Zihang Qi

Design of triangular microstrip dual mode filter based on the coupling matrix synthesis method

This paper presents a new four poles dual-mode of the triangular microstrip filter with asymmetrical input and output filter feed. Cameron theory is applied to synthesize coupling matrix and design the filter. The filter is optimized by using the Cauchys method, which is used in the S band with 200MHz pass-band filters of orders two and four are successfully designed. The results show that the insertion loss is less than 2 dB, the return loss is more than 20dB, even no higher order mode interference in the pass-band. The improved structure has a better band rejection performance. The designed filter is now being fabricated.

A compact combline filter design and optimization using the Cauchy method

A 10th-order direct-coupled combline filter is designed and optimized using the Cauchy method in this paper. The fabricated filters tuning procedure is via a real-time Cauchy extracting system. The filter is synthesized based on Chebyshev low-pass prototype with a fractional bandwidth up to 15.2% centred at 889.4MHz. The average insertion loss of the fabricated filter is lower than 0.72dB. The measured results are obtained in good agreement with the predicted ones.