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High power, gan, quarter-wave length switches for x-band applications

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2019
Turan, Duygu Işınsu
RF switches are one of the main building blocks of many communication and radar systems. In time-multiplex systems they are used to switch between the high power transmit path and the high sensitivity receive path, and thus needs to exhibit low insertion loss, while achieving high isolation. Low insertion loss for such switches reduces signal degradation on either path, while high isolation reduces signal leakage from the transmitter to the receiver. Since switches are connecting the antenna and the transmit/receive paths, they should also be very linear, in order not to introduce any nonlinearities to the signal. They should be able to handle large input power values, especially when used in radar systems. This thesis presents two single pole double throw switches built on Gallium Nitride (GaN) on silicon carbide (SiC) technology as a part of transceiver module designed for X-band radar applications. Both of the switches are designed to handle 25 Watts of input power. Fabricated die of Configuration I shows nearly 0.3 dB of insertion loss for most of the part of the band of interest. The die area of the switch is 2.9 x 2.1 mm2. Measurement results of Configuration II exhibits an isolation of better than 50 dB while offering insertion loss better than 0.8 dB for most of the band. Both of the switches are very well matched. Measured return loss of switches are better than 15 dB, and 13 dB, for Configuration I, and Configuration II, respectively, for the frequency band of operation.