Klein Marine Systems, Inc. HydroChart 5000, Operation And Maintenance Manual

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1-6
CHAPTER 1 Overview
HydroChart 5000 Sonar Operations and Maintenance Manual P/N 11210080, Rev. 02
sub-arrays and three bathymetry sub-arrays that operate as receive elements. There
is also a separate transmit line array included that projects acoustic energy to the
seabed.
The Sonar Head Unit sonar electronics includes a Transmitter board, two Receiver
boards and a Multiplexer board. A block diagram of the Sonar Head Unit is shown
in Figure 1-3.
Transmitter board.
The Transmitter board produces a transmit pulse, at the
start of a swath, that ensonifies the sea floor over a defined footprint. The
Transmitter board is composed of two individual transmitting channels, one
connected to the port array and the other connected to the starboard array. The
transmitters operate at a center frequency of 455 kHz and support both CW and
chirp waveform transmission. The Transmitter board also contains transmit
and receive circuitry for the altimeter.
Receiver boards.
The Receiver boards process the backscatter information by
applying fixed gain, time varied gain (TVG) and frequency filtering to the
input voltage signals received from the individual sub-arrays in the transducer
arrays. There are two Receiver boards, one for the port array and one for the
starboard array. Each of the receiver channels is bandpass filtered with tightly
matched filters providing a -3dB bandwidth of 20 kHz, centered at 455 kHz.
The filtered signal is then output to the Multiplexer board for sampling.
Multiplexer board.
The Multiplexer board digitizes the signals from each of
the transducer sub-array channels along with the signals from the sensors,
encodes the data, and transmits a high baud rate digital data stream to the TPU
over the deck cable. The Multiplexer board also receives the trigger signal and
command messages which instruct the Transmitter board to fire the arrays and
configure aspects of the sonar operation. In addition, the Multiplexer board
functions as a motherboard for the other boards providing the connections and
distributing power. The Multiplexer board uses a proprietary sampling scheme
that preserves the phase of the individual channel signals, but only requires a
single A/D converter, thereby reducing cost and power consumption while
eliminating the phase mismatch between converters of alternate dual converter
schemes. The output of the A/D is input to the data encoder and converted to
serial data for subsequent transmission over the deck cable. A full duplex
hybrid allows data transmission up the cable while simultaneously receiving
the FSK trigger signals and power. The downlink signals are input to FSK
demodulators, and the baseband outputs are routed to the Transmitter board,
indicating when to fire the main array, and to a micro controller that handles
the sonar configuration.
NOTE
The transducers are side specific and are not interchangeable.