FR2523772A1 - Compact antenna for TV reception - comprises rectangular frame with frame reflector, both tuned to operating band by their dimensions - Google Patents

Abstract

A radiating or active element (1) in the form of a rectangular frame is tuned to the operating frequency band by its dimensions. A reflector (2) comprises a square closed loop tuned to the operating frequency band by its dimensions. Upper and lower elements (6) position the reflector w.r.t. the active element. Both active and reflective elements present characteristics of an inductive circuit. A bifilar matching line (3) attached to the active element provides matching between the element and the coaxial cable (5) connecting it to the TV receiver. A metallic tube in which the coaxial cable is located provides electrical assymmetry. The cable is maintained in position by washers and polyester resin blocks. The tube is located between the active and reflective elements to provide mechanical support on a fixing foot (7).

Description

 The present invention relates to a device intended for the reception or the emission of hertzian waves.

 This device was studied to present a reduced obstruction, not requiring a usual assembly system (strapping mast stays), while respecting the characteristics and qualities imposed by the transmission of the frequencies UHF (450-865! Thz) used in television.

Its original features according to the invention consists in:
10 Combine two active elements, a radiant and a reflector
each behaving like electrical coef circuits
have a high Q such as inductive circuits.

20 A balun, apart from its electrical functions, is
placed in such a way that all of the
elements around him as shown in the figure in perspec
tive Jointe and that it mechanically supports the means of
sealing of electrical connections, points A and
B in the figure.

 It consists of a radiating element (1) of rectangular shape having all the properties of the skeleton antenna tuned by its dimensions in the working frequency band.

 - a reflector element (2) constituted by a square loop, closed, granted by its dimensions in the working frequency band.

 I1 is intended to modify the diagram of the radiating element (1) and to protect it against parasitic waves which may come from the rear of the saddle.

 - a two-wire adapter line (3) from which the signal is taken at a location chosen to ensure good agreement between the impedance of the radiating element and the characteristic impedance of the connecting cable (5) to the television.

 - an asymmetrization system (4) which has to fulfill a double electrical and mechanical role. I1 consists of a metal tube in the center of which is placed the coaxial cable (5) held by centering washers. At its ends, at lower point B, the coaxial cable (5) penetrates and is held by a block of cast polyester resin; at point A the coaxial cable (5) joins the two-wire line (3) and the electrical contacts are made there by crimping. Linen block of molded and cast polyester resin ensures the watertightness and mechanical resistance of this point A. In this it ensures its electrical functions by applying the so-called Bazooka principle.

Its second role, mechanical, is ensured by its positioning inside the volume constituted by the elements (1) (2) and (3). At point A, the two-wire line (3) is held rigid by the block of polyester resin, towards point B a fixing lug (7) is welded and allows the assembly of the set by a simple threaded rod or a bolt on a ridge tile or a chimney tray.

 The upper and lower elements (6) ensure the positioning of the element (2) relative to the element (1). The mechanical contact points are welded. The lower element (6) is also fixed to the tube (4).

 These elements are made electrically neutral by determining their mechanical length.

Under these conditions, they do not disturb the operation of elements (1) and (2).

Main Features
To cover all IllF frequencies between 450 and 865 Mhz, bands
IV and V used in television, it has been studied and produced four devices according to the invention.

 Each of these devices or antennas works in a wide band from 70 to 110 Mhz.

 - The dimensions of the elements constituting length, width, spacings are directly proportional and a function of the wavelength at the central frequency of the band considered. Except the bracket (7) and the length of the coaxial cable (5).

 - The gain obtained is approximately 10 dB, comparable to that of an antenna 1 to 1.5 meters in length and operating according to the principle of YAGGI.

 - The standing wave rate is equal to or less than 2.2 in the band considered.

 - The insertion of the asymmetrizor (4) does not provide any damping or any loss of energy.

 - These antennas are currently made mechanically from formed and brazed aluminum wire, 4 mm in diameter. It is possible to use another non-magnetic metal with a neighboring diameter.

 - Made of aluminum, this device, the largest dimension of which does not exceed 310 mm and equipped with a coaxial cable 2 meters in length, weighs approximately 200 grams.

Claims (2)

 10 Device according to the invention intended for the reception or the emission of UHF frequencies, characterized mainly by the association of a radiating element (1) forming a closed circuit, tuned to a frequency and equivalent to an inductive circuit of coefficient high overvoltage, with a reflective element (2) having the same inductive circuit characteristics.  I1 is associated with it an asymmetrizer materialized by the element (4) as well as the elements (6) ensuring the relative mechanical positions between the elements (1) and (2).  20 Device according to claim 1  comprising a balun (4) characterized apart from its electrical functions by its constitution of mechanical position in the assembly to ensure the rigidity and the tightness of the electrical connections.  30 Device according to claim 1 and claim 2  characterized by the mechanical connection elements (6) determined and positioned so that they provide the mechanical connection between the elements (1) and (2) without causing any electrical disturbance.