Upgrade of the COMPASS tokamak microwave reflectometry system with I/Q modulation and detection

摘要

The microwave reflectometry system on COMPASS tokamak uses the frequency modulated continuous wave (FM-CW) in the K and Ka bands. The fast swept synthesizer together with the homodyne detection provides the complex beat frequency spectrum for the density profile reconstruction. The homodyne detection limits the use of reflectometry in the other applications like correlation or Doppler reflectometry. Our effort was to implement a heterodyne detection based on the existing system. We have decided to use a single-sideband modulator (SSBM) scheme to keep the compatibility with the fast sweeping. Lack of suitable SSBMs on the market leads us to use In modulator, which is modulated by the in-quadrature signals. (C) 2017 Elsevier B.V. All rights reserved.