close

Вход

Забыли?

вход по аккаунту

?

Патент USA US2410007

код для вставки
Oct. A29, 1946.
D. BLITZ
2,410,006
BALANCED DETECTOR FOR ALTIMETERS
Filed May so, 1944>
I:
n
Hrm/aver
Patented Oct. 29, 1946
2,410,005
perreo sTaTes eATeNT
FFECE
2,410,006
BALANCED BETECT赗 F躌 ALTEIV虴TERS
Daniel Blitz, Princeton, N. l1., assignor to Radio
Corporation of America, a corporation of Dela
?vare
Appiication May 30, 1944, Serial No. 538,052
l
5 Claims.
My invention relates to balanced detectors for
(Cl. Z50-27)
2
is a View showing the mechanical arrangement
of my double coupling loop employed in the re
ceiver illustrated in Fig. 1; and Figure 3 is a View
In application Serial No. 445,720, 駆ed June 4,
showing the relative positioning of the coupling
i942, in the name of Royden C. Sanders, Jr.,
loops to the tuned line of Fig. 1. In the several
entitled Frequency modulated altimeter or dis
figures,
like parts are indicated by the same ref
tance indicator, there is described a balanced
erence characters.
beat frequency detector comprising diodes and a
Referring to Fig. 1, the invention is shown ap
tuned line in which undesired amplitude modu
lation in an FM altimeter or radar system is 10 plied to the balanced detector of a radio altime
ter. The altimeter comprises a frequency-modu
balanced out. In any balanced detector that is
lated radio transmitter ill which radiates a fre
employed in a system operating on high radio
quency-modulated carrier wave from an antenna
frequencies such as those utilized in radar sys
altimeters or other distance measuring systems of
the frequency modulated or FM type.
i i. Suitable means for sweeping the carrier Wave
tems, it is diii頲ult to obtain a perfect balance.
An object of the present invention is to provide 15 frequency through a certain frequency range
periodically is indicated at I2.
an improved detector of the balanced type, and
The associated receiver includes a balanced de
particularly to provide an improved method of
tector which comprises a pair of diodes I3 and I4
and means for coupling to a balanced detector.
that have signal applied thereto from a tuned
A further object of the invention is to provide
an improved balanced detector for use in FM dis 20 line E6 having a grounded center conductor Il
associated therewith. The reflected signal is
tance measuring systems such as altimeters,
A further object of the invent-ion is to provide >?picked up by a receiver antenna I8 and is sup
plied through a coaxial line IS to a coupling loop
a detector of the balanced type that can be ad
El which (as shown in Fig. 3) is positioned
justed to an exact bala-nce with a minimum of
difnculty.
?
under the conductor Il with its plane at right
25
angles to the plane of the tuned line I 5. Thus
A still further object of the invention is to
the reiiected signal is applied with like polarity
provide an improved coupling means for balanced
to the anodes i5 and 2t of the diodes I3 and Ill.
detectors operating on centimeter Wave signals.
Stated differently, it is applied in parallel relation
In one embodiment, the
fention is applied to
a balanced diode detector in which each detector u9 to the diodes.
rl?he same frequency-modulated signal that is
supplied to the transmitter antenna II is also
supplied as a heterodyning signal through either
tube has the reflected signal and the heterodyn
ing signal applied thereto with the two signals
having a phase relation with respect to each
other at one tube that is the opposite of their
a coaxial or a two-wire line 253 to a coupling loop
2l which is made a double loop for the purpose of
phase relation with respect to each other at the
improving the circuit balance as explained here
inafter. The double loop 2l is positioned with its
plane parallel to the plane of the tuned line I5
other tube. The reflected signal may be applied
to the detector tubes in parallel relation while
the heterodyning signal from the transmitter is
and it is centered with respect to the line It as
applied to
push-pull relation through my
improved coupling circuit which comprises a dou 40 illustrated. Thus the heterodyning signal is ap
plied With opposite polarities to the anodes I5
ble coupling loop. The output signal may be
aud gli of the diodes I3 and Ill, i. e., it is applied
`taken ofi the anode of one tube and olT the cath
in push-pull relation instead of in parallel rela
ode of the other tube and the two output signals
tion. The two applied signals produce a differ
combined, whereby any amplitude modulation of
the applied signals, and particularly of the het
or beat frequency signal which is a measure
erodyning signal, may be balanced out. The
of the time required for the signal radiated from
heterodyne or dii頴rence frequency signal, on the
antenna Ii to reach antenna I8 by re馿ction and
other hand, appears in the detector output cirm
which is, therefore, a measure of the distance?to
cuit. Likewise, any interfering or jamming sig
nal may be balanced out.
The invention will be better understood from
the following description taken in connection
with the accompanying drawing in which
Figure l. is a circuit and block diagram of an
FM altimeter embodying the invention; Figure 2
50
the reilecting surface.
The -tuned line l5 includes Itwo coaxial conduc
tors 3| and 32, the inner conductors of Which are
connected Ito the anodes Ill and 2d. The outer
conductors ci the coaxial conductors 3i and 32
are connected at each end lto the inner conductor
by means of capacitors 33, 34, 36 and 31 whereby
2,410,006
3
the inner and outer conductors are at the same
4
receiver shielding (not shown). As shown in Figs.
1 and 2, one of the loops 2l is connected through
potential at radio frequencies.
a terminating resistor E@ to one side of the input
The cathode 33 of diode I3 is conductively con
line 26; the other end of this loop may be con
nected to ground preferably through a low im
nected to ground through the shielding can 45.
pedance resistor 33 and a capacitor llI in parallel.
Likewise, the other of the loops 2l is connected
The cathode � of diode I6 is connected to ground
through a terminating resistor 515 to the other
at radio frequencies through a capacitor �. The
side of the line El; and the other end of this loop
cathode 38 may be connected directly to ground,
is connected to the shielding can 45. lf desired,
if desired, but the connection through capacitor
the terminating resistors 50 and 55 may be lo
4I is preferred since it makes the circuit more 10 cated `adjacent to the ground connections instead
symmetrical and more easily balanced. This is
of in the locations illustrated.
true because capacitor 縤l at diode I3 corresponds
The transmitter end of the line 2li preferably is
to capacitor 43 at diode I4, the latter capacitor
grounded at its electrical midpoint 6@ for balanc
being required where the beat frequency signal
ing out any electrostatic pickup from the trans
is taken off the cathode. The resistor 39 is re 15 mitter because any signal thus picked up and
quired to complete the direct-current path for
supplied -to the detector will be in the wrong
diode i3. It may have a resistance of 1GO ohms,
phase 籥nd will unbalance the detector. How
ever, grounding the transmitter end of the line
Z6 does not always eliminate signal due to capac
radio frequencies by means of bypass capacitors 20 ity pick-up for the reason that the grounded point
縧ll and d6. Also, one side of the heater filament
Sii is not always exact as to location. Any such
for cathode 縧2 is held at ground potential at radio
pick-up current may have diiferent values in the
frequencies by means of a bypass Q1, the other
two sides of the line 2li. It is because of this that
side of the filament being connected directly to
the double loop 27 is employed. 1t will be ap
for example. Each side of the heater 駆ament
for cathode 38 is held at ground potential at
ground.
Referring again to the tuned line i6, the ends
of the outer conductors of lines 3! and 32 are
connected to ground through a connection 縤8 and
parent that the coupling to the tuned line 3I, 32
from 4any part of the doubleloop 2l will include
both leads of the line 2li and any current differ
ence will be averaged out.
the center conductor I'I. An adjustable shorting
Referring now to the detector output circuit, it
bar figa, 49h is provided for tuning the two cir 30 will be seen that the beat frequency signal is
cuits i?ormed by each coaxial line and the center
taken ofi the anode l5 through the inner con
conductor il to the mid-frequency of the signal
ductor of the coaxial line "al and supplied through
from the receiver antenna I8. It will be seen
a conductor
a resistor 5G and a portion of
that there is one resonant circuit that may be
a resistor 5l to a variable tap 58 and an output
traced from the :anode I5 through the capacitor
resistor 59. The beat frequency signal also is
33, the conductor BI, the snorting bar section @3a
taken 01T the cathode f1.2 through a low impedance
and the conductor I'I to ground; and a second
filter resisto-r @I (having a resistance of 100 ohms,
resonant circuit that may be traced from the
for example) and supplied through a resistor G2
anode 25J through the capacitor 3S, the conductor
and the other portion of resistor 5l to the variable
32, the shorting bar section 49h and the con- tap 53 and the output resistor 52. A filter capaci
ductor I?I to ground.
tor d3 is connected between ground and the end
A third resonant path is provided by a capacitor
of filter resistor 5I remote from the cathode.
5I that is in adjustable contact with the outer
The resistor 5I and the capacitor ?23 are provided
conductors of coaxial conductors 3l and 32. This
to keep the radio frequency out of the output
path may be traced from the anode I5 through
circuit. The beat or audio frequency circuit for
the capacitor 33, the conductor 3i, the capacitor
diode id is completed from the anode 2G, through
5I, the conductor 32 through capacitor 36 to the
the inner conductor of coaxial Vline 32 and
anode 29. This third path is made resonant at
through a connection Eli to the grounded con
the mid-frequency of the heterodyning or mixing
Il.
signal from the transmitter, this mid-frequency 50 ductor
From the foregoing, it will be evident that any
being the same, of course, as the mid-frequency
of the received reilected signal.
amplitude modulation may be balanced out by
adjusting the tap 5?� since this modulation at
It will be seen that the lines of force from the
one anode is in phase with that at the other
loop 2l will cut the conductors 3l and 32 as in
dicated in Fig. 3 whereby the 駉w of transmitter 55 anode. rPhe beat frequency signal, on the other
hand, is 180 degrees out of phase at one anode
or mixing signal in tuned circuit I6 will be as
with respect to the beat frequency signal at the
indicated by the arrows ir in Fig. l. Thus, the
other anode whereby these signals add due to
mixing signal at the anode l5 is 180 degrees out
of phase with the mixing signal at the anode 2li.
phase reversal obtained
the output connec-Y
The lines of force from the loop ZI out the con 60 tions,
It may be noted, merely by way of example,
ductors 3l and 32 as shown in Fig. 3 whereby the
that all the capacitors shown in Fig. l, except
flow of reflected signal will be as shown by the
the tuning capacitor 52, have a capacity of 55
arrows iR in Fig. l. It will be seen that the
reflected signal on the anode i5 is in phase with
the reflected signal on the anode Eil. '
micro-microfarads. Also, resistors 56 and S2 may
5 be 50cc ohms each, resistor si
be 250cc cams
and resistor
may be 47,060 ohms. These values
are for a receiver operating at a 440 megacycle
carrier frequency that is being swept through a
range of 40 rnegacycles,
70 It should be understood that the mixing signal
and the reflected signal may be applied to the
The loops 2l and 2l are adjustable parallel to
the plane of the lines BI and 32 to permit balanc
ing adjustments to compensate for any difference
in diode characteristics or in the physical con
struction of the tuned circuit Sii-32 or other
parts of the receiver. The loop 2i preferably is
terminated by a tuning capacitor 52. The double
detector in parallel relation and push玴uil rela
loop il may be supported by a block lili of insu
tion, respectively, if desired instead of in the
lating material as shown in Fig. 2 and covered by
opposite way described above.
a rectangular shielding can 縧5 that is part of the 75
2,410,006
5
I claim as my invention:
6
prising a double inductive loop coupled to said
1. In combination, a baia-need circuit compris
ing a tuned line, a two-wire line for supplying
signal from a signal source to said tuned line,
tively, of said tuned line, the midpoint of said
said two-wire line being grounded adjacent to
said signal source at substantially the electrical
double loop being grounded whereby each side
of said double loop includes conductors that
midpoint of said two-wire line, and means for
coupling said two-wire line to said tuned line,
said means comprising a double inductive loop
carry the current flow or" each of the conductors
of said two-wire line so that any coupling due
tuned line, said double loop having two sides
that are adjacent to the two conductors, respec
to misplacement of said grounded point of the
,
10 two-wire line is balanced out.
ing two sides that are adjacent to the two con
4. A balanced detector comprising a tuned line
ductors, respectively, of said tuned line, the mid
having an electrical midpoint, a pair of recti
point of said double loop being grounded whereby
韎ers coupled, respectively, between said midpoint
each side of said double loop includes conductors
and opposite sides of said line, a multiple turn
that carry the current 駉w of each of the con 15 coupling loop coupled to said tuned line, a pair
ductors of said two-wire line so that any cou
of conductors for supplying signal to said multi
pling due to unequal current iiow in opposite
ple turn coupling loop, said conductors being in
sides of said two-wire line is balanced out.
ductively coupled through a coupling loop por
coupled to said tuned line, said double loop hav
2. In combination, a balanced detector com
tion to a signal source, said conductors being
prising a tuned line and a pair of rectifiers 20 connected to ground at a balance point on said
coupled to opposite sides, respectively, of said coupling loop portion, said multiple turn coupling
line, a two-wire line for supplying signal from
a signal source to said tuned line, -said two-wire
line being grounded adjacent to said signal
loop having two sides that are adjacent to the
two conductors, respectively, of said tuned line,
each side of said multiple turn loop including a
source at substantially the balance point of said 25 pair of wires carrying the current of each of said
two-wire line, and means for coupling said two
conductors, respectively, of said pair.
wire line to said tuned line, said means corn
5. In a frequency-modulated radar system, a
prising a double inductive loop coupled to said
balanced detector comprising a tuned line having
tuned line, said double loop having two sides that
an electrical midpoint, a pair of recti馿rs coupled,
are adjacent to the two conductors, respectively, 30 respectively, between said midpoint and opposite
of said tuned line, the midpoint of said double
sides of said line, a double loop coupled to said
loop being grounded whereby each side of said
tuned line, a pair of conductors for supplying
double loop includes conductors that carry the
signal to said double coupling loop, said con
current flow of each of the conductors of said
ductors being inductively coupled through a cou
two-wire line so that any coupling due to mis 35 pling loop portion to a, signal source, said con
placement of said grounded point of the two-wire
ductors being connected to ground at a balance
line is balanced out.
point on said coupling loop portion, said double
3. In combination, a balanced circuit compris
coupling loop having two sides that are adjacent
ing a tuned line, a, signal source, a two-wire line
to the two conductors, respectively, of said tuned
for supplying signal from said signal source to 40 line, each side of said double loop including one
said tuned line, said two-wire line being induc
oi said conductors of said pair whereby differ
tively coupled to said signal source through a
ences in current flow in the conductors of said
coupling loop which is grounded at substantially
pair are averaged out.
its balance point, and means for coupling said
DANIEL BLITZ.
two-wire line to said tuned line, said means com 45
Документ
Категория
Без категории
Просмотров
0
Размер файла
499 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа