Signal Control and Signal Characteristics
R&S
®
SMW-K144
142User Manual 1178.8013.02 ─ 06
"Constant PSD"
The power level set with the parameter "Status Bar > Level" is the
power of a fully allocated, fictitious signal with a specific band-
width (Reference System Bandwidth). The power spectral density
(PSD) of this fictitious signal is equal to the PSD of the current signal.
In this mode, you configure a specific power spectral density per
resource element rather than the RMS of the complete signal. The
absolute power of a particular allocation is then calculated by multi-
plying the configured PSD with the bandwidth of the allocation.
Thus, for a given "Reference System Bandwidth", the PSD and the
signal power for a particular bandwidth (SignalPower
BW
) are calcula-
ted as follows:
●
PSD = "Status Bar > Level" / "Reference System Bandwidth"
●
SignalPower
BW
= PSD*BW, where BW is the channel bandwidth.
Example:
Figure 6-4: Signal power level for Power Mode = Constant PSD
Level = "Status Bar > Level"
For "Reference System Bandwidth" = 100 MHz, the signal power of a
signal with 100 MHz bandwidth (BW = 100 MHz) is:
SignalPower
100 MHz
= ("Status Bar > Level" / 100 MHz)*100 MHz =
"Status Bar > Level"
The signal power of a signal with 50 MHz bandwidth (BW = 50 MHz)
is then:
SignalPower
50 MHz
= ("Status Bar > Level" / 100 MHz)*50 MHz = "Sta-
tus Bar > Level"/2 or
SignalPower
50 MHz
= "Status Bar > Level" - 3 dB
If "Status Bar > Level" = -10 dBm, the RMS power measured with a
power sensor in both cases is:
●
RMS
1
= -13 dBm
●
RMS
2
= -16 dBm
This mode is useful if you need to configure an absolute SNR. To
achieve an absolute SNR, set the "AWGN > System Bandwidth"
value to be equal to the "5G New Radio > Output/Power > Power >
Reference System Bandwidth".
Adjusting the Signal Power
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