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    • 专利摘要:
    The present invention relates to a method and a system for microwave heating comprising: modal transition means that transform a linear input polarization into a first circular polarization; and a quasi-isolator device, passive, reciprocal, with three electric doors and attachable to a microwave transmission chain, which is configured to reflect a second circular polarization orthogonal to the first, which occurs when said first circular polarization is reflected in the load to be heated; thus, in a process of heating the load, of reflection coefficient ρ, the reflection coefficient at the input of the quasi-insulating device is less than ρ and the power delivered to the load is maximized. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2734379A1
    申请号:ES201930549
    申请日:2019-06-17
    公开日:2019-12-05
    发明作者:Machain Rebollar (Upm) Jesús María；Garai José Ramón Montejo；Cruz Jorge Alfonso Ruiz
    申请人:Universidad Politecnica de Madrid；Universidad Autonoma de Madrid；
    IPC主号:
    专利说明:

    [0001] SYSTEM AND METHOD TO IMPROVE THE ENERGY PERFORMANCE OF A
    [0002]
    [0003] OBJECT OF THE INVENTION
    [0004]
    [0005] The present invention relates to the technical field of microwave waves and more specifically to the use of microwave waves in heating processes of industrial systems or microwave ovens, with improved energy efficiency.
    [0006]
    [0007] BACKGROUND OF THE INVENTION
    [0008] The electromagnetic signals of frequencies in the range between 0.1 and 100 Gigahertz (GHz), are commonly used for the transmission and reception of information signals, using what is known as microwave systems. In addition to this use in communications, the energy exchange between electromagnetic fields and energy dissipation in the form of heat, which is commonly used in numerous industrial heating systems and also in domestic furnaces, is well known.
    [0009]
    [0010] A characteristic that completely marks the operation of these systems is the operating frequency band, corresponding to the so-called ISM bands (Industrial, Scientific and Medical). For example, for household microwave ovens, this frequency is 2.45 GHz. But there is another fundamental property of electromagnetic fields that is polarization. This is used routinely in communications systems where the different polarizations used are: vertical, horizontal, circular right (C +) and circular left (C-). In these systems, a figure of merit is used, which is the discrimination of orthogonal polarizations (vertical versus horizontal and circular right to circular left) to measure its purity. Very high discrimination values (high polarization purity) are necessary to separate the different polarizations and ensure proper functioning of these systems.
    [0011]
    [0012] In microwave heating systems, the polarization property remains in the background, since the objective is not to transport information, but to convert the electromagnetic field generated through a feeder system, connected on the one hand to a microwave signal generator, and on the other hand to a load (the object to be heated), in heat dissipation in the load.
    [0013]
    [0014] In the usual operation of a microwave electromagnetic wave oven for heating materials, the charges are very different and with electromagnetic properties (type of material, shape, etc.) very diverse. This causes that the waves that are reflected at the entrance of the feeder system can present great variations, with a very significant associated power. However, for the correct functioning of the system (to extend its useful life, and to increase its energy efficiency) it is of interest that the feeder system be able to deliver all the power of the generator regardless of the material to be heated (that is, using the microwave circuit engineering terminology, regardless of the load to which it is connected to the heating system), or at least that the generator is not affected by the reflection of the feeder system and the load. This situation is the most realistic, since completely canceling that reflection is a technical unlikely scenario due to the multitude of materials, with their respective shapes, which can be subject to heating.
    [0015]
    [0016] There are several solutions to try to alleviate this effect related to the reflected signal (characterized from the technical point of view with the reflection coefficient) by the material to be heated. Most of them are based on the use of microwave devices or circuits known as insulators, circulators and rotators (all three are non-reciprocal devices) and, the respective combinations of these devices by additional microwave frequency circuitry as hybrid couplers (elements reciprocal and non-dissipative) and adapted reference loads (dissipative elements by definition). In general, the more you want to separate the feeder system from the load, the more expensive it is economically. More important if it is possible that, even in the event that the generator of the load is independent, the energy expenditure is still considerable, as part of the power of the generator reaches the dissipative elements, which can become very significant , and that has not been delivered to the load to be heated.
    [0017]
    [0018] A first solution that is usually adopted so that the generator is not affected is to place an insulator at the generator outlet. The insulator is, from the electromagnetic point of view, a non-reciprocal device made with ferrites, and economically expensive The power reflected by the load does not reach the generator, when it is absorbed by the insulator (which is a dissipative element, that is to say, in its interior that energy reflected by the material to be heated is dissipated, producing a waste of energy ). This situation is depicted in detail in Figure 1, which shows the scheme of the transmission chain of the microwave signal for heating formed by a microwave generator 100 and a microwave antenna (the applicator of the electromagnetic field excited on the generator 100 to the material to be heated) 120. Between them, to protect the generator 100 is an insulator 102, which allows the signal 101 of the generator to pass to the antenna. The signal 103 that reaches the antenna, one part is dissipated in the load 104, but another part 105 is reflected towards the generator. The parameter that quantifies the ratio of the reflected signal 105 on the incident signal 103 is the reflection coefficient pB 106 and is determined by the characteristics (electromagnetic properties, shape, temperature, etc.) of the material to be heated. The insulator 102 in this case protects the generator, absorbing the reflected signal 105 by dissipation, and preventing it from reaching the generator. However, this signal 105 has dissipated on the insulator, instead of on the material to be heated, decreasing the energy efficiency.
    [0019]
    [0020] Another possibility based on non-reciprocal elements is that of using circulators with a dissipative element (resistive loads adapted) incorporated on purpose in the design to dissipate the power that cannot be delivered to the load to be heated and is reflected by it towards the generator. This situation is represented in detail in Figure 2, where another scheme of the transmission chain of the microwave signal for heating is shown, with the microwave generator 100 and the microwave antenna (the field applicator to the material to be heated) 120. Between them, to protect the generator 100 is a circulator 108 (three-door circuit), which allows the signal 101 of the generator to pass to the antenna. The signal 103 that reaches the antenna, a part 104 is dissipated in the load to be heated, but another part 105 is reflected towards the generator due to the reflection coefficient pB 106. The dissipative load 107 located in the door 3 of the circulator 108 absorbs the reflected signal 105, preventing it from reaching the generator. As in the case of Figure 1, part of the energy of the generator 101 has dissipated in an element (in this case the load 107) and not in the material to be heated, thus decreasing the energy efficiency.
    [0021] Other alternatives that can be adopted are circuitally more complicated solutions such as those based on the use of a spinner (non-reciprocal) plus two 3 dB hybrid couplers (passive and reciprocal devices) with two dissipative elements (adapted loads) incorporated in the design on purpose to dissipate the power that is reflected to the load to be heated. Again the energy wastage of all the power reflected by the antenna towards the generator. This situation is represented in detail in Figure 3 , where another scheme of the microwave transmission chain for heating is shown in which part of the energy of the microwave generator 100 is also wasted. Between the generator and the microwave antenna (the applicator of the field to the material to be heated) 120 two circuits known as hybrid couplers 202 , 204 of 3 dB division, and a spinner 203 are inserted (circuit that changes the phase of the transmitted wave in one direction with respect to the transmitted wave in the opposite direction). The signal from the generator 101 crosses these components and becomes the signal 103 that drives the field 120 applicator . One part 104 is inverted in the heating of the material, but another part 105 is reflected due to the reflection coefficient pB 106 and dissipates in dissipative charges 107.
    [0022]
    [0023] Therefore, a solution that improves the protection of the microwave generator against variability in the conditions of reflection of eventual loads, without penalizing energy efficiency, is lacking in the state of the art, since known solutions pass through complex based systems in power dissipating elements, not reciprocals with improved energy efficiency.
    [0024]
    [0025] DESCRIPTION OF THE INVENTION
    [0026] In order to achieve the objectives and avoid the aforementioned drawbacks, the present invention describes, in a first aspect, a microwave heating system comprising:
    [0027] - modal transition means configured to transform an input linear polarization into a first circular polarization; Y
    [0028] - a quasi-insulating device, passive, reciprocal, with three electric doors and attachable to a microwave transmission chain, where the quasi-insulating device is configured to reflect a second circular polarization orthogonal to the first, where the second circular polarization is produces when the first circular polarization of the transition means is reflected in a load to be heated;
    [0029] where, in a process of heating the load, of reflection coefficient p, with the circular polarization of output, the reflection coefficient at the input of the quasi-insulating device is less than p. Thus, advantageously, the power delivered to the load to be heated is maximized by using the two orthogonal circular polarizations, where a circular polarization in one direction of rotation occurs when the orthogonal circular polarization in the other direction is reflected in the load.
    [0030]
    [0031] In one of the embodiments of the present invention, where an ideal operation of the quasi-isolator device is contemplated, its behavior is defined by a matrix S of dispersion parameters with a coefficient S11 = 0 and coefficients S12 and S13 that meet that the sum of its squares is equal to 0. In other embodiments of the invention, the design of the quasi-isolating device with approximate coefficients defined for an ideal behavior is contemplated.
    [0032]
    [0033] Thus, when the system of the present invention is coupled in a microwave transmission chain and a process of heating a load having an associated reflection coefficient of pB is initiated, the reflection coefficient at the input of the quasi-insulator device results approximately from p2B. Therefore, advantageously, for loads such as those used in heating that meet 0 <| pB | <1, the reflection coefficient p2B at the input of the quasi-insulating device is smaller than that which would have the direct connection of the generator with the load of bp. This is achieved in the present invention by applying polarization concepts, away from the technical field of heating, to improve efficiency and performance in the heating process by surprisingly reducing the signal reflected by the load towards the microwave generator.
    [0034]
    [0035] According to one of the embodiments of the present invention, the modal transition means comprises: means for transforming the linear input polarization into two orthogonal linear polarizations; and offset means, configured to offset the two orthogonal linear polarizations 90 °.
    [0036] Additionally, in one of the embodiments of the present invention it is contemplated: an input waveguide connected by one of its ends to an electrical input gate of the quasi-insulator device, where the input waveguide is connectable by another of its ends to a microwave generator; and an output waveguide, connected at one of its ends to the electrical output doors of the quasi-isolator device, where the output waveguide is connectable at another of its ends to a microwave antenna.
    [0037]
    [0038] In one of the embodiments of the present invention, the system comprises a horn-type microwave antenna, connected to the output waveguide and configured to, when excited by microwaves with circular output polarization, apply an electromagnetic field on the load characterized by a reflection coefficient p.
    [0039]
    [0040] Optionally, in one of the embodiments of the invention an adapter module is arranged between the exit doors of the quasi-isolator device and the input of the horn-type microwave antenna. Thus, advantageously, the circular polarization that leaves the phase shifter can be adapted to the signal that will excite the electromagnetic field applicator with the load to be heated.
    [0041]
    [0042] In case of incorporating waveguides and input to the system of the present invention, according to a particular embodiment, they are chosen with double symmetry and the output waveguide is a circular waveguide comprising a single physical output gate for the two electrical exit doors of the quasi-isolator device, each of them for each of the two modes TE11 of the circular waveguide.
    [0043]
    [0044] Alternatively to the embodiments with waveguide technology described, in a particular embodiment of the present invention implemented with planar technology, the modal transition means are arranged on a dielectric substrate and comprise: phase shifter means configured to offset a polarized input signal linearly; and a patch antenna with two orthogonal inputs connected to the electrical output doors of the quasi-isolating device, configured to radiate a circular polarization electromagnetic field.
    [0045] Additionally, one of the embodiments comprises an input polarizer connected to an electrical input gate of the quasi-isolator device, configured to transform a circular input polarization into a linear output polarization. Thus, advantageously, the system of the present invention can be adapted to scenarios in which the input is circularly polarized, without changing its configuration and operation rather than adding said input polarizer.
    [0046]
    [0047] In one of the embodiments of the invention, the modal transition means are part of the quasi-isolator device.
    [0048]
    [0049] A second aspect of the invention relates to a method for microwave heating comprising the steps of: providing a linearly polarized microwave signal at an input of a quasi-insulating, passive, reciprocal device, with three electric doors and attachable to a microwave transmission chain; transform, in modal transitional means, the linearly polarized microwave signal into a first circularly polarized microwave signal; apply, by a microwave antenna, the first circularly polarized microwave signal to a load of reflection coefficient p, so that a part of the circularly polarized microwave signal is reflected in the load and a second circularly orthogonal polarized signal is produced at first; and reflect, in the quasi-insulator device, the second signal circularly polarized and orthogonal to the first, so that a reflection coefficient at the input of the quasi-insulator device is less than p. Advantageously, the power delivered to the load to be heated is thus maximized by using the two orthogonal circular polarizations, where a circular polarization in one direction of rotation occurs when the orthogonal circular polarization in the other direction is reflected in the load.
    [0050]
    [0051] In one of the embodiments of the invention, where an ideal operation is contemplated, the method further comprises defining the quasi-insulator device by means of a matrix S of dispersion parameters, establishing the following conditions: a coefficient S11 = 0 and coefficients S12 and S13 that fulfill that the sum of their squares is equal to 0.
    [0052]
    [0053] In one of the embodiments of the invention, transform the linearly polarized microwave signal into the first circularly polarized microwave signal. it comprises: transforming the linear input polarization into two linear orthogonal polarizations; and offset the two orthogonal linear polarizations 90 °.
    [0054]
    [0055] Additionally, one of the embodiments of the present invention comprises: generating the microwave signal in a microwave generator; guide, by an input waveguide, the microwave signal to the quasi-isolator device; and guide, by an output waveguide, the circularly polarized microwave signal to a microwave antenna, configured to apply it to the load. More specifically, a particular embodiment further comprises determining a working frequency and selecting a geometry for the input waveguide and the output waveguide, based on said frequency.
    [0056]
    [0057] In one of the embodiments of the invention, it is also contemplated to transform, by an input polarizer connected between the input of the quasi-isolator device and a microwave generator with circular polarization, a circularly polarized signal in the linearly polarized microwave signal that is provides at the entrance of the quasi-insulator device.
    [0058]
    [0059] Transforming the linearly polarized microwave signal into a circularly polarized microwave signal comprises, according to one of the embodiments of the invention, the steps of: 90 ° offsetting the linearly polarized microwave signal provided at the input of the quasi-isolating device; and providing the two 90 ° offset signals at two inputs arranged orthogonally on a planar antenna, typically a microstrip patch, where this planar type antenna is configured to radiate the circularly polarized microwave signal that is applied to the load.
    [0060]
    [0061] For all the foregoing, the present invention has a multitude of advantages that, despite being mainly focused on the efficiency and performance of the heating system, also report other benefits such as the durability of the system and its lower cost and / or complexity from a electromagnetic point of view.
    [0062]
    [0063] The system and method of the present invention is applicable to classic microwave heating systems, such as those shown in Figures 1,2 and 3, just before the antenna (or electromagnetic field applicator), advantageously causing that said systems operate in much more favorable conditions by handling a much lower reflected power towards the generator, by reducing the reflection coefficient at the input of the quasi-insulator device to approximate values of p2B, compared to the value of pB that it is had without the present invention.
    [0064]
    [0065] In one of the embodiments of the invention, for a common situation of loads with modulus of the reflection coefficient between 0.6 and 0.98 (4.4 dB and 0.2 dB), the improvement of the heating system performance by adding the present invention with respect to the system without The present invention varies between 36% and 96%, according to Figure 7A-7B, and in particular to the results shown in the table of Figure 7C.
    [0066]
    [0067] From a functional point of view, the system of the present invention has a behavior very similar to that of the microwave circuit known as an insulator, since it allows the generator to be isolated from the load by converting the reflection coefficient of pB at the output into a Approximate value of p2B at the entrance. Obviously, isolation is not absolute, so it is considered more appropriate to define it as quasi-insulator.
    [0068]
    [0069] Another advantage of the present invention is that, unlike the known insulating circuits, the quasi-insulating device of the present invention is composed of only reciprocal components, that is, it is only composed of materials whose electromagnetic properties give rise to circuits that They fulfill the property known as reciprocity.
    [0070]
    [0071] Additionally, the quasi-isolating device of the present invention, from a point of view of its circuit definition, is a lossless microwave circuit, since it does not include dissipative elements inside it such as circulator-based or rotator-based schemes with hybrid couplers , which incorporate charges where the energy reflected by the charge dissipates.
    [0072]
    [0073] BRIEF DESCRIPTION OF THE FIGURES
    [0074] Next, a series of drawings that help to better understand the invention and that expressly relate to an embodiment of said invention that is presented as a non-limiting example thereof are briefly described.
    [0075] Figure 1 shows the operation of a heating system, consisting of a microwave generator, a microwave antenna (the applicator of the electromagnetic field from the generator to the material to be heated), using the solution to protect the generator based on the circuit of microwave known as an insulator positioned between the generator and the antenna.
    [0076]
    [0077] Figure 2 shows the operation of a heating system, consisting of a microwave generator, a microwave antenna (the applicator of the field to the material to be heated), using the solution to protect the generator based on the three microwave door circuit known as a circulator, positioned between the generator and the antenna, with one of its doors connected to a dissipative load.
    [0078]
    [0079] Figure 3 shows the operation of a heating system, consisting of a microwave generator, a microwave antenna (the field applicator to the material to be heated), using the solution to protect the generator based on a spinner plus two hybrid couplers with Two dissipative charges.
    [0080]
    [0081] Figures 4A, 4B and 4C show the operation of a transmission medium (a guide or guidance system) of chiral characteristics, when excited with a microwave signal with circular polarization, giving rise to reflected signals with different characteristics, and allowing reduce the reflection coefficient at the entrance of the chiral medium.
    [0082]
    [0083] Figure 5A shows the operation of a heating system, consisting of a microwave generator, a microwave antenna (the field applicator to the material to be heated), using the solution object of the present invention (the "quasi-insulating device " the "Quasi-Isolator-Reciprocal-Lossless" or "QARSP") positioned between the generator and the antenna.
    [0084]
    [0085] Figures 5B and 5C show simple embodiments of the device of the present invention in waveguide technology and in planar technology respectively.
    [0086]
    [0087] Figures 6A and 6B represent other uses of the Quasi-Isolator-Reciprocal-Lossless (QARSP) object of the present invention in heating systems. In one case a heating system is presented that protects the generator so simpler and with greater energy savings than conventional systems. In another case, a system with two generators of two different frequencies is presented, where the present invention also protects the generator more easily and with greater energy savings than conventional systems.
    [0088]
    [0089] Figure 7A represents the case of direct connection between the heating system generator and the antenna (the field applicator to the material to be heated). In Figure 7B the new device object of the present invention is positioned between the generator and the antenna. Figure 7C is a summary table of the benefits of the new device comparing the benefits of the case of Figure 7A, with the case of Figure 7B. The graphs of these parameters considered in the tables are represented in Figures 7D, 7E and 7F , which represent the summary of the performance of the new device.
    [0090]
    [0091] Figure 8 shows a preferred embodiment of the new device, based on a block diagram with well defined functionalities.
    [0092]
    [0093] Figures 9A, 9B, 9C and 9D represent the experimental validation of one of the possible implementations of the new quasi isolator device or QARSP, showing how to perform each of the blocks, and comparing the theoretical results with the experimental ones of an experimental prototype measured with different test loads representing different types of materials to be heated.
    [0094]
    [0095] DETAILED DESCRIPTION OF THE INVENTION
    [0096] The system and method of the present invention, to improve the energy efficiency in microwave heating processes, apply polarization concepts far from the technical field of heating which, surprisingly, result in the reduction of the reflected signal towards the microwave generator for the material to be heated.
    [0097]
    [0098] Then, for clarification purposes only, chiral transmission media schemes representing a similar operation to that of the present invention are introduced. The chiral means only allow the passage of certain waves, selectively discriminating the positive or negative circular polarization. So, This operation will serve as a conceptual basis for understanding the operation of the present invention.
    [0099]
    [0100] Figures 4A, 4B and 4C summarize these concepts, although always in a different area from the microwave heating of the present invention, showing how to convert a reflection coefficient pB in the load into a reflection coefficient p2B in the input. The consequence, since the modulus of the reflection coefficient is a number smaller than 1, is that when it is squared it is smaller, so that the reflected power is reduced. Figures 4A and 4B show basic operation (no load), and Figure 4C shows operation with a load.
    [0101]
    [0102] The chiral guides have the property that they let a field with circular polarization C + pass and do not allow the passage of the circular polarization C- (or vice versa). Accordingly, Figure 4A shows the incidence on the left to the chiral guide 210 of a wave 211 of amplitude a01 with circular polarization C +. This signal is transmitted to output 213 with an amplitude ideally b03 = a01 with circular polarization C + equal to the polarization of the incident wave. If a wave 212 with an amplitude a02 with circular polarization C- falls on the input, it is fully reflected due to the properties of the chiral guide.
    [0103]
    [0104] Figure 4B shows the incidence to the chiral guide 210 on the right of a wave 223 of amplitude a03 with circular polarization C +. This signal is transmitted to output 221 with an amplitude ideally b01 = a03 with circular polarization C + equal to that of the incident wave. If a wave 224 with an amplitude a04 with circular polarization C- falls on the right chiral medium, this wave is ideally fully reflected, again due to the properties of the chiral guide.
    [0105]
    [0106] In Figure 4C , the chiral guide 210 is loaded with an element (such as a material to be heated) characterized by its reflection coefficient pB 240. The system is fed with a signal 231 with circular polarization C +. After the successive transmissions and reflections 232 , 233 , 234 , 235 , the signal reflected at input 236 has an amplitude of p2B with respect to the amplitude of the incident wave 231 (and with the same C + polarization). The reflection coefficient at the input has therefore become p2B.
    [0107] Therefore, despite the fact that the chiral guides require circularly polarized signals at the input, that they are not precisely conventional elements and that they are not characterized by their application in environments with high power levels, the schemes in Figures 4A- 4C have a direct relationship with the operation of the present invention, in that they allow reflection to be reduced without dissipative elements. Once these concepts have been introduced, the isolating device of the present invention will be described below, which will also be referred to herein as a QARSP (acronym for Quasi-Isolator-Reciprocal-Lossless).
    [0108]
    [0109] A block diagram of an embodiment of the invention is shown in Figure 5A , where a heating system with a microwave generator 100 , an antenna 120 (the applicator of the electromagnetic field from the generator), and the QARSP 300 device is contemplated to improve the performance of the present invention located between the microwave generator and the antenna. The QARSP 300 device, reciprocal and lossless (that is, without dissipative elements inside it), and without using chiral guides, allows a greater part of the available power of the generator 101 to be converted into power delivered 104 to the load to be heated . Therefore, the QARSP device allows most of the generator power to be dedicated to the heating of the load whatever the load, characterized by its reflection coefficient pB 106. When the generator signal 101 strikes the new device 300 , most of it is transmitted 103 towards the load, and only a small power signal 308 from the signal reflected 105 by the load with a reflection coefficient pB is reflected towards the generator. This reflected signal 308 carries a small fraction of the power of the generator, specifically, the device of the present invention allows the reflection coefficient 307 at the generator input to be reduced approximately to p2B.
    [0110]
    [0111] Figure 5B depicts a simple embodiment in waveguide technology of device 300 , where it is schematically arranged between two physical gates, which are a rectangular waveguide input that implements an electrical input gate 61 and a guidewire output. circular wave that implements the two electrical exit doors 62 and 63 . Its operation can be summarized in the steps of: receiving an input signal (linear polarization in this case) that excites the device and produces circular polarization of reference C + at its output. Next, the output reflection caused by the object to be heated causes the return signal of amplitude proportional to pB and circular polarization C- to be affected by the output door of the QARSP device. Of this signal that reaches the QARSP device through its exit door, a part is reflected again in the exit door towards the object to be heated, thus contributing to the heating; and another part is transmitted to the input of the QARSP device as a reflection (in linear polarization) towards the generator connected to the input door of the QARSP device. As a result of this whole process, the total net reflection presented by the QARSP at the entrance is of proportional amplitude to p2B.
    [0112]
    [0113] Figure 5C represents the same QARSP device of the present invention, but implemented with planar technology instead of waveguide. In this case, the three electric gates 61, 62, and 63, which are a characteristic common to all embodiments, are implemented in three physical gates, where the two exit gates provide two linearly polarized signals, offset 90 ° to each other, which they are connected directly to two orthogonal inputs 73, 74 of a patch-type antenna 71, comprised in the same dielectric substrate 72 as the QARSP device, to emit circular polarization. Its operation is substantially the same as in the previous embodiment in waveguide, since its behavior is defined by the dispersion matrix, as will be explained in detail below.
    [0114]
    [0115] All of the above results in an improvement in the energy efficiency of the heating process, which can be demonstrated numerically by analyzing the design of the QARSP device according to its dispersion parameters, also known as S parameters, which obviate the electromagnetic analysis and model its behavior as a transmission line
    [0116]
    [0117] Assuming a description of the device 300 of the present invention by means of its matrix S or dispersion matrix, which is a customary procedure in microwave engineering, the quasi-isolating device 300 of the present invention is then defined as a passive, reciprocal and Lossless with three electric doors. Thus, when the quasi-isolator device or QARSP is used in a heating process and finds a load with a reflection coefficient at the output pB, the amplitude of the signal reflected in the input with respect to the transmitted one (that is, the reflection coefficient at input / w) can be written as follows based on the parameters S of its dispersion matrix:
    [0118]
    [0119]
    [0120]
    [0121]
    [0122] Since the QARSP device has been defined as reciprocal, its dispersion matrix S is symmetric: [S] = [S] T, that is, the elements of the matrix fulfill that: Sij = S¡¡. i, j = 1, ..., 3.
    [0123]
    [0124] Furthermore, it is imposed in the present invention that the S parameters of the QARSP device comply with:
    [0125]
    [0126]
    [0127] that is, the device is adapted at the entrance door. This property (like the previous one of reciprocity) is very common in microwave engineering.
    [0128]
    [0129] On the other hand, another much more specific condition is imposed for the quasi-isolating device of the present invention, and the dispersion parameters also meet that:
    [0130]
    [0131]
    [0132]
    [0133] This condition of adjustment of transmissions in module and phase is fundamental to satisfy the objective of the present invention to improve the energy efficiency in a heating process.
    [0134]
    [0135] According to the above, the reflection coefficient at the entrance is as:
    [0136]
    [0137]
    [0138]
    [0139]
    [0140] that for | pB | <1 (usual passive loads), it can be approximated by / w = p2B. Therefore, the reflection at the input pent is proportional to p2B; and taking into account that | pB | <1, it is finally assumed that the signal reflected at the input is much lower than the reflection at the output, which demonstrates the improvement in energy efficiency that advantageously and surprisingly provides the design of the method and device of the present invention.
    [0141] In addition, the design and manufacture of the QARSP device is very simple and does not require any material other than that used for the realization of the antenna, preferably a metal such as aluminum, copper or brass: the QARSP is reciprocal and lossless and does not contain materials such as ferrites or dissipative elements.
    [0142]
    [0143] On the other hand, the method and system of the present invention is applicable to both domestic and high-power industrial environments, so the final design of the QARSP device will only depend on the expected working conditions, which will lead to any expert in the matter to choose the most appropriate design options to adapt for example to a certain working frequency, select a type of waveguide technology or planar technology, select the geometry of the waveguides, select a microwave antenna horn type or select a patch type antenna.
    [0144]
    [0145] Figure 8 shows one of the embodiments of the QARSP 300 device of the present invention by means of functional blocks already known separately in the field of microwave circuits, but designed together to achieve the functionality of the quasi-insulator device object of the present invention , using reciprocal and lossless circuits. This topology, once the indicated components have been designed, converts the reflection coefficient pB 106 into a reflection coefficient at input 309 of approximately p2B. When the signal 101 of the linear polarization generator strikes the quasi-insulator device 300 of the present invention, most of it is transmitted to the load 104 . Only a small power signal 308 from the signal reflected by the load with a reflection coefficient pB 106 is reflected towards the generator. This reflected signal 308 carries a small fraction of the power of the generator, specifically, the device 300 of the The present invention allows the reflection coefficient at the input 309 of the generator to be reduced to p2B. Most of the power 104 will have dissipated in the load using a field with circular polarization.
    [0146]
    [0147] This embodiment comprises the following functional blocks:
    [0148] - a modal transition 350 that is excited by the signal 101 from the generator (directly as in Figure 5A, or after passing through additional elements). This block 350 generates two orthogonal linear polarizations at its output.
    [0149] - a phase shifter 351 of the two linear polarizations orthogonal to the input that offset these two polarizations 90 °, resulting in a circular polarization.
    [0150] - An adapter module 352 of the circular polarization leaving the phase shifter to adapt the signal that will excite the electromagnetic field applicator with the load to be heated.
    [0151]
    [0152] Figures 6A and 6B show a block diagram of the device object of the present invention in two different situations.
    [0153]
    [0154] An engineering situation is shown in Figure 6A in which it is required that there is no reflected power to the generator 100. Therefore, an additional insulator 102 has been added. In this case, the use of the quasi-insulator device of the present invention (also referred to as Quasi-Isolator-Reciprocal-Lossless or QARSP) 300 makes it possible to handle an insulator 102 much simpler, less expensive and with a longer service life than the one it would be necessary without the device of the present invention, since the power of the reflected signal 308 that it has to absorb is much less. All this is achieved in addition to the increase in energy efficiency already described, since most of the power delivered by the generator has dissipated in the load to be heated (the quantification of this behavior will be seen in Figures 7C-7F) . That is, the QARSP device of the present invention is applicable in traditional architectures, such as those in Figures 1, 2 and 3, placing it just before the antenna (or electromagnetic field applicator) 120, where a reflection coefficient pB is seen 106.
    [0155]
    [0156] A heating application using two different frequency sources (f1 and f2, respectively) provided by two generators 401, 402 is shown in Figure 6B. The antenna (the electromagnetic field applicator) 420 operates at these two frequencies, and at Putting the load to be heated has a reflection coefficient pB 412 at these two frequencies, which causes part of the incident signal 407 to become a reflected signal 408 towards the generator. For this application the QARSP 370 device can be adapted / modified to work on two frequencies. The new QARSP 370 device maintains good insulation between generators In this case, between the generator and the QARSP, a diplexer must be introduced that adds the signal of the two generators f1 and f2 to the input of the QARSP. What is presented in Figure 6B is that the QARSP device can work simultaneously with two frequencies f1 and f2, as well as the aforementioned reflection characteristics are maintained, allowing the signals reflected towards the generator 404, 406 to have an amplitude p2B regarding the signals incident to the QARSP 403, 405.
    [0157]
    [0158] Figures 7A, 7B, 7C, 7D, 7E, 7F summarize the operation of the device object of the present invention from a quantitative point of view, comparing a starting situation of direct connection between the microwave generator and the antenna (Figure 7A), with the situation in which the QARSP device of the present invention is positioned between them (Figure 7B).
    [0159]
    [0160] In Figure 7A, the generator 100 has an available power 101 of P-gen ("gen" indicates generator.) Due to the load to be heated, the antenna input (the field applicator) 120 has a coefficient of reflection pB 106. The power 104 that is delivered and dissipated in the heat load is P-load-SD ("SD" indicates "no device", that is, without using the new device object of the present invention) The power 105 that is reflected towards the generator in this situation is P-ref-SD ("ref" indicates reflected).
    [0161]
    [0162] In Figure 7B, generator 100 has an available power 101 (P-gen). Due to the load to be heated, at the antenna input (the field applicator) 120 there is a reflection coefficient pB 106. The power 204 that is delivered and dissipated in the load in the form of heat is power in the load with device (P-load-CD), that is, in this situation you have the device 300 Quasi-Isolator-Reciprocal-Lossless or QARSP between the generator 300 and the antenna 120. The power 205 that is reflected towards the generator in This situation is called reflected power with device (P-ref-CD).
    [0163]
    [0164] A comparative table of the situation of the two cases is shown in Figure 7C: that of Figure 7A and that of Figure 7B. The power of the P-gen generator in both the case of Figure 7A and that of Figure 7B is maintained without loss at 1 W (first column), and the reflection coefficient modulus | pB | in the same way in two cases (that is, the same load to be heated is located in both cases, and for each row, what happens with different loads is evaluated). The power delivered to the load in both cases, load power without device (P-load-SD) and load power with device (P-load-CD), is quantified in the third column (subdivided into two) in percentage form with respect to the first column. The lost power that is reflected towards the generator in both cases, reflected power without device (P-ref-SD) and reflected power with device (P-ref-CD), is quantified in the fourth column (subdivided into two) in percentage form with respect to the first column. The performance in percentage form for each case is detailed in the fifth column, which indicates the power delivered to the load with respect to the generator available. The last, (sixth column) indicates the ratio between the system performance with the device ("CD"), with respect to the system without device ("SD"), that is, the improvement in performance (if it is a number greater than 1 ) when using the QARSP device of the present invention, with respect to not using it. In this figure, the area 400 is highlighted, where the performance improvement, just when the load causes more reflection of the generator, is more noticeable, approaching double for loads with a very high reflection. It is in this situation where the improvement introduced by the present invention is more remarkable, since it is the most adverse situation for the generator, being able to deliver almost double more power when using the QARSP device than without using it, which entails energy savings and increased life of the entire system.
    [0165]
    [0166] The power and performance curve related to the situations of Figures 7A and 7B are illustrated in Figures 7D and 7E . On the horizontal axis, the scale of modules of the reflection coefficient of the load is represented, while on the vertical axis a power scale (as a percentage of the generator power) is shown in Figure 7D, and a scale of yield (in percentage) in Figure 7E. The two curves of Figure 7D correspond to the power reflected towards the generator with device (curve 510 ) and without device (curve 520 ), respectively, and the power delivered to the load P-load-CD, P-load-SD, In both situations. It is observed how for any load, the power delivered using the QARSP device of the present invention is always greater than or equal to that of the system that does not use said device. In extreme cases where there is no reflection, that is | pB | = 0, or there is total reflection, that is, | pB | = 1, the device would not provide any advantage, but in reality these two cases do not occur in practice, as usual in a system of heating is to have the situation 0 <| pB | <1. Similarly, the power reflected towards the generator is always lower (except in the extreme cases already mentioned, where it would be the same) in the system using the QARSP device.
    [0167]
    [0168] This advantage is shown more clearly in Figures 7E and 7F . Figure 7E shows the two performance curves (power delivered to the load with respect to the available power of the generator) in percent for the system without QARSP device (curve 610 ) and with QARSP device (curve 620 ). These curves reflect the great importance that the QARSP provides from an energy point of view: when the reflection coefficient is small, the yield is close to the maximum (100%) in both situations. When the reflection coefficient increases and the performance of the system without a device decreases, the QARSP device causes the performance ratio to increase continuously until it doubles. That is, the more energy is lost in the system without a device (worse performance), the more effective is the use of the QARSP method and device of the present invention.
    [0169]
    [0170] Figure 7F shows the improvement in percentage yield (curve 710 ). In both Figure 7D and 7E and 7F, the zone 500 , 600 , 700 in which the improvement produced by the QARSP device is most noticeable is where the coefficient of reflection of the load is highest, which results in the best energy use introduced by the present invention, which can almost reach a 100% performance improvement, when the load has a very high reflection coefficient.
    [0171]
    [0172] A particular embodiment of the invention that illustrates the main features and versatility of the present invention is described below. Figures 9A, 9B, 9C and 9D show the experimental validation of a practical implementation of the QARSP device of the present invention. This validation has been done in the X band from 11.9 to 12.1 GHz for simplicity of the measurement tooling, but the design and operation principle is exactly the same in other frequency bands used in heating processes.
    [0173]
    [0174] Figure 9A shows the computer-aided design representation (CAD figure) of the QARSP device, where the modal transition 350 , the phase shifter 351 and the adapter module 352 are identified between the quasi-insulator exit door and the door of horn antenna input. These components are connected to the rest of the heating system by the circular waveguide 504 to the antenna (the applicator of the electromagnetic field to the object to be heated), and by the rectangular waveguide 501 to the part of the system that links to the generator of microwave. All waveguides and the different sections that make up the device are metallic, and in this case aluminum and filled with air, thus complying that the device is reciprocal and lossless (in other cases they could be designed with other shapes and with others dielectric materials, but always fulfilling this condition). Its quasi-isolator behavior is verified later in the description of Figures 9D and 9E.
    [0175]
    [0176] Figure 9B shows another view of Fig. 9A where the circular exit guide and its flange 504 are observed for connection with the field applicator, which in this case is an X-band conical horn antenna with input into circular guide of the same size as the circular output guide 504 of the QARSP.
    [0177]
    [0178] A measurement scheme with the elements for the experimental characterization of the present invention is shown in Figure 9C . This figure shows the rectangular input guide 501 of the quasi-isolator device, or QARSP, where for experimental validation it is connected to the generator of a network analyzer 520 by a transition 502 between the rectangular guide and the coaxial cable 522 that gives access to network analyzer 520 . At the exit of the horn an absorbent panel 602 is placed, in order to be able to characterize the reflected signal at the input of the QARSP device and therefore measure the reflection coefficient at the input pDp 309. This coefficient is ideally p2B, with pB 106 being the coefficient of reflection with which the QARSP is loaded, which in this case is the reflection coefficient seen in the circular output guide 504 of the QARSP produced by the transition 506 generating said reflection.
    [0179]
    [0180] With this experimental characterization system, four cases (four transitions 506) of study 910 , 920 , 930 , 940 have been raised, each corresponding to a different reflection coefficient pB in the circular exit guide 504 of the quasi-isolating device or QARSP. For each case, the pB was first measured without a QARSP device (which would be the situation in Figure 7A), and then with the QARSP device (situation in Figure 7B), whose practical validation is performed with the system shown in Figure 9C.
    [0181] Figure 9D shows the experimental results obtained from the different reflection coefficients measured in decibels with respect to the frequency for each of the four cases. In each of the four graphs 910, 920, 930, 940 (one graph per case), there are three curves. Two are measured: a first curve 911, 921, 931, 941 represents the reflection coefficient pB associated with the load and a second curve 912, 922, 932, 942 the coefficient pDP at the input of the QARSP. This last coefficient, for an ideal QARSP should be p2B, and therefore a third curve 913, 923, 933, 943 has been introduced for each graph that is directly the value of p2B for each frequency, in order to compare with the measured one. It is observed in the graphs that the theoretical ( 913, 923, 933, 943 ) and experimental results ( 912, 922, 932, 942) are very similar. Therefore, according to the results it is validated that the device shown in Figure 9B behaves very roughly like a QARSP device. Small discrepancies, which even improve the expected results at some frequencies, are typical of any microwave experiment of limited cost.
    [0182]
    [0183] As a summary table, the specific results of each of the curves for the 12GHz frequency are shown below.
    [0184]
    [0185]
    [0186] Therefore, it is demonstrated that this experimental prototype is an adequate implementation of the QARSP device in X-band, and therefore gives rise to the advantages already mentioned in its application to a heating system.
    [0187]
    [0188] The example shown is based on one of the possible embodiments of the QARSP, but it is only one of the many possibilities that can be conveniently designed to obtain a circuit with the characteristics of Quasi-Isolator-Reciprocal-Lossless as described in the present invention, to exploit its advantages in heating systems. Thus, for example, other structures can be proposed in planar technology, both strip and microstrip, based on the use of circuits and antennas both in this technology, as in the patch or slot type antennas.
    [0189]
    [0190] These and other embodiments, although based on technologies other than those shown in depth in the previous examples of Figures 8 and 9, could be implemented to fulfill the same functions described for the QARSP method and device of the present invention with simple variations and modifications Obvious to those skilled in the art.
    权利要求:
    Claims (17)
    [1]
    1. Microwave heating system comprising:
    - modal transition means configured to transform an input linear polarization into a first circular polarization; Y
    - a quasi-insulator device (300), passive, reciprocal, with three electric doors (61, 62, 63) and attachable to a microwave transmission chain, where the quasi-insulator device is configured to reflect a second orthogonal circular polarization to the first, where the second circular polarization occurs when the first circular polarization is reflected in a load to be heated;
    where, in a process of heating the load, of reflection coefficient p, with the first circular polarization, the reflection coefficient at the input of the quasi-insulating device is less than p.
    [2]
    2. System according to any one of claim 1 wherein, the quasi-isolator device is defined by a matrix S of dispersion parameters with a coefficient S11 = 0 and coefficients S12 and S13 that meet that the sum of their squares is equal to 0.
    [3]
    3. System according to any of the preceding claims wherein the modal transition means comprises:
    - means (350) for transforming the linear input polarization into two linear orthogonal polarizations; Y
    - means (351) phase shifters, configured to offset 90 ° the two linear orthogonal polarizations.
    [4]
    4. System according to any of the preceding claims further comprising:
    - an input waveguide (501) connected at one of its ends to an electrical input gate (61) of the quasi-isolator device, where the input waveguide is connectable at another end to a microwave generator ; Y
    - an output waveguide (504), connected at one of its ends to the electrical output doors (62, 63) of the quasi-insulator device, where the Output waveguide is connectable by another of its ends to a microwave antenna.
    [5]
    5. System according to claim 4 further comprising a horn-type microwave antenna (120), connected to the output waveguide and configured to, when excited by the microwaves with the first circular polarization, apply a field electromagnetic on the charge p.
    [6]
    6. System according to claim 5 further comprising an adapter module (352) disposed between the exit doors of the quasi-isolator device and an entrance door of the horn-type microwave antenna.
    [7]
    7. System according to any one of the preceding claims 4-6 wherein the input waveguide and the output waveguide have double symmetry, and wherein the output waveguide is a circular waveguide comprising a single physical exit door for the two electrical exit doors (62, 63) of the quasiaislator device, each of them for each of the two modes TE11 of the circular waveguide.
    [8]
    8. System according to claim 1 wherein the modal transition means are arranged on a dielectric substrate (72) and comprise:
    - phase shifting means configured to offset a linearly polarized input signal; Y
    - a patch-type antenna (71) with two orthogonal inputs (73, 74) connected to the electrical output doors (62, 63) of the quasi-isolating device, configured to radiate an electromagnetic field of circular polarization.
    [9]
    9. System according to any of the preceding claims, further comprising an input polarizer connected to an electrical input gate of the quasi-isolator device, configured to transform a circular input polarization into a linear output polarization.
    [10]
    10. System according to any of the preceding claims wherein the modal transition means are part of the quasi-insulator device.
    [11]
    11. Method for microwave heating comprising the steps:
    - providing a linearly polarized microwave signal at an input of a quasi-insulating, passive, reciprocal device, with three electric doors and attachable to a microwave transmission chain,
    - transforming, in modal transitional means, the linearly polarized microwave signal into a first circularly polarized microwave signal;
    - applying, by a microwave antenna, the first circularly polarized microwave signal to a reflection coefficient load p, so that a part of the circularly polarized microwave signal is reflected in the load and a second circularly polarized signal is produced orthogonal to the first; Y
    - reflect, in the quasi-insulator device, the second signal circularly polarized and orthogonal to the first, so that a reflection coefficient is produced at the input of the quasi-insulator device less than p.
    [12]
    12. Method according to claim 11, further comprising defining the quasi-insulator device by means of a matrix S of dispersion parameters, establishing the following conditions: a coefficient S11 = 0 and coefficients S12 and S13 that meet the sum of its squares equals 0;
    [13]
    13. Method according to any of claims 11-12 wherein transforming the linearly polarized microwave signal into the first circularly polarized microwave signal comprises:
    - transform the linear input polarization into two orthogonal linear polarizations; Y
    - 90 ° offset the two linear orthogonal polarizations.
    [14]
    14. Method according to any of claims 11-13, further comprising:
    - generate the microwave signal in a microwave generator;
    - guide, by an input waveguide, the microwave signal to the quasi-isolator device;
    - guide, by an output waveguide, the first circularly polarized microwave signal to a microwave antenna, configured to apply it to the load.
    [15]
    15. Method according to claim 14, further comprising determining a working frequency and selecting a geometry for the input waveguide and the output waveguide, as a function of said frequency.
    [16]
    16. A method according to any of claims 11-15 which further comprises transforming, by an input polarizer connected between the input of the quasi-isolator device and a microwave generator with circular polarization, a circularly polarized signal in the microwave signal linearly polarized that is provided at the input of the quasi-insulator device.
    [17]
    17. Method according to claim 11 wherein transforming the linearly polarized microwave signal into the first circularly polarized microwave signal comprises:
    - 90 ° offset the linearly polarized microwave signal provided at the input of the quasi-isolator device; Y
    - provide the two 90 ° offset signals in two inputs arranged orthogonally on a microstrip patch antenna, where the microstrip patch antenna is configured to radiate the first circularly polarized microwave signal that is applied to the load.
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    同族专利:
    公开号 | 公开日
    WO2020254701A1|2020-12-24|
    ES2734379B2|2020-06-05|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4336434A|1980-08-15|1982-06-22|General Electric Company|Microwave oven cavity excitation system employing circularly polarized beam steering for uniformity of energy distribution and improved impedance matching|
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    ES201930549A|ES2734379B2|2019-06-17|2019-06-17|SYSTEM AND METHOD TO IMPROVE THE ENERGY PERFORMANCE OF A MICROWAVE WARMING PROCESS|ES201930549A| ES2734379B2|2019-06-17|2019-06-17|SYSTEM AND METHOD TO IMPROVE THE ENERGY PERFORMANCE OF A MICROWAVE WARMING PROCESS|
    PCT/ES2020/070273| WO2020254701A1|2019-06-17|2020-04-28|System and method for improving the energetic performance of a heating process by microwaves|
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