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2. CIRCUIT DESCRIPTION
2.1 TRANSMITTER UNIT
2.1.1 Board Function
Refer to the block diagram shown in figure 2.1. The transmitter unit consists of five PC
boards. The table below shows the major functions of each PC board.
Board
TRS. A 01 P5742
TRS. B 01 P5743
SEN 01 P5744
CO NT. A
01P5740
CONT. B 01P5741 1) D/A conversion and frequency modulation of signals transmitted
2.1.2 Power ON/OFF Control
When the transmitter unit reach at 10 m deep in the water, the pressure switch is turned on
and activates the + 5 and 15 V regulator on the CONT A board. And the transmitter unit
starts functioning automatically. When the transmitter unit rises above 10 m, the pressure
switch is turned off, and the transmitter unit stops functioning.
2.1.3 Upward and Downward Soundings
Transmitter Circuit
The transmitter circuit for upward and downward soundings are incorporated on TRS.
A and TRS. B boards. For the 75 kHz transmission, the 1.2 MHz signal generated by the
CPU on the CONT A board is frequency-divided by 16 to 75kHz and 1.4 MHz generated by
a crystal oscillator on the TRS.A board is divided by 8 to 175 kHz.
These 75 kHz or 175 kHz clock signals are applied to the succeeding gate circuit, where it
is gated by 0.2ms long TSMT pulse from the CPU, and then sent to the power amplifier.
The power amplifier amplifies the transmission signals to 100W and sent to the sounding
transducer via the output transformer and the T/R circuit. The T/R circuit links the
transducer to the transmitter circuit during transmission and to the RF amplifier during
reception. Relay K1 selects the transducer for upward or downward sounding and is
controlled by the CPU via the UP/DN CONT circuit.
Figure 2.2 and 2.3 show the transmitting waveform and TSMT signal.
Major Functions
1) Generates upward/downward sounding TX signals.
2) IF amplifier, mixer, and detector of received signals.
3) TVG control of received signals.
4) A/D conversion of received signals.
1) Power amplification of upward/downward sounding TX signals.
2) RF amplification of received signals.
1) Depth/water temperature measurement.
1) Control of transmitter, receiver and signal transmitter circuits by
CPU.
2) Acquisition and processing of A/D converted received signals.
3) Power amplification of signal transmitted to paravane receiver.
toward paravane receiver.
2) A/D conversion of depth and water temperature signals for
acquisition by CPU.
3) Presetting of transmitter unit operation mode.
2-1
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