ISFFM - Frequency Modulated Sinusoidal Current Source Model

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Model Kind

Current Source

Model Sub-Kind

Single-Frequency FM

SPICE Prefix

I

SPICE Netlist Template Format

@DESIGNATOR %1 %2 ?"DC MAGNITUDE"|DC @"DC MAGNITUDE"| SFFM(@OFFSET @AMPLITUDE @"CARRIER FREQUENCY" @"MODULATION INDEX" @"SIGNAL FREQUENCY") #"AC MAGNITUDE"|AC @"AC MAGNITUDE"| @"AC PHASE"

Parameters (definable at component level)

The following component-level parameters are definable for this model type and are listed on the Parameters tab of the Sim Model dialog. To access this dialog, simply double-click on the entry for the simulation model link in the Models region of the Component Properties dialog.

DC Magnitude

DC offset used in an Operating Point Analysis. (Default = 0).

AC Magnitude

the magnitude of the source when used in an AC Small Signal Analysis. (Default = 1).

AC Phase

the phase of the source when used in an AC Small Signal Analysis. (Default = 0).

Offset

the DC offset of the signal generator (in Amps). (Default = 2.5).

Amplitude

the peak amplitude of the output current (in Amps). (Default = 1).

Carrier Frequency

the carrier frequency (in Hz). (Default = 100k).

Modulation Index

the modulation index (Default = 5).

Signal Frequency

the signal (message) frequency (in Hz). (Default = 10k).

Notes

  1. The image above shows an example waveform produced by an FM current source (connected to a 1Ohm load) with the parameters set to their default values. The shape of the waveform is described by the following formula:

I(t) = IO + IA sin[2πFCt + MI sin(2πFSt)]

where:

  • t is an instance of time
  • IO is the DC offset of the signal generator
  • IA is the maximum amplitude of the output swing (excluding the DC offset)
  • FC is the Carrier frequency
  • MI is the Modulation Index and
  • FS is the Signal frequency.
  1. The simulation-ready frequency modulated sinusoidal current source component (ISFFM) can be found in the Simulation Sources integrated library (\Library\Simulation\Simulation Sources.IntLib).

Examples

Consider the frequency modulated sinusoidal current source in the previous image, with the following characteristics:

  • Pin1 (positive) is connected to net IN
  • Pin2 (negative) is connected to net GND
  • Designator is I1
  • Offset = 0
  • Amplitude = 1m
  • Carrier Frequency = 10k
  • Signal Frequency = 1k
  • All other parameters for the model are left at their default values.

The entry in the SPICE netlist would be:

*Schematic Netlist: 

I1 IN 0 DC 0 SFFM(0 1m 10k 5 1k) AC 1 0

 

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