L3 comminications SERIES 5000, Руководство по эксплуатации и обслуживанию, Страница: 33 / 283

1-6
CHAPTER 1 Overview
Series 5000 Sonar System Operations and Maintenance Manual P/N 11210060, Rev. 13.0
Transmitter board.
The Transmitter board produces a transmit pulse, at the
start of a swath, that illuminates the sea floor over a defined footprint. The
pulse length is nominally 100 µs. The Transmitter board is composed of six
individual transmitting channels, each of which is connected to two sub-arrays
of both the port and starboard transducer. The six transmitters operate at a
center frequency of 455 kHz while independently providing phase modulation
to reduce coherence in the transmit pulse to mitigate the effects of speckle in
the received data. The transmitters are Class-D switching types coupled
through a double tuned transformer to the transducer sub-arrays.
The Transmitter board also contains two additional auxiliary transmitters, one
for an optional externally mounted responder and one for the downward
looking 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.
The Receiver boards first process the transducer data by isolating the input
preamplifier electronics from the high voltage transmit signal via a
transmit/receive (T/R) switch. The T/R switch is automatic and requires no
intelligent control. After the transmit waveform has decayed, the switch closes
Figure 1-3:
Towfish Block Diagram