3
rd
Generation Compact RDMS
TM
Telemetry Receiver
84
Quasonix, Inc.
E R Time Bits Errors Delta Err* Error Rate* Seconds Eb/N0 L
! * 00:00:02.600 2.5933e+07 1.2836e+07 1.2836e+07* 4.950e-01 2 -45.15
! ! 00:00:03.100 3.0919e+07 1.5516e+07 2.6804e+06* 5.018e-01 3 -43.43
! ! 00:00:03.600 3.5904e+07 1.8197e+07 2.6813e+06* 5.068e-01 3 -44.11
! ! 00:00:04.100 4.0889e+07 2.0737e+07 2.5398e+06* 5.072e-01 4 -44.64
! ! 00:00:04.600 4.5875e+07 2.3443e+07 2.7062e+06* 5.110e-01 4 -31.84
10.1 Test Noise Commands
Digitally generated Additive White Gaussian Noise (AWGN) can be injected in the demodulator for test purposes.
This noise can exhaust most or all of the demodulator's error-free signal processing margin so that small
imperfections in the received signal will be visible as an increase in the bit error rate.
The noise level is calibrated relative to an extremely accurate measurement of the input signal level. This
measurement will be most accurate when the received signal has a high signal-to-noise ratio. Therefore, input signal
levels above -70 dBm are generally recommended. Due to the available dynamic range of the demodulator signal
processing path and the faithful representation of the AWGN, noise samples may be clipped, especially at or below
0 dB Eb/N0.
Note that the noise is injected following downconversion to baseband but before demodulation. Therefore, the noise
will affect demodulator output signals, including video outputs and the front panel display (eye diagram or
constellation), but it will not change measurements of the input signal (signal strength and signal quality).
The AWGN command, described in Table 10, displays and controls Additive White Gaussian Noise settings.
Table 10: Test Noise Commands
Mnemonic
Name
Description
AWGN ?
Test Noise Help
Provides help for using the test noise commands
AWGN
Test Noise Status
Report test noise status of current tracking channel
Example:
AWGN
AWGN disabled
AWGN power 50.00 dB E
b
/N
0
AWGN <e>
Enable/Disable Test
Noise
Turns the test noise output Enabled or Disabled
AWGN <e>
<e> - Sets AWGN enable to <e>
If 'e' is 0, test noise is Off/Disabled
If 'e' is 1, test noise is On/Enabled
Example:
AWGN 1
AWGN enabled