In these work, a cheap and compact Low-Pass filter (LPF) with wide stopband is designed using modified hair-pin resonator. The first transmission zero is obtained from the transfer function (TF) analysis of the hair-pin resonator. Further, open stubs are added to widen the stopband. An approximate LC equivalent circuit of the proposed structure is derived and the response is in accord with simulated result. A prototype of the proposed LPF is fabricated on FR4 substrate. The proposed LPF has -3 dB cut-off frequency at 1.1 GHz with wide stopband ranging from 1.6 GHz to 11.5 GHz. The size occupied by the proposed LPF is 15.8 mm x 14.3 mm. In the passband region, the insertion loss is -0.3 dB and return loss is better than -25 dB. The proposed LPF is measured and there is a good agreement between the simulated and measured results.
low pass filter, wide stopband, hair-pin resonator, open-stubs
The authors want to acknowledge Mr. Lakhindar Murmu and Mr. Amit Bage of ISM Dhanbad for extending their help in the completion of the project.
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