# US 9,438,177 B2 · Pre-distortion method and associated apparatus and non-transitory machine readable medium > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,177 B2 - Document ID: US9438177B2 - Status: Granted - Kind: B2 - Application number: 14/320,552 - Filed: 2014-06-30 - Published: 2015-01-15 - Granted: 2016-09-06 - Earliest claimed: 2013-07-11 - Assignees: Realtek Semiconductor Corp. - Applicants: Realtek Semiconductor Corp. - Inventors: Yuan-Shuo Chang - Web page: https://patentgrep.com/patent/US9438177B2 ## CPC - H03F 1/3258: {based on polynomial terms} - H03F 1/3247: {using feedback acting on predistortion circuits (H03F1/3264 takes precedence)} - H03F 3/195: in integrated circuits - H03F 3/24: of transmitter output stages - H03F 1/26: Modifications of amplifiers to reduce influence of noise generated by amplifying elements - H03F 1/3241: {using predistortion circuits (H03F1/3211, H03F1/3217 take precedence)} - H03F 2201/3212: Using a control circuit to adjust amplitude and phase of a signal in a signal path - H03F 2201/3224: Predistortion being done for compensating memory effects - H03F 2201/3227: Adaptive predistortion based on amplitude, envelope or power level feedback from the output of the main amplifier - H03F 2201/3233: Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion - H03F: AMPLIFIERS ## Abstract A pre-distortion method includes: receiving an input data; and obtaining a pre-distorted output by inputting the input data into a pre-distortion function, wherein the pre-distortion function is determined according to a power amplifier. A pre-distortion apparatus includes a receiver and a pre-distortion unit. The receiver is utilized for receiving an input data. The pre-distortion unit is utilized for obtaining a pre-distorted output by inputting the input data into a pre-distortion function, wherein the pre-distortion function is determined according to a following power amplifier. A non-transitory machine readable medium stores a program code executed for performing steps of the proposed pre-distortion method. ## Claims ### Claim 1 A pre-distortion method, comprising: receiving an input data; and obtaining a pre-distorted output by inputting the input data into a pre-distortion function, wherein the pre-distortion function is determined according to a power amplifier, comprising: deriving a plurality of coefficients respectively corresponding to a plurality of power levels of the pre-distorted output within a specific power level range by utilizing an adaptive algorithm, wherein the plurality of coefficients includes at least a first coefficient and a second coefficient of a function of the power amplifier. ### Claim 2 (depends on 1) The pre-distortion method of claim 1, wherein the input data is an Orthogonal. Frequency Division Multiplexing (OFDM) data. ### Claim 3 (depends on 1) The pre-distortion method of claim 1, wherein the step of obtaining the pre-distorted output by inputting the input data into the pre-distortion function further comprises: storing a reciprocal of the first coefficient corresponding to each of the plurality of power levels into a first look-up table; storing the second coefficient corresponding to each of the plurality of power levels into a second look-up table; storing a plurality of results obtained by multiplying a square value of each of a plurality of first coefficients with a square value of the corresponding pre-distorted output, respectively, into a third look-up table; and deriving the pre-distortion function according to the first look-up table, the second look-up table and the third look-up table. ### Claim 4 (depends on 1) The pre-distortion method of claim 1, wherein the adaptive algorithm is a least mean square (LMS) algorithm. ### Claim 5 (depends on 1) The pre-distortion method of claim 1, wherein the plurality of power , levels within the specific power level range is assigned according to a non-linear characteristic of the power amplifier. ### Claim 6 (depends on 1) The pre-distortion method of claim 1, wherein the step of deriving the plurality of coefficients corresponding to each of the plurality of power levels of the pre-distorted output within the specific power level range by utilizing the adaptive algorithm comprises: generating a test signal which has a specific power level of the plurality of power levels to a finite impulse response (FIR) filter and the power amplifier; obtaining an FIR filter output at an output terminal of the FIR filter; controlling an output of the power amplifier to be fed back to the output terminal of the FIR filter and to be subtracted from the FIR filter output to obtain an error term; and utilizing the error term to perform the adaptive algorithm to optimize the FIR filter and to obtain a plurality of coefficients corresponding to the specific power level of the pre-distorted output. ### Claim 7 (depends on 6) The pre-distortion method of claim 6, wherein contents of the test signal are pseudo random values. ### Claim 8 (depends on 6) The pre-distortion method of claim 6, wherein the test signal possesses a bandwidth where the power amplifier desires to process. ### Claim 9 (depends on 3) The pre-distortion method of claim 3, wherein the step of deriving the pre-distortion function according to the first look-up table, the second look-up table and the third look-up table comprises: deriving a square value of an output of the pre-distortion function at a previous time unit, and obtaining a specific second coefficient corresponding to the square value of the output of the pre-distortion function at the previous time unit from the second look-up table, and multiplying the specific second coefficient with the output of the pre-distortion function at the previous time unit to produce a first sub-term; subtracting the first sub-term from the input data to produce a second sub-term, and obtaining a specific third coefficient corresponding to a square value of the second sub-term from the third look-up table; and obtaining a reciprocal of the specific first coefficient corresponding to the specific third coefficient from the first look-up table, and multiplying the reciprocal of a specific first coefficient with the second sub-term to produce the pre-distortion function. ### Claim 10 (depends on 9) The pre-distortion method of claim 9, wherein the step of obtaining the specific third coefficient corresponding to the square value of the second sub-term from the third look-up table comprises: finding a result closest to the square value of the second sub-term from the third look-up table; and finding the specific third coefficient corresponding to the result. ### Claim 11 A pre-distortion apparatus, comprising: a receiving unit, arranged for receiving an input data; and a pre-distortion unit, arranged for obtaining a pre-distorted output by inputting the input data into a pre-distortion function, wherein the pre-distortion function is determined according to a following power amplifier, comprises: an adaptive coefficient generating unit, arranged for deriving a plurality of coefficients respectively corresponding to a plurality of power levels of the pre-distorted output within a specific power level range by utilizing an adaptive algorithm, wherein the plurality of coefficients includes at least a first coefficient and a second coefficient of a function of the power amplifier. ### Claim 12 (depends on 11) The pre-distortion apparatus of claim 11, wherein the input data is an Orthogonal Frequency Division Multiplexing (OFDM) data. ### Claim 13 (depends on 11) The pre-distortion apparatus of claim 11, wherein the pre-distortion unit further comprises: a first look-up unit, possessing a first look-up table, wherein the first look-up table stores a reciprocal of the first coefficient corresponding to each of the plurality of power levels into a first look-up table; a second look-up unit, possessing a second look-up table, wherein the second look-up table stores the second coefficient corresponding to each of the plurality of power levels into a second look-up table; a third look-up unit, possessing a third look-up table, wherein the third look-up table stores a plurality of results obtained by multiplying a square value of each of a plurality of first coefficients with a square value of the corresponding pre-distorted output respectively into a third look-up table; and an arithmetic unit, arranged for deriving the pre-distortion function according to the first look-up table, the second look-up table and the third look-up table. ### Claim 14 (depends on 11) The pre-distortion apparatus of claim 11, wherein the adaptive algorithm is a least mean square (LMS) algorithm. ### Claim 15 (depends on 11) The pre-distortion apparatus of claim 11, wherein the plurality of power levels within the specific power level range is assigned according to a non-linear characteristic of the power amplifier. ### Claim 16 (depends on 11) The pre-distortion apparatus of claim 11, wherein the adaptive coefficient generating unit comprises: a test signal generating unit, arranged for generating a test signal which has a specific power level of the plurality of power levels to a finite impulse response (FIR) filter and the power amplifier; the FIR filter, arranged for receiving the test signal and outputting an FIR filter output; an error computing circuit, arranged for controlling an output of the power amplifier to be fed back to the output terminal of the FIR filter and to be subtracted from the FIR filter output to obtain an error term; and an adaptive processing unit, arranged for performing the adaptive algorithm by utilizing the error term to optimize the FIR filter and to obtain a plurality of coefficients corresponding to the specific power level of the pre-distorted output. ### Claim 17 (depends on 16) The pre-distortion apparatus of claim 16, wherein contents of the test signal are pseudo random values. ### Claim 18 (depends on 16) The pre-distortion apparatus of claim 16, wherein the test signal possesses a bandwidth where the power amplifier desires to process. ### Claim 19 (depends on 13) The pre-distortion apparatus of claim 13, wherein the arithmetic unit comprises: a first sub-arithmetic unit, arranged for deriving a square value of an output of the pre-distortion function at a previous time unit, obtaining a specific second coefficient corresponding to the square value of the output of the pre-distortion function at the previous time unit from the second look-up table, and multiplying the specific second coefficient with the output of the pre-distortion function at the previous time unit to produce a first sub-term; a second sub-arithmetic unit, arranged for subtracting the first sub-term from the input data to produce a second sub-term, and obtaining a specific third coefficient corresponding to a square value of the second sub-term from the third look-up table; and a third sub-arithmetic unit, arranged for obtaining a reciprocal of a specific first coefficient corresponding to the specific third coefficient from the first look-up table, and multiplying the reciprocal of the specific first coefficient with the second sub-term to produce the pre-distortion function. ### Claim 20 (depends on 19) The pre-distortion apparatus of claim 19, wherein the second sub-arithmetic unit comprises: a searching unit, arranged for finding a result closest to the square value of the second sub-term from the third look-up table; and an output unit, arranged for outputting the specific third coefficient corresponding to the result. ### Claim 21 A non-transitory machine readable medium storing a program code, wherein when executed by a processor, the program code enables the processor to perform a pre-distortion method, the method comprising: receiving an input data; and obtaining a pre-distorted output by inputting the input data into a pre-distortion function, wherein the pre-distortion function is determined according to a following power amplifier, comprising: deriving a plurality of coefficients respectively corresponding to a plurality of power levels of the pre-distorted output within a specific power level range by utilizing an adaptive algorithm, wherein the plurality of coefficients includes at least a first coefficient and a second coefficient of a function of the power amplifier. ### Claim 22 (depends on 21) The non-transitory machine readable medium of claim 21, wherein the input data is an Orthogonal Frequency Division Multiplexing (OFDM) data. ### Claim 23 (depends on 21) The non-transitory machine readable medium of claim 21, wherein the step of obtaining the pre-distorted output by inputting the input data into the pre-distortion function further comprises: storing a reciprocal of the first coefficient corresponding to each of the plurality of power levels into a first look-up table; storing the second coefficient corresponding to each of the plurality of power levels into a second look-up table; storing a plurality of results obtained by multiplying a square value of each of a plurality of first coefficients with a square value of the corresponding pre-distorted output respectively into a third look-up table; and deriving the pre-distortion function according to the first look-up table, the second look-up table and the third look-up table. ### Claim 24 (depends on 21) The non-transitory machine readable medium of claim 21, wherein the adaptive algorithm is a least mean square (LMS) algorithm. ### Claim 25 (depends on 21) The non-transitory machine readable medium of claim 21, wherein the plurality of power levels within the specific power level range is assigned according to a non-linear characteristic of the power amplifier. ### Claim 26 (depends on 21) The non-transitory machine readable medium of claim 21, wherein the step of deriving the plurality of coefficients of the pre-distorted output corresponding to each of the plurality of power levels within the specific power level range by utilizing the adaptive algorithm comprises: generating a test signal which has a specific power level of the plurality of power levels to a finite impulse response (FIR) filter and the power amplifier; obtaining an FIR filter output at an output terminal of the FIR filter; controlling an output of the power amplifier to be fed back to the output terminal of the FIR filter and to be subtracted from the FIR filter output to obtain an error term; and utilizing the error term to perform the adaptive algorithm to optimize the FIR filter and to obtain a plurality of coefficients corresponding to the specific power level of the pre-distorted output. ### Claim 27 (depends on 26) The non-transitory machine readable medium of claim 26, wherein contents of the test signal are pseudo random values. ### Claim 28 (depends on 26) The non-transitory machine readable medium of claim 26, wherein the test signal possesses a bandwidth where the power amplifier desires to process. ### Claim 29 (depends on 23) The non-transitory machine readable medium of claim 23, wherein the step of deriving the pre-distortion function according to the first look-up table, the second look-up table and the third look-up table comprises: deriving a square value of an output of the pre-distortion function at a previous time unit, obtaining a specific second coefficient corresponding to the square value of the output of the pre-distortion function at the previous time unit from the second look-up table, and multiplying the specific second coefficient with the output of the pre-distortion function at the previous time unit to produce a first sub-term; subtracting the first sub-term from the input data to produce a second sub-term, and obtaining a specific third coefficient corresponding to a square value of the second sub-term from the third look-up table; and obtaining a reciprocal of a specific first coefficient corresponding to the specific third coefficient from the first look-up table, and multiplying the reciprocal of the specific first coefficient with the second sub-term to produce the pre-distortion function. ### Claim 30 (depends on 29) The non-transitory machine readable medium of claim 29, wherein the step of obtaining the specific third coefficient corresponding to the square value of the second sub-term from the third look-up table comprises: finding a result closest to the square value of the second sub-term from the third look-up table; and finding the specific third coefficient corresponding to the result.