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Amplitude Modulation

General Form:
am(sa oc fm fc td)
Example:
vin 12 0 am(10 1 10meg 100meg 10n)

parameter description default value units
sa signal amplitude   volts or amps
oc offset constant    
fm modulation frequency 1/tstop hz
rc carrier frequency 0.0 hz
td signal delay 0.0 seconds

The shape of the waveform is described by the following table:

time value
0 to td 0
td to tstop sa . {oc + sin(2$ \pi$ . fm . (time - td ))} . sin(2$ \pi$ . fc . (time - td ))

This function applies only to transient analysis, where time is the running variable. When referring to default values, tstep is the printing increment and tstop is the final time in transient analysis</a>. This function is a work-alike to the similar function found in HSPICE.

If this function is used bare and not part of an expression in a voltage or current source, then the general source instance parameters prm1 etc. map as below. It is possible to read and alter these values using the special vector @device[param] construct, or with the alter and sweep commands. However, there is no sanity checking so bad numbers can cause wild behavior or worse.

prm1 sa
prm2 oc
prm3 fm
prm4 fc
prm5 td


next up previous contents index
Next: Sinusoidal Up: Tran Functions Previous: Single-Frequency FM   Contents   Index
Stephen R. Whiteley 2019-06-03