R&S SMJ100A, Руководство по эксплуатации

Страница: 313 / 874

Instrument Function
R&S
®
SMJ100A
297 Operating Manual 1403.7458.32 ─ 14
Remote command:
[:SOURce<hw>]:AWGN:FREQuency:RESult?
on page 575
Noise Power Configuration And Output Results
The interfering signal is configured in the "Noise/Interferer Power Configuration and
Output Results" section.
Set Power via - AWGN
(Additive Noise only)
Selects the mode for setting the noise power.
"C/N ""S/N" The noise power is set on the basis of the value entered for the car-
rier/noise or signal/noise ratio.
Whether a selection of C/N or S/N is enabled, depends on the
selected "Display Mode".
With digital modulation, the associated E
b
/N
0
value is determined and
displayed.
"E
b
/N
0
" The noise power is set on the basis of the value entered for the ratio
of bit energy to noise power density.
The associated C/N or S/N value is displayed. The correlation
between the two values is as follows:
C/N or S/N = (E
b
/N
0
)*(f
bit
/B
sys
), where
f
bit
is the Bit rate (Symbol rate x Modulation value)
B
sys
is the System bandwidth
With "Custom Dig Mod" signals, the bit rate used for calculation is
defined by the selected standard in the "Custom Digital Mod" dialog.
With "Digital Standard" signals, the bit rate to be used for calculating
the E
b
/N
0
can be entered at "Bit Rate".
Some test cases with the 3GPP base station tests (TS 25.141) spec-
ify, for example, E/N settings that apply to channel-coded data or
block segments.
Remote command:
[:SOURce<hw>]:AWGN:POWer:MODE
on page 577
Reference Mode - AWGN
(Additive Noise and CW Interferer, Display Mode set to RF)
Select reference mode if the C/N or Eb/N0 ratio is changed.
"Carrier" If the C/N value or E
b
/N
0
value changes, the carrier power is kept
constant and the noise power is adjusted. This is the standard proce-
dure for measuring the bit error rate versus the noise power.
"Noise" If the C/N value or E
b
/N
0
value changes, the noise power is kept con-
stant and the carrier power is adjusted.
Some test cases of 3GPP Base Station Tests (TS 25.141) specify, for
example, that the noise power be permanently set as a function of the
base station power class, whereas the carrier power is variable.
Remote command:
[:SOURce<hw>]:AWGN:POWer:RMODe
on page 578
Impairment of Digital I/Q Signal and Noise Generator - AWGN/IMP Block