Joint transmit and receive I/Q imbalance compensation

• US 8,311,083 B2
• Filed: 12/29/2009
• Issued: 11/13/2012
• Est. Priority Date: 12/29/2009
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Ding, Lei, Yang, Zigang, Mujica, Fernando, Sperlich, Roland
• Primary Examiner(s): HA, DAC V
• Application Number:
  US12/648,898
• Publication Number:
  US 20110158297A1
• Time in Patent Office: 1,050 Days
• Field of Search: 375/219, 375/221, 375/222, 375/260, 375/261, 375/284, 375/285, 375295-297, 375/316, 375/340, 375/347, 455/501, 455/63.1, 455/67.11, 455/37.13, 4551142-1143, 455/115.1, 455/126, 455/296, 455/302, 455/303, 455/305, 332/123, 332/124, 332/159, 332/160, 329/302, 329/306, 329/308, 329318-320, 329349-351, 370/276, 370/278, 370/282, 370/286
• US Class Current: 375/219
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H04B 1/40 Circuits

Abstract

Conventional transceivers do provide some compensation for in-phase/quadrature (I/Q) imbalance. However, these techniques do not separately compensate for I/Q imbalance for the transmitter and receiver sides of the transceiver. Here, a transceiver is provided that allows for compensation of I/Q imbalance in the transmitter and receiver irrespective of the other to allow for a more accurate transceiver.

Claims

1. An apparatus comprising:

a transmit path that is coupled to radio frequency (RF) circuitry, wherein the transmit path includes a modulation compensator that compensates for in-phase/quadrature (I/Q) mismatch in the transmit path;

a switch that is coupled to the RF circuitry;

a delay element that is coupled to the RF circuitry and that is coupled to the switch so as to actuate and deactuate the switch; and

a receive path that is coupled to switch, wherein the receive path includes a demodulation compensator that compensates for I/Q mismatch in the receive path.

2. The apparatus of claim 1, wherein each of the receive and transmit paths further comprise an in-phase path and a quadrature path.

3. The apparatus of claim 2, wherein the in-phase path for the transmit path further comprises:

an in-phase filter that is coupled to the modulation compensator;

an in-phase digital-to-analog converter (DAC) that is coupled to the in-phase filter;

an in-phase low pass filter (LPF) that is coupled to the in-phase DAC; and

an in-phase mixer coupled to the in-phase LPF.

4. The apparatus of claim 3, wherein the quadrature path for the transmit path further comprises:

a quadrature filter that is coupled to the modulation compensator;

a quadrature DAC that is coupled to the quadrature filter;

a quadrature LPF that is coupled to the quadrature DAC; and

a quadrature mixer coupled to the quadrature LPF.

5. The apparatus of claim 4, wherein the transmit path further comprises:

an adder that is coupled to the in-phase mixer and the quadrature mixer;

a local oscillator that is coupled to the in-phase mixer; and

a phase delay circuit that is coupled to the local oscillator and the quadrature mixer.

6. The apparatus of claim 2, wherein the in-phase path for the receive path further comprises:

an in-phase mixer that is coupled to the switch;

an in-phase LPF that is coupled to the in-phase mixer; and

an in-phase analog-to-digital converter (ADC) that is coupled to the in-phase LPF and the demodulation compensator.

7. The apparatus of claim 6, wherein the quadrature path for the receive path further comprises:

a first quadrature mixer that is coupled to the switch;

a quadrature LPF that is coupled to the first quadrature mixer;

a quadrature ADC that is coupled to the quadrature LPF; and

a second quadrature mixer that is coupled to the quadrature ADC and the demodulation compensator.

8. The apparatus of claim 7, wherein the transmit path further comprises:

a local oscillator that is coupled to the in-phase mixer; and

a phase delay circuit that is coupled to the local oscillator and the first quadrature mixer.

9. The apparatus of claim 1, wherein the relationship between an input signal (u(n)) and an output signal (x(n)) for the modulation compensator is:

10. The apparatus of claim 1, wherein the relationship between an input signal (y(n)) and an output signal (v(n)) for the demodulation compensator is:

11. An apparatus comprising:

a transmit path having;

a modulation compensator that compensates for I/Q mismatch in the transmit path;

an in-phase filter that is coupled to the modulation compensator;

a quadrature filter that is coupled to the modulation compensator;

a first DAC that is coupled to the in-phase filter;

a second DAC that is coupled to the quadrature filter;

a first LPF that is coupled to the first DAC;

a second LPF that is coupled to the second DAC;

a first local oscillator;

a first mixer that is coupled to the first local oscillator and the first LPF;

a first phase delay circuit that is coupled to the first local oscillator;

a second mixer that is coupled to first phase delay circuit and the second LPF; and

an adder that is coupled to the first and second mixers;

RF circuitry that is coupled to the adder;

a switch that is coupled to the RF circuitry;

a delay element that is coupled to the RF circuitry and that is coupled to the switch so as to actuate and deactuate the switch; and

a receive path having;

a third mixer that is coupled to the switch;

a fourth mixer that is coupled to the switch;

a second local oscillator that is coupled to the third mixer;

a second phase delay circuit that is coupled to the second local oscillator and the fourth mixer;

a third LPF that is coupled to the third mixer;

a fourth LPF that is coupled to the fourth mixer;

a first analog-to-digital converter (ADC) that is coupled to the third LPF;

a second ADC that is coupled to the fourth LPF;

a fifth mixer that is coupled to the second ADC; and

a demodulation compensator is coupled to the first ADC and the fifth mixer, wherein the demodulation compensator compensates for I/Q mismatch in the receive path.

12. The apparatus of claim 11, wherein the relationship between an input signal (u(n)) and an output signal (x(n)) for the modulation compensator is:

13. The apparatus of claim 11, wherein the relationship between an input signal (y(n)) and an output signal (v(n)) for the demodulation compensator is: