DE1043425B - Antenna feeder - Google Patents

Description

GERMAN

The invention relates to a feed device for an antenna of the reflector type, which over a wide Frequency band can be operated.

The invention allows sidh z. B. advantageous in connection use with antennas that are used in radio communications, the antenna both for Sending as well as receiving - on different frequencies over a broadband and even for simultaneous Transmitting and receiving on different frequencies within this band is applied. In the following description, the invention is with particular application to a parabolic reflector type antenna described in the ultra-high frequency band over an approximate range from 750 to 950 megahertz (a wavelength of about 30 to 40 cm) should operate although the invention is equally applicable to antennas for other frequency bands and for many more Purposes such as B. for frequency-keyed radar, are intended.

It will be readily understood by one skilled in the art that in achieving a acceptable impedance matching between the waveguide and the antenna causes significant problems occur to achieve a low standing wave ratio over a frequency band of such width (the total bandwidth of 200 megahertz is about 25% of the center frequency of 850 megahertz).

It is therefore one of the objects of the invention to provide a feed system which can be perfectly matched supplies to an antenna over a frequency band of said width; a system that too before all mechanically simple, well suited for commercial production and for running trouble-free Application to field conditions is.

According to the invention there is an antenna feed device created which is a piece of a waveguide with at least one opening therein for emitting radio frequency energy to and / or receiving radio frequency energy from a reflector type antenna and in which a first reactance is connected to the waveguide is electrically coupled to a point at which the admittance vectors of the feed device are measured at a plurality of frequencies over a wide frequency band, e.g. B. from 750 to 950 megahertz, are of the same general angular position and all susceptance components have one polarity, which is opposite to that of said reactance means, the first Reactance, of sufficient magnitude to contain all admittance vectors, measured after addition of the first reactance, reactance components of the same polarity as that of the first reactance antenna feed device

Applicant:

General Bronze Corporation,
Long Island, NY (V. St. A.)

Representative: Dipl.-Ing. H. Görtz, patent attorney,
Frankfurt / M., Schneckenhofstr. 27

Claimed priority:
V. St. v. America October 22, 1956

George J. Doundoulakis, Brooklyn, N.Y.,

and Ira Kamen, New York, N.Y. (V. St. A.),

have been named as inventors

Standes to give and in which a second reactance unites with the waveguide at one point that is spaced apart from the first reactance in a direction away from the opening and in such a distance that the admittance of the feed device, measured at this Point after adding the first reactance but before adding the second reactance, Conductance components of the general one standardized across the broad frequency band Order of magnitude 1, with the second reactance being sufficient to cover the reactance components to counteract the last-mentioned admittance values and measure these admittance values after adding the second reactance, into practically pure conductance values of a normalized value of the general order of magnitude 1, whereby the admittance of the feed device the characteristic admittance of the waveguide is adapted across the broad frequency band, to create a standing wave ratio close to 1.

Further features, advantages and possible applications of the invention can be seen from the illustrations of an exemplary embodiment as well as from the following description. It shows

1 is a schematic perspective view of a high frequency antenna of the parabolic reflector type; has the features of the invention,

2 shows a schematic plan view of one of the two flanges on a horn of the feed device according to Fig. 1,

«SS 678/237

3 4

Fig. 3 is a schematic longitudinal cross-sectional view are generally wedge-shaped, their »pointed

of the horn, tapered surfaces 41 are concavely curved

4 and 5 are cross-sectional views of the horn in the form of surfaces of a straight circular cylinder

long the lines 4-4 and 5-5 of Fig. 3 and coaxial with the opposite curved upper

6, 7 and 8 are Smith chart representations of the 5 surfaces 40. Thus, the concavely curved upper admittance coordinates of the feed device, the surfaces of the partition walls 42 measure equally in all points in different reference planes in the horn far from the convexly curved surfaces 40 in front and after adding a certain reactance, it is harvested. The tip 43 of the separators, which run along the elements, with Fig. 6 facing the complete Smith waveguide 26 backwards, halves the shorter Diagram and FIGS. 7 and 8 only the central part io dimension of the waveguide, the concave illustrate the same on an enlarged scale. Surfaces 41 practically tangential to each other and to

As can be seen from Fig. 1, the illustrative inner surface of the wall 34 of the horn light antenna according to the invention is parabolic, although as shown at 41a on each reflector 20 it is made of a suitable metal , Side cut away to facilitate assembly like sheet steel, and to facilitate assembly on a tower by supporting a movement of the. From the center of the parabolic surface 20, separating members through the waveguide 26 extend along their axis of symmetry, which is as possible. From the foregoing description of angular waveguides 22 to the front, mechanically it can be seen that the shorter dimension is each of the self-supporting. half of the outer end of the

The inner transverse dimensions of the waveguide 20, waveguide 26 or 38.1 mm, are sufficient to be able to transmit the particular frequencies occurring on the two inclined rear surfaces 36. In one example and 38 of the horn is a pair of flanges 44 facing antenna which are used to transmit frequencies that have rectangular openings 46 (see FIG. 2) on within the band from 750 to 950 megahertz, these openings If smooth continuations are suitable, the waveguide expediently has 25 of the two sections 30 and 32 of the horn, a larger internal transverse dimension (its width or the opened flanges with their divergent upper dimension) of 247.65 mm. On its inner surfaces 48 and SO serve as the radiating elements, end adjacent to the surface of the parabolic surface by means of which the radio frequency energy is directed against the 20, the waveguide expediently has a surface of the parabolic surface 20 (Fig. 1), shorter inner transverse dimension ( its height or 30 The inner surface of each of the two flanges 44 is abi> dimension) of 123.825 mm, which extends linearly to receive a dielectric plate, 76.2 mm at the outer end of the waveguide which is used to tapers the waveguide. This gives the waveguide a boundary wave-like seal and allows it to be pressure-tight with a length of 2 a = 49.5 cm, which corresponds to a frequency of, e.g. B. with dried air, corresponds approximately to 600 megahertz. 35 On each of the short sides of the openings 46 (like

At the outer end of the waveguide 22 is shown as a (in Fig. 3) the side walls 27 of the flanges

Composite radiating element a horn arrangement in the direction of the opening a short distance

attached, which is indicated generally at 24. wide beveled. This is used for lateral expansion

This horn arrangement is shown in detail in FIGS. 2 tion of the energy beam emitted from the opening

to 5 illustrated. As can best be seen from Fig. 3 40 and enables a more uniform irradiation of the

can be seen, the horn arrangement 24 has a parabolic surface 20. For the same purpose, the various

A length of waveguide 26 extends upwardly from the gent surfaces 48 and 50 of the flanges (as in FIG

an effective continuation of the main part 22 (Fig. 1) Fig. 2 illustrates) at their outer corners even-

of the waveguide forms, cut away in its shorter fall, to inclined surfaces 48 a

tapered measurement in a similar way and to leave the 45 and 50a free.

The end of the main waveguide is fitted around a. The openings 46 are somewhat chap-smooth in nature to form inner junction 27. That quoted in their admittance properties, in spite of the Horn 24 is provided with a flange 28, by means of the fact that the inward of their shorter whose beveled upper end protrudes with a similar flange on the outer side walls of the main waveguide 22 is connected. 50 surfaces 47 a certain amount of inductive reactive

The outer end of the horn 24 is inserted into the upper and lower conductance, which to some extent corresponds to the den

lower sections of the same size 30 and 32 on openings 46 inherent capacitive blind conductors

divided, whereby these two sections are counteracted by means of a value.

common front wall 34 and rear The separating members 42 expediently have

walls 36 and 38, which at an angle of 45 ° 55 have a width of 38.1 mm and are flush

with respect to the longitudinal axis of the waveguide, it closes at an incline with the shorter side walls of the

are limited. In the area in which the waveguide is arranged. This becomes a free one

two sections 30 and 32 in the waveguide 26 space between the inner surfaces of the

pass over, each of the two inner corners 40 is left free in both separators of 171.45 mm.

Rounded shape of a straight circular cylinder, whose 60 These dividing links not only lead into the circle

Axis parallel to the longer dimension of the shaft - a certain amount of complex admittance,

conductor is to ensure a smooth transition from the wave whose main component is capacitive susceptance

Head into the two sections 30 and 32 to yield. but also serve as supports for a couple in-

The main body of the horn is suitably ductile orifices 56 which are placed on each of the sections 30

formed from cast aluminum, the inner surfaces 65 and 32 of which of the horn are arranged,

are machined. As best illustrated in FIG. 3, extend

On the end wall 34 is adjacent to this diaphragm 56 from the convexly curved ones

two shorter side walls of the waveguide inner surfaces 40 of the horn from against dÄ "

a pair of separators 42 are attached having a concave curved tapered surface 41

have beak-tip shape, - that is, they 70 of the separating members 42 in a plane a in which the

Axis of the adjacent curved surface 40 lies. The outer edges of the panels which the Forming diaphragms 56 are, as best seen in FIG. 4, with the shorter side walls of the two Sections of the horn flush.

In one illustrative device, the bezels are made of sheet aluminum having a thickness of 3.63 mm and extend transversely into the conductor for a distance of 41.275 mm, being they leave a gap of 165.1mm between their edges. The diaphragms 56 lead into the System inductive reactance a. Their purpose is, generally speaking, the arrangement of the admittance cardiinates of the feed device, measured in the plane of the diaphragms, to reverse.

This effect can best be understood by referring to the Smith chart representations of admittance coordinates shown in FIGS. Fig. 6 illustrates in the area labeled A a plurality of susceptance coordinates, measured at different frequencies over the entire frequency band within which the feed device is to be used, the measurement being made in plane a (Fig. 3), which contains the diaphragms Take 56, but before adding the apertures. The small circles in group A, which represent the admittance coordinates corresponding to the various frequencies, are entered to indicate the frequencies which they represent accordingly and which extend from 750 to 950 megahertz in steps of approximately 30 megahertz. As can be easily understood from familiarity with these types of graphs, all of these admittance coordinates have capacitive susceptance components of the same order of magnitude, and the standing wave ratios measured over this frequency band are also of the same general order of magnitude. Thus, the admittance coordinates are tightly "clustered" over the entire frequency band. It is important that the apertures 56 are arranged sufficiently close to the openings 46 so that the admittance coordinates are not too far apart - in other words, so that their respective vectors are practically in phase.

As is well known, when the reference plane is moved back along the waveguide in a direction toward the generator and away from the load, the admittance coordinates, measured at various frequencies, move in a clockwise direction in a generally circular path, its The center is located approximately at 0 of the diagram, which represents a normalized admittance of 1 (ie an admittance equal to the characteristic admittance of the waveguide), the radius of the circle being equal to the reflection coefficient. The circles in the groups generally designated B represent the admittance coordinates, measured in an arbitrary reference plane & (Fig. 3), extending along the waveguide towards the generator for a distance away from the apertures 56 which is approximately a quarter wavelength , is kept at a distance.

The effect of shifting the reference plane is greater at the higher frequencies than at the lower frequencies because the distance by which the plane has been shifted is greater in relation to the wavelengths of the higher frequencies than to those of the lower frequencies. Thus, the admittance coordinates, measured at higher frequencies, move clockwise by a larger angle than do the coordinates, measured at lower frequencies. Thus, when the reference plane is shifted towards b , the admittance coordinates come to lie further apart in a generally curved line in which the high frequencies "lead" - that is, the coordinates, measured at the higher frequencies, are moved further forward than clockwise the coordinates measured at lower frequencies.

The addition of the apertures 56 and separators 42 (Fig. 2) has the composite effect of introducing inductive susceptibility values into the feed device of sufficient magnitude to give all admittance values, measured in plane a, across the entire frequency band, susceptance values components that are closer to are inductive than capacitive. This causes the susceptance coordinates, measured in plane b, to be shifted from the positions indicated at B in FIG. 6 to the positions illustrated at B ' in the enlarged-scale diagram according to FIG. 7. As can be seen, this shift has the effect of reversing the order of the corresponding coordinates so that the low frequency coordinates now "lead" in the clockwise direction.

If the reference plane is now shifted further back in the waveguide in the direction of the generator, all coordinates generally move in exactly one direction clockwise, around point 0 of the diagram, with the high-frequency coordinates moving at a greater angle than the low-frequency coordinates . Thus, a point can be found where the higher frequencies "catch up" with the lower frequencies. This effect is illustrated by the coordinates in the group labeled C in FIG. 7, which represent the admittance coordinates, measured in reference plane c (FIG. 3), across the frequency band.

The practical coincidence of the various coordinates shows that the susceptibility components of all coordinates are of approximately the same magnitude and that, as can be seen, all susceptibility components are positive in polarity, that is to say capitively. It should also be noted that the coordinate group C lies around the circular line 62, which corresponds to the conductance components with a normalized value 1, ie a value which is equal to the characteristic conductance of the waveguide.

As can be seen from FIGS. 3 and 5, an inductive diaphragm arrangement 58 is mounted in the waveguide in plane c , which has a pair of diaphragm plates 58a and 58 &, the outer edges of which correspond to the inner surfaces of the opposite short side walls of the waveguide 26 are flush. The diaphragm 48 introduces an inductive susceptance into the waveguide in plane c of sufficient magnitude to counteract the capacitive susceptance which is present at this point before the diaphragm is added. In the illustrated system to which previously referred, the two diaphragm plates 58 are α and each made of aluminum plate with a thickness of 3.18 mm 58, and extend into the waveguide 26 mm to a distance of 28.58 in, wherein they leave a 19.05 mm gap between their inner edges.

The purpose of introducing this inductive susceptance is to remove all admittance coordinates,

as illustrated in FIG. 8, in a counterclockwise direction along the circular line 62 in the direction of the reference line 63, which corresponds to the zero conductance. The inductive diaphragm 56 has a greater effect on the susceptance values measured at lower frequencies than on those measured at higher frequencies. Thus, the lower frequencies tend to move further towards the baseline than the higher frequencies. The inductive conductance value of the diaphragm 58 is of sufficient size to bring all the conductance value coordinates approximately into alignment with the reference line 63. Therefore, all admittance values, measured across the frequency band, are practically pure conductance values without any significant susceptibility components, and their conductance components have a normalized value in the order of magnitude 1 - that is, the admittance of the feed system, measured in level c, is 58 after the addition of the inductive diaphragm over the entire frequency band approximately equal to the characteristic admittance of the waveguide. This adaptation of the feed system admittance to the characteristic admittance of the waveguide results in the electrical effect of a waveguide of infinite length in which reflections are practically eliminated and a standing wave ratio of practically no greater than 1 is achieved. As can be seen from FIG. 8, a circle drawn around the origin 0, which corresponds to the characteristic admittance of the waveguide, with a radius which corresponds to a standing wave ratio of 1.2, comprises all admittance coordinates of the feed system measured over the entire frequency band .

Problems arise with many antennas, particularly those of the parabolic reflector type of reflections from the parabolic surface back into the openings of the radiating horn. This reflected Energy creates standing waves on the line and has an adverse effect in context with the intelligibility of the signal - e.g. B. it can create a "ghost image" in a television signal or distort a radio teletype signal. These problems were addressed by applying a pair of Reflector plates 64 and 66 (Fig. 1) overcome. These plates are made of aluminum sheet; their front surfaces are practically flat for ease of manufacture, and they are cut out in a circular shape. on the parabolic surface 20 they are supported by arms 68 which support the plates so that the Surface in the center of each plate practically perpendicular (normal) to one of the focus of the parabolic surface 20 intersecting line. A very precise setting can be made in such positions, by the maximum energy radiation from the reflector plates 64 and 66 back into the openings 46 of the horn 24 to reach. The space between the reflector plates in front of the parabolic surface 20 is such adjusted so that the energy reflected from the plates 64, 66 back into the openings 46 is 180 ° out of phase with respect to the integrated reflected back into the openings 46 by means of the parabolic surface 20 Energy is, and the size of the plates 64, 66 is chosen so that the amount of these plates reflected energy equal to the amount reflected from the parabolic surface 20 into the openings 46 Energy is.

For a typical antenna to be used in the aforementioned frequency range, show the reflector plates when using a parabolic reflector with a diameter of 9.14 m for a Focus 2.74 m from the center of the front surface of the parabolic surface. Diameter of 568.3 mm and are with their inner edges 282.08 mm away from the axis of the parabolic surface and 65.09 mm arranged in front of the parabolic surface, wherein they are tilted inward so that their outer edges 95.25 mm from their inner edges.

Since the energy reflected from plates 64 and 66 is equal and opposite to that of the Parabolic surface 20 is reflected energy in the openings 46, it acts under the influence of the latter, exactly opposite. Thus the total reflection is 0 and the standing wave ratio of the system remains practically 1.

It will therefore be understood that the disclosed feed device provides excellent impedance matching between the antenna and the waveguide over the entire frequency range for which the system is intended is, creates.

The particular embodiment of the invention illustrated and described herein serves only as a convenience Example and is not intended to limit the invention.

Claims (6)

Patent claims: 1. Antenna feed device comprising a piece of waveguide with at least one opening therein for emitting radio frequency energy and / or for receiving radio frequency energy from a reflector-type antenna, characterized in that a first reactance is electrically coupled to the waveguide at one point, at which the admittance vectors of the feed device, measured at a plurality of frequencies over a wide frequency band, e.g. From 750 to 950 megahertz, are of the same general angular position and all reactance components have a polarity which is opposite to that of the first reactance, the first reactance being of sufficient size to cover all of the admittance vectors, measured after the addition of the first reactance, reactance components the same polarity as that of the first reactance, and that a second reactance is associated with the waveguide at a point spatially remote from the first reactance in a direction away from the opening and at such a distance that the admittances of the feed device , measured at this point after adding the first reactance, but before adding the second reactance across the broad frequency band, have normalized conductance components of the general order of magnitude 1, the second reactance being sufficient to reduce the Bl to counteract the inductance components of the last-mentioned admittance values and to convert these admittance values, measured after adding the second reactance, into practically pure conductivity values of a normalized value of the general magnitude of 1, whereby the admittance of the feed device is adapted to the characteristic admittance of the waveguide across the broad frequency band, a standing wave ratio to create nearly the first 2. Apparatus according to claim 1, characterized in that the first reactance of is inductive in nature, so that the susceptance components of the admittance vectors are measured in the absence of the first reactance, of capacitive and, measured after the addition of the first reactance, are inductive in nature, the second reactance also is of an inductive nature, so that the susceptibility components of the admittance vectors are measured in the absence of the second reactance, are of a capacitive nature. 3. Device according to claims 1 and 2, wherein the waveguide has a rectangular cross section and the antenna is parabolic, characterized in that the radiating and / or receiving The end of the waveguide is divided into two sections of the same size at its shorter dimension is, with each section having a rearward opening approximately in focus of the Having an antenna and wherein the first reactance further comprises a pair of inductive shutters, one of which is arranged in each section, while the second reactance has another Has inductive aperture. 4. Apparatus according to claim 3, characterized in that the inductive diaphragm in each Section has a pair of diaphragm plates extending from opposite short side walls of the portion between a pair of partition members and an inner wall of the Extend section, wherein the separating members of opposite short side walls of the Waveguide protrude, where the waveguide is divided into its sections and has tips, pointing in a rearward direction along the waveguide and the short dimension of the Waveguide practically split in two, the tapered surfaces of the separating members being concave are curved about axes which are also the axes of the straight circular cylinders, the convexly curved ones Surfaces form the inner walls of the sections. 5. Device according to claims 3 and 4, characterized in that the tendency to reflection integrated energy back into the openings by means of the antenna during transmission through into the openings by means of a pair of reflector plates that are on opposite sides Sides of the waveguide are placed in front of the antenna, reflected energy is eliminated. 6. Apparatus according to claim 5, characterized in that the plates with their front surfaces are oriented practically perpendicular to imaginary lines extending from the openings extend to the centers of the plates, and that the distance of the plates from the openings and the size of the plates is such that the energy reflected by the plates is practically 180 ° out of phase with the integrated reflected energy and the same magnitude as this having. For this purpose 2 sheets of drawings © «». 673/237 11.58