Design Of Numerical Control Hopping Filter Based On Capacitor Array

At the incipient develop stage of microwave technology, application of filters are not very extensive for the reason that the designation of filter is quite a tedious task. However, since the rapid development of the electromagnetic technology, filters become more and more important during many industrial design processes. Microwave filters are wildly used in microwave communication systems, electronic resistance system, missile guidance systems, radar systems and other relating areas. Filter as an important part in many design processes, it can not only be used as a limit of power transmitters in the band that work under radiation, and can also be used to prevent the interference on receiver from other bands signal. In a word, filters are of vital importance for almost all devices that working in the electromagnetic spectrum.In this paper, the background of filter research was analyzed based on the design theory of filter and digital circuit, and completed the designation of a capacitor arraybased NC dance band-pass filter. The Frequency range of this filter is 90~400MHz and divided into two parts, 90MHz~200MHz and 200MHz~400MHz. The insertion loss is within 6dB, VSWR less than 2 and the tuning speed within 10 us. This filter can be applied to all types of high frequency radio receiver as primary filters and can make at least 10 dB improvement in receiver sensitivity. Furthermore, it also can be used as the excitation level input of transmitters that can greatly reduce the noise in the output of the transmitter.In this paper, the whole sample production process was described in detail, including the selection of models, order analysis, experiments and tests. The work in this paper can provides a good reference for the later frequency-hopping filter researcher.Innovations in this paper mainly concentrate on three points.(1)Precision error of capacitance was used to achieve small capacity capacitor. This solution can solve the difficulty in small capacity capacitor achievement.(2)In order to design the filter in a smaller space, the multilayer was used. This also can avoid the effects of electromagnetic interference on the radio frequency signals.(3)Impedance transformer was used in this paper to do the impedance change. This designation can solved the difficulty that device value cannot be too large or too small.