Novatel OEM719, Инструкция по установке и эксплуатации

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Chapter 3 OEM7 Receiver Operation
OEM7 Installation and Operation User Manual v4 72
Measuring the RF Input Gain
This section is intended for advanced users.
The RFINPUTGAIN command allows users to enter a more accurate receiver input condition,
which is considered as a calibrated receiver input condition, and is used for interference detec-
tion. This command supports different values for L1, L2, L5, and L-Bband and is recommended
when there is a known strong interference present at receiver start up.
To calibrate the receiver input level, use a standard spectrum analyzer to measure the receiver
input noise density in dBm/Hz. Make sure the pre-amplifier is turned on in Spectrum Analyzer
under “Amplitude”. Place the Marker around L1, L2, L5, or L-Band frequency region and select
“noise density” under “Marker Function”.
RFINPUTGAIN = Receiver Input Noise Density (dBm/Hz) - Typical Thermal Noise KT of -
174dBm/Hz,
where:
K = 1.38E-23w-sec/K
T = 290 k.
For example, if the receiver input noise density measured at L1 is -144dBm/Hz,
RFINPUTGAIN = -144 – (-174) = 30dB for L1 path.
Alternatively, if a spectrum analyzer is not available, the RFINPUTGAIN can be obtained using
the cascaded RF gain before receiver plus LNA noise figure (NF), including LNA gain in antenna,
in-line amplifier gain (if applicable), RF cable or distribution loss prior to receiver input con-
nector. A typical GNSS active antenna with reasonable quality has a noise figure of ~2dB.
RFINPUTGAIN = Cascaded Gain before re LNA NF
For example, if system cumulative gain measured before receiver is ~25dB, and LNA NF is
around 2dB, the RFINPUTGAIN = 27dB.
RFINPUTGAIN L1 27
RFINPUTGAIN L2 27
RFINPUTGAIN L5 27
RFINPUTGAIN LBand 27
Statistical Analysis Detection
Statistical Analysis Detection is focused on out of band interference detection. It is sup-
plementary to the Spectrum Analysis Detection and is useful when interference is outside the
analog passband of the receiver and creating distortion that may not be visible to Spectrum Ana-
lysis Detection until the interference is very strong.
The Statistical Analysis Detection is designed as a sensitive detection tool. Out of band mit-
igation does not impose much penalty when enabled and it brings awareness to unintentional
interferences next to GNSS operations.