Noise Figure Measurement - Safran CORTEX RTR NeXt Series User Manual

6.5

Noise Figure Measurement

A feature has been introduced which should be used when using an automatic NF measurer tool.
Different kind of Diode can be used to generate noise with different ENR values from 5dB to 15dB.
NF measurement is done at maximum gain inside the receiver and when AGC is running in automatic
mode, the use of high ENR diode may generate some saturation in the RF chain and as a result give a
wrong NF measurement.
When performing automatic NF measurement, the diode is continuously driven ON and OFF like
shown on the following screenshot:
To have a good NF measurement, it is important to be able to set the receiver at the appropriate gain
when the diode is ON but generally it is not possible turn the diode ON and Freeze the receiver gain to
perform a proper measurement.
If AGC is in automatic mode, to have a stable measurement, the time constant should be set to
1000ms but due to Diode ON/OFF cycling, a mean gain is computed and some saturation may occur.
Hence, a NF Meas. Mode has been added and is accessible from the AGC configuration element in
the operation page.
When activating this mode the following sequence is done:

AGC time constant is internally set to 1000ms

Gain value is averaged over 2 seconds

AGC mode is internally changed to manual

The Gain value minus 5dB is applied to avoid any saturation
Hence, when using an automatic NF measurer:
1- Connect the measurer to the receiver
2- Turn the Diode Cycling ON
3- Select the NF. Meas mode on the receiver
4- Read the result on the NF measurer tool.
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Radio Telemetry Receiver
User's Manual
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Ref. D104004
Is.Rev 07
Previous Ref.: DTU000567
Date: 21/06/2021
Safran Data Systems
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Page 62