Keysight Technologies N5244/5B Service Manual page 209

Theory of Operations
Synthesized Source Group Operation
Table 5-9 LFE Bands (2 of 2) – (S/N Prefix
Band A15 DDS
LO
Synthesizer
a
(OCXO)
2 1.0000 to
1.95313
1.95313 to
3.90000
3.90000 to
7.81000
7.81000 to
9.9000
3 9.9000 to
10.01000
4 10.01000 to
19.99000
5 1.99000 to
31.25000
31.5000 to
53.0000
6 53.0000 to
62.50000
62.50000 to
1000.0000
a. A15 Source synthesizer VCO column only applies to version 6 synthesizers in instruments
with a s/n prefix <6021.
Understanding LFE vs. Legacy PNA Environment
To understand several parts of the LFE board behavior, we must consider the
non-LFE behavior of the PNA (i.e., what is already in place on different boards
that did not change).
On the synthesizer board, there is a LFE output coming almost directly from
the direct digital synthesis (DDS). There is a 250 MHz Low Pass Filter. The
low frequency extension uses this output to100 MHz.
A C-R High Pass Filter limits the lowest frequency.
With LFE mode, we use dedicated mixers, which are the LFE board. These
mixers downconvert the RF signals in LFE mode and create dedicated IF
signals. These IF signals are then sent to the A20 IF MUX board.
Keysight N5244B/45B Service Guide
IF Mode DIV / N
Thru 4
4
4
4
IF2 4
Thru 4
IF1 4
4
IF2 4
4
6021 Only)
≥
Synth RF Synth RF
Path Output
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
DDS_CLK LFE
5-41