Microstrip Quasi-Elliptic Low Pass Filter in Multilayer Topology

A quasi-elliptic stepped impedance low pass filter using modified dielectric is proposed in this work. The dielectric is modified using plated hole vias and is implemented with double layer topology. The pitch should be 0.22λg and the height of the artificial dielectric should be three times the other dielectric to result in quasi-elliptic characteristics. The presented technique resulted in transmission zero at the stop band edge of slow wave Butterworth filter with 78 dB attenuation and is higher compared to similar works reported. For proof of concept, the filter is fabricated and performance is validated with measurement. The simulated and measured results showed good mutual agreement with each other.