Design of an X-Band 6-Bit Phase Shifter

The design and performance of X-band (8-12 GHz) 6-bit MMIC phase shifter is presented. The phase shifter is fabricated in 0.25um GaAs pHEMT technology. Each bit of this phase shifter design is based on an optimum topology to reach balanced and optimal insertion loss, phase shifting accuracy and return loss. A new type of loaded-line topology for small phase shift states is also relevant. The adoption of the parallel transistors and a resonance inductor in parallel with the series transistors is to improve the isolation of the SPDT switch. Ordering the sequence of bits is optimized so as to minimize the overall return and insertion loss. The proposed phase shifter, with a chip size of 4.2mm*2.2mm, exhibits better than 10dB return loss, no more than 7.6 dB insertion loss, better than 3.3° RMS phase error and 0.7dB RMS amplitude error over the operating frequency range.