Broadband Micro-coaxial Bandpass Filter at Ka-Band

This paper presents a broadband bandpass filter at Ka-band based on micro-coaxial structures. Micro-coaxial components get the advantages in small size, low insertion loss and high stability, which is contribute to the integration and design of passive devices. The air-filled micro-coaxial transmission lines are used to design the proposed bandpass filter. It is composed of six paralleled resonant units and five quarter-wavelength transformation lines. Transition structures are designed to connect with other devices and facilitate the measurement. The filter designed are conducive to Ka-band communication system with their compact structure and good performance. The center frequency of the filter designed is 28.4 GHz. The measured minimum insertion loss of the filter is as low as 0.601 dB and the 3-dB bandwidth is as broad as 56.9%, which shows good consistency with the simulation.