US2267446A - Aerial and feeder system - Google Patents

Description

Dec. 23, 1941. E c, CORK AL 2,267,446

AERIAL AND FEEDER SYSTEM Filed June 18, 1958 I To EDWARD 050/: c

ATTORNEY.

Patented Dec. 23, 1941 2,267,446 AERIAL AND FEEDER SYSTEM Edward Cecil Cork, Ealing, London, and Joseph Lade Pawsey, Hillingdon, England, assignors to Electric &' Musical Industries Limited, a British company Application June 18, 1938, Serial No. 214,437 In Great Britain June 23, 1937 10 Claims. (01. 178- 44) v This invention relates to aerials and feeder systems, and has particular reference to such systems in which an aerial is connected with a concentric feeder of the kind having one or more conductors surrounded by an outer conducting sheath. The invention is concerned with the suppression of undesired waves on the outside of the outer conducting sh'eath. In the specification of British Patent No. 438,506, alternative methods of suppressing 'waves are described which are applicable particularly to balanced aerials, the case of a center fed dipole aerial being described in the specification. A feature common to the methods described in the patent is the provision of an auxiliary conductor one quarter of a wavelength long. and constituted by a wire or hollow conductor similar to the outer conducting sheath. The drawings attach'edto the patent referred to show'an auxiliary conductor connected to the aerial end'of the feeder and bent to lie parallel with the feeder, one of the dipole conductors being connectedto the outer conducting sheath and the other dipole conductor being connected to the centralv conductor and also to the auxiliary conductor. I Alternatively, one of the dipole. conductors is con:

nected directly to the central conductor and theother dipole conductor is connected to the outer sheath and auxiliary conductor. 1 In the case of unbalanced aerial systems such,

for example, as a bottom fed dipole aerial, a

known method for reducing the effect of waves travelling up the feederconsists in the provision of two quarter" wavelength conductors con: nected to the outer sheath at the aerial end and extending on opposite sides of the feeder. The reduction-may be enhanced by the provision of two further quarterwavelength conductors arranged at right angles to the first pair, but spaced a distance such as one quarter of a wavelength from the aerial end of the feeder. These quarter wavelength conductors operateto reduce the impedance to earth from the points at which they are connected, to a value much lower than that of the aerial, and any wave travelling up, the feeder is. considerably attenuated.

The object of the present invention is to provide means for effecting further attenuation of undesired waves on the outside of the feeder than is produced by the known methods outlined.

According to the presentinvention high frequency signalling apparatus includes a main conductor providing a transmission path for signals and subject to the transmission of-undesiredsignals along the outside thereof attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals, by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said main conductor at a point which is at a given length from the end of said main conductor, said auxiliary conductor being of effective length including said given length and an additional length such that phase reversal of the. undesired signals occurs insaid auxiliary conductor with resultant substantial cancellation thereof at the end of the said main conductor. In particular apparatus to which the invention is applied, the auxiliary conductor is connected to a point in the main conductor one quarter of a wavelength of the desired signal frequency from the end of the main conductor. In an aerial and feeder system to which the invention is applied, the length of the auxiliary conductor includes a fraction of the order of one quarter of the wavelength of the desired signal frequency and an additional length substantially equal to one half of said Wavelength. An auxiliary. conductor provided in accordance withthe invention may be used in conjunction with a pair of quarter Wavelength conductors extending on opposite sides of a concentric feeder from the end of the feeder and a similar pair of quarter wavelength conductors arranged at right angles to the first and connected to the feeder at the point at which the auxiliary conductor is connected thereto, The auxiliary conductor may be bent to lie in a plane on one side only of the concentric feeder or it may be bent to form a zig-zag path having its axis constituted by the concentric feeder but shaped so as not to make contact with the feeder except at its end and at the point of connection.

In order that the invention may be more clearly understood and readily carried into effect alternative conductor systems embodying the invention will now be described by way of example and with reference to the accompanying drawings in which:

Figures 1, 2 and 3 show three such alternative forms. 1

Referring to Figure 1 of the drawing, an aerial l is fed by a concentric feeder 2 and at the end A of the feeder quarter wavelength conductors 3 and 4 are connected to the feeder and extend on opposite sides as shown. At a point B distant by the length 1 from the end of the feeder, two further quarter wavelength conductors .5 and 6 are arranged at rightanglesto the conductors 3 and 4. Th'ese conductors operate to reduce the impedance from the points A and B to earth, so that any wave travelling up the feeder 2 to the aerial is considerably attenuated. Actually these quarter wavelength conductors, together with the portion of the feeder between them, are equivalent to a band stop filter consisting. of a tuned circuit with a shunt path to earth at each' end, the shunt paths each consisting of inductance and capacity in series.

A conductor '1 of length l+ \/2 is bent to the shape shown in Figure 1 and connected at the points A and B, A being the operating wavelength.

The principle underlying the use of the additional length of feeder is that waves passing up the feeder will divide at the point B and in consequence of the extra half wavelength, the wave taking the path B, C, A will be in anti-phase at A to that going direct from B to A. Hence suppression of the Wave will occur; An alternative method of regarding the problem is to consider that the auxiliary conductor 1 forms with the original conductor 2 a parallel tuned circuit so that there is a high impedance between A and B. The two pairs of conductors 3, 4 and 5, 6 at the points A and B provide additional attenuation.

It may be found that the presence of the additional conductor 1 gives rise to distortion of the directional diagram of the aerial, due to the mutual coupling between the conductor 1 and the aerial. Such distortion can largely be overcome by the provision of a conductor similar to the conductor 1 arranged on the opposite side of the feeder 2.

An alternative arrangement is shown in Figure 2 of the drawing in which the extra half wavelength of auxiliary conductor has been included by making the auxiliary conductor of zig-zag shape. It will be understood that the auxiliary conductor 1 in this case is connected to the main conductor 2 only at the points A and B, sufficient space being left between the auxiliary conductor and main conductor at the points at which they are in proximity to keep the capacity so introduced as low as possible. The arrangement shown in Figure 2 has the effect of reducing the mutual coupling between the auxiliary conductor I and the aerial so preventing distortion of the directional'diagram of the aerial. The conductors 3, 4 and 5, B are shown arranged in the same plane in Figure-2 instead of at right angles as in Figure 1. It is desirable that these conductors should be at a substantial angle to each other or to adjacent projecting conductors, but owing to the particular shape of the auxiliary conductor 1, it is preferable to arrange them in the same plane instead of at right angles.

Fi ure 3 shows a further constructional form of an auxiliary conductor which is, in this case, arranged as a helix about the end of the feeder. The helix in this case has somewhat similar properties to the zig-zag conductor shown in Figure 2, but the conductors 3, 4 and 5, B are arranged at right angles to each other as in Figure 1.

While the expression Z+ \/2 has been used to indicate the length of the auxiliary conductor it is to be understood that the extra length of the auxiliary conductor beyond the length l is not necessarily an exact physical half Wavelength in air, but may be modified by the disposition of the conductor and its length may have to be adjusted experimentally to produce the best cancellation of the waves it is desired to suppress.

The invention has been described in connection with a bottom fed aerial, but it will be understood that the invention may in general be applied to the attenuation of waves along the outside of any high frequency conductor. Thus, for example, it may be used in combination with any of the arrangements described in the specification of British Patent No. 438,506 in order to provide very high attenuation of the wave travelling up the feeder to a center fed dipole aerial.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is:

1. High frequency signalling apparatus including a main conductor providing a trans-mission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said main conductor at a point which is at a given length from the end of said main conductor, said auxiliary conductor being of effective length including said given length and an additional length such that phase reversal of the undesired signals occurs in said auxiliary conductor with resultant substantial cancellation thereof at the end of said main conductor, and further conductors connected to said main conductor at each end of said given length to provide shunt paths to earth at each end of said given length, said length being such as to provide with said shunt paths a band stop filter for said undesired signals.

2. High frequency signalling apparatus according to claim 1 wherein said auxiliary conductor is connected to a point in said main conductor which is of the order of one quarter of the wavelength of the desired signal frequency from the end of said main conductor.

3. High frequency signalling apparatus including a main conductor providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced Without substantially increasing the attenuation of desired signals by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said main conductor at a point which is at a distance equal to a quarter of the length of the operating wave from the end of said main conductor, said auxiliary conductor being of an effective length including said quarter Wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in such auxiliary conductor with resultant substantial cancellation thereof at the end of said main conductor, and further conductors connected to said main conductor at at least one end of said quarter wave length portion to provide shunt paths to earth for said undesired signals.

4. High frequency signalling apparatus including a main conductor providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said mainlconductor atla point which is'at a distance equal to a'quarter of the length'ofthe operating wave'from the end of said main conductor, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of: the undesired signals occurs in such auxiliary conductor with resultant substantial cancellation. thereof at the end of said main conductonand a pair of quarter wave conductors extending perpendicularly on opposite sides of said main conductor ateach point of connection of saidIaiixiIiarY 'cohductOr to said main conductor.

5. High frequency signalling apparatus including a main conductor providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said main conductor at a point which is at a distance equal to a quarter of the length of the operating wave from the end of said main conductor, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in such auxiliary conductor with resultant substantial cancellation thereof at the end of said main conductor and a pair of quarter wave conductors extending perpendicularly on opposite sides of said main conductor at each point of connection of said auxiliary conductor to said main conductor, one of said pairs of quarter wave conductors being in a plane at right angles to the other of said pairs. I I

6. High frequency signalling apparatus including a main conductor providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor one end of which is connected to the end of said main conductor and the other end of which is connected to said main conductor at a point which is at a distance equal to a quarter of the length of the operating wave from the end of said main conductor, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in such auxiliary conductor with resultant substantial cancellation thereof at the end of said main conductor and a pair of quarter wave conductors extending perpendicularly on opposite sides of said main conductor at each point of connection of said auxiliary conductor to said main conductor, one of said pairs of quarter wave conductors being in a plane at right angles to the other of said pairs, said auxiliary conductor being symmetrically disposed with respect to said main conductor.

7. High frequency signalling apparatus including a concentric feeder having an outer casing and inner conductor and providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for. such "undesired signals being introduced without substantially increasingtheattenuation of desiredflsignals by an auxiliary conductor, one end of which is connected to theend of saidcuter casingand the other end of which is'connected 'to' said outer casing at a point which is at a length equal to a quarter of the length of-the operating wave from the end of said outer casing, said auxiliary-conductor being of an eifective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in said auxiliary conductor with resultant substantial cancellation thereof at the end of said outer casing, and further conductors connected to said main conductor at at least one end of said quarter wave length portion to provide shunt paths to earth for said undesired signals.

8. High frequency signalling apparatus including a concentric feeder having an outer casing and inner conductor and providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor, one end of which is connected to the end of said outer casing and the other end of which is connected to said outer casing at a point which is at a length. equal to a quarter of the length of the operating wave from the end of said outer casing, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in said auxiliary conductor with resultant substantial cancellation thereof at the end of said outer casing, and a pair of quarter Wave conductors extending perpendicularly on opposite sides of said outer casing at each point of connection of said auxiliary conductor to said outer casing.

9, High frequency signalling apparatus including a concentric feeder having an outer casing and inner conductor and providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor, one end of which is connected to the end of said outer casing and the other end of which is connected to said outer casing at a point which is at a length equal to a quarter of the length of the operating wave from the end of said outer casing, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in said auxiliary conductor with resultant substantial cancellation thereof at the end of said outer casing, and a pair of quarter wave conductors extending perpendicularly on opposite sides of said outer casing at each point of connection of said auxiliary conductor to said outer casing, one of said pairs of quarter wave conductors being disposed in a plane at right angles to the other of said pairs of conductors.

10. High frequency signalling apparatus including a concentric feeder having an outer casing and inner conductor and providing a transmission path for signals and subject to the transmission of undesired signals along the outside thereof, attenuation for such undesired signals being introduced without substantially increasing the attenuation of desired signals by an auxiliary conductor, one end of which is connected to the end of said outer casing and the other end of which is connected to said outer casing at a point which is at a length equal to a quarter of the length of the operating wave from the end of said outer casing, said auxiliary conductor being of an effective length including said quarter wavelength and an additional length equal to a half the length of the operating wave whereby phase reversal of the undesired signals occurs in said auxiliary conductor with resultant substantial cancellation thereof at the end of said outer casing, and a pair of quarter wave conductors extending perpendicularly on opposite sides of said'outer casing at each point of connection of said auxiliary conductor to said outer casing, one of said pairs of quarter wave conductors bein disposed in a plane at right angles to the other of said pairs of conductors, said auxiliary conductor being coiled about said outer casing between its points of connection to said outer casing.

EDWARD CECIL CORK.

JOSEPH LADE PAWSEY.

Images