Composite Right/left-handed Coplanar Waveguide Research Articles

Analysis and Design Guidelines for Wideband CRLH SRR-loaded Coplanar Waveguide

This article presents a novel lumped-element equivalent circuit model for split-ring resonator (SRR)-based composite right/left-handed (CRLH) coplanar waveguide (CPW). The proposed model has closed-form expressions in terms of the parameters of the constituent transmission lines and is valid over a wide frequency range. This article also presents a novel slotline to coupled microstrip (MS) line $E$ -plane T-junction. Based on the circuit model and the proposed junction, systematic design procedures for ultrawideband balanced SRR-based CRLH CPW unit cells that benefit from the geometry of the unit cell and do not rely on adding extra components or parametric iterations are developed. This article also explains the layout constraints and presents alternatives to realize wideband designs. Two CPW unit cells using SRR and edge-coupled (EC) SRRs are designed, fabricated, and characterized. Simulations, which are in good agreement with measurements, show that the operating bandwidth can reach 97% and 78.21% for the two cells, respectively.

Resonant-type balanced composite right/left-handed coplanar waveguide structure

A resonant-type balanced composite right/left-handed (CRLH) coplanar waveguide (CPW) structure based on split ring resonators (SRRs) is presented. An equivalent circuit model is used to describe its complicated behaviour. As the higher cutoff frequency of the left-handed (LH) band and the lower cutoff frequency of the right-handed (RH) band are identical, a continuous transition from LH band to RH band without a bandgap can be achieved. In addition, because of the presence of SRRs, the resonant-type balanced CRLH CPW structure exhibits a very sharp cutoff in the lower edge of the transmission band.

Asymmetric Dual-Passband Coplanar Waveguide Filters Using Periodic Composite Right/Left-Handed and Quarter-Wavelength Stubs

A novel dual-passband coplanar waveguide (CPW) filter periodically loaded with the composite right/left-handed (CRLH) short-circuited stubs and the quarter-wavelength open-circuited stubs in asymmetric configuration is presented. The unit-cell equivalent circuit of the periodic structure in conjunction with Floquet's theorem is employed to find the propagation characteristics of passband and stopband regions. Unlike the conventional quarter-wavelength transmission-line inverter suitable only for a narrow frequency range, the dual-band inverter is adopted in the dual-passband filter to achieve a better frequency response within two operating bands. The performance of the 2.4/5.8-GHz third-order CRLH CPW dual-passband filter with 52% and 23% bandwidths is measured and validated by full-wave simulation. Two arbitrary passband regions are presented and the stopband within the passbands can be controlled by varying the length of open-circuited stub, supporting the flexibility and compactness of the proposed dual-passband filter

A Novel 3-dB Directional Coupler With Broad Bandwidth and Compact Size Using Composite Right/Left-Handed Coplanar Waveguides

A wideband composite right/left-handed (CRLH) coplanar waveguide (CPW) coupler with 3-dB coupling value and quadrature phase difference is presented. Compared with the conventional edge-coupled CPW coupler, this symmetrical structure, consisting of a gap capacitor, a broadside-coupled capacitor, and a meandering short-circuited stub inductor, achieves wider operating bandwidth and larger coupling level. The 3-dB CRLH CPW coupler with 0.7mm spacing between coupled lines exhibits an amplitude balance of 2dB and a phase balance of 900 plusmn 50 from 3.2 to 7.6GHz. The coupled-line length and the port impedance of the proposed structure are approximately lambda/4 and 50Omega, respectively, which makes it more compact than the cascaded CRLH microstrip coupled-line coupler. To characterize this structure, the equivalent circuit model including the unique coupling mechanism within CRLH CPWs is established and verified by measurement. The signal with less dispersion on output ports is demonstrated based on the standard deviation of group delay time

Composite right/left-handed coplanar waveguide band-pass filter using capacitively-coupled zeroth-order resonators

Design and performance of a coplanar waveguide (CPW) bandpass filter (BPF) using composite right/left-handed (CRLH) zeroth-order resonators have been studied. The unit cell of the CRLH CPW consists of a series interdigital capacitor and two shunt stub inductors embedded between two sections of CPWs. The Bloch analysis is applied based on the S parameters to derive the characteristics of the eigen modes (Bloch modes), from which the right/left-handed frequency band and the zeroth-order resonant frequency are clearly determined. Then, the susceptance slope parameter of the resonator is extracted and the admittance (J-) inverters are introduced to synthesize a capacitively coupled CPW BPF. The measured performance agrees with the simulated one. They show that the size of the filter is greatly reduced (more than 60%) when compared to a conventional structure.

Broadband Composite Right/Left-Handed Coplanar Waveguide Power Splitters With Arbitrary Phase Responses and Balun and Antenna Applications

This study presents novel coplanar waveguide (CPW) power splitters comprising a CPW T-junction with outputs attached to phase-adjusting circuits, i.e., the composite right/left-handed (CRLH) CPW and the conventional CPW, to achieve a constant phase difference with arbitrary value over a wide bandwidth. To demonstrate the proposed technique, a 180/spl deg/ CRLH CPW power splitter with a phase error of less than 10/spl deg/ and a magnitude difference of below 1.5 dB within 2.4 to 5.22 GHz is experimentally demonstrated. Compared with the conventional 180/spl deg/ delay-line power splitter, the proposed structure possesses not only superior phase and magnitude performances but also a 37% size reduction. The equivalent circuit of the CRLH CPW, which represents the left-handed (LH), right-handed (RH), and lossy characteristics, is constructed and the results obtained are in good agreement with the full-wave simulation and measurement. Applications involving the wideband coplanar waveguide-to-coplanar stripline (CPW-to-CPS) transition and the tapered loop antenna are presented to stress the practicality of the 180/spl deg/ CRLH CPW power splitter. The 3-dB insertion loss bandwidth is measured as 98% for the case of a back-to-back CPW-to-CPS transition. The tapered loop antenna fed by the proposed transition achieves a measured 10-dB return loss bandwidth of 114%, and shows similar radiation patterns and 6-9 dBi antenna gain in its operating band.

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

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.