IQ mismatch correction for zero-IF/low-IF TX/RX

A transceiver circuit for transmitting and receiving radio frequency (RF) communication signals, including a transmit (TX) end, and a receive (RX) end, at the TX end and/or the RX end the circuit comprising:

• an analog signal chain, and including analog circuitry that introduces IQ mismatch signal impairments;
• a digital signal chain including an IQmc mismatch corrector to filter In-phase and Quadrature digital signals to provide IQmc correction to correct the IQ mismatch impairments;
• and
• an ADC (analog-to-digital conversion) circuitry to provide an interface between the analog signal chain and the digital signal chain;
• the IQmc mismatch corrector including:
• an I-path coupled to receive the In-phase digital signals (I signal), and
• a Q-path coupled to receive the Quadrature digital signals (Q signal);
• and
• an in-path filter element to filter either the I signal or the Q signal received in the same path, and
• a cross-path filter element to filter either the I signal or the Q signal received in the other path;
• wherein the IQmc mismatch corrector to provides IQmc correction that results in a change in linear response through the analog and digital signal chains, the circuit further comprising:
• in the analog signal chain, a digital step attenuator (DSA) to provide a selected DSA step attenuation;
• in the digital signal chain,
• a DSA gain/phase correction block to provide a DSA correction signal to the DSA to correct the selected DSA step attenuation, and
• a DSA gain/phase correction update module to adjust the DSA correction signal to compensate for the change in linear response.

A method to provide IQ mismatch correction, for use in a system for radio frequency (RF) communication, the method useable at a transmit (TX) end, and/or at a receive (RX) end in which an analog signal chain includes analog circuitry that introduces IQ mismatch signal impairments, the method comprising:

• digital filtering, in an IQmc corrector, In-phase and Quadrature digital signals to provide IQmc correction to correct the IQ mismatch impairments;
• the digital filtering for IQmc correction accomplished by:
• receiving, in an I-path, the In-phase digital signals (I signal), and
• receiving, in a Q-path, the Quadrature digital signals (Q signal), and
• filtering in an in-path filter element either the I signal or the Q signal received in the same path, and
• filtering in a cross-path filter element either the I signal or the Q signal received in the other path;
• wherein the analog signal chain includes a digital step attenuator (DSA) to provide a selected DSA step attenuation, the method further comprising;
• determining a change in linear response through the analog and digital signal chains that results from the digital filtering for IQmc correction;
• and
• providing a correction signal to the DSA to adjust the selected DSA step attenuation to compensate for the change in linear response.