Homodyne cellular base station

• US 5,918,169 A
• Filed: 09/25/1996
• Issued: 06/29/1999
• Est. Priority Date: 09/25/1996
• Status: Expired due to Term

• Current Assignee: Unwired Planet LLC (JP Morgan Chase & Co)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul W.
• Primary Examiner(s): Faile, Andrew I.
• Assistant Examiner(s): Le, Vu
• Application Number:
  US08/719,788
• Time in Patent Office: 1,007 Days
• Field of Search: 455/324, 455/118, 455/130, 455/131, 455/511, 455/313, 455/255-257, 455/189.1, 455/190.1, 455/192.1, 455/561, 455/434, 455/455, 455/516, 455/517, 455/334 , 455/552-553
• US Class Current: 455/324
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

A method and apparatus for providing a homodyne cellular base station. A cellular antenna is coupled to both a conventional signal channel receiver 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 downconverter 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.

Claims

1. A cellular base station comprising:

means for receiving a cellular band signal;

a homodyne converter for converting the cellular band signal to a complex baseband signal, comprising;

a quadrature downconverter for mixing the cellular band signal with a local oscillator signal; and

a local oscillator for generating the local oscillator signal, wherein the frequency of the generated local oscillator signal corresponds to a control channel frequency of the cellular band signal such that all DC offsets in the complex baseband signal are associated with the control channel frequency;

means for digitizing the complex baseband signal;

means for processing the digitized complex baseband signal to separate traffic channels from the baseband signal; and

a single channel receiver for receiving a control channel within the cellular band signal.

2. The base station of claim 1 wherein the means for receiving further includes:

an antenna for receiving the cellular band signal;

a band pass filter for rejecting signals other than the cellular band signal, and

an amplifier for amplifying the received cellular band signal.

3. The base station of claim 2, further including first and second buffers for coupling the means for performing a homodyne conversion and the single channel receiver to the antenna.

4. The base station of claim 1, further including a high-pass filter for removing the control channel from the complex baseband signal.

5. The base station of claim 1, further including signal sorting means for sequentially selecting said separated traffic channels according to a predetermined frequency-hopping sequence in order to reassemble frequency-hopped traffic signals.

6. A cellular radio base station comprising:

an antenna for receiving a cellular band signal;

a multi-channel homodyne receiver coupled to the antenna for converting the received cellular band signal to a complex baseband signal, the homodyne receiver performing homodyne downconversion of the received cellular band signal to a complex baseband signal such that a control channel frequency is an only frequency channel in the baseband signal affected by DC offsets;

means for digitally extracting traffic channels from the baseband signal; and

a single channel receiver coupled to the antenna for receiving a control channel.

7. The base station of claim 6 wherein the homodyne receiver further includes:

a quadrature downconverter for mixing the cellular band signal with a local oscillator signal; and

a local oscillator for generating the local oscillator signal, wherein a frequency of the generated local oscillator signal corresponds to a control channel frequency of the cellular band signal.

8. The base station of claim 7, further including a high-pass filter for removing the control channel frequency from the complex baseband signal.

9. The base station of claim 6, further including first and second buffers for coupling the homodyne receiver and the signal channel receiver to the antenna.

10. The base station of claim 6, further including a signal sorter for sequentially selecting outputs of said multi-channel receiver according to a predetermined frequency-hopping sequence in order to reassemble frequency-hopped traffic information.

11. A method for processing a cellular band signal containing voice channels and a control channel using a homodyne receiver comprising the steps of:

receiving a cellular band signal;

performing a homodyne conversion of the cellular band signal to a complex baseband signal such that all DC offset of the complex baseband signal reside within a frequency of the control channel;

extracting the voice channels from the converted complex baseband signal; and

extracting the control channel from the received cellular band signal using a single channel receiver.

12. The method of claim 11 wherein the step of preforming a homodyne conversion further includes the steps of:

selecting a local oscillator signal having a frequency equivalent to the control channel frequency to ensure all DC offsets are within the control channel frequency; and

mixing the local oscillator signal with the cellular band signal to generate the complex baseband signal.

13. The method of claim 11, further including the step of filtering the DC offset and control channel from the converted complex baseband signal.

14. The method of claim 11 wherein the step of extracting the voice channels further includes the steps of:

digitizing the complex baseband signal; and

digitally filtering the complex baseband signal to separate the baseband signal into each of the voice channels.