A numerical model of directional couplers for ECRH systems and its validation

Real-time power measurement of the Electron Cyclotron (EC) wave is essential for the Electron Cyclotron Resonance Heating (ECRH) system operation. Directional couplers integrated into the miter bend can realize real-time EC wave power measurement. To monitor the operating status of the ECRH system, we need to design directional couplers. In the design process, a numerical model and corresponding program have been developed. To validate the reliability of the model, 23-hole and 27-hole directional couplers have been designed and high-power tests at the frequency of 105 GHz have been carried out. Deviations between the measured coupling coefficients and the theoretical values are about 0.6 dB and 5 dB, respectively. Within the error range allowed, these two directional couplers show high performance in agreement with theory and can reflect power changes accurately. The established numerical model is proved to be reliable and feasible.