A dual notched band UWB-BPF based on microstrip-to-short circuited CPW transition

Abstract

This paper proposes a dual notched band ultra-wideband (UWB) bandpass filter (BPF) based on hybrid transition of microstrip and coplanar waveguide (CPW). The CPW in ground plane houses a stepped impedance resonator shorted at ends, and is designed to place its resonant modes within the UWB passband. The microstrips on the top plane are placed some distance apart in a back-to-back manner. The transition of microstrip on top and shorted CPW in the ground is coupled through the dielectric in a broadside manner. The optimized design of the transition develops the basic UWB spectrum with good return/insertion loss and extended stopband. Later, defected ground structure, embedded in CPW, and split ring resonators, coupled to feeding lines are utilized to develop dual sharp passband notches. The simulated data are verified against the experimentally developed prototype. The proposed dual notched UWB-BPF structure measures only 14.6 × 7.3 mm2, thereby justifying its compactness.

A miniaturized low‐cost microstrip‐to‐coplanar waveguide transition‐based ultra‐wideband bandpass filter with multiple transmission zeros

“…Column 4 depicts that dual notches of the proposed structure have good attenuation (>15 dB) at 6.1 (C band) and 8.1 GHz (X band). The proposed BPF has a wide stopband till 18 GHz with attenuation greater than 15 dB unlike most BPFs, 2,8‐11,13 which possess narrow stopband. The stopbands reported in other studies 3‐7,12 are quite wide, but they possess poor passband characteristics in terms of insertion/return loss.…”

“…It can be observed from column 1 of Table 1 below that the proposed structure is developed on a low‐cost dielectric unlike others 2‐10,12,13 . Column 2 indicates that the proposed structure meets the FCC passband requirement of 3.1 to 10.6 GHz comfortably.…”

“…The presence of TZs at either passband edge is very crucial to the frequency characteristics of any BPF for its enhanced selectivity. From column 3, it is observed that the proposed structure possesses TZs at both the passband edges unlike, 2,3,7‐9,11‐13 which do not possess TZ at either passband edges, whereas 4‐6,10 possess TZ at only one passband edge. Column 4 depicts that dual notches of the proposed structure have good attenuation (>15 dB) at 6.1 (C band) and 8.1 GHz (X band).…”

“…This spectrum is also home to other RF sources like WLAN, C, X band, and so on, which are concentrated pockets of high power and often act as sources of interference to the UWB systems. For these UWB devices to operate interference free, researchers have designed and developed UWB‐bandpass filters (BPFs) with integrated multiple stopband characteristics 2‐13 . Dual passband notches were developed in these UWB filters using stubs acting on the wave cancellation principle, 2,3 slots engraved in the microstrip, 4,5 stepped impedance resonators (SIRs) placed along microstrip 6 or feedline, 7 SIR in the form of E‐shaped resonator, 8 simplified composite right/left‐handed (SCRLH) resonator 9 placed adjacent to microstrip.…”

“…Dual passband notches were developed in these UWB filters using stubs acting on the wave cancellation principle, 2,3 slots engraved in the microstrip, 4,5 stepped impedance resonators (SIRs) placed along microstrip 6 or feedline, 7 SIR in the form of E‐shaped resonator, 8 simplified composite right/left‐handed (SCRLH) resonator 9 placed adjacent to microstrip. Other structures developed dual notches using multiple stubs attached to patch, 10 electromagnetic bandgap structure placed closed to feedline, 11 or combination of stubs with slot 12 or stubs with defected ground structures 13 . Most of them are developed on high‐cost dielectric, 2‐10,12,13 have large size, 2‐13 possess vias that make the geometry complex, 6‐9,11,12 and lack transmission zeros (TZs) 2‐13 …”