Ceramic coaxial resonator filter in a CubeSat system

Abstract

RF and microwave filters can be implemented using ceramic coaxial resonators. This technology has been widely employed in nanosatellite communications systems recently, owing to its large quality factor (Q), permitting them to have low loss and narrow bandwidth. Features such as high selectivity, high power handling, excellent rejection, and low passband insertion loss are just a few of the key performance areas offered by ceramic coaxial resonators. This feature makes them suitable for use in bandpass filters. Applications with demanding specifications requiring low volume and mass make use of this technology. Fulfilling the required performance goals can be challenging, given the size and weight restriction. Difficulties such as finding the correct length of resonators and the coupling capacitors’ structure to meet the size restriction, limit the type of ceramic coaxial resonators to use. This thesis presents the design of a bandpass filter using ceramic coaxial resonators, which provides evidence of the concept for F’SATI’s future needs. This design will be used in an imminent space mission and the intention is to mount the bandpass filter in the receiver communications system. An intensive investigation was conducted into the use of filters for nanosatellite communication systems. The Chebyshev LC ladder low pass prototype was used to derive the conventional bandpass filter. Thereafter, the coupled resonator bandpass filter was derived using the conventional bandpass filter topology combined with the admittance inverter. Following this, using the ceramic coaxial resonators datasheet and information provided by the manufacturers, the coupled resonator bandpass filter was converted into a 3D model for further simulations, using CST Microwave Studio®. The ceramic coaxial resonator filter fabricated using Rogers’s material provided satisfactory results at its operating frequency between 2.2 GHz and 2.3 GHz. A radiation level test was performed on the filter to justify the use of the metallic enclosure. The test presented a low level of radiation measured at the filter operating frequency (2.25 GHz). The filter was also subjected to temperature cycling.