DESIGN OF COMPACT RECONFIGURABLE BROADBAND BAND-STOP FILTER BASED ON A LOW-PASS FILTER USING HALF CIRCLE DGS RESONATOR AND MULTI-LAYER TECHNIQUE

This paper describes the design of a two-pole low-pass and band-stop filters. The low-pass structure is designed at the cutoff frequency of 2 GHz for the L-Band applications. This architecture uses half circle defected ground structure HCDGS instead full circle DGS resonator. Both the HCDGS shapes are etched in the ground plane and coupled via a substrate with a compensated capacitor. The rejection bandwidth of the LPF covers a large wideband spectrum. Therefore, the band suppression reaches more than 3fc. The filter is simulated and fabricated. The measured results are in good agreement with the full-wave simulated ones, showing the merits of compact size and sharp roll-off. The multi-layer technique has been used in order to realize a transformation from low-pass behaviours to band-stop characteristics, keeping the same passband features. The new extracted band-stop topology is simulated and optimized using an RO4003 substrate with relative permittivity of 3.38 and thickness of h = 0.813 mm. The structure has a wide stopband with over 20 dB rejection from 3.5 GHz to 8.5 GHz. Such filters can be used for L-band and military applications.