WO2015079407A1

WO2015079407A1 - Antenna

Info

Publication number: WO2015079407A1
Application number: PCT/IB2014/066396
Authority: WO
Inventors: Antonie Craig ALBERTS
Original assignee: Green Star Hi-Tech Electronics (Pty) Ltd
Priority date: 2013-11-27
Filing date: 2014-11-27
Publication date: 2015-06-04

Abstract

This invention relates to an antenna 10 which comprises a dielectric substrate 12, a first radiating sheet element 14 adhered on an operatively upper surface 12.1 of the dielectric substrate 12 and a first feed line 16 adhered on the upper surface 12.1 and connected to the first radiating element 14 to feed it. The antenna 10 further includes a second radiating sheet element 18 disposed and adhered on a position of an operatively lower surface 12.2 of the dielectric substrate 12 directly opposite to the radiation element 14. The second radiating element 18 is thus spaced from and faces the first radiating element 14. The first and second radiating elements 14 and 18 are electrically connected to each other by means of a second feed line 20. The arrangement is such that the antenna 10 includes at least two radiating planar levels being electrically connected to each other through the dielectric substrate 12.

Description

ANTENNA

FIELD OF THE INVENTION This invention relates to an antenna. More specifically, but not exclusively, the invention relates to an antenna, such as a patch, microstrip, or any planar type of antenna.

BACKGROUND TO THE INVENTION

Patch antennas are well known and widely used. In their simplest form, they consist of a generally flat radiating element or patch positioned over a larger ground plane. Both the radiating patch and ground plane are made from conductive materials. There are many applications for antennas for which it is important for the antenna to be as small as possible. Unfortunately, due the nature of antennas with a reduction in size, their efficiency generally also reduces. In this regard, it is known to incorporate, at least in part, a fractal design in the radiating elements of antennas in order to reduce their size without negatively affecting their performance.

A fractal antenna is an antenna that uses a fractal, self-similar design to maximize the length, or increase the perimeter (on inside sections or the outer structure), of material that can receive or transmit electromagnetic radiation within a given total surface area or volume. Such fractal antennas are also referred to as multilevel and space filling curves, but the key aspect lies in their repetition of a motif over two or more scale sizes, or "iterations". For this reason, fractal antennas are very compact, multiband or wideband, and have useful applications in cellular telephone and microwave communications. A fractal antenna's response differs markedly from traditional antenna designs, in that it is capable of operating with good-to-excellent performance at many different frequencies simultaneously. Normally standard antennas have to be "cut" for the frequency for which they are to be used, and thus the standard antennas only work well at that frequency. This makes the fractal antenna an excellent design for wideband and multiband applications. In addition the fractal nature of the antenna shrinks its size, without the use of any components, such as inductors or capacitors.

OBJECT OF THE INVENTION It is therefore an object of the present invention to provide an antenna with which the aforesaid disadvantage can be overcome or at least minimised, and/or which provides a useful alternative to known antennas.

SUMMARY OF THE INVENTION

According to the invention there is provided an antenna, comprising:

- a first radiating sheet element;

- a first feed line connected to the first radiating sheet element;

- a second radiating sheet element spaced from and facing the first radiating sheet element; and - a second feed line electrically connecting the first and second radiating sheet elements to each other,

- the antenna does not require a specific ground plane or counterpoise to achieve resonance,

- the fractal pattern described is not specifically necessary to achieve resonance but the perimeter of the active area will define the points of resonance, the arrangement being such that the antenna includes at least two radiating levels being electrically connected to each other. It is well known that antennas are reciprocal devices which may be used for either transmitting signals or receiving signals or both. It will hence be appreciated that when in this specification any term is used in one context, for example in a receiving context, where appropriate the term must be construed to include the term in the reciprocal context of transmitting.

According to an example embodiment of the invention, there may be a dielectric material located between first and second radiating sheet elements. Preferably, the dielectric material may be in the form of a dielectric substrate. The dielectric substrate may be rigid, or resiliently deformable.

There is provided for the first radiating sheet element and the first feed line to be adhered on an operatively upper surface of the dielectric substrate, and for the second radiating sheet element to be adhered on an opposing operatively lower surface of the dielectric substrate. The first and second radiating sheet elements may be flat.

According to an example embodiment of the invention, the antenna may further include a third radiating sheet element facing the first radiating sheet element and spaced from the first radiating sheet element in a direction opposite that of the second radiating sheet element, the first and third radiating sheet elements being electrically connected to each other by means of a third feed line.

There may be a second dielectric material located between the first and third radiating sheet elements. Preferably, the second dielectric material may be in the form of a second dielectric substrate. The second dielectric substrate may be rigid or resiliently deformable.

There is provided for the first radiating sheet element and the first feed line to be adhered on an operatively lower surface of the second dielectric substrate, and for the third radiating sheet element to be adhered on an opposing operatively upper surface of the second dielectric substrate.

The third radiating sheet element may be flat.

According to at least some embodiments of the invention, the first radiating sheet element may have a fractal type of appearance being a predetermined fractal-type geometric pattern. The fractal-type geometric pattern may be in the form of repeated geometric sections with reoccurring patterns.

The repeated geometric sections may be in the form of multiple repeated triangles in reducing size, repeated to allow for resonance at specific frequencies where each repeated triangular structure is fully enclosed directly opposite and operatively above the second radiating sheet element.

At least part of the fractal-type geometric pattern may be directly opposite and operatively above the second radiating sheet element.

In at least some embodiments of the invention, the second radiating sheet element may have a substantially uniform shape along its length. In further embodiments of the invention, the second radiating sheet element may include at least one or more cut- outs. In still further embodiments of the invention, the antenna may include a plurality of radiating sheet elements being similar to the second radiating sheet element in that they are spaced from and face the first radiating sheet element.

The first feed line may be in the form of a meander line located directly opposite and operatively above the second radiating sheet element, which may serve to capacitively load the antenna.

There is provided for the antenna to include a plurality of first and/or second feed lines. The second feed line may be located at a position on the first radiating sheet element being any one or more of distal, intermediate or proximal to that of the first feed line. The second and third feed lines may each be in the form of a via.

Multiple repeated antennas may be provided on the same substrate, with dedicated feed lines, in order to increase directionality and gain of the antenna system. These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described below, by way of non-limiting examples only, and with reference to the accompanying drawings in which:

Figure 1 is a perspective view from above of an antenna according to a first embodiment of the invention; Figure 2 is a plan view of the antenna of figure 1 ;

Figure 3 is a side view of the antenna of figure 1 ;

Figure 4 is an exploded perspective view from above of the antenna of figure 1 ; Figure 5 is a side view of an antenna according to a second embodiment of the invention;

Figure 6 is a side view of an antenna according to a third embodiment of the invention;

Figure 7 is a plan view of an antenna according to a fourth embodiment of the invention; and Figure 8 is a perspective view from above of an antenna arrangement according to the invention.

DETAILED DESCRIPTION OF THE INVENTION With reference to the drawings, in which like features are indicated by like numerals, an antenna according to the invention is generally indicated by reference numeral 10, and an antenna arrangement according to the invention is generally indicated by reference numeral 100 in figure 8. Figures 1 to 4 show a first embodiment of the antenna 10 which comprises a dielectric substrate 12, a first or primary radiating sheet element 14 adhered on an operatively upper surface 12.1 of the dielectric substrate 12 and a first or primary feed line 16 adhered on the upper surface 12.1 and connected to the first radiating element 14 to feed it. The antenna 10 further includes a second or secondary radiating sheet element 18 disposed and adhered on a position of an operatively lower surface 12.2 of the dielectric substrate 12 directly opposite to the radiation element 14. The second radiating element 18 is thus spaced from and faces the first radiating element 14. The first and second radiating elements 14 and 18 are electrically connected to each other by means of a second or secondary feed line 20 in the form of a via. The arrangement is such that the antenna 10 includes at least two radiating planar levels being electrically connected to each other through the dielectric substrate 12.

The dielectric substrate 12 could be of any suitable substrate known in the art, including rigid and resiliently deformable (soft) substrates. The thickness of the substrate 12 could be varied in order to adjust the resonance frequency bands of the antenna 10. The loading between the first and second radiating elements 14 and 18 enables resonance at frequencies well below one tenth of a wavelength. The first feed line 16 is in the form of a meander line, the majority of which is located directly opposite and operatively above the second radiating element 18, which serves to capacitively load the antenna 10. This assists to further reduce the size of the antenna 10 without adversely affecting its performance. It should be appreciated that in other embodiments of the invention, the first feed line 16 could be any suitable transmission line, implemented on the relevant substrate or otherwise, with the required impedance.

As stated previously, the first and second radiating elements 14 and 18 are conductively connected to each other by the second feed line 20. Such a secondary feed line 20 between the separate layers of the radiating planar levels could be implemented with vias of other suitable methods applicable to the specific fabrication technology. According to the example embodiment shown, the second feed line 20 is located on an end of the first radiating element 14 proximal to that of the first feed line 16.

The first sheet radiating element 14 is planar/flat and has a fractal type of appearance which is a predetermined fractal-type geometric pattern. The fractal-type geometric pattern of the radiation element 14 increases the perimeter of the first radiating element 14 and is in the form of repeated geometric sections with reoccurring patterns. More particularly, the repeated geometric sections are in the form of multiple repeated triangles in reducing size. The repeated triangles are replicated along the length of the first radiating element 14 to allow for resonance at specific frequencies where each repeated triangular structure is fully enclosed directly opposite and operatively above the second radiating element 18. Each geometric repetition is ordered in even or odd multiples of the major radiating structure. It should be appreciated that the repeated triangular structure does not have to be fully enclosed above the second radiating element 18 in all embodiments of the invention. As is best shown in figure 2, the second radiating element 18 is rectangular in shape and thus has a substantially uniform shape along its length. This figure further shows that the first radiating element 14 is enclosed by the second radiating element 18.

The first and second radiating elements 14 and 18 are made from conductive materials. The radiation plane 18 disposed on the lower surface 12.2 of the dielectric substrate 12 could be a first radiation plane and the antenna could include a plurality of similar radiation planes disposed on the lower surface of the dielectric substrate (not shown).

Figure 5 shows a side view of an antenna 10A according to a second embodiment of the invention. The antenna 10A is similar to the antenna 10 described above save for the differences addressed here below. The antenna 10A includes a plurality of separate second radiating elements 18.1 and 18.2 on the operatively lower surface 12.2 of the substrate 12, with each being electrically connected to the first radiating element 14 by way of respective second feed elements 20.1 and 20.2. It should be appreciated that any number of second radiating elements 18 could be used.

Figure 6 illustrates a side view of an antenna 10B according to a third embodiment of the invention. The antenna 10B is similar to the antenna 10 described above save for the differences addressed here below. The antenna 10B includes a second dielectric material substrate 12.10 which is staggered in relating to the substrate 12 so to sandwich the first radiating element 14 between the substrates 12 and 12.10. The substrates 12 and 12.10 are similar.

The antenna 10B further includes a third flat radiating sheet element 22 adhered on the operatively upper surface 12.2 of the substrate 12.10 and is electrically connected to the first radiating element 14 by means of a third feed line 24 in the form if a via. The first radiating sheet element 14 and first feed line 16 are adhered on an operatively lower surface of the substrate 12.10. The second and third radiating elements 18 and 22 are thus spaced from the first radiating element 14 in opposite directions.

Figure 7 illustrates a perspective view from above of an antenna 10C according to a third embodiment of the invention. The antenna 10C is similar to the antenna 10 described above save for the differences addressed here below. The first radiating element of the antenna 10C does not have a fractal-type geometric pattern. Also, its second feed line 20 is located on a distal end region of the first radiating element 14 to where the first feed line 16 is located. Further, its second radiating sheet element 18 includes a cut-out 26. According to the example embodiment shown, the cut-out 26 extends substantially the width of the second radiating sheet element 18. It should be appreciated that in further embodiments of the invention the cut-out 26 could be of any shape and size, and there may be a plurality thereof, which may be repetitive, or not.

Referring particularly to figure 8, an antenna arrangement 100 is shown which includes multiple repeated antennas 10 provided on the same substrate 12, with dedicated feed lines, in order to increase directionality and gain of the antenna arrangement 100. It should be appreciated that the orientation of the repeated antennas 10 could vary and they do not have to extend substantially to each other. For example, they could be rotated by any degree in relation to each other.

The invention provides an antenna 10 that does not require a specific ground plane, and could have a plurality of resonating planes (not shown) sandwiched in the substrate 12. However, a ground plane (also not shown) could be provided to alter the impedance of the antenna 10 to accommodate longer wavelengths, with counterpoise conductive sheets able to alter the input impedance of the antenna 10 shifting resonance points lower. A feed point from where the first feed line 16 feeds the antenna 10 is not defined at a specific position on the antenna 10. The resonance of the antenna can be guaranteed without a specific feed point with only some changes in the input impedance at the given frequency and the feed point can therefore be located at any point on the active elements.

The multiband resonance frequency of the antenna 10 enables the use of a single transmission line to act as the transmission medium for multiple transceivers acting in different frequency bands with a 'single-to-multiport' matching network. The antenna 10 could be matched to specific bands using conventional matching techniques.

It is foreseen that the antenna 10 could be tuned to receive signals at two or more cellular or ism bands, as required. The antenna 10 has multiple frequency band and broadband characteristics.

It is further foreseen that the antenna 10 of the present invention reduces antenna size drastically, whilst offering performance similar to its larger counterparts. Accordingly, the antenna design of the present invention offers improved performance, by having an antenna that exists over multiple planar levels within the substrate with two or more conductive layers that may or may not reply on counterpoise. The dual radiating elements permit the antenna to excite higher order modes.

It will be appreciated that variations in detail are possible with an antenna according to the invention without departing from the scope of the appended claims. For example, the radiating sheet elements 14, 18 and 22 may be curved. Also, there may be more than one second feed line 20 extending between the first and second radiating elements 14 and 18 and located anywhere on the first radiating element 14. The second fee lines are not limited to vias.

Claims

An antenna comprising

a first radiating sheet element;

a first feed line connected to the first radiating sheet element;

a second radiating sheet element spaced from and facing the first radiating sheet element; and

a second feed line electrically connecting the first and second radiating sheet elements to each other,

the arrangement being such that the antenna includes at least two radiating levels being electrically connected to each other.

The antenna according to claim 1 , including a dielectric material located between first and second radiating sheet elements.

The antenna according to claim 2, wherein the dielectric material is in the form of a dielectric substrate which could be either rigid, or resiliently deformable.

The antenna according to claim 3, wherein the first radiating sheet element and the first feed line are adhered on an operatively upper surface of the dielectric substrate, and the second radiating sheet element is adhered on an opposing operatively lower surface of the dielectric substrate.

The antenna according to any one of the preceding claims, wherein the first and second radiating sheet elements are flat.

6. The antenna according to any one of the preceding claims, wherein the first feed line is in the form of a meander line located directly opposite the second radiating sheet element, which serves to capacitively load the antenna.

The antenna according to any one of the preceding claims, wherein the second feed line is located at a position on the first radiating sheet element which is any one of distal, intermediate or proximal to that of the first feed line.

The antenna according to any one of the preceding claims, wherein the second feed line is in the form of a via.

The antenna according to any one of the preceding claims, including a third radiating sheet element facing the first radiating sheet element and spaced from the first radiating sheet element in a direction opposite that of the second radiating sheet element, the first and third radiating sheet elements being electrically connected to each other by means of a third feed line.

10. The antenna according to claim 9, including a second dielectric material located between the first and third radiating sheet elements.

1 1 . The antenna according to claim 10, wherein the second dielectric material may be in the form of a second dielectric substrate which could be either rigid or resiliently deformable. 12. The antenna according to claim 1 1 , wherein the first radiating sheet element and the first feed line are adhered on an operatively lower surface of the second dielectric substrate, and the third radiating sheet element is adhered on an opposing operatively upper surface of the second dielectric substrate.

13. The antenna according to any one of claims 9 to 12, wherein the third radiating sheet element is flat.

14. The antenna according to any one of claims 9 to 13, wherein the third feed line is in the form of a via. 15. The antenna according to any one of the preceding claims, wherein the first radiating sheet element has a fractal type of appearance being a predetermined fractal-type geometric pattern.

16. The antenna according to claim 15, wherein at least part of the fractal-type geometric pattern is directly opposite and operatively above the second radiating sheet element.

17. The antenna according to claim 15 or 16, wherein the fractal-type geometric pattern is in the form of repeated geometric sections with reoccurring patterns.

18. The antenna according to claim 17, wherein the repeated geometric sections is in the form of multiple repeated triangles in reducing size, repeated to allow for resonance at specific frequencies where each repeated triangular structure is fully enclosed directly opposite and operatively above the second radiating sheet element.

19. The antenna according to any one of the preceding claims, wherein the second radiating sheet element has a substantially uniform shape along its length.

The antenna according to any one of claims 1 to 18, wherein the second radiating sheet element include at least one or more cut-outs.

The antenna according to any one of the preceding claims, including a plurality of radiating sheet elements being similar to the second radiating sheet element in that they are spaced from and face the first radiating sheet element.

22. An antenna arrangement comprising the antenna according to any one of the preceding claims provided adjacent each other on the same substrate.