A Power Combiner–Splitter Based on a Rat-Race Coupler for an IQ Mixer in Synthetic Aperture Radar Applications.

Synthetic aperture radar (SAR) is a powerful tool in remote sensing applications that can produce high-resolution images and operate in any weather condition. It is composed of many RF components, such as the IQ mixer, which mixes the base chirp signal (IF) with the carrier signal (LO) and increases the bandwidth of the transmitted signal to twice the maximum frequency of the base chirp signal, reducing the workload of Programmable Field Gate Arrays (FPGA) and increasing the resolution of the SAR system. This research proposes a power combiner–splitter design that will be used as a supporting component to construct the IQ mixer in SAR applications based on a rat-race coupler. The measurement results show that the coupler has good S-parameter values.  S 11 ,  S 22 , and  S 33  have a low reflection value below −17 dB,  S 13  has a high isolation value below −22 dB, and  S 21  and  S 31  have a low attenuation value below −4 dB with amplitude unbalance below 0.1 dB and phase unbalance below 1 ° . The 150 MHz requirement bandwidth for the RF signal is also achieved. [ABSTRACT FROM AUTHOR]