Design, development and testing of IF section for FMCW reflectometry diagnostics for tokamaks

Abstract Reflectometry diagnostics is essential for determining plasma position, density, and density fluctuations to characterize tokamak plasmas. An Ultra-fast Frequency Modulated Continuous Wave reflectometry system for measuring time evolution of density profiles is operational on ADITYA-U. This paper discusses the development of an in-house IF section, signal acquisition and processing has already been reported separately. Initially, a modular design of the IF section was implemented. However, due to the higher cost and bulkiness of the modular design, it was replaced by IF section card developed in-house to achieve a compact and cost-effective solution. This paper details the circuit simulations, printed circuit board layout, design, and testing of the developed IF electronics. Both modular and card based IF sections were used and were found to be in excellent agreement with expected values of beat frequency. Specifically, modular IF design achieves a 2.5% error, and the card-based IF design measures with a 2% error. In addition to having a lower error compared to the modular IF design, the card-based design also offers a lower cost in a more robust and compact form factor.