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Output Section Attenuator
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Fig.5.3. Output section block diagram
The output section is split into several stages in order to obtain the best
possible signal-to-noise ratio. The attenuator is split into three sections, each
with an attenuation of 0, 10 or 20 dB. This gives a total attenuation of
60 dB in 10 dB steps. Situated between the attenuators are two amplifiers,
each providing 20 dB gain.
The final amplifier stage separates the signal into two components. The
component which is in phase with the input signal is amplified by 30 dB.
The anti-phase component is amplified by 40 dB. This component is then
fed to the R MS detector.
Output Overload Indicator
An overload indicator is placed at the amplifier output in order to safe-
guard against signals of too high a peak value. It is driven by the two output
signal components, i.e. in-phase and anti-phase components. It is also con-
nected in parallel with the input overload indicator to the overload relay.
5.2.3. RMS Detection and Averaging
Circuits for extracting the RMS value of an alternating signal consist in
42
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