5.7 The Source Waveform Menu

In the Source Waveform menu you specify the excitation signal that will be injected at the source point or points during the simulation. A number of standard waveforms are available, and a user-defined input file can be selected as well. All source waveforms can be visualized and inspected using the Graph menu.
Figure 1-7: The Source Waveform Menu.

The available options are:

Impulse Default signal; enter the magnitude only.
Sin(f) Sine function; enter the magnitude and the frequency in GHz.
Sin(T) Sine function; enter the magnitude and the period as an integer multiple of the timestep Dt. Only a single period will be injected if the Periodic Excitation box is unchecked.
Sqr(f) Square wave; enter the magnitude and the fundamental frequency in GHz.
Sqr(T) Square wave; enter the magnitude and the period as an integer multiple of the timestep Dt. Only a single period will be injected if the Periodic Excitation box is unchecked.
Raised Cosine(T) Raised cosine function; enter the magnitude and the period as an integer multiple of the timestep Dt. Only a single period will be injected if the Periodic Excitation box is unchecked.
NEMP(T) Nuclear electromagnetic pulse waveform; enter the magnitude as well as the rise time and the fall time as integer multiples of the timestep Dt.
Gaussian(T) Gaussian pulse: enter the magnitude as well as the Sigma and the Mean as integer multiples of the timestep Dt.
Gaussian(f) Bandlimited signals with Gaussian envelopes; enter the magnitude as well as the bandwidth and the center frequency in GHz. Select one of the following three options:
  • A simple Gaussian Pulse (Constant). The center frequency is automatically set to zero. The bandwidth Df is centered at f=0 and extends from -Df/2 to +Df/2.
  • A Gaussian-modulated sine waveform (Sine). It is an odd function with respect to the maximum of the Gaussian envelope. This function has a spectrum of bandwidth Df about the center frequency.
  • A Gaussian-modulated cosine waveform (Cosine). It is an even function with respect to the maximum of the Gaussian envelope. This function also has a spectrum of bandwidth Df about the center frequency.

Note that the source waveform will be displayed in the time domain even though its characteristics have been specified in the frequency domain.
User Defined This option allows you to use your own arbitrary time-dependent function, sampled at intervals of Dt, as the excitation signal. The source function must be available in an ASCII text file with a sou extension to appear in the file selection window. The numbers stored in a source file represent the impulse amplitudes injected sequentially into the TLM network at the source point(s) or region(s). To generate such a source file, sample a desired analog function at discrete Dt intervals and write the values of these samples into an ASCII file. The value of Dt is displayed in the Simulation Control Data dialog box. The source file must have the following format (which is also the format of joh files).

int 
float 1 
float 2 
. 
float i 
. 
float n

The first number in the source file is the total number of samples in the file. If you want to specify a periodic source waveform, only one period needs to be sampled and stored. An example demonstrating the use of a source file is given in the Tutorial. After the source waveform has been specified, it appears as a graph for inspection and verification.