Low-Cost Educational System for Electromagnetics & Wireless Communications
The 2013 IEEE AP-S Antenna Design Challenge required student teams to build an antenna system with reconfigurable antenna elements that can adapt to different propagation conditions. Other challenge specifications stated that the antenna system should be used to teach how antennas work, and that the system should operate at 2.4 GHz with its own source. This reconfigurable antenna measurement system for educational use, from the Huff Research Group at Texas A&M University, tied for first place in the challenge. Two-crossed dipole antennas connected to XBee radios and Teensy microcontrollers serve as the basis of the measurement system. The crossed-dipole antennas were simulated and then fabricated, and the radiation patterns of the antennas were then measured using the measurement system and compared to the simulated results.
Transcript
00:00:00 this is an entry submitted in response to the 2013 it e APS student design challenge reconfigurable antennas this entry is submitted from the Huff research group within Texas A&M electromagnetics and microwaves laboratory our entry is a reconfigurable antenna test bed a lowcost educational system for electromagnetics Wireless Communications and electronics here is a
00:00:25 concept overview of our test bed our system is based on pattern and polarization reconfig antennas the antenna under test or aut can be switched between two different polarization States and two different pattern states which allow for Broadside horizontal and fire horizontal and broadside vertical polarizations the reference antenna can be switched
00:00:45 between two different polarization states allowing the system to perform both co-polarized and cross-polarized measurements without having to physically rotate the antenna the two different antennas serve as the basis for the two different modules in the system our system takes advantage of the reconfigurability of both antennas in order to test antenna
00:01:06 radiation patterns and evaluate conditions for reconfigurable performance in a system our system can be expanded to accommodate multiple antenna modules to examine other antenna driven techniques such as Source localization our antenna design is based on two probe fed linearly polarized micr strip patch antennas with one of the antennas rotated 90° around the x-axis
00:01:29 the radiating mechanism for the antennas is the fringing electric fields at the edges of the patch these can be approximated as rectangular radiating slots in the ground plane to build the cross dipole from the two patches the two patches are superimposed in the ground plane the patches are reduced in width and overlaid at the probe position to combine the two polarizations into a
00:01:51 single antenna this decrease in width will create a substantial reduction in the radiation efficiency of these antennas compared to their typical p counterparts the two antennas are now shorted together to isolate each polarization State slots are made at the intersection of the narrow patches RF pin diodes are placed between the gaps allowing each polarization state to be
00:02:12 selected independently of the orthogonally polarized state to activate the pin diodes and select the polarization State bias lines are added to the design the bias lines are grounded for both RF and DC so that the DC bias on the center conduction controls the state of the antennas for the Third configuration of the aut an extra length of narrow patch
00:02:33 is added which extends the patch antenna Beyond a half wavelength and produces an nire pattern a quarterwave bias T is added to isolate the extended arms DC control from the adjacent arm two modules were developed to accommodate these antennas each module consists of an antenna either the aut or the reference antenna a bias S ciruit A Teensy 2.0 Plus+ microcontroller and an
00:02:59 XB series 1 Pro Wireless Radio the wireless radios communicate using the 802.15.4 protocol and operate in the 2.4 GHz ISM band in order to communicate with the Java program the reference antenna module is connected to the laptop over USB now we will discuss the fabrication of the antennas after simulating the two intended designs in anisoft hfss each
00:03:27 design was placed on a PCB using KS IAD each PCB contains all of the electronics for the modules on the back plane of the antenna including the antenna biasing circuit the XB radio and the Tec microcontroller we fabricated the boards ourselves using a milling machine but the design files can also be F manufactured inexpensively by a PCB fabrication company you can download the
00:03:53 design files at the Huff research group Wiki or the aps competition site once our boards were fabricated headers for the XB radios and the teensi microcontroller were soldered onto the boards along with other electronic components like voltage regulators and bias resistors through plotting radiation patterns our system is able to
00:04:13 demonstrate a wide range of antenna principles the radiation patterns alone in addition we are able to find the number of packets lost during a measurement routine as the aut rotates it will transmit its current degree configuration State and number of packets sent back to the reference antenna the Java program will use the RSSI data and configuration state to
00:04:35 plot the radiation pattern in real time the LEDs at the ends of the arms of the antenna will indicate the biasing of the antenna overall the polarization and pattern reconfigurability of the antennas allow for a lowcost easyto use measurement system that be can be expanded to perform more advanced and dynamic tasks