Short-circuit Stub In The Waveguide Filter

Recently, with the rapid development of the microwave and millimeter-wave technology, microwave apparatus are facing a huge market in many fields, such as microwave communication, navigation, and electro-counterwork. Moreover, the frequency channel distributed to multiple communication systems becomes narrow because of the limit of the frequency resource. As a result, the apparatus used for microwave and millimeter- wave receiver and transmitter are required to have a good performance to decrease the insertion loss and the noise interference. It becomes an important research subject to improving the performance of the filters through any methods.Shorting stub plays an important part in increasing rejection and the small size of filter. In this paper, new methods, new configurations and new technique of shorting stubs will be analyzed and studied. The paper includes the following content:First of all, a systemic research of waveguide E-plane shorting stubs will be done based on the theory of transmission line. It consists of the relationship between the resonance frequency and the dimension of the shorting stub; the relationship between the band-width, Q factor and the coupling aperture; the application of capacitance-loaded technology.On the research of single stub, multiple stubs are studied. These cascade stubs have different response with different length of connecting waveguide. They can be used to improve the performance of the filter.Then, the method using stub resonators to improve the rejection of the filter will be proved on the circuit simulation software ADS. By studying the equivalent circuit of each element and the new structure for the compact shorting stub filter design, four kinds of filters are designed, fabricated, and measured. They are 6-order shorting stubs waveguide band-stop filter, 4-order waveguide pass-band filter, 6-order sharp rejection band-pass filter and 20-order coaxial shorting stubs band-stop filter.At last, by studying the effect brought out by the fabrication error, we suggest a new method to revise the error. According to the experience of filter design and measurement, a speedy and effective means for the debugging of the filter is proposed.