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This project focuses on developing a beam-steerable antenna array for Solar-Powered Autonomous Underwater Vehicles (SAUVs) to enhance communication for the USF College of Marine Science. The new adaptive antenna will operate in the 2.4 GHz ISM band with an 80 MHz bandwidth, enabling increased throughput and live video support, extending the range to at least one mile. The control system autonomously selects the optimal beam steering configuration based on the SAUV's position relative to the shore, enhancing efficiency and minimizing signal loss.
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N.E.P.T.U.N.E Novel Engineering Products and Technologies for Unmanned Nautical Exploration Advisor: Dr. Weller Group Members: Kyle Chapman Bryce Hotalen Stephanie Kiley
Overview • Beam-steerable antenna array to be implemented on Solar-Powered Underwater Autonomous Vehicles (SAUVs) • Control system to autonomously select required beam steering based on SAUV position • Improved communication system will facilitate research for the USF College of Marine Science
Motivation • A new communication system is desired for the USF College of Marine Science’s Solar-Powered Autonomous Underwater Vehicles (SAUVs)
Motivation Current System: • 915 MHz ISM band radio • Omni-directional whip monopole antenna • 2-3 mile link range • Throughput sufficient for control and data transmission • Approx. 30 MHz bandwidth
Problem System Requirements: • Beam-steering capability • Low elevation radiation pattern • Ability to operate in maritime environments • Minimal impact on SAUV • High efficiency • Autonomous position-finding control system Desired Capabilities: • Increased throughput • Support live video feed • More bandwidth • At least 1 mile range • Networking enhancements • “Smart” antenna capabilities
Solution Adaptive Antenna Array: • 2.4 GHz ISM band • 80 MHz bandwidth • Single driven element (center) • Circular array of parasitics • Beam-steering by shorting a desired set of parasitic elements to the ground plane
Solution Simulated radiation pattern with parasitics in HFSS
Solution Minimal loss in link range at new frequency
Solution Antenna Control System: • Shorting set of parasitics to ground transmits in one direction • Need to determine best direction • Control system determines position of SAUV relative to shore antenna, selects and activates configuration Above: SAUV must transmit in different directions depending on its position relative to the shore
Solution Antenna Control System: Design based on received signal strength • Shore transmitter sends test signal • Record received signal strength (RSSI) • Repeat for each configuration • Configuration with highest RSSI is incident to shore
Solution Control System Flow Chart: • Select subset of configurations • Less power used, fewer resources diverted from data transmission • Prepare system for test signal • Measure RSSI • Repeat for all desired configurations • Selection algorithm • Signal switching network
Solution Control System Implementation: • Texas Instruments MSP430 – RF2500 • Low power • Integrates microprocessor and transceiver • C language programming • AnarenXinger 10 dB coupler • Divert portion of received signal to control system for evaluation • Most of signal remains on main transmit / receive line
Solution Control System Error Prevention • Periodically transmit control system status to shore for user inspection • Error Prevention - Equal RSSI measurements • Adjacent – select one configuration • Not adjacent – repeat test • Error Prevention - No signal detected • Repeat test after time interval • If no signal still detected, send error message
Solution Switching Network: • Responsible for activating and deactivating elements of the physical antenna • Physically separates the passive antenna from the ground plane • Causes a change in radiation pattern from the antenna ray • Allows the RF signal to be broadcast in a direction controlled by the microprocessor
Solution Visual layout of the switching network:
Solution Switching Network Components • Composed of six Hittite HMC550 SPST RF surface mount switches • Switches are located on a micro-strip circuit containing blocking capacitors at the RF Ports • Microprocessor will activate the switches and take the unneeded antennas out of service
Solution Switching Network Benefits • Low insertion loss (0.7 dB typical loss) • Very low current consumption (≈ 200 nA) • Compatible with CMOS and TTL logic families