Atoll enables you to work with antennas in many ways. To create a new antenna, you can import the data necessary from external sources, such as from a spreadsheet or from a Planet-format file. Once you have created an antenna, you can improve signal level prediction by smoothing the high-attenuation points of the vertical pattern.
In this section, the following are explained: • "Creating an Antenna" on page 143
• "Importing Planet-Format Antennas" on page 144 • "Importing 3-D Antenna Patterns" on page 145 • "Smoothing an Antenna Pattern" on page 147.
4.1.1 Creating an Antenna
Each Atoll project template has antennas specific to the technology supported by the template. As well, Atoll allows you to create antennas and set the parameters such as manufacturer, gain, horizontal pattern, and vertical pattern.
To create an antenna:
1. Click the Parameters tab in the Explorer window.
2. Click the Expand button ( ) to expand the Radio Network Equipment folder. 3. Right-click on the Antennas folder. The context menu opens.
4. Select New from the context menu. The Antennas New Element Properties dialogue appears. 5. Click the General tab. You can enter information in the following fields:
- Name: Atoll automatically enters a default name for each new antenna. You can modify the name Atoll enters if you want.
- Manufacturer: The name of the antenna manufacturer. - Gain: The antenna’s isotropic gain.
- Pattern Electrical Tilt: The antenna’s electrical tilt. This field is for information only; for an antenna’s electrical tilt to be taken into consideration in calculations, it must be integrated into the horizontal and vertical patterns. Atoll automatically calculates the pattern electrical tilt if the Pattern Electrical Tilt field is left blank or has a value of "0." This field has to be correctly filled (i.e., consistent with the defined vertical pattern) if you want the antenna to be available when selecting an antenna for a transmitter.
- Physical antenna: The name of the physical antenna to which the antenna model belongs. A physical antenna may have one or more antenna models (patterns), corresponding to different electrical downtilts. If you want to flag a physical antenna as obsolete, add the word "obsolete" (not case sensitive) to the name of the physical antenna. Physical antennas flagged as obsolete are not listed among available antennas in the Antenna Selector dialogue
When you create a new antenna, you can copy the horizontal and vertical antenna patterns from a spreadsheet or word processor.
It is strongly recommended to enter a name in the Physical antenna field. Atoll uses this entry to group antenna models into physical antennas.
d. Switch to Atoll.
e. Click the upper-left cell of the Co-polar Section table describing the horizontal pattern. f. Press CTRL+V to paste the data in the table.
- If there are some blank rows in your data sheet, Atoll will interpolate the values in order to obtain a complete and realistic pattern.
- When performing a calculation along an angle for which no data is available, Atoll calculates a linear interpo- lation from the existing pattern values.
g. Click Apply to display the pattern of the values you have pasted in.
7. Click the Vertical Pattern tab. The Vertical Pattern tab has a table describing the vertical antenna pattern in terms of the attenuation in dB (Att.) per Angle and a graphical representation of the pattern. Atoll allows you to enter antenna pattern attenuations for as many as 720 angles. Therefore, attenuation values can also be defined for angles other than integer values from 0° to 359°. If you have the vertical pattern in a spreadsheet or text document, you can copy the data directly into the table as described in step 6.
8. Click the Other Properties tab. You can define the following fields (not used in any calculation):
- Beamwidth: In a plane containing the direction of the maximum lobe of the antenna pattern, the angle between the two directions in which the radiated power is one-half the maximum value of the lobe. In terms of dB, half power corresponds to -3 dB. In this window, you can enter this angle in degrees. This field must be filled in cor- rectly if you want to display transmitters using a symbol that indicates the beamwidth.
- FMin: The minimum frequency that the antenna is capable of emitting. - FMax: The maximum frequency that the antenna is capable of emitting. 9. Click OK.
Atoll checks whether the vertical and horizontal patterns are correctly aligned at the extremities. The antenna patterns are correctly aligned when:
• the horizontal pattern attenuation at 0° is the same as the vertical pattern attenuation at the pattern electrical tilt angle, and
• the horizontal pattern attenuation at 180° is the same as the vertical pattern attenuation at the 180° less the pattern electrical tilt angle.
4.1.2 Importing Planet-Format Antennas
In Atoll, you can import Planet-format antennas by importing an index file listing the individual antenna files to be imported. Standard Atoll fields are directly imported. Other fields are imported for information only and are accessible on the Other Properties tab of the Antenna Properties dialogue.
If you are working with a database, you will have to create the required fields before you import the Planet-format antennas. For more details, see the relevant technical note.
To import Planet-format antennas:
1. Select the Parameters tab in the Explorer window.
2. Click the Expand button ( ) to expand the Radio Network Equipment folder. 3. Right-click the Antennas folder. The context menu appears.
4. Select Import from the context menu. The Open dialogue appears. 5. Select "Planet 2D Antenna Files® (index)" from the Files of type list.
6. Select the index file you want to import and click Open. The antennas are imported.
Atoll checks whether the vertical and horizontal patterns are correctly aligned at the extremities. The antenna patterns are correctly aligned when:
• the horizontal pattern attenuation at 0° is the same as the vertical pattern attenuation at the pattern electrical tilt angle, and
• the horizontal pattern attenuation at 180° is the same as the vertical pattern attenuation at the 180° less the pattern electrical tilt angle.
4.1.3 Importing 3-D Antenna Patterns
You can import three-dimensional antenna patterns in the form of text files. The three-dimensional antenna patterns you import are saved in the Antennas table.
During calculations, Atoll interpolates the data of antennas for which only horizontal and vertical cross-sections are available to create a three-dimensional pattern. When you import a three-dimensional antenna pattern, even though only horizontal and vertical sections of the antenna pattern are displayed, Atoll conserves all the information and can use it directly; Atoll does not therefore need to interpolate to recreate the three-dimensional antenna pattern.
The text file must have the following format:
• Antenna description: Three separate values are necessary to describe the three-dimensional antenna pattern. The columns containing the values can be in any order:
- Azimuth: The range of values allowable is from 0° to 360°, with the smallest allowable increment being 1°. - Tilt angle: The range of values allowable is from -90 to 90°, or from 0 to 180°, with the smallest allowable incre-
ment being 1°.
- Attenuation: The attenuation (in dB).
The text file describing the the antenna can also contain a header with additional information. When you import the antenna pattern you indicate where the header ends and where the antenna pattern itself begins.
To import three-dimensional antenna pattern files: 1. Select the Parameters tab in the Explorer window.
2. Click the Expand button ( ) to expand the Radio Network Equipment folder. 3. Right-click the Antennas folder. The context menu appears.
4. Select Import from the context menu. The Open dialogue appears. 5. Select the file to import.
7. If you already have an import configuration defining the data structure of the imported file, you can select it from the Configuration list. If you do not have an import configuration, continue with step 8.
a. Under Configuration, select an import configuration from the Configuration list. b. Continue with step 11.
8. Under Name, you can define a name for the imported antenna pattern. This name will appear in the Antennas folder on the Network tab. If no name is defined, Atoll will use the file name as the name of the antenna:
- If the name of the antenna is in the file, check the Value read in the file check box and enter a Keyword identifying the name value in the file.
- If you want to enter a name for the antenna, clear the Value read in the file check box and enter a name. 9. Under Gain, you can define the antenna gain. If no gain is defined, Atoll will assume that the gain is "0."
- If the gain of the antenna is in the file, check the Value read in the file check box and enter a Keyword identifying the gain value in the file.
- If you want to enter a gain for the antenna, clear the Value read in the file check box and enter a gain value. 10. Under Diagram, you define the structure of the antenna pattern file. As you modify the parameters, the results are
displayed in the table.
- 1st Pattern: Select the first row of the file containing data on the antenna pattern.
- File Tilt Range: Select the tilt range in the file. The tilt range can be measured from top to bottom or from bottom to top and from 0° to 180° or from -90° to 90°.
- Field Separator: Select the character that is used in the file to separate fields (" ", "<tab>", ";") - Decimal Symbol: Select the decimal symbol.
11. In the table under Diagram, click the title in each column in the table and select the data type: Azimuth, Tilt, Attenu- ation, or <Ignore>. As you modify the parameters, the results are displayed in the table.
12. Click Import. The antenna patterns are imported into the current Atoll document.
Figure 4.2: Importing a 3-D antenna pattern
You can save the choices you have made in the Setup dialogue as a configuration file by clicking the Save button at the top of the dialogue and entering a name for the configura- tion. The next time you import a three-dimensional antenna pattern file, you can select the same settings from the Configuration file list.
4.1.4 Smoothing an Antenna Pattern
Empirical propagation models, such as the Standard Propagation Model (SPM), require antenna pattern smoothing in the vertical plane to better simulate the effects of reflection and diffraction, which, therefore, improves signal level prediction. In Atoll, you can smooth antennas’ vertical as well as horizontal patterns.
To smooth the vertical or horizontal pattern of an antenna: 1. Select the Parameters tab in the Explorer window.
2. Click the Expand button ( ) to expand the Radio Network Equipment folder. 3. Click the Expand button ( ) to expand the Antennas folder.
4. Right-click the antenna whose pattern you want to smooth. The context menu appears. 5. Select Properties from the context menu.
6. Select the Vertical Pattern or the Horizontal Pattern tab.
7. Right-click the graphical representation of the pattern. The context menu appears. 8. Select Smooth from the context menu. The Smoothing Parameters dialogue appears. 9. Enter the following parameters and click OK to smooth the vertical pattern:
- Max Angle: Enter the maximum angle. Smoothing will be applied to the section of the vertical pattern between 0° and the maximum angle (clock-wise).
- Peak-to-Peak Deviation: Enter the attenuation values to which smoothing will be applied. Atoll will smooth all attenuation values greater than or equal to the peak-to-peak deviation with the defined correction factor. - Correction: Enter the correction factor by which the attenuation values will be smoothed.
10. Click OK.
4.1.5 Printing an Antenna Pattern
You can print the horizontal or vertical pattern of an antenna. To print an antenna pattern:
1. Select the Parameters tab in the Explorer window.
2. Click the Expand button ( ) to expand the Radio Network Equipment folder. 3. Right-click the Antennas folder. The context menu appears.
4. Select Open Table from the context menu. The Antennas table appears. 5. In the Antennas table, right-click the antenna whose pattern you want to print. 6. Select Record Properties from the context menu. The Properties dialogue appears.
7. Select the Horizontal Pattern tab or the Vertical Pattern tab to display the antenna pattern you want to print. 8. Right-click the antenna pattern and select Linear or Logarithmic from the context menu.
9. Right-click the antenna pattern again and select Print from the context menu.