SMIQ Arbitrary Waveform Generator ARB
1125.5555.03 2.341 E-9
2.21 Arbitrary Waveform Generator ARB
The option SMIQB60, a two-channel ARB generator, is an integrated I/Q modulation source of the
SMIQ. Thus, arbitrary modulation signals such as COFDM, multicarrier or noise can be generated. The
software WinIQSIM enables the calculation of modulation signals and the loading of these signals into
the instrument. Furthermore, signals which were calculated by a mathematical program such as Matlab
may be transferred.
2.21.1 Function
Conventional ARB generators substantially consist of an output memory with series-connected D/A
converter and analog filter. Due to the limited number of filters and their steepness the sampling rate
often has to be set considerably higher than required by Nyquist's theorem, in order for the aliasing
effects to be sufficiently suppressed by the analog filter. Fig. 2-214 shows these ratios for a 1-MHz
sinewave signal. If a filter provides a cutoff-frequency of 11 MHz, a sampling rate of at least 12 MHz
must be selected to make sure that the aliasing effects are suppressed sufficiently.
Fig. 2-214 Signal flow of ARB generator
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