Design Of Microwave Band - Stop Filter

Microwave band-stop filters are widely used in wireless communication systems, and their main function is to provide suppression in the desired band, in order to filter out the interference signals mixed in the desired signals. With the development of wireless communication technology, the study of band-stop filters with better performance, so band-stop filters with smaller volume, better rectangular coefficient, lower insertion loss in pass-band has become one of the key studies.In this thesis, the main research contents are the basic design principle, structure and realization of microwave band-stop filters. Combining cylindrical dielectric resonators, introducing the concept of cross-coupled, we design three band-stop filters, whose main transmission lines are coaxial lines. The main contents of this paper are as follows:1. Introduce the general design principles of narrow band band-stop filters, give the design equations, and design a narrow band band-stop filter based on the equations. The filter is used in a stray test system for mobile phones, and its order is five. Its center frequency is 1.95GHz, stop-band is 1.9475GHz～1.9525GHz, and its stop-band rejection is 30dB. Its resonance unit is metallic rod.2. Introduce the basic theory of cylindrical dielectric resonators; solve dimensions of the required resonator using MATLAB software programming. Design a five-order dielectric band-stop filter using HFSS software. The filter’s center frequency is 5GHz, stop-band is 4.96GHz～5.04GHz, and its stop-band rejection is 35dB.3. Introduce the principle of cross-coupled filters and the extraction method of the coupling matrix. Use MATLAB software programming to get the coupling matrix. Design a four-order dielectric band-pass filter using HFSS software. The filter’s center frequency is 4.99GHz, pass-band bandwidth is 60MHz, and its return loss is greater than 20dB. The frequencies of transmission zeros are 4.9GHz and 5.1 GHz. Obtained the coupling matrix of band-stop filters on the basis of band-pass filters, then use MATLAB software programming to get the band-stop coupling matrix. Design a four-order dielectric band-stop filter using HFSS software. The filter’s center frequency is 4.965GHz, stop-band is 4.93GHz～5.0GHz, and its stop-band rejection is 15dB. The frequencies of reflected zeros are 4.83GHz and 5.1GHz.