Global Positioning System Reference
In-Depth Information
GPS Signal
In order to design a software-defined single frequency GPS receiver it is neces-
sary to know the characteristics of the signal and data transmitted from the GPS
satellites and received by the GPS receiver antenna. In this chapter an overview
of the GPS signal generation scheme and the most important properties of the
various signals and data are presented.
2.1
Signals and Data
The GPS signals are transmitted on two radio frequencies in the UHF band. The
UHF band covers the frequency band from 500 MHz to 3 GHz. These frequencies
are referred to as L1 and L2 and are derived from a common frequency,
f
0
=
10
.
23 MHz:
f
L1
=
154
f
0
=
.
,
1575
42 MHz
(2.1)
f
L2
=
120
f
0
=
.
.
1227
60 MHz
(2.2)
The signals are composed of the following three parts:
Carrier
The carrier wave with frequency
f
L1
or
f
L2
,
Navigation data
The navigation data contain information regarding satellite or-
bits. This information is uploaded to all satellites from the ground stations
in the GPS Control Segment. The navigation data have a bit rate of 50 bps.
More details on the navigation data can be seen in Section 2.6.
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