Design of Microstrip Low-Pass Filter Based on Six-Slit-Ring DGS
A novel six-slit-ring defected ground structure (DGS) is presented in this paper. The location of the slit can shift the resonant frequency without changing the overall size of the DGS and its adjustment range can reach 8.81 GHz. By cascading three identical six-slit-ring DGS unit cells, a microstrip low-pass filter (LPF) can be realized. Its 3dB cutoff frequency is 7.27 GHz. The in-band insertion loss is below 0.35 dB and the stop-band width with 20 dB attenuation is over 8.12 GHz. To improve the out-of-band rejection of the filter, shunt branches were added on both sides of the microstrip line. Its 3 dB cutoff frequency is 8.285 GHz. The insertion loss is less than 0.81dB in the pass-band. The stop-band rejection is better than -40 dB at 11.36-20 GHz and the size of the filter is only 28 mm by 11 mm. The simulation results show that the proposed novel six-slit-ring DGS microstrip LPF has the characteristics of compact size, flexible adjustment, flat pass-band, wide stop-band and high selectivity.
Microstrip stepped‐impedance hairpin resonator low‐pass filter with defected ground structure
In this paper, a new microstrip stepped‐impedance hairpin resonator (SIR) low‐pass filter (LPF) using a defected ground structure (DGS) is proposed. The proposed SIR hairpin low‐pass filter using DGS provides a very sharp cutoff frequency response with low insertion loss. Furthermore, the SIR hairpin low‐pass filter can provide attenuation poles for the wide‐stopband characteristic due to the resonance characteristic of the DGS. Design parameters for the SIR low‐pass filter are derived based on stepped‐impedance theory and the equivalent‐circuit model for the DGS. The experimental results show excellent agreement with the theoretical simulation results. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 405–408, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21364
Improved Microstrip Folded Tri-Section Stepped Impedance Resonator Bandpass Filter using Defected Ground Structure
─ In this paper, a study of a microwave microstrip bandpass filter (BPF), based on folded tri-section stepped impedance resonator (FTSIR) and defected ground structure (DGS) is presented. Based on the resonance characteristics of a stepped impedance resonator (SIR), the first spurious resonant frequency can be tuned over a wide range by adjusting its structure parameters. The SIR bandpass filter is designed to have a quasi-elliptic function response and a wide upper stopband. Furthermore, five ground slots (DGS) are used in order to omit the first spurious resonant frequency. Compared to similar microstrip filter without defected ground, the simulated performances of this novel structure indicate some functional advantages. To validate the design and analysis, a prototype of the bandpass filter with DGS was fabricated and measured. It is shown that the measured and simulated performances are in a good agreement. Index Terms ─ Defected ground structure (DGS), folded tri-section stepped impedance resonator (FTSIR), microstrip bandpass filter.