US2202368A - Loop antenna - Google Patents

Description

w. BERNDT 2,202,368

} LOOP ANTENNA Filed Nov. 11, 1937 May 28, 1940. I

INVENTOR WAL TER a IQ/V07 ATTORN EY ill ' shielding means or with the casing R, the an tenna effect may be cut down to a very low value.

Patented May 28, 1940 LOOP ANTENNA Walter Berndt, Berlin, Germany, assignor to Telefunken Gesellschaft fiir .Drahtlose Telegraphic in. b. 11., Berlin, Germany, a corporation of Germany Application November 11, 1937, Serial No. 173,992 In Germany October}, 1936 t 5'Claims.- (01. 250-33) 1 This invention relates to a frame or loop antenna arrangement possessing only a small antenna effect.

It is known in the art that the direction diagrams or characteristics of loops or frames correspond to the calculated values only when it is possible to eliminate the antenna effect of the loop. Several ways and means have been disclosed in the earlier art to this end. The loop and the input circuit may be built symmetrically. The loop may be shielded electrically; the leads brought-to the loop maybe grounded through difierential condensers, while the antenna effect I finally may be compensated by an auxiliary antenna. Yet, in spite of all these steps an appreciable antenna effect will be found to be present, and it will always be compensated by the last-named means, namely, an auxiliary antenna. The requisite auxiliary antenna must possess a certain efiective minimum size if its action is to be attainable in an adequate measure. ever, it is often undesirable or inconvenient to use a large auxiliary antenna. For this reason it is desirable to design a loop antenna having inherently a low antenna effect.

The antenna effect" of a loop of known construction is essentially due to capacitive dissymmetries to ground or casing of the two halves thereof. Another part of the antenna efiect is due to the leads brought to the loop which, in most cases, are coupled with a circuit presenting a dissymmetric relation to ground.

Referring, now, to the drawing, Fig. 1 shows one form of my invention, while Figs. 2 and 3 show modifications thereof. I

According to this invention, therefore, a loop is used which is not furnished with any direct supply leads or downleads and which consists of one or several turns L closed upon themselves; The

connection with the receiver apparatus, as shown in Fig. 1, is established bymeans of a coil W annularly surrounding the turner the turnsof the loop. However, also two symmetrically mounted coils W, W may be employed as shown in Fig. 2. By means of static shielding of the annular coil or coils as shown in more detail in Figure 3, and connection with ground of the A further reduction in the antenna-effect is attainable by grounding the loop antenna L-or connecting it with the casing R in a symmetrical manner. The grounding point of the loop turns will then'be symmetrical to the annular coils (Fig, 2') or to the annular coil (Fig. 3).

- nular coil.

The, annular coils are included suitablyin a tuned circuit which acts upon the grid of ,a tube (Fig. 2). Ifas close a coupling as possible is to be insured between the loop and the grid circuit,

then the core of the annular coil may consist of.

iron or of a material containing low-loss iron K, asshown in Fig. 3.

By the use of two similar annular coils which.

are placedupon both sides of the grounding point of the loop, theloop arrangement is made of symmetric construction. 7 l

If the loop antenna is .used for pickingup a wide wave band, then it will be expedientto; provide the annular coil with several convolutions which are tapped or reversed, it being understood, of course, that for each wave band-distinct annularcoils could be employed.

To obtainspecial directional effects the loop antenna, of this invention 'whichinheres no antenna effect at all or only a very small one,.

could be combined with one or several like or similar antennae; and the same could then be used either for reception or for transmission.

Referring to Fig. 3, R. denotes the loop casing which acts also as a shield for the convolutions L and W the winding while S indicates a shield for the winding W. o By the ground terminal indicated at E, the convolutions ofvthe loop are in referenceto .the an-' earthed symmetrically I claim:

1. Loop antenna comprising convolutions, saidconvolutions being closed upon themselves to form a closed circuit, means for coupling said loop to a receiver comprising coils annularly surrounding the-loop convolutions and means for shielding said loop convolutions including a casing surrounding said convolutions and connected to the convolutions at the center of the portion surrounded by said coupling means.

2. A loop antenna comprising one or more con volutions said loop convolutions beirig closed upon themselves to form aclosed circuit, means for coupling said loop to ,a receiver comprising a coil annularly surrounding the loop convolutions and means for electrostatically shielding saidcoil surrounding said coil and connected to ground at a point intermediate the ends thereof.

3. Loop antenna comprising convolutions, said convolutions being closed upon themselves to .form a closed, circuit, means for coupling said I loop to a receiver comprising a coil annularly sur- I rounding the loop convolutions and means for,

shielding said loop convolutions including a casing'surrounding said convolutions and connected to the convolutions at the center of the portion surrounded by said coupling means.

4. Loop antenna comprising a convolution, said convolution being closed upon itself, to form a closed circuit, means for coupling said loop to a receiver comprising coils annularly surrounding the loop convolution and means for shielding said loop convolution including a casing surrounding said convolution and connected to the convolution at the center of the portion surrounded by said coupling means.

5. Loop antenna comprising a convolution, said convolution being closed upon itself, to form a. closed circuit, means for coupling said loop to a receiver comprising a coil annularly surrounding the loop convolution and means for shielding said loop convolution including a casing surrounding said convolution and connected to the convolution at the center of the portion sur- WALTER BERNDT.

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