An Improved SPST Switch Using PIN Diodes

This work presents an improved single-pole-single-throw (SPST) switch using PIN diodes. The primary aim of the design is to mitigate the parasitic effects of a PIN diode across a wide frequency range. However, as theoretical parasitic compensation is performed solely at a specific frequency, the comprehensive switch performance depends on the wideband parasitic values. To accomplish this, adjustments are made to the diode parasitic values to expand the bandwidth of the switch. The diode is employed in the shunt arm and connected to the main line via an impedance transforming network. A transmission line-based analysis is provided to explain the working principle of the switch. Finally, the proposed design is verified through fabrication and measurements in the X-band. The overall responses show significant improvement compared to the conventional design. The simulation shows that a single stage SPST switch provides 20 dB isolation over 1 GHz at the mid-band frequency of 10.0 GHz which is at least 75% more than the conventional design using the same diode. The mid-band insertion loss also decreases.