A Compact Lowpass Filter with Ultra Wide Stopband using Stepped Impedance Resonator

Abstract

In this paper, a compact asymmetric-shaped microstrip lowpass filter (LPF) using a stepped impedance resonator is presented. An ultra wide stopband with high attenuation in the stopband region, within very small circuit area is achieved for the proposed filter using novel asymmetric structures for resonator and suppressor. The transmission zeros of the resonators can be adjusted as a function of high impedance and low impedance microstrip lines, and due to the asymmetric structure, the proposed suppressing cell can be located within the resonator structure without occupying a large area. For verification, a 2.92 GHz LPF is designed and fabricated. The experimental results, in comparison with the other LPFs, show that the proposed LPF has significant advantages in the stopband characteristics with acceptable sharp roll off. The measured passband insertion loss is below 0.1 dB, and the rejection band over-20 dB is obtained from 3.42 GHz to 36.2 GHz. The size of filter corresponds to compact electrical size of 0.156 λ g × 0.128 λ g , where λ g is the guided wavelength at 2.92 GHz. Also, the maximum variation of the group delay in 80 percent of the passband region is only about 0.2 ns.

Wide Band Stop Response Using Interdigital Capacitor/CSRR DGS in Elliptical Microstrip Low-Pass Filter

“…is observed for HL-ELPF with mitered U-shaped line, which is shown in Figure 10 The characteristics of low-pass filter designs reported in this work are summarized in Table II as discussed in this section and previous section. The LPF performance parameters like, roll-off rate (β), relative stop-band (RSB) bandwidth for -20 dB return loss, normalized circuit size (NCS), and figureof-merit (FOM) are calculated from the known relations [9,18] and comparison of last three designs is given in Table III.As given in Table III, the performances of Design 6 and Design 7 are comparable to the earlier reported filters [8,19,21,31]. In addition, the proposed filters in this work achieved wide stop-band of 8.15 GHz with high attenuation (> -20 dB) in the stop-band with the compact circuit size.…”

“…Most of these designs either suffer with low attenuation (<20 dB) range in the stop-band or have larger size. In addition, for better roll-off rate as well as compactness, an elliptical-function response is used in many LPFs which are based on several structures, such as stepped-impedance hairpin resonator [8], tapered resonator [12], slit-loaded tapered compact microstrip resonator cell [13], symmetrically loaded radial-shape patches and meandered transmission line [14], triangular patch resonators and radial patch resonators [15], symmetrically loaded triangular and high-low impedance resonators [16], P-shaped resonators [17], novel asymmetric structures for resonator and suppressor [18], wide stop-band using tri-section stepped impedance resonator [19] etc.…”

Compact tunable U-Hi-Lo low pass filter using quasi C-shaped stubs

“…All previous demands make the RF filters compatible with the modern wireless technologies [1,2]. There is an enormous demand for designing and implementing a low pass filter with a pass-band covering the L-band (1-2 GHz), S-band (2-4 GHz), and C-band (4)(5)(6)(7)(8). Microstrip low pass filters with advanced features have been widely utilized in various technological aspects and due to their importance; many techniques have been used to obtain the required features.…”

“…One of the techniques used was cascaded technique where resonators are placed in horizontal or vertical topology, but it needs a larger occupied area in addition to larger coupling between resonators is occurred [3,4]. Other techniques can also be used to improve the behaviour of the low pass filter such as stepped-impendence resonators (SIR) [5,6], defected ground-plane structures (DGS) [7][8][9][10], combination of DGS and DMS [11], interdigital line resonator (ILR) [12], and meander-loop resonator [13], meander inductor [14,15], complementary split-ring resonator (CSRR) [16], and combination of SIR and DGS [17].…”

Design of a novel microstrip four-channel diplexer for multi-channel telecommunication systems

“…Microstrip devices with improved performance are widely used in communication applications because of their planer structure, low profile, light weight, moderate efficiency and ease of integration with active devices [3][4][5][6][7][8][9][10][11][12][13][14][15]. Multi-frequency antennas commonly need multi-channel diplexers and multiplexers to separate signals from crowded frequency bands.…”