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To calculate PULSE PROPAGATION you will need to use SWAMPGREEN.FOR. To run SWAMPGREEN.FOR you have to choose input parameters. Necessary recommendations you will find here: User manual for "SWAMP-1 CW propagation"

CODE GENERATING TIME-DOMAIN PULSE RESPONSE

The files in the complete Acoustic Model package producing the time-domain pulse response for range-dependent ocean waveguides are: SWAMPGREEN.FOR, TIME.FOR, SWAMPGREEN.IN and PULSE.IN. To get the pulse response for the waveguide, the user has to first run SWAMPGREEN.FOR with the provided input files SWAMPGREEN.IN and PULSE.IN. The structure of file SWAMPGREEN.IN is the same as is required for the SWAMP-model, except the parameter 'freq' is , the carrier frequency of the pulse. Thus, the user has to refer to the "SWAMP USER GUIDE" for information about the parameters used. The structure of file 'PULSE.IN' is shown in Fig. 5A.1, where only the first four parameters are used by SWAMPGREEN.FOR. The parameters in 'PULSE.IN' are:

1. freq (Hz) is a carrier frequency (equivalent to , described above).

2. Np is the integer number of sampling points per period in the digitized emitted signal.

3. nos is the integer number of signal periods in the active part of the signal.

4. N is the number (an integer power of 2) of Fourier sampling points including the zero-filling (equivalent to , described above).

5. nr is the integer number of range points in which the spatial transfer function is written out by 'SWAMPGREEN.FOR' in the output file 'SWAMPGREEN.DAT'. This parameter can be calculated as rmax/dr, where rmax and dr are parameters in 'SWAMPGREEN.IN'. It is printed out on the screen at the beginning of the SWAMPGREEN.FOR run, so it can be corrected before running TIME.FOR.

6. nz is the integer number of depth points for which the spatial transfer function is written out by 'SWAMPGREEN.FOR' in the output file 'SWAMPGREEN.DAT'. This parameter can be calculated as h/dh, where h and dh are parameters in 'SWAMPGREEN.IN'. It is printed out on the screen at the beginning of the SWAMPGREEN.FOR run, so it can be corrected before running TIME.FOR.

7. nrw (nrw<nr) is the integer number of the point in range at which the color contour plot 'pressure amplitude versus depth and time' is to be created. It can be determined as rw/dr (rw is a parameter described below). The user combines parameters r and dr to get the integer.

8. rw (m) is the distance in range at which the contour plot 'pressure amplitude versus depth and time' is created by 'TIME.FOR'.

9. c0 (m/sec) is the reference sound speed that determines the start of the time window for a receiver at range rw. It is chosen equal to the highest wave speed in the problem. It is used by 'TIME.FOR' to scale the beginning of the time axis at distance rw.

10. ddz (m) is the depth step size to scale the z axis for the contour plot. It is determined by the parameters from 'SWAMPGREEN.IN' as ddz=dz.

11. nzw (nzw< nz) is the integer number of the point in depth Z (in meters) at which the line plot ('pressure amplitude versus time) is to be created. It can be determined from the parameters in 'SWAMPGREEN.IN' as Z/dz. The user combines parameters to get the integer.

The output of 'SWAMPGREEN.FOR' is the file 'SWAMPGREEN.DAT', which is a binary, direct access file with record size 8 bytes. Every record is the complex spatial transfer function , where is the number of the frequencies calculated as . Index k is the fastest changing one.

The user runs 'TIME.FOR' for Fourier synthesis after 'SWAMPGREEN.FOR' has executed. The input files for 'TIME.FOR' are 'PULSE.IN' and 'SWAMPGREEN.DAT' created by 'SWAMPGREEN.FOR'. The structure of both files is described above. The output files are 'PULSE.LINE' and 'PULSE.OUT'.

The file 'PULSE.LINE' is a two column ASCII file representing the received pressure amplitude versus time at a receiver depth and range determined by the parameters nzw and rw, respectively, from 'PULSE.IN'. The time axis is scaled as rw/c0+ (in seconds).

The file 'PULSE.OUT' is a binary direct access file with record size 4 bytes. Each block of information is represented by 12 bytes and contains the negative current depth, current time and the received pressure amplitude information for the contour plot at the range point determined by the parameter rw: . Index j changes faster than index i. The time axis is scaled as in the file 'PULSE.LINE'. The depth axis is scaled by (in meters). The structure of ‘PULSE.OUT’ allows one to plot contour data using standard graphing software, for example, ‘Spyglass-Transform’ with the binary columns option for the input data file.

Code 'TIME.FOR' contains a parameter statement at the beginning of the code. Parameter nt1 determines the maximum allowed FFT length (it has to be an integer power of 2). Parameter nt has to be 2*nt1. Parameter nt1 is set to 4096. One has to change both parameters if one wants to widen the temporal window and decrease the frequency step size