US 7,379,725 B2 | ||
LNA gain adjustment in an RF receiver to compensate for intermodulation interference | ||
Hong Shi, Redondo Beach, Calif. (US) | ||
Assigned to Broadcom Corporation, Irvine, Calif. (US) | ||
Filed on Sep. 19, 2006, as Appl. No. 11/523,332. | ||
Prior Publication US 2007/0010224 A1, Jan. 11, 2007 | ||
Int. Cl. H04B 1/10 (2006.01) |
U.S. Cl. 455—296 [455/226.2; 455/295; 455/302] | 4 Claims |
1. A method comprising:
receiving a radio frequency signal at an input of a low noise amplifier during a guard period when a carrier corresponding
to a signal of interest is not present;
measuring wideband signal strength indication (RSSI_A) at an output of a mixer, the mixer coupled to receive an output of
the low noise amplifier;
determining if mixer non-linearity is present based upon the wideband signal strength indication;
reducing gain of the low noise amplifier if mixer non-linearity is present, until the mixer is no longer driven into non-linearity;
determining if wideband signal strength indication exceeds a predetermined threshold that causes the mixer to operate in an
upper range of mixer operation;
measuring narrowband signal strength indication (RSSI_B) after band pass filtering the output of the mixer, if wideband signal
strength indication exceeds the predefined threshold;
determining if intermodulation interference is present using the narrowband signal strength indication;
optimizing a signal-to-interference ratio of the mixer by setting the gain of the low noise amplifier to have the mixer operate
within its linear region of operation, if intermodulation interference is detected; and
setting the gain of the low noise amplifier so that narrowband signal strength indication exceeds a predetermined minimum,
in which a combination of wideband signal strength indication and narrowband signal strength indication based gain adjustments
of the low noise amplifier is employed to compensate for intermodulation interference.
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