Design And Research Of Notched Ultra-wideband Filter

It is difficult to select the materials in the designs of the THz devices, because most of the materials would lead to high loss, high absorption and high dispersion in the transmission of the THz wave. The metamaterials can realize the integration and miniaturization of the THz systems bringing new hope to the researches of the THz devices. Based on the metamaterials, we have finished three aims: the design of a bi-directional tunable terahertz modulator; the design of single band-stop and dual band-stop terahertz filters; the design of single band-pass and dual band-pass terahertz filters.After the US Federal Communications Commission(FCC) issued ultra-wideband communications standards in February 2002, ultra-wideband wireless communication technology got a lot of attention in related fields with its high data transfer rates, low loss, good flexibility and mobility. Ultra-wideband filter is a very important element in this system, it will have a significant impact to the system’s performance. The ultra-wideband bandpass filter with notch in this article is based on the stepped impedance resonator structure and cross coupling structure, which with low cost, small size and better performance. The structure which produces ultra-wideband is composed by the stepped impedance resonators which load quarter-wavelength short circuit stubs.WLAN, Wimax and satellite access which are in the presence of ultra-wideband frequency band have already been used, and therefore ultra-wideband filter with multi-notches are needed. The notches are got by loading coupled resonators and embedded stubs. a single notch is achieved by loading coupling structure in the interdigital structure, dual notches or even three notches are got by embedding short circuit structure in the ultra-wideband structure in this paper.The main contents of this paper are:1. An ultra-wideband filter with a single notch which loads a folded open stubs out of the interdigital filter structure is designed. Analysis resonator’s transmission zero and resonance characteristics based on microwave network theory and multimode resonator theory. calculated length of the microstrip line’s coupling portion and the length of the resonator with ADS. By adjusting the width of the coupled slot, the length of the coupled microstrip lines, and the groove’s geometry in the resonator to meet the requirements of the ultra-wideband bandpass filter. Loading a folded open stubs out of the interdigital structure to produce a single notch, and getting a notch at WLAN by adjusting the open stub’s geometry. After the actual processing and testing, the filter’s in-band ripple characteristics meet the requirements, the sideband characteristics are good, the coupling structure can effectively block the transmission of the WLAN.2. By embedding double short circuit stubs structures to produce dual notch. Four short circuit stubs ultra-wideband bandpass filter is designed, and analyzed several common structure which are used to generate stopband and contrasted their differences. Finally, I choose the method which generates notches by embedding open stubs. By adjusting the gap width between the open stubs and the ultra-wideband bandpass filter and the open stubs’ physical size to make the resonant frequency to the notch frequency position. A dual notch UWB filter is achieved. The simulation results and processing measured of the filter have a good match, insertion loss and return loss is good.3. Embedding three short circuit stubs structure is designed to produce three notches. Regarding the optimized four short circuit stubs ultra-wideband bandpass filter as the basic structure in which embed three λ/4 open stubs, The three open stubs are designed to the form of cross coupling, which can effectively increase the coupling strength. By adjusting the gap width between the open stubs and the ultra-wideband bandpass filter and the open stubs’ physical size to make the resonant frequency to the notch frequency position. The simulation results and processing measured of the filter have a good match, insertion loss and return loss is good.