A phase shift group delay-based approach to resolving the phase ambiguity problem in plasma microwave diagnostics

In the diagnosis of plasma microwave transmission, when the plasma size is large and the electron density is high, the microwave will cause a phase period ambiguity problem. In order to solve the phase ambiguity, a novel method of using the phase shift group delay (PSGD) to recover the true phase shift is proposed. The PSGD method is used to recover the simulated phase shift and diagnose the plasma. The diagnostic accuracy is all greater than 91%, which verifies the method. And the new method is used to diagnose the real inductively coupled plasma with high precision. Through analysis, the method of group delay recover phase shift is more suitable for stable plasma or slow-varying plasma.