Rohde & Schwarz SMBV100A, Руководство по эксплуатации

Страница: 327 / 911

Instrument Function
R&S
®
SMBV100A
312 Operating Manual 1176.8016.02 ─ 17
"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 596
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 598
Bit Rate - AWGN
(Additive Noise)
Sets or indicates the bit rate used for converting C/N or S/N to E
b
/N
0
.
With "Custom Digital Mod" signals, the bit rate used is indicated here. It is defined by
the choice of the standard in the "Custom Digital Mod" menu.
With "Digital Standard" signals, the bit rate used for converting C/N or S/N to E
b
/N
0
is
set here.
When generating a "Digital Standard", it is thus possible to select which bit rate is to be
used for calculating the ratio of bit energy to noise power density, e.g. the bit rate
before or after channel coding.
Remote command:
[:SOURce<hw>]:AWGN:BRATe
on page 592
Carrier/Noise Ratio / Signal/Noise Ratio
(Additive Noise and CW Interferer only)
Impairment of Digital I/Q Signal and Noise Generator - AWGN/IMP Block