Wideband microwave circuit design using phase inverter

Abstract

Parallel-strip line (PSL) is a balanced transmission line. It can provide many advantages of the differential nature. By making this characteristic of the PSL, a phase inverter can be easily implemented. In this project, the phase inverter is applied to both passive and active circuit designs with a wideband performance. For a passive approach, the phase inverter is investigated to construct a wideband band-pass filter, which provides 108% in measured impedance bandwidth for the return loss smaller than -10 dB. The simulated and measured group delay from 0.5 GHz to 1.3 GHz varies 1.03 and 1.68ns, which demonstrates a relatively flat group delay response. For an active approach, a wideband parallel-strip balun with differential outputs is proposed. The measured differential output phase bandwidth centered at 1 GHz is 160% (0.1 GHz - 1.7 GHz), which has maximum 10 degrees of phase error. For the measured port-to-port isolation and return loss below -10 dB, it provides 100% operation bandwidth (0.48 GHz - 1.48 GHz). Furthermore, the balun is applied to a balanced frequency doubler. For the input frequency from 0.1 GHz to 1.7 GHz, the measured bandwidth of the positive conversion gain is 160% which is more superior than the conventional designs.