Quadrature receiver sampling architecture

• US 7,139,332 B2
• Filed: 06/28/2002
• Issued: 11/21/2006
• Est. Priority Date: 05/17/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Jaffe, Steven, Yu, Tommy, Krafft, Stephen Edward
• Primary Examiner(s): Corrielus, Jean B.
• Application Number:
  US10/184,766
• Publication Number:
  US 20030215027A1
• Time in Patent Office: 1,607 Days
• Field of Search: 375/220, 375/316, 375/340, 375/350, 375/285, 455/3.01, 455/3.02, 455/141, 708/313
• US Class Current: 375/316
• CPC Class Codes: H04L 27/00 Modulated-carrier systems

Abstract

Quadrature receiver sampling architecture. A signal ADC performs analog to digital conversion for both I and Q streams. An analog MUX selects the appropriate I and the Q baseband analog input streams for input to the ADC at the appropriate time. A digital filter may also be employed to compensate for any introduced delay between the samples of the I and Q channel when seeking to recover the symbols that have been transmitted to a communication receiver that employs this quadrature receiver architecture and/or signal processing. In one embodiment, if an ADC is clocked at a rate of substantially twice the sample rate of the I and Q channels, there will be a one-half sample clock delay between the digital I and digital Q data at the output of the ADC. This delay is then removed before the demodulator processes the input signals to recover the transmitted symbols.

Claims

1. A communication receiver, comprising:

an analog front-end that is operable to receive an analog I stream and an analog Q stream;

a digital processing unit that is communicatively coupled to the analog front-end;

wherein the analog front-end includes a multiplexor and a single analog to digital convener that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby convening the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and

the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream, the digital processing unit includes a digital signal processor, wherein the digital signal processor performs mathematical operations on the digital I stream and the digital Q stream to compensate for delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.

2. The communication receiver of claim 1, further comprising a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from a received analog signal.

3. The communication receiver of claim 1, wherein a selector of the multiplexor and the single analog to digital convener being clocked at a frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream.

4. The communication receiver of claim 1, wherein a selector of the multiplexor being clocked a first frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream;

and

the single analog to digital convener being clocked at a second frequency that is substantially twice the digital sampling frequency of the analog I stream and the analog Q stream.

5. The communication receiver of claim 1, wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.

6. The communication receiver of claim 5, wherein the analog I stream and the analog Q stream are provided to the multiplexor;

an output of the multiplexor is provided to the sample and hold element; and

an output of the sample and hold element is provided to the single analog to digital converter.

7. The communication receiver of claim 5, wherein the analog front-end further comprises at least one additional sample and hold element;

and

wherein the analog I stream is provided to the sample and hold element;

the analog Q stream is provided to the at least one additional sample and hold element;

outputs from the sample and hold element and the at least one additional sample and hold element are provided to the multiplexor; and

an output of the multiplexor is provided to the single analog to digital converter.

8. The communication receiver of claim 1, wherein the communication receiver comprises at least one of a base station receiver, a mobile receiver, a set top box, a tower receiver, a mobile unit, and an high definition television (HDTV) set top box receiver.

9. The communication receiver of claim 8, wherein at least one of the base station receiver and the tower receiver comprises a wireless tower.

10. The communication receiver of claim 8, wherein at least one of the set top box and the HDTV set top box receiver comprises a local satellite dish.

11. The communication receiver of claim 1, wherein the communication receiver is contained within a transceiver, the transceiver also comprises a communication transmitter.

12. The communication receiver of claim 2, wherein the analog signal is received via a wireless communication channel.

13. A satellite communication system, comprising:

a local satellite dish that is operable to receive an analog signal transmitted from a satellite via a wireless communication channel; and

a set top box, communicatively coupled to the local satellite dish via a coaxial cable, that receives the analog signal received by the local satellite dish;

wherein the set top box includes an analog front-end and a digital processing unit, the analog front-end includes a radio frequency interface;

the analog front-end is operable to receive the analog signal transmitted from the satellite and to extract an analog I stream and an analog Q stream therefrom;

the digital processing unit is communicatively coupled to the analog front-end;

the analog front-end includes a multiplexor and a single analog to digital converter that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby converting the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and

the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream;

wherein the digital processing unit includes;

a digital signal processor, a delay element, and a half band interpolating filter;

the delay provided by the delay element is substantially comparable to a time comprises a duration that is substantially comparable to a time required to perform a half band interpolating filtering; and

wherein the delay element and the half band interpolating filter operate cooperatively to compensate for delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.

14. The satellite communication system of claim 13, wherein the analog front-end further comprises a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from the received analog signal.

15. The satellite communication system of claim 13, wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.

16. A communication receiver, comprising:

an analog front-end that is operable to receive an analog I stream and an analog Q stream;

a digital processing unit that is communicatively coupled to the analog front-end;

wherein the analog front-end includes a multiplexor and a single analog to digital convener that operate cooperatively to perform alternative digital sampling of the analog I stream and the analog Q stream thereby convening the analog I stream and the analog Q stream into a digital I stream and a digital Q stream; and

the digital processing unit is operable to perform decimation and de-rotation of a digital sample of the digital I stream and the digital Q stream, the rotation being introduced during the analog to digital conversion of the analog I stream and the analog Q stream, wherein the digital processing unit includes;

a digital signal processor, a delay element, and the half band interpolating filter;

the delay provided by the delay element is substantially comparable to a time includes a duration that is substantially comparable to a time required to perform the half band interpolating filtering; and

wherein the delay element and the half band interpolating filter operate cooperatively to compensate for any delay that occurs during the analog to digital conversion of the analog I stream and the analog Q stream thereby performing the de-rotation of the digital sample of the digital I stream and the digital Q stream.

17. The communication receiver of claim 16, further comprising a radio frequency interface that is operable to extract the analog I stream and the analog Q stream from a received analog signal.

18. The communication receiver of claim 16, wherein a selector of the multiplexor and the single analog to digital convener being clocked at a frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream.

19. The communication receiver of claim 16, wherein a selector of the multiplexor being clocked a first frequency that is substantially twice a digital sampling frequency of the analog I stream and the analog Q stream;

and

the single analog to digital convener being clocked at a second frequency that is substantially twice the digital sampling frequency of the analog I stream and the analog Q stream.

20. The communication receiver of claim 16, wherein the analog front-end further comprises a sample and hold element that is communicatively coupled to the multiplexor.

21. The communication receiver of claim 20, wherein the analog I stream and the analog Q stream are provided to the multiplexor;

an output of the multiplexor is provided to the sample and hold element; and

an output of the sample and hold element is provided to the single analog to digital converter.

22. The communication receiver of claim 20, wherein the analog front-end further comprises at least one additional sample and hold element;

and

wherein the analog I stream is provided to the sample and hold element;

the analog Q stream is provided to the at least one additional sample and hold element;

outputs from the sample and hold element and the at least one additional sample and hold element are provided to the multiplexor; and

an output of the multiplexor is provided to the single analog to digital converter.

23. The communication receiver of claim 16, wherein the communication receiver comprises at least one of a base station receiver, a mobile receiver, a set top box, a tower receiver, a mobile unit, and an high definition television (HDTV) set top box receiver.

24. The communication receiver of claim 23, wherein at least one of the base station receiver and the tower receiver comprises a wireless tower.

25. The communication receiver of claim 23, wherein at least one of the set top box and the HDTV set top box receiver comprises a local satellite dish.

26. The communication receiver of claim 16, wherein the communication receiver is contained within a transceiver, the transceiver also comprises a communication transmitter.

27. The communication receiver of claim 17, wherein the analog signal is received via a wireless communication channel.