PathDisp

MATLAB

s = PathDisp(G,Atm,DispType,p1,p2,...)

Description

Computes displacement of 2 beams (designated beam 1 and beam 2) along propagation path based upon the input displacement type 'DispType' and accompanying parameters. Specified separations should be thought of as applied to beam 2, and reported displacement vector is from beam 1 to beam 2. That is, if vector r1 locates beam 1 and r2 locates beam 2, then r1 + d = r2.

Parameters

Parameters	Description
G [struct]	Platform/target geometry structure from GeomStruct
Atm [struct]	Atmospheric modeling structure from AtmStruct. Must be a discrete atmospheric model.
DispType [string]	Identifier for type of beam displacement to model. Current valid identifiers are: 'ANGULAR' - Constant angular offset projected toward target, 'APERTURE' - Apertures with fixed offset directed to same target point, 'APERTURE-ANGULAR' - Aperture separation and angular offset together, 'CHROMATIC' - Beams of different wavelength directed to same target point, offset due to atmospheric dispersion, 'CHROMATIC-ANGULAR' - Dispersion combined with angular offset, 'TIME-OF-FLIGHT' - Round-trip propagation time multiplied by beam clearing velocity, 'TIME-DELAY' - Compensation for anisoplanatic delay for a given delay tau.
p1...pN [list]	(Optional) Input parameters to accompany DispType identifier
For DispType	'ANGULAR', parameter list is: 'APERTURE', parameter list is: 'APERTURE-ANGULAR', parameter list is: 'CHROMATIC', parameter list is: 'CHROMATIC-ANGULAR', parameter list is: 'TIME-OF-FLIGHT', no additional parameters 'TIME-DELAY', parameter list is:
theta [scalar]	Angular separation of beams (rad) Angular separation of beams (rad) Angular separation of beams (rad)
phi [scalar]	Orientation of separation at target measured counter-clockwise from P axis (rad) Orientation of separation at target measured counter-clockwise from P axis (rad) Orientation of separation at target measured counter-clockwise from P axis (rad) NOTE: angular separation will be applied to beam 2, and total displacement vector (chrom+ang) will be from beam 1 to beam 2
d [scalar]	Separation of aperture centers (m) Separation of aperture centers (m)
beta [scalar]	Orientation of separation of aperture centers measured counter-clockwise from P axis (rad) Orientation of separation of aperture centers measured counter-clockwise from P axis (rad)
lambda1 [scalar]	Wavelength of beam 1 (m) Wavelength of beam 1 (m)
lambda2 [scalar]	Wavelength of beam 2 (m) NOTE: displacement vector will be from beam 1 to beam 2 Wavelength of beam 2 (m)
tau [scalar]	The delay time at the target from position (a) to (b). NOTE: If a vector is used, then it is assumed that the length of tau equals the length of array G. Or, if mismatch occurs then only G(1) will be used with the vector tau.

Return Values

Return Values	Description
s [matrix]	Vector displacement along the propagation path (m). Number of rows in d equals number of screen positions in Atm. Column 1 is displacement in P axis, column 2 is
displacement in T axis, i.e., s	[s_P,s_T]

Examples

>> s = PathDisp(GeomStruct,AtmStruct,'ANGULAR',1.0e-6,0)

1 microrad separation at target in direction of P axis

>> s = PathDisp(GeomStruct,AtmStruct,'ANGULAR',1.0e-6,pi/2)

1 microrad separation at target in direction of T axis

>> s = PathDisp(GeomStruct,AtmStruct,'APERTURE',1.0,0)

1 m separation at aperture plane in direction of P axis

>> s = PathDisp(GeomStruct,AtmStruct,'APERTURE-ANGULAR',1.0,0,1e-6,pi/2)

1 m separation at aperture plane in direction of P axis combined with 1 mircorad separation at target plane in T axis

>> s = PathDisp(GeomStruct,AtmStruct,'CHROMATIC',1.3e-6,1.0e-6)

Separation of 1.0 micron beam from 1.3 micron beam due to atmospheric chromatic dispersion

>> s = PathDisp(GeomStruct,AtmStruct,'CHROMATIC-ANGULAR',1.3e-6, ...

1.0e-6,1.0e-6,0)

Separation of 1.0 micron beam from 1.3 micron beam due to atmospheric chromatic dispersion combined with a 1 microrad offset in the 'P' axis for the 1 micron beam

>> s = PathDisp(GeomStruct,AtmStruct,'TIME-OF-FLIGHT')

Path separation associated with propagation time delay

>> s = PathDisp(GeomStruct,AtmStruct,'TIME-DELAY',1e-3);

1 millisecond of time delay

>> s = PathDisp(GeomStruct,AtmStruct,'TIME-DELAY',[1:10]*1e-3);

1-10 milliseconds of time delay