Imbalance compensation for direct conversion communication systems

A method for correcting imbalance between real and imaginary signals in a direct conversion receiver comprising:

• receiving a real signal and an imaginary signal from a direct conversion receiver;
• performing quadrature correction, to correct error introduced by the receiver, on the real signal and the imaginary signal to create a corrected real signal and a corrected imaginary signal;
• performing quadrature error estimation with a quadrature estimation module to generate one or more receiver parameters and one or more transmitter parameters;
• receiving the corrected real signal and the corrected imaginary signal at a transmitter correction module, located at the receiver, and performing derotation and equalization on the corrected real signal and the corrected imaginary signal to correct error introduced by a transmitter, the performing derotation and equalization includes dividing the corrected real signal or corrected imaginary signal by a value, the value being a total of one plus an estimate of transmitter amplitude imbalance, and shifting a phase of the corrected real signal or the corrected imaginary signal by an estimate of the unwanted phase shift.

A method, performed at a receiver, for correcting error in a direct conversion communication device comprising:

• receiving a one or more signals from a transmitter;
• performing receiver imbalance compensation including dividing the one or more signals by a value, the value being a total of one plus an amplitude error estimate, to create a result and then rotating the result by a receiver phase error estimate to create one or more quadrature corrected signals;
• performing linear equalization on the one or more quadrature corrected signals to reduce the effects of channel distortion to create one or more equalized signals;
• performing derotation on the one or more equalized signals to achieve carrier frequency offset compensation to create one or more transmitter imbalanced signals;
• and
• performing, at the receiver, transmitter imbalance compensation on the one or more transmitter imbalanced signals to reduce or remove transmitter imbalance introduced by the transmitter.

A direct conversion error correction circuit comprising:

• an integrated circuit configured for processing a real signal and an imaginary signal, the real signal and the imaginary signal received from a transmitter;
• a receiver quadrature correction circuit embodied on the integrated circuit at the receiver, the receiver quadrature correction circuit configured to process the real signal and the imaginary signal to reduce receiver imbalance and create one or more receiver imbalance corrected signals;
• and
• a transmitter correction circuit embodied on the integrated circuit at the receiver, the transmitter correction circuit configured to process the one or more receiver imbalance corrected signals by dividing one or more receiver imbalance corrected signals by a total of one plus an estimated transmitter amplitude imbalance value and shifting a phase of the one or more receiver imbalance corrected signals by an estimate of unwanted phase shift introduced by the transmitter.