I/Q mismatch correction using transmitter leakage and gain modulation

• US 7,450,919 B1
• Filed: 02/07/2006
• Issued: 11/11/2008
• Est. Priority Date: 02/07/2006
• Status: Expired due to Fees

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Zhang, Pengfei, Chen, Jesse E.
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US11/349,417
• Time in Patent Office: 1,008 Days
• Field of Search: 455/67.11, 455/67.13, 455/67.14, 455/226.1, 455/296, 455/311, 455/312, 455/324
• US Class Current: 455/226.1
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A system and method are provided for compensating for an I/Q mismatch of a receiver in a mobile terminal. In general, the receiver and a transmitter of the mobile terminal are formed on a single substrate. A transmit signal is transmitted via the transmitter. Due to leakage through the substrate, the transmit signal is provided to one or more points in the receiver. One of these points is an input of the amplifier circuitry. A gain of the amplifier circuitry is modulated during reception of the transmit signal such that an amplified signal provided by the amplifier circuitry is offset from the carrier frequency of the transmit signal by a known frequency offset. The amplified signal is downconverted to provide a quadrature output signal. Processing circuitry processes frequency components of the quadrature output signal corresponding to the known frequency offset to determine the I/Q mismatch of the receiver.

Claims

1. A method of compensating for an I/Q mismatch of a receiver comprising:

providing receiver circuitry and associated transmitter circuitry formed on a single substrate;

transmitting a transmit signal;

receiving the transmit signal at an input of amplifier circuitry coupled to an input of the receiver circuitry due to leakage through the substrate from an output of the transmitter circuitry to the input of the amplifier circuitry;

modulating a gain of the amplifier circuitry while receiving the transmit signal such that an output of the amplifier circuitry has a known frequency offset from a carrier frequency of the transmit signal;

downconverting the output of the amplifier circuitry using a quadrature local oscillator signal to provide a quadrature output signal; and

processing the quadrature output signal to determine an I/Q mismatch of the receiver circuitry based on frequency components of the quadrature output signal corresponding to the known frequency offset.

2. The method of claim 1 wherein processing the quadrature output signal comprises determining Fourier coefficients for the frequency components of the quadrature output signal corresponding to the known frequency offset.

3. The method of claim 2 wherein downconverting the output of the amplifier circuitry comprises downconverting the output of the amplifier circuitry to a desired frequency to provide the quadrature output signal, and determining the Fourier coefficients comprises determining Fourier coefficients for a first frequency component corresponding to the desired frequency plus the known frequency offset and determining Fourier coefficients for a second frequency component corresponding to the desired frequency minus the known frequency offset.

4. The method of claim 3 wherein processing the quadrature output signal further comprises determining the I/Q mismatch of the receiver circuitry based on the Fourier coefficients.

5. The method of claim 4 wherein the I/Q mismatch comprises a gain error.

6. The method of claim 5 wherein determining the I/Q mismatch comprises determining the gain error based on the following equation:

$\mathrm{\varepsilon <br><br>}=2·<br><br>\frac{\begin{array}{c}\sqrt{{\left(C_{\mathrm{Pr}}+C_{\mathrm{Mr}}\right)}^2+{\left(-C_{\mathrm{Pi}}+C_{\mathrm{Mi}}\right)}^2}-\\ \sqrt{{\left(C_{\mathrm{Pr}}-C_{\mathrm{Mr}}\right)}^2+{\left(C_{\mathrm{Pi}}+C_{\mathrm{Mi}}\right)}^2}\end{array}}{\begin{array}{c}\sqrt{{\left(C_{\mathrm{Pr}}+C_{\mathrm{Mr}}\right)}^2+{\left(-C_{\mathrm{Pi}}+C_{\mathrm{Mi}}\right)}^2}+\\ \sqrt{{\left(C_{\mathrm{Pr}}-C_{\mathrm{Mr}}\right)}^2+{\left(C_{\mathrm{Pi}}+C_{\mathrm{Mi}}\right)}^2}\end{array}},$

where C_Pr and C_Pi are real and imaginary Fourier coefficients for the first frequency component of the quadrature output signal, and C_Mr and C_Mi are real and imaginary Fourier coefficients for the second frequency component of the quadrature output signal.

7. The method of claim 5 wherein the I/Q mismatch further comprises a quadrature error between in-phase and quadrature-phase components of the quadrature local oscillator signal.

8. The method of claim 7 wherein determining the I/Q mismatch further comprises determining the quadrature error based on the following equation:

$\mathrm{\Delta <br><br>\varphi <br><br>}=\mathrm{Arc}<br><br><br><br>\mathrm{Tan}<br><br>\left[\frac{-C_{\mathrm{Pi}}+C_{\mathrm{Mi}}}{C_{\mathrm{Pr}}+C_{\mathrm{Mr}}}\right]+\mathrm{Arc}<br><br><br><br>\mathrm{Tan}<br><br>\left[\frac{C_{\mathrm{Pi}}+C_{\mathrm{Mi}}}{C_{\mathrm{Pr}}-C_{\mathrm{Mr}}}\right],$

where C_Pr and C_Pi are real and imaginary Fourier coefficients for the first frequency component of the quadrature output signal, and C_Mr and C_Mi are real and imaginary Fourier coefficients for the second frequency component of the quadrature output signal.

9. The method of claim 7 wherein processing the quadrature output signal further comprises determining a phase offset between the carrier frequency and a frequency of the quadrature local oscillator signal based on the Fourier coefficients.

10. The method of claim 1 further comprising determining a distortion matrix defining a distortion of the receiver circuitry based on the I/Q mismatch.

11. The method of claim 1 further comprising providing a correction matrix for compensating for the I/Q mismatch of the receiver circuitry based on the I/Q mismatch.

12. The method of claim 1 further comprising post-distorting subsequent output signals from the receiver circuitry based on the I/Q mismatch, thereby compensating for the I/Q mismatch of the receiver circuitry.

13. The method of claim 1 further comprising activating both the receiver circuitry and the transmitter circuitry prior to transmitting the transmit signal.

14. A system for compensating for an I/Q mismatch of a receiver comprising:

a) receiver circuitry comprising;

i) amplifier circuitry having a controllable gain; and

ii) downconversion circuitry coupled to an output of the amplifier circuitry and adapted to downconvert an amplified signal from the amplifier circuitry using a quadrature local oscillator signal to provide a quadrature output signal;

b) transmitter circuitry, wherein the receiver circuitry and the transmitter circuitry are formed on a single substrate; and

c) processing circuitry adapted to;

i) transmit a transmit signal via the transmitter circuitry such that the transmit signal is received at an input of amplifier circuitry forming an input of the receiver circuitry due to leakage through the substrate from an output of the transmitter circuitry to the input of the amplifier circuitry;

ii) modulate the controllable gain of the amplifier circuitry while the receiver circuitry is receiving the transmit signal such that the amplified signal output by the amplifier circuitry has a known frequency offset from a carrier frequency of the transmit signal and the quadrature output signal includes frequency components corresponding to the known frequency offset; and

iii) process the quadrature output signal to determine an I/Q mismatch of the receiver circuitry based on the frequency components of the quadrature output signal at the known frequency offset.

15. The system of claim 14 wherein the processing circuitry is further adapted to process the quadrature output signal to determine the I/Q mismatch of the receiver circuitry by determining Fourier coefficients for the frequency components of the quadrature output signal corresponding to the known frequency offset.

16. The system of claim 15 wherein the downconversion circuitry is further adapted to downconvert the amplified signal to a desired frequency to provide the quadrature output signal, and the processing circuitry is further adapted to determine the Fourier coefficients by determining Fourier coefficients for a first frequency component corresponding to the desired frequency plus the known frequency offset and determining Fourier coefficients for a second frequency component corresponding to the desired frequency minus the known frequency offset.

17. The system of claim 16 wherein the processing circuitry is further adapted to determine the I/Q mismatch of the receiver circuitry based on the Fourier coefficients.

18. The system of claim 14 wherein the processing circuitry is further adapted to determine a distortion matrix defining a distortion of the receiver circuitry based on the I/Q mismatch of the receiver circuitry.

19. The system of claim 14 wherein the processing circuitry is further adapted to provide a correction matrix based on the I/Q mismatch of the receiver circuitry.

20. The system of claim 14 wherein the processing circuitry is further adapted to post-distort subsequent output signals from the receiver circuitry based on the I/Q mismatch, thereby compensating for the I/Q mismatch of the receiver circuitry.