drive a subsequent mechanism without disruption. It is easy to see that thisdrive a subsequent mechanism without disruption. It is easy to see that this
effect gets better, the higher the inertia of the wheel is. At the same time theeffect gets better, the higher the inertia of the wheel is. At the same time the
flywheel howeverflywheel however, loses the ability to , loses the ability to follow rapid changes in the follow rapid changes in the revolutionsrevolutions
per minute, i.e. the per minute, i.e. the dynamic response of the drive system gets worse. Thedynamic response of the drive system gets worse. The
same correlation also applies to the same correlation also applies to the electronic trackinelectronic tracking filter which thusg filter which thus
always represents a compromise between the regeneration effect and thealways represents a compromise between the regeneration effect and the
dynamic tracking behavior of the dynamic tracking behavior of the input signal. Basicallyinput signal. Basically, good , good dropoutdropout
elimination or noise suppression is always involved with limited dynamicelimination or noise suppression is always involved with limited dynamic
response. If the response. If the maximum acceleration is exceeded, the maximum acceleration is exceeded, the synchronizasynchronizationtion
between the input signal and the oscillator is lost (the tracking filter loses lock)between the input signal and the oscillator is lost (the tracking filter loses lock)
which leads to drastic signal distortions at the which leads to drastic signal distortions at the signal output. Practical advicesignal output. Practical advice
for setting the tracking filter can be found infor setting the tracking filter can be found insec
sectiotionn 4.24.2.3.3..
The internal structure of the The internal structure of the tracking filter circuit is shown intracking filter circuit is shown infi
figugurere C.C.22. The. The
function of the voltage controlled oscillator (VCO) has already beenfunction of the voltage controlled oscillator (VCO) has already been
mentioned. The control signal which synchronizes the oscillator is generatedmentioned. The control signal which synchronizes the oscillator is generated
in the phase in the phase detector which monitors the phase difference between the inputdetector which monitors the phase difference between the input
signal and the oscillator signal. The signal and the oscillator signal. The dynamic characterisdynamic characteristics of thetics of the
configuration are mainly determined by the internal low pass filter. Theconfiguration are mainly determined by the internal low pass filter. The
maximum acceleratiomaximum acceleration which the tracking filter can n which the tracking filter can still follow depends on thestill follow depends on the
filter bandwidth. The low pass time constant is switched between SLOW andfilter bandwidth. The low pass time constant is switched between SLOW and
FAST via the system control and thus adapts the dynamic characteristics toFAST via the system control and thus adapts the dynamic characteristics to
the application. The tracking filter can be turned off via a bypass if thethe application. The tracking filter can be turned off via a bypass if the
accelerations are too high or in the case of good accelerations are too high or in the case of good optical signals.optical signals.
Down-mixiDown-mixing of the ng of the frequency in the input frequency in the input section is required to convert thesection is required to convert the
carrier frequency of the input signal from 40.4carrier frequency of the input signal from 40.4MHz originally to lowerMHz originally to lower
intermediate frequencies. With these intermediate intermediate frequencies. With these intermediate frequencies, the velocityfrequencies, the velocity
decoder can work optimally in decoder can work optimally in the individual measurement ranges. Down-the individual measurement ranges. Down-
mixing is carried out by a mixing is carried out by a mixing process which does not affect the modulationmixing process which does not affect the modulation
content of the FM signal. content of the FM signal. The variable frequency fThe variable frequency f
LOLO
is produced by the so-is produced by the so-
called local oscillator in a called local oscillator in a fixed relationship to the drive frequency of fixed relationship to the drive frequency of thethe
Bragg cell.Bragg cell.
Figure C.2: Block diagram of the tracking filter circuitFigure C.2: Block diagram of the tracking filter circuit
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