DESIGN OF MICROSTRIP MEANDERED DUAL MODE WIDEBAND BANDPASS FILTER USING QUARTER WAVELENGTH STUBS

This paper proposes a new compact microstrip meandered dual mode loop resonator wideband bandpass filter. The proposed filter is constructed by using bandstop filter with orthogonal direct connected feed lines. The passband is created inside a wide stopband by using the quarter wavelength open circuited stubs which are connected to the opposite sides of the input and output port sides. A small square patch perturbation element is added at right top corner of symmetrical axis of the loop. Perturbation element excites dual degenerate modes thereby improving the selectivity of the filter on both higher and lower side of the passband. Simulated filter is designed at a center frequency of 3.85 GHz shows a very low insertion loss of 0.3 dB and high return loss of above 17 dB with a wide fractional bandwidth of 55.26 %. The introduced filter is compact with low insertion loss, high return loss and wide bandwidth suitable for modern wireless and satellite communication systems.