The goal of the Utility Acoustic Modem (UAM) effort is to produce a completely self-contained, autonomous acoustic modem capable of moderate communication rates with low power consumption. Emphasis is on robust data transfer with automatic re-transmission and data-rate selection to ensure data integrity and minimum power supply consumption. The UAM will be demonstrated at AOSN preparatory deployments in 1997 and will be a part of the 1997-98 Labrador Sea AOSN.
UAM Key Specifications:
1. Size
6" x 3" main electronics; single main board with plug-on pre-amp design
2" x 3" power amplifier (separate from main board to reduce switching noise)
will fit in 8" x 3" (i.d.) Pressure housing excluding batteries
2. Power Consumption (including DC-DC convertor loss)
Receiving: 8 W
Transmitting: 1W + 1.3 Po, P. = power into source, e.g., using Datasonic ATM-18DT 15 kHz source with 170 dB/W (directional) at a 180 dB S.L.
3. Main Board
Texas Instruments TMS320C44-60 60 MHZ DSP with 1 MWord of 1 wait-state RAM and 1 Mbyte of data storage in Non-Volatile RAM
4 ADC channels, 0-100kHz sampling rate
2 DAC channels, 0-100kHz sampling rate
Real-time clock
2 serial ports
20 parallel input/output and timing lines
4. Power Supply
Main supply 18 - 50V Reserve supply 6 - 18V
Switching to Reserve Supply in the absence of the Main Supply is automatic. Normal operation can continue or a special behavior can start (e.g., beacon or shutdown).
1. Evolved concept of how acoustic communications will be used in Labrador Sea Experiment:
Vehicle to dock (one way) Dock to ship/sonobuoy Dock to dock Dock to vehicle (very low rate ABORT' signal
2. Algorithm and implementation breakthrough for Autonomous acoustic modem
Automatic selection of receiver settings based on the current acoustic environment
Improved low-complexity receiver design suitable for use in a low-power single processor system
Enhanced Doppler tracking and correction for moving source/receiver
Robust detection and timing initialization algorithms
3. Operating system development for the UAM (AMS)
Rapid software interface to vehicles and instruments
Provides common platform for implementation and performance evaluation of Northeastern University/WHOI algorithm improvements
Built-in support for multi-rate fallback robust communications
Allows other functions to be added with low development cost (e.g., USBL, LBL, Doppler velocity, mono-static sonar)
4. UAM design
Now completing schematic capture. Prototype testing in late December/early January
Ground-up design for low-power, low cost. Directly supports AMS and the autonomous receiver/transmitter software
See specifications sheet
Software controlled instrument interface and wide range of power supply options will make vehicle installation fast
Fulfills most requirements in returned 'Modem Survey' forms
High efficiency Sigma-Delta, variable Q power amp in development