Extend IQ Six-Port Demodulator RF Bandwidth by 250% Using Fourier Based Modelling

Six-Port IQ demodulator/interferometer has gained the attention from the research community thanks to its high potential to address accurate measurement of amplitude and phase of microwave signals at a reduced coast and low-power consumption. The passive structure of the six-port demodulator is build up with a passive multi-port junction, i.e. hybrid couplers and power dividers associated to four power detectors. A modelling of the propagation microwave paths associated to a calibration procedure is considered to express the four detected powers as a function of IQ signals. In this paper, we investigate the limits of the mathematical modelling on frequencies far beyond the center frequency of microwave microstrip functions used in the six-port circuitry. As a demonstration, we exemplary show that an appropriate modelling based on Fourier analysis extend the frequency of the operation from single 2.45 GHz to 500 MHz – 6 GHz, only limited by the test bench.