Trimming of local oscillation in an integrated circuit radio

• US 20070002974A1
• Filed: 09/05/2006
• Published: 01/04/2007
• Est. Priority Date: 04/29/2002
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Ibrahim, Brima, Jensen, Henrik
• Granted Patent: US 7,580,483 B2
• Time in Patent Office: Days
• US Class Current: 375/324
• CPC Class Codes: H04L 2027/003 at baseband only
• CPC Class Codes: H04L 2027/0053 Closed loops
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296
• CPC Class Codes: H04L 25/063 Setting decision thresholds using feedback techniques only
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

A method and apparatus for trimming of a local oscillation within a radio frequency integrated circuit (RFIC) includes processing that begins when an RFIC receives a radio frequency (RF) signal having a known frequency. The processing then continues when the RFIC mixes the RF signal with a receiver local oscillation to produce a low intermediate frequency (IF) signal, which may have a carrier frequency of zero (i.e., a baseband signal) or up to a few mega Hertz). The processing then continues when the RFIC demodulates the low IF signal to produce demodulated data. The processing then continues as the RFIC determines a DC offset from the demodulated data, where the DC offset is reflective of the difference between the known frequency and the frequency of the receiver local oscillation. The processing then continues as the RFIC adjusts the receiver local oscillation to reduce the DC offset when the DC offset compares unfavorably with an allowable offset threshold.

Claims

1-24. -24. (canceled)

25. A method comprising:

mixing a received radio signal with a local oscillation signal to produce a demodulated signal;

determining a DC offset from the demodulated signal;

determining if magnitude of the DC offset exceeds an upper limit of an allowable offset threshold or lower limit of the allowable offset threshold; and

adjusting the local oscillation signal to reduce the DC offset when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold.

26. The method of claim 25 further comprising demodulating to produce the demodulated signal, wherein the demodulating includes bandpass filtering a mixed signal to produce a filtered signal, converting the filtered signal into a digital signal and demodulating the digital signal to produce demodulated data.

27. The method of claim 25, wherein the adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, determining a fractional adjustment value based on the DC offset such that the local oscillation signal plus frequency of a mixed signal substantially equals a frequency of the radio signal, wherein the local oscillation signal is partially based on the fraction adjustment value.

28. The method of claim 25, wherein the adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, iteratively adjusting a fractional adjustment value until the magnitude of the DC offset resides within the allowable offset threshold, wherein the receiver local oscillation is partially based on the fractional adjustment value.

29. The method of claim 25, wherein the adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, adjusting a reference frequency based on the DC offset such that the local oscillation signal plus frequency of a mixed signal substantially equals a frequency of the radio signal, wherein the local oscillation signal is based on the reference frequency.

30. An apparatus comprising:

means for mixing a received radio signal with a local oscillation signal to produce a demodulated signal;

means for determining a DC offset from the demodulated signal;

means for determining if magnitude of the DC offset exceeds an upper limit of an allowable offset threshold or lower limit of the allowable offset threshold; and

means for adjusting the local oscillation signal to reduce the DC offset when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold.

31. The apparatus of claim 30 further comprising means for demodulating to produce the demodulated signal, wherein the means for demodulating demodulates by bandpass filtering a mixed signal to produce a filtered signal, converting the filtered signal into a digital signal and demodulating the digital signal to produce demodulated data.

32. The apparatus of claim 30, wherein the means for adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, determining a fractional adjustment value based on the DC offset such that the local oscillation signal plus frequency of a mixed signal substantially equals a frequency of the radio signal, wherein the local oscillation signal is partially based on the fraction adjustment value.

33. The apparatus of claim 30, wherein the means for adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, iteratively adjusting a fractional adjustment value until the magnitude of the DC offset resides within the allowable offset threshold, wherein the receiver local oscillation is partially based on the fractional adjustment value.

34. The apparatus of claim 30, wherein the means for adjusting the local oscillation signal when the magnitude of the DC offset exceeds the upper limit or the lower limit of the allowable offset threshold includes, adjusting a reference frequency based on the DC offset such that the local oscillation signal plus frequency of a mixed signal substantially equals a frequency of the radio signal, wherein the local oscillation signal is based on the reference frequency.