Miniaturized High-Performance Cube-Shaped Filter Made up of Quasi-TM010 Mode Dielectric-Loaded Cavities

Abstract

In this paper, a compact quasi-TM010 mode dielectric-loaded bandpass filter with 8th-order pseudoelliptic filtering function and symmetric positioning of 4 transmission zeros is analyzed and designed. The resonant frequency and field components of quasi-TM010 mode of a cylindrical dielectric resonator (DR) were first calculated and simulated. Compared to the pure TM010 mode, the unloaded Q factor of quasi-TM010 mode can increase by 3000 to more than 8000 and then the dimensions of the single DR at 2.595GHz are \pi \times 34^{2}\times 20 mm3 (using \varepsilon -{\mathrm {r}}= 45 ). The magnetic coupling and electric coupling between dielectric-loaded cavities are studied and the dielectric window is innovatively proposed to generate electric coupling and to avoid the use of metallic probes that are cumbersome to assemble. In final, a quasi-TM010 mode double-layer filter with two pairs of symmetric transmission zeros is designed according to the cubic-like topology and fabricated and tested which exhibits close agreements between the simulated and measured results demonstrating the advantages of low insertion loss, very close-To-band rejections and compact configuration. The proposed filter has great potential for development in 5G mobile communication systems and microwave radar communication systems.