Antenna Characteristics
Objective
Test the characteristics of the antenna.
Proof of Concept
Connect the patch antenna to the SMA connection on the rotating stage. The rotating stage is connected to the spectrum analyzer and the signal generator is across the room acting as the transmitter. Once everything is set up, test to see if the patch antenna can receive signals from the transmitter. We performed this test by rotating the patch antenna from 0 to 180 degrees in steps of 10 degrees to find the radiation pattern.
Methods
Need to ensure the radiation pattern of one antenna in order to know the highest received power level. Connect the antenna to the rotating stage using a SMA connector and connect the rotating stage to the spectrum analyzer. Then set the signal generator to 930 MHz and start to transmit the signal towards the antenna. Once the spectrum analyzer and transmitter were set up we started to test the antenna. We rotated the rotating stage from 0 to 360 degrees taking measurements at every 10 degrees. After taking the measurements we plotted the normalized received power level which gave us our radiation pattern. The radiation pattern shows us the highest received power at which our antennas can transmit at. This also tells us how we should mount out antennas on our phased array. Note that we initially thought our antennas were patch antennas, but they are actually printed dipole antennas. We did not realize this until after performing our antenna characteristics test. This affected our initial estimates regarding the range of our transmitting and receiving signals due to Friis Equation. The general form of Friis Equation is the following: 𝑃𝑟 = 𝑃𝑡 𝐺𝑡 𝐺𝑟 σ 𝛼 λ^2 / (4π)^3𝑅^4 where 𝑃𝑟 is the power at the receiving antenna, is the output power of transmitting 𝑃𝑡 antenna, 𝐺𝑡 is the gain of the transmitting antenna, 𝐺𝑟 is the gain of the receiving antenna, λ is the wavelength, R is the distance between the antennas, σ is the radar cross section, and α is our system loss. For our measurements we need to solve for the distance between the antennas, R. The transmitting power of our RFID reader, or 𝑃 , is set to 15 𝑡 dBm via the Arduino code, our receiving power, 𝑃 , is -45 dBm, our transmitting gain, 𝑟 𝐺 𝑡 , is 2.15 dB, our receiving gain, 𝐺 , is 2.15 dB, our radar cross-section, 𝛼 is -20 dB, and 𝑟 our system loss, α is -15 dB. We calculated our wavelength, λ, using the speed of light divided by our frequency which was 930 MHz and our wavelength was 0.322 m. Therefore, since we would like to solve for R, or the distance between the antennas, we would use the following form of Friis equation which also accounts for the known values in units of dB/dBm rather than linear scale: 𝑅 = sqrt {λ / (4*π)^1.5 *10^[(𝑃𝑟 − 𝑃𝑡 − 𝐺𝑡 − 𝐺𝑟 − σ − 𝛼)/20]. Using the previous equation, we plugged in all known values to solve for R, which was about 46 cm, or 18 inches. Therefore, we expected the range of our system to be roughly one and a half feet.
Results
We rotated the patch antenna from 0 to 180 degrees in order to understand the characteristics of the patch antenna. After observing the results, we found out that the patch antenna's highest received power level was at the 180 degree direction. Due to the highest received power level in that direction we oriented the broad side of our antenna in the 90 degree direction.
Patch Antenna Characteristics
![Screen Shot 2021-04-14 at 11.06.49 AM.pn](https://static.wixstatic.com/media/d427e6_fe2986e2c56043738cb7ee3c1ff2dfd6~mv2.png/v1/fill/w_852,h_768,al_c,q_90,usm_0.66_1.00_0.01,enc_auto/Screen%20Shot%202021-04-14%20at%2011_06_49%20AM_pn.png)
Patch Antenna 3 Characteristics
Images
![Image from iOS.jpg](https://static.wixstatic.com/media/d427e6_917d8acf16564dea8991425f1f69be91~mv2.jpg/v1/fill/w_814,h_1085,al_c,q_85,usm_0.66_1.00_0.01,enc_auto/Image%20from%20iOS.jpg)
Team Members Taking Measurements