8. DigiLock User Interface (DUI)
Page 33
Status: 5.12.17
8.2.5.2 LI/PDH
Figure 21 LI/PDH tab in the Settings function
Modulation signal type: Type of the waveform used for modulation and demodulation.
First filter notch
(LI-Module): The LI module only works properly if a low-pass filter is applied to the
demodulated signal in order to filter frequency components located at
the modulation frequency. This filter is implemented as a “moving aver-
age” filter in the digital domain. The first notch of such a filter is at the
modulation frequency. In order to reduce noise this first filter notch can
be set to lower frequencies. It must be taken into account that a mov-
ing average filter introduces a linear phase shift to the output signal of
the LI module. At the first notch frequency the phase shift is -180 °. As a
consequence, lowering the filter frequency reduces the maximum
available regulation bandwidth !
AIO1out selection: The AIOout output channel can be configured to display the LI- or PDH-
error signal. Please note that the bandwidth of this signal is limited to the
output channel bandwidth.
8.2.5.3 Simulation
Figure 22 Simulation tab in the Settings function
Elements to include
in calculations: Checkboxes allow to include or exclude signal path elements in the
transfer function simulation.
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