The Design And Research Of Stub-loaded Microwave Filters Used In Wireless Communication

Recently, with the rapid development of the wireless communication technology, thefrequency channel distributed to multiple communication systems becomes narrow. As aresult, the filters of transceiver are required to have a better performance. And it becomes animportant research subject to improving the performance through various methods andstructure.A stub-loaded resonator can generate two modes, which has important application inminiaturization. Loading stub will separate even and odd mode resonance frequency and itwill only change some mode, while another mode frequency is mainly determined byresonator. This feature plays an important role in adapting passband performance.Stub-loading technology can also improve the filter stopband performance. In order to furtherperfect the performance index of filters, we also do some research on slotline and microstripstructure. Slotline structure will greatly improve filters’ power capacity and microstrip-slotlinestructure makes full use of the space of the substrate which can significantly reduce the size ofthe filter. Therefore, we develop three bandpass filters using stub-loading technology withslotline, microstrip and microstrip-slotline structure, respectively. This paper mainly includesthe following contents:First of all, the article puts forward the basic concept of the filter, and simply introduces thecommon index parameters in filter design. The classical method of filter design is described,that is using low-pass prototype to design filter. In addition, this article expounds the detail ofbutterworth, chebyshev and elliptic function low-pass prototype filter, and simply states howto get the general filter response from the low-pass prototype filter by using the frequency andimpedance transformation.Then, T-shaped stub-loaded microstrip and slotline are introduced and analyzed in thisarticle. Also, a dual-band bandpass filter is developed by using T-shaped slotline stub-loadedresonator. In addition, with T-shaped stub-loaded and short circuit stub-loaded microstrip, acompact dual-band filter is designed. Passband performance of the two filters can beconveniently adjusted by the loaded stub.At last, this paper proposes a microstrip-slotline tri-band filter by using the proposedmicrostrip dual-band filter and a T-shaped slotline resonator on the ground.