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No. 2D730-148E*O
4)
5)
Selectable gain amp
The Doppler signal level differs for each transducer.
Therefore, the signal level
can be selected from 0 to 16 dB in 2-dB steps.
Selection is performed by the address decoder (EPLD) based on code of the TC
bus (BBGAIN).
ADC
After performing
IO-MHz sampling in
Z-A
type ADCs, the frequency
element
156.25 kHz or more is eliminated in the digital filter and decimation is performed
at the 312.5 kHz. The signals are output as serial data.
The signals in the two ADCs (in-phase/quadrature-phase)
are synchronized
with
the system clock via the EPLD and are output to the BE board.
The I/Q signals in the two ADCs are combined into one synchronization
signal
with the serial data and they are then transferred in the differential format.
(c)
Clock generation
circuit (plus generator/LO)
In order to generate the reference clocks for mixers and the pencil CW transmission
clock, the TXPG is configured to operate in infinite number of pulses mode (INPM).
The PECL clock (four-phase,
40 MHz) is input to the TXPG and the frequency is set
based on the TC bus data.
(d)
Pencil CW transmitter/receiver
I>
2)
Pencil CW transmitter
The pencil CW transmission
circuit drives the pencil transducer
piezoelectric
elements.
The TXPG outputs the clocks Houtl and Lout1 to the ACT08.
This is
controlled by the transmission
enable signal (TXENI).
The ACT08 drives the
MOSFET and performs bipolar transmission
by driving the transformer
alternately.
The transmission signal is transferred to the pencil transducer via the TI board.
Pencil CW receiver
The reception signal returned from the pencil transducer is input to the
preamplifier of the CB board via the TI board. After the weak signal from the
transducer
is amplified in the preamplifier, the CW receiver is connected to the
selectable BPF and quadrature
demodulation
circuit by switching the multiplexer.
The signal sent via the same route as for SCW summation
and is processed.
4-19
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