A major upgrade to Barracuda Mark VII is the addition of a new
and improved passive sonar system. Led by Daniel Naito, the
electronics team revamped the once problematic and inaccurate system. While the physical
arrangement of the hydrophone array stayed the same, its functional operation has been radically changed. This year’s hydrophone data will be
processed by a array of microcontrollers communicating over a shared CAN (Controller-Area Network) bus. Here is a brief break down of the hydrophone processing operation.
1
The audio is amplified by a pair of National Semiconductor LMH6646 high speed operational amplifiers at a gain of approximately 15dB.
2
The
signals are paired off and received by three dsPIC30F4012's, which are
Microchip PIC microcontrollers optimized for digital signal
processing.
3
The dsPICs
filter out the erroneous frequencies, and further amplify
the signal. Each calculates the phase difference between
a pair of signals, and sends the phase information over a CAN
(controller-area network) bus to a fourth dsPIC.
4
The fourth
dsPIC uses hyperbolic positioning to find a directional
vector towards the pinger. The same CAN bus is used to send
the pinger's direction to the main control system. The main control board combines this data with the depth reading to get an approximate location of the pinger relative to the submarine.
