As air transport continues to grow, the use of Global Satellite Navigation Systems (GNSS) for Flight Navigation

is increasing. So too is the move towards using systems that support Required Navigation Performance

(RNP). Augmentation Systems to GNSS, both Satellite-Based Augmentation Systems (SBAS), such as Wide

Area Augmentation System (WAAS) and European Geostationary Navigation Overlay System (EGNOS) are

already in use but the adoption of the Local Area systems such as the Ground-Based Augmentation Landing

System (GBAS Landing System) for airport precision approach and category I, II, and III landing operations is

on the rise. A critical system such as this must meet stringent performance indicators for RNP and be sure to

maintain accuracy and stability under the full range of real-world conditions.

In order to help developers and integrators to test the airborne GNSS receiver in their GBAS Landing System,

GSS4150

The integrated solution to GNSS + GBAS functional testing

No. 1

The rst source is the error modelling

applied to a simulated GNSS reference

receiver, the location for which is user-

specied. The various simulated system

effects are calculated and the resulting

errors are compiled into the differential

transmitter location and

the simulated aircraft

position, and in response

to the simulated VHF

antenna reception pattern.

No. 2

The second source is the xed data entered by the user

via detailed on-screen forms that is required by message

types 2 and 4, and for some elds associated with

message type 1. The GSS4150 varies the signal level in

response to the distance of separation from the dened

simulated transmitter location and the simulated aircraft

GSS4150B

Data messages are constructed in real time from two sources associated with the host GNSS Simulator:

Airport

Authorities

Airline

Operators

Avionics

System

GBAS

System

Integrators

Specications

The GSS4150 comprises a VHF signal source generator and software extensions contained within Spirent’s

Maximum

0.025MHz

Symbol Rate Fixed 10.500 symbols/s

Modulation D8PSK

TDMA Timing Reference RTCA DO-246 As ICD

Maximum Signal Level At RF port

(represents modelled received power at VHF antenna)

-50dBm

-40dBc

Message Types 1 2 3 Differential Corrections 100 second smoothed pseudoranges

Message Type 2 GBAS related data

Message Type 4 FAS and TAP construction data

Message Types 5 2 3 Ranging Source Availability

Message Types 11 2 3 Differential Corrections 30 second smoothed pseudoranges

Uncertainty in calibrated simulated power at

maximum power power level

an external reference from the simulator, and is

dependent on its calibrated accuracy.

Master clock may be manually adjusted to < 0.02Hz

error at calibration interval (1 year).

GSS4150

Front Panel

Provides the primary RF GPS signal

output at specied levels.

50 ohm

VSWR <1.2:1 (band)

DC isolated

External reference

Rear Panel

references