# US 2012/0258676 A1 · Filter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2012/0258676 A1 - Document ID: US20120258676A1 - Status: Published application - Kind: A1 - Application number: 13/439,679 - Filed: 2012-04-04 - Published: 2012-10-11 - Earliest claimed: 2011-04-05 - Assignees: Intel Corporation - Inventors: Christopher Brian Smart - Web page: https://patentgrep.com/patent/US20120258676A1 ## CPC - H03H 17/0263: {Rank order filters} - H04L 27/2624: {by soft clipping} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Method and filter for filtering a signal, in which the signal is applied to a delay line having a plurality of taps. Respective weighting coefficients of a windowing function are applied to outputs from the plurality of taps to thereby generate a plurality of weighted outputs. The method comprises repeatedly selecting, for output, whichever of the weighted outputs has the highest value. ## Claims ### Claim 1 A method of filtering a signal comprising: applying the signal to a delay line having a plurality of taps; applying respective weighting coefficients of a windowing function to outputs from the plurality of taps to thereby generate a plurality of weighted outputs; repeatedly selecting the weighted outputs with the highest value; and outputting the weighted outputs with the highest value. ### Claim 2 (depends on 1) The method of claim 1 further comprising filtering the selected outputs over time to thereby generate a filtered signal. ### Claim 3 (depends on 2) The method of claim 2 wherein the signal is a scaling factor which has been generated from a transmit signal and the filtered signal is a filtered scaling factor which is to be applied to the transmit signal. ### Claim 4 (depends on 2) The method of claim 2 wherein filtering the selected outputs over time comprises passing the selected outputs to a further delay line having a further plurality of taps and determining an average of outputs from the further plurality of taps, such that the average of the outputs from the further plurality of taps is used as the filtered signal. ### Claim 5 A method of processing a transmit signal for transmission from a transmitter, the method comprising: generating a scaling factor from the transmit signal using a function which is dependent upon the value of the transmit signal and a threshold value, the threshold value indicating a maximum value to which the transmit signal is to be limited; filtering the scaling factor to create a filtered scaling factor by applying the scaling factor to a delay line having a plurality of taps, applying respective weighting coefficients of a windowing function to outputs from the plurality of taps to thereby generate a plurality of weighted outputs, and repeatedly selecting the weighted outputs with the highest value; and applying the filtered scaling factor to the transmit signal such that the transmit signal does not exceed the maximum value indicated by the threshold value. ### Claim 6 (depends on 5) The method of claim 5 wherein applying the filtered scaling factor to the transmit signal reduces the peak-to-average power ratio of the transmit signal. ### Claim 7 (depends on 5) The method of claim 5 wherein applying the filtered scaling factor to the transmit signal involves a multiplication operation on the transmit signal. ### Claim 8 (depends on 5) The method of claim 5 wherein the function has a first form when the value of the transmit signal is above the threshold value and the function has a second form when the value of the transmit signal is below the threshold value. ### Claim 9 (depends on 5) The method of claim 5 further comprising using a power amplifier to perform power amplification on the transmit signal subsequent to applying the filtered scaling factor to the transmit signal. ### Claim 10 (depends on 9) The method of claim 9 wherein the threshold value is related to a threshold between a first regime of the power amplifier in which the power amplifier operates in a linear region and a second regime of the power amplifier in which the power amplifier operates in a non-linear region. ### Claim 11 (depends on 1) The method of claim 1 wherein the windowing function is a Hamming function or a Kaiser function. ### Claim 12 A filter for filtering a signal comprising: a delay line having a plurality of taps, the delay line being arranged to receive the signal; weighting means for applying respective weighting coefficients of a windowing function to outputs from the plurality of taps to thereby generate a plurality of weighted outputs; and selecting means for repeatedly selecting for output the weighted outputs with the highest value to create selected outputs. ### Claim 13 (depends on 12) The filter of claim 12 further comprising filtering means for filtering the selected outputs over time to thereby generate a filtered signal. ### Claim 14 (depends on 13) The filter of claim 13 wherein the filtering means comprises: a further delay line having a further plurality of taps, the further delay line being arranged to receive the selected outputs; and determining means for determining an average of outputs from the further plurality of taps such that the average of the outputs from the further plurality of taps is the filtered signal. ### Claim 15 (depends on 14) The filter of claim 14 wherein the further delay line and the determining means constitute at least part of a moving average filter. ### Claim 16 (depends on 13) A processing block for processing a transmit signal for transmission from a transmitter, the processing block comprising: generating means for generating a scaling factor from the transmit signal using a function which is dependent upon the value of the transmit signal and a threshold value, the threshold value indicating a maximum value to which the transmit signal is to be limited; the filter of claim 13 for filtering the scaling factor to thereby generate a filtered scaling factor; and applying means for applying the filtered scaling factor to the transmit signal such that the transmit signal does not exceed the maximum value indicated by the threshold value. ### Claim 17 (depends on 16) The processing block of claim 16 wherein the applying means comprises multiplication means for performing a multiplication operation on the transmit signal.