Digital pre-emphasis quadrature imbalance compensating filter

Patent metadata

Field	Value
Publication number	US-2017346509-A1
Application number	US-201615168552-A
Country	US
Kind code	A1
Filing date	May 31, 2016
Priority date	May 31, 2016
Publication date	Nov 30, 2017
Grant date	—

Abstract

A transmitter includes a pre-emphasis digital filter configured to filter a series of respective digital input data samples according to a plurality of coefficients to generate a series of respective corresponding pre-emphasized data samples. The transmitter also includes a digital-to-analog converter (DAC) configured to sample the series of pre-emphasized data samples to generate an analog signal and an analog filter configured to filter the analog signal to generate a filtered signal. Estimator circuitry is configured to input a pre-emphasized data sample; input a corresponding sample of the filtered signal; and calculate the plurality of coefficients based on the sample of the filtered signal and the pre-emphasized data sample.

First claim

1 . A transmitter comprising:
a pre-emphasis digital filter configured to filter a series of respective digital input data samples according to a plurality of coefficients to generate a series of respective corresponding pre-emphasized data samples; a digital-to-analog converter (DAC) configured to sample the series of pre-emphasized data samples to generate an analog signal; an analog filter configured to filter the analog signal to generate a filtered signal; and estimator circuitry configured to:
input a pre-emphasized data sample;
input a corresponding sample of the filtered signal; and
calculate the plurality of coefficients based on the sample of the filtered signal and the pre-emphasized data sample.

2 . The transmitter of claim 1 , wherein the estimator circuitry is configured to calculate the plurality of coefficients by solving for a filter function that, when applied to the pre-emphasized data sample, will bring the filtered signal into equivalence with the pre-emphasized data sample.

3 . The transmitter of claim 1 , comprising an observation path configured to feedback a sample of the filtered signal to the estimator circuitry, wherein the observation path comprises an analog-to-digital converter (ADC) that inputs the filtered signal and generates the sample of the filtered signal.

4 . The transmitter of claim 1 , comprising an observation path configured to feedback a sample of the filtered signal to the estimator circuitry, wherein the observation path comprises:
an up-converter configured to convert the filtered signal from a baseband frequency to radio frequency (RF) to generate an RF filtered signal for transmission by the transmitter; a down-converter configured to convert the RF filtered signal back to the baseband frequency to generate a filtered baseband signal; and an analog-to-digital converter (ADC) configured to:
generate a sample of the filtered baseband signal; and
feedback the sample to the estimator circuitry.

5 . The transmitter of claim 1 , wherein the pre-emphasis digital filter comprises:
leakage compensation circuitry configured to generate, for each input data sample, a leakage compensated I component and a leakage compensated Q component; and skew and bandwidth compensation circuitry configured to generate, for each input data sample, a skew and bandwidth compensated I component and a skew and bandwidth compensated Q component; wherein the pre-emphasis digital filter is configured to: add an I component of the input data sample to the leakage compensated I component and the skew and bandwidth compensated I component to generate a pre-emphasized I component; and add a Q component of the input data sample to the leakage compensated Q component and the skew and bandwidth compensated Q component to generate a pre-emphasized Q component; combine the pre-emphasized I component with the pre-emphasized Q component to generate the pre-emphasized data sample.

6 . The transmitter of claim 5 , wherein the leakage compensation circuitry is configured to:
add a first portion of a Q component of an input data sample to a second portion of an I component of the input data sample to generate the leakage compensated I component, wherein the first portion and second portion are controlled by a first coefficient and a second coefficient, respectively, of the plurality of coefficients; and add a third portion of the I component of the input data sample to a fourth portion of the Q component of the input data sample to generate the leakage compensated Q component, wherein the third portion and fourth portion are controlled by a third coefficient and a fourth coefficient, respectively, of the plurality of coefficients.

7 . The transmitter of claim 5 , wherein the skew and bandwidth compensation circuitry configured to:
add a fifth portion of an I component of the input data sample to a sixth portion of an I component of an immediately prior input data sample to generate a first summed I component, wherein the fifth portion and sixth portion are controlled by a fifth coefficient and a sixth coefficient, respectively, of the plurality of coefficients; add a seventh portion of a Q component of the input data sample to an eighth portion of a Q component of an immediately prior input data sample to generate a first summed Q component, wherein the seventh portion and eighth portion are controlled by a seventh coefficient and an eighth coefficient, respectively, of the plurality of coefficients; add the first summed I component and the first summed Q component to generate the skew and bandwidth compensated I component; add a ninth portion of an I component of the input data sample to a tenth portion of an I component of an immediately prior input data sample to generate a second summed I component, wherein the ninth portion and tenth portion are controlled by a ninth coefficient and a tenth coefficient, respectively, of the plurality of coefficients; add an eleventh portion of a Q component of the input data signal to a twelfth portion of a Q component of an immediately prior input data sample signal to generate a second summed Q component, wherein the eleventh portion and twelfth portion are controlled by an eleventh coefficient and a twelfth coefficient, respectively, of the plurality of coefficients; add the second summed I component and the second summed Q component to generate the skew and bandwidth compensated Q component.

8 . The transmitter of claim 1 , comprising monitor circuitry configured to:
input the sample of the filtered signal; input a corresponding input data sample; compare the sample of the filtered signal to the input data sample; determine if a difference between the sample of the filtered signal and the input data sample exceeds a threshold; and trigger the estimator circuitry to re-calculate the coefficient based on present pre-emphasized data samples and present samples of the filtered signal when the difference exceeds the threshold.

9 . The transmitter of claim 1 wherein the transmitter is configured to transmit in a selected one of two or more bandwidths, and wherein a bandwidth of the analog filter is selected as a narrowest bandwidth of the two or more bandwidths.

10 . A method comprising:
filtering a series of respective digital input data samples according to a plurality of coefficients to generate a series of respective corresponding pre-emphasized data samples; sampling the series of pre-emphasized data samples to generate an analog signal; filtering the analog signal to generate a filtered signal; inputting a pre-emphasized data sample; inputting a corresponding sample of the filtered signal; and calculating the plurality of coefficients based on the sample of the filtered signal and the pre-emphasized data sample.

11 . The method of claim 10 comprising calculating the plurality of coefficients by solving for a filter function that, when applied to the pre-emphasized data sample, will bring the filtered signal into equivalence with the pre-emphasized data sample.

12 . The method of claim 10 , comprising: generating the sample of the filtered signal by inputting the filtered signal to an ADC.

13 . The method of claim 10 , comprising:
converting the filtered signal from a baseband frequency to radio frequency (RF) to generate an RF filtered signal for transmission by a transmitter; converting the RF filtered signal back to the baseband frequency to generate a filtered baseband signal; and inputting the filtered baseband signal to an ADC to generate the sample of the filtered signal; and providing the sample of the filtered baseband signal to the esti

Assignees

• Intel Ip Corp

Inventors

• Sulimarski Avi
• Avraham Oren E

Classifications

• H04B1/0475 Primary

  with means for limiting noise, interference or distortion (H04B1/0483 takes precedence) · CPC title

• H04B1/04 Primary

  Circuits · CPC title

• H04B17/18 Primary

  Monitoring during normal operation · CPC title

• H04B2001/0425

  with linearisation using predistortion · CPC title

• H04B17/11

  for calibration · CPC title