Broadband and Compact Tunable Reflection‐Type Phase Shifter Based on Microstrip Slotline Coupler

ABSTRACT This paper presents a broadband and compact tunable reflection‐type phase shifter based on microstrip slotline coupler. The phase shifter consists of a microstrip slotline 3 dB coupler, along with two identical reflected loads made of variable capacitors and high‐impedance transmission lines shorter than a quarter wavelength. This structure increases the bandwidth of reflection‐type phase shifter and reduces the maximum insertion loss and the fluctuation of insertion loss. The measured return loss of the phase shifter shows a 47.2% bandwidth better than 10 dB, with center frequency insertion loss of 1.0∼2.7 dB and a maximum phase shift of . The phase shifter occupies an area of at 3.6 GHz.