Design and Implementation of an Ultra- Wideband Six-port Network

This paper presents a six-port network over an ultrawideband (UWB) of 2–8GHz. Its key component is the six-port junction, which consists of a Wilkinson power divider and three 3-dB quadrature couplers. This six-port junction is accomplished in a low dielectric constant substrate (Rogers RT/duroid 5880). Multi-section impedance transformation is applied in the power divider, and the quadrature coupler is realized by using two 8.34 dB couplers in tandem. An ultra-wideband operation of the six-port junction is verified by full electromagnetic simulations and measurements. The results show that the designed devices exhibit good performance across 2–8 GHz band: the return losses at input ports are higher than 15 dB, the insertion losses from input ports to the remaining ports are 7.2 dB ± 1.7 dB, the isolation between two input ports is greater than 20.5 dB, and the maximum phase difference compared with the theoretical behavior between two test ports is 10◦. For the manufactured six-port junction, a six-port phase measurement system and a calibration technique based on support vector regression (SVR) are introduced. Results show that the SVR model can achieve a mean phase error of 1.5274◦.