Two paralleled Ba0.25 Sr0.75 TiO3 ferroelectric varactors series connected coplanar waveguide microwave phase shifter

Abstract

A distributed phase shifter of coplanar waveguide (CPW) using ferroelectric (Ba0.25 Sr0.75 TiO3) film varactors with parallel-plate electrodes is presented. In order to satisfy the requirement of small dimension of the parallel-plate varactor for the design of phase shifter and impedance match of the circuit, two parallel-plate varactors of 8×10 μ m2 are connected in series. The fabricated CPW phase shifter exhibited low insertion loss of 2.3 dB and large differential phase shift of 170° at 7 GHz with a dc bias voltage of 25 V. © 2009 American Institute of Physics.