DESIGN OF AN ADAPTABLE MICROSTRIP FILTER IN S-BAND FREQUENCY.3

摘要

Satellites play a vital role in the field of communication. Satellite receivers at microwave frequencies are being used for a large number of purposes. A satellite receiver without adequate filtering at its input is able to pick up signals at two different frequencies simultaneously; the desired frequency and the image frequency. Hence there is a need for the installation of the preselect filter at the RF stage before mixing. The aim of this project is to eliminate this image frequency and design a preselect filter in the RF (Radio Front) stage. At S-band microwave frequency (2 GHz to 4 GHz), the lumped components cannot be used due to distributed effects. Also, for the compactness of the filter, the distributed components are being used in microwave frequencies. Hence the coupled stage of microstrip filter with good frequency response is adopted in this paper. The filter design is carried out by using a simulation software namely, ADS (Advanced Design System). Only the coupled stages of a microstrip filter cannot reduce the aliasing effect, hence extra strict requests are made on the insert loss and standing wave ratio of the received signal in a satellite receiver. This filter is designed at the center frequency of 2.491 GHz. Only on optimization, the filter achieves minimum aliasing interference at the desired center frequency. This is done by the GOALs and OPTIM controller embedded with ADS.