DIPLEXER DESIGN USING MICROSTRIP LINES

Abstract

ABSTRACT In this Project, a new microstrip structure is proposed and studied to design microstrip diplexer. Modern wireless communication systems demand RF devices operating in multiple frequency bands. A diplexer, is an essential component in multi-service and multi-band communication systems, is a three terminal device that separates the input signals to two output ports. A well designed diplexer should have low cost and high performance. To demonstrate the design ideas, the equivalent circuits of the proposed Diplexer are built and studied and then Simulated in ADS software tool. It is found that the different loads on different positions of the proposed half-wavelength resonator make the resonator have different features, which will easily control the characteristic of the diplexers. And here, resistor, open stub, and shorted stub are used as loaded elements. It is found the resistor loaded on the centre of the microstrip line resonator can extremely reduce the unloaded quality factor of even-mode resonant frequency, which can be used to suppress the harmonics of the diplexer. The loaded open stub not only can reduce the size of the diplexer, but also control the frequency ratio between the fundamental frequency and second harmonic of a resonator, which can increases the frequency ratio between the two pass bands of the diplexer. As for the loaded shorted stub, it can enlarge the size of the diplexer. Here in our project diplexer is designed with only four stubs and two transmission lines. The transmission line used has the same characteristic impedances. While it has a good transmission performances and good isolation between the output ports. Here microstrip diplexer is designed and simulated in ADS software tool. The Diplexer is designed to operate with 2.4 GHz and 2.85GHz frequencies. Different results for the diplexer have been found in terms of S parameter. Which shows different characteristics of the device. Here a good agreement with the calculated results and the simulated results is achieved.