US2349976A - System for directive radiation of electromagnetic waves - Google Patents

Description

May 30, 1944 H. MATSUDAIRA 2,349,976

l SYSTEM FOR DIRECTIVE RADIATION OF ELECTROMAGNETIC WAVES Filed Jan. 14. 1941 w1 ,JW-4

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Patented May 30, 1944 SYSTEM FOR DIRECTIVE RADIATION OF ELECTROMAGNETIC WAVES Hatsutaro Matsudaira, Hsingking, Manchoukuo; vested in the Alien Property Custodian Application January 14, 1941, Serial No. 374,322

(ci. 25o-11) l Claim.

This invention relates to a systemfor directive radiation of electromagnetic waves for obtaining an equisignal intensity zone to meet a predetermined direction by the interlocking of different directive radiations from two dipole antennae of a half wavelength each.

The object of this invention is to provide a directive radiating system of a simple construction, having high efficiency in feeding the antennae, and without the trouble of so-called key-clicks when detecting a continuous equisignal zone of radiations.

Among many applications, the invention may be particularly employed for finding the runway of an acrodrome by detecting, on aircraft intended to be guided, the equisignal zone of radiation, which direction is predetermined to the runway, when the visibility is obscured by clouds, fogs and at night, or during blind flight.

The invention will now be described in detail with reference to the accompanying drawing, in

which: i

Figure l shows an arrangement of a vertical half wave antenna and a reflector,

Figure 2 shows directive characteristics of radiation of the antenna system when a method of feeding the antenna and the length of a reflector have been changed,

Figure 3 shows two vertical antennae of a half wavelength each and their feeding system,

Figure 4 shows two antennae, one acting as a radiator and the other as a reector,

Figure 5 shows the same antennae, but with their relation reversed, and

Figure 6 shows a connection of said two antennae at the instant they are simultaneously fed together.

When we set vertically a metal rod A of a half wavelength excited from an energy source V with a tuned frequency, with a height h above the ground G, and another metal rod B slightly longer than a half wavelength, said two rods A and B being arranged parallel and apart a quarter Wavelength fro-m each other, it is well known that the rod A acts as a vertical antenna and the rod B as a reector lby induced electric current from the rod A, and we get a radiating field of a directive characteristic shown as a polar curve C as shown in Fig. 2, which pattern of radiation will hereinafter be referred to as the rst case for the sake of convenience in explanation.

Now, assume the case in which the metal rods A and B are put in inverse arrangement, that is to say, the length of the rod B is made equal to a half wavelength energized with the same source V, and the rod A is made slightly longer than a half wavelength.` Then the rod B acts as a radiator and the rod A as a reector, and the pattern of the field radiating from this arrangement must be represented by a polar curve D which is perfectly symmetrical to the curve C of the first case. Said pattern D will hereinafter be referred to as the second case.

In both cases, the height h of the metal rods A and B above the ground may influence the directive characteristic in zenithal planes, but not any characteristics in horizontal planes. From the above mentioned patterns of Fig. 2, it is obvious that points of intersection K and H of the curves C and D and a center o of the arrangement of the rods A and B must be on a straight line which is at a right angle to a plane containing the rods A and B, because of the symmetry of the curves C and D. It is to be understood that, in order to obtain a radiation eld having such a directive characteristic shown as polar curves C and D, the impedance of the rod acting as a reector must always be suitably inductive.

According to this invention, for making the impedance of the reflector inductive, I employ a method which will be described with reference to Fig. 3. In Fig. 3, the length of the metal rods A and B is made equal to a half wavelength and divided into two parts at the mid points, where two parallelwire-feeders W and Y are connected, the length of the same being preadjusted to have a reasonable reactance for any rod acting as a reflector.

When a couple of contact points e and f of a change-over relay S, to which is connected a main feeder line from the energy source V, are brought into contact with a couple of contacts c and d of the feeder W, the overall connection will be as shown in Fig. 4. Then, the metal rod A, excited from the source V through the main feeder F and a balancing apparatus Q, acts as a vertical antenna, and the rod B has an open-ended feeder Y connected at its center portion, being the current loop of the rod.

From a theoretical basis, it is understood that an equivalent reactance X of an open-ended feeder line is expressed as X =Z cot gil (l) where I Z: surge impedance of a feeder line,

k: wavelength, standing on a feeder line,

l: length of a feeder line.

The end points u and o of feeder Y form a current-loop of the rod B, and the equivalent reactance at points u and v must be inductive, when the length l of the feeder Y satisfies the following equation:

Where A: wavelength standing n; odd integer.

on a feeder line, with If we take appropriately the lengthrl within a scope of satisfying the Equation 2 and without sourceV, `but both antennaeare simultaneously excited fora AVery short Ainterval of time, as they will` be with the connection shown in Fig. 6. In

said connection of Fig. 6, bothantennae A and a considerable loss resistance, the metal rod B v has an vinductive reactance and acts Vas a reflec-y tor, in which condition all particulars a're'the,

same as the iirst case already mentioned, and

this enables obtaining ka radiatingeld of polar n curve C shown in Fig. 2. Y ,y l

When the couple of contact points e, f of the relay S vcome in contact with a couple of contact points r, t, the overall connection of the system will be as shown in Fig. 5, which is quite opposite and symmetrical to that of Fig. 4, when'a radiating field of this* connection will have the polar curve D shown in Fig. 2. In both cases, the balancing apparatus Q of the main feeder F must be adjusted to obtain the maximum eiiiciency of feeding fromV the energy source V.

Now, if theY change-over relay S is so designed that the couple of contact points e and j moves together according to predetermined signals, for

example, Morse signals E dot for Fig. 4, and

T(dash) for Fig, then radiating elds of polar curves C and D will be alternately rradiated by jeld intensity 'of polar curve P may always be B are excited in the same phase and magnitude,

and of which the'directive characteristic of radiation must be such a polar curve P as shown in Fig.`2, so that' thedireotion of maximum intensity .coincides with the equisignal intensity KOH. It will be necessary to equalize the lield intensityfof the polar curve P to that of polar curves C and D in the direction of KOH to completely avoid key-click.` If an antenna input of Fig. 6 is equal to that of Figsfl -and 5, the

'stronger than that of polar/curves C and D in the direction of equisignal but the Amain Akeying the relay S following the above signals,

which -will fbe detected with a suitable receiving apparatus; For example, in a direction O-M-N of Fig, 2,A stronger E(dot)signals proportional vtohO--N Will `be repeatedly dtectedand weaker T(dash)'sig`nals proportional to .O-M in intervals of E(dot)s, and, in another direction O-'l,l2l, ystronger T(dash) -sigrials andl weaker E(d ot)signals, proportionalv` to O-U and O-R will alternately be detected. On a straight line, 'inV the direction of intersection of polar curves C 'a'nd`D, bothfsign'als are superposed vwith equal '-feeder` F is so"adjusted-as to balance the an-v tenna system in the' connections of Figs. 4 and 5 to obtain the maximum elicie'ncy of feeding energy; Therefore, in the connectiony of Fig. 6, there will be -an unbalahcing orfeeder F and decrease of the input ofv antenna, which causes lthe eld intensity of polar curveeP to diminish to substantially equal value with the intensity of the polar curves, C and D in the direction of equisignal KOH, and the trouble due 'torv key-clicks is practicallyremoved what relaimis; v

A 'systemfor directive radiation of electromagnetic waves,'oompris'ing v`a current'source, a dou.- ble pole change over means connected to said source, 'two 'doublet antennae' each'of which is tuned Ato -a predetermined Wave length, a pair of feeders connected to each of saidantennae and having end contacts adapted to 'be engaged by intensity, "causing a'continuous signal. Thus,vin

an `aerodrome, when 'we assign the direction of equisignal intensity KOH to the runway, the pilot runway by em v during blind ilight may nd ythe ploying suitable detecting apparatus.

However, thefmethod of interlocking two sig.- nals 'E and vTis very important. The'shortest interruptionsV of eduisignalv radiation, if any, cause key-clicks which destroy the continuous equisignal, `and make it diicult to detect the runway, especially in aural detect-ion. To overcome this difculty,"according to this invention, the change-over `vrelay-S is designed in the fol'- lowing manner. Twocouples of contact points c, 'di and 7', t Iare made of adjustable spring metal and the distances between the same and .Ill

said changeover i'neans, `said feeders .having an,

' N.inductive reactan'ce at th'ejfrequency to whichA said' antenn'aes are tuned when said end icon-- tacts arey opened by "said change over means so, as to cause the antennae respectively'connectedi to the feeder involved to yact as a reliector and allowing two Vel'ds ft'o be radiated by the operation ofl said change over means, said fields having diferentdirectional lcharacteristics of symmetrioal pattern and said changeover `means comprising means forconnecting both 'feeders `simultaneollsly Yto the c's'urrentl source during the change overpe'rio'd soasto cause excitation `o1 both antennae in the same phase and magnitude l and radiate a third'eld foffdierent directional *characteristics than Y l l u 1 -thefrsttwofand thereby avoid-any interruption" of `radiation from the system during said-changeover period.

HATSTARO MATSUDAIRA.

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