148 Keysight EXG and MXG X-Series Signal Generators User’s Guide
Avionics VOR/ILS (Option 302)
Using ILS Glide Slope Softkeys
To set the ILS Glide Slope DDM value
This process sets a value for the “Difference in Depth of Modulation” (DDM).
1.
Press Aux Fctn > Avionics > ILS Glide Slope
2.
Press DDM/SDM
3.
Press DDM
(Default value is 0.0000.)
4.
Enter a value that is within the range of the current SDM value.
Typically the SDM default value provides sufficient range (–0.80 to 0.80)
for most applications.
If SDM is set to 99%, then the full range (-0.99 to 0.99) of DDM is
available. The following demonstrates the limits of DDM’s range:
(–SDM/100) to (SDM/100)
As SDM’s value increases or decrease, so does DDM’s range.
The primary mechanism which makes it possible for a pilot to obtain guidance
to a runway is the aircraft receiver's ability to detect the “Difference in Depth of
Modulation (DDM)” between this 90 Hz and 150 Hz amplitude modulation.
DDM is defined to be the “percentage modulation depth of the larger signal”
minus the “percentage modulation depth of the smaller signal”,
divided by 100.
DDM = [AM(90 Hz)% - AM(150 Hz)%] / 100
To set the ILS Glide Slope DDM value in micro-amps (
μ
A)
This process sets a value for the difference in depth of modulation (DDM)
expressed in
μ
A.
1.
Press Aux Fctn > Avionics > ILS Glide Slope
2.
Press DDM/SDM
3.
Press DDM uA
(Default value is 0.0
μ
A.)
4.
Enter a value that is within the range of the current SDM value.
Typically the SDM default value provides sufficient range for most
applications.
If SDM is set to 99%, then the full range (–846.6 to 846.6
μ
A) of DDM uA is
available. The following demonstrates the limits of DDM uA’s range:
((–SDM/100)*(150/.175)) to ((SDM/100)*(150/.175))
As SDM’s value increases or decrease, so does the range.
