Dual-Band Schiffman Phase Shifter with Large Frequency Ratio and Wide Bandwidths

This paper presents a dual-band Schiffman type phase shifter with large frequency ratio and wide bandwidths. The proposed phase shifter employs three cascaded Symmetric Stepped Impedance Transmission Lines (SSITLs), as the reference line, and one Symmetric Stepped Impedance Parallel Coupled Line (SSIPCL), as the phase adjusting line. Detailed design theory is presented and validated with practical design of a prototype 90° dual-band phase shifter, working at 2 GHz and 11 GHz. Simulation and measured results demonstrate that equal absolute bandwidths of 1.2 GHz are obtained at two design frequency bands, with phase error of ± 4.5° and insertion losses of less than 2 dB.