when testing receivers, it is also necessary to simulate real transmitting and receiving conditions.
with the aid of the noise generator, an additive white gaussian noise (awgn) signal can be superimposed on the output signal of the r&s® smiq. the ratio of carrier power to noise power (c/n) can be varied with a high resolution over a wide range. this allows, for instance, precise sensitivity measurement of receiver circuits with a defined c/n ratio.
the distortion simulator allows amplitude and phase distortion to be simulated (e.g. of a travelling wave tube in a satellite output stage). all that has to be done is to enter via the iec/ieee bus the input values of the am/am and am/m characteristics to be simulated. the complete characteristics forming the basis for nonlinear distortion of the i/q baseband signals are calculated by means of spline interpolation. it is possible to distort i/q signals irrespective of whether they are generated by the internal modulation coder or applied from an external source. digital signal processing in the baseband (i and q signals) is used both for the generation of the awgn signal and distortion of the output signal. this ensures high accuracy and excellent repeatability of measurements.