Coupled Line Wide Stop Band Diplexer Using Stepped Impedance Resonator

This work presents a new wide stop band diplexer for S and C band. The parallel coupled line sections with an additional microstrip line section is used for each pass band path. The mathematical analysis with generalized guideline is presented for diplexer design. According to the measured results, the stop-band rejection is achieved up to 10f
c1
while maintaining 20dB suppression and 2.16 pass band frequency ratio. The in-band isolation between two output path are below 43dB, 56dB; insertion losses (IL) are 1.86dB, 2.2dB; and bandwidths are 30%, 28% at lower and upper pass band path of the diplexer respectively.