Fundamental Measurement Techniques: Signal Simulation and Signal Generators.
Part four of our new occasional series around ‘Fundamental measurement techniques’ takes a look at the basics of signal simulation and signal generators.
We use signal simulation to test against a standard for compliance or to add interference or impairments to test the robustness of a system.
Simulated signals can record/playback real signals scenarios such as those in defence, communication and design applications as well as for conformance during manufacturing test.
We have a broad range of Signal Generators available.
These include generators for:
Basic CW Signals
Here core specifications include Range (Frequency minimum to Frequency maximum), Resolution (smallest frequency increment) Accuracy, Output Power and Phase Noise. n.b. Poor frequency accuracy and/or resolution will cause the transmitter output to be at the wrong frequency. Poor phase noise spreads energy into adjacent channels.
Analogue Signal generation
Here core specifications include Frequency Range, Modulation rate/deviation, Modulation Distortion (n.b. Non-linear distortion is characterised by the appearance of harmonics other than the fundamental component in the baseband output)
Vector Signal generation
Here core applications include Format Specific Signal Generation, Receiver Sensitivity, Receiver Selectivity and Component Distortion.
With all of these measurements it is critical that test signal imperfections are removed or at least taken into consideration (mathematically). For example if there is a source of error in the I/Q modulator, RF chain, IQ path the resulting measurements could be impaired by pass-band tilt, ripple, and roll off.
Often when removing test signal imperfections a trade-off is made against test time in terms of calculation time.
A variant of signal simulation testing is to capture real time signals and use those as the source. This requires the generation/ measurement device to have RF capture and playback functionality. This can be both analogue or digital capture and playback.
In summary, there are many complexities to choosing the correct signal generation/ simulation instrument or measurement device. If in doubt get in touch and we’ll be only too glad to help.