Design of S-Band Interdigital Band Pass Filter

Abstarct: A Band Pass Filter is one of the key components in the receive chain of any Transmit-Receive Module of an Active Array Radar. The critical parameter for the design of a BPF for a TR module is the form factor,insertion loss and rejection. Hence a microstrip based interdigital (tapped) BPF for S-Band TR Module (3.1-3.5 GHz) was designed. The filter was designed to achieve a typical insertion loss of 2.0 dB in the passband and a rejection of 50 dB on either side at 1.2 GHz away from centre frequency. The filter was realized and tested successfully on a 25 mil thick Rogers’s substrate having a dielectric constant of 10.2. Further development is under progress to suppress the harmonics.