# US 11,444,819 B1 · Adaptive digital receiver path linearizer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,444,819 B1 - Document ID: US11444819B1 - Status: Granted - Kind: B1 - Application number: 17/827,730 - Filed: 2022-05-29 - Granted: 2022-09-13 - Earliest claimed: 2022-05-29 - Assignees: IQ-Analog Corporation - Applicants: IQ-Analog Corporation - Inventors: Mikko Waltari - Web page: https://patentgrep.com/patent/US11444819B1 ## CPC - H04L 27/368: {adaptive predistortion} - H03F 1/3223: {using feed-forward (H03F1/3211 takes precedence)} - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H04W 88/02: Terminal devices - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H03F: AMPLIFIERS - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A system and method for digital receiver linearization is provided. An input digital signal is accepted with a plurality of spectral components. The input digital signal may be either a radio frequency (RF) digital signal or a baseband digital signal. Nonlinear distortion is created in response to the input digital signal. As the result of a corrected input digital signal, a primary baseband signal is created with real (I) and imaginary quadrature (Q) components. In response to the nonlinear distortion, auxiliary baseband signals are created with real (IAUX) and imaginary quadrature (QAUX) components. The primary baseband signal is compared to the auxiliary baseband signals to supply complex amplitude correction coefficients. The complex amplitude correction coefficients are used to modify the nonlinear distortion, and the modified nonlinear distortion is subtracted from the input digital signal to supply the corrected input digital signal. ## Claims ### Claim 1 An adaptive digital receiver linearizer comprising: a distorter having an input to accept a radio frequency (RF) input digital signal with a plurality of spectral components and an output to supply nonlinear distortion; a digital down converter (DDC) having an input to accept a corrected RF input digital signal and an output to supply a primary baseband signal with real (I) and imaginary quadrature (Q) components; an auxiliary DDC having an input to accept the nonlinear distortion and an output to supply auxiliary baseband signals with real (IAUX) and imaginary quadrature (QAUX) components; a correlator having an input to accept the primary baseband signal and the auxiliary baseband signals, and an output to supply complex amplitude correction coefficients, including real (ICOR) and imaginary quadrature (QCOR) correction coefficients for the nonlinear distortion; and, a correction network having an input to accept the complex amplitude correction coefficients, an input to accept the nonlinear distortion, an input to accept the input digital signal, and an output to supply the corrected RF input digital signal. ### Claim 2 (depends on 1) The linearizer of claim 1 wherein the correction network comprises: a multiplier having an input to accept the complex amplitude correction coefficients, an input to accept the nonlinear distortion, and an output to supply adjusted nonlinear distortion components that have been adjusted for amplitude and phase; a summer having an input to accept the adjusted nonlinear distortion components, the summer combining the adjusted nonlinear distortion components to supply corrections at an output; and, an adder having an input to accept the RF input digital signal and input to accept corrections, the adder subtracting the accepted corrections from the RF input digital signal to supply the corrected RF input digital signal at an output. ### Claim 3 (depends on 2) The system of claim 2 wherein the distorter supplies real nonlinear distortion components (IDIS) and imaginary quadrature nonlinear distortion components (QDIS); wherein the multiplier adjusts the amplitude of the real nonlinear distortion components (IDIS) in response to the real (Icor) correction coefficients and adjusts the amplitude of the imaginary quadrature nonlinear distortion components (QDIS) in response to the imaginary (Qcor) correction coefficients, to respectively supply amplitude adjusted real nonlinear distortion components (IADJ) and amplitude adjusted imaginary quadrature nonlinear distortion components (QADJ); wherein the summer combines the amplitude adjusted real nonlinear distortion components (IADJ) and combines the amplitude adjusted imaginary quadrature nonlinear distortion components (IADJ) to respectively supply combined amplitude adjusted real correction signal (ICOMB) and a combined amplitude adjusted imaginary quadrature correction signal (QCOMB); and, wherein the adder subtracts the combined amplitude adjusted real correction signal (ICOMB) from the RF input digital signal. ### Claim 4 (depends on 3) The system of claim 3 wherein the combined amplitude adjusted imaginary quadrature correction signal (QCOMB) is supplied to an input of the DDC. ### Claim 5 (depends on 3) The system of claim 3 wherein the auxiliary DDC sequentially supplies N auxiliary baseband signals, (IAUX1 through IAUXN) and (QAUX1 through QAUXN), corresponding to N nonlinear distortion components, where N is an integer greater than 1; wherein the correlator sequentially supplies N complex amplitude correction coefficients; wherein the summer combines N amplitude adjusted real nonlinear distortion components and combines the N amplitude adjusted imaginary quadrature nonlinear distortion components to supply the combined amplitude adjusted real correction signal (ICOMB) and the combined amplitude adjusted imaginary quadrature correction signal (QCOMB). ### Claim 6 (depends on 3) The system of claim 3 wherein the auxiliary DDC comprises N parallel-connected auxiliary DDCs to supply N corresponding nonlinear distortion components, (IAUX1 through IAUXN) and (QAUX1 through QAUXN), where N is an integer greater than 1; and, wherein the correlator comprises N parallel-connected correlators to supply N complex amplitude correction coefficients. ### Claim 7 (depends on 3) The system of claim 3 wherein the distorter, for each component in the input digital signal, supplies second-order nonlinear distortion signals and third-order nonlinear distortion signals. ### Claim 8 (depends on 3) The system of claim 3 wherein the distorter, for each component in the input digital signal, supplies nth-order nonlinear distortion signals, where n is an integer greater than 1. ### Claim 9 (depends on 3) The system of claim 3 wherein the distorter comprises: an IQ generator having an input to accept a distorter input digital signal, and an output to supply a first-order real signal (I1) and a first-order imaginary quadrature signal (Q1); a second-order generator having an input to accept I1 and Q1 and an output to supply real second order products I2A and I2B, and an imaginary quadrature second order product Q2B, where “A” and “B” represent, respectively, lower and upper sidebands of a signal in the frequency domain; and, a third-order generator having an input to accept I1, Q1, I2B, and Q2B, and an output to supply real third-order products I3A and I3B, and imaginary third-order quadrature products Q3A and Q3B. ### Claim 10 (depends on 9) The system of claim 9 wherein the second-order generator comprises: a first mixer having inputs to accept I1 and Q1, and an output to supply a first product; a 2× gain block having an input to accept the first product and an output to supply a second-order imaginary quadrature component Q2B; a second mixer having inputs to accept I1 and an output to supply a second product ((I1)2); a third mixer having inputs to accept Q1 and an output to supply a third product ((Q1)2); a first adder having inputs to subtract the third product from the second product, and an output to supply I2B; and, a second adder having inputs to accept the second and third products and an output to supply I2A. ### Claim 11 (depends on 9) The system of claim 9 wherein the third-order generator comprises: a fourth mixer having inputs to accept I1 and I2B, and an output to supply a fourth product; a fifth mixer having inputs to accept Q1 and I2B, and an output to supply a fifth product; a sixth mixer having inputs to accept I1 and Q2B, and an output to supply a sixth product; a seventh mixer having inputs to accept Q1 and Q2B, and an output to supply a seventh product; a third adder having inputs to subtract the seventh product from the fourth product, and an output to supply I3A; a first calculator having an input to accept I1, and multiplying I1 by a constant 1/sqrt(3) to supply an eighth product at an output; a second calculator having an input to accept Q1, and multiplying Q1 by the constant 1/sqrt(3) to supply a ninth product at an output; a fourth adder having inputs to subtract the eighth product from the seventh product and the fourth product, and an output to supply I3B; a fifth adder having inputs to accept a negative sixth product and a negative fifth product, and an output to supply Q3A; and, a sixth adder having inputs to add the fifth product, a negative sixth product, and a negative ninth product, and an output to supply Q3B. ### Claim 12 (depends on 9) The system of claim 9 wherein the IQ generator comprises: a delay unit to accept the distorter input digital signal and an output to supply I1; and, a Hilbert transformer having an input to accept the distorter input digital signal and an output to supply Q1. ### Claim 13 An adaptive digital baseband receiver linearizer comprising: distorter having an input to accept a baseband input digital signal with real and imaginary components, and with a plurality of spectral components, and an output to supply nonlinear distortion; a down-sampler comprising a lowpass frequency filter and a decimation filter, having an input to accept a corrected baseband input digital signal and an output to supply a primary baseband signal with real (I) and imaginary quadrature (Q) components; an auxiliary down-sampler having an input to accept the nonlinear distortion and an output to supply auxiliary baseband signals with real (IAUX) and imaginary quadrature (QAUX) components; a correlator having an input to accept the primary baseband signal and the auxiliary baseband signals, and an output to supply complex amplitude correction coefficients, including real (ICOR) and imaginary quadrature (QCOR) correction coefficients for the nonlinear distortion; and, a correction network having an input to accept the complex amplitude correction coefficients, an input to accept the nonlinear distortion, an input to accept the baseband input digital signal, and an output to supply the corrected baseband input digital signal. ### Claim 14 (depends on 13) The linearizer of claim 13 wherein the correction network comprises: a multiplier having an input to accept the complex amplitude correction coefficients, an input to accept the nonlinear distortion, and an output to supply adjusted nonlinear distortion components that have been adjusted for amplitude and phase; a summer having an input to accept the adjusted nonlinear distortion components, the summer combining the adjusted nonlinear distortion components to supply corrections at an output; and, an adder having an input to accept the baseband input digital signal and input to accept corrections, the adder subtracting the accepted corrections from the baseband input digital signal to supply the corrected baseband input digital signal at an output. ### Claim 15 (depends on 14) The system of claim 14 wherein the distorter supplies real nonlinear distortion components (IDIS) and imaginary quadrature nonlinear distortion components (QDIS); wherein the multiplier adjusts the amplitude of the real nonlinear distortion components (IDIS) in response to the real (Icor) correction coefficients and adjusts the amplitude of the imaginary quadrature nonlinear distortion components (QDIS) in response to the imaginary (Qcor) correction coefficients, to respectively supply amplitude adjusted real nonlinear distortion components (IADJ) and amplitude adjusted imaginary quadrature nonlinear distortion components (QADJ); wherein the summer combines the amplitude adjusted real nonlinear distortion components (IADJ) and combines the amplitude adjusted imaginary quadrature nonlinear distortion components (IADJ) to respectively supply combined amplitude adjusted real correction signal (ICOMB) and a combined amplitude adjusted imaginary quadrature correction signal (QCOMB); and, wherein the adder subtracts the combined amplitude adjusted real correction signal (ICOMB) and the combined amplitude adjusted imaginary quadrature correction signal (QCOMB) from the baseband input digital signal. ### Claim 16 A method for digital receiver linearization, the method comprising: accepting an input digital signal with a plurality of spectral components; creating nonlinear distortion in response to the input digital signal; in response to a corrected input digital signal, creating a primary baseband signal with real (I) and imaginary quadrature (Q) components; in response to the nonlinear distortion, creating auxiliary baseband signals with real (IAUX) and imaginary quadrature (QAUX) components; in response to comparing the primary baseband signal to the auxiliary baseband signals, supplying complex amplitude correction coefficients; using the complex amplitude correction coefficients to modify the nonlinear distortion; and, subtracting the modified nonlinear distortion from the input digital signal to supply the corrected input digital signal. ### Claim 17 (depends on 16) The method of claim 16 wherein using the complex amplitude correction network to modify the nonlinear distortion includes: multiplying the nonlinear distortion by the complex amplitude correction coefficients to supply adjusted nonlinear distortion components that have been adjusted for amplitude and phase; combining the adjusted nonlinear distortion components to supply corrections at an output; and, wherein subtracting the modified nonlinear distortion from the input digital signal includes subtracting accepted corrections from the input digital signal to supply the corrected input digital signal at an output. ### Claim 18 (depends on 17) The method of claim 17 wherein creating nonlinear distortion includes creating real nonlinear distortion components (IDIS) and imaginary quadrature nonlinear distortion components (QDIS); wherein multiplying the complex amplitude correction coefficients by the nonlinear distortion includes adjusting the amplitude of the real nonlinear distortion components (IDIS) in response to the real (Icor) correction coefficients and adjusting the amplitude of the imaginary quadrature nonlinear distortion components (QDIS) in response to the imaginary (Qcor) correction coefficients, to respectively supply amplitude adjusted real nonlinear distortion components (IADJ) and amplitude adjusted imaginary quadrature nonlinear distortion components (QADJ); wherein combining the adjusted nonlinear distortion components includes combining the amplitude adjusted real nonlinear distortion components (IADJ) and combining the amplitude adjusted imaginary quadrature nonlinear distortion components CO to respectively supply combined amplitude adjusted real correction signal (ICOMB) and a combined amplitude adjusted imaginary quadrature correction signal (QCOMB); and, wherein subtracting accepted corrections from the input digital signal includes subtracting the combined amplitude adjusted real correction signal (ICOMB) from the input digital signal. ### Claim 19 (depends on 18) The method of claim 18 creating a primary baseband signal includes creating the primary baseband signal at least partially in response to the combined amplitude adjusted imaginary quadrature correction signal (QCOMB). ### Claim 20 (depends on 16) The method of claim 16 wherein accepting the input digital signal includes a method selected from the group consisting of using a digital down converter to accept a radio frequency (RF) digital signal or using a down-sampler to accept a baseband digital signal with real and imaginary quadrature components. ### Claim 21 A signal distortion system comprising: an IQ generator having an input to accept an input digital signal, and an output to supply a first-order real signal (I1) and a first-order imaginary quadrature signal (Q1); a second-order generator having an input to accept I1 and Q1 and an output to supply real second order products I2A and I2B, and an imaginary quadrature second order product Q2B, where “A” and “B” represent, respectively, lower and upper sidebands of a signal in the frequency domain; and, a third order generator having an input to accept I1, Q1, I2B, and Q2B, and an output to supply real third-order products I3A and I3B, and imaginary third-order quadrature products Q3A and Q3B. ### Claim 22 (depends on 21) The system of claim 21 wherein the second-order generator comprises: a first mixer having inputs to accept I1 and Q1, and an output to supply a first product; a 2× gain block having an input to accept the first product and an output to supply a second-order imaginary quadrature component Q2B; a second mixer having inputs to accept I1 and an output to supply a second product ((I1)2); a third mixer having inputs to accept Q1 and an output to supply a third product ((Q1)2); a first adder having inputs to subtract the third product from the second product, and an output to supply I2B; and, a second adder having inputs to accept the second and third products and an output to supply I2A. ### Claim 23 (depends on 21) The system of claim 21 wherein the third-order generator comprises: a fourth mixer having inputs to accept I1 and I2B, and an output to supply a fourth product; a fifth mixer having inputs to accept Q1 and I2B, and an output to supply a fifth product; a sixth mixer having inputs to accept I1 and Q2B, and an output to supply a sixth product; a seventh mixer having inputs to accept Q1 and Q2B, and an output to supply a seventh product; a third adder having inputs to subtract the seventh product from the fourth product, and an output to supply I3A; a first calculator having an input to accept I1, and multiplying I1 by a constant 1/sqrt(3) to supply an eighth product at an output; a second calculator having an input to accept Q1, and multiplying Q1 by the constant 1/sqrt(3) to supply a ninth product at an output; a fourth adder having inputs to subtract the eighth product from the seventh product and the fourth product, and an output to supply I3B; a fifth adder having inputs to accept a negative sixth product and a negative fifth product, and an output to supply Q3A; and, a sixth adder having inputs to add the fifth product, a negative sixth product, and a negative ninth product, and an output to supply Q3B. ### Claim 24 (depends on 21) The system of claim 21 wherein the IQ generator comprises: a delay unit to accept the input digital signal and an output to supply I1; and, a Hilbert transformer having an input to accept the input digital signal and an output to supply Q1.