Concurrent Dual-Band Six-Port Receiver for Multi-Standard and Software Defined Radio Applications

Abstract

This paper proposes a novel concurrent dual-band receiver architecture that uses only one six-port correlator circuit to downconvert two signals in two different bands concurrently. The receiver is reconfigurable over a broadband to simultaneously receive two different signals with different modulation techniques and bandwidths. There are no limitations on the carrier frequencies of the two signals except that they have to be within the bandwidth of the six port receiver. The mathematical model for the receiver is derived and subsequently implemented to evaluate its performance. This approach shows that, by analytically choosing the frequencies of the two local oscillator signals sent into the six-port correlator, the in-phase (I) and the quadrature (Q) components of each of the two input RF signals can be obtained from the filtered high-pass and low-pass components of the diode detectors outputs. A black box model, which uses a modified memory polynomial, is used to calibrate the receiver. The calibration constants are estimated by sending a training signal of similar characteristics as the signal to be received. Two signals pairs with different modulation types are received to verify the model, and to evaluate the performance and test the robustness of the receiver. A 64-QAM signal at 2.5 GHz and a 16-QAM signal at 3.0 GHz, both with a data rate of 2 Mbps are received. The measured EVMs were 1.9% for the 64-QAM and 1.8% for the 16-QAM. Real communication signals, WCDMA and LTE were also received concurrently with measured EVMs of 1.9% and 2.0%, respectively. A bit error rate (BER) profile of the receiver for a 16QAM and 64QAM, both at 2Mbps is also plotted to evaluate the receiver.