LAUSR

This paper proposes an enhanced model for a re-entrant coaxial resonator and analyzes the capacitance behavior between its different sections and the $Q$ -factor, for which mathematical expressions are derived. This model makes it possible to carry out a geometric optimization to minimize the volume of a compact coaxial resonator. Theoretical conclusions are compared with electromagnetic simulations and an optimized symmetrical six-pole re-entrant coaxial resonator bandpass filter prototype is designed and fabricated to illustrate the optimization.