RU2231876C1 - Spiral antenna with readjustable resonance frequency - Google Patents

Abstract

FIELD: antenna equipment, ultra short and decimeter waves radio communication systems.

SUBSTANCE: spiral antenna with readjustable resonance frequency includes elements functioning as radiator: dielectric base carrying emitting winding put on it, aerial distributed capacitor of variable capacitance formed by one or several metal bars positioned along axis of dielectric base and emitting winding. Given antenna has elements functioning as matching tuned transformer with primary and secondary windings positioned on dielectric base. Finish of primary winding and start of secondary winding are interconnected, cylindrical capacitor of variable capacitance comprises mobile outer metal plate connected to metal bars, dielectric insulator, inner metal plate connected to start of primary winding. There are positioned metal guiding contact bushing made fast to dielectric base between start of emitting winding and finish of secondary winding interconnecting them electrically and through metal bars to mobile outer metal plate. Possibility of readjustment of resonance frequency of spiral antenna is ensured by simultaneous movement of metal bars of distributed capacitor of variable capacitance and mobile metal plate of cylindrical capacitor of variable capacitance along vertical axis of primary and secondary windings and radiator winding in correspondence with direction of readjustment of resonance frequency of spiral antenna which leads to optimal matching in wide frequency range.

EFFECT: design of spiral antenna displaying optimal matching during readjustment of resonance frequency in wide frequency range.

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Description

The proposed spiral antenna with tunable resonant frequency relates to antenna technology and can be used in VHF and UHF radio communication systems.

The prior art spiral antenna [1], consisting of a wire wound on an elastic base of fiberglass according to a sinusoidal law. With this winding, an optimal sinusoidal current distribution occurs along the length of the spiral antenna, which gives it an advantage over a simple vertical antenna. The number of turns of a spiral antenna needed for resonance depends on the length of the spiral, pitch, diameter of the dielectric base and the diameter of the wire of the spiral. The manufacture of a cone-shaped dielectric base and the unevenness of the spiral winding make it impossible to calculate a spiral antenna, and winding the antenna conductor according to a sinusoidal law is difficult. The disadvantage of this antenna is the impossibility of tuning the resonant frequency.

Closest to the proposed spiral antenna with tunable resonant frequency is the antenna [2], which is selected as a prototype. It consists of a wire wound around a fiberglass rod, and the resonance frequency is tuned by a variable capacitor connected at the power point in series with the distributed inductance of the lower part of the emitter. Structurally, a variable capacitor is formed by the inner surface of a metal cylinder, which is an element for attaching the antenna and part of the emitter winding, which has the ability to move and fix in the vertical direction. As a dielectric strip, a heat shrink tube is used to protect the antenna emitter from external influences. The disadvantage of this design is that moving the emitter to the lower part of the cylinder leads to an increase in the capacity of the cylindrical capacitor, that is, to a decrease in the resonant frequency of the antenna while reducing part of the inductance of the emitter. This leads to a decrease in the tuning range of the spiral antenna due to a mismatch in the input impedance of the antenna and the transceiver at the edges of the operating frequency range.

The technical result of the inventive spiral antenna with tunable resonant frequency is the creation of a spiral antenna with optimal coordination when tuning the resonant frequency in a wide frequency range.

The technical result is achieved by the fact that a spiral antenna with a tunable resonant frequency contains elements that act as a radiator: a dielectric base with a radiating winding located on it, a distributed capacitor of variable capacitance (air), formed by one or more metal rods located along the axis of the dielectric base, and radiating winding. This antenna also contains elements that perform the function of a matching resonant transformer: primary and secondary windings on a dielectric base, and the end of the primary winding and the beginning of the secondary winding are interconnected, a cylindrical capacitor of variable capacitance consisting of a movable outer metal plate connected to metal rods, a dielectric insulator, inner metal lining connected to the beginning of the primary winding. There is also a metal guide contact sleeve, rigidly mounted on a dielectric base between the beginning of the radiating winding and the end of the secondary winding, electrically connecting them to each other and through metal rods with a movable outer metal lining. The resonant frequency of the spiral antenna can be tuned by simultaneously moving the metal rods of the distributed variable capacitor and the movable outer metal lining of the variable capacitance cylindrical capacitor along the vertical axis of the primary, secondary and emitter windings in accordance with the direction of tuning of the resonant frequency of the spiral antenna, which ensures optimal coordination in a wide frequency range.

Figure 1 shows the design of a spiral antenna with a tunable resonant frequency, where

1 - dielectric base;

2 - metal rod;

3 - metal guide contact sleeve;

4 - movable outer metal lining;

5 - dielectric insulator;

6 - inner metal lining;

7 - coaxial supply conductor;

8 - primary winding;

9 - secondary winding;

10 - radiating winding.

A spiral antenna with a tunable resonant frequency consists of a dielectric base 1, on which three windings from a wire are located from bottom to top: primary winding 8, secondary winding 9, radiating winding 10.

The lower part of the dielectric base is rigidly bonded to the inner metal lining 6, surrounded by a dielectric insulator 5 and a movable outer metal lining 4. The inner metal lining, the dielectric insulator and the movable outer metal lining form a cylindrical capacitor of variable capacitance. In the body of the movable outer metal plate parallel to the axis of the dielectric base, metal rods 2 are rigidly mounted, forming a distributed capacitor of variable capacity (air) with a radiating winding.

A metal guide contact sleeve 3, rigidly mounted on a dielectric base between the beginning of the radiating winding and the end of the secondary winding, electrically connects them together and through metal rods with a movable outer metal lining of a cylindrical capacitor of variable capacitance. Moreover, the movement of metal rods of a distributed capacitor of variable capacitance and a movable outer metal lining of a cylindrical capacitor of variable capacitance is carried out simultaneously and in accordance with the direction of tuning the resonant frequency of the spiral antenna. In this case, the beginning of the primary winding is connected to the inner metal lining, and the end of the primary winding and the beginning of the secondary winding are interconnected at one point.

The antenna is powered through a coaxial conductor 7 connected to the connection point of the end of the primary winding and the beginning of the secondary winding of the matching transformer.

Figure 2 shows a schematic diagram of an electrical circuit of a spiral antenna with a tunable resonant frequency, where

1 - emitter;

2 - matching transformer;

L1 - radiating winding;

L2 - secondary winding;

L3 - primary winding;

C1 is a cylindrical capacitor of variable capacitance;

C2 - distributed capacitor of variable capacitance.

The principle of operation of a spiral antenna with a tunable resonant frequency is as follows.

The signal of the carrier frequency of the transceiver is fed to the primary winding L3 of the matching transformer 2, where the resistance of the transceiver and the helical antenna are matched. In this case, the role of the matching transformer is performed by primary L3 and secondary L2 windings located on a dielectric base from a wire with a parallel-connected cylindrical capacitor of variable capacitance C1, which allows resonance of the matching transformer 2.

Next, the resonant signal of the carrier frequency is supplied to the emitting winding L1 of the emitter 1. In this case, the emitter 1 located on the dielectric base is emitted by the emitting winding L1 with a distributed capacitor of variable capacitance C2 connected in parallel. The resonance of the emitter is achieved through the use of a distributed capacitor of variable capacitance C2, connected in parallel with part of the winding of the emitter L1.

Changing the resonant frequency of the spiral antenna in the direction of increasing or decreasing it is done by simultaneously reducing or increasing the capacity of a cylindrical capacitor of variable capacitance C1 and a distributed capacitor of variable capacitance C2. Structurally, this condition is satisfied by simultaneously moving the movable outer metal lining of the cylindrical capacitor of variable capacity and the rods of the distributed capacitor of variable capacity parallel to the vertical axis of the primary, secondary and radiating windings by any of the known methods. To protect the antenna from external factors, a cover from an insulating tube can be used.

Sources of information

1. "Antennas" / Ed. K. Rothammelya. - St. Petersburg, Boyanich, 1998, p. 508, 509.

2. Patent for invention, USA No. 5, 955, 996, 1999

Claims (1)

A spiral antenna with a tunable resonant frequency, comprising a primary winding, a secondary winding and a radiating winding located from bottom to top on a dielectric base, the lower part of which is rigidly bonded to the inner metal plate surrounded by a dielectric insulator and a movable outer metal plate with the dielectric base installed in parallel with it metal rods, as well as a metal guide contact sleeve, rigidly mounted on a dielectric axis between the beginning of the radiating winding and the end of the secondary winding, electrically connecting them to each other and through metal rods with a movable outer lining, the beginning of the primary winding connected to the inner lining, and the end of the primary winding and the beginning of the secondary winding connected to each other at the power point.

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