In this paper, a lowpass filter with -3 dB cutoff frequency of 5.3 GHz using T-shaped and polygon resonators is presented. The applied resonators create a sharp transition band of 0.2 GHz from -3 dB to -40 dB. To obtain an ultra-wide stopband about 54 GHz (10.18fc) with a suppressing level of -21 dB, two different suppressing cells are employed. The overall circuit size is 59.16 mm2, which indicates a small occupied area. To clarify the performance of each resonator and describe the location of the transition zeros, exact equations based on the equivalent LC circuits have been calculated.
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