Rohde & Schwarz SMBV100B - Page 253

Configuring the Internal Baseband Source
R&S
®
SMBV100B
251User Manual 1178.4460.02 ─ 03
Limitations
The complex I/Q bandwidth of the shifted useful signal must not exceed the total avail-
able baseband bandwidth (see data sheet). The setting range of the frequency offset is
then calculated as follows:
-(TotalBasebandBandwidth/2) + f
use
/2
≤ f
offset
≤ (TotalBasebandBandwidth/2) - f
use
/2 ,
where
f
use
is the complex useful bandwidth of the I/Q signal before the offset
f
offset
is the frequency offset
The Figure 3-29 illustrates the setting range of the frequency offset.
Figure 3-29: Setting range of frequency offset
Example: Calculating the maximum frequency offset
This example uses the following signal:
●
"Standard = 3GPP FDD"
●
"Chip Rate = 3.84 Mcps"
●
"Filter Type = Root Cosine"
●
"Roll Off Factor = 0.22"
The complex useful bandwidth of filtered signal is calculated as follows (see "Impact of
the Filter Parameters" on page 106):
●
f
use
= (1 + "Roll Off Factor") * "Symbol Rate"
●
f
use
= (1+ 0.22) * 3.84 MHz = 4.6848 MHz
For an instrument with a total available I/Q bandwidth of 160 MHz, the valid range of
values for the frequency offset is then:
●
-160 MHz/2 + 4.6848 MHz/2 ≤ f
offset
≤ 160 MHz/2 - 4.6848 MHz/2 or
●
-77.6576 MHz ≤ f
offset
≤ 77.6576 MHz
Shifting and Boosting the Baseband Signal