Design of LO Phase Shifter Based on Quadrature Hybrid Ring Coupler for IQ Mixer in Synthetic Aperture Radar Applications

Synthetic Aperture Radar (SAR) can produce high-resolution images and operate in any weather condition, day and night, without a light source. One of the important components that construct an RF SAR sub-system is the IQ Mixer, which mixes the base chirp signal with the carrier signal and increases the bandwidth of the transmitted signal to twice the maximum frequency of the base chirp signal, which is important because the range resolution of SAR depends on the bandwidth of the transmitted signal. This research proposes a LO Phase Shifter design that will be used as a supporting component for IQ Mixer in Synthetic Aperture Radar applications based on a Quadrature Hybrid Ring Coupler. The result from the fabricated measurement shows that the coupler has a good S-parameter value. S11 has a low reflection of -33.85 dB, S41 has a high isolation of -29.56 dB, S21 and S31 have low attenuation with amplitude unbalance of 0.2 dB and phase unbalance of 1.93 degrees. The requirement bandwidth of 150 MHz at the center frequency of 5.5 GHz was also achieved.