RF Front-End Electrically Tunable Null-Forming Circuit Based on Reflective-Type Phase Shifter

In this paper, a radio frequency front-end electrically tunable null-forming circuit has been presented. The circuit is composed of quadrature couplers and tunable phase shifters. A quadrature branch-line coupler and a low insertion loss reflective-type phase shifter with a full 360°phase shift range at 6 GHz are simulated as the critical components of the circuit. Finally, an 8-element circuit is simulated at 6 GHz to verify the proposed circuit. The results show that the circuit can successfully construct a tunable null in a full field-of-view with dc bias voltage changing when it is applied to an 8-element uniform linear array. For the best performance element, the depth of the null reaches 24 dB.