X-Band Microwave Rotary Joint for Very-High-Power Satellite Tracking Systems

Link Microtek has developed an X-Band microwave rotary joint for satellite tracking systems that transmit a high pulsed power of 100 kW, with a mean power of 4 kW, over a wide frequency band of 2 GHz.

Designed to transmit and receive at frequencies from 8.5 to 10.5 GHz, the tracking system uses long runs of WR90 rigid waveguide, with six special single-channel rotary joints to provide the necessary movement for elevation, azimuth and tilt. According to Link Microtek, while single-channel rotary joints in themselves aren’t particularly tough to make, when the frequency bandwidth and the levels of power are extreme, it becomes a massive challenge. Any losses, even tiny ones, will generate a significant amount of heat, and thus, thermal modelling was the key in preventing internal overheating of the devices. What’s more, the customer’s system was un-pressurized, so that made it very difficult to keep breakdown voltages to acceptable levels.

Drawing on years of experience in this field, Link Microtek’s engineering team used CST electromagnetic simulation software to model those crucial aspects of the design and eventually came up with a rotary joint that could satisfy the stringent requirements of the customer’s specification. Incorporating a 10mm-thick heatsink to conduct the excess heat away, the rotary joints achieve a low insertion loss of less than 0.2dB and a VSWR of 1.2:1. They are manufactured from aluminium and measure 122mm in length with a heatsink diameter of 75mm.

As the satellite tracking system is installed in an exposed coastal location, the rotary joints also feature chromium-free passivation for corrosion resistance and IP65 sealing to prevent the ingress of moisture and dust.