An Odd Order Elliptic Function Narrow-Bandpass Microwave Filter

Multiple coupled high Q cavities can be used to generate even order elliptic function bandpass filter responses. This paper describes the design of odd order elliptic function bandpass filters using a minimum number of cavities connected by simple and resonant coupling elements. Experimental results of a 3-pole, 20-MHz bandpass waveguide cavity filter centered at 3890 MHz correlate well with theory.