CNET304 Lab 6 Antennas Group 1

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Centennial College *

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304

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Electrical Engineering

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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
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
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