us 3875427
TRANSCRIPT
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8/15/2019 Us 3875427
1/6
United States
Patent 1 1 9 1
‘
1 1 1 1
3,875,427
R i l e y [ 4 5 ]
A p r .
1 ,
1 9 7 5
[ 5 4 1 SWEEP GENERATOR CIRCUIT FOR
AN 3 . 6 1 2 . 9 0 2 1 0 / 1 9 7 1 M o o s e 3 0 7 / 2 2 9
[ 2 2 ]
I 2 1 ]
[ 5 2 1
[ 5 1 1
I 5 8 ]
[ 5 6 }
3 , 4 3 9 , l
8 7
3 . 5 2 l . 0 8 2
3 , 5 8 8 , 5 3 0
ELECTRONIC APPARATUS
WHICH
PRODUCES
A
SWEEP
SIGNAL
HAVING
A
SWEEP
RATE
PROGRAMMED BY
THE
SETTINGS
OF
A
SELECTED PLURALITY
OF CONTROLS OF THE
ELECTRONIC
APPARATUS
R u s s e l l
B . R i l e y , P o r t o l a
V a l l e y ,
C a l i f .
H e w l e t t - P a c k a r d
Company, P a l o
A l t o ,
C a l i f .
F i l e d : D e c . 1 0 ,
I 9 7 3
A p p l .
N o . : 4 2 3 , 3 4 1
I n v e n t o r :
A s s i g n e e :
US. Cl . . . . . . . . . . . . . . . . . 307/228, 307/229, 307/230,
3 2 8 / 1 8 1, 3 2 8 / l 8 5 , 3 2 8 / 1 4 5
I n t .
C l . . . . . . . . . . . . . . . . . . . . . . . . .
. .
l - l 0 3 k 4/08,
606g
7/24
F i e l d
o f Search . . . . . . . . . . . . . . . . .
. .
307/228,
229, 230;
3 2 8 / l 8 l - I 8 5 , I 4 4 . I 4 5
R e f e r e n c e s C i t e d
UNITED STATES
PATENTS
4/l969 Strauss
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . 307/229
7 l970 Wolk
. . . . . . . . . . . . . . . . . . . . . . . . ..
307 228
6/l97l Langan . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 307/229
OTHER
PUBLICATIONS
“ I n v e r s e F u n c t i o n
D-+
A o n v e r t e r , “ b y Baumann
i n
IBM
T e c h . D i s c l . B u l l . , V o l . l 2 , N o . 1 , J u n e 1 9 6 9 ,
p a g e 8 2 .
P r i m a r y E x a m i n e r - S t a n l e y D . M i l l e r ,
J r .
A t t o r n e y , A g e n t , o r F r m - P a t r i c k J . B a r r e t t
[ 5 7 ] ABSTRACT
S e v e r a l c u r r e n t
s o u r c e s
a r e p r o v i d e d
which produce
c u r r e n t s p r o p o r t i o n a l t o t h e l o g a r i t h m s o f I F band
w i d t h , v i d e o
b a n d w i d t h , and s c a n
w i d t h o f a
spectrum
a n a l y z e r . These
c u r r e n t s a r e
summed b y a n o p e r a
t i o n a l
a m p l i ? e r
t o p r o d u c e a v o l t a g e p r o p o r t i o n a l t o
t h e
a l g e b r a i c sum
o f t h e s e c u r r e n t s . T h i s v o l t a g e i s a p
p l i e d t o an
e x p o n e n t i a t i n g
t r a n s i s t o r t o produce a c o l —
l e c t o r c u r r e n t which c h a r g e s a c a p a c i t o r whose v o l t
a g e
r i s e i s
l i n e a r
w i t h t i m e . The v o l t a g e o n t h e c a p a c i
t o r
may be u s e d a s a sweep s i g n a l
i n
a spectrum
a n a l y —
z e r .
O t h e r c i r c u i t s
g e n e r a t e
c o m p e n s a t i n g v o l t a g e s
which
a r e
added t o
t h e a f o r e m e n t i o n e d v o l t a g e ap
p l i e d
t o
t h e
e x p o n e n t i a t i n g t r a n s i t o r
t o
r e d u c e
v a r i a
t i o n s i n c o l l e c t o r c u r r e n t
d u e
t o t e m p e r a t u r e c h a n g e s
i n t h i s
t r a n s i t o r .
8
C l a i m s ,
2 D r a w i n g
F i g u r e s
532
a
22
- ° 1
0
r 2 3
2 1
UTLRATM
C I R C U I T
: =~2
REDIT
C I R C U I T
ach
1 i
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3 , 8 7 5 , 4 2 7
I
SWEEP GENERATOR
CIRCUIT FOR
AN
ELECTRONIC APPARATUS WHICH
PRODUCES
A
SWEEP
SIGNAL
HAVING
A
SWEEP
RATE
PROGRAMMED
BY THE SETTINGS OF A
SELECTED PLURALITY OF CONTROLS OF THE
ELECTRONIC APPARATUS
BACKGROUND
OF THE INVENTION
P r i o r
a r t
sweep
g e n e r a t o r s
f o r s p e c t r u m
a n a l y z e r s
u s u a l l y p r o v i d e a sweep r a t e which i s
c o n t r o l l e d
by a
s i n g l e s w i t c h w i t h
which t h e
u s e r m a n u a l l y s e l e c t s
t h e
d e s i r e d
sweep r a t e .
I d e a l l y ,
t h e
u s e r
w i l l
always want
t o
s e l e c t a sweep
r a t e t h a t i s f a s t
enough
f o r
t h e s i g n a l
t r a c e o n t h e
cathode
r a y
tube
d i s p l a y
t o appear ?icker
f r e e .
Such a s e l e c t i o n
i s
u s u a l l y
p o s s i b l e w i t h wide 1 F
bandwidths and
a
nar r o w
scan o r
sweep width;
how
ever, m ost
users
also
desire to
use n a rr o w bandwidths
and wid e sweep w i d t h s t o o b t a i n
g r e a t e r
r e s o l u t i o n
over
a
l a r g e
p o r t i o n o f
t h e
s p e c t r u m .
Under
h e s e
con
d i t i o n s , t h e
sweep
r a t e must be reduced t o
g i v e
t h e
I F
f i l t e r s s u f f i c i e n t t i m e
t o
r e s p o n d
t o
i n c o m i n g s i g n a l s . I f
t h e
s p e c t r u m
a n a l y z e r i s
s w e p t
t o o f a s t , t h e i n f o r m a t i o n
d i s p l a y e d
on
t h e
CRT
i l l be d i s t o r t e d .
I n
many p r i o r
a r t
s p e c t r u m a n a l y z e r s , t h e o p e r a t o r
m u s t s i m p l y
b e
a l e r t t o t h e
p o s s i b i l i t y t h a t
d e c r e a s i n g
I F bandwidth o r
i n c r e a s i n g sweep
w i d t h may r e s u l t i n
an u n c a l i b r a t e d and
d i s t o r t e d
d i s p l a y . T h u s , t h e opera
t o r
w i l l
watch t h e
d i s p l a y and change
t h e
sweep r a t e ,
or scan t i m e , when t h e d i s p l a y
s t a r t s
t o d i s t o r t . Some
s p e c t r u m a n a l y z e r s ,
f o r e x a m p l e t h e
H e w l e t t - P a c k a r d
m o d e l
8 5 5 3 / 8 5 5 2 ,
p r o v i d e a w a r n i n g l i g h t t o i n d i c a t e
t h a t t h e
sweep r a t e i s t o o
g r e a t
f o r t h e bandwidth and
sweep i d t h
t h a t h a v e
been s e l e c t e d .
T h i s w a r n i n g l i g h t
i s connected
t o
a s e n s i n g c i r c u i t t h a t d e t e c t s t h e p o s i
t i o n s
o f
t h e v a r i o u s s w i t c h e s
u s e d
t o
s e l e c t
t h e sweep
w i d t h , sweep
r a t e
and
b a n d w i d t h . The
s w i t c h
p o s i t i o n s
a r e d e t e c t e d
b y connecting each s w i t c h t o a v a r i a b l e
c u r r e n t source
whose
output i s
dependent o n t h e
s e t
t i n g o f
t h e
s w i t c h .
S i n c e t h e p r o p e r
r e l a t i o n s h i p
o f
bandwidth, sweep width
and sweep r a t e can
be ex
p r e s s e d a s a n a l g e b r a i c
f o r m u l a
d i s c u s s e d
b e l o w )
t h e
c u r r e n t s r e p r e s e n t i n g t h e s e q u a n t i t i e s a r e a l g e b r a i c a l l y
combined i n
t h e
s e n s i n g
c i r c u i t r y
t o i n d i c a t e whether
t h e sw i t c h
s e t t i n g s a r e p r o p e r .
Both o f t h e f o r e g o i n g
methods
a v e
c e r t a i n i n h e r e i n t
d i s a d v a n t a g e s .
F o r
t h e
f i r s t
method
t o
b e
s u c c e s s f u l ,
t h e
spectrum
a n a l y z e r u s e r
must
be
aware
o f
t h e e f f e c t
d e s c r i b e d and he must
c o n s t a n t l y
be a l e r t t o t h e e f f e c t
o f
s w i t c h s e t t i n g s o n h e c a l i b r a t i o n o f t h e d i s p l a y .
T h i s
i s f r e q u e n t l y
d i f f i c u l t ,
e s p e c i a l l y
w h e n
t h e s i g n a l b e i n g
d e t e c t e d
i s i n t e r m i t t e n t o r t h e u s e r i s s t i l l
l o o k i n g
f o r a
s i g n a l . The
second method s
more d e s i r a b l e , b u t
s t i l l
r e q u i r e s
v i g i l a n c e
o n t h e p a r t
of
h e u s e r ,
a s
w e l l a s an
a w a r e n e s s o f
t h e
s i g n i ? c a n c e o f
t h e w a r n i n g l i g h t .
SUMMARY OF THE INVENTION
A c c o r d i n g t o
t h e
p r e f e r r e d embodiment o f t h e p r e s
e n t i n v e n t i o n ,
t h e
sweep r a t e
o f
a
spectrum
a n a l y z e r
i s
a u t o m a t i c a l l y c o n t r o l l ed b y a s i m p l e c o n t r o l
c i r c u i t
which i s
dependent o n t h e
I F
bandwidth (BWW), t h e
v i d e o bandwidth ( B W , , , , , ) , and
t h e
s c a n w i d t h (SW) o f
t h e a n a l y z e r .
The
r e l a t i o n s h i p
o f
t h e s e q u a n t i t i e s
t o
sweep
a t e
(SR)
o r
sweep
t i m e
(ST) s
g i v e n b y
t h e
f o l
l o w i n g
e q u a t i o n :
1 0
1 5
2
BWIF
X
WM
LS
SW
I I
5
ST
which
may b e e x p r e s s e d i n l o g a r i t h m i c
form
a s :
l o g
BWIF+
o g
B W , ‘ , , , —
l o g SW+ K o l / S T ) .
A BWW o n t r o l
s e l e c t s
an I F bandwidth and a l s o regu
l a t e s
a
current
source
w h i ch
pro vi des a current
pro p or
t i o n a l t o l o g BWW.
n
t h e
same
manner,
WM o n t r o l
s e l e c t s
a video
bandwidth
and
a l s o
r e g u l a t e s a current
s o u r c e
which
p r o v i d e s a c u r r e n t p r o p o r t i o n a l
t o
l o g
B W , , , , , , and
s i m i l a r l y , a
SW
o n t r o l
s e l e c t s a
scan wi dth
and a t the same time regulates
a
current
source t o p r o
v i d e a c u r r e n t which
s
p r o p o r t i o n a l t o
—log
SW. A l l o f
t h e s e c u r r e n t s a r e coupled
t o
t h e
spectrum
a n a l y z e r
s w e e p g e n e r a t o r
c i r c u i t r y .
The three
sources producing t h e s e
cur rents are
c o n
n e c t e d
t o a
summing
o i n t which s ,
i n
t u r n ,
connected
t o t h e
i n p u t
o f
a
summing m p l i ? e r .
The
o u t p u t v o l t a g e
o f t h e summing m p l i ? e r i s
a p p l i e d
t o t h e e m i t t e r - b a s e
2 0
j u n c t i o n
o f an e x p o n e n t i a t i n g t r a n s i s t o r
t o
produce a
25
30
35
40
45
50
55
60
65
c o l l e c t o r c u r r e n t which i s p r o p o r t i o n a l
t o
t h e a n t i
l o g a r i t h m
o f
t h e
a p p l i e d
v o l t a g e ,
a c c o r d i n g
t o t h e w e l l
k n o w n d i o d e
l a w .
The c o l l e c t o r c u r r e n t
produced b y
t h e e x p o n e n t i a t i n g t r a n s i s t o r c h a r g e s
a c a p a c i t o r
t o
produce a v o l t a g e ramp which r i s e s a s a l i n e a r f u n c t i o n
o f t i m e . A e s e t c i r c u i t connected o
t h e c a p a c i t o r
s t o p s
t h e v o l t a g e
r i s e
a t
a
predetermined
v a l u e and r e s e t s
i t
t o
i t s
i n i t i a l
v a l u e
f o r t h e
beginning
of n e w
sweep.
The
o u t p u t
o f
t h i s
a m p l i ? e r
i s u s e d t o c o n t r o l t h e sweep
o f
a o c a l o s c i l l a t o r
and
h e
h o r i z o n t a l d e f l ec t i o n of a CRT
i n
a spectrum a n a l y z e r .
F u r t h e r ,
i n a c c o r d a n c e w i t h
t h e
p r e f e r r e d embodi
ment o f t h e p r e s e n t
i n v e n t i o n , c i r c u i t s may a l s o
b e
i n
c l u d e d
t o
e f f e c t i v e l y
p r e v e n t
t e m p e r a t u r e
v a r i a t i o n s
f r o m
c h a n g i n g
t h e c o l l e c t o r
c u r r e n t p r o d u c e d b y t h e
e x p o n e n t i a t i n g t r a n s i s t o r . T h i s s t a b i l i z i n g e f f e c t may b e
a t t a i n e d
b y a d d i n g c o m p e n s a t i n g v o l t a g e s t o t h e
v o l t
a g e a p p l i e d t o
t h e
e m i t t e r - b a s e j u n c t i o n
o f
t h i s t r a n s i s
t o r .
BRIEF
DESCRIPTION
OF THE DRAWINGS
F I G .
I
shows
a
s c h e m a t i c
d i a g r a m o f t h e p r e f e r r e d
embodiment.
F I G .
2
shows a s c h e m a t i c diagram o f t h e
p r e f e r r e d
emb odi ment w i t h an
a d d i t i o n a l
temperature
c o m pe n
s a t i n g c i r c u i t .
DESCRIPTION OF THE
PREFERRED
EMBODIMENT
FIG.
1
shows c u r r e n t s o u r c e s l 0 , l2 and
17
which
s u p p l y c u r r e n t s p r o p o r t i o n a l t o t h e l o g a r i t h m o f some
p a r a m e t e r s o r
c o n t r o l
s e t t i n g s o f a spectrum a n a l y z e r .
For
n s t a n c e , t h e c u r r e n t
produced
by
s o u r c e
1 0 i s pro
p o r t i o n a l t o
l o g
(BWm).
t h e
c u r r e n t
p r o d u c e d b y
s o u r c e 12 s
p r o p o r t i o n a l
t o — - l o g
(SW),
and h e
c u r r e n t
p r o d u c e d b y
s ou r c e 1 7
i s
p r o p o r t i o n a l
t o
l o g (BWM).
These c u r r e n t s a r e summed a t an i n v e r t i n g i n p u t 16 o f
a n o p e r a t i o n a l a m p l i ? e r l 5 , a n d
a
v o l t a g e p r o p o r t i o n a l
t o
the sum
of
t h e s e
currents
s
developed a c r o s s nega
t i v e
feedback r e s i s t o r 7 .
The
o u t p u t
v o l t a g e o f o p e r a t i o n a l a m p l i ? e r
1 5 i s
a p
p l i e d
t o t h e
e m i t t e r - b a s e j u n c t i o n o f a t r a n s i s t o r
2 0 ,
and
t h e
base
of t h a t t r a n s i s t o r i s
connected
t o
a
constant
v o l t a g e V , . T h u s , t h e c o l l e c t o r c u r r e n t ( 1 , ) o f t r a n s i s t o r
20 s p r o p o r t i o n a l
t o t h e a n t i - l o g a r i t h m
o f i t s
e m i t t e r
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3
b a s e v o l t a g e
a c c o r d i n g t o
t h e
w e l l - k n o w n
e x p o n e n t i a l
s e m i c o n d u c t o r l a w : I”: K2 K a l a u ,
where
K: and K 3 a r e d e v i c e p a r a m e t e r s t h a t depend
on
t e m p e r a t u r e .
T h i s
p r o c e s s o f summing l o g a r i t h m s a n d
f o r m i n g t h e
a n t i - l o g a r i t h m s
means
t h a t t h e c o l l e c t o r
c u r r e n t o f t r a n s i s t o r
2 0 ,
i t , i s p r o p o r t i o n a l t o :
BWIE X BWM
L5 X SW
The c u r r e n t
I t i s used t o
c h a r g e a a p a c i t o r
24
which
i s connected t o
t r a n s i s t o r
20 by a f i e l d - e f f e c t t r a n s i s t o r
(PET)
2 2 .
The FET i s o l a t e s t r a n s i s t o r 20 from a n y
l o a d i n g e f f e c t s o f c a p a c i t o r 24
s i n c e
t h e v o l t a g e
b u i l d u p on t h e c a p a c i t o r c h a n g e s t h e
c o l l e c t o r e m i t t e r
v o l t a g e o n t h e t r a n s i s t o r which
i n
t u r n , a f f e c t s some
what
t h e
c u r r e n t o u t p u t
o f t h e
t r a n s i s t o r . The
FET
a s
a n e g l i g i b l e g a t e c u r r e n t ,
and
h e r e f o r e e s s e n t i a l l y
a l l o f
I E
r e a c h e s
c a p a c i t o r 2 4 .
T h i s
c a p a c i t o r ,
i n
t u r n ,
i s
con
n e c t e d
t o u t i l i z a t i o n
c i r c u i t s
23 by a b u f f e r a m p l i ? e r
2 1 .
The b u f f e r
a m p l i ? e r
h a s a s u f f i c i e n t l y h i g h i n p u t
impedance t h a t t h e c h a r g e on c a p a c i t o r 24
due
t o l a i s
n o t d r a i n e d
o f f by h e
u t i l i z a t i o n c i r c u i t s .
T y p i c a l l y ,
u t i
l i z a t i o n
c i r c u i t s
23 i l l
b e
h o r i z o n t a l
d e ? e c t i o n
a m p l i
?er
f o r
a
CRT and
a voltage-tuned l o c a l o s c i l l a t o r
i n
a
spectrum a n a l y z e r . With a
c o n s t a n t
c u r r e n t l c from
t r a n s i s t o r 2 0 , t h e
v o l t a g e
on c a p a c i t o r 24 i l l
i n c r e a s e
l i n e a r l y w i t h t i m e , and
i l l
t h u s
p r o v i d e
a l i n e a r sweep
s i g n a l t o t h e u t i l i z a t i o n c i r c u i t s .
A
e s e t c i r c u i t 30
s u c h
a s t h o s e c o m m o n l y u s e d i n spectrum a n a l y z e r s and o s
c i l l o s c o p e s i s u s e d t o l i m i t
t h e v o l t a g e
r i s e
on c a p a c i t o r
24
and r e s e t i t
t o
z e r o when a predetermin ed maximum
v a l u e
i s r e a c h e d .
As shown
i n
FIG.
2 , c u r r e n t
s o u r c e s
l 0 , l2
and
17
ma y
each comprise a
p l u r a l i t y
o f r e s i s t o r s t h a t a r e
s e
l e c t i v e l y
s w i t c h e d i n t o t h e
c i r c u i t
b e t w e e n i n p u t
1 6
a n d
g r o u n d .
The
v a l u e s
o f t h e r e s i s t o r s
a r e
chosen s o t h a t
a
l i n e a r change
i n
t h e v a l u e o f
a
parameter s e l e c t e d by
a
sweep
wid th or
bandwidth
s w i t c h w i l l
r e s u l t
i n l o g a
r i t h m i c change n c u r r e n t . Thus s
t h e
sweep
w i d t h ,
f o r
e x a m p l e , i s
i n c r e a s e d
by f a c t o r
o f
1 0 , t h e c u r r e n t p r o
p o r t i o n a l t o i t w i l l d e c r e a s e by on e u n i t o f c u r r e n t . I t
s h o u l d a l s o be noted h e r e t h a t both an I F
bandwidth
and a
video
bandwidth c o n t r o l a r e provided f o r . I n
some s p e c t r u m a n a l y z e r s a r e l a t i v e l y w i d e v i d e o band
w i d t h
i s
p r o v i d e d
c o m p a r e d w i t h
t h e I F b a n d w i d t h )
and o n l y
t h e [ F
b a n d w i d t h
i s
v a r i a b l e . I n s u c h a n
a n a l y
z e r t h e o p t i m a l sweep r a t e may
b e
determin ed b y t h e
f o l l o w i n g e q u a t i o n :
SR 2 . 2 sw
Thus t h e i n c r e m e n t s o f c u r r e n t r e p r e se n t i n g I F band
w i d t h i n s u c h an n a l y z e r would b e
t w i c e
t h e i n c r e m e n t
o f c u r r e n t u s e d f o r sweep w i d t h .
As shown n b o t h F I G S .
1
a n d
2 , o p e r a t i o n a l a m p l i
t i e r
1 5
a l s o h a s a n on - i n v e r t i n g i n p u t
1 9 . T h i s
i n p u t
i s
u s e d
t o
i n t r o d u c e a
v o l t a g e t h a t v a r i e s
w i t h tempera
t u r e t o compensate f o r t e m p e r a t u r e v a r i a t i o n s e x p e r i
e n c e d
b y
t r a n s i s t o r 2 0 . A
t e m p e r a t u r e c o m p e n s a t i n g
t r a n s i s t o r
26 i s
t h e r m a l l y c o u p l e d t o t r a n s i s t o r
20 b y
mounting them t o a g o o d thermal
conductor such
a s a
b l o c k o f aluminum o r c o p p e r . The
e m i t t e r
of
r a n s i s t o r
26 s connected t o a
v o l t a g e s o u r c e
V,
through
a
r e s i s
25
30
3 5
45
50
55
4
t o r
3 5 ,
a s i s
a
v a r i a b l e
v o l t a g e
d i v i d e r
3 3 .
V2
s t y p i c a l l y
s e v e r a l v o l t s h i g h e r t h a n V ‘ . The v a r i a b l e arm o f t h e
v o l t a g e
d i v i d e r i s c o n n e c t e d
t o n o n - i n v er t i n g i n p u t
1 9 .
As
t h e
t e m p e r a t u r e
o f
t r a n s i s t o r
20
i n c r e a s e s , t h e
temperature o f t r a n s i s t o r 26 w i l l a l s o i n c r e a s e , a s w i l l
t h e c u r r e n t t h r o u g h t h e s e t r a n s i s t o r s . With a
g r e a t e r
c u r r e n t ? o w i n g
t h r o u g h t r a n s i s t o r 2 6 , t h e
v o l t a g e
d r o p
a c r o s s r e s i s t o r 35
i l l
i n c r e a s e , d e c r e a s i n g t h e
v o l t a g e
on n o n - i n v e r t i n g
i n p u t 1 9 .
That
d e c r e a s e w i l l
r e s u l t
i n
a
l o w e r v o l t a g e o n h e e m i t t e r o f t r a n s i s t o r 2 0 , l o w e r i n g
the current
through
t h e
t r a n s i s t o r .
The v a r i a b l e arm o n
v o l t a g e d i v i d e r 33 can
be
a d j u s t e d t o
compensate
f o r
dc. v o l t a g e o f f s e t s between
i n p u t s
l 6 and 1 9 and d i f
f e r e n c e s
i n t h e
VBE o f
t r a n s i s t o r s 20 and
2 6 .
A hange
i n
t h e c u r r e n t ?owing t h r o u g h a t r a n s i s t o r
c a n c h a n g e
i t s t e m p e r a t u r e ,
a n d
t h e r e f o r e c h a n g e s i n
t h e c u r r e n t ?owing
h r o u g h
c o m p e n s a t i n g t r a n s i s t o r 2 6
c o u l d d e l e t e r i o u s l y e f f e c t
t h e
c o m p e n s a t i o n .
A
r a n s i s
t o r
27
i s p r o v i d e d
t o keep
t h e
c u r r e n t
t h r o u g h t r a n s i s
t o r
26
r e l a t i v e l y
c o n s t a n t
t o
m i n i m i z e t e m p e r a t u r e
c h a n g e s
d u e t o
c h a n g e s
i n c u r r e n t t h r o u g h t r a n s i s t o r
2 6 .
The
base of
r a n s i s t o r 27 i s connected
t o
a r e s i s t o r
31 i n s e r i e s w i t h t h e
c o l l e c t o r
of r a n s i s t o r 26 t o s e n s e
t h e
c u r r e n t t h r o u g h t h a t t r a n s i s t o r , and
t h e
c o l l e c t o r o f
t r a n s i s t o r
27 s connected
o
t h e
e m i t t e r o f
t r a n s i s t o r 26
t o p r o v i d e
t h e c u r r e n t
s t a b i l i z i n g f e e d b a c k
s i g n a l .
An
d d i t i o n a l
t e m p e r a t u r e c o m p e n s a t i o n c i r c u i t
may
a l s o be p r o v i d e d a s shown
i n
F I G .
2 .
As
p r e v i o u s l y
m e n t i o n e d , 1 c
i s t e m p e r a t u r e
d e p e n d e n t
s i n c e , i n t h e
e q u a t i o n
I , =
2
eKsVBE
K 3
i s
i n v e r s e l y p r o p o r t i o n a l t o
t e m p e r a t u r e .
Thus
t h e
c u r r e n t t h r o u g h t r a n s i s t o r 20
i l l
s t i l l
b e
t e m p e r a t u r e
dependent o
a
e r t a i n e x t e n t , even
f
t h e compensation
scheme shown n P 1 6 . 1 i s u s e d . T h i s
t e m p e r a t u r e
v a r i
a t i o n
c a n b e c o m p e n s a t e d f o r b y m a k i n g v o l t a g e V ,
v a r y w i t h t e m p e r a t u r e a s K ; v a r i e s . The v o l t a g e d r o p
across a forward-biased diode
made
o f
the same m ate
r i a l
a s
t r a n s i s t o r s 20 and 26 and
t h e r m a l l y
c o u p l e d
t o
them i l l v a r y i n t h e same way s V“. Such a forward
b i a s e d
d i o d e 43 s connected t o an i n v e r t i n g i n p u t 49
o f a n
o p e r a t i o n a l
a m p l i ? e r 42 h r o u g h a summing e s i s
t o r 4 4 .
The v o l t a g e a c r o s s
diode
43 s added t o a regu
l a t e d v o l t a g e from a power s u p p l y 2 9 ,
connected
t o a
n o n i n v e r t i n g
i n p u t 4 7 o f o p e r a t i o n a l
a m p l i ? e r
4 2 , t o
p r o v i d e a t e m p e r a t u r e d e p e n d e n t
v o l t a g e
V ‘ , a t
t e r m i
n a l
41
t h a t
v a r i e s
t h e
same
a s
V“, u t
i n
t h e
o p p o s i t e
d i r e c t i o n .
I
c l a i m :
1 . A sweep
g e n e r a t o r
c i r c u i t , a d a p t e d
t o
r e s p o n d t o
a p l u r a l i t y o f
i n p u t
q u a n t i t i e s , c o m p r i s i n g :
current
source means f o r producing c u r r e n t s propor
t i o n a l t o t h e l o g a r i t h m s o f e a c h o f t h e i n p u t q u a n t i
t i e s :
summation
means connected t o the current source
means
f o r
p r o d u c i n g a
v o l t a g e
p r o p o r t i o n a l t o
t h e
sum
f the currents
f r o m
the
current
source
means;
e x p o n e n t i a t i n g means
connected
t o t h e
summation
means f o r producing a c u r r e n t p r o p o r t i o n a l t o t h e
a n t i - l o g a r i t h m
o f t h e
v o l t a g e
p r o d u c e d b y t h e
sum
mation means;
and
c h a r g e s t o r a g e means c o n n e c t e d
t o
t h e e x p o n e n t i a t
i n g
means
f o r producing a
sweep
v o l t a g e i n r e
s p o n s e t o t h e
c u r r e n t
produced b y t h e e x p o n e n t i a t
i n g
means.
2 . A sweep
g e n e r a t o r a s
i n c l a i m 1 w h e r e i n :
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6/6
3 , 8 7 5 , 4 2 7
5
t h e summation
means c o m p r i s e s a
summing
a m p l i
? e r ;
t h e
c h a r g e
s t o r a g e
means
c o m p r i s e s
a c a p a c i t o r ; and
t h e e x p o n e n t i a t i n g means
o m p r i s e s a
v o l t a g e s o u r c e
and a ? r s t t r a n s i s t o r having an
e m i t t e r
connected
t o t h e
summing
a m p l i ? e r ,
a
b a s e connected t o t h e
v o l t a g e
s o u r c e ,
and a c o l l e c t o r connected t o
t h e
c a p a c i t o r .
3 . A
sweep
g e n e r a t o r
a s
i n c l a i m 2 i n c l u d i n g a ? r s t
t e m p e r a t u r e c o m p e n s a t i n g c i r c u i t c o n n e c t e d t o
t h e
? r s t t r a n s i s t o r t o compensate f o r
t h e r m a l l y
i n d u c e d
c h a n g e s i n c o l l e c t o r
c u r r e n t o f
t h e ? r s t
t r a n s i s t o r .
4 . A sweep
g e n e r a t o r a s i n c l a i m 3 wherein t h e
? r s t
t e m p e r a t u r e c o m p e n s a t i n g c i r c u i t
c o m p r i s i n g :
a second
r a n s i s t o r exposed o t h e
same thermal
e n v i
ronment a s t h e ? r s t t r a n s i s t o r and havin g a base
connected t o
t h e b a s e o f t h e
? r s t t r a n s i s t o r ,
an
emitter connected
o
a
source
o f current
an d
a
c o l
l e c t o r ;
a n d
c i r c u i t
means
connected between
t h e
summ i ng
am
p l i ? e r and t h e
e m i t t e r o f t h e s e c o n d
t r a n s i s t o r
f o r
p r o v i d i n g a s i g n a l
t o
c o m p e n s a t e
f o r
t h e r m a l l y i n
duced c h a n g e s i n t h e
c o l l e c t o r
c u r r e n t
o f
t h e
? r s t
t r a n s i s t o r .
5 . A sweep g e n e r a t o r 5 5 i n c l a i m
4
wherein t h e v o l t ’
5
1 5
20
25
30
3 5
40
45
50
55
60
65
6
age source
i n c l u d e s
a
second
temperature
compensat
i n g c i r c u i t .
6 .
A sweep
generator a s i n c l a i m 5 wherein
t h e
s e c
o n d
t e m p e r a t u r e
c o m p e n s a t i n g c i r c u i t
c o m p r i s e s :
a
forward-biased diode
exposed
t o t h e
same thermal
environment a s t h e ? r s t and
second
t r a n s i s t o r s ;
a
s o u r c e
of
r e l a t i v e s t a b l e v o l t a g e ;
and
summing
i r c u i t
h a v i n g
i n p u t s c o n n e c t e d t o t h e f o r
wardbi ased diod e and t h e
s o u r c e
o f r e l a t i v e l y s t a
b l e v o l t a g e and an o u t p u t
connected
t o t h e b a s e s
o f
t h e
? r s t
and
second t r a n s i s t o r s f o r
a p p l y i n g
t o
t h o s e b a s e s a v o l t a g e t h a t
v a r i e s
w i t h t e m p e r a t u r e
t o compensate
f o r
t h e b a s e - e m i t t e r v o l t a g e v a r i a
t i o n o f
t h o s e
t r a n s i s t o r s .
7 .
A
sweep g e n e r a t o r a s i n c l a i m
2
i n c l u d i n g a b u f f er
c i r c u i t connected between t h e ? r s t t r a n s i s t or
and
t h e
c a p a c i t o r .
8 . A weep g e n e r a t o r c i r c u i t a s i n c l a i m 2 wherein h e
i n p u t q u a n t i t i e s a r e q u a n t i t i e s r e p r e s e n t i n g t h e I F
b a n d w i d t h ,
t h e v i d e o
b a n d w i d t h , and
t h e s c a n
w i d t h
o f
a
s p e c t r u m
a n a l y z e r
h a v i n g
a p l u r a l i t y o f s w i t c h e s f o r
s e l e c t i n g s a i d q u a n t i t e s , and t h e
c u r r e n t
s o u r c e means
c o m p r i s e s a p l u r a l i t y o f r e s i s t o r s connected t o e a c h o f
t h e s w i t c h e s .
I l l i ‘I I . ‘