Heterodyne detection system of frequency hopping microwave reflectometer for Alfvén eigenmode measurements in LHD

In order to measure the internal structure of fluctuation, a broadband frequency-tunable system, which has a fast and stable hopping operation, has been developed in the large helical device. For constructing an accurate heterodyne phase detection system, a single-sideband (SSB) modulation technique is applied. Recently, high performance (SSB) modulators have been available in the wide band frequency range and its sideband rejection is around−20 dB. The frequency multiplier and mixer deformed the signal and the band-pass filter is used effectively to attain high signal-to-noise ratio.