What is the technical breakthrough identified in the paper?
(UG) CSA Catapult’s goal was to create an RF switching network to enable the application of the tunable reflective termination, which enables the introduction of the various reactive components to the Orthogonal Load Modulated Balanced Amplifiers (OLMBA).
We designed a RF switch (SPDT) that operates at Ka-band frequencies and has a power rating of up to 3 Watts with low insertion loss.
The fabricated RF switch is based on Gallium Nitride (GaN) on Silicon Carbide (SiC) technology and characterised through load-pull measurements to analyse its behaviour when exposed to various reactive components across the Smith chart.
Why were GaN and SiC used over other compound semiconductor materials?
GaN-on-SiC offers excellent thermal conductivity and can handle high-power density, which makes it ideal for high-frequency and high-power applications.
The key reason for selecting GaN was to increase the device’s compatibility with a wider range of RF systems and applications.
This switch was designed to function as the tunable reflective termination in an OLMBA which is also based on GaN technology. Using the same material for the substrate ensures seamless integration and optimised performance.
How in this research unique and how will it help accelerate radio frequency (RF) power amplifier technology, and LMBA and OLMBA architectures?
The Load Modulation Balanced Amplifier (LMBA) and its variations, such as OLMBA, are among the latest and most widely accepted power amplifier architectures. These designs have gained interest from academic institutions and the defence industry due to their enhanced efficiency over an extended frequency range.
The OLMBA combines the control signal power (CSP) with the main RF signal at the input stage. The introduction of a reactive component at the output-isolated port, which modulates the impedance, greatly reduces the power requirements for the CSP and so improves the total efficiency.
By developing this switch that enables dynamic load modulation, CSA Catapult can help advance OLMBA architectures, which are known for their wider frequency bandwidth and higher efficiency, which is a key capability when it comes to accelerating our journey to Net Zero.
What was CSA Catapult’s role in this research?
CSA Catapult’s RF and Microwave communications lab houses advanced characterisation technology where we analyse device performance with high accuracy.
We used the passive load-pull measurement system to evaluate the switch in a non-50-ohm environment which gave us valuable insights and aided our research.
The precise measurement data we gained can support the development of a tunable reflective termination model for CAD software, which will help further improve OLMBA designs.
How will this technology benefit our customers?
This work has expanded CSA Catapult’s capabilities in RF switch design and characterisation, and demonstrates how we can help customers advance RF and microwave communications applications.
From initial market analysis carried out by CSA Catapult, it is understood that among the top 20 companies manufacturing RF switches, only one is based in the UK. There is an opportunity to explore investment in this sector and interact with new companies who need components for high-power and high-frequency devices.
What type of applications might this switch help deliver?
This switch will help accelerate technology in communication systems such as base stations, satellites and antennas, as well as test and measurement setups for signal routing.
First and foremost, this switch is a flexible, enabling technology for RF power amplifiers with OLMBA architectures and presents an even greater opportunity to help customers optimise their products in applications for Future Telecoms.
Urman’s paper on ‘Ka-Band Single-Pole Double-Throw Switch in GaN MMIC Technology’ is published under open access in the International Journal of Microwave and Wireless Technologies.
