Parameter extraction of the coaxial resonator based on the SOLT calibration method

A 4.6GHz voltage-controlled oscillator (VCO) using a coaxial resonator (COAX) with high quality factor can be used as an ultra-low phase noise microwave signal source in the coherent population trapping (CPT) cesium atomic clock to achieve the closed-loop locking. In order to design and simulate the VCO more accurately, a proper model considering practical operating environment of the COAX is needed. Firstly, this paper analyzes the 12-term SOLT error model and derives the real S parameters of the device under test (DUT), then the SOLT calibration standards are designed according to the specifications that they should meet, and the accuracy and reliability of them are verified by testing some inductors with known characteristics. Finally, the COAX is measured by the same way and its actual equivalent circuit model which considers the parasitic effects of the operating environment is built on the basis of the test data so that reliability of the simulation results of the VCO designed with the COAX model can be improved greatly.