NF FRA5097, Instruction Manual

Page: 28 / 192

1.4 Principle of operation
FRA5097 1-12
Operation of the FRA5097 Frequency Response Analyzer will be described according to
“Fig.
1-3 FRA block diagram”
.
a)
OSC BD
This is an oscillator that generates timing signals for this instrument.
The OSC BD generates the three following types of signals: sampling clock signals for A/D
conversion, local frequency signals for heterodyne and oscillator output signals.
This oscillator has a setting resolution of 0.1 mHz
(1 mHz at 10 MHz or higher)
for the
frequency range of 0.1 mHz to 15 MHz, due to its use of direct digital frequency synthesizer
technology using dedicated LSIs. It has features of, for example, capability of instantaneous
frequency change with phase continuity, etc.
b)
PREAMP BD
The PREAMP BD is a type of preamplifiers composed of an amplifier with variable gain and an
A/D converter.
The input signal will have its DC component removed and be amplified or attenuated to an
appropriate level to be A/D-converted to a 16-bit signal. If the analysis frequency is below 3
kHz, the signal will be directly A/D-converted. If the analysis frequency is above 3 kHz, the
signal will be A/D-converted after it is converted to the intermediate frequency of
approximately 55 Hz through a frequency conversion circuit.
c)
AD CPU BD
The digital data signal that has been A/D-converted through the PREAMP BD will be
Fourier-integrated and stored as measurement data in the AD CPU BD. the AD CPU BD
contains a 16-bit CPU and controls the auto-range function of PREAMP BD, which is in
addition to its function of Fourier integration.
d)
MAIN CPU BD
The MAIN CPU BD reads measured data from the AD CPU BD, performs coordinate transform,
error compensation, etc. and displays the outcome on the LCD. It also controls the keyboard,
the floppy disk and the GPIB.
e)
DCPS BD
The DCPB BD supplies isolated electric power with high impedance to the CH1/CH2
preamplifier and the OSC.