Study Of The Microwave Passive Circuit Based On CRLH TL

Considerating the real situation of the left-handed transmission line (LH TL), theconcept of composite right/left-handed transmission line (CRLH TL) is introduced.Therefore, the effective permittivity and permeability of the CRLH TL are negative insome frequency band. Compared with the traditional right-hand transmission line (RHTL), the CRLH TL has the properties of forward phase, opposite directions of phasevelocity and group velocity and nonlinear dispersion curve. Due to the abovecharacteristics, it has advantages of small size and novel structure when designing themicrowave passive components such as filters, couplers and phase shifters with CRLHTL. Thus it will have significant value for the miniaturization and integration inmicrowave radio frequency systems by using the CRLH TL to design microwavepassive circuitits.In this paper, we firstly discuss the basic theory of the CRLH TL. The unitstructure of the CRLH TL used to design the microwave passive components in thefollowing chapters is proposed. By using the structure of CRLH TL which is inbalanced condition, an ultra-wideband bandpass filter is designed. In addition, usingtwo CRLH TL structure units coupled with each other and quarter-wavelength of opencircuit transmission lines, a dual-band bandpass filter is realized. Finally, based thecharacteristic of phase forward what the CRLH TL has, a miniaturized hybrid ringcoupler is proposed. After finishing the simulation and optimization of filters and thecoupler, we fabricate and test them. The experimental results of the ultra-wideband filtershow that it has a bandwidth of72.2%and the measured insertion loss is better than2dB in pass band. The experimental result of the dual-band bandpass filter is as follows:the3dB bandwidth of the first pass band is range from5.77GHz to6.88GHz and thesecond pass band has a3dB bandwidth from10.26GHz to10.68GHz. Both the twopass bands have a return loss better than10dB. The miniaturized hybrid ring coupler hasa test result of that when using the port1and port2as the signal input terminalrespectively, the coupler shows a good performance in isolation, reflection and powerdistribution. In this paper, three kinds of microwave passive components are simulated,fabricated and tested. The experimental results show that their work performances aregood and some of them have obvious advantages in small sizes. It is shown that theresearch of using CRLH TL to design microwave passive circuit are considerablysignificant for miniaturization and integration in microwave circuits and systems.