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## define_antenna

• description: Allows generating time-varying fields using a modulated sine-wave current source.

• example:
&define_antenna
start = 0.01, end = 0.02, position = 0.03,
direction = "z",
current = 1,
frequency = 2856e6,
waveform = "spline.wf"
&end

This defines a current source in the longitudinal direction extending from z of 1cm to 2cm at a radius of 3cm. The amplitude of the current is 1A with a frequency of 2856MHz, modulated by the envelope in SDDS file spline.wf.

• synopsis and defaults:
&define_antenna
double start = 0;
double end = 0;
double position = 0;
STRING direction = "z";
double current = 0;
double frequency = 0;
double phase = 0;
STRING waveform = NULL;
double time_offset = 0;
&end


• details:

• direction: may take values "z" and "r", indicating an antenna extending in the longitudinal or radial direction, respectively.
• start, end: starting and ending limits of the antenna in the direction direction.
• position: position of the antenna in the "other" direction. I.e., it is the r position if direction is "z", and the z position if direction is "r".
• current, frequency, phase: basic parameters of the antenna waveform.
• waveform, time_offset: specifies an envelope function for the antenna drive. The SDDS file waveform must contain at least two columns, named t (for the time in seconds) and W, specifying the envelope W(t). The antenna is driven by the function , where is the current in Amperes, is the time in seconds, is time_offset in seconds, is frequency in Hertz, and is phase in radians.

Next: load_fields Up: Manual Pages Previous: Geometry File
Robert Soliday 2005-06-28