| With the rapid development of communication industry, new wireless communication systems have more stringent requirements to the performance of the existing microwave passive components. As an important component of signal separation, microwave filters should have low insertion loss, high suppression, high power and far parasitic passband. Besides, miniaturization, low cost and short design cycle has gained great attention of the microwave designers nowadays.The study introduces some new structures and the design method of quasi-lumped suspended stripline filters. The main work and contributions are as follows:(1) quasi-lumped elements based on suspended stripline is proposed to realize lumped elements. And the corresponding relation between the two are given.(2) Combining the circuit simulation and the electromagnetic simulation, the initial dimensions of the filters are obtained with certain precision. Using previous frequency deviation in circuit simulation,3D dimensions are more close to the optimal result, at the same time, the design cycle is reduced.(3) Based on (1) and (2), suspended stripline high and low pass filters using suspended stripline are designed. Among them, the low-pass filter adopts the vertically symmetrical structure to reduce the insertion loss; By using suspended stripline, the high-pass filter adopts top and bottom of the coupling to realize the large capacity coupling. And the mixed structure with microstrip and suspended stripline is used to reduce the size.(4) A novel quasi-lumped suspended stripline bandpass filter structure based on the tubular filter circuit is presented to realize ultra-wideband, wideband bandpass filter. And, by using unequal cavity height, this way makes the filter structure smaller. Finally the performance is ideal.(5) According to the comparison between the test results and theoretical analysis, deficiencies of the filter design are found out and the method of further improvement is pointed out. |
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