Rack-Mount RDMS
TM
Telemetry Receiver
94
Quasonix, Inc.
noise. When Mod Scaling is in Tracking mode, the modulation index estimate becomes poorer as the SNR decreases
(that is, as the received signal gets weak). This in turn negatively impacts demodulation performance, making bit
errors more likely than they would be if the modulation index were known a priori.
•
Eb/N0 is the ratio of signal energy per bit (Eb) to noise energy spectral density (N0), which is sometimes
referred to as “SNR per bit.”
4.2.3.1.2.3 AGC Settings Window
The AGC (Automatic Gain Control) Settings window includes the following parameters:
•
AGC Gain (00)
•
AGC Time Constant (in ms)
•
AGC Zero Hold
•
AGC Freeze On
•
AGC Polarity Inverted
Figure 166: AGC Settings Window
AGC Zero is used to set a baseline for background radio noise levels. A typical application of the AGC Zero
function is explained in the following example.
1.
Connect the receiver to its normal RF signal source, such as antenna, LNA, cabling, and splitters.
2.
Orient the receiving antenna in a direction that is expected to yield the lowest signal level that the receiver
is likely to encounter.
3.
Activate AGC Zero under this condition by clicking on the AGC Zero screen button, shown in Figure 166.
The AGC output voltage is set to zero volts DC at a time when the receiver input is at its minimum value.
This process ensures that the AGC output voltage will not cross through zero volts DC under normal
operation.
4.2.3.1.2.4 AM Settings Window
The AM (Amplitude Modulation) Settings window includes the following parameters:
•
AM Bandwidth (KHz)
•
AM Time Delay (us)
•
AM Scale (0.05-2.5)
•
AM Polarity Inverted (+/-)
•
AGC Compensate