Novel Cavity Filters Designed for Easily Integrated With Planar Circuits

This paper presents novel cavity filters designed for easily integrated with planar circuits. The filter has a center frequency of 12.5GHz and bandwidth of 1GHz. The in-band insertion loss is less than 0.5dB, the reflection coefficient is below -18dB, while the stop band rejection from 14 to 15GHz is below -46dB. The design of this filter can be divided into two parts: one is the design of the rectangular waveguide filter; the other is the design of the waveguide-microstrip transition. This proposed filter can make up for the shortcomings of planar filter such as high insertion loss and low power capacity, and can be easily integrated with other planar circuits.