Wideband 0.9 GHz to 5 GHz six-port and its application as digital modulation receiver

A six-port reflectometer which operates from 0.9 GHz to 5 GHz is proposed, constructed and characterised using MIC techniques. Results from the new structure, when compared to those obtained from a commercial network analyser, show a maximum error of about 2° in phase and about 0.6 dB in reflection coefficient over the entire operating band. In addition, the reflectometer exhibits less than 3 dB noise figure below 3 GHz. The use of the six-port reflectometer as a digital receiver is presented, along with modifications to the demodulation, diode linearisation and calibration algorithms normally associated with this class of receiver. Bit error rate measurements and simulation results are given for QPSK signals under a variety of operating conditions. It is shown that the resulting receiver can give bit error rates of as low as 8×10^-7 for input power levels of -37 dBm. Such a receiver should find application across all of the available frequency bands currently used for personal wireless communications.