GBAS/SCAT-I Mode (Options R&S
EVSG-K4/-K5)
R&S
®
EVSG1000
172
User Manual 1178.6227.02 ─ 06
Figure 6-1: GBAS components and signals (simplified representation)
1 = GNSS reference receiver
2 = GBAS ground station
3 = VHF data broadcast (VDB) transmitter
a = GNSS navigation message
b = Pseudorange
c = GBAS Correction message
d = VDB signal
The GBAS GNSS reference receivers receive the
GNSS navigation message
, perform
pseudorange measurements and transmit this information to the GBAS ground station.
The GBAS ground station determines errors in the calculated positions, adds additional
parameters and approach path information, produces a
GBAS correction message
and
sends it the VDB transmitter. The VDB transmitter modulates and encodes this mes-
sage and
broadcasts
it to the airborne GBAS equipment, for example a GBAS receiver
in the airplane. The GBAS equipment in the airplane is a high-precision multimode
receiver that evaluates the message and applies corrections parameters to improve
the navigation algorithms from GPS.
This list outlines the three signals transmitted between the components and referred to
as GBAS Signal-in-Space:
●
GNSS satellite to GBAS ground subsystem navigation signal
●
GNSS satellite to GBAS airborne subsystem navigation signal
●
GBAS ground subsystem to GBAS airborne subsystem VHF data broadcast
Carrier frequencies and frequency channels
The VHF data broadcast is defined for carrier frequencies within the range of
108.025
MHz to 117.950
MHz and carrier spacing of 25.0
kHz.
Basics on GBAS and SCAT-I Analysis
