Rohde & Schwarz EVSF1000, User Manual

Page: 35 / 295

Numeric Measurement Modes
R&S
®
EVSF1000
35 User Manual 1178.6410.02 ─ 05
6 Numeric Measurement Modes
● ILS Localizer and ILS Glidepath (GP) Modes ......................................................... 35
● ILS Marker Beacon Mode (Option R&S EVSG-K3) ................................................ 56
● VOR Mode (Option R&S EVSG-K2) ....................................................................... 66
● COM Mode (Option R&S EVSG-K6) .......................................................................83
6.1 ILS Localizer and ILS Glidepath (GP) Modes
Access VNC : [m] > Down arrow key
The ILS Localizer and Glidepath measurements demodulate the AM components of
the ILS signal and calculate characteristic parameters such as the modulation depth
and frequency or phase for specific components. Furthermore, an FFT is performed on
all components of the AF signal. The resulting AF spectrum allows you to measure the
required components and their distortions (harmonics).
Remote command:
MODE_LOC
on page 205
MODE_GP
on page 205
● Localizer Basics ...................................................................................................... 35
● Glide Slope Basics ..................................................................................................36
● ILS Localizer and Glidepath Measurements and Results ....................................... 37
● ILS Localizer and Glidepath Configuration ..............................................................48
6.1.1 Localizer Basics
The localizer transmitter is located near the end of the runway (nearest to the start of
the aircraft approach). Typically, horizontally aligned antennas transmit two intersecting
main beams beside one another at carrier frequencies between 108
MHz and
112 MHz. As seen from the approaching aircraft coming in for a landing, the left beam
is usually modulated at 90 Hz and the right beam 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).
DDM = m(x90) – m(x150)
The following scenarios are possible:
●
Predominance of the 90 Hz beam: the aircraft is too far to the left and must turn to
the right
●
Predominance of the 150 Hz beam: the aircraft is too far to the right and must turn
to the left
●
The signal strength from both beams is equal: the aircraft is in the center, on the
right course.
ILS Localizer and ILS Glidepath (GP) Modes