Method and system for a shared GM-stage between in-phase and quadrature channels

• US 8,023,591 B2
• Filed: 12/31/2006
• Issued: 09/20/2011
• Est. Priority Date: 12/06/2006
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Hafizi, Madjid
• Primary Examiner(s): WANG, TED M
• Application Number:
  US11/618,866
• Publication Number:
  US 20080139162A1
• Time in Patent Office: 1,724 Days
• Field of Search: 455/325, 455/326, 327/355, 375/316, 375/334
• US Class Current: 375/334
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

Aspects of a method and system for a shared GM-stage between in-phase and quadrature channels may include processing an in-phase (I) component signal for the I channel and a quadrature (Q) component signal for the Q channel via one or more shared transconductance stages in a frequency demodulator. The I channel may be isolated from the Q channel and the Q channel may be isolated from the I channel using isolation resistors. The values of the isolation resistors may be selected so as to balance the isolation and signal attenuation. A folding circuit, comprising active devices, may isolate the I channel from the Q channel. A generated voltage may be utilized to bias the folding circuit. An oscillator for the I channel may be isolated from a mixer for the Q channel and an oscillator for the Q channel may be isolated from a mixer for the I channel.

Claims

1. A method for processing signals in a communications system, the method comprising:

processing an in-phase component signal for an in-phase channel and a quadrature component signal for a quadrature channel utilizing a shared transconductance stage in a frequency demodulator;

generating a single differential output signal for said in-phase component signal and said quadrature component signal in said transconductance stage, wherein a load is communicatively coupled between a pair of output terminals of said transconductance stage corresponding to said single differential output signal; and

adjusting a linearity of said transconductance stage utilizing one or more biasing signals.

2. The method according to claim 1, comprising isolating said in-phase channel from said quadrature channel.

3. The method according to claim 2, comprising isolating said in-phase channel from said quadrature channel using isolation resistors.

4. The method according to claim 3, comprising selecting a resistance value for said isolation resistors to balance signal attenuation and said isolating.

5. The method according to claim 2, comprising isolating an oscillator for said in-phase channel from a mixer for said quadrature channel.

6. The method according to claim 2, comprising isolating an oscillator for said quadrature channel from a mixer for said in-phase channel.

7. The method according to claim 1, comprising converting said load of said frequency demodulator from a passive load to an active load.

8. The method according to claim 7, comprising generating a common-mode feedback signal when said active load is configured to operate in an active mode.

9. The method according to claim 8, wherein said common mode feedback signal is generated via a common mode feedback circuit communicatively coupled to said active load to operate in said active mode.

10. The method according to claim 1, comprising generating a bias current when an RF mixer within said frequency demodulator is configured to operate in an active mode.

11. The method according to claim 10, comprising generating a common-mode feedback signal when said RF mixer is configured to operate in said active mode.

12. The method according to claim 11, wherein said common mode feedback signal is generated via a common mode feedback circuit communicatively coupled to said RF mixer.

13. The method according to claim 1, comprising processing wideband modulated signals when said frequency demodulator is configured to operate with an active transconductance-stage load.

14. The method according to claim 1, comprising processing narrowband modulated signals when said frequency demodulator is configured to operate with a passive transconductance-stage load.

15. A system for processing signals in a communications system, the system comprising:

a frequency demodulator comprising a shared transconductance stage that is operable to process an in-phase component signal for an in-phase channel and a quadrature component signal for a quadrature channel;

said frequency demodulator is operable to generate a single differential output signal for said in-phase component signal and said quadrature component signal in said transconductance stage, wherein a load is communicatively coupled between a pair of output terminals of said transconductance stage corresponding to said single differential output signal; and

said frequency demodulator is operable to adjust a linearity of said transconductance stage utilizing one or more biasing signals.

16. The system according to claim 15, comprising one or more circuits that isolate said in-phase channel from said quadrature channel.

17. The system according to claim 16, comprising isolation resistors that isolate said in-phase channel from said quadrature channel.

18. The system according to claim 17, wherein resistance values for said isolation resistors results in balancing signal attenuation and said isolating.

19. The system according to claim 16, wherein said one or more circuits isolates an oscillator for said in-phase channel from a mixer for said quadrature channel.

20. The system according to claim 16, wherein said one or more circuits isolates an oscillator for said quadrature channel from a mixer for said in-phase channel.

21. The system according to claim 15, comprising one or more circuits that converts said load of said frequency demodulator from a passive load to an active load.

22. The system according to claim 21, wherein said one or more circuits generates a common-mode feedback signal when said active load is configured to operate in an active mode.

23. The system according to claim 22, comprising a common mode feedback circuit communicatively coupled to said active load that operates in said active mode and generates said common mode feedback signal.

24. The system according to claim 15, comprising one or more circuits that generates a bias current when an RF mixer within said frequency demodulator is configured to operate in an active mode.

25. The system according to claim 24, wherein said one or more circuits generates a common-mode feedback signal when said RF mixer is configured to operate in said active mode.

26. The system according to claim 25, comprising a common mode feedback circuit communicatively coupled to said RF mixer that generates said common mode feedback signal.

27. The system according to claim 15, comprising one or more circuits that processes wideband modulated signals when said frequency demodulator is configured to operate with an active transconductance-stage load.

28. The system according to claim 15, comprising one or more circuits that processes narrowband modulated signals when said frequency demodulator is configured to operate with a passive transconductance-stage load.