Low complex IQ-imbalance compensation for low-IF receivers

The evolution of wireless communication systems forces the development of cheaper and smaller analog components for the RF (radio frequency)-frontend. To an increasing degree digital algorithms are used to compensate analog nonidealities, lowering the requirements for the analog frontend. Consequently, simpler, cheaper and smaller analog frontends can be applied without loosing overall system performance. The most critical frontend-nonidealities, whose dimensions are dependent on the chosen transceiver concept, are amplifier-nonlinearities, phase noise, DC-offset, 1/f-noise, carrier frequency offset and IQ-mismatch. In recent years homodyne and low-IF (intermediate frequency) architectures supersede the conventional heterodyne concepts. In this paper we will present IQ-imbalance compensation techniques for low-IF transceiver architectures and we will present a very low-complex digital compensator, which operates with only four complex multiplications per sample.