Analysis and Design of a X-Band Analog Phase Shifter for Passive Millimeter-Wave Imaging Application

The analysis, design and measurement of a Monolithic Microwave Integrated Circuit (MMIC) analog phase shifter is implemented based on 0.15 $\mu$m GaAs pHEMT process. We propose a flexible methodology for phase shifter design which utilizes multistage cascaded phase shifting sections. The equivalent circuit model of the GaAs pHEMT diode is established and the characteristic of the phase shifting section is analyzed. By adjusting the characteristic of the phase shifting section and selecting appropriate number of stages, desired overall performance of the phase shifter is obtained, including over 100° phase shift range, low and nearly constant insertion loss during phase shifting and excellent phase stability when input signal power varies. A single control voltage is required for the chip and the DC consumption is almost zero. This phase shifter has a compact chip size of $1.65 mm \times 1.1$ mm which is suitable for high-integrated phased arrays in passive millimeter-wave imaging.