# US 2010/0167680 A1 · Controllable image cancellation in a radio receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0167680 A1 - Document ID: US20100167680A1 - Status: Published application - Kind: A1 - Application number: 12/317,786 - Filed: 2008-12-30 - Published: 2010-07-01 - Earliest claimed: 2008-12-30 - Assignees: Silicon Laboratories Inc. - Inventors: Junsong Li; John Khoury - Web page: https://patentgrep.com/patent/US20100167680A1 ## CPC - H04B 1/28: the receiver comprising at least one semiconductor device having three or more electrodes - H04B 1/0032: {with analogue quadrature frequency conversion to and from the baseband (quadrature modulators and demodulators per se H03D3/007, H03C3/40)} - H04B: TRANSMISSION ## Abstract In one embodiment, a receiver includes parallel paths for signal channel processing and image channel processing. The paths may include a mixer to receive an intermediate frequency (IF) signal and to downconvert the IF signal to a channel baseband signal, a filter to generate a filtered channel value, a combiner to combine the channel baseband signal with a filtered channel value from the other path to obtain a channel path output, in addition to one or more controllers to generate a step control signal and update a weighting of the filters based at least in part on the step control signal. ## Claims ### Claim 1 An apparatus comprising: a signal channel path including: a first mixer to receive an intermediate frequency (IF) signal and to downconvert the IF signal to a signal channel baseband signal; a signal filter to receive a value of the signal channel baseband signal and to generate a filtered signal channel value; a first combiner to combine the signal channel baseband signal with a filtered image channel value to obtain a signal channel path output; an image channel path including: a second mixer to receive the IF signal and to downconvert the IF signal to an image channel baseband signal; an image filter to receive a value of the image channel baseband signal and to generate the filtered image channel value; a second combiner to combine the image channel baseband signal with the filtered signal channel value to obtain an image channel path output; a first controller to determine a signal strength of the signal channel baseband signal and the image channel baseband signal and to generate a step control signal based at least in part on the signal strengths; and a second controller to receive the signal channel path output and the image channel path output and to update a weighting of the image filter and the signal filter based on the signal channel path output, the image channel path output and the step control signal. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the signal channel path further includes a first programmable decimator coupled to the first mixer to receive the signal channel baseband signal and to output the signal channel baseband signal at a selected sample rate. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the first programmable decimator is controllable to output the signal channel baseband signal at the selected sample rate based on a selected radio band of operation. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the first controller is to determine whether to enable image cancellation via the image filter based on a difference between the signal strength of the signal channel baseband signal and the image channel baseband signal. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein the first controller is to generate the step control signal with a first value during an acquisition mode and with a second value during a tracking mode. ### Claim 6 (depends on 4) The apparatus of claim 4, wherein the first controller is to generate the step control signal based on a comparison of the difference between the signal strengths of the signal channel baseband signal and the image channel baseband signal and a second difference between signal strengths of the signal channel path output and the image channel path output. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the second controller is to generate a cross-correlation value of the signal channel path output and the image channel path output, obtain a product of the cross-correlation value and the step control signal, and obtain a sum of the product and a value of a delay element of the image filter and to update a tap of the image filter with the sum. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the cross-correlation value is a mean value for a data block, and wherein the second controller is to calculate a cross-correlation between the signal channel path output and the image channel path output for only a predetermined number of samples of the data block. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the apparatus comprises a digital circuit to receive the IF signal as a digital complex signal and to provide the signal channel path output to a digital signal processor to perform demodulation of the signal channel path output to output audio information. ### Claim 10 A method comprising: calculating a signal strength of a pre-filtered image channel signal and a pre-filtered desired channel signal obtained in a receiver; determining whether the signal strength of the pre-filtered image channel signal is greater than the signal strength of the pre-filtered desired channel signal by at least a threshold level; and if so, enabling image cancellation processing, otherwise disabling the image cancellation processing. ### Claim 11 (depends on 10) The method of claim 10, further comprising if the image cancellation processing is enabled, determining whether the receiver is in an acquisition mode or in a tracking mode, and generating a step control signal for a filter updater having a first level if the receiver is in the acquisition mode and having a second level if the receiver is in the tracking mode. ### Claim 12 (depends on 11) The method of claim 11, wherein the tracking mode is determined based on a comparison of the difference between the signal strengths of the pre-filtered desired channel signal and the pre-filtered image channel signal and a second difference between signal strengths of a post-filtered desired channel signal and a post-filtered image channel signal. ### Claim 13 (depends on 11) The method of claim 11, further comprising generating a cross-correlation value of a post-filtered desired channel signal and a post-filtered image channel signal, obtaining a product of the cross-correlation value and the step control signal, and obtaining a sum of the product and a value of a delay element of an image filter and updating a tap of the image filter with the sum. ### Claim 14 (depends on 13) The method of claim 13, further comprising calculating a cross-correlation for a predetermined number of samples of a data block, the predetermined number substantially less than the samples of the data block. ### Claim 15 A system comprising: an antenna to receive a radio frequency (RF) signal; an analog front end to receive the RF signal from the antenna and to downconvert the RF signal to an intermediate frequency (IF) signal and to convert the IF signal to a digital complex signal; a digital front end coupled to the analog front end, the digital front end including an image canceller to perform image rejection, the image canceller including: an image channel path, the image channel path parallel to a signal channel path and including: a mixer to receive the digital complex signal, and to downconvert the digital complex signal to an image channel baseband signal; an image filter to receive a value of the image channel baseband signal and to generate a filtered image channel value; a combiner to combine the image channel baseband signal with a filtered signal channel value from the signal channel path to obtain an image channel path output; a first controller to determine a signal strength of a signal channel baseband signal and the image channel baseband signal and to generate a step control signal based at least in part on the signal strengths; and a second controller to receive a signal channel path output and the image channel path output and to update a weighting of the image filter based on the signal channel path output, the image channel path output and the step control signal; and a digital signal processor coupled to the digital front end to receive and demodulate the signal channel path output. ### Claim 16 (depends on 15) The system of claim 15, wherein the first controller is to determine whether to enable image cancellation via the image canceller, based on a difference between the signal strengths of the image channel baseband signal and the desired channel baseband signal. ### Claim 17 (depends on 16) The system of claim 16, wherein the first controller is to generate the step control signal with a first value during an acquisition mode and with a second value during a tracking mode. ### Claim 18 (depends on 15) The system of claim 15, wherein the image canceller further includes a first low pass filter to filter the image channel baseband signal and a second low pass filter to filter the image channel path output. ### Claim 19 (depends on 16) The system of claim 16, wherein the image filter comprises a multi-tap complex filter including a plurality of delay elements each having an output coupled to a first input of a corresponding multiplier, each said multiplier having a second input coupled to receive a coefficient value from a corresponding coefficient element, wherein each said coefficient element is updatable by the second controller. ### Claim 20 (depends on 19) The system of claim 19, wherein the second controller is to update each said coefficient element using a sum value, the sum value obtained via a value of the corresponding coefficient element and a product of a cross-correlation value of the signal channel path output and the image channel path output and the step control signal.