Radio Evaluation and Training Tool - RETT - Concept and design proposal

Authors:

  • Stefan D Olsson
  • Ulrika Uppman

Publish date: 2023-02-06

Report number: FOI-R--5416--SE

Pages: 24

Written in: Swedish

Keywords:

  • radio
  • jamming
  • training tool

Abstract

The project have been executed as a part of the FMV-FoT program. This part of the program is called "RETT - Radio Evaluation and Training Tool". The purpose was to establish whether it is possible to build a training system that allows jamming on a radio system without transmitting the jamming signal "in the air". This would facilitate training and planning, since external jamming-platforms and transmission permits would not be needed. The RETT-project is an adaption and further development of the GETT-project at FOI (GETT - GNSS Evaluation and Training Tool). For this, software have been developed to generate jamming scenarios which defines when, where, and at which level the jamming signal is generated.The RETT-device is connected between a radio and it's antenna to be able to inject a jamming signal into the radio, without affecting the radio transmitting or receiving. It must therefore be able to handle signals in different directions. The RETT-device must also be designed to tolerate the full transmission power of the radio, which can be up to 50 W. This is done through a power-adaption circuit. The power-adaption must protect the RETT-devices internal components from the power of the radio and generate enough jamming power into the radio. Relevant levels of jamming have been determined from two scenarios, one advanced jammer at a range of 5 km, and a jammer mounted in a fixed-wing UAV at a shorter distance and at an altitude of 400-1000 m. Calculations on both cases give a relevant jamming level of approximately -20 dBm. The RETT-unit have been designed to provide at least -20 dBm jamming level. Two functional prototypes have been designed. The first with a power sensing circuit that switches the incoming signal to a termination when the connected radio transmits. The incoming signal is switched when the level exceeds a minimum safe level for components internal to the RETT-unit. The second functional prototype is based on a circulator/isolator components that sense the direction of the signal. I.e. the transmitting power is sent to a termination while the transmission of the RETT-unit is sent to the input of the connected radio. The solution is attractive since it doesn't require switching or signal detection. The first functional prototype has been implemented in a hardware-demonstrator. A number of measurements have been made on this demonstrator both on different parts and on the whole unit connected to a radio-system with 50 W transmit power. Measurements have also been made to make sure that only negligible signal levels leaks to the antenna. The evaluation have shown that the demonstrator can handle 50 W and generate a jamming signal that fulfils the levels determined (-20 dBm) in the jamming-scenarios.