FR2545991A1 - EXTENSIBLE LOOP ANTENNA TO THE OUTSIDE - Google Patents

Abstract

THE INVENTION RELATES TO A LOOP ANTENNA FOR USE IN A TELEVISION INCLUDING A BOX. ACCORDING TO THE INVENTION, A FIRST ANTENNA LOOP SECTION 13 IS PROVIDED IN THE BOX 11 AND A SECOND ANTENNA LOOP SECTION 14 IS ARRANGED WITH RESPECT TO THE FIRST SECTION TO FORM A SENSITIVELY COMPLETE LOOP, THE SECOND SECTION BEING PROGRESSIVELY MOBILE BETWEEN A FIRST POSITION WHERE THE SURFACE OF THE LOOP ANTENNA IS SENSITIVELY INSIDE THE BOX AND A SECOND POSITION OR A SENSITIVE PART OF THE SURFACE OF THE LOOP ANTENNA IS OUTSIDE THE BOX. THE INVENTION APPLIES IN PARTICULAR TO PORTABLE TELEVISIONS.

Description

The present invention relates to antennas for television sets and

  more particularly to antennas

  adjustable parts of the TV.

  The reception of signals transmitted by the air by a television requires, in almost all cases, an antenna or a signal gathering structure in order to obtain images reproduced in an acceptable manner. In the case of a portable television, the Antenna must also be portable to allow the use of the TV in different locations Examples of these antennas include the monopole and the dipole (telescopic rabbit ears) well connected OE that can be part of the TV or be a separate unit Although providing an acceptable performance in most cases, antennas of this kind are unattractive and have directional reception characteristics often requiring careful adjustment when changing station or receiver location In addition, such as nonopoleset antennas dipoles require considerable space for a good fit, we can not easily use them in confined spaces, for example when the TV where they are mounted is placed on a bookshelf or the like. In most cases, these antennas are effective for receiving very high frequency signals only and satisfactory reception of ultra high frequency signals. may require

additional antenna.

  It is known that a loop antenna can be used instead of monopoles or telescopic chipoles for receiving very high frequency signals in order to improve the omnidirectionality of the antenna, thus reducing the necessary positional adjustment. when changing channel or receiver location In order to obtain a sensitivity and signal / noise ratios comparable to monopole and dipole antennas, the area delimited by the loop must be large enough, with

  as a result, a cumbersome and unattractive arrangement.

  In addition, some form of mechanical or electrical adjustment of the loop parameters may be necessary to optimize the reception of signals for each channel

  received, thereby increasing the complexity of the antenna.

  U.S. Patent No. 4,342,999 of 3 August 1982, in the name of OM Woodward et al. And entitled "Loop Antenna Arrangements for Inclusion in a Television Receiver", discloses a loop antenna placed in the box of a television set, which eliminates the need for However, for small screen televisions, the box is correspondingly small, which therefore limits the area bounded by the loop.

  antenna and reduces the efficiency of the antenna.

  The present invention is directed to an extensible loop antenna where the aesthetic advantages of the internal antenna are incorporated while providing a performance comparable to that of monopole antennas.

and dipoles.

  According to the invention, a loop antenna is produced

  for use in a television set with a cabinet.

  The loop antenna includes a first section of a

  loop that is inside the cabinet of the TV.

  A second section of a loop is located near the first section and substantially forms, with it, a complete loop. The second section of the loop is progressively movable between a first position and the antenna surface is substantially in position. television and a second position or a sensitive part of the antenna surface is outside

of the TV cabinet.

  The invention will be better understood, and other purposes, features, details and advantages thereof

  will become clearer during the description

  explanatory text which will follow with reference to the accompanying diagrammatic drawings given solely by way of example and illustrating several embodiments of the invention, and in which: FIG. 1 is a perspective view of a television set or incorporates a built-in antenna; according to the present invention, shown with torn parts to illustrate the antenna in its retracted position; Figure 2 is a perspective view similar to Figure 1 illustrating the antenna of the present invention at its extended position; Fig. 3 is a top plan view of the antenna of the present invention illustrating its operating elements; Fig. 4 is a diagram of an electrical tuning circuit associated with the antenna of the present invention; Figure 5 shows another embodiment of an antenna tuning circuit; and FIG. 6 is another embodiment of a

antenna tuning circuit.

  Referring to Figures 1, 2 and 3, we can see

  a television 10 having a structure forming a cabinet.

  The television 10 contains an antenna assembly 12 which includes a loop having substantially a rectangular cross-section. The antenna assembly 12 includes a first antenna loop portion or section 13 and a second antenna loop portion or section. The first part 13 is completely inside the box 11 and, as can be seen in FIG. 3, it consists of three elongate members 16, 17 and 18 which form the three sides of a rectangle. 17 extends through the front of the cabinet 11, near the top and is disposed at the front of the picture tube 15 It is desirable, for the best reception of the signals, that the antenna assembly 12 has as large as possible while being placed as far as possible from metal structures, including the shadow mask in the image tube 15 The other elongated members 16 and 18 of the portion 13 extend rearward along sides of the cabinet Part 13, as shown in FIG. 3, is configured so that the surface of the antenna is as large as possible and to allow as much of the antenna as possible to be away from the picture tube. , while adapting around the structure elements teb that the tube-image mounting protuberances that are used to attach

the tube at the front of the cabinet.

  Part 13 may be made of thin metal strips (such as brass), a metal tube or a thick wire, for example, forming a continuous structure, and it may be held in place in the case by a means conventional, such as an adhesive or self-closing pliers, or by molding an automatic closing structure or the like in

the cabinet itself.

  The antenna loop portion 14 also comprises three elongated members 20, 21 and 22 which also form a continuous structure whose member 21 is aligned with the rear of the box 11. The two other elongated members and 22 are aligned in parallel with the members lying 16 and 18 of part 13 which extend towards the rear,

  and they are near them, but not touching them.

  The elongate member 21 is disposed outside the cabinet 11 and the elongate members 20 and 22 are slidably mounted through holes in the cabinet 11 by means of sleeves or guide tubes either attached to the cabinet or molded into the cabinet itself. For example, part 14 may be made of metal bands, tubes or rods, such as part 13, bent or otherwise suitably shaped. In Fig. 1, the antenna loop portion 14 is shown in its retracted or inwardly biased position. The elongate member 21 is near the cabinet, which has a clean, unobstructed appearance. The back of the cabinet 11 may also contain a slot or recess for receiving the elongated member 21 It can be seen in Figure 1 that the elongate member 20 extends over the depth of the o Dffret 11 The antenna loop portion 14 could also be constructed with the elongate members 20 and 22 as telescopic elements, i.e., such as those used in mopole or dipole antennas

  rather than in the form of fixed-length members.

  FIGS. 2 and 3 show the assembly 12 with the antenna loop portion 14 at its extended or pulled out position. By allowing the antenna portion 14 to be extended, the surface contained by the assembly horizontally aligned loop antenna 12 is considerably larger than is possible with the antenna assembly 12 completely built in the box 11 as can be seen in FIG. 3, the dotted line representing the box outline It has been found that for the reception of signals broadcast on the very high frequency channels (channels 2-13), the increase of the size of the surface of the antenna loop improves the reception of the signals By allowing the part 14 antenna loop to withdraw into the cabinet 11, this offers an aesthetically more pleasing appearance when the device is not in use and this gives the receiver a greater mobility than that obtained if the part of the antenna outside the box is held in place The TV can also be placed in a more confined space than would be possible with a

  TV having a monopole antenna or conventional dipole.

  The amount by which the antenna loop portion 14 extends out of the cabinet 11 will determine the total area of the antenna loop. Surprisingly, while it is intended to be used primarily as a very high frequency antenna, found that by controlling the surface of the loop by adjusting the position of the portion 14, this allowed the antenna assembly 12 to be equally

X 5545991

  used for reception of ultra-high frequency broadcast signals (channels 14-83), thereby eliminating the usual need for an ultra-fast loop antenna

  separate high frequency or "butterfly knot" antenna.

  For the reception of very high frequency signals the antenna assembly 12 is substantially omnidirectional and the position of the television has little consequence. The reception of the ultra-high frequency signals for certain channels may require a positioning of the television or a partial withdrawal of the television. the loop portion 14 to obtain optimal reception of the signal in a

given location.

  In order to adapt the impedance of the antenna assembly 12 to the television tuner, an antenna tuning circuit 23 as shown in FIGS. 3 and 4, which is connected to the supply terminals 30, is provided. and 31 of the antenna assembly 12 The fixed tuning circuit shown

  in FIG. 4, which comprises a symmetrical transformer

  In FIGS. 3, a capacitor 25, a coil 26 and capacitors 27 and 28 (having the indicated values, by way of example) 1 produces an acceptable adaptation to a 75 f L load as a very high frequency tuner. and 4, a band divider 40 is illustrated as applying the signals of the antenna assembly 12 to a very high frequency tuner

  41 and an ultra high frequency tuner 42 of the TV.

  Optimized omnidirectionality of the antenna has been found to occur with a 1 μF capacitance placed in series with the antenna at an interval between the elongated members 18 and 22 which are diametrically opposed to the power supply terminals 30 and 31. presence of this ability also simplifies circuit construction

  23 by reducing the amount of adaptation of

  pedance required for the tuning circuit 23 The cover

  of the ends of the elongated members 18 and 22 of about 19.05 mm with an air gap of between 6.35 and 7.94 mm produces the desired capacitance shown in FIGS. 4, 5 and 6 by the capacitor 29 without require a separate capacitor The value of the capacitor changes while the loop portion 14 is depressed, which

  contributes to the agreement of the antenna 12.

  A more precise tuning of the antenna for particular diffuse channels is possible by using more complex antenna tuning circuits, such as those shown in FIGS. 5 and 6, where the very high frequency tuner voltages of the antenna are used. television for controlling the conduction state of the rod diode to change the operation of the tuning circuit to improve the gain characteristics of the antenna

  for particular ranges of broadcast frequencies.

  The value of the components given in FIG. 4, when used with an antenna assembly having a loop of approximately 45.7 cm side, gives a performance

  comparable to a monopole or simple dipole antenna.

Claims (9)

R E V E N D I C A T I 0 N S   A loop antenna for use in a television or incorporating a box structure characterized by: a first antenna loop section (13) disposed in said box structure; a second antenna loop section (14) disposed with respect to said first loop section to substantially form a complete loop, said second loop section being progressively movable between a first position where the surface of said loop antenna is substantially the interior of the structure and a second position where a sensitive part of the surface of said loop antenna is outside said structure forming box.   Antenna according to Claim 1, characterized in that the first antenna loop section (13) comprises a continuous strip of metal.   Antenna according to claim 1, characterized in that the first antenna loop section (13) comprises a cylindrical tube made of metal.   Antenna according to claim 1 characterized in that the first antenna loop section comprises a thick thread.   Antenna according to claim 1 characterized in that the second antenna loop section (14) comprises a continuous rod made of metal.   Antenna according to claim 1 characterized by antenna tuning means (13; 23; 29) disposed between   first (13) and second (14) antenna loop sections.   Antenna according to claim 6, characterized in that the antenna tuning means (13; 23; 29) comprises a first tuning means (23; 24) which includes means for adapting the impedance of said antenna. to a tuner in said television connected between the power terminals between   first and second antenna loop sections.   Antenna according to claim 7, characterized in that the antenna tuning means comprises a second antenna tuning means which comprises an air gap.   (29) between the first and second antenna loop sections.   9 Antenna according to claim 8 characterized in that the second tuning means (29) is placed on the opposite side of the antenna loop relative to the first means agree (23; 24).   Antenna according to claim 8, characterized in that the air gap (29) produces a capacitance which   contributes to the tuning of the loop antenna.   Antenna according to claim 1, characterized in that the first antenna loop section (13) comprises first and second elongated members (16; 18) which extend along the sides of the box structure (11) and a third elongated member (17) extending along the front of the box structure and connecting the first and second elongated members;   the second antenna loop section (14) progressively   extendable outwardly of the box structure includes fourth and fifth elongate members (20; 22) along the sides of the structure and disposed at   proximity of the first and second elongate members respectively   and a sixth elongated member (21) connecting the fourth and fifth elongated members; and the antenna tuning means disposed between the first and second antenna loop sections is coupled between the first and fourth elongated organs.