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Appendix A
the secondary winding. The voltage is rectified, and filtered at the power
filter (PWR FILTER). External DC-supply voltage and internal batteries
are connected through diodes. A battery power switch located at the front
panel is common to both DC supplies. The DC supplies and the rectified
mains supply are connected together at the power filter.
This unregulated DC supply voltage is connected to the auxiliary regulator
(AUX. REG.), which pre-regulates the supply to about 16 volts (VDD3); it
also produces a regulated 5 volts supply (VDD2). These voltages are pre-
sent as long as mains, or the internal/external DC-sources are connected.
The main power control (MAIN PWR CONTROL) enables the DC/DC
switching regulator (DC/DC-CONV.) under CPU control. It enables the
main 5-volt power (VDD1) to the Electronics Unit; VDD1 supplies the
CPU, the timing generator circuitry, bus interface logic, part of the off-
board I/O, the recorder, and the front panel interface. VDD2 supplies vola-
tile memory (RAM), volatile configurable logic circuits, and the real time
clock (RTC) with standby power. In addition, the RTC is also backup-
powered by a 250 mAh Lithium coin cell, which maintains its calendar and
alarm settings if all power is off.
To save power also when the Electronics Unit is "awake", that is if VDD1
is switched on, additional power management is provided. The CPU can
enable power via the receiver power strobe switch (RCV PWR STROBE)
to the receiver portion of the ADFM, which includes the receiver amplifier
(RCV-AMP), the mixers, the low pass filters (LPF) the limiting amplifiers
(LIMITER), and the data acquisition circuitry (FIFO, CORRELATOR) as
its main components. Also the 2.50-volt reference voltage VR1 is con-
trolled by the same switch. The CPU controls also the transducer power
strobe switch (XDCR PWR STROBE), which enables a 7.9-volt regulator.
After additional filtering and power supply decoupling, it supplies the
transducer and transmit amplifier (XMT-AMP) with power.
To increase reliability and reduce power consumption, all power strobes
and controls are solid state devices.
A-2.2
Receiver
The transducer output signal (RCV-SIG) is routed to the receive coupling
transformer (RCV-XFMR) that provides isolation and impedance matching.
The signal is further amplified and bandwidth limited by a high gain selec-
tive log-amplifier (RCV-AMP) circuitry. The amplified receive signal is
fed to a frequency mixer, where the signal is mixed multiplicatively with
the local oscillator (LO) frequency. The desired base band signal, which is
the difference frequency of the receive signal and the local oscillator fre-
quency, is obtained by passing the mixer output signal through a low pass
filter. The base band signal contains now the entire Doppler spectrum with-
out the carrier signal.
page A-2
MGD Technologies, Inc.
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