Cryogenic Chamber for Remote Mechanical Tuning Cooled Passive Microwave Devices

D. D. Bronnikov, E. Y. Khvostov, Yu. V. Vekshin

Transactions of IAA RAS, issue 72, 10–13 (2025)

DOI: 10.32876/ApplAstron.72.10-13

Keywords: cryogenic chamber, tuning, microwave, servo, remote control, automation

Abstract

The aim of this work is to develop a laboratory cryogenic chamber for remote mechanical tuning of passive microwave (MW) devices under cryogenic conditions. The primary focus is on enabling precise parameter adjustment without physical or visual contact with the device, as well as exploring the potential for full automation of the tuning process. The project involved the developing principles for integrating servo drives into the hermetically sealed chamber and designing a mechanism to transmit rotation to the tuning screws. The rotation transmission is achieved via a special collet coupled with an M4-threaded rod featuring a fine pitch, which compensates for vertical displacement of the screws. Tuning is carried out using software developed in LabVIEW, which enables precise positioning of the servo drives, realtime monitoring of their current positions, stepwise movement control, and visualization of MW device parameters (VSWR, insertion loss) via a Rohde & Schwarz ZVA40 vector network analyzer. During testing, remote tuning of an S-band microstrip directional coupler equipped with five tuning screws was successfully carried out. The prototype chamber confirmed the system’s functionality: the adjustments were performed entirely within an isolated volume, eliminating the need for physical access. The maximum positioning accuracy of the servo drives was 0.44°, corresponding to a vertical screw displacement of 0.6 μm relative to the microstrip lines. Future efforts will focus on implementing automatic parameter optimization algorithms (e.g., minimizing VSWR and losses), scaling the system to accommodate a larger number of tuning screws, and designing a flexible shaft for use in densely configured setups. The long-term goal is to create a universal platform for high-precision tuning of passive MW devices operating in cryogenic environments, where stringent demands on parameter stability are critical.

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