The Design Of Microstrip Bandpass Filter Based On ADS

With the rapid development of digital TV, a complete set of theories and methods has come into being for the purpose to covert the continuous time signal into discrete time signal. A signal distortion will be caused due to the fact that each kind of signal will be interfered by the external environment during each link of transmissions.While in most cases, the distortion is so severe that the effective information signals would be deeply buried into the noises. However, The filter can effectively filtrate the frequency point having a specific frequency or any frequency else other than its frequency so as to obtain an electrical signal with a specific frequency. In short, a well-designed filter can filtrate the unusable signal in the transmission signal with a given parameter value and frequency value, so as to exclusively allow the usable signal to pass through the transmission device. The contribution presented in this thesis is to design a parallel coupled microstrip line band pass filter and a wide band microstrip filter, after the specific bandwidth and parameter values were set, they had been made with reference to ADS aided design software by Prof. Huang Yulan. The former microstrip band pass filter had a 2.1GHz center frequency and a 50 ? system characteristic impedance, its frequency range within passband was 2.0GHz-2.2GHz, the in-band attenuation was less than 1.5dB with an attenuation more than 20 dB at 1.8GHz and 2.4GHz. the latter product was only half-finished, to which errors had occurred in the final simulation stage, many attempts of debugging has been made but all failed. However, a relevant analysis on the cause of errors has been conducted in the later part, hopefully, a final conclusion can be arrived in the following part.The first chapter of this thesis outlines the development process and research significance, and introduces the related design principles.In the second chapter, the theory of parallel coupled- microstrip is introduced.Based on the theoretical basis of the second chapter, the third chapter is to design a microstrip bandpass filter with center frequency at 2.1 GHz and relative bandwidth of9.5% by using the parallel coupled microstrip structure. At the same time, in order to get the superior performance of parallel coupled microstrip band pass filter, ADS is used to make the circuit schematic and layout, and at last optimize the filter structure.In the fourth chapter, we first introduce the related theory of stepped impedance resonator, and then design a wideband bandpass filter based on ADS.