US2210066A - Aerial and feeder system for use in high frequency signaling systems - Google Patents

Description

Aug. 6, 1940. 2,210,066

AERIAL AND FEEDER SYSTEM [FOR USE IN HIGH FREQUENCY SIGNALING SYSTEMS E. c. CORK ET AL .Filed June 24, 193'? I I l l I l I I I l Fig.2.

INVENTORS EDWARD cz-r/z CORK JOSEPH ZADE PAM/SE) ATTORNEY Patented Aug. 6, 1940 2,210,066 1 g I AERIAL AND FEEDER SYSTEM i on USE IN HIGH FREQUENCY SIGNALING SYSTEMS Edward Cecil Cork, Ealing, London, and Joseph Lade Pawsey, Hillingdon, England, 'assignors to Electric & Musical Industries Limited, Hayes,

Middlesex, Britain England, a company of Great Application June 24, 1937,Serial"l lo. 150,030

In Great Britain July 1936- 11 Claims. (01. Zane-3a "This invention relates to high frequencysignaling systems and has particular reference to short Wave aerial and feeder systems employing frequencies of the order used for television transmission. The invention is also applicable to aerials used in the reception of signals.

In such systems it is common practice to use an aerial consisting of a tuned half wavelength of wire conductor fed at one end from a transmitter.

The impedance of such an aerial at the feed point is usually of the order of two thousand ohms while the characteristic impedance of a concentrio feeder connecting the aerial with the transmitter may in such acase be of the order of one one is involved. A well known type of transformer for this purpose is disclosed in, the specification of British Patent No. 282,905, or again, a tuned coil with an adjustable tappingflpoint may be used.

The types of impedance matching device previously proposed introduce considerable selectivity and constitute additional means requiring adjustment;

It is the object of the present invention to pro vide an impedance matchingarrangement which does not introduce undesirable selectivity.

According to the present invention; the physical dimensions of an aerial of which the electrical length is equal to or approximately equal to an integral number of half-wavelengths of thecarrier frequency radiated or received are made such that the ratio between the open-ended impedance of the aerial and the characteristic impedance of a feeder or other circuit connected with the aerial is not greater than 4:1.

'In'carrying the invention into practice it is.

preferred to match the impedance of the aerial with that of the feeder or other circuit connected with it so that the use of a separate transformer can be dispensed with. However, even if a separate transformer is used, as the ratio of transformation ,will be low, it is less difficult to obtain a transformer which will pass a sufficiently wide band of signal frequencies such as is required to example with reference to the accompanying drawing; in'which:

Fig. Us a diagrammatic representation of certain electrical characteristics of an aerial and Fig. 2 shows diagrammatically a particular form of aerial.

Referring to Fig 1 of the drawing, A, B represents a tunedhalf wave aerial and r is a resistance which represents the series radiation resistance of the aerial," assumed to be concentrated at the centre.

If ZOA is the characteristic impedance of the aerial, the resistanc'e R at the pointA is given by the equation:

R=i I r Assuming that it is'desired to'match the aerial to a feederof characteristic impedance Znr, this can be done bymaking I T 1 from which I I. v A= or The characteristic impedance ZUA- of the aerial is determined by thediameter of the aerial conductor and in the case of a circular cylinder of radius a,

In the case of a feeder having a characteristic impedance Zn" of seventy eight ohms, connected to a circular aerial having a characteristic impedanceZoA of seventy-four'ohms and a series resistance 1' of seventy ohms, the wavelength. x to be used being 6.5 metres, the'radius a of the aerial should vbe.6.7inches. j o

Referring to Fig. 2 of the drawing a half-wave dipole aerial, A, B is connected at its lower end to the inner conductor C of a concentric feeder F. A centre tapped half Wave conductor. X,.Y effectivelyearths the ends of the outer sheath of the conductor F for the working frequency and a similar conductorX}, Y serves the purpose of furthersuppressingwaves on'th'e outside of'the sheath. v

The aerial conductor itself may consist of a tube of metal or wire gau'ze,"a large strip of metal or a number of wires in paralleL'or in fact any conducting surface, the dimensions of which may be modified in accordance with the invention. In the case of a metal or gauze tube, the required dently permit considerable decrease in its resist ance.

If the open-ended impedance of the aerial is made low enough to match the characteristic impedance of the feeder, as above described, the use of a transformer between the aerial and feeder is unnecessary. However, satisfactory results ac.- cording to the invention, may be obtained even when the characteristic impedance of the aerial is not more than four times as great as the latter. In this case, as is well known, transformers with the required small ratio of transformation, (approximately 2.1) can be readily obtained, which do not have an objectionably high selectivity.

We claim: a

1. An aerial having a feeder connected thereto, said aerial having an electrical length equal to an integral number of half wavelengths of the carrier frequency to which the aerial is tuned, said aerial having substantially a cylindrical form for a substantial portion of its length which tapers into substantially a conical form whose apex is connected to said feeder, the diameter of said aerial being such that the ratio between the open-ended impedance of the aerial and the characteristic impedance ofsaid feeder is not greater than 4:1.

, 2. An aerial having a feeder connected thereto, said aerial having an electrical length approximately equal to an integral number of half wavelengths of the carrier frequency to which the aerial is tuned, said aerial having substantially a cylindrical form for a substantial portion of its length which tapers into substantially a conical form whose apex is connected tosaid feeder, the diameter of said aerial being such that the ratio between the open-ended impedance of the aerial and the characteristic impedance of said feeder is not greater than 4:1.

3. A high frequency signal transmitting system comprising in combination transmitting apparatus, a feeder and an aerial connected with said transmitting apparatus by said feeder, said aerial havingan electrical length equal to an integral number of half wavelengths of the carrier frequency to which the aerial is tuned, said aerial having substantially a cylindrical form for a substantial portion of its length which tapers into substantially a conical form whose apex is connected to said feeder, the diameter of said aerial being such that the ratio between the open-ended impedance of the aerial and the characteristic impedance of said feeder is not greater than 4:1.

4. A high frequency signal receiving system comprising in combination signal receiving apparatus, a feeder and an aerial connected with said receiving apparatus by said feeder, said aerial having an electrical length equal to an integral number of half wavelengths of the carrier frequency to which the aerial is tuned, said aerial having substantially a cylindrical form for a substantial portion of its length which tapers into substantially a conical form whose apex is connected to saidfeedenthe diameter of said aerial being such that the ratio between the open-ended impedance of the aerial and the characteristic impedance of said feeder is not greater than 4:1.

5. An aerial having a feeder connected thereto, said aerial having an electrical length equal to an integral number of half wavelengths of the carrier frequency to which the aerial is tuned, the physical dimensions of said aerial being such that the ratio between the open-ended impedance of the aerial and the characteristic impedance of said feeder is not greater than 4:1, said aerial having a diameter such that the relation is at least approximately true, where ZOA is the characteristic impedance of the aerial at the frequency of the carrier wave radiated, r is a resistance which represents the series radiation resistance of the aerial, assumed to be concentrated at the centre thereof, and ZOF is the characteristic impedance of the said feeder or other circuit at the frequency of the carrier wave radiated.

6. A short wave aerial according to claim 1 and composed of a group of parallel wires arranged in the form of a cylinder.

7. An aerial system for the transmission or reception of a wide band of short waves, comprising an aerial having connected thereto a feeder, said aerial having a diameter such that the relation EW G is approximately true, where ZOA is the characteristic impedance of the aerial at the frequency of the carrier wave tobe radiated or received, 7' is the resistance which represents the series resistance of the aerial, assumed to be concentrated at the center thereof, and ZOF is the characteristic impedance of said feeder at the frequency of said carrier wave.

8. An aerial system in accordance with claim 7, characterized in this that said feeder is a concentric feeder whose inner conductor is connected to one end of said aerial and whose outer conductor is. effectively grounded for the operating frequency at theend adjacent said one end of said aerial.

9. An aerial system for the transmission or reception of a wide band of short waves, comprising an aerial having connected to one end thereof a section of. concentric transmission line, the inner conductor of said concentric line being connected to said aerial, the lower portion of said aerial which connects with said inner conductor being in the form of a cone, said aerial having a diameter such that the relation ZoA '\/7Z is approximately true, where ZOA is the characteristic impedance of. theaerial at the frequency of the carrier wave to be radiated or received, 1' is the resistance whichrepresents the series resistances ofthe aerial, assumed to be concentrated at the centerthereof, aHdZOF is the characteristic impedance of said feeder at the fre-. quency of said carrier wave, and means for effectively grounding the outer conductor of said line for the working frequency.

10,.An aerial system for the transmission or reception of a wide band of short waves, comprising anaerial having connected to one end thereof a section of concentric transmission line, the inner conductor of said concentric line being on e said a r a t em rat f.

said aerial which connects with said inner conductor being in the form of a cone,said aerial having a diameter such that the relation is approximately true, where Z0; is the characteristic impedance of the aerial at the frequency of the carrier wave to be radiated or received, r is the resistance which represents the series resistance of the aerial, assumed to be concentrated at the center thereof, and ZOF is the characteristic impedance of said feeder at the frequency of said carrier wave, and a half wave conductor connected at its center to the end of the outer conductor adjacent said aerial for effectively grounding said outer conductor for the workin frequency. a

11. An aerial system for the transmission or reception of a wide band of short waves, comprising a circular cylindrical aerial having a feeder connected thereto, said aerial having a diameter such that the relation Z0A= 1Og107r d 0.25 is approximately true, where ZOA is the characteristic impedance of the aerial at the frequency of the carrier wave to be radiated or received,

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