Compact ultra-wideband bandpass filter with variable notch characteristics based on transversal signal-interaction concepts

• Published in: International journal of RF and microwave computer-aided engineering Vol. 24; no. 5; pp. 549 - 559
• Main Authors: Mirzaee, Milad, Virdee, Bal S., Noghanian, Sima
• Format: Journal Article
• Language: English
• Published: Hoboken Blackwell Publishing Ltd 01.09.2014; Hindawi Limited
• Subjects: bandpass filter (BPF); Bandpass filters; Inclusions; Mathematical models; Microwaves; Noise levels; Selectivity; Stepped; stepped impedance resonator (SIR); transversal signal-interaction concepts; ultra-wideband (UWB) filter; Ultrawideband; variable notch-band
• ISSN: 1096-4290; 1099-047X
• DOI: 10.1002/mmce.20798

ABSTRACT A novel technique is presented to design highly compact microstrip ultra‐wideband (UWB) bandpass filters that exhibit high selectivity quasi‐elliptical response. The design is based on transversal signal‐interaction concepts that enable the inclusion of single or dual notch‐bands within the filter's passband to eliminate interference from other services that coexist within the UWB spectrum. The filter configuration comprises of two transmission paths which include folded T‐shaped stepped impedance resonators (SIRs) that are capacitively coupled with the input/output lines to enable signal transmission. It is shown that by combining the filters of different passband centre frequencies an UWB filter can be realised with either a single‐ or dual‐notch function. The theoretical performance of the filter is corroborated via measurements to confirm that the proposed filter exhibits UWB passband of 123% for a 3 dB fractional bandwidth, a flat group‐delay with maximum variation of less than 0.3 ns, passband insertion loss less than 0.94 dB, high selectivity, a sharp rejection notch‐band with attenuation of −23 dB, and a good overall out‐of‐band performance. Furthermore, the filter occupies a significantly small area of 94 mm2 compared with its classical counterparts. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:549–559, 2014.