Microstrip Trisection Filter

Model

The first figure shows the geometry of a microstrip trisection filter on a substrate with a relative dielectric constant of 10.8 and a thickness of 1.27 mm. The structure consists of open loop resonators and produces asymmetric frequency response  with an attenuation pole.  Edge sources are used to feed the microstrip line at two ports.

Simulation

A template broadband simulation is prepared and then the S-parameter Simulation Setup tool is used to build necessary simulations to extract the two-port S-parameters of the filter. The UPML absorbing boundary conditions are used to truncate the domain.

Results

The S-parameter Evaluation tool is employed to calculate S-parameters of the filter. The simulated frequency response of the filter is illustrated in the second figure. It shows that an attenuation pole of finite frequency occur on the upper side of the passband which provides higher selectivity.

Ref. Jia-Sheng Hong and M.J. Lancaster, Microstrip Filters for RF/Microwave Applications, New York:Wiley-Interscience, 2001.