Measurements and Results
R&S
®
FSVA3000/ R&S
®
FSV3000
147
User Manual 1178.8520.02 ─ 01
Figure 7-20: Approximating the channel filter by sweeping with a small resolution bandwidth
The following steps are performed:
1. The linear power of all the trace points within the channel is calculated.
P
i
= 10
(Li/10)
Where P
i
= power of the trace pixel i
L
i
= displayed level of trace point i
2. The powers of all trace points within the channel are summed up and the sum is
divided by the number of trace points in the channel.
3. The result is multiplied by the quotient of the selected channel bandwidth and the
noise bandwidth of the resolution filter (RBW).
Since the power calculation is performed by integrating the trace within the channel
bandwidth, this method is called the IBW method (
I
ntegration
B
and
w
idth method).
Fast ACLR
The integrated bandwidth method (IBW) calculates channel power and ACLR from the
trace data obtained during a continuous sweep over the selected span. Most parts of
this sweep are not part of the channel itself or the defined adjacent channels. There-
fore, most of the samples taken during the sweep time cannot be used for channel
power or ACLR calculation.
To decrease the measurement times, the R&S
FSV/A offers a "Fast ACLR" mode. In
Fast ACLR mode, the power of the frequency range between the channels of interest
is not measured, because it is not required for channel power or ACLR calculation. The
measurement time per channel is set with the sweep time. It is equal to the selected
measurement time divided by the selected number of channels.
In the "Fast ACLR" mode, the R&S
FSV/A measures the power of each channel in the
time domain, with the defined channel bandwidth, at the center frequency of the chan-
nel in question. The digital implementation of the resolution bandwidths makes it possi-
ble to select filter characteristics that are precisely tailored to the signal. For
CDMA2000, for example, the power in the useful channel is measured with a band-
width of 1.23
MHz. The power of the adjacent channels is measured with a bandwidth
of 30
kHz. Therefore the R&S
FSV/A changes from one channel to the other and
measures the power at a bandwidth of 1.23
MHz or 30
kHz using the RMS detector.
Channel Power and Adjacent-Channel Power (ACLR) Measurement
