Homodyne cellular base station

专利摘要:
PURPOSE: A homodyne cellular base station is provided to use homodyne transformation of cellular band signals received to synchronize signals of a base station. CONSTITUTION: A cellular antenna of a homodyne cellular base station is coupled to both a conventional signal channel receiver and a homodyne receiver. The conventional single channel receiver is configured to receive the control channel from a cellular band signal. The homodyne receiver utilizes a quadrature down converter and local oscillator to receive the voice channels. The local oscillator is tuned to the frequency of the control channel to limit all DC offsets to the control channel within the homodyne receiver. All DC offsets and the control channel frequency are filtered from the homodyne receiver signal and, the filtered signal is then digitized and digitally processed to separate the signal into each of the traffic channels.
公开号:KR20000048583A
申请号:KR1019990702510
申请日:1997-09-24
公开日:2000-07-25
发明作者:덴트폴다블유
申请人:도날드 디. 먼둘；에릭슨 인크.；
IPC主号:

专利说明:

Homodyne cellular base station {HOMODYNE CELLULAR BASE STATION}
Existing cellular radio base stations require a significant amount of expensive hardware to receive the control and traffic channels used in cellular communication technology. The control channel carries signals that control cellular voice signals to and from the cellular radio base station and the mobile unit. The traffic channel carries voice transmission data between the base station and the mobile unit. Critical equipment prices associated with conventional receivers used in cellular radio base stations have resulted in significant cost increases for users of cellular technology. Base stations that use significantly less hardware and are less expensive to equipment will benefit both cellular providers and customers paying for cellular services.
FIELD OF THE INVENTION The present invention relates to cellular radio base stations, and in particular, to cellular radio base stations that employ homodyne conversion of received cellular band signals to synthesize base station signals.
1 is a block diagram illustrating a process performed by a cellular base station homodyne to a received cellular band signal.
2 is a block diagram of a homodyne cellular base station.
3 illustrates a sectorized antenna configuration;
The present invention describes a method and apparatus for providing a control channel using a homodyne receiver with a single channel receiver and a homodyne cellular base station receiving each of the traffic channels of a cellular band signal. The base station includes an antenna for receiving cellular band signals, an associated filter and an amplifier for processing the received cellular band signals. Conventional single-channel receivers for receiving control channels and homodyne receivers for receiving traffic channels are connected to the antenna via a pair of buffers.
The homodyne receiver consists of an orthogonal downlink frequency converter that mixes the local oscillator signal and the cellular band signal to down-convert the cellular signal into I and Q output signals. The local oscillator signal frequency corresponds to the control channel frequency of the cellular band signal. This allows all DC offsets in the I and Q output signals to remain in the control channel only. The highpass filter removes any DC offset components and control channels from the I and Q output signals of the quadrature downlink frequency converter. The remainder of the signal is then digitized using an analog-to-digital converter. The digital signal is then processed by a digital signal processor (DSP) and each of the traffic channels is extracted from the digitized signal using digital filtering.
The single channel receiver is configured to detect only the control channel of the cellular band signal since this channel is filtered from the signal processed by the homodyne receiver. Once the control channel is detected, the traffic channels separate from the control channel are processed by the cellular base station as needed.
A more complete understanding of the method and apparatus of the present invention may be made by reference to the following detailed description taken in conjunction with the accompanying drawings.
Referring to the drawings, and in particular with reference to FIG. 1, a process performed by a homodyne cellular base station in the channels of a cellular band signal is described. Initially, in step 10 the base station receives the cellular band signal and a pair of receivers processes the signal. One of the receivers performs a homodyne transformation on the cellular band signal, converting this signal into a complex baseband signal in step 12. Homodyne transformation of the cellular baseband signal will be described more fully with reference to FIG. 2 soon.
The complex baseband signal is digitized by the digital-to-analog converter in step 14 and also processed by the digital signal processor in step 16. The digital signal processor performs channel separation of the converted baseband signal to extract each of the traffic channels in the received cellular band signal. The second receiver is a single channel receiver tuned to detect a control channel within the cellular band signal in step 18.
Referring to FIG. 2, shown is a block diagram of a cellular base station implementing the process described with respect to FIG. 1. The cellular base station has an antenna 20 that receives cellular band signals from multiple mobile units (not shown). The received signals pass through a bandpass filter 22 to discard any signals other than cellular band mobile unit signals. The filtered cellular signals are amplified through an amplifier 24 and then through a pair of buffers 26 to a homodyne receiver 27 and a single channel receiver 29. The buffer 26 limits homodyne downlink frequency-converted oscillator leakage that may interfere with the reception of the single channel receiver 29. In a preferred embodiment, the buffers have a high isolation buffer amplifier and / or ferrite isolator connected to the inputs of homodyne receiver 27 and single channel receiver 29.
The quadrature downlink frequency converter 28 (I, Q mixer) mixes the received cellular band signal and the local signal generated by the local oscillator 30 to down-frequency convert the signal into a complex baseband I, Q signal. Downlink frequency converter 28 and local oscillator 30 comprise a homodyne receiver 27. The homodyne receiver 27 suffers from the well-known DC offset in the I, Q output signals of the downlink frequency converter 28, as described in Applicant's US Pat. No. 5,241,702, which is incorporated herein by reference. The DC offset in the I and Q output signals is significantly greater than the received cellular signal components. Thus, there is the potential for loss or masking of the desired portion of the cellular signal.
The problem of DC offset can be overcome according to the present invention by setting the local oscillator 30 at the same frequency as the frequency of the control channel assigned to the cell in the cellular band. This is possible because the control channel is a fixed frequency channel. By setting the local oscillator frequency equal to the control channel frequency, the control channel is mapped to a complex I, Q baseband zero frequency or DC, so that the control channel is the only frequency channel that is interfered by an unwanted DC offset from the orthogonal transform. to be.
Since all traffic channels are replaced by at least one traffic channel spaced away from the DC, the traffic channels are protected from interference by the DC offset. Traffic channels are also protected by filtering the signal from the quadrature downlink frequency converter 28 through a highpass filter 32 to remove unwanted DC offset and control channel energy from the signal. High pass filtering of the signal also prevents instantaneous non-power controlled mobile units from randomly accessing the control channel to prevent overloading the homodyne receiver 27.
The filtered I, Q outputs of the homodyne receiver 27 are digitized using an analog-to-digital converter 34. The digitized signal is then processed by the digital signal processor 36. The digital signal processor 36 performs channel separation on the digital signal to extract the respective audio channels from the digital signal using digital filtering functions encoded in the digital signal processor 36.
The control channel is received at a conventional single channel receiver 29, independent of the control channel frequency. The control channel and traffic channels are then processed by a cellular base station controller (not shown) to control cellular communication between the base station and the mobile unit.
In a GSM system, the control channel occupies one TDMA timeslot at a fixed frequency. Traffic signals may occupy other timeslots during the TDMA frame period and may also be frequency-hopped. In a GSM system, the control channel receiver is digitally controlled by a signal sorter 38 (shown in broken lines) that re-assembles the frequency hopped timeslots of each traffic channel to reconstruct the re-hopped signals for processing. Processed with the output of separate traffic channels. This is known as "baseband frequency re-hopping". If AMPS or IS54 (D-AMPS) systems are digitized, there is no frequency-hopping so no signal sorter 38 is needed.
In another embodiment of the present invention employing a sectorized system having a 120 degree sector antenna in three cells (FIG. 3), the homodyne center frequency of a sector oscillator of one sector is such that the isolation between the different sector antennas is homodyne. It is selected to be a calling channel of another sector to provide additional isolation between the receiver and the conventional receiver.
Alternatively, the local oscillator frequency of a particular sector may be deliberately selected to be equivalent to the control channel or traffic channel frequency assigned to another sector or an adjacent base station, such that the frequency is not used in that particular sector.
Although embodiments of the method and apparatus of the present invention are shown in the accompanying drawings and described in the above detailed description, the present invention is not limited to the described embodiments, and the present invention as defined in the following claims is not to be construed. It will be appreciated that numerous modifications, reconfigurations and alternatives are possible without departing from the scope of the present disclosure.

权利要求:
Claims (18)
[1" claim-type="Currently amended] Means for receiving a cellular band signal;
Means for performing homodyne conversion of the cellular band signal to a complex baseband signal;
Means for digitizing a complex baseband signal;
Means for processing a digitized complex baseband signal to separate traffic channels from the baseband signal; And
And a single channel receiver for receiving a control channel in a cellular band signal.
[2" claim-type="Currently amended] The method of claim 1, wherein the means for performing homodyne transformation is:
An orthogonal downlink frequency converter for mixing cellular band signals and local oscillator signals; And
And a local oscillator for generating a local oscillator signal whose frequency corresponds to the control channel frequency of the cellular band signal.
[3" claim-type="Currently amended] The method of claim 1 wherein said receiving means is:
An antenna for receiving a cellular band signal;
A bandpass filter for blocking signals other than cellular band signals; And
And a amplifier for amplifying the received cellular band signal.
[4" claim-type="Currently amended] 4. The cellular base station of claim 3, further comprising first and second buffers connecting the single channel receiver to the antenna for means for performing homodyne conversion.
[5" claim-type="Currently amended] 2. The cellular base station of claim 1, further comprising a highpass filter that removes the control channel from the complex baseband signal.
[6" claim-type="Currently amended] 2. The cellular base station of claim 1, further comprising signal sorting means for successively selecting the separated traffic channels according to a predetermined frequency-hopping order to re-assemble the frequency-hopped traffic signals.
[7" claim-type="Currently amended] A multi-sector oriented antenna for receiving cellular signals from multiple directions and producing corresponding sector signals; And
Each sector with a local oscillator frequency configured such that the local oscillator frequency used in the first sector is equal to the channel frequency used in the second sector to produce a down-frequency transformed quadrature baseband signal comprising I and Q signals. A cellular base station having a homodyne downlink frequency converter for mixing signals.
[8" claim-type="Currently amended] 8. The cellular base station of claim 7, wherein the second sector is located in an adjacent base station.
[9" claim-type="Currently amended] An antenna for receiving a cellular band signal;
A multi-channel receiver coupled to an antenna for a traffic channel digitally separated from the received cellular band signal; And
And a single channel receiver coupled to the antenna for receiving the control channel.
[10" claim-type="Currently amended] 10. The system of claim 9, wherein the multi-channel receiver is:
Means for performing homodyne downlink frequency conversion of the received cellular band signal to a complex baseband signal;
Means for digitizing a complex baseband signal; And
And a digital signal processing means for separating the baseband signal into traffic channel frequencies.
[11" claim-type="Currently amended] The method of claim 10, wherein the means for performing homodyne transformation is:
An orthogonal downlink frequency converter for mixing the cellular band signal and the local oscillator signal; And
And a local oscillator for generating a local oscillator signal whose frequency coincides with the control channel frequency of the cellular band signal.
[12" claim-type="Currently amended] 11. The cellular base station of claim 10, further comprising means for performing homodyne conversion and first and second buffers coupling the signal channel receiver to the antenna.
[13" claim-type="Currently amended] 12. The cellular base station of claim 11, further comprising a highpass filter that removes the control channel frequency from the complex baseband signal.
[14" claim-type="Currently amended] 10. The cellular base station of claim 9, further comprising a signal sorter for successively selecting the outputs of the multi-channel receiver in accordance with a predetermined frequency-hopping order to re-assemble frequency-hopping traffic information. .
[15" claim-type="Currently amended] In a method for processing a cellular band signal using a homodyne receiver:
Receiving a cellular band signal;
Performing a homodyne conversion of the cellular band signal to a complex baseband signal such that all DC offsets remain in the control channel;
Extracting a voice channel from the transformed complex baseband signal; And
Extracting a control channel from the received cellular band signal.
[16" claim-type="Currently amended] The method of claim 15, wherein performing the homodyne transformation is:
Selecting a local oscillator signal having a frequency equal to the control channel frequency; And
Mixing the local oscillator signal and the cellular band signal to produce a complex baseband signal.
[17" claim-type="Currently amended] 16. The method of claim 15, further comprising filtering a DC offset and a control channel from the transformed complex baseband signal.
[18" claim-type="Currently amended] 16. The method of claim 15, wherein extracting voice channels comprises:
Digitizing the complex baseband signal; And
And digitally filtering the complex baseband signal to separate the baseband signal into respective voice channels.

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引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
1996-09-25|Priority to US08/719,788

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1996-09-25|Priority to US8/719,788

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1997-09-24|Application filed by 도날드 디. 먼둘, 에릭슨 인크.

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2000-07-25|Publication of KR20000048583A

优先权:

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申请号 | 申请日 | 专利标题

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US08/719,788|US5918169A|1996-09-25|1996-09-25|Homodyne cellular base station|

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US8/719,788|1996-09-25|