AU598904B2 - Indoor antenna - Google Patents

Description

AU--11010M~ PCT WORLD INTELLECTUAL PROPERTY ORGANIZATION PC Interniaional Bureau INTERNATIONAL APPLICATION PU I^ D t D H PT T COOPERATION TREATY (PCT) (51) International Patent Classification 4 (11) Intenr .,onal Publication Number: WO 88/ 04836 H01Q 1/36, 19/28 Al (43) International Publication Date: 30 June 1988 (30.06.88) (21) International Application Number: PCT/AU87/00429 (22) International Filing Date: 17 December 1987 (17.12.87) dI .:.-"unment c-ts.. 'i US. 1 s i I.

i d. dLd is4'0 YI.

Published tI With internationat~sdercep'orT. With amended claims (31) Priority Application Number: PH 9565 (32) Priority Date: (33) Priority Country: 18 December 1986 (18,12,86)

AU

(71)(72) Applicants and Inventors: YIP, John, Chu., Sing [CN/AU]; YIP, Catherine, Wei, Yuen fCN/AU]; 13 Blue Jay Court, West Pennant Hills, NSW 2120 (AU).

(74) Agent: EDWD. WATERS SONS; 50 Queen Street, Melbourne, VIC 3000 (AU), (81) Designated States; AT (European patent), AU, BE (European patent), CH (European patent), DE (European patent), FR (European patent), GB (European patent), IT (European patent), LU (European patent), NL (European patent), SE (European patent), A.O.J.P. 1 8 AUG 1988

AUSTRALIAN

15 JUL 1988 PATENT OFFICE (54) Title: INDOOR ANTENNA (57) Abstract An indoor antenna having at least two planar non-parallel structures 2, 6, 7) in which the planar structures include or support antenna elements 4, 5, 9 and 12), the antenna elements including driven elements 9) and parasitic elements the angle between the structures being adjustable. The use of parasitic elements and the adjustable angle between the elements beneficially influence the performance characteristics such as band width, gain and front to back ratio of the antenna, ii i i__ WO 88/04836 PC/I'AU87/00429 INDOOR ANTENNA The present invention is directed to the field of antennas and in particular antennas with planar structures for indoor use.

Directional antennas, incorporating multiple parasitic elements such as directors or reflectors, are common in outdoor applications, for example Yagi antennas, to overcome any reception problems arising from, low field strength,, and to reduce ghosting which can arise from multipath reflections.

The design of conventional indoor antennas, however, is constrained by factors such as a lack of space and visual appearance.

As a result, conventional indoor antennas usually comprise a dipole element in the form of exposed rigid rods or a loop wire supported by a stand or base. Such an antenna will usually pick up sufficient sgnal in urban areas where field strengths are usually high but ghosting remains a common problem. Yagi antennas ar t also used as indoor antennas but they occupy considerably more space.

Such indoor antennas are unsightly and awkwardly shaped.

Towards overcoming the above problems, the present invention is an antenna for indoor use comprising two or more planar structures characterized in that said planar structures support antenna elements including driven and parasitic elements and the planar structures are substantially non-parallel.

The word driven describes elements that are electrically feeding the antenna cable.

According to a first embodiment of the invention, the antenna comprises at least two planar structures connected along adjacent edges to define at least one common edge, wherein one planar structure supports at least one driven element and optionally parasitic elements, and the other planar structure supports parasitic elements.

PCT/AU87/00 4 2 9 WO 88/04836 2 The use of parasitic elements and the adjustable angle between elements in connected planar structures affect beneficially the performance characteristics such as the bandwidth, gain and the front-to-back ratiu of the antenna.

The angle can be preset during manufacture or allowed to be adjustable for fine tuning during normal usage.

Preferably, the structures in the first embodiment are rectangular and positioned on substantially a horizontal surface either in an inverted-V shaped configuration with the commnn edge upper-most and free edges extended apart, or alternatively with the common edge vertical as for the case of receiving vertically polarized signals. Positioning on a wall or other vertical surface by hanging or other fixed means is also possible.

Preferably, the planar structures are made from non-metallic material such as perspex, plastic, fibreglass board or the like.

The antenna elements on the other hand are conductors, preferably mnade from mutallic wires, films or strips. Materials with suitable dielectric properties may also be used to achieve reduction of the lengths of the antenna elements which'are required to resonate at the requisite design frequencies. The antenna elements are supported on the planar structure, preferably by bonding onto its surface such as in the case of printed circuit boards, however, embedding the ahtenna elements in the structures is also possible such as in the form of slots, or as wire threaded through or encased in the structure during its formation into final form.

As stated previously, the use of parasitic elements and the adjustable angle between elements in connected planar structures affect beneficially the performance characteristics of the antenna.

Notably, orientation of the antenna according to the first embodiment will cause it to function as a directional antenna. Additional parasitic elements, placed WO 88/04836 PCT/AU87/00429 -3in a plane parallel and close to that of the driven elements, for example, in the same planar structure supporting the driven element, will provide improved gain or widened bandwidth of reception. Such parasitic elements can be placed in a plane in front of that of the driven elements hence acting as directors.

A parasitic element such as a reflector placed in the second planar structure of the antenna according to the first embodiment would also enhance the performance characteristics such as the gain and front-to-back ratio.

The angle extended between the two planar structures and thereby the angle and distance between antenna elements can be altered to optimize the performance characteristics for the desired frequency band of operation. This arrangement also enables a broadband antenna with improved gains and front-to-back ratios over a wide bandwidth to be designed.

In a further embodiment of the invention where there may be more than one driven element, the driven elements may be two loops joined at their respective ends to provide improved gain or widened bandwidth.

It can be seen from the above that the invention will be small, compact and stable and be directional in its reception of signal, A further important advantage is that the antenna may be formed to serve a decorative or display purpose in that the planar structures can be formed as a holder for photographs, pictures or the like, In such an embodiment of thai invention, each structure is preferably provided with a planar outer transparent member, The invention according to various preferred embodiments will be described with reference to the following figures: Figures la, ib and ic are perspective front and rear views respectively of the invention according to a first embodiment.

Figures 2a and 2b are a perspective and inside WO 88/04836 PCT/AU87/00429 4 front view of a second embodiment of the invention.

Figure 3 is a view according to a third embodiment.

Figure 4 is a view according to a fourth composite embodiment.

Figure 5 illustrates the angular relationships, for t H-polarized signal reception.

Referring to figures la and lb, the antenna shown is a preferred embodiment comprising planar structures 1, 2 connected along a common edge 2a.

Planar structure 1 supports the driven elements 3 which consist of a pair of stacked and joined folded dipoles made of metallic wires. The two main antenna elements may not be identical, depending on the application. One or more parasitic elements 5 are also in the first planar structure, lying in a plane parallel to, and in front of, that of the driven elements. The parasitic elements 5 serve to improve the bandwidth and gain by acting as a set of directors and as bandwidth-broadening elements.

The planar structure 2 has a parasitic element being a reflector 4 made of preferably aluminium plate .r film mounted thereon. In this embodiment, a single reflector may be used for both dipoles, as shown.

Alternatiely, multiple and separate reflectors can be used.

As a note, reflectors are not required in ghost-free reception areas but such situations are relatively rare.

Preferably, in this embodiment, the main antenna elements are mounted on cardboard and then inserted in between the t'Lo members la and lb of the planar structure 1 which preferably is a perspex sheet folded over.

Alternatively, not shown, tKe driven elements may be threaded through suitable holes made in the rear surface of planar sLcucture 1.

From the rear of the planar structure 1, the output signal of the driven antenna elements is fed to, for example, a television receiver. A matching stub, in the form of a short length of antenna cable, and a balun

M

~_IC~

WO 88/04836 PCT/AU87/00429 (matching transformer) in series can be connected to the antenna output for improving the impedance char.acteristics over the desired UHF band; the matching stub and balun can be physically located between the planar stLuctures.

Referring to figures 2a and 2b, a further embodiment of the invention is shown. Two planar structures 6 and 7 consist of preferably cardboard covered in plastic and are connected along a common movably connected edge 7a.

The structures can be positioned to extend in an inverted-V shape as shown, with bottom edges connected by a member 8.

In this embodiment, the driven element 9 is a substantially triangular loop antenna contained in the structure 7. Parasitic elements are directors 10 made of thin metal strips contained in structure 6. This electrical arrangement is suitable for narrow-band reception. For broadband reception, the electrical arrangement described under the first embodiment can be used instead. Figure 2c illustrates two movably connected structures made of plastic cardboards. A connecting member 8a is inserted into the sideholes, thus holding the structures in place. A similar member 8b is used on the other side to improve rigidity, These members can be re-positioned upwards or downwards for adjusting the angle between the structures.

Referring to figure 3, in this embodiment, the antenna is hung against a wall or other vertical surface which, in many situations, provides improved reception and reduces the detrimental effect on reception due to bodily movements. The vertical beam-width of the antenna may be designed to be wide enough for these alternatives.

Referring to figure 4, there is shown a composite embodiment of the invention. Whereas the antenna according to its preferred embodiments is primarily intended for UHF reception, a similar antenna can be designed for other frequency bands, subject to the user acceptability of the physical size. The output signal of the antenna can be combined with the signal from another indoor or outdoor

M

WO 88/04836 PCT/AU87/00429 -6antenna such as a VHF television antenna by means of a signal combining unit. Accordingly, in this embodiment the UHF antenna structure is used to support also a VHF antenna mounted upon or attached to it.

Two rotatable telescopic metallic rods 12 forming the VHF antenna may be mounted on the upper join of the UHF antenna which is similar to that shown in figure 1 for example. It is modified in that the common edge of the planar structures is a narrow and flat member 11.

The design of a combined UHF and VHF antenna system as shown in figure 4, offers the advantages of a high le-el of flexibility in the adjustment of the positions of the two telescopic rods 1.2 because of their elevation, in comparison with conventional indoor combined antenna systems which typically consists of two telescopic rods mounted below or close to a UHF antenna. In such a prior art combination, there are often physical restrictions in the adjustment of the telescopic rods, and the need to avoid undesirable electrical interaction between VHF and UHF antennas. In the 2Q arrangement as shown in figure 4, such restrictions are reduced.

The combining unit for the antenna system shown in figure 4 may be achieved preferably by means of a diplexer circuit using strip-line techniques on a printed circuit card which may in addition embody the main UHF antenna elements as printed circuits.

Referring to Figure 5, line 14 represents the horizontal plane of the E-vector, i.e. for H-polarized signal reception, through the electrical centre of the antenna. Sum of the angles a and b (between this horizontal plane and the antenna structures containing the elements) is less than 180 degrees.

It can be seen from all of the above that the invent'ion has the following advantages, namely, a high level of mecsical stability and compactness which blends with the necessity for an aesthetically attractive antenna in the WO 88/04836 PCT/AU87/00429 7 home environment particularly when the antenna is used for a display purpose. The antenna provides a directional response for ghost reduction when parasitic elements are incorporated. Low cost non-rigid antenna elements such as thin metallic wires or thin aluminium films or strips may be used.

Further, the invention has horizontal and vertical beamwidth angles wide enough to allow the structure or structures to be orientated in most usage situations, or inverted, as when it is hung on a wall, to achieve both reception and decorative aims.

In the directional antenna designed with the V-shape, both outer members can provide a display capability and th:,s is necessary to give a high level of flexibility in antenna orientation.

As is usual with antennas, an impedance matching circuit or device such as a balun may be used between the antenna and television receiver. Such a circuit or device may optionally be attached to or incorporr.ed in the antenna according to the invention.

.I

Claims (3)

1. '4 directional television UHF antenna for indoor use comprising two mutually inclined planar structures connected together along a common adjacent edge wherein: one planar structure supports at least one driven antenna element consisting of a pair of folded metallic dipoles and a plurality of parasitic antenna elements in a plane close to and in front of that of the dipoles; (ii) the other planar structure supporting a substantially rectangular metallic reflector positioned away from the common adjacent edge and having metallic side shoulders extending towards the said common adjacent edge to avoid interference with the said dipoles, to maximise the gain of the said antenna as well as to minimise the overall size of the antenna; (iii) the angle between the two mutually inclined planer structures is selected to maximise the performance characteristics of the antenna over the UHF band of reception.

2. An antenna as claimed in Claim 2 wherein the angle is between 160 to 300,

3. An antenna as claimed in any one of the preceding claims wherein the planar structures serve a further display purpose. S4. An antenna as claimed in Claim 3 wherein the antenna is combined with a co-located VHF antenna. DATED this 18th day a 4pril, 1990. JOHN CHUN SING YIP and CAHTERINE WEI YUEN YIP 13 Blue Jay court West Pennant Hills NSW 2120 Australia. L 1 .i i Y: i ill