Blind IQ-Regeneration for Six-Port-Based Direct Conversion Receiver with Low Analog Complexity

Mobile multi-protocol radio terminals require receivers with wideband capabilities in order to support a large number of services at many different carrier frequencies. In this paper, test-signal-free calibration and IQ-regeneration are presented for a novel six-port-based direct receiver. The receiver performs an online DC-offset cancellation. Therefore, the analog circuitry effort within the front-end can be reduced to the effort of conventional mixer-based direct receivers, whereas the DC-offsets can be removed completely before the analog-to-digital conversion. This enables the use of blind source separation algorithms instead of test-signal calibration. It is shown that the transmission behavior of the "six-port" can be estimated via blind source separation algorithms. This includes the digital correction of analog amplitude and phase imbalances within the receiver. The combination of a six-port-based direct receiver and blind IQ-regeneration makes the proposed system concept an interesting candidate for broadband and multi-protocol wireless applications.