IMPLEMENTATION OF A MATCHED FILTER FOR LFM SIGNALS USING A SYSTEM-ON-CHIP BASED SDR TRANSCEIVER
Authors: Kaidenko Mykola , Roskoshnyi Dmytro 
Published: July 2024

Background. Creation of communication channels with effective protection against intentional interference is the most urgent task for communication channels of unmanned aerial vehicles (UAVs). An effective solution is the use of signals with spectrum expansion, which allows reducing the impact of intentional interference on control and telemetry channels, thereby increasing the survivability of UAVs. The most optimal is the use of LCM modulation, which became possible with the development of SDR and SoC technologies. The main problem of using LFM modulation is the complexity of implementing matched filters. This requires research to create optimal digital implementations of matched filters.
Objective. The purpose of the paper is to determine the parameters of the LFM signal for the implementation of the communication system using CSS modulation on the SDR transceiver. Optimal implementation of discrete matched filter (correlator) for CSS BOK modulation on FPGA (SoC).
Methods. Analysis of the possibilities of implementing CSS BOK modulation for building a communication system based on SDR transceivers. Analysis of optimal options for building a discrete matched filter (correlator) for CSS BOK modulation on FPGA (SoC) and its implementation. Testing on a laboratory bench.
Results The possibility of creating a communication system based on an SDR transceiver using CSS BOK modulation has been confirmed. The optimal parameters of the LFM signal, which can be implemented, have been studied. An implementation of a discrete matched filter (correlator) for CSS BOK modulation on FPGA has been developed. Testing carried out on a laboratory bench using SDR transceivers AD9361 (AD9364) showed the correctness and effectiveness of the decisions made.
Conclusions The parameters of the LFM signal for the implementation in the communication system using CSS modulation on the SDR transceiver have been studied and determined. It was determined that when using the AD9361 (AD9364) transceiver, it is possible to implement an LFM signal with a band of up to 25 MHz, while the optimal symbol duration will be 16.6667 µsec at 1024 counts and a sampling frequency of 61.44 MHz. It was determined that the best CSS modulation method for creating a communication system is the binary orthogonal manipulation (BOK) method, which allows you to effectively use the advantages of SDR technologies, in particular, the ease of working with quadrature channels and, as a consequence, the ease of implementing phase synchronization. It has been determined that the best method of implementing a matched filter (correlator) on the basis of FPGA (SoC) is the application of fast convolution based on the fast Fourier transform. The developed implementation of a discrete matched filter (correlator) for CSS BOK modulation on FPGA showed the possibility of implementing a communication system with CSS BOK modulation on an SDR transceiver in full accordance with the research results. Experimental studies were carried out on a laboratory bench using SDR transceivers AD9361 (AD9364), which fully confirmed the results of simulation modelling.