Optimized Design of a Miniaturized Irregular Spherical Resonator with Enhanced Subtractive/Additive Manufacturing Process Compatibility

RF design and structural optimization of an air-filled spherical-cavity-based miniaturized irregular resonator is presented. The irregular spherical cavity resonator is squeezed non-uniformly in horizontal orientations, and is miniaturized by capacitive loading using a geometrically shaped mushroom-head rod. The design differs from the conventional in the shaping of the cavity geometry, simultaneously taking into account 1) size compactness and miniaturization, 2) enhanced power handling capability, 3) maximized spurious-free region at lowest cost, and 4) most significantly, improved process compatibility with subtractive and additive manufacturing technologies. A prototype of the shaped irregular resonator with a fundamental-mode frequency of 3 GHz is fabricated in size of 0.3 \lambda_{\mathrm{g}} \times 0.2 \lambda_{\mathrm{g}} \times 0.33 \lambda_{\mathrm{g}}$, demonstrating an unloaded quality factor of 2610 and a spuri-ous-free region of >4 octaves. The resonator is a good candidate for new generations of miniaturized coaxial cavity filters with flexible manufacturing schemes.