Automatic Directional Antenna Azimuth Controller Cezanne Camacho, Andrew Curtis, and Tyler Bowen Department of Electrical Engineering, University of Washington, Seattle, WA electrical engineering The Automatic Directional Antenna Azimuth Controller (ADAAC) is a low power assembly consisting of: a passive radar bearing detection array, directional transmission antenna, and motor controller with a feedback loop designed for mobile platforms to increase the mobile platform’s signal range and to minimize the power required to transmit data remotely. This design is customized for use in a Mars Rover control station which will be required to receive and transmit data to and from a Rover mobile unit, and having a dedicated directional transmitter would increase the control station's effective range. This design will be easily adapted to multiple platforms and hardware options. Project Description A successful completion of this project will be for our design to detect a transmitted 915 MHz signal (provided by XBee transceivers) and its bearing relative to the platform's position, and direct the directional antenna towards the signal as we move the position of the signal. The signal may be up to 1 km away from the directional antenna. Our whole unit must be able to fit within the bounds of the space we are allowed on the control station, which is about a 5 by 5 foot square. Goal Testing Individual Components We encountered a challenge when testing the phase detectors: We encountered redundancy when testing the rotary encoder: Methods and Results Design Changes After testing the components, we changed our design to minimize the noise in our signal detection system by removing the main source: phase detectors, and switching to the XBee‘s signal strength detector as a means of locating the direction of an incoming signal relative to the two receiving antennas. We also simplified our design by incorporating a stepper motor that was capable of rotating our platform and having its position controlled by an Arduino Mega Controller instead of using a rotary encoder and DC motor in tandem for the same purpose. Control System Discussion and Control System Our final product rotates reliably with a moving signal that is up to 1 km away from our system. Final Product Professor Howard Chizeck T.A. Kevin Huang Professor Robert Darling and use of the RF Lab and Agilent Technologies equipment Acknowledgements Figure 1. Diagram of the ADAAC, with directional arrows indicating the flow of information between components 1) XBee Transceivers We set up the transceivers to be on the same channel; synchronized with the same baud rate, and attached to antennas, then sent serial data from one to the other to test the range. The data was successfully transmitted up to 1 km. 2) Stepper Motor Attached to our rotating base and controlled using a Motor Shield on an Arduino Mega Controller. We use the “double” mode, which gives us the most torque, and we control the motor by specifying which direction and how many steps to take. 3) Phase Detectors  XBee Signal Strength Detector Attached to the XBee transceivers; when a signal is detected, the phase detectors output a phase difference indicated by a voltage: V. The output is extremely noisy! We switched to the signal strength detector built in to the XBee’s and use that to detect the relative location of the signal. 4) Rotary Encoder  Just the Stepper Motor When attached to our rotating base, this outputs a gray code which we translated into a position number between The stepper motor also gives us a relative position when attached to our rotating base. Figure 2. (Left) The two receiving XBee transceivers. (Right) The same transceiver connected to an explorer board for programming Figure 3. (Left) The offending phase detector. (Middle) A clean oscilloscope phase difference reading. (Right) Observed environmental RF noise.