The Merlin Signal Generator - A Powerful, Low- Cost Constellation Galileo/GPS Signal Simulator

摘要

With the upcoming Galileo System and the GPS Modernizationrnprogram the need for a powerful signal simulatorrnfor the receiver developers has increased. In responsernto this need IfEN GmbH and Work GmbH launched arnjoint venture to develop a flexible signal generator, capablernof simulating all currently planned civil Galileo signalsrnas well as all civil signals specified for GPS III.rnKey drivers for the design were flexibility, scalability andrnlow cost. The simulator consists of three sections: Thernsteering software, which runs on a normal Windows orrnLinux based PC, the digital base-band part and three orrnfour digital-to-analog up-converter sections.rnThe steering computer is connected to the signal generationrnhardware by LAN and provides the base-band hardwarernwith the steering data for each individual signalrnchannel. The steering data consist of relative code offsets,rnDoppler shifts, power levels etc. The steering parametersrnare inferred from the configuration, i.e. the constellation,rnuser trajectory and signal environment being simulatedrnand the current system time.rnAll simulation parameters are highly configurable. Thernsoftware also provides the hardware with raw navigationrndata frames, including time-stamp. The base-band processorrnreceives the data and constructs the base-band signalrnmodulated with the data frames. Doppler and code offsetsrnare also applied at this stage. The base-band signals forrneach frequency band are combined digitally and upconvertedrnusing one analog chain. This approach practicallyrneliminates all relative group-delays within eachrnband.rnThe up-converter shifts the combined digital signal to thernappropriate RF-frequency. Each up-converter can be configuredrnindependently to any RF-frequency in L-band andrncan service up to 8 satellites (Galileo and/or GPS).