CNET304 Lab 6 Antennas Group 1

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Apr 3, 2024

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CNET304 Lab 6 - Antennas Lab 6: Antennas Name Student ID Signature* Darpan Harmel 301283854 Kapil Bikram Basnet 301294428 Krish Bohora 301314053 *By signing above, you attest that you have contributed to this submission and confirm that all work you have contributed to this submission is your own work. Any suspicion of copying or plagiarism in this work will result in an investigation of Academic Misconduct and may result in a “0” on the work, 1 Section No. Sec 5 Group No. 01 Obtained Mark (out of 25) Due Date

CNET304 Lab 6 - Antennas Learning Objectives Upon completion of this lab, students will reliably demonstrate the ability to: - Differentiate basic antenna types - Measure antenna frequency response with spectrum analyzer, tracking generator & return loss bridge - Determine antenna gain by referencing it to the known dipole - Plot the antenna radiation pattern and state antenna beam width and front-to-back ratio [ 1 mark ] Equipment Used in this Experiment (type, make, model): ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [ 1 mark ] Parts Used in this Experiment (other than antennas that are listed in the table below: ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… Background: Antenna Frequency Response Why is it important? It could be observed that different antennas are used for different frequencies. For example, long antenna for FM radio and short antenna for Wi-Fi. Therefor knowing antenna’s resonant frequency and their usable frequency band is the first antenna parameter we need to know. What do we need to measure it? Spectrum Analyzer with its Tracking Generator offers a one step method for obtaining the device-under-test (D.U.T.) frequency response – the same method as used for the cable’s frequency response earlier. However, unlike the cable or filter or amplifier, antenna is not a 2-port device so an additional device needs to be used: either Directional Coupler (simpler, cheaper, and good for lower frequencies) or Return Loss Bridge (more complex, more costly, and more precise, for higher frequencies). On what principle? At the out-of-band frequencies, the antenna reflects the signal back since there’s no impedance match to transfer power to antenna and then to air. Around the resonant frequency, antenna absorbs the signal and radiates it into the air as an EM wave. How does this measurement work? The 0-3GHz sweeping signal from the Tracking Generator is applied to the antenna. The Return Loss Bridge is a device that separates the 2

CNET304 Lab 6 - Antennas reflected signal and delivers it into Spectrum Analyzer’s input to be displayed. The expected graph is the return loss with high amplitude along most of the frequencies except around antenna’s resonant frequency where we can see significant drop in amplitude with distinctive notches. Note that simple antennas would have multiple notches at resonant frequency harmonics and some complex antennas are intentionally designed to cover different bands of frequencies. WARNING! Keep safe in the lab by keeping transmitting power 0dBm (in this case tracking generator) and your body min 10cm away from the transmitting antenna (in this case antenna as D.U.T.) Experiment Task 1: Antenna Frequency Response 1. [ 3 mark ] Identify the antennas you have and find their information on Internet: # ANTENNA TYPE, MAKE FREQUENCY Resonant Freq and/or Band RADIATION PATTERN in HORIZONTAL PLANE GAIN (in dBi or dBd) 1 (black whip with N connector) HG2405RD-NM 2 (magnetic mount) MM24-7-RSMA 3 (white tube) AOU24-YA-1414 4 (short black right- angle whip with SMA connector) “unknown model” 3

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CNET304 Lab 6 - Antennas 2. When doing frequency response measurement, as usual, the first step is NORMALIZATION. - Connect the Return Loss Bridge as shown, with D.U.T. port OPEN - Spectrum Analyzer: hard key SPAN  soft key Full Span (0-3GHz) - Tracking Generator: hard key TG  soft key On  Output Level 0 dBm  Normal On 3- Connect Antenna #1 to the D.U.T. port on Return Loss Bridge. Touch the metal part of the antenna and the adapters to try to get strong notches in the frequency response display. Note: Whip antennas are usually designed with a plan to be mounted on a metallic box that serves as a ground plane and enhances antenna’s operation. Your body also represents a ground plane.) 4- [ 4 marks ] For each of the 4 antennas: a) Sketch their frequency response graphs bellow for the ground plane position that produces strongest notch (you hold antenna metal base at different places by your hands or a flat metal) b) Indicate the frequencies of strong notches as read with a marker placed to the notch 4

CNET304 Lab 6 - Antennas Antenna #1 5   2.4-2.5 GHz band of interest

CNET304 Lab 6 - Antennas .0 Antenna #2 6

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CNET304 Lab 6 - Antennas 7

CNET304 Lab 6 - Antennas Antenna #3 Antenna #4 8 Note about SMA connectors: M and F refer to thread (inside M, outside F). M with pin is regular polarity, M with sleeve is reverse polarity (RP). Similar for F connectors. You don’t need to memorize proper names but it is important to connect adapters for proper fit.

CNET304 Lab 6 - Antennas Task 2: Antenna Gain WARNING! When transmitting wirelessly, keep safe in the lab by keeping your body min 10cm away from the transmitting antenna. There’s no danger at the receiving side. 1. [ 3 marks ] Determine gain of a dipole, an omnidirectional, and a directional antenna. GAIN OF A DIPOLE AS A REFERENCE - The professor will set the HP/Agilent Signal Generator to transmit at 2.45 GHz frequency with 0dBm power using an omnidirectional antenna. - You disconnect previous parts and Preset-Preset your Spectrum Analyzer. Set 2.45 GHz as the center frequency. Connect one end of the RG142 (or RG400) cable to the spectrum analyzer’s RF input and attach an N-type F-F adapter to the other end. - Ask professor to come with the dipole antenna (small whip with purple stripes) and you connect it to your cable (we have only few of those so use it carefully). Activate the PEAK marker on the signal. Hold your Rx dipole antenna in a vertical position at the same height as the Tx antenna (remember or label that position!). Get few seconds of no people movements and record the max power you can receive with this dipole: P r(dipole) = ……………..…………. - Return the dipole to the professor (be careful with it). 2. GAIN OF AN OMNIDIRECTIONAL ANTENNA  Connect the black whip antenna with N connector (the one that according to Internet data sheet has 5.5dBi gain). Rotate it in the same spot to verify that the amplitude is constant thus proving that it is an omnidirectional antenna. Then hold it in the same way and exactly the same position as you did the dipole antenna, get few seconds of steady display and record the max power you can receive with this antenna: P r(whip) = …………………..  Determine the GAIN of the longer black whip antenna with respect to the dipole. Since the received powers are in dBm, the gain would be calculated as the difference and expressed in dBd. Then, by adding 2.14dBi for the dipole, gain would be expressed in dBi. You write all steps how you are calculating and use proper units. Note that dB/dBd/dBi are relative values. Gain in dBd: G (whip) = P r(whip) - P r(dipole) =…………………………………….. 9 NOISE DATA STREAM 10001000…

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CNET304 Lab 6 - Antennas Gain in dBi: G (whip) =……………………………………………………… 3. GAIN OF A DIRECTIONAL ANTENNA  Connect the white tube Yagi directional antenna instead of the omnidirectional. Review your data from the Internet about what gain we should expect from this model.  First, find the antenna’s “main direction” in the horizontal plane by finding in which polarity and rotation you get the max received power. Then hold your Yagi antenna in it’s “main direction” at the same place as you did the previous two antennas and record the max power you can receive: P r(Yagi) = ………………… .....................................  Determine the GAIN of the white tube Yagi directional antenna in dBd and then dBi in the same way as above: Gain in dBd: G (Yagi) = P r(Yagi) - P r(dipole) =………………………………. Gain in dBi: G (Yagi) =………………………………………………….. Task 3: Antenna Radiation Pattern 1. EXPECTATIONS. On computer, search for a good image of “Yagi antenna radiation pattern” and observe how it is plotted in horizontal plane. Note normalized gain plotted on a radial scale from the outside circle 0dB towards the inner circles as more and more negative dB. Note that these patterns are usually measured in an “anechoic chamber” to avoid all obstacles and reflections so don’t expect perfect patterns from our lab. Keep the display the radiation pattern for a Yagi antenna open for the next steps. 2. [ 2 marks ] MEASUREMENTS. You would still have Yagi antenna connected to the RF IN of the spectrum analyzer and center frequency 2.45 GHz. Holding the antenna at the same place, rotate it in the horizontal plane to measure and record the received power at the angles 0, 30, 60,…330 degrees. Enter the values in the dBm column of the table on the 6 th page. Note: 0-degree angle is the one when your directional Rx antenna is pointed towards the Tx antenna and turned in the same polarization as Tx antenna for the highest possible gain. 3. [ 2 marks ] GRAPH the antenna pattern.  First, you need to calculate normalized gain for the antenna and enter values in the dB column: Normalized gain = Pr(at any angle) – Pr(at 0dgr) 10

CNET304 Lab 6 - Antennas  Next, decide on the dB/div among circles (either 10 or 5 or 2 or 1; it should be the smallest that can accommodate all your measured values, most likely 5 would be the best). Label the outside circle as 0dB and then label the other circles towards the center. Plot the measured points and connect them by smooth lines that follow the circles as much as possible (definitely not straight lines between points!). Consider drawing one main lobe, two on side and few at the bottom. Verify that the plotted radiation pattern has the main lobe with the highest amplitude in the 0 dgr direction and smaller in all other lobes. Draw with pencil and consult with the professor. 4. [ 2 marks ] TECHNICAL SPECIFICATIONS. Determine beamwidth of the antenna from its radiation pattern as follows: determine half-power points (where power is 3dB less than the power of the 0 dgr direction), draw the radius lines through those points and read the angle between them. Make sure you label beamwidth on the graph. Half-power (-3dB) BEAMWIDTH: …………………………………….………… Antenna Beamwidth:……………………………………………….. 5. [ 2 mark ] Determine front-to-back-ratio for each antenna as the ratio of powers at 0dgr and 180dgr (since the received powers are in decibels, the logarithmic ratio would be calculated just as the dB difference). Front-to-Back Ratio: …………………………………………………….. 11

CNET304 Lab 6 - Antennas Antenna Type: ……………………… 12 Angle (dgrs ) Measured Pr (dBm) Normalized Gain (dB) 0 -61 0 30 -58 -2 60 -55 90 -59 120 -71 150 -64 180 -57 210 -55 240 -56 270 -59 300 -61 330 -57 Antenna Specifications Type Make Model Frequency band* Beamwidth* Front-to-Back ratio* Gain* *as determined from your lab measurements (not internet) 30°

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