Hello,
I'd like to "reintroduce" units in meep, but I'm not getting the results
I'm expecting.
Following the description in "Units in Meep", let's say it's convenient
for me to specify distances in millimeters. For a source frequency of 3
GHz, free space lambda is .1 meters, or 100 mm. The description tells
me that I want to set the source frequency to 1/100 = .01.
Next I define the cell size to be something large enough that I can see
how long a wavelength is, but not so large that it takes a long time to
compute. Let's make it half a wavelength. First I convert lambda to
the base length I chose (1 mm), then divide by 2.
The result I get is appears to have a wavelength which is much smaller
than the size of the computation cell. (Also, something else I didn't
understand, the source appears to turn off quickly, even though I don't
specify a turn off time).
Any ideas on where I'm going wrong here?
Best Regards,
Matt
(define unit 1e-3) ; base unit in meters (1e-3 = 1
mm)
(define fh 3e9) ; frequency in hertz
(define lam (/ 3e8 fh)) ; free space wavelength in
meters
(define fcen (/ unit lam))
(define-param csize (/ (/ lam unit) 2)) ; make the cell size lam/2
(define-param eps 1)
(set! geometry-lattice (make lattice (size csize csize no-size)))
(set! geometry (list
(make block (center 0 0) (size csize csize no-size) (material
air))))
(set! pml-layers (list (make pml (thickness 10))))
(set-param! resolution 10)
(set! sources (list
(make source
(src (make continuous-src (frequency fcen)))
(component Ez) (center 0 0))))
(use-output-directory)
(run-until 200 (at-every 1.0 (output-png Ez "-Zc bluered")))
(exit)
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