Ground-plane antenna

The invention relates to a horizontal polarization antenna with vertical quarter-wave radiator, with improved functional parameters, intended for use in radio communication 'technique'. 5

Antennas with horizontal polarization, with radiant, quarter wave, vertical elements are known, especially for the frequency range between 20 and 200 MHz.

These antennas usually have the radiating element isolated from the ground, in direct current and alternating current, this execution, presenting 'the disadvantages of the tendency of electrostatic charge, of a weak protection for the emission or recapture apparatus against 15 the atmospheric electric discharges, as well as the difficulties in achieving the basic insulators with good dielectric and mechanical properties.

On the other hand, the use of 20 dipole antennas, although it allows the grounding of the radiant element to be grounded in direct current, due to the difference of an order of magnitude between the antenna length and the distance between the two parallel conductors, the protection against ²⁵the electrical discharges remain insufficient.

It is also known the solution of the direct current connection to the ground of the antenna. Through a short-circuit line in the quarter of ³⁰wave. and

The known antennas with horizontal polarization with vertical radiator in the fourth quarter also have the disadvantage of the limited possibilities of widening the band of working frequencies up to relative values ​​of 5 ... 10-%. on the path of increasing the diameter of the radiant clement, known as the .logarithmic relation between the realized band and the used diameter.

The invention removes the disadvantages of the above, in that, in order to obtain an increased bandwidth, without excessive enlargement of the radiator diameter, superior mechanical strength and better protection against atmospheric electric discharges, it provides for the use as a vertical radiant element of a conductive cylindrical tube having a length approximately equal to one quarter of the wavelength, positioned above of the vertical plane of the earth, a tube in which a central earthen rod is placed, having a short-circuit element, forming with the inner cylindrical wall of the radiating element a line in the short circuit coupled with a line. empty located below the vertical plane of the earth. the resulting combined line having the electrical length of about a quarter of a wave, being coupled in parallel with the antenna terminals and having as effect compensating the antenna susceptibility and providing a favorable stationary wave ratio for a wide range: 84948

PRICE LEI 10.27 dc frequencies, the lower end of the tubular radiant element being connected both the hot wire of the coaxial connection line and the radiocommunication equipment, as well as with the central conductor of the empty line made and, preferably, from the coaxial cable, the length electric of the combined line composed of the short circuit line and the empty line being able to be located within a tolerance range of ± 25% around the quarter wavelength.

The following is an example of embodiment of the invention in connection with FIG. 1 .., 3, which represents:

FIG. I, principle diagram of the antenna;

FIG. 2, side view of the antenna;

FIG. 3, the curve of variation of the stationary wave ratio according to frequency.

The horizontal polarization antenna shown in FIG. 1 is made of a vertical radiant clamp 1, made of a metal tube with the length approximately equal to the quarter wavelength, positioned above the virtual ground plane 2, created by the effect of four counterweighted conductors 3 inclined and with dimensions close to the length a quarter of a wave.

The antenna has a pair of terminals 4 and 5 of which the terminal 4 is connected to the lower (hot) end of the radiant element 1, to the central conductor of the coupling cable 6 and to the central conductor of the empty line 7, and the terminal 5 is connected to the grounding plane, on the outer screen of the hollow line 7 and at the lower end of the central rod, of earthing 8 placed inside the radiating tubular element 1.

The upper end of the earthing rod 8 'is coupled through a short piece 9, with the inner wall of the radiating element 1.

The central earthing rod 8 together with the shorting element 9 and the interior of the radiating element 1 forms a line in the short circuit shorter than a quarter wave, against which the blank line 7, made from. coaxial cable, is an extension, the combination of the two lines can be considered as a single line, in short at one end and in, empty. take the other one, with a branching at the level of the plane.

At these branch points, the combined line has a pure susceptibility that adds sc to the reactive component of the antenna admittance. The frequency of the line in the branching points changes with the frequency, the gradient of this variation depending on the position of the branching point on the combined line, while the susceptibility size depends on the total length of the line and the parasitic capacity of the antenna base.

The length of the combined line is close to the quarter wave, remaining constant, the relative position of the branch points being adjustable by simultaneously modifying the position of the short-circuit element 9 and the length of the line in the gap 7. Thus, by the positional adjustment of the branch points, the compensation, by the combined line susceptibility, of the variations of the reactive components of the antenna impedance, over a relatively wide frequency band and with the establishment of a favorable stationary wave ratio.

The combined line also provides a galvanic connection between the radiant element 1 and the ground, thus eliminating the electrostatic charge of the antenna, and placing the earthen rod 8 inside the radiant clement limits the destructive effects of a possible atmospheric discharge.

The antenna, according to the embodiment, has as constructive elements (fig. 2 - side view) a metal support 10 in which the inclined counterweight 3 rods 3 are fixed by threading. On the support a metal disc 11 is connected electrically connected to the lower end of the earthing rod 8 and isolated, by means of the spacer bush 12, made of dielectric material with respect to the radiant element 1.

The insulating support bush 13, placed at the top of the cylindrical orifice practiced in the support 10, constitutes the fixing piece of the radiant element 1 on an hour. constructive form replacing the bending moments with compression demands where the used insulating materials better resist. This mode of fixing the radiant element, with increased mechanical resistance, can be used because the increased parasitic capacities involved in this case are compensated by the effect of the combined line susceptibility. The shields of the empty line cables 7 and of the power supply 6 are connected to the disc 11 through the clamps 14a and 14b, the central conductors being connected by the clamp 15 at the lower end of the radiant element 1,

A connector 16 allows connection and disconnection of the power cord 19.

The free lower end of the blank line 7 is protected by the rubber sleeve 17.

A spacer disk 18, fixed to the radiant element 1, placed above the insulating support bush 13, provides a sufficiently long path to the antenna support 10, and, by means of a recess, a protection against electrical discharges.

A watertight sleeve 19 protects the space above the metal disc 11 from water infiltration, and a cap 20 closes the upper end of the tubular radiant member 1. in FIG. 3 shows the curve of the variation of the stationary wave ratio as a function of frequency, in the case of an antenna constructed as in the present embodiment, intended for use in the 33 -.- 38 MHz dc band,

84948 '..... 5' resulting in a better stationary wave ratio dc 1.5 in a 5 MHz band, so a relative band of 14%.

The antenna with horizontal polarization according to the invention has the following advantages:

- widens the increased frequency band without using a large diameter radiator;

- possibility to make a 1θ construction with high mechanical resistance to wind or ice deposits;

- - better protection against atmospheric electric discharges.