Operating Manual Vol 1 - ES Documentation

SMIQNoise Generator and Distortion Simulator2.24 Noise Generator and Distortion SimulatorThe noise generator and the distortion simulator (Option SMIQB17) perform the following two functions:• Addition of noise to the SMIQ output level. Since the C/N can be finely varied, different receptionconditions can be realistically simulated.• Simulation of TWTA (traveling wave tube amplifier) distortion of satellite. The signal received by thesatellite is strongly distorted and thus more difficult to demodulate than an undistorted signal. Realreception conditions can be simulated with the distortion simulator and the receivers can thus betested realistically.The noise generator outputs an AWGN signal (Additive White Gaussian Noise) , ie the noise power ratiois Gaussian-distributed and the noise signal is added to the signal.Distortion is performed via AM/AM conversion and AM/PM conversion. The respective characteristicscan be loaded or modified via IEC/IEEE bus.NoisegeneratorIinDistortionIIoutQ inAM/AM conversionAM/PM conversionQQ outNoisegeneratorFig. 2-237Block diagram of noise generator and distortion simulatorThe noise generator and distortion simulator are independent functional units and can be operatedseparately. They exclusively use baseband signals I and Q. Both external I/Q signals and I/Q signalsinternally generated by the modulation coder can be distorted and superimposed with noise. The noisegenerator can also be switched on if internal and external modulation are switched off. The unmodulatedcarrier is then superimposed with the noise signal.IQ modulatorcos( ωt)IQextextOptionFadingSimulatorSMIQB14NoisegeneratorDistortionsimulatorRF OUTModulationcoderI QAUXsin( ωt)Fig. 2-238Noise generator and distortion simulator in the SMIQ1125.5555.03 2.383 E-9