Ultra-Compact Band-Pass Filter at Low Frequency of Operation

|An ultra-compact band-pass (cid:12)lter is presented in this paper. The (cid:12)lter is designed to operate in the medical implants communication service (MICS) band ranging from 401 MHz to 406 MHz. The (cid:12)lter is designed on a Rogers RT/duroid substrate with " r = 2 : 94 and tan (cid:14) = 0 : 0012. The overall size of the proposed (cid:12)lter is only 30 : 6 mm (cid:2) 18 : 5 mm (0.058 (cid:21) g (cid:2) 0 : 035 (cid:21) g ), making it suitable for compact, portable devices. An equivalent circuit model is also proposed for the analysis of the (cid:12)lter geometry. From the circuit model, it can be concluded that the (cid:12)lter exhibits the characteristics of a dual-composite right left-handed (D-CRLH) transmission line. This is also con(cid:12)rmed from the dispersion characteristics. The salient features of the proposed (cid:12)lter include ultra-compactness at low operating frequency, harmonic suppression of 3.7 times of the passband frequency, fractional bandwidth of 4.45%, and good roll-off rate of 297.6 dB/GHz in the lower stopband and 116.4 dB/GHz in the upper stopband.