JP2005534242A - Thin patch antenna - Google Patents

Abstract

The present invention relates to a thin plate antenna, which includes a radiating element (50), an antenna feeding part connected to the radiating element, and a distance e from the element that is substantially parallel to the radiating element. And a conductive surface (66) arranged at a distance. The conductive surface is equipped with at least one slot (68) facing the radiating element and comprises a conductive connection between the conductive surface and the radiating element.

Description

  The present invention relates to a plate antenna having a small thickness.

  Currently, PIFA type and similar plate antennas are used in the manufacture of portable radiotelephones. Actually, the antenna is completely disposed in the housing of the mobile phone, and its size is relatively small.

The attached FIG. 1 is a schematic vertical sectional view of such an antenna. This consists of a radiating element 10 designed according to the wavelength used and the desired impedance (typically 50Ω). The antenna also has a ground plane 12 substantially parallel to the radiating element 10. A short circuit 14 is formed between the radiating element 10 and the ground plane 12. In addition, the antenna is generally powered by a coaxial cable 16, with the central conductor 16a of the coaxial cable 16 being electrically connected to the radiating element 10 and the shield 16b being connected to the ground plane. In the case of such an antenna, it is necessary to supply a minimum spacing e in order to ensure that the antenna operates satisfactorily. Typically, when the dielectric between the radiating element and the ground plane is air and the frequency is less than 2 GHz, the minimum spacing e is about 7 millimeters (mm) to 10 mm.

If an attempt is made to reduce the distance e between the radiating element and the ground plane, the achieved antenna is limited in operation. That is, there is a restriction that the pass band cannot be allowed. In particular, it is difficult to achieve a distance e of less than 5 mm for frequencies below 2 GHz, i.e. in the frequency band commonly used in radiotelephones, in particular in GSM systems.

In portable radio telephones that are evolving day by day, the overall thickness of the radio telephone must be reduced more and more. The antenna is also required to have a reduced thickness and in particular a distance e considerably shorter than 7 mm, for example about 2 mm to 3 mm.

  Also, to save space inside the radio telephone, the metallization on the printed circuit board (PCB), ie the shield etc., constitutes the ground plane of the radio telephone, while it consists of the radiating element, the short circuit 14 and the feeding cable 16. There is also a need for a specification in which the assembly is placed directly on the printed circuit.

  Thus, it has an overall thickness of 5 mm or less, is acceptable and spans multiple frequency bands corresponding to those conventionally used in wireless telephones, especially computer modems for portable computers, PCMCIA cards, PDAs and others. There is a real need for an antenna that exhibits an operational state capable of functioning.

  Accordingly, it is an object of the present invention to provide a plate antenna having a passband with reduced thickness and conforming to current effective standards.

Such an object of the present invention is achieved by a thin plate antenna. The plate type antenna
A radiating element;
An antenna feeder connected to the radiating element;
A conductive surface substantially parallel to the radiating element and spaced from the element by a distance e , the conductive surface having at least one slot open substantially facing the radiating element A conductive surface;
A conductive connection between the conductive surface and the radiating element;
It is characterized by providing.

  Note that the term “slot” is used in the present specification to include any concave shape in the conductive surface regardless of its outer shape.

  Antennas that fall within the above definition are suitable for use in portable radiotelephones and the like that operate in commonly used frequency bands of less than 2 GHz, particularly in GSM systems, regardless of thickness reduction, eg, about 3 mm. Allows acquisition of a suitable passband. This result is achieved mainly because in addition to the electric field generated by the radiating element, the magnetic field is induced by the presence of a slot provided on the electric field surface facing the radiating element. Together, these two fields in quadrature produce an electromagnetic wave corresponding to the wave used in a standard thickness, ie, an antenna of about 7 mm to 10 mm.

  The term “open slot” is used to encompass a slot that is open to the periphery of the conductive surface. In other words, when the slot is open, the slot is not completely surrounded by the conductive element. Since the slot is open, radiation from the slot is avoided and the operation of the antenna is greatly improved.

  Preferably, the shape of the open slot is substantially the same as the shape of the radiating element.

  In one embodiment of the present invention, the slot shape substantially corresponds to the outer shape of the radiating element.

  In a preferred embodiment of the antenna, the conductive surface comprises a conductive plate, and the antenna further comprises an insulating mechanical structure on which the radiating element, the conductive plate and the conductive connection are all fixed.

  The assembly can be fixed directly on the printed circuit or can be appropriately connected to the conductive tracks of the printed circuit.

  Other features and advantages of the present invention will become more apparent from the following description of various embodiments that do not limit the invention.

  Next, a first embodiment of the antenna according to the present invention will be described with reference to FIGS.

  In this embodiment, as is apparent from FIG. 2B, the radiating element 50 is joined by two parallel main portions 52, which are joined by a loop 56 at one end and extended by a branch 58 at the opposite end of the straight portion 52. 54. The shape of the radiating element is determined by the operating frequency of the antenna and the desired impedance. Each branch 58 is extended by two connection tabs 60 and 62 for antenna and short circuit, both tabs being fixed to the double connection 64.

FIG. 2A shows a conductive surface 66 having a slot 68. The slot 68 is similar in shape to the shape of the radiating element 50 but need not be identical. This slot is composed of slot portions 52 ', 54', 56 'and 58'. The slot branch 58 ′ is extended with an open portion 70 to the peripheral portion 66 a of the conductive surface 66 in order to achieve an open slot in the sense defined above. The slot portion 70 is located between the connection areas 72 and 74.
Connection areas 72 and 74 correspond to establishing an electrical short between the radiating element and the conductive surface 66 and feeding the antenna, respectively. The double connection portion 64 constitutes a means for mechanically fixing the radiating element to the conductive surface. Thereby, the radiating element is held parallel to the conductive surface at a distance e ₁ of about 2 mm from the conductive surface, in any case less than 5 mm.

  The conductive surface 66 can also be constituted by a conductive plate or by metallization on an insulating substrate.

  FIG. 3 shows a curve I that firstly gives the standing wave ratio (SWR) of the reference antenna as a function of the frequency F, and secondly the voltage standing wave ratio (VSWR) of the antennas of FIGS. Curve II is shown as a function of frequency. The reference antenna corresponding to the curve I is the same antenna as shown in FIGS. 2A to 2C except that the conductive surface 66 that forms the ground plane has no slot 68.

  FIG. 3 clearly shows that the reference antenna corresponding to curve I exhibits a passband. This passband is greatly reduced and has a much lower amplification factor than the antenna according to the invention corresponding to curve II.

  FIG. 6 shows another embodiment of the antenna according to the present invention. This embodiment is close to the embodiment shown in FIGS. 2A, 2B and 2C.

FIG. 6 shows a conductive surface 140 made of several metallizations formed on, for example, an insulating substrate 142. The conductive surface 140 is supplied with a slot 144 described in detail later. This figure similarly shows the radiating element 146 arranged in a plane substantially parallel to the conductive surface 140. In this example, the radiating element 146 includes a first branch 148 corresponding to the first frequency band, a second branch 150 corresponding to the second frequency band, and a base 152. The second branch 150 includes, for example, a first portion 150a that is substantially parallel to the first branch 148 and a second portion 150b that is drawn from the first portion 150a. Further, the second branch 150 has a base 152 common to both branches. The radiating element 146 can be formed by separating a thin conductive metal sheet. In this example, the radiating element 146 is mounted on the duplex connector 154. This connector provides a first short connection between the radiating element and the conductive surface 140 and a second connection between the radiating element and the antenna cable 156. The distance e between the radiating element 146 and the conductive surface 140 is 2 mm.

  The shape 144a of the slot 144 substantially corresponds to the outer shape of the radiating element 146. In the example shown in FIG. 6, the shape 144a is rectangular. This slot is preferably arranged in a state substantially facing the radiating element. The slot 144 is suitably extended by an extension 158 that is open to the peripheral portion 140a of the conductive surface 140 so as to form an open slot in the sense defined above.

  As described above, the conductive surface can include a plurality of slots associated with the shape of the radiating element. Preferably, such a plurality of slots are open or at least one slot is open.

  Next, another modified embodiment of the antenna according to the present invention will be described with reference to FIG. In this embodiment, the structure of the antenna is the same as that described above, but a mechanical structure for configuring the antenna module is added. The mechanical structure is made of an insulating material, preferably a moldable plastic material. The entire mechanical structure is illustrated by reference numeral 80 and is generally cap-shaped with four side walls such as top walls 82 and 84. The radiating element is shown schematically as 86 and is preferably embedded within the plastic material comprising the top wall 82. This radiating element may have the shape shown in FIG. 2B. The top wall 82 faces the part 86a of the radiating element and forms connection recesses 88 and 90. Furthermore, the mechanical structure 80 forms a housing 92. In the housing 92, the double connection 94 can be clipped or mounted in a suitable manner. The connection portion 94 functions as an antenna connection portion and a short-circuit connection portion. For this purpose, the connecting part 94 includes two upper contacts 96 and 98 penetrating into the recesses 88 and 90 and two lower contacts 100 and 102.

  The bottom portion of the side wall 84 of the cap 80 includes a rim 104 formed to be thick so as to be fixed to the periphery of the conductive plate 106 constituting the conductive surface. The open slot 108 formed in the plate 106 is shown in a simplified manner. Furthermore, the plate 106 has a flexible contact 110 for passing through the housing 92 to obtain an electrical connection with the shorting contact 102, thereby providing a connection with the radiating element.

  FIG. 4 also shows a portion of the printed circuit 112 having conductive tracks 114. The conductive tracks 114 first constitute an electrical ground and secondly constitute an antenna conductor. These conductive tracks 114 are connected to the electrical contacts 100 and 102 of the connecting portion 94.

It is clear that the assembly consisting of the cap 80 with the connection 94 can be fixed directly to the surface of the printed circuit 112 in order to obtain the electrical connection described above and to mechanically fix the cap on the printed circuit. is there. Of course, in this embodiment, the distance e ₁ between the radiating element 86 and the conductive plate 106 is about 2 mm.

FIG. 5 shows a second variant embodiment of the antenna according to the invention. This antenna is manufactured as a printed circuit 120. In this figure, it can be confirmed that the insulating substrate 122 of the printed circuit having the thickness e ₂ of about 2 mm exists. On the first surface 122a of the insulating substrate 122 is a first metallization 124 that forms a radiating element that can be shaped as shown in FIG. 2B or FIG. Further, a second metallized 126 is formed on the second surface 122b of the insulating substrate 122 and constitutes a conductive surface of the antenna. This conductive surface is naturally provided with one or more open slots 128. The open slot 128 faces the radiating element 124 and has an outer shape substantially the same as or corresponding to the shape of the radiating element. The short circuit is established through the first plated through hole 130 connected to the metallized 126 through the insulating substrate 122. Another metallization 130 is formed on the surface 122b of the insulating substrate 122, and constitutes an antenna conductor. The antenna conductor 130 is connected to the radiating element 124 by the second plated through hole 134.

  This example is an antenna having exactly the same features as described above, except that the dielectric between the radiating element 124 and the conductive surface 126 is not air and is the material from which the printed circuit insulating substrate 122 is manufactured. provide.

It is a figure which shows the conventional PiFa type | mold antenna. 2A is a plan view showing a conductive surface of the antenna according to the first embodiment of the present invention, FIG. 2B is a plan view showing a radiating element corresponding to FIG. 2A, and FIG. 2C is a plan view of FIGS. 2A and 2B. It is a longitudinal cross-sectional view which shows the antenna incorporating a component. 3 is a graph showing two curves corresponding to a reference antenna and the antennas of FIGS. It is a longitudinal cross-sectional view of the antenna which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the antenna which concerns on 2nd Embodiment. It is a perspective view of the antenna which concerns on other embodiment.

Claims (10)

A thin plate antenna,
A radiating element;
An antenna feeder connected to the radiating element;
A conductive surface substantially parallel to the radiating element and spaced from the element by a distance e, the conductive surface having at least one slot open substantially facing the radiating element A conductive surface;
A conductive connection between the conductive surface and the radiating element;
A plate-like antenna comprising: It is a plate-shaped antenna of Claim 1, Comprising:
An antenna, wherein a radiating element has a predetermined shape, and the one or more slots have a shape substantially equal to a predetermined shape of the radiating element. It is a plate-shaped antenna of Claim 1, Comprising:
The antenna is characterized in that the shape of the slot corresponds to the outer shape of the radiating element. It is a plate-shaped antenna in any one of Claim 1 to 3,
The antenna according to claim 1, wherein the conductive surface comprises a conductive plate. The plate antenna according to claim 4, further comprising:
An antenna comprising an insulating mechanical structure having all of the radiating element, the conductive plate, and the conductive connection portion fixed thereon. The plate-shaped antenna according to claim 5,
The antenna is characterized in that the mechanical structure is made of a moldable material, and the structure has a top portion in which a radiating element is embedded. The plate antenna according to claim 5 or 6, further comprising:
A connector element mounted on the mechanical structure for electrically connecting the radiating element to the antenna feeder and for forming a short circuit between the radiating element and ground; Characteristic antenna. The plate-shaped antenna according to claim 7,
The antenna according to claim 1, wherein the mechanical structure comprises at least two side walls having the conductive plate fixed parallel to the radiating element. The plate-shaped antenna according to any one of claims 1 to 4,
An insulating substrate for the printed circuit;
A first metallization formed on a first surface of the substrate to form a radiating element;
A second metallization formed on the second surface of the insulating substrate to form a conductive surface;
Two electrical links that pass through the substrate and constitute the electrical connection and the antenna feed,
The antenna according to claim 1, further comprising: The plate-shaped antenna according to any one of claims 1 to 9,
An antenna having an operating frequency of less than 2 GHz.

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