Transient noise provides the benefit of examining the effects of large signal noise on many types of systems. It gives you the opportunity to examine the impact of noise in the time domain on various circuit types without requiring access to the SpectreRF analysis. This capability is an extension to the current transient analysis, and is accompanied by enhancements to several calculator functions, allowing you to calculate multiple occurrences of measurements such as risetime and overshoot.
AMS-Spectre supports only the single run method of simulating transient noise. The single run method involves a single transient run over several cycles of operation. The native Spectre multiple run method is not supported in AMS-Spectre at this time.
The use model adopted by APS for transient noise analysis is identical to the one used by the Spectre circuit simulator.
Set the following parameters to calculate noise during a transient analysis.
|
Parameter |
Definition | |
|---|---|---|
|
|
Bandwidth of pseudorandom noise sources. A valid (nonzero) value turns on the noise sources during transient analysis. The maximal time step of the transient analysis is limited to 1/noisefmax. | |
noiseon=[...] |
The list of instances to be considered as noisy during transient noise analysis. | |
noiseoff=[...] |
The list of instances to be considered as not noisy during transient noise analysis. | |
noisescale=1 |
Noise scale factor applied to all generated noise. It can be used to artificially inflate the small noise to make it visible over transient analysis numerical noise floor, but it should be small enough to maintain the nonlinear operation of the circuit. | |
noiseseed |
Seed for the random number generator. Specifying the same seed allows you to reproduce a previous experiment. | |
noisefmin (Hz) |
If specified, the power spectral density of noise sources depend on frequency in the interval from noisefmin to noisefmax. Below noisefmin, noise power density is constant. The default value is noisefmax, so that only white noise is included and noise sources are evaluated at noisefmax for all models. 1/ noisefmin cannot exceed the requested time duration of transient analysis. | |
noisetmin (s) |
Minimum time interval between noise source updates. Default is 1/noisefmax. Smaller values will produce smoother noise signals at the expense of reducing time integration step. |
|
noiseupdate=fmax | step |
Specifies whether noise is to be injected at a constant time step (fmax) or the Spectre solver time step is to be used (step). Injecting noise at a constant time step is suitable when the value of noisefmax is larger that the bandwidth of all signals in the circuit, and simulation time step is effectively controlled by noise. Only one noise frequency is updated at each time step. If the bandwidth of some of the signals exceeds noisefmax, which forces the simulator to take steps smaller than noisetmin, then noise should also be injected at each time step between the regular noise updates. In this case, all noise frequencies are updated at each time step. |
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Example
tr1 tran stop=4u noisefmax=5G noisefmin=1Meg noiseseed=1 noisescale=10 \param=isnoisy param_vec=[0 1 10ns 0 50ns 1]
tr1 tran stop=4u noisefmax=5G noiseupdate=step noiseseed=1 noisescale=10