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N.E.P.T.U.N.E

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.

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N.E.P.T.U.N.E

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  1. 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

  2. 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

  3. Motivation • A new communication system is desired for the USF College of Marine Science’s Solar-Powered Autonomous Underwater Vehicles (SAUVs)

  4. 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

  5. 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

  6. Solution – System Overview

  7. 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

  8. Solution Simulated radiation pattern with parasitics in HFSS

  9. Solution Minimal loss in link range at new frequency

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. Solution Visual layout of the switching network:

  17. 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

  18. 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

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