In this video, we will demonstrate how to create custom GPS scenarios using the Agilent
N7609B signal studio for global navigation satellite systems software with option RFP
for scenario generation. Here is the equipment set up used for this demonstration. The N7609B
signal studio software runs inside the N5106A PXB baseband generator and channel emulator
to create the GPS baseband signal in the PXB. This digital baseband signal is then sent
over an LVDS digital BUS to the N5182A MXG signal generator where it is up converted
to the GPS RF frequency and sent to the GPS receiver. A u-blox EVK-5H evaluation kit.
The GPS receiver sends its information via a USB interface to the u-blox u-Center evaluation
software for display. Let us start by showing how to create custom scenarios with the N7609B
signal studio software. On the scenario generator tab, we select "create" as the generation
mode and leave the scenario type at the default setting of "static" to create the scenario
for a stationary GPS receiver. We provide an almanac file name, input the longitude,
latitude, and altitude for the location of the scenario, provide the starting date and
time and required duration of the scenario.
The location given here is for San Francisco, California. There are also options to specify
an elevation mask angle to include modeling for impairment from the troposphere and the
ionosphere. To generate the scenario file, we click on the create scenario button and
the software will ask for a scenario file name. As you see here, a scenario with a 1
hour duration takes just a few seconds to create. Once the file has been saved, we can
go to the GPS settings tab to select and play the scenario. The resulting GPS receiver signal
is shown in the u-Center software.
Notice that the green cross on the world map indicates the general location of the GPS
receiver for this scenario. Let us now take a look at how we create dynamic scenarios
to simulate moving GPS receivers. On the scenario generator tab, we again select "create"
for the generation mode and provide the almanac file name as we did previously. This time,
we select "dynamic" as the scenario type. For dynamic scenario, we need to input the
trajectory path for the moving GPS receiver by using an NMEAGGA format file. The GGA file
contains the location information of the receiver, sampled at a set rate over the timed duration
of the scenario.
There is no need to input an initial location or time. Here we select a GGA file that was
previously created. It is for a GPS receiver that is moving clockwise around the circle
with a 1 kilometer radius at a speed of 100 kph. We also provide the start date for the
scenario. The time information will come from the GGA file. We then create and save the
scenario file. We go back to the GPS settings tab and select this new scenario for playback.
For this scenario we will use the deviation map display in the u-Center software. The
center of this circle represents the center of the 1 kilometer circular route. We can
see the results of the GPS scenario as the GPS receiver correlates the satellites and
begins to calculate the location fix. Here was see that the GPS receiver is moving in
a clockwise route around the circle with the 1 kilometer radius. The speedometer function
displays the speed of about 100 kph as we expect. In conclusion, GPS receiver verification
requires a GPS simulator capable of recreating real life scenarios. In this video, we have
demonstrated how the N7609B signal studio software can be used to create custom scenarios
for stationary and moving GPS receivers. For more information, please contact your local
Agilent technologies representative or go to the web at www.agilent.com/find/gps. Thank
you.