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

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.

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.