Numeric Measurement Modes
R&S
®
EVSG1000
56
User Manual 1178.6227.02 ─ 06
Figure 4-1: Approach navigation using instrument landing system (ILS)
Typically, vertically aligned antennas transmit two intersecting main beams on top of
one another at carrier frequencies between 329
MHz and 335
MHz. The top beam is
usually modulated at 90
Hz and the beam below at 150
Hz.
The information on position is provided after demodulation of the beam signals by eval-
uating the difference in depth of modulation (DDM). The following scenarios are possi-
ble:
●
Predominance of the 90
Hz beam: the aircraft is too high and must descend
●
Predominance of the 150
Hz beam: the aircraft is too low and needs to climb
●
The signal strength from both beams is equal: the aircraft is in the center, on the
right course.
If there is a predominance of the 90
Hz beam, then the aircraft is too high and must
descend. A predominant 150
Hz means that the aircraft is too low and needs to climb.
4.1.3
ILS Localizer and Glidepath Measurements and Results
A single receiver board in the R&S
EVSG1000 can measure data at two different
receiver frequencies at the same time. Therefore, the ILS Localizer and Glidepath
measurements can detect both course and clearance data simultaneously, and display
the individual results. Alternatively, the individual channels can be measured only, or
any one or two user-defined frequencies. By default, a wideband measurement is per-
ILS Localizer and ILS Glidepath (GP) Modes
