A NOVEL MINIATURIZED UWB BANDPASS FILTER BASING ON E-SHAPED DEFECTED MICROSTRIP STRUCTURE

This paper proposes a novel miniaturized UWB bandpass filter by cascading two miniaturized low-pass and high-pass modules. On account of the slow wave and stopband characteristic of defected microstrip structure(DMS), an E-shaped DMS with low-pass characteristic is presented, and an RLC equivalent circuit is utilized to analyze it. By three-dimensional electromagnetic modeling, the S parameters can be obtained to extract the initial parameter values of the RLC equivalent circuit and verify the validity of equivalent circuit in Advanced Design System. The high-pass module uses a lump element to reduce the circuit dimension. The high frequency selectivity can be achieved by loading L-shaped stubs, which produces one transmission zero at the upper band of passband and has a good rectangle coefficient of 1.2 (25 dB-bandwidth/3 dB-bandwidth ). To verify the idea, a compact UWB bandpass filter is simulated and fabricated. The result shows that the passband range is 3.1–10.6 GHz with 1 dB loss, and the measurement has a good agreement with the simulation. Besides, a notched wave working in X wave band can also be generated. Compared with the previous works, this UWB bandpass filter has the advantages of miniature and high selectivity.