Decoupling transmitter from loopback path IQMM with phase delay-elimination by rotation

1 . A system, comprising:

a transmitter configurable to transmit a quadrature amplitude modulation (QAM) signal, wherein the QAM signal includes an in-phase (I) chain signal and a quadrature (Q) chain signal;

a first circuit configurable to receive the QAM signal and transmit an attenuated signal responsive the QAM signal;

a receiver configurable to receive the attenuated signal;

a delay element configurable to introduce a first phase delay in a transmitter-receiver loop, wherein the transmitter-receiver loop comprises the transmitter, the first circuit, and the receiver; and

a controller configurable to:

determine an I-Q mismatch (IQMM) of the transmitter-receiver loop with the first phase delay;

determine an IQMM of the transmitter-receiver loop with a second phase delay, wherein the second phase delay is different than the first phase delay;

determine an IQMM of the transmitter responsive to the IQMM of the transmitter-receiver loop with the first phase delay and the IQMM of the transmitter-receiver loop with the second phase delay; and

produce a correction signal responsive to the IQMM of the transmitter.

2 . The system of claim 1 , wherein the delay element is configurable to introduce the first phase delay by changing a clock generation phase in the receiver.

3 . The system of claim 1 , wherein the delay element is configurable to introduce the first phase delay by using a phase shift at an amplifier in the transmitter.

4 . The system of claim 1 , wherein the delay element is configurable to introduce the first phase delay by adding a phase delay to a signal path in the receiver.

5 . The system of claim 1 , wherein the delay element is configurable to introduce the first phase delay by adding a delay to a clock path in the receiver.

6 . The system of claim 1 , wherein the first phase delay is a multiple of 90 degrees.

7 . The system of claim 1 , wherein the first phase delay decouples the IQMM of the transmitter from an IQMM of the receiver.

8 . The system of claim 1 , wherein the transmitter-receiver loop is configurable to provide a feedback signal to the transmitter.

9 . A system, comprising:

a transmitter having a first in-phase (I) signal chain, a first quadrature (Q) signal chain, a first mixer, and an amplifier;

a first circuit configurable to receive a first signal from the transmitter and produce an attenuated signal responsive to the first signal;

a receiver configurable to receive the attenuated signal and provide a feedback signal to the transmitter, wherein the receiver includes a second mixer, a second I signal chain, and a second Q signal chain, and wherein the transmitter, the first circuit, and the receiver form a transmitter-receiver loop;

a delay element configurable to introduce a first phase delay and a second phase delay in the transmitter-receiver loop; and

a controller configurable to receive the feedback signal and determine an I-Q mismatch (IQMM) of the transmitter responsive to the first phase delay and the second phase delay.

10 . The system of claim 9 , wherein the controller is further configurable to determine an IQMM of the transmitter by:

determining a first IQMM of the transmitter-receiver loop with the first phase delay, wherein the first phase delay is zero;

determining a second IQMM of the transmitter-receiver loop with the second phase delay; and

determining the IQMM of the transmitter responsive to the first IQMM of the transmitter-receiver loop and the second IQMM of the transmitter-receiver loop.

11 . The system of claim 10 , wherein the controller is further configurable to:

correct the IQMM of the transmitter by providing a correction signal to the transmitter.

12 . The system of claim 9 , wherein the delay element is configurable to introduce the first phase delay and the second phase delay by changing a clock generation phase in the receiver.

13 . The system of claim 9 , wherein the delay element is configurable to introduce the first phase delay and the second phase delay by adding a delay to a clock path in the receiver.

14 . A method, comprising:

transmitting a quadrature amplitude modulation (QAM) signal with a transmitter, wherein the QAM signal includes an in-phase (I) chain signal and a quadrature (Q) chain signal;

attenuating the QAM signal to produce an attenuated signal;

receiving the attenuated signal at a receiver, wherein the receiver and the transmitter form a transmitter-receiver loop;

determining an I-Q mismatch (IQMM) of the transmitter-receiver loop with a first phase delay;

determining an IQMM of the transmitter-receiver loop with a second phase delay, wherein the second phase delay is different than the first phase delay;

determining an IQMM of the transmitter responsive to the IQMM of the transmitter-receiver loop with the first phase delay and the IQMM of the transmitter-receiver loop with the second phase delay; and

producing a correction signal responsive to the IQMM of the transmitter.

15 . The method of claim 14 , further comprising:

introducing the first phase delay by changing a clock generation phase in the receiver.

16 . The method of claim 14 , further comprising:

introducing the first phase delay by phase shifting the QAM signal in a signal path in the transmitter.

17 . The method of claim 14 , further comprising:

introducing the first phase delay by adding a phase delay to a signal path in the receiver.

18 . The method of claim 14 , further comprising:

introducing the first phase delay by adding a delay to a clock path in the receiver.

19 . The method of claim 14 , wherein the receiver is configurable to provide a feedback signal to the transmitter.

20 . The method of claim 14 , wherein the first phase delay is introduced between a mixer in the transmitter and a mixer in the receiver.

21 . The method of claim 14 , wherein the second phase delay has a value of 0.

22 . The method of claim 14 , wherein the method is performed in real-time.

23 . The method of claim 14 , wherein the QAM signal is transmitted via an antenna.