Design and Development of Microstrip Lowpass Filters for RF Communications

Abstract

The majority of electrical circuits used in wireless communication are now frequency newlinedependent. Each application has its own set of frequency bands that it uses for signal newlinepropagation and transmission. Filter circuits with a passband and stopband range of newlinefrequencies choose those frequencies. There is a risk of high frequency noise newlineinterference in a network of wireless electronic circuits. Lowpass filters that meet newlinespecific frequency parameters, such as sharp roll-off level, larger stopband extension, newlineminimal losses, and minimum normalised circuit size, are important for this function. newlineSeveral lowpass filter models for planar printed circuit boards are designed, newlinefabricated, and measured in this thesis. The physical models are made up of cascading newlineirregularly shaped resonators that provide a coupling environment. newlineThe greatest accomplishments in frequency characteristics among all the produced newlineprototypes are the maximum roll-off level acquired using a dual split resonator newlinestructure and 26th harmonic suppression accomplished using a poly-resonator inclined newlinestepped impedance configuration. Lowpass filters with single band bandpass newlineresponses are also constructed in a single circuit and obtain large fractional newlinebandwidth. Utilising some minor coupling modifications in the same circuit, the newlinecombined lowpass-bandpass response are accomplished with 24 percent fractional newlinebandwidth. In the integration of lowpass-bandpass filter, the suspended microstrip newlinemodel of lowpass filter for attaining higher Q-factor is also constructed. The newlineRT/Duroid 5880 outperforms FR4 substrates in terms of roll-off characteristics, newlinestopband performances, and loss factors (return loss and insertion loss).