Design of a cheap compact low-pass filter with wide stopband

Abstract

In these work, a cheap and compact Low-Pass filter (LPF) with wide stopband is designed using modified hairpin resonator. The first transmission zero is obtained from the transfer function (TF) analysis of the hairpin 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 cutoff 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.

Design of a Low Cost Compact Elliptic Function LPF Using Open Circuited Stubs

“…Inclusion of defected ground structures (DGS) in the circuit is another way of improving the stop band performance [11][12]. A sharp roll-off factor while maintaining a minimum insertion loss is an important parameter to implement any microwave filter [13][14][15][16]. In case of LPF using coupled lines [17], the capacitance of the coupled lines is too small and hence the finite attenuation poles cannot be located close to the passband.…”