Wavetek 3000 Instruction Manual page 39

4194
0
1718
/b98
/S93
AN.
/498
/398
1298
1198
MNz
MNz
MHz
/467
1449
270-
250--
210
170-
130
-90--
SO
280 -
2401
2004
160
/20
90 ~ I
40
O
O
3 .15 .1 Phase Detector
?Oo
/70
/Zo
The frequency offset circuit converts
the frequency of the VCO to a lower fre-
quency which retains the frequency error
information for use by the phase detec-
tor . In addition to the frequency off-
set circuit and the phase detector, sev-
eral auxillary circuits are included .
The phase detector compares the"offset"
VCO frequency to the reference frequency
from the M31 . (Refer to the description
of the M31 for a more detailed descrip-
tion of this 10 .000 - 9 .001 MHz refer-
ence .)
The phase detector output voltage goes
positive or negative to ultimately drive
the wide oscillator higher or lower in
SO
/o
0
40
70
g12
Figure 3-21 . M34 - Signal Frequencies
THFnRY OF OPERATION
1212
BO 110 /60 ; 140
190 BZO 3(0
/00
200
300
OUTPUT F-R10Ue/VC) , MNz
/so
.200
-~t~{-.~-_ -ma y
440 4,510
1
.00
400 500
3 .15 .2 Frequency Offset Circuit
280
The VCO error information must be con-
verted to a frequency useable by the
phase detector .
This conversion is made
by mixer #1, a 270 MHz low pass filter,
mixer #2
and a 10 MHz low pass filter .
Refer to
Figures 3-20, 3-21 and 3-22
for descriptions of signals .
Mixer 41 heterodynes the VCO frequency
with the "MHz steps" reference
fre-
quency (1448 + R) MHz .
The difference
frequency,
11448 + R - VCOJ,
is below
270 MHz . This signal is sent to mixer
42 where it is heterodyned with the 40
MHz comb . For any output frequency
graph
D in Figure 3-21
shows only
the comb
frequency which
will yield
the desired
output ( below
20
?liz)
3-21
frequency until both inputs to the phase
of
m;xPr # 2 .
Tf the loop is locked,
detector are the same frequency . The
mixer ,# 2
will
produce a 10 MHz
integrator serves as a low pass filter
difference as Ghown
in Figure 3-21
for the phase detector . (assuming the "kHz" switches are set for