Automatic Measurement And Laser Trimming Of Microwave Dielectric Resonator

New dielectric ceramic materials have many advantages, such as high permittivity, low dielectric loss and high temperature stability. Microwave dielectric resonators made of dielectric ceramic have been widely utilized as key components in microwave circuits. They play a key role in reducing size, decreasing loss and improving stability of circuit. Microwave components fabricated from dielectric resonators, such as filters, antennas and frequency stabilized oscillators, have been widely applied in such areas as mobile communications, satellite broadcast, GPS and so on.Resonant frequency is a key parameter of microwave dielectric resonator. Computation of resonant frequency has been investigated with many numerical methods, such as effective dielectric constant method, mode-matching method and finite-difference method. A novel numerical method is developed to calculate resonant frequency and quality factor of dielectric resonator placed in an axial symmetry structure. The method adopts the equivalent functional of Helmholtz equation and its boundary conditions, incorporating with MATLAB PDE (Partial Differential Equation) toolbox. For verification of the new method, the resonant frequency and quality factor of a dielectric resonator placed on a substrate in MIC (Microwave Integrated Circuit) are calculated. The results are in agreement with those presented in literatures applying different methods.Tuning of resonant frequency is a necessary procedure in microwave circuit manufacture. Many frequency tuning methods presented in literatures are introduced. For investigation of circuit performance related to frequency tuning range, the resonant frequency and conductor quality factor of dielectric resonator in MIC with tuning screw are calculated. The frequencies of dielectric resonators after laser trimming procedure are numerical calculated with finite element method. Laser trimming of dielectric resonator is proved to be feasible and of great advantage.Frequency tuning should be automatic, quick and precise in dielectric resonator manufacture. An automatic system is developed to measure and trim the resonant frequency of dielectric resonator by laser automatically. The whole procedure is realized via hardware and software design. By applying different software, the fixture is also applied to measurement of temperature coefficient of dielectric resonator, which highly improves the efficiency.