Modeling of symmetric composite right/left-handed coplanar waveguides with applications to compact bandpass filters

• Published in: IEEE transactions on microwave theory and techniques 2005-11, Vol.53 (11), p.3460-3466
• Main Authors: MAO, Shau-Gang, WU, Min-Sou, CHUEH, Yu-Zhi, CHUN HSIUNG CHEN
• Format: Article
• Language: English
• Subjects: Applied sciences; Band pass filters; Bandpass filter (BPF); Bandpass filters; Bandwidth; Capacitance; Capacitors; Circuit properties; composite right/left-handed (CRLH) coplanar waveguide (CPW); Computer simulation; Coplanar waveguides; Electric, optical and optoelectronic circuits; Electromagnetic waveguides; Electronic circuits; Electronics; Equivalence; Exact sciences and technology; Frequency filters; Inductors; Magnetic devices; Microwave circuits, microwave integrated circuits, microwave transmission lines, submillimeter wave circuits; Microwaves; Oscillators, resonators, synthetizers; Resonance; resonator; Resonator filters; Resonators; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Shunt (electrical)
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/TMTT.2005.857114

This study proposes an equivalent-circuit model for the composite right/left-handed (CRLH) coplanar waveguide (CPW) comprising the series interdigital capacitor and shunt meandering short-circuited stub inductor in symmetric configuration. The new technique for extracting the equivalent-circuit elements of the CRLH CPW, which include inductances, capacitances, and resistances to represent the left-handed, right-handed, and lossy characteristics, is developed based on the effective medium concept. The applications to the compact resonators and filters are presented to emphasize the unique features of the CRLH CPW. A novel CRLH CPW resonator with a 0/spl deg/ effective electrical length at resonance is proposed, which gives a 49.1% size reduction when compared with the conventional half-wavelength resonator at 5 GHz. Based on the zeroth-order CRLH CPW resonators, an inductively coupled two-pole bandpass filter with 5.4% 3-dB bandwidth and 2.7-dB insertion loss at 5 GHz is implemented, and it is 51.4% more compact than the conventional structure. A good agreement among the results of the full-wave simulation, equivalent-circuit model, published data, and measurement demonstrates the effectiveness of the proposed modeling technique. To suppress the higher order harmonic spurious passbands, the electromagnetic-bandgap CPW structures are incorporated into the proposed CRLH CPW filter.