Abstract:

In order to realize a relatively wide impedance matching bandwidth,the traditional composite right/left-handed（CRLH） transmission line（TL） must operate in a balanced state,in which a seamless transition exists between the left-handed and the right-handed passbands.However,it is difficult to satisfy such a balanced condition in practice.To solve this problem,a novel simplified CRLH（SCRLH） TL structure is proposed.The novel structure is similar to the bandpass filter in property,that is,the attenuation constant keeps zero with a continuous and smooth characteristic impedance distribution within the passband, the bandwidth may be wideband or even uhrawide band, and the characteristic impedance is respectively a real number within the passband and a pure imaginary with the inhibition of electromagnetic wave propagation outside the passband. Then, a practical microstrip SCRLH TL structure with the center frequency locating at 6.85 GHz and the relative bandwidth of 110% is implemented by adopting the microstrip high/low-impedance lines and the grounded stub, and its transmission properties obtained from full-wave/circuit simulation analyses and experimental measurement accord well with each other. In addition, the dispersion characteristics extracted from the above-mentioned transmission properties approach the theoretical ones well, which justifies the feasibility of the novel SCRLH TL structure and its potential application prospects in the design of ultra-wideband filter.

Key words: simplified composite right/left-handed transmission line, phase shift, attenuation, impedance characteristic, ultra-wide band, microstrip implementation