WLS5000_Lab9_AntennaMeasurements

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Humber College *

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WL504

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Electrical Engineering

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Apr 3, 2024

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WLS-5000 Applied Electromagnetics Wireless Telecommunications Lab-9 Antenna Radiation Pattern Measurements 1 Lab Report Prepared By Name: ________________________ Name: ________________________ Student ID: ____________________ Student ID: ____________________ 2 Objectives  Learning about anechoic chambers and antenna measurements.  To measure the approximate radiation pattern of a patch antenna using a VNA. 3 Materials  Network Analyzer (will be provided in the lab)  Coaxial cables (will be provided in the lab)  Connectors / adaptors (will be provided in the lab)  Calibration kit (will be provided in the lab)  Copper tape (will be provided in the lab)  Pre-fabricated test PCB (will be provided in the lab)  Ruler (students to bring)  Scissors 4 Information Every antenna radiates the power supplied to it in some directions better than others. Directivity of an antenna is defined as the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. The average radiation intensity is equal to the total power radiated by the antenna divided by 4π. If the direction is not specified, the direction of maximum radiation intensity is implied. Gain of an antenna is closely related to its directivity. Directivity is a measure of directional properties. In addition to these, Gain also takes into account the antenna efficiency. Gain of an antenna is generally expressed in dBi or dBd. In this lab, we will use the inset fed patch antenna we designed and prototyped last week to measure its ‘normalized’ gain and radiation pattern. 5 Pre-lab Assignment Review the class notes on antennas and the manual for Lab-9. Humber College Institute of Technology and Advanced Learning

WLS-5000 Applied Electromagnetics Wireless Telecommunications 6 Experiment Procedure 6.1 Part-A: Re-build and measure the inset-fed patch antenna from last experiment 1. Using the calculated parameters last week, rebuild your patch antenna prototype with the inset feed method so that you have a 50Ω matched antenna. Generally S11 = -10dB is used as a rule of thumb indicating a good match. 2. Calibrate your VNA for both reflection and transmission measurements. Use a frequency range of 2.2GHz to 2.7 GHz. 3. Measure your prototype with VNA and observe the S11 magnitude format. Record the resonance frequency and S11 value. Note that we are referring to the best matched point (lowest S11) as the resonance frequency. Resonance Frequency (f 0 ) = ______2.32______ GHz S11 magnitude at f 0 = _____-12.1_________ dB 6.2 Part-B: Measure the gain of the antenna in elevation plane 1. For this experiment we will use both ports of the VNA [please perform a 2-port calibration before proceeding]. 2. Connect a source antenna (a monopole antenna will be provided by your instructor) to port-2 of the VNA and connect your patch antenna to the port-1 of the VNA. Use a 1m (or 3 feet) coax cable with the patch antenna so you have flexibility to move and rotate the patch antenna. Refer to Figure 1 for an illustration of the test setup. a. Maintain a distance greater than the far field distance between the antennas and keep this constant. b. Try to minimize reflections by conducting the experiments away from metal surroundings or other equipment. Figure 1: Test setup illustration. Humber College Institute of Technology and Advanced Learning

WLS-5000 Applied Electromagnetics Wireless Telecommunications 3. We would like to measure the patch antenna radiation pattern in its elevation ‘cut’. Referring to Figure 2, this means rotating the antenna around the y-axis (following the green circle). Figure 2: Illustration of the elevation cut and rotation direction. 4. Steps for measurements (keep your marker at the resonance frequency): a. Measure the S21 at z axis first while your VNA marker is at the resonance frequency (patch antenna facing the source antenna). Typically the maximum patch antenna gain occurs at z-axis (boresight). This is the 90° degree measurement in your elevation cut. Record your S21 value in Table 1. b. While maintaining the distance between the antennas and keeping the y-axis steady, rotate your patch antenna in approximately 30 degree steps. Record your S21 readings in Table 1 c. When you complete the table with your S21 readings, normalize these readings by equating the 90° S21 value to 0 dB. For example, if your S21 reading was -25dB, you will equate this to 0dB by adding 25dB. This means you will add the same amount (25dB for this example) to every other angles and create the normalized column. Elevation angle (degrees) S21 reading (dB) Normalized S21 for polar plot (dB) 0 30 60 90 120 150 180 210 240 270 300 330 Table 1: S21 measurement results for radiation pattern plot. Humber College Institute of Technology and Advanced Learning

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WLS-5000 Applied Electromagnetics Wireless Telecommunications 5. Using the normalized values in Table 1, mark your data points on the polar plot provided in Figure 3. You can connect the dots based on your best ‘curve fitting’ intuitions. Figure 3: Polar plot for the prototype patch antenna based on lab measurements. 6. What is the half power beam width of your antenna? Half-power beam width (3-dB beam width) = ____________ degrees 7. [Optional] A similar experiment is done with an automated fashion in the video below: https://www.youtube.com/watch?v=LVsv26JjcNE Humber College Institute of Technology and Advanced Learning x z