Method and apparatus for I/Q mismatch calibration in a receiver

• US 20050047536A1
• Filed: 09/02/2003
• Published: 03/03/2005
• Est. Priority Date: 09/02/2003
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Wu, Kuo-Ming, Chiu, Mao-Ching, Cheng, Jui-Hsi
• Granted Patent: US 7,174,146 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/3863 Compensation for quadrature error in the received signal

Abstract

A method for I/Q mismatch calibration of a receiver having an I/Q correction module with correction parameters, comprising the steps of generating a test signal containing a single tone waveform with frequency of a carrier frequency plus a predetermined frequency, applying I/Q demodulation to reduce the central frequency of the test signal and outputting a demodulated signal, converting the demodulated signal to a digital signal, obtaining measures of the digital signal respectively indicative of the frequency response of the digital signal at the plus and minus predetermined frequencies, and calculating the set of the correction parameters for the I/Q correction module based on the measures.

Claims

1. A method for I/Q mismatch calibration of a receiver having an I/Q correction module which performs x_o[n]=A_p·

x_i[n]+B_p·

x*_i*[n] where x_i[n] and x_o[n] respectively represent the input and output signal of the I/Q correction module, the superscript * refers to a complex conjugate, and A_p and B_p are correction parameters, comprising the following steps;

generating a test signal x(t) containing a single tone waveform with frequency of (f_c+f_T) Hz, where f_c and f_T are real numbers;

applying I/Q demodulation to reduce the central frequency of the test signal x(t) by f_c Hz and output a demodulated signal x_dem(t);

converting the demodulated signal x_dem(t) to a digital signal x_dem[n];

obtaining measures U₁ and U₂ of the digital signal x_dem[b] where U₁ and U₂ are values indicative of the frequency response of x_dem(t) at frequency +f_T Hz and −

f_T Hz, respectively; and

calculating the set of the correction parameters A_p and B_p for the I/Q correction module based on the measures U₁ and U₂.

2. The method for I/Q mismatch calibration of a receiver as claimed in claim 1, the measure U₁ and U₂ are obtained from the coefficients of the Fourier transformation of the x_dem[n] corresponding to the frequency +f_T Hz and −

f_T Hz.

3. The method for I/Q mismatch calibration of a receiver as claimed in claim 1, wherein the test signal x(t)=cos(2π

(f_c+f_T)).

4. The method for I/Q mismatch calibration of a receiver as claimed in claim 1, wherein the set of correction parameters (A_p,B_p) are obtained by

$\hspace{1em}$

{ A p = R + j ⁢

 

⁢

α

⁢

 

⁢

S B p = - α

⁢

 

⁢

R - j ⁢

 

⁢

S

where α

, R, and S are obtained based on U₁ and U₂.

5. The method for I/Q mismatch calibration of a receiver as claimed in claim 4, wherein α

, R, and S are obtained based on

H=real(U₁·

U₂)
I=imag(U₁·

U₂),

and

G=|U₁|²+|U₂|².

6. The method for I/Q mismatch calibration of a receiver as claimed in claim 4.1, wherein α

, R, and S are obtained by

$\mathrm{\alpha <br><br>}=\frac{H}{\mathrm{\kappa <br><br>}},\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\kappa <br><br>}=\frac{G+\sqrt{G^2-4<br><br>H^2}}{2},\mathrm{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>R=\sqrt{\frac{1+P}{2}},<br><br>S=\sqrt{\frac{Q}{2·<br><br>\sqrt{\frac{1+P}{2}}}},\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>Q=\frac{2·<br><br>I}{\mathrm{\kappa <br><br>}·<br><br>\left(1-{\mathrm{\alpha <br><br>}}^2\right)},<br><br>P=\sqrt{1-{\left(\frac{2·<br><br>I}{\mathrm{\kappa <br><br>}·<br><br>\left(1-{\mathrm{\alpha <br><br>}}^2\right)}\right)}^2}.$

7. The method for I/Q mismatch calibration of a receiver as claimed in claim 4, wherein the set of correction parameters (A_p, B_p) is further normalized

such that the power of the output signal of the I/Q correction module equals to that of the input signal of the I/Q correction module.

8. An apparatus for I/Q mismatch calibration of a receiver having an I/Q correction module which performs x_o[n]=A_p·

x_i[n]+B_p·

x*_i[n] where x_i[n] and x_o[n] respectively represent the input and output signal of the I/Q correction module, the superscript * refers to a complex conjugate, and A_p and B_p are correction parameters, comprising;

a signal generator for generating a test signal x(t) which contains a single tone waveform with frequency of (f_c+f_T) Hz, where f_c and f_T are real numbers;

a demodulator for applying I/Q demodulation to reduce the central frequency of the test signal x(t) by f_c Hz and outputting a demodulated signal x_dem(t);

A/D converters for converting the demodulated signal x_dem(t) to a digital signal x_dem[n];

a dual-tone correlator for obtaining measures U₁ and U₂ of the digital signal x_dem[n] output from the I/Q correction module where U₁ and U₂ are values indicative of the frequency response of x_dem(t) at frequency +f_T Hz and −

f_T Hz, respectively; and

a processor for obtaining the set of the correction parameters A_p and B_p according to the measures U₁ and U₂.

9. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 8, the measure U₁ and U₂ are obtained from the coefficients of the Fourier transformation of the x_dem[n] corresponding to the frequency +f_T Hz and −

f_T Hz.

10. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 8, wherein the test signal x(t)=cos(2π

(f_c+f_T)).

11. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 8, wherein the set of correction parameters (A_p, B_p) are obtained by

$\hspace{1em}$

{ A p = R + j ⁢

 

⁢

α

⁢

 

⁢

S B p = - α

⁢

 

⁢

R - j ⁢

 

⁢

S

where α

, R, and S are obtained based on U₁ and U₂.

12. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 11, wherein α

, R, and S are obtained based on

H=real(U₁·

U₂),
I=imag(U₁·

U₂),

and

G=|U₁|²+|U₂|².

13. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 12, wherein α

, R, and S are obtained by

$\mathrm{\alpha <br><br>}=\frac{H}{\mathrm{\kappa <br><br>}},\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\kappa <br><br>}=\frac{G+\sqrt{G^2-4<br><br>H^2}}{2},\mathrm{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>R=\sqrt{\frac{1+P}{2}},<br><br>S=\sqrt{\frac{Q}{2·<br><br>\sqrt{\frac{1+P}{2}}}},\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>Q=\frac{2·<br><br>I}{\mathrm{\kappa <br><br>}·<br><br>\left(1-{\mathrm{\alpha <br><br>}}^2\right)},<br><br>P=\sqrt{1-{\left(\frac{2·<br><br>I}{\mathrm{\kappa <br><br>}·<br><br>\left(1-{\mathrm{\alpha <br><br>}}^2\right)}\right)}^2}.$

14. The apparatus for I/Q mismatch calibration of a receiver as claimed in claim 11, wherein the set of correction parameters (A_p, B_p) is further normalized such that the power of the output signal of the I/Q correction module equals to that of the input signal of the I/Q correction module.