| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 95 === The filters play an important part in mobile device of wireless communication, cellular phone, global positioning system (GPS) and signal processing systems. There are many different kinds of specification of wireless communication put into a device in the market that will be usually required and the bandwidth efficiency describes the ability of a modulation technique to accommodate data within a limited bandwidth. The microwave filters are widely used in all radio system in order to discriminate between wanted and unwanted signal frequency.
Traditionally, most of the filters are made by passive networks that such as waveguide, transmission line or discrete lumped elements. But ,due to keep improvement of monolithic microwave integrated circuit (MMIC) process technology, more and more system utilize the active filters and it is the trend to reduce the size of mobile device so it also is the reason to use the active filters to instead of the passive filters. Because the advantages of active filters are small size, compatibility with other ICs and low losses in narrow bandwidth designs.
The thesis plays a important to design a high frequency and narrow bandwidth filters and design concept to be use negative resistance compensation technique to compensate the losses that are made by elements of circuit. We design the resonator that consists of an active capacitance circuit together with a conventional inductor and the active capacitance circuit was made of a field-effect transistor that exhibits negative resistance as well as capacitance. It can, therefore, compensate the loss of an inductor. The element values of the circuit and the computer simulation for the circuit performance are given. The EDA analysis results show that this active filter does have the narrow band property, and gain of more than at center frequency and the attenuation of more than at are achieved. By the way, a 1.9GHz active narrow band-pass filter fabricated on FR4 substrate is implemented to ensure the circuit topology used throughout this thesis is applicable.
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