A Bandpass Filter with Switch Function Based on Slotline Resonator and PIN Diode

A novel bandpass filter (BPF) with the switch function is proposed. It consists of three slotline step-impedance resonators, two L-shaped feed lines, and three microstrip bridges. The microstrip bridge is loaded with a PIN diode, controlled to turn on and off. Design the coupling matrix in the ON state to meet performance indicators, and improve the OFF-state suppression (OSS) in the OFF state by loading diodes on each resonator. The final measurement shows that the center frequency of the BPF with the switch function in the ON state is 0.975 GHz, the insertion loss is less than 1.18 dB, the return loss is better than 19.9 dB, and the fractional bandwidth is 18.67%. The OSS of the passband in the OFF state is better than 46.1 dB, and it is better than 20 dB in the range below 1.458 GHz.