RFL 9780 RFL Electronics Inc.
April 8, 2003 14-2 (973) 334-3100
14.2 SPECIFICATIONS
As of the date this manual was published, the following specifications apply to all RFL 9780
Limiter/Slicer modules, except where indicated. Because all RFL products undergo constant refinement
and improvement, these specifications are subject to change without notice.
Discriminator/Slicer detection:
Shift Frequency:
106430-1 & 106430-11: 100 Hz
106430-2 & 106430-12: 250 Hz
106430-3 & 106430-13: 500 Hz
Shift Direction: Selectable using programmable jumper J1 in accordance with Table 14-1.
14.3 THEORY OF OPERATION
For the following discussion of the RFL 9780 LM/SL module, refer to the block diagram in Figure
14-2 and the schematic diagram in Figure 14-5.
14.3.1 OVERVIEW
The 4 kHz signal out of the CLI module is fed into two circuit branches in the Limiter/Slicer Module.
One branch performs the Limiter/Slicer functions while the other is an envelope detector. The
Limiter/Slicer consists of an input limiter followed by an active discriminator, which shifts the signal
by 90 degrees (at 4 kHz). This is followed by another limiter circuit. The two limited signals are then
combined using an exclusive-OR which produces a 50% duty cycle 8 kHz squarewave (with 4 kHz in).
The signal from the input limiter is passed through another exclusive-OR which may be used to invert
the signal. Inverting the signal results in swapping the phase relationship between the two limiter
signals. This, in turn results in swapping the subsequent circuitry’s response to a shift up versus a shift
down in frequency. Note that this feature is rarely used. Receiving a trip-up signal is accommodated by
switch SW8-2 on the Logic Module as described in paragraph 6.4.17.
The 8 kHz signal is fed through a low pass filter to extract the dc component (average value) of the
signal. This signal is then normalized by an amplifier stage with variable gain and offset adjustments.
The resulting signal is fed into two slicer circuits (guard and trip). The guard and trip outputs can be
disabled by using the block input.
The envelope detector circuit consists of a precision full-wave bridge rectifier followed by a low pass
filter. This converts the amplitude of the input signal to an averaged dc level. The output of the low
pass filter is then passed through a corona filter which has three notches to block the effects of corona
discharge on the signal.
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