Study of polarization strategy with two elliptical grating polarizers for ECRH systems

•The polarization strategy for ECRH systems with two elliptical grating polarizers was studied.•The polarization purity of the polarization strategy was analyzed.•The elliptical polarizer was tested at the low power experiment. The grating polarizer is a critical component in the millimeter-wave transmission line in an electron cyclotron resonance heating (ECRH) system, the main function of which is to change the polarization characteristics of the millimeter-wave. This paper presents an optimal polarization strategy for the millimeter-wave transmission line in an ECRH system. With two identical sinusoidal-groove elliptical grating polarizers, an arbitrary polarization can be realized. A special elliptical grating polarizer has thus been designed and its performance has been tested on a low power test bed. The results of the low power experiments agree well with the theoretical calculation values. The purity of the polarization achieved via the polarization strategy developed in this work has also been calculated and is found to be no less than 99.98 %. The analysis indicates that almost all the polarization states can be obtained by this polarization strategy.