Overall Theory Of Operation; In Cw/Manual Mode; In Swept Modes - HP 8340B Manual

20-30
Loops
Overall Theory of Operation
The 20-30 loops provide the
YIG oscillator
loop with
a
synthesized reference signal.
The
YO feedback
circuitry phase
locks the YO to the
20-30
loops output signal as explained below:
NOTE: The phase lock loops PLL2, PLL3, and PLL1 are usually
mentioned
out of numeric order (e.g.
instead of PLL1, PLL2, and PLL3 order). Instead, they are mentioned
in
functional order. PLL2
is the
first phase
lock loop, then PLL3, followed by PLL1.
IN CW/MANUAL MODE
The 20-30 loops directly phase lock the YO. PLL2, PLL3, and PLL1
operate together to produce
high
resolution tuning of the YO.
IN
SWEPT MODES
The 20-30
loops are used in three different ways, depending on the frequency range over which the
YIG oscillator
is
swept.
YO Sweep Width
is
Between 100 Hz and 5
MHz
The 20-30 loop
is
swept
in
this
mode, and the output of the
20-30
loops sweeps the YIG oscillator.
The
other
tuning inputs to the YO loop are
held constant.
YO
Sweep
Width
is >5 MHz
The 20-30
loops provide phase-lock reference to
the
YO only at the beginning of the sweep When
sweep
begins, the
YO phase-lock
loop
is opened, and the
YO
Is swept by
analog
means.
Table
C-l. 20-30
Loop Operation vs
YO
Sweep
Width
YO Sweep
Width
100 Hz
to
5
kHz
and
CW Mode
>5 kHz to
100kHz
>
100 kHz to
5
MHz
Loops Used
PLL1
X
X
-
PLL2
X
X
X
PLL3
X
X
-
PLL2VCO
Divided
By:
500
25
5
PLL1
Divide
By 10
ON
ON
OFF
Total
Divide
Number
5000
250
5
20-30
Output
Resolution
1
Hz
20 Hz
1 kHz
20-30
Loops
Overall Theory of Operation
HP 8340B/41B