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Патент USA US2405174

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:
A. ALFORD
2,495,174
TRANSMI S S ION CONTROL. NETWORK
Filed May 27,} 1942
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YlNVENTOR'
' BY
Patented Aug. 6, 1946
2,405,174
UNITED STATES PATENT OFFICE}
2,405,174
(
TRANSMISSIGN CONTROL NETWORK
Andrew Alford, New York, N. Y., assig'nor to
Mackay Radio and Telegraph Company, New
York, N. Y., a corporation of Delaware
Application May 27, 1942, Serial No. 444,660
4 Claims.
(Cl. 178-44)
1
This invention relates to high frequency trans
mission systems and more particularly to im
2
line 2, to a load impedance 3 which is made sub
stantially equal to thecharacteristic impedance
pedance matching networks for high frequency
of line 2, In such a transmission line there will
lines.
be no standing waves. If, then, a conductor 4
It is often necessary to provide high frequency
is coupled to the line it is found that standing
‘lines with networks or the like in order that the
waves are produced on the line, as shown at 5.
line may be matched in impedance with a load.
The conductor has a characteristic impedance
A number of such systems have been proposed
of Z0’ and a length 1. With such a relationship
such as short sections of transmission line,
it is found that the spacing of the conductor
commonly called building-out sections, or other 10 from the standing waves maximum, Imax is given
networks coupled to the line. In many cases it
by the value P. Since such a network is capable
is found that the known forms of networks may
of producing standing waves in a matched line,
be undesirable because of the difficulty of apply
it is clear that a similar network applied in a
ing them to installations already existing or be
transmission line normally having standing
cause of their size or position.
15 waves of the same Imax to Imin ratio as the waves
It is an object of my invention to provide an
5, and spaced the same distance P from the Imax
impedance adjusting network which is readily
position will serve to match the frequency of the
applied to any transmission line and which is
line to the load in accordance with the reci
relatively small and light so that it will not add
procity theorem.
materially to the weight or wind resistance of a 20
In Fig. 1A is shown such a system in which
line when applied thereto.
the source I is connected over a transmission
According to a feature of my invention the
line 2 to a load 3a, the line normally having
stated objects may be achieved by coupling to
standing waves as indicated at 5a. The network
the transmission line a conductor of given char
4 of length Z and characteristic impedance Z0’
acteristic impedance value, the length being de 25 serves to match the impedance of the line as il
termined by the characteristic impedance of the
lustrated in this ?gure. It can be seen that this
line and the standing wave ratio in the line and
form of network will readily serve to secure im
the position along the line being determined by
pedance match in most transmission lines if the
the selected length and the characteristic im
proper dimensions and position are chosen. Fur
pedance of the line.
thermore, since the network is of small vertical
A better understanding of my invention and
dimension it will exert very little bending stress
the objects and features thereby will be had by
on the line during high winds or the like, and is,
the particular description thereof made with ref
therefore, particularly Well suited for use on open
erence to the accompanying drawing in which
wire high frequency transmission lines which
Figs. 1 and 1A are diagrams used to explain 35 are exposed to the weather.
the principles of my invention;
In order properly to select the desired network
Figs. 2 and 3 are curves showing characteris
of dimension to satisfy the impedance matching
tics of networks used in myjnvention;
requirement, it is possible to provide curves to
Fig. 4 illustrates one form of my invention ap
aid in its selection. Such curves are illustrated
plied to a line feeding an antenna.
40 in Figs. 2 and 3.
'
Fig. 5 illustrates a further modi?cation of my
In Fig. 2 is shown a family of curves, repre
invention; and
senting different values of the ratio of charac
Fig, 6 illustrates still another form of my in
teristic impedance Z0v of the line to the charac
vention.
teristic Z0’ of these networks, plotted with the
The conventional forms of impedance match 45 length of the units in electrical degrees against
ing networks are often cumbersome, particularly
the standing wave ratio Q, that is
when used on high frequency supply leads to
radio antenna. I have discovered that an im
pedance matching may be achieved by use of a
simpler network consisting of a relatively long 50 Fig. 3 then shows a set of curves for determining
narrow conductive arrangement fastened to the
the spacing P, the spacing 'P being shown in
conductors,
In Fig. 1 the effect of the network is demon
electrical degrees plotted against the length Z in
electrical degrees.
strated. In this arrangement a high frequency
When it is desired to apply a network to match
source I is shown connected over a transmission 55 a given standing wave ratio in a line, the curves
3
2,405,174
4
length of the units may be determined by the
of Fig. 2 are ?rst consulted. Assume, for exam
ple, the standing wave ratio is 3. It is seen that
number of loops added to the line, so that the
proper adjustment and length can be easily made
there are three sets of networks which will be
satisfactory depending upon the characteristic
in the ?eld.
While the impedance of such networks as
impedance of the networks which it is desired to
use. The characteristic impedance of the net
shown at 61, 62, may be calculated, this calcula
tion is quite involved and it is often more feas
work may be readily calculated for any ?at metal
ible to ?nd the impedance thereof by experiment.
objects of the type illustrated in Fig. 1 or for
The impedance of such networks may be deter
metal rod forms such as shown in Fig. 5. Ac
cordingly, the desired width of plate or diameter 10 mined by use of the arrangement similar to that
shown in Fig. 1. Since the standing wave ratio
of rod is found by calculation and the length is
on the line which is created by the unit networks
then determined by reference to Fig. 2. We will
assume ?rst that curve 22 is chosen. It will be
can be readily measured, and the characteristic
seen that this requires a network having a length
impedance Z0 is known, the characteristic im
of substantially 60 electrical degrees. Turning
pedance of any unit of length I may be readily
then to Fig. 3, the length Z found from Fig. 2
calculated after taking the measurements from
is laid out on the horizontal axis, and the spac
the known functions. In order to secure the
required data loops of a particular size may be
ing P can'then be determined from this. In the
given example it is found that the spacing P must
strung on a matched impedance line such as
then be made of the order of 2.5 degrees from
shown in Fig. 1, and the information as to the
standing wave ratio produced thereby determined
the current maximum.
It is clear that any desired, impedance match
for different lengths of network having a given
ing network may be secured from a family of
looping dimension. Thus, a family of curves
curves as shown in Figs. 2 and 3. While only
similar to those shown in Fig. 2 may be readily
plotted experimentally. Likewise, the spacing P
a few curves have been shown it is readily ap
parent that the number of curves which may be
may be determined at the same time and a set
provided is substantially in?nite, and, therefore,
of experimental curves similar in type to that
the variety of networks that can be provided in
shown in ‘Fig. 3 may be plotted. When it is de
accordance with my invention is also in?nite.
sired to match the impedance of a transmission
One advantage of the ?at sheet-like network 30 line, the standing wave ratio of the line may be
is that it may be readily applied and adjusted
?rst measured and the desired length of loop net
experimentally without reference to the curves.
work may be derived from the sets of curves in
In Fig. 4. is illustrated an arrangement in which
a similar manner to that previously described.
transmission line 48 is coupled to a dipole an
When this has once been determined all that is
tenna 4|. Matching sections 42, 43 are provided
necessary is to fasten the conductor forming the
in each of the lines. If these sections are found
loops to the transmission line at one point and
to be too short, additional sections 44, 45 may be
proceed to make the number of intermediate loops
hung on the ends thereof. Further, if the sec
necessary to produce the desired length of net~
tions 42, 43 are found to be too long they may
work. It is, therefore, seen that this particular
be readily trimmed oif, being made of light sheet 40 form of network arrangement shown in Fig. 6 is
readily applicable to transmission lines in the
metal.
'
In Fig. 5 is illustrated how another form of
?eld and may be applied by any attendant who is
network comprising sections of line 52, 55 of
in charge of the transmission lines.
different diameter than the conductors of line 13!}
While I have disclosed speci?c apparatus for
may be applied to the line. The impedance of 45 accomplishing this result in accordance with my
the line sections may be readily calculated and
invention, it should be distinctly understood that
they may be applied to the line by use of the
these are given merely by way of example, and
diagrams of Figs. '2 and 3 or similar diagrams
not as limitations. In fact, ‘any desired form
calculated for this form of conductor.
-
of impedance network can be used so long as
While the solid metal arrangements shown in ’
the conductor is chosen with respect to the unit
Fig. 4 may be provided to secure the desired im
impedance value and taking into consideration
pedance matching, such elements may be unde
the characteristic impedance of the line, the
standing wave ratio of the line and the proper
sirable on outside lines due to the wind resistance.
position determined by this characteristic im
It is therefore clear that in place of solid metal
sheets as shown therein wire screening or netting 55 pedance and the selected length.
What is claimed is:
may be used.
Although sheets of screening or thin metal
1. In a high frequency transmission the com
bination comprising a high frequency transmit
may be provided for achieving the impedance
ting line complete in itself for transmitting en
matching as described above, it is often desir
ergy to a load, a separate readily applied im~
able to build up units in the ?eld out of wire
pedance matching network comprising conduc
loops. In Fig. 6 is shown a form of network ap
plied to a transmission line 46 connected to an
tive means having a given characteristic imped
ance connected to a conductor of said line
antenna 4!, in ‘which each of the units BI, 52
throughout substantially the entire length of said
comprises a plurality of small loops of wire fas
tened to the transmitting conductor. If desired 65 conductive means, said conductive means hav
ing an overall length determined from the selec
these wire loops may be reinforced by a third
tion of a characteristic among those existing be
wire 63, 64, as shown. Such a construction is
tween standing wave ratio in said transmission
preferable to the netting or screening since the
line and network lengths, for different ratios be
openings are much larger and do not facilitate
the formation of sheets of sleet. The impedance 70 tween characteristic impedance of said line and
of networks including approximately said given
matching with such networks as shown in 63, 764
characteristic impedance, and said conductive
can be accomplished in a similar manner to that
means having a position along said line with re
described above. In addition, however, the net
spect to the standing wave maximum of standing
work such as shown at ‘El, 62, has the additional
advantage overthe use of the sheets in that the 75. waves in said line determined by the selection of
5
2,405,174
6
one among the existing characteristics between
network lengths and positions for di?erent ratios
between the characteristic impedance of said line
and of networks including approximately said
given characteristic impedance.
2. An impedance matching network according
existing characteristics between network lengths
and positions for different ratios between the
characteristic impedance of said line and of net
K
u
to claim 1 wherein said conductive means com
prises a metal sheet fastened to said conductor.
3. In a high frequency transmission the com
works including approximately said given char
acteristic impedance.
4. A high frequency transmission line system
comprising a high frequency transmitting line
including an impedance matching network com
prising conductive mea-ns having a given charac
bination comprising a two~conductor high fre 10 teristic impedance connected to a conductor of
quency transmitting line complete in itself for
said line, said conductive means having an over
transmitting energy to a load, a separate readily
all length determined from the selection of a
applied impedance matching network compris
characteristic among those existing between
ing conductive means connected to each conduc
standing wave ratio in said transmission line and
tor of the line throughout substantially the en
network lengths, for di?erent ratios between
tire length of said conductive means, said con
ductive means de?ning a predetermined area in
the plane of said conductor and having a given
characteristic impedance and an overall length
determined from the selection of a characteristic
characteristic impedance of said line and of net
works including approximately said given char
acteristic impedance, and said conductive means
having a position along said line with respect to
the standing wave maximum of standing Waves
in said line determined by the selection of one
among the existing characteristics between net
work lengths and positions for different ratios
between the characteristic impedance of said line
among those existing between standing wave ra
tio in said transmitting line and network lengths
for different ratios between characteristic im
pedance of said line and of networks including
approximately said given characteristic imped
ance, and said conductive means having a posi
tion along said line with respect to the stand
ing wave maximum of standing waves in said line
determined by the selection of ‘one among the
25
and of networks including approximately said
given characteristic impedance, said conductive
means comprising a series of looped wires each
terminating at said conductor.
ANDREW ALFORD.
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