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Патент USA US2405073

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Filed Oct. 28, 1943
Inventor‘ :
Roy E. Troell,
by His ttorney.
Patented July 30, 1946
Roy E. Troell, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
Application October 28, 1943, Serial No. 507,952
3 Claims.
(Cl. 172—-245)
The present; invention relates to a phase com
parator adapted for use at high frequencies.
The object of my invention is to provide a
phase comparator in which the input and meas
uring circuits can be grounded without impair
ing the accuracy and in which the need for a 90
‘The phase comparison circuit, because of the
symmetry in the input and measuring circuits
which permits grounding along the axis of sym
degree phase shifting network is eliminated.
The novel features which I believe to be char
acteristic of my invention are set forth with par
metry, is suitable for use at high frequencies; e. g.
30 me. The parallel tuned bridge circuits are an
improvement over separate 90 degree phase shift
ing networks. If there is any stray capacity. such
as that resulting from the leads or the diodes
I1, l8, it can be neutralized by inductances 22. 23
ticularity in the appended claims. My invention 10 connected across the terminals l, 2 and induct
ances 24, 25 connected between ground and the
itself, however, both as to its organization and
method of operation, together with further ob
terminals l4, l6.
While I have shown particular embodiments of
jects and advantages thereof, may best be un
derstood by reference to the following descrip
my invention, it will be understood that many
tion taken in connection with the accompanying 16 modi?cations may be made without departing
drawing in which the single ?gure is a diagram of
from the spirit thereof, and I contemplate by the
a phase comparator embodying my invention.
appended claims to cover any such modi?cations
Referring to the drawing there is shown a
phase comparator having pairs of input terminals
as fall within the true spirit and scope of my
I and 2 to which are applied the voltages E1 sin 20
What I claim as new and desire to secure by
wt and E2 sin (wt+0) to be compared in phase.
Letters Patent of the United States is:
One of each pair of terminals is grounded and
1. In a phase comparator, grounded input cir
across the respective pairs of terminals are con
cuits for the voltages to be compared in phase,
nected a bridge circuit 3., 4 each of which com
lagging and leading phase shifting networks
prises equal resistances 5, 6 and inductances ‘I 25 across each of the input circuits. center tapped
and condensers 8 having reactances at the fre
decoupling impedances respectively cross con
quency of the voltages to be compared equal in
necting the lagging phase shift voltage of one and
magnitude to the resistances. At the terminals I
the other input circuit to the leading phase shiit
and 2 the bridge circuits are parallel tuned at the
voltage of said other and one input circuit. square
operating frequency. Because the resistances are 30 law detectors for the voltages at said center taps,
equal to the inductive and capacitive reactances,
and means for subtracting the detected voltages.
the voltages at the intermediate bridge terminals
2. In a phase comparator, input circuits for
9, Ill and ll, [2 respectively lag and lead the
the voltage to be compared each connected to
voltages applied to the terminals I and 2 by 45
diametral terminals of a parallel tuned bridge
degrees. By means of decoupling resistances l3 35 circuit, intermediate terminals of said bridge cir
the lagging voltage from terminal 9 is added to
cuits having potentials leading and lagging with
the leading voltage from terminal l2 producing
respect to the input voltages, center tapped de
a resultant voltage at the center tap l4 propor
coupling impedances respectively cross connect
tional to E1 sin (wt—45°)+Ez sin (wt+6'+45°).
said leading potential of one and the other
Similarly by decoupling resistances I5 the lead 40
bridge circuits with said lagging potential
ing voltage from terminal I0 is added to the
of said other and one bridge circuit, square law
lagging voltage from terminal II to produce at
detectors for the resultant voltages at said cen
the center tap i B a resultant voltage proportional
taps, and means for subtracting the de
to E1 sin (wt+45°)+E2 sin (wt+0—45°). The
voltages at terminals l4 and [6 are respectively 45 tected voltages.
3. In a phase comparator, input circuits for
fed through square law detectors, such as diodes
the voltages to be vcompared each connected to
l1 and i3. causing the charging of grounded con
diametral terminals of a parallel tuned bridge
densers l9 and 2!! in accordance with the squares
circuit, said bridge circuits having arms of equal
of the resultant voltages. Because the diodes are
connected in opposite polarity, the condensers are 50 impedances consisting respectively of resistances
and reactances whereby at the intermediate
charged to voltages of opposite polarity and the
bridge terminals the input voltages are shifted
addition of the condenser voltages at terminal 24
in phase 45° leading and lagging, means for re
is in effect a subtraction which results in a D.-C.
spectively adding the leading voltage of one and
voltage above ground proportional to E1 E2 sin 0
the other bridge circuit to the lagging voltage of
at terminal 2!. There are also A.-C. voltages
which do not affect a D.-C. voltmeter. The volt
said other and one bridge circuit to obtain re
age at terminal 2|, when measured by a D.-C.
voltmeter. will accordingly change sign as the rel
sultant voltages, square law detectors for the re
sultant voltages, and means for subtracting the
ative phase displacement (0) goes from positive
detected voltages.
to negative so the operator can tell whether a
voltage is lagging or leading.
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