DE19540880A1 - Shortened closed loop antenna using coaxial trap principle - Google Patents

Abstract

The antenna is serially fed by adaptor elements. The cable capacitance of the coaxial cable which is used, can be tuned by means of a series additional capacitance around the cable. The capacitance is tuned so that with the inductance value of the geometric surface covered by the cable flex, the desired resonance is achieved. The capacitive elements for tuning to resonance preferably include two or more metal tubes with good metallic contact. The tubes are preferably provided with threads for fine adjustment. Two or more cable rings may be used to achieve the desired capacitive reduction. The ring may be spread or partly spread to vary the inductance.

Description

Horizontal and also vertical antennas are due to their mechanical ab measurements resonant only for a certain frequency. Should these antennas used for lower frequencies, they must be extended electrically will. This is accomplished by turning on extension inductors. This causes the antenna to become narrower because the L-C ratio changes shifts. The capacity ratios remain practically intact inductive value increases.

The coax ring radiator does not have these disadvantages. On the contrary. The L and C Values of this emitter can be set as required when using Ko axial cable. The principle of this coax radiator is known from the coaxial Trap, a coaxial parallel resonant circuit (see "The antenna dictionary" by Karl H. Hille and Alois Krischke, 1988 edition, page 144).

These coaxial traps have the disadvantage of a certain broadband because the L-value of the cable core increases with winding, the cable capacity value, Shielding soul, however, remains.

This disadvantage must be remedied. In the coaxial trap, the capacity is Umbrella soul, the accompanying capacity to form the coaxial resonance relationships, so to form the parallel resonant circuit. From a physical point of view a coaxial cable is a Faraday cage with a concentric inside ladder. Tensions, whether coming from outside or generated by a resonant circuit Conditions via the cable core only form on the outer skin of the screen out.

This accompanying capacity is now realized using a coaxial series capacity sufficient dielectric strength is shortened. Although the coaxial shortening capacity makes up only a fraction of a coax ring emitter, this effect shortening over the entire shielding distance.

As with the coaxial trap, which forms a parallel resonant circuit in that the cable core of one end with the braid of the other end connects, this connection now becomes the coaxial shortening capacity produced. This creates an electrical expansion of the distance between Cable core and screen, not only in the area of the coaxial shortening capa zitat. This Series C is predictable.  

This is what the formula stands for:

C₁ = cable capacity
C _total = Capacity in the optimal LC ratio
C _s = series capacity

With this variable electrical expansion option you can control the resonance Shift conditions (capacitive coordination).

One has a variable magnetic expansion possibility that one z. B. two spreads large coils of a coaxial ring radiator from each other (inductive Poll). Is only one turn to achieve the resonant circuit conditions required, the inductive change can be achieved by compression.

With these two tuning options you can use a coaxial cable to produce flat radiators with resonance frequency and an tennengüte (district quality) is adjustable and also over a usable broadband disposes.

Such a coax ring emitter is fed in serially. The connection points, that make it a parallel resonant circuit are separated on the two open points, the impedance and resonance measurement is carried out and then, based on the measurement result, the symmetrical impedance transformer wrapped with a smooth adjustment of supply cable and Coax ring radiator guaranteed.

Deviations from the desired frequency are in the impedance and resonance measurement recognizable and can immediately, e.g. B. by further coaxial shortening capacitors or can be corrected by inductive tuning.

With the options described you have a space-saving easily under antenna to be delivered which meets the desired requirements.

Special attention must be paid to the coaxial isolation of the shortening capacities, as here between the coverings of screen and cover high capacitance occur.

See the principle drawing.  

Points A-B are connected in the coaxial trap for multi-band antennas. The Points C-D remain open. Windings and cable capacity form the blocking circuit.

Points A-E are connected on the coax radiator. Points C-D-B remain open.

The resonance and impedance measurement is carried out at points A-E. After the result of the measurement is calculated for the symmetry transformer.

This is also looped in there with its secondary side.

If several coax rings are required, the adjustable shortening can be used capacity include this. The effect is the same.

With the geometric circular shape, g.F. several shortening capacities hang up, which are then connected to each other.

The insulation between the coverings must be voltage-proof accordingly. Because of the voltage conditions, the insulation must be adjustable Protruding shortening capacity.

Claims (10)

1. A shortened geometric blocking circuit antenna based on the known principle of coaxial traps with serial feed via adapter elements, characterized in that:
the cable capacity of the coaxial cable used can be tuned by means of a coaxial series additional capacitance placed around the cable, so as to bring about the desired resonance case with the inductance value of the geometric surface covered by the cable core. 2. The serial shortening capacities are adjustable by two or more stackable metal sleeves or metal pipes with good metallic Connection with each other, also for better adjustment with threads can be provided. 3. When using two or more cable rings, the desired capacitive Shortening is also achieved in that the coaxial series shortening capacity has a bundle effect. 4. The inductance change to tune to resonance by upsetting (Ver smaller) of the geometric antenna inductance area, but also at two or more cable rings or areas surrounding the cable by spreading or only partial spreading of the radiator rings or radiator surfaces can be added. 5. That apart from the ring shape also all other geometric shapes as a vote bare spotlights are to be used. 6. The geometric spotlight, due to its space-saving structure, a brings easy adjustability, and so the effective antennas surface of the most varied elevation angles of the free space radiation easily is to be adjusted. 7. With at least two cable rings, these can be offset by 90 ° (cross system) in order to generate an omnidirectional characteristic. 8. The serial shortening capacity can be divided between both cable turns beginnings and thereby a certain directional sensitivity is achieved. (In extreme cases, capacities that have been divided (serial capacities) 180 °.) The arrangement of the division is arbitrary. 9. The coax radiators arranged as parasitic elements, the main coax radiator can make direction sensitive. 10. The above-mentioned tuning measures for resonance are also combined with one another can be applied.