In this paper, miniature planar UWB filters with circular slots in ground is presented and we are using a new technique by etching a wideband circular-shape slot resonator in the ground plane of the filters. The proposed filters have compact size of 15 × 12.4mm2. Two filters are introduced and the final design achieves flat insertion loss and linear phase of S12 throughout the passband (3.14-8.28 GHz) but occasional slight ripple occurs. Two different results are shown and the minimum insertion loss is less than 0.13 dB for both of presented filters.
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