Viavi 87339, Operation Manual

Page: 125 / 198

Principals of Operation
6 -8
satellite’s position at any time and combine this with the receiver distance from the
satellite, yielding a GPS position.
Fig. 6-9 Satellite Relative Position
The health information transmitted in subframe 5, is critical to prevent a receiver from
using the ranging information from a satellite that has been declared unfit for navigation
purposes.
The remainder of the information found in the data stream (clock corrections, ionospheric
model, UTC data) are used to resolve potential sources of GPS position errors.
6.1.4.B Code and Frequency Correlation
The power of the received GPS signal in open sky is at least -160 dBW (-130 dBm). The
maximum of the spectral power density of the received signal is -190 dBm/Hz. The
spectral power density of the thermal background noise is approximately -174 dBm/Hz (at
a temperature of 290 K). Refer to Fig. 6-10. The maximum received signal power is
approximately 16 dB below the thermal background noise level
Fig. 6-10 GPS Received Signal