Understanding EDX Format Antenna Pattern Files

In order to use directional antennas with EDX software, the data describing the directional pattern must be stored in a data file. This is an ASCII data file you can prepare yourself using a text editor. This file is a tabulation of azimuths and relative field or dB values that describe a directional antenna pattern. Both horizontal and vertical plane pattern values can be listed in the file. The format of this file is as follows:

'Antenna Type', GAIN, KYPAT
AZR(1), HP(1)
AZR(2), HP(2)
.
.
.
AZR(NR), HP(NR)
999
NUM_SLICES, NELV
AZ_SLICE(1)
EL(1,1), VP(1,1)
EL(1,2), VP(1,2)
.
.
.
EL(1,NELV), VP(1,NELV)
AZ_SLICE(2)
EL(2,1), VP(2,1)
EL(2,2), VP(2,2)
.
.
.
EL(2,NELV), VP(2,NELV)
AZ_SLICE(3)
EL(3,1), VP(3,1)
EL(3,2), VP(3,2)
.
.
.
EL(3,NELV), VP(3,NELV)
.
.
.
.
AZ_SLICE(NUM_SLICES)
EL(NUM_SLICES,1), VP(NUM_SLICES,1)
EL(NUM_SLICES,2), VP(NUM_SLICES,2)
.
.
.
EL(NUM_SLICES,NELV), VP(NUM_SLICES,NELV)

where:

'Antenna Type' - a name of the antenna. It must be no more than 20 characters in length and enclosed in single quotation marks. This name is only used to identify the file; it is not used by the program.

GAIN - the maximum gain of the antenna in dBi. This number is not used by the program for the co-polarized antenna file. Instead, the program normalizes the pattern maximum to the maximum ERP for the transmitter. For cross- polarized antenna patterns this number is the amount of cross-polarization rejection in dB.

KYPAT - the key number which indicates whether the following tabulated pattern data is in relative field strength or relative dB. KYPAT=1 for relative field strength; KYPAT=2 for relative dB.

AZR - azimuth from 0 to 360 degrees or -180 to +180 degrees on which the horizontal plane pattern value is specified. These need to be in ascending order in the file. A 0.0 degree azimuth must be included. Maximum azimuth increment = 45°.

HP - horizontal plane pattern value in relative field as a decimal fraction, or dB, depending on the value of KYPAT.

NR - total number of azimuths listed in the file. The maximum number of horizontal plane pattern points which may be listed is 721.

999 - a special code which separates the horizontal plane from the vertical plan antenna data.

NUM_SLICES - number of vertical plane pattern azimuth “slices” or descriptions which follow in the file. Maximum value = 72.

NELV - number of vertical plane pattern values that are specified for each azimuth slice. Maximum value = 361. Each azimuth slice must also use the same set of vertical plane elevation angles.

If there is no vertical plane pattern information, the NUM_SLICES and NELV values should both be 0. This line will then be the last line in the file. In this case the EDX program will assume unity gain for all vertical elevations at all azimuths.

AZ_SLICE - the azimuth in degrees for which the following vertical plane pattern points is taken. Value must be in the range of between 0 to 360 degrees. The 0 degree azimuth slice must always be included.

EL - elevation angle between +90 and –90 degrees on which the vertical plane pattern value is specified. Minimum of 5 elevations. These angles begin above the horizon (positive) and progress to below the horizon (negative).

VP - vertical plane pattern value in relative field as a decimal fraction, or dB, depending on the value of KYPAT.

The structure given above is in generic variable name array notation. In preparing the file, actual, numbers are used in place of the variable names. A comma and/or spaces can be used to separate the fields on each line. So that the program can properly normalize the values for internal use, the azimuth and elevation with the maximum pattern value in each case must be included in the file.

The file can take any name desired. For consistency we recommend that .pat be used as the file name extension but this is not absolutely necessary.

Pattern information that defines the relative shape of the antenna pattern with regard to a cross-polarized signal should be entered as a separate data file using the above format. The name of this data file is identical to the name of the co-polarized file except that the extension .xpol is added. For example: if the co-polarized pattern is in a file “sample.pat” the cross-polarized pattern would be in a file called sample.pat.xpol.

All values for pattern gain (HP, VP) in the file can either be absolute gain or relative gain. The program normalizes each plane to the maximum value entered and then combines the various relative gains at the appropriate azimuths and elevations to give the relative gain in that direction.

Example file:

'sample_file', 0.0, 2
0, 10.0
1, 8.0
2, 4.0
....
357, 4.0
358., 8.0
359, 10.0
999
2, 180
0
90, -20
89, -19
...
0, 0
...
-89, -19
-90, -20
180
90, -20
89, -19
...
0, 0
...
-89, -19
-90, -20

For this file the 0.0 azimuth is the greatest gain so we normalize by subtracting 10.0 dB from all horizontal gains. Then, if for example the maximum ERP for this sector is 15 dBW, the ERP at 357 degrees from the main beam azimuth is:

15dBW + (4 - 10) = 9dBW

If there were vertical slices in this file then each vertical slice would be individually normalized in the same manner as above.