Based on the Sino-European cooperation in the Galileo satellite navigation system Search And Rescue(SAR) service, a
multi-channel distress beacon signal simulator is presented here. The mathematic model and spectrum analysis of current
406 MHz distress beacons signals is presented which includes Emergency Position Indicating Radio Beacons (EPIRB)
for Maritime, Personal Locator Beacons (PLB) for land (road and rail), and Emergency Locator Transmitter (ELT) for
aeronautical applications. Based on Software Defined Radio (SDR) and digital IF techniques, the design of a SAR Signal Simulator (SAR-SS) is proposed, which can generate no less than 20 distress signals simultaneously. The Doppler shift and space propagation effect such as ionosphere delay, free space attenuation and etc, are simulated in SAR-SS, which provided a significant test and evaluation capability for SAR/Galileo project. The performance of SAR-SS is more accurate and stabile than the Cospas-Sarsat(C-S) requirement. SAR-SS will be a significant instrument for the Galileo system search and rescue project ground test.
This paper deals with several key points including parameter estimation such as frequency of arrival (FOA), time of
arrival (TOA) estimation algorithm and signal processing techniques in Medium-altitude Earth Orbit Local User
Terminals (MEOLUT) based on Cospas-Sarsat Medium-altitude Earth Orbit Search and Rescue system (MEOSAR).
Based on an analytical description of distress beacon, improved TOA and FOA estimation methods have been proposed.
An improved FOA estimation method which integrates bi-FOA measurement, FFT method, Rife algorithm and Gaussian
window is proposed to improve the accuracy of FOA estimation. In addition, TPD algorithm and signal correlation
techniques are used to achieve a high performance of TOA estimation. Parameter estimation problems are solved by
proposed FOA/TOA methods under quite poor Carrier-to-Noise (C/N0). A number of simulations are done to show the
improvements. FOA and TOA estimation error are lower than 0.1Hz and 11μs respectively which is very high system
requirement for MEOSAR system MEOLUT.