US2315170A

US2315170A - Transmitting or receiving device comprising a dipole antenna

Info

Publication number: US2315170A
Application number: US427554A
Authority: US
Inventors: Adelbert Van Weel
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-08-01
Filing date: 1942-01-21
Publication date: 1943-03-30
Anticipated expiration: 1960-03-30
Also published as: GB553636A; FR874350A

Abstract

553,636. Wireless receiving and transmitting circuits. PHILIPS LAMPS, Ltd. (Naamlooze Vennootschap Philips' Gloeilampenfabrieken). Nov. 26, 1941, No. 15247. [Class 40 (v)] A circuit for coupling a dipole antenna 4 to a transmission line connected to terminals 1, 2, with or without a transformer 8, so as to ensure correct matching over a wide frequency band, comprises a resistance in two parts 5, 6 which together equal the radiation resistance of the antenna, tapped on to a resonant circuit 7 tuned to the natural frequency of the antenna 4. The tappings are chosen so as to include an inductance which is equal to the capacity of the antenna multiplied by the square of the radiation resistance. With these conditions the arrangement presents at the terminals 1, 2 an impedance which is a pure resistance equal to the radiation resistance of the antenna over a wide band of frequencies.

Description

March 30, 1943.

TRANSMITT I NG OR. RECEIVING DEVICE COMPRISING DIPGLE ANTENNAS Filed Jan. 21, 1942 Jim 1 L [55- 55. At] N V'VV' INVENTOR ATTORNEY Patented Mar. 30, 1943 TRAN SlVIITTIN G OR RECEIVING DEVICE COMPRISING A DIPOLE ANTENNA Adelbcrt van Weel, Eindhoven, Netherlands; vested in the Alien Property Custodian Application January 21, 1942, Serial No. 427,554 In the Netherlands August 1, 1940 2 Claims.

This invention relates to a device for transmitting electric oscillations by means of a dipole antenna that through a transmission lead can be connected to a high frequency energy transducer such as transmitter or receiver and is particularly useful when a wide frequency band is to be transmitted by the antenna, for example for television purposes.

The object of the invention consists in ensuring correct matching of the dipole antenna to the transmission lead throughout a wide frequency band.

According to the invention, for this purpose the conductors which connect the dipole antenna, in some cases through a transformer, to the transmission lead have arranged between them the series combination of an ohmic resistance equal to the radiation resistance of the antenna and a parallel resonance circuit which is tuned to the natural frequency of the antenna and whose effective inductance is equal to the capacity of the antenna multiplied by the square of the radiation resistance.

In order that the invention may be clearly understood and readily carried into effect it will now be described more fully with reference to the accompanying drawing, wherein Figur 1 shows a substitution diagram of an antenna system in which is embodied the present invention and Figure 2 shows a modification thereof.

Referring to Figure l, the inductance L, the capacity C and the resistance R constitute the substitution diagram of a dipole antenna since a dipole antenna behaves as regards frequencies adjacent the resonance frequency as a series rescnance circuit. Via the terminals l and 2 the dipole antenna may be connected to a transmission lead 3, a transformer being inserted, if necessary, in order to match the wave resistance of the lead to the radiation resistance R of the antenna.

It is obvious that correct matching is only possible in connection with those frequencies with which the impedance of the antenna is approximately real, that is to say, only in connection with a comparatively narrow frequency band immediately adjacent the resonance frequency of the antenna correct matching will be ensured.

According to the invention, in order to enable matching in a wide frequency band the conduc tors which connect the antenna to the terminals I and 2 have connected between them a network comprising the series combination of an ohmic resistance R1 and a parallel resonance circuit L1C1.

If the conditions are satisfied a pure real impedance the value of which is R is measured between the terminals l and 2 as viewed from the lead 3 for any frequencies.

The value of the inductance L1 derived from the above conditions is in practice frequently too low for an efficient construction of the oscillatory circuit LlCl. This difficulty may be obviated by constructing the oscillatory circuit so as to have a higher inductance and by connecting the resistance R1 to a tapping of the circuit. In this case, the effective inductance of the oscillatory circuit is to be understood to mean the inductance of the transformed oscillatory circuit which appears to occur in series with the resistance R1.

From the point of view of symmetry it is preferable to split up the resistance R1 into two equal parts which are arranged on either side of the oscillatory circuit.

An embodiment of the invention, modified as suggested above, is shown in Figure 2. In this case, a dipole antenna 4 is connected through a transformer 8 to the terminals 1 and 2 to which a transmission lead can be connected, the transformer 8 serving for matching the radiation resistance of the antenna 4 to the wave resistance of the transmission lead.

The conductors which connect the antenna to the primary of the transformer 8 have arranged between them two .equal resistances 5 and 6 which jointly are equivalent to the radiation resistance of the antenna and whose adjacent ends are connected to two tappings of an oscillatory circuit 1 symmetrically arranged relatively to the midpoint. The circuit I is tuned to the natural frequency of the antenna 4 and the inductance of the transformed oscillatory circuit that appears to occur between the two tappings is equal to the capacity of the antenna multiplied by the square of the radiation resistance.

Between the terminals l and 2 a constant and real impedance is measured throughout a wide frequency band on either side of the natural frequency of the antenna.

It may be observed that the ratio between the antenna-E. M. F. and the voltage occurring between the terminals l and 2 still depends on the frequency. This frequency relation may be annulled if desired by a suitable choice of the frequency characteristic of the transmitter or receiver. &

I claim:

1. In an antenna system, an antenna and high frequency transducer means coupled to terminals of said antenna, a circuit including a capacity and an inductance connected in parallel and tuned to the operating frequency of said antenna, tapping points on said inductance including less than all of said inductance therebetween so located that the reactance between said tapping points is numerically equal to the product of the capacity of said antenna and the square of the radiation resistance of the antenna, and a series circuit including an ohmic resistance equal to the radiation resistance of said antenna and the portion of said inductance between said tapping points connected across the terminals of said antenna.

2. In an antenna system, an antenna and high frequency transducer means coupled to terminals of said antenna, a circuit including a capacity and an inductance connected in parallel and tuned to the operating frequency of said antenna, tapping points on said inductance including less than all of said inductance therebetweenso located that the reactance between said tapping-'points is numerically equal to the product of the capacity of said antenna and the square of the radiation resistance of the antenna, and a series circuit including an ohmic resistance equal to the radiation resistance of said antenna and the portion of said inductance between said tapping points connected across the terminals of said antenna, said ohmic resistance being split into two equal parts, one connected to each inductance tapping point.

ADELBERT VAN WEEL.