Compact Wideband Bandpass Filters Using Stepped-Impedance Resonators and Interdigital Coupling Structures

• Published in: IEEE microwave and wireless components letters Vol. 19; no. 9; pp. 551 - 553
• Main Authors: LIANG, Cheng-Hsien, CHANG, Chi-Yang
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.09.2009; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Band pass filters; Banded structure; Chebyshev approximation; Circuit properties; Coupling circuits; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency filters; Impedance; Interdigital coupled lines; Joining; microstrip; Microstrip filters; Microstrip resonators; Microwaves; Noise levels; Oscillators, resonators, synthetizers; Passband; Resonator filters; Resonators; Simulation; stepped-impedance resonator (SIR); Strips; Wideband; wideband bandpass filter (BPF); Resonator; Wide band circuit; Stepped impedance device; Chebyshev filter; Coupled line; Compact design; Interdigital coupled lines; Implementation; microstrip; Simulation; wideband bandpass filter (BPF); Band pass filter; Passband; Impedance; stepped-impedance resonator (SIR); Interdigital configuration
• ISSN: 1531-1309; 1558-1764
• DOI: 10.1109/LMWC.2009.2027060

This letter proposes a microstrip lambda/4 interdigital stepped-impedance resonator whose impedance ratio can be very low and coupling strength between adjacent resonators can be very large. On the basis of the proposed structure, one four-pole Chebyshev and one four-pole generalized Chebyshev filter with 0.05 dB equal-ripple bandwidths of 48% and 46%, respectively, are designed and fabricated. Both implemented filters have a compact size, a wide passband, a wide upper stopband, and a high spurious passband at near 5.1 times the center frequency. Good agreement between measurements and simulations is observed.