Reflectionless Bandstop Filter Based on Suspended Microstrip Line

In this report, a suspended microstrip line dual-port reflectionless bandstop filter is designed. The filter consists of a bandstop section loaded with open branch lines on the lambda g/4 transmission line and a bandpass section loaded with terminating resistors at the input/output ports, where the reflected signals are absorbed by the resistors to achieve the two-port non-reflection characteristic. The fractional bandwidth of this filter is 38.9%, the attenuation of S-11 and S-22 is greater than 10.2dB in the 0.5-6.8GHz frequency band, and the filter has a wide non-reflection frequency band.