Faculty of Electrical & Electronics Engineering BEE4233 Antenna and Propagation LAB 1: Introduction to Antenna Measurement Mapping CO, PO, Domain, KI : CO2,PO3,P5,CTPS5 CO1: Characterize the fundamentals of antenna CO2: Analyze the parameters of antenna such as radiation pattern, impedance, directivity, gain, polarization 1 - Learning Outcomes: a) Introduction to measurement facilities in the laboratory b) Identify different types of antenna and their usage c) Plot the radiation pattern of the measured antenna 2 - Equipment Required a) ME1300 Training Kit b) RF Signal Generator (recommended model: Agilent N9310A) c) A pair of monopole antennas d) A pair of dipole antennas 3 - Introduction The ME1300 training kit consists of a transmitter module (TX), a receiver module (RX), and a set of antennas. Together with the RadPat software, it can be used to measure antenna parameters using the built-in RF detector. Figure 1 shows the ME1300 training kit and a block diagram of the process flow, while Figure 2 shows the RadPat graphical user interface.
Transmitting Antenna Receiving Antenna RadPat PC Software External RF Signal Generator Antennas Set Transmitter Module Transmitting Antenna Transmits RF signal RF Signal Receives RF signal and rotates the antenna Receiving Antenna (AUT-Antenna Under Test) Receiver module Module RF Signal Generator Generates RF signal Communicates with the controls the rotator, and collects and processes data RadPat Software Figure 1 ME1300 Training Kit and Process Flow Block Diagram
Figure 2 RadPat Graphical User Interface The graphical user interface of the RadPat software consists of the following features: a) Rotator control tab b) Settings tab c) Rotator measurement results display panel d) Antenna radiation pattern polar chart e) Status bar The RadPat software is a tool to communicate with the RF detector. The RadPat software is capable of rotating the receiver module antenna and displaying the antenna angular position. It allows the configuration of serial communications, and detects serial communication errors. It is also capable of collecting measurement data from the RF detector and displaying the data in a list, as well as plotting the antenna radiation pattern on the polar chart.
4 - ME1300 Module Connections Note: To get the best accuracy, you should perform calibration before making any measurements on your RF detector. Please refer to Appendix C for the calibration procedure. 1. Mount a 915 MHz dipole antenna on the top connector of the fixed antenna holder on the transmitter module (TX). This is the transmitting antenna. 2. Use an RF coaxial cable to connect the RF OUT connector of the RF signal generator to the RF IN connector of the transmitter module (TX). 3. Mount another 915 MHz dipole antenna (AUT) onto the top connector of the rotatable antenna holder on the receiver module (RX). This is the receiving antenna. 4. Connect the RF IN connector and RF OUT connector on the receiver module (RX) using a coaxial cable (to send the signal back to the RF detector). 5. You can orientate the two antennas at different directions but make sure that they are of the same height. Note: The distance between both antennas must be at least 0.5 m to perform the measurement in the far-field region. 5 - RadPat Software Configuration 1. The RadPat software communicates with the receiver module and the RF detector. 2. Open the RadPat software; click Settings at the menu bar, and select ComPort. The dialog box as shown in Figure 3 appears. 3. In the ComPort tab, select the desired PC ComPort and make sure that the selected PC ComPort matches the one set earlier for the PC. 4. Set the Baud Rate to 57600. You may click the Check ComPort Connection button to verify the COM port connection of the PC.
Figure 3 ComPort Settings Tab 5. Click the Instrument tab and unselect Enable Instrument. The RF detector will be activated when the Enable Instrument is unselected. Figure 4 Instrument Settings Tab 6. In the RF signal generator, set Frequency to 915 MHz. This is the frequency of the antenna-under-test (AUT). 7. Set Power Level to -10 dbm. 8. Click the Measurement tab. This allows you to change the measurement parameters as shown in Figure 5.
Figure 5 Measurement Settings Tab 9. Deg/Step in the Rotator panel defines the turning angle of the rotator. The program will observe and record the data for every step position defined in Deg/Step. The minimum and maximum values are 5 degrees and 30 degrees respectively. By default, Deg/Step is set to 10. 10. Radiation Pattern Plot defines the 0-dB reference value for the radiation pattern. By default, it is set to 20 dbm. 11. Scale lets you adjust the resolution of the radiation pattern on the polar chart. Set the resolution to 15 db/div. 12. Click Connect after configuring all the desired parameters. This will bring the rotator back to its home position. 13. The Info Display tab shows the information of the configured parameters and the operations of RadPat. Figure 6 Info Display Tab
14. After the homing operation has completed, the window will return to the RadPat main interface. Click Run at the menu bar to perform the Start, Pause, Stop, and Homing operations of the rotator. 15. Click Graph at menu bar to Normalize or Undo the normalization of the radiation pattern. 16. RadPat allows you to save the plotted data and display the data when necessary, as shown in Figure 8. To save the data, click File at the menu bar, and then click Save As. Select the desired directory to save the plotted data. To recall the saved data, click File at the menu bar, and then click Open. Select the corresponding directory to retrieve the data. Figure 7 Show Recorded Data Display 17. You may click a particular plotted data in the DATA POINT panel. The selected point in the radiation pattern will be indicated as a red circle.
6 - Plotting Antenna Radiation Pattern Using RF Detector 1. After completing the configuration procedure in Section 2 and Section 3, adjust the horizontal distance between the two antennas to 50 cm. 6. 2. Open the RadPat software; click Connect to configure the desired parameters. Click Run at the menu bar, and then click Start to begin plotting the antenna radiation pattern. 3. Observe the plot and record the received signal strength at each step (e.g., 10 ) into Table 1 in Appendix A. 4. Plot the received strength at each step in Polar Chart 915 MHz Dipole Antenna Using RF Detector in Appendix B. 5. Repeat steps 1 to 8 by replacing the transmitting and receiving antennas with 915 MHz monopole antennas. 6. Observe the plot and record the received signal strength at each step (e.g., 10 ) into Table 2 in Appendix A. 7. Plot the received strength at each step Polar Chart 915 MHz Monopole Antenna Using RF Detector in Appendix B.
7 - Discussions 1. Explain the difference between the data collected from the monopole and dipole antennas. 2. Complete the empty rows in the table below: Tab/Panel/Menu Bar Feature/Button Description Start Pause Run Graph Settings > ComPort Settings > Instrument Settings > Measurement Settings > Info Display Data Point Stop Single Capture Homing Normalize Undo PC ComPort Baud Rate Enable Instrument Deg/Step: 0-dB Ref: Scale Info Display Step No. Angle RF To select the port for communication To select the baud rate of the COM Ports Number of steps
Appendix A Antenna Rotation Measurement Using RF Detector Record Form Table 1 915 MHz Dipole Antenna Angle (Degree) RF Level (dbm) Angle (Degree) 10 190 20 200 30 210 40 220 50 230 60 240 70 250 80 260 90 270 100 280 110 290 120 300 130 310 140 320 150 330 160 340 170 350 180 360 RF Level (dbm) Table 2 915 MHz Monopole Antenna Angle (Degree) RF Level (dbm) Angle (Degree) 10 190 20 200 30 210 40 220 50 230 60 240 70 250 80 260 90 270 100 280 110 290 120 300 130 310 140 320 150 330 160 340 170 350 180 360 RF Level (dbm)
Appendix B Polar Chart 915 MHz Dipole Antenna Using RF Detector
Polar Chart 915 MHz Monopole Antenna Using RF Detector
Appendix C Tips on How to Calibrate the RF Detector 1. Setup the equipment as shown in Figure 8. To connect the two rods, remove one SMA adapter from one of the rod. This setup is with the assumption that removing the SMA adapter has insignificant impact on this calibration process.. Figure 8 Calibration Setup 2. In Radpat, click on the Calibration at the Settings menu bar. At the calibration tab, click on Perform Calibration button to run the calibration.
Figure 9 Calibration Menu Tab 3. At the calibration window, key in the value of the desired frequency. 4. At the signal generator, set the power level of the signal generator according to the calibration points which stated at the calibration table. For example -60 dbm. Then press the RF On button at the signal generator to turn on the RF Output. 5. At first, the measured value might be fluctuating a lot. Wait until the measured value settling down with minimum fluctuation, and then press the SET button to set the calibrated value. Figure 10 Calibration Window 6. Repeat step 4 and 5 for the other power levels. Save the calibrated data after ALL the calibration points were calibrated. 7. Save the calibration file with the desired name at the desired location (Calibration folder is suggested). 8. Make sure the calibration file is loaded before making any measurements on your RF detector.
Appendix D Tips on How to Import the Plotted Data into Microsoft Excel The plotted data on RadPat is saved in the dat format (with the.dat extension) and can be opened by any text editor. For example, you may import the plotted data into Microsoft Excel to further analyze the data. 1. Open Microsoft Excel if it is not already opened. 2. Select the desired directory using the keyboard shortcut Ctrl+O. 3. In the Files of type: box, select All Files (*.*); select the text file that you wish to import into Microsoft Excel. This is shown in Figure 11. Figure 11 Opening the Import Text File 4. Click Open after selecting the desired text file. The following Text Import Wizard window appears. Figure 12 Text Import Wizard (Step 1)
5. Select Delimited and set Start import at row: to 1. Leave the default setting for File origin:, and then click Next. 6. Select Comma under Delimiters as shown in Figure 13, and then click Next. Figure 13 Text Import Wizard (Step 2) 7. Select General. Click Finish to import the plotted data into Microsoft Excel. Figure 14 Text Import Wizard (Step 3)