# US 10,320,340 B1 · Frequency-shaped digital predistortion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,320,340 B1 - Document ID: US10320340B1 - Status: Granted - Kind: B1 - Application number: 15/868,295 - Filed: 2018-01-11 - Granted: 2019-06-11 - Earliest claimed: 2018-01-11 - Assignees: Analog Devices Global Unlimited Company - Applicants: Analog Devices Global Unlimited Company - Inventors: Patrick Pratt; David Jennings - Web page: https://patentgrep.com/patent/US10320340B1 ## CPC - H03F 1/3247: {using feedback acting on predistortion circuits (H03F1/3264 takes precedence)} - H03F 1/3258: {based on polynomial terms} - H03F 3/245: {with semiconductor devices only} - H03M 1/183: {the feedback signal controlling the gain of an amplifier or attenuator preceding the analogue/digital converter} - H03M 3/50: {Digital/analogue converters using delta-sigma modulation as an intermediate step (digital delta-sigma modulators per se H03M7/3004)} - H03M 7/3004: {Digital delta-sigma modulation} - H04L 25/49: using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels {; Baseband coding techniques specific to data transmission systems (spectral shaping H04L25/03828)} - H03F 2201/3224: Predistortion being done for compensating memory effects - H03F 2201/3233: Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion - H03M 1/70: Automatic control for modifying converter range - H04B 17/104: {of other parameters, e.g. DC offset, delay or propagation times} - H04L 25/03853: {Shaping by digital methods other than look up tables or up/down converters} - H03F: AMPLIFIERS - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04B: TRANSMISSION ## Abstract Various examples are directed to a digital predistortion (DPD) circuit comprising a DPD actuator circuit, a DPD feedback frequency-shaping filter, a basis matrix generator circuit, a basis matrix frequency-shaping filter, and a DPD adaption circuit. The DPD actuator circuit may generate a predistorted signal based at least in part on an input signal and a set of frequency-shaped DPD parameters. The DPD feedback frequency-shaping filter may filter a DPD feedback signal to generate a frequency-shaped DPD feedback signal. A passband of the DPD feedback frequency-shaping filter may include substantially all of a bandwidth of the input signal and exclude a distortion term outside the bandwidth of the input signal. The basis matrix generator may generate a basis matrix based at least in part on a power amplifier feedback signal The basis matrix frequency-shaping filter may generate a frequency-shaped basis matrix based at least in part on the basis matrix. The DPD adaption circuit may be configured to generate the set of frequency-shaped DPD parameters based at least in part on the frequency-shaped basis matrix and the frequency-shaped DPD feedback signal. ## Claims ### Claim 1 A digital predistortion (DPD) circuit with frequency shaping, comprising: a DPD actuator circuit configured to perform operations comprising generating a predistorted signal based at least in part on an input signal and a set of frequency-shaped DPD parameters; and a DPD feedback frequency-shaping filter configured to perform operations comprising filtering a DPD feedback signal to generate a frequency-shaped DPD feedback signal; a frequency-shaped feedback parameter circuit configured to perform operations comprising generating feedback parameter data based at least in part on a power amplifier feedback signal; a feedback parameter frequency-shaping filter configured to generate a frequency-shaped feedback parameter based at least in part on the feedback parameter; and a DPD adaption circuit configured to perform operations comprising generating a revised set of frequency-shaped DPD parameters based at least in part on the frequency-shaped feedback parameter and the frequency-shaped DPD feedback signal. ### Claim 2 (depends on 1) The DPD circuit of claim 1, wherein a passband of the DPD feedback frequency-shaping filter comprises substantially all of a bandwidth of the input signal and excludes a distortion term outside the bandwidth of the input signal. ### Claim 3 (depends on 1) The DPD circuit of claim 1, wherein a passband of the feedback parameter frequency-shaping filter is about equal to the passband of the DPD feedback frequency-shaping filter. ### Claim 4 (depends on 1) The DPD circuit of claim 1, wherein a gain of the DPD feedback frequency-shaping filter decreases at a tilt slope between a first frequency and a second frequency that is higher than the first frequency, and wherein a gain of the feedback parameter frequency-shaping filter also decreases at the tilt slope between the first frequency and the second frequency. ### Claim 5 (depends on 1) The DPD circuit of claim 1, wherein the feedback parameter frequency-shaping filter is further configured to perform operations comprising applying a group delay to the feedback parameter. ### Claim 6 (depends on 1) The DPD circuit of claim 1, further comprising: an amplifier inverse model circuit configured to perform operations comprising generating an estimated predistorted signal based at least in part on the frequency-shaped feedback parameter; and a summer circuit configured to perform operations comprising generating the DPD feedback signal, wherein the DPD feedback signal is based at least in part on a difference between the estimated predistorted signal and the predistorted signal. ### Claim 7 (depends on 6) The DPD circuit of claim 6, further comprising an equalizer filter configured to perform operations comprising generating an equalized predistorted input, wherein a gain of the equalizer filter decreases between a first frequency in a bandwidth of the input signal and a second frequency in the bandwidth of the input signal. ### Claim 8 (depends on 6) The DPD circuit of claim 6, wherein generating the set of frequency-shaped DPD parameters comprises minimizing a least squares cost function of the amplifier inverse model. ### Claim 9 (depends on 1) The DPD circuit of claim 1, further comprising: a digital-to-analog converter (DAC) configured to perform operations comprising generating an analog predistorted signal based at least in part on the predistorted signal; an uptilt amplifier configured to perform operations comprising generating an uptilted predistorted signal, wherein the uptilt amplifier has a frequency-dependent gain; and a power amplifier configured to perform operations comprising generating an amplified signal based at least in part on the uptilted predistorted signal. ### Claim 10 A method for performing digital predistortion (DPD) with frequency-shaping, comprising: generating a predistorted signal based at least in part on an input signal and a set of frequency-shaped DPD parameters, generating a frequency-shaped DPD feedback signal based at least in part on a predistorted signal; generating a feedback parameter based at least in part on a power amplifier feedback signal; generating a frequency-shaped feedback parameter based at least in part on the feedback parameter; and generating a revised set of frequency-shaped DPD parameters based at least in part on the frequency-shaped feedback parameter and the frequency-shaped DPD feedback signal. ### Claim 11 (depends on 10) The method of claim 10, wherein a bandwidth of the frequency-shaped DPD feedback signal is about equal to a bandwidth of the input signal and excludes a distortion term outside the bandwidth of the input signal. ### Claim 12 (depends on 10) The method of claim 10, wherein the generating of the frequency-shaped DPD feedback signal is performed by a DPD feedback frequency-shaping filter having a first passband, and wherein the generating of the frequency-shaped feedback parameter is performed by a feedback parameter frequency-shaping filter having a second passband that is about equal to the first passband. ### Claim 13 (depends on 10) The method of claim 10, wherein generating the frequency-shaped DPD feedback signal comprises applying a gain that decreases at a tilt slope between a first frequency and a second frequency that is higher than the first frequency. ### Claim 14 (depends on 10) The method of claim 10, wherein generating the frequency-shaped feedback parameter comprises applying a group delay to the feedback parameter. ### Claim 15 (depends on 10) The method of claim 10, further comprising: generating an estimated predistorted signal based at least in part on the frequency-shaped feedback parameter; and generating the DPD feedback signal, wherein the DPD feedback signal is based at least in part on a difference between the estimated predistorted signal and the predistorted signal. ### Claim 16 (depends on 15) The method of claim 15, generating, by an equalizer filter, an equalized predistorted input, wherein a gain of the equalizer filter decreases between a first frequency in a bandwidth of the input signal a second frequency in the bandwidth of the input signal. ### Claim 17 (depends on 15) The method of claim 15, wherein generating the estimated predistorted signal comprises applying an amplifier inverse model, and wherein generating the revised set of frequency-shaped DPD parameters comprises minimizing a least squares cost function of the amplifier inverse model. ### Claim 18 (depends on 10) The method of claim 10, further comprising: generating, by a digital-to-annalog circuit, an analog predistorted signal based at least in part on the predistorted signal; and generating, by an uptilt amplifier, an uptilted predistorted signal, wherein the uptilt amplifier has a frequency-dependent gain. ### Claim 19 A system for performing digital predistortion (DPD) with frequency-shaping, comprising: means for generating a predistorted signal based at least in part on an input signal and a set of frequency-shaped DPD parameters; and means for generating a frequency-shaped DPD feedback signal; means for generating a feedback parameter based at least in part on a power amplifier feedback signal; means for generating a frequency-shaped feedback parameter based at least in part on the feedback parameter; and means for generating a revised set of frequency-shaped DPD parameters based at least in part on the frequency-shaped feedback parameter and the frequency-shaped DPD feedback signal. ### Claim 20 (depends on 19) The system of claim 19, wherein a passband for the generating of the frequency-shaped feedback parameter is about equal to a passband for generating the frequency-shaped DPD feedback signal. ### Claim 21 (depends on 1) The DPD circuit of claim 1, wherein the feedback parameter comprises a basis matrix. ### Claim 22 (depends on 10) The method of claim 10, wherein the feedback parameter comprises a basis matrix. ### Claim 23 (depends on 19) The system of claim 19, wherein the feedback parameter comprises a basis matrix.