Avionic Standards
R&S
®
SMA100B
133User Manual 1178.3834.02 ─ 05
"Down"
The 90 Hz modulation signal is predominant, the DDM value is posi-
tive (the airplane is too high, it must descend).
Remote command:
[:SOURce<hw>]:ILS[:GS|GSLope]:DDM:DIRection on page 554
DDM Step
Selects the variation of the DDM values.
"Decimal"
Decimal variation according to the current cursor position.
"Predifined"
Variation in predefined steps according to the standardized DDM val-
ues.
Remote command:
[:SOURce<hw>]:ILS[:GS|GSLope]:DDM:STEP on page 555
DDM Current
Sets the current of the ILS indicating the instrument corresponding to the DDM value.
The instrument current is calculated according to:
DDM Current µA = DDM Depth [%] × 857,125 µA
A variation of the instrument current automatically leads to a variation of the DDM
value and the DDM value in dB.
Remote command:
[:SOURce<hw>]:ILS[:GS|GSLope]:DDM:CURRent on page 553
DDM Depth
Sets the difference in depth of modulation between the upper lobe (90 Hz) and the
lower lobe (150 Hz) tone of the ILS glide slope modulation signal.
The DDM value is calculated with the formula:
●
"DDM Polarity > 90 Hz - 150 Hz":
DDM = [ AM (90 Hz) - AM (150 Hz) ] / 100%
●
"DDM Polarity > 150 Hz - 90 Hz":
DDM = [ AM (150 Hz) - AM (90 Hz) ] / 100%
A variation of the DDM value automatically leads to a variation of the value of the
instrument current and the DDM value in dB.
Remote command:
[:SOURce<hw>]:ILS[:GS|GSLope]:DDM[:DEPTh] on page 556
DDM Logarithmic
Sets the DDM value in dB. The dB value is calculated according to:
DDM dB = 20 × LOG [(SDM+DDM×100%) / (SDM-DDM×100%)]
A variation of the value automatically leads to a variation of the DDM value and the
instrument current.
Remote command:
[:SOURce<hw>]:ILS[:GS|GSLope]:DDM:LOGarithmic on page 554
DDM Percent
Sets the difference in depth of modulation between the upper lobe (90 Hz) and the
lower lobe (150 Hz) tone of the ILS glide slope modulation signal.
ILS Configuration and Settings
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