29-05-2019 | Link Microtek Ltd | Subs & Systems
A dual-channel Ka-band microwave rotary joint designed and manufactured by Link Microtek is performing a critical role within a new stabilised antenna platform created by ADS International Srl for high-end satcom-on-the-move (SOTM) applications.
Typically mounted on vehicles for either commercial or defence use, the new system comprises a low-profile radome that houses a four-port, wideband flat-panel waveguide-array antenna collectively with ancillary hardware. Running at 19.2-21.2GHz in Rx and 29-31GHz in Tx, the dual circular polarisation system is perfect for the newest high-data-rate demands and, as it is European made, is free from any ITAR/EAR restrictions.
Important to the performance of the ADS antenna system are two of the company's rotary joints – one for azimuth and one for elevation – which allow RF signals to be served from the static side of the system to its rotating side.
The central transmit channel of the rotary joint is performed in WR28 waveguide and produces up to 50W of microwave power over the frequency range 29 to 31GHz with an insertion loss of only 0.5dB and a VSWR of 1.3:1. This enables the signal from the BUC, which is connected to the system port, to be transported through a waveguide transmission line to the antenna, therefore minimising losses.
According to Steve Cranstone, managing director of Link Microtek, power loss is a significant consideration in the system design. “To be able to transmit 50W at Ka-band frequencies, you need quite expensive amplifiers, so it is important not to lose too much of that power on the way to the antenna,” he said. “Using CST electromagnetic simulation software to verify the performance of the rotary joint design, our engineering team was able to ensure that the waveguide transmit channel would keep any loss to a minimum.”
He continued: “The design and manufacture of this type of rotary joint presents a significant challenge in a number of ways. Inside each one are scores of tiny individual parts, which have to be crafted to high precision and tight tolerances before being carefully assembled by hand. Despite this intricate, almost watch-like design, they have to be robustly constructed to withstand the particular mechanical stresses associated with SOTM systems so that they deliver reliable long-term operation.”
For ADS, chief engineer Marco Formaggi said: “We have been delighted with the performance of the rotary joints supplied by Link Microtek. The company’s many years of experience and expertise in this field enabled it to satisfy all of our technical and commercial requirements and helped us produce an innovative antenna system employing the most advanced technology available.”
