Dielectric lens apparatus

Abstract: The radiation directivity of radio waves can be controlled more easily over a wider range by using the disclosed dielectric lens. A dielectric lens element (13) having a curved surface (15) is bonded to one of the surfaces of a laminate element (12) in the shape of a flat plate in which a plurality of dielectric layers whose relative dielectric constants are different for adjacent layers are laminated. By controlling the distribution mode of the relative dielectric constants in the laminate element the radiation directivity for the entire dielectric lens apparatus (11) can be controlled; therefore, the radiation directivity can be controlled more easily over a wider range. A focal point (17) may be positioned within or at the surface of the laminate element (12), and a signal processing circuit (18) may be formed within and/or at the surface of the laminate element.

Description: The present invention relates to a dielectric lens apparatus employing a solid dielectric. More particularly, the present invention relates to a dielectric lens apparatus for use in a high frequency band. Fig. 3 shows a conventional typical dielectric lens 1. A dielectric lens 1 has a curved surface 2 which is formed into, for example, a convex surface. Such a dielectric lens 1 functions to refract radio waves 3 which enter from the curved surface 2 side so they converge at a focal point 4. However, a dielectric lens 1 such as that shown in Fig. 3 has the following problems. First, the radiation directivity of the radio waves 3 is determined substantially by the shape of the dielectric lens 1 and the dielectric constant of the dielectric which forms the dielectric lens 1. For this reason, the dielectric lens 1 arranged as shown in Fig. 3 has only a small degree of freedom concerning radiation directivity, and so it is relatively difficult to control radiation directivity. Also, since the focal point 4 is positioned outside the dielectric lens 1, if an obstacle is present between the dielectric lens 1 and the focal point 4, as a matter of course, the radio waves 3 will be shielded, causing the dielectric lens 1 not to function as a lens. EP 0420137A2 discloses two layer matching dielectrics for radomes and lenses for wide angles of incidence. The multi-layered structure has two impedance matching layers and a base member to provide an optimal transmission characteristic for the double impedance matching layer structure. The structure provides for optimal transmission of an electromagnetic signal for wide angles of incidence and displays minimal sensitivity to the polarization of the signal. US-A-5,755,820 discloses an antenna device having a dielectric sheet substrate with an antenna patch on one surface and a ground plane on the other surface. A hemispherical dielectric lense is arranged over the antenna patch. US-A-5,185,613 concerns a hybrid structure having a lens, an antenna array and a semiconductor microcircuit. The antenna array is formed on a surface of the lens or on a surface of a substrate having substantially the same refractive index as the material of the lens. Metal bump bonds provide connections between the antenna array and the semiconductor microcircuit. It is the object of the present invention to provide an improved dielectric lens apparatus having an easy to control radiation directivity and ensuring the proper functionality of the device as lens. This object is achieved by a dielectric lens apparatus according to claim 1. In the present invention, the focal point of the dielectric lens apparatus is positioned within or at the surface of the laminate element. Further, in the present invention, at least a part of a signal processing circuit may be formed within and/or on the surface of the laminate element. According to the present invention, in addition to a dielectric lens element having a curved surface, a laminate element is provided with a plurality of dielectric layers whose relative dielectric constants are different for adjacent layers. Therefore, it becomes possible to control radiation directivity by not only controlling the shape of the dielectric lens element and the dielectric constant of a dielectric which constitutes the dielectric lens element, but also by controlling the distribution of the relative dielectric constants of each dielectric layer in the dielectric element. Therefore, it is possible to widen the range of control of radiation directivity. As a result, it is possible to widen the applicable range of the dielectric lens apparatus and provide convenience in designing dielectric lens apparatus. When a laminate element is provided, the focal point of the dielectric lens apparatus can easily be positioned within or at the surface of the laminate element. When the focal point of the dielectric lens apparatus can be positioned within or at the surface of the laminate element in such a manner as described above, there is no room for an obstacle to enter the space between the focal point and the dielectric lens element, thereby making it possible to prevent radio waves from being shielded by such an obstacle. In the present invention, as described above, at least a part of a signal processing circuit can be formed within and/or on the surface of the laminate element. If at least a part of a signal processing circuit is formed within a laminate element in the manner as described above, a dielectric lens apparatus having the circuit integrated therein can be obtained, making it possible to achieve a multi-function dielectric lens apparatus. This contributes to a smaller size and higher performance electronic apparatus employing such dielectric lens apparatus. The above and further objects, aspects and novel features of the invention will more fully appear from the following detailed description when read in connection with the accompanying drawings. Fig. 1 is a sectional view illustrating a dielectric lens apparatus according to an embodiment of the present invention; Fig. 2 is a sectional view illustrating a dielectric lens apparatus according to another embodiment of the present invention; and Fig. 3 is a sectional view illustrating a conventional dielectric lens apparatus. Fig. 1 is a sectional view illustrating a dielectric lens apparatus 11 according to an embodiment of the present invention. The dielectric lens apparatus 11 comprises a laminate element 12 and a dielectric lens element 13. The laminate element 12 has a flat plate shape in which a plurality of dielectric layers 14a, ..., 14n are laminated. The relative dielectric constants of these dielectric layers 14a, ..., 14n are different for adjacent dielectric layers. In this embodiment, the relative dielectric constants are changed incrementally in such a manner as to have a stepped gradient from the topmost dielectric layer 14a to the bottommost dielectric layer 14n. Concerning each of the dielectric layers 14a, ..., 14n or one dielectric layer 14a for instance, each layer may be formed of a plurality of layers having the same relative dielectric constant in the manufacturing process therefor. Further, each of the dielectric layers 14a, ..., 14n may not have the same thickness. In the embodiment shown in the figure, not only does the laminate element 12 have a flat plate shape, but also each of the dielectric layers 14a, ..., 14n which constitute the laminate element 12 has a flat plate shape. However, each of these dielectric layers may be formed into any desired shape, for example, a shape such that they are in contact with each other via a conical-shaped or cone-shaped interface according to the desired state of refracted radio waves. On the other hand, the dielectric lens element 13 has a curved surface 15 which provides a convex surface. This dielectric lens element 13 is bonded to one of the surfaces of the laminate element 12 with the curved surface 15 facing outwards. Although in this embodiment the curved surface 15 of the dielectric lens element 13 provides a convex surface, the shape of this curved surface may be any other shape, for example, a shape which provides a concave surface or which provides a convex surface in the central portion and a concave surface in the surrounding portion. This dielectric lens apparatus 11 functions to refract radio waves 16 which enter from the curved surface 15 side so they converge at a focal point 17. In this embodiment, a design is used such that the focal point 17 is positioned at the surface of the laminate element 12. In such a dielectric lens apparatus 11, by changing the distribution mode of the relative dielectric constants in the laminate element 12, it is possible to control the radiation directivity of the radio waves 16, and it is relatively easy to obtain desired radiation directivity. This distribution mode of the relative dielectric constants can be selected as desired according to the radiation directivity to be obtained. More specifically, in this embodiment as described above, the relative dielectric constants are provided to have a gradient in such a way that the relative dielectric constants decrease in a stepped manner from the topmost dielectric layer 14a to the bottommost dielectric layer 14n; however, an inverse gradient may be provided, or rather than having relative dielectric constants varying only in one direction, the distribution mode of the relative dielectric constants can be provided such that they first increase and then decrease in the thickness direction of the laminate element 12. In this embodiment, since the focal point 17 is positioned at the surface of the laminate element 12, there is no room for an obstacle to enter the space between the focal point 17 and the dielectric lens element 13, thereby making it possible to prevent radio waves from being shielded by such an obstacle. Also, when such a focal point is positioned within the laminate element 12, similar advantages can be obtained. The dielectric lens apparatus 11 can be manufactured by applying a manufacturing method which is basically similar to that used for, for example, laminate ceramic electronic parts. More specifically, dielectric ceramic green sheets capable of providing desired relative dielectric constants for each of the plurality of dielectric layers 14a, ..., 14n which constitute the laminate element 12 and dielectric ceramic green sheets for the dielectric lens element 13 are prepared, and these ceramic green sheets are laminated and pressed. This pressing causes the contact characteristic of the plurality of ceramic green sheets to increase and molds the curved surface 15 of the dielectric lens element 13. Thereafter, by baking the ceramic green sheets, the dielectric lens apparatus 11 can be obtained. If the curved surface 15 of the dielectric lens element 13 is not properly molded in the above-described pressing process, polishing or cutting may be performed after baking to form the curved surface 15. In order to provide each of the plurality of dielectric layers 14a, ..., 14n which constitute the laminate element 12 and the dielectric lens element 13 with a desired relative dielectric constant, a method of mixing resins with dielectric ceramic powder may be used. In such a case, a sheet in which a heat-curing resin, such as polypropylene, polyethylene or polystyrene, is mixed into the dielectric ceramic powder at a predetermined ratio is prepared to make each of the dielectric layers 14a, ..., 14n and the dielectric lens element 13, and these sheets are fuzed, resulting in a monolithic dielectric lens apparatus 11. Fig. 2 is a sectional view illustrating a dielectric lens apparatus 11a according to another embodiment of the present invention. Since the dielectric lens apparatus 11a shown in Fig. 2 is provided with elements common to those of the dielectric lens apparatus 11 shown in Fig. 1, these common elements are given the same reference numerals and therefore, a description thereof is omitted. In the dielectric lens apparatus 11a shown in Fig. 2, the focal point 17 is positioned at the interface between a dielectric layer 14m and a dielectric layer 14n which constitute the laminate element 12. An antenna 18, such as a patch antenna, which operates as a primary radiator is formed by patterning in the portion where the focal point 17 is positioned. Further, a grounding electrode 19 is formed on the outer surface of the laminate element 12 in such a manner as to face the antenna 18. Since the antenna 18 is formed inside the laminate element 12 as described above, the dielectric lens apparatus 11a can be made to function as a dielectric lens antenna. If a circuit is integrated into the dielectric lens apparatus by forming at least a part of a signal processing circuit, such as the above-described antenna 18, within and/or on the surface of the laminate element 12, the dielectric lens apparatus can be made multi-functional. Examples of signal processing circuits which can be integrated in the manner described above include, in addition to that described above, an amplification circuit, and a frequency conversion circuit. Further, such a circuit may be formed of a circuit pattern as in the antenna 18, or may be formed by adding discrete electronic parts on this circuit pattern. The positions at which these circuit elements are arranged can be selected as desired within or on the surface of the laminate element, and consideration is given not to hinder the propagation of radio waves in selecting the position of the arrangement.

Claims: A dielectric lens (11) apparatus, comprising: a laminated element (12) comprising a plurality of laminated dielectric layers (14a,...,14n) fused together and having relative dielectric constants which are different for at least some adjacent layers; and a dielectric lens element (13) which has a curved surface (15) and which is bonded to one of the surfaces of said laminated element with said curved surface facing outwards; wherein the laminated element (12) and the lens element (13) coact to form a focal point (17) of said dielectric lens apparatus which is positioned within or at the surface of the laminated element (12). The dielectric lens apparatus (11) of claim 1, wherein said relative dielectric constants of said laminated dielectric layers (14a,...,14n) and said curved surface of said dielectric lens element are selected to coact to provide said focal point (17). The dielectric lens apparatus of any of the preceding claims, further comprising a signal processing circuit at least part of which is within and/or on the surface of said laminated element (12). The dielectric lens apparatus of claim 3, wherein said signal processing circuit part comprises an antenna (18). The dielectric lens apparatus of claim 4, wherein said antenna (18) is within said laminated element (12) and a ground conductor (19) is formed on a surface of said laminated element (12) so as to coact with said antenna. The dielectric lens apparatus of any of the preceding claims, wherein said shape of said dielectric lens element is convex and faces outwards. The dielectric lens apparatus of any of the preceding claims, wherein each said dielectric layer (14a, ..., 14n) has the same thickness. The dielectric lens apparatus of any of the preceding claims, wherein the laminated element (12) has a flat shape. The dielectric lens apparatus of any of the preceding claims, wherein each dielectric layer (14a ,..., 14n) in the laminated element has a flat shape. The dielectric lens apparatus of any of the preceding claims, wherein each adjacent pair of dielectric layers (14a, ..., 14n) have different respective dielectric constants. The dielectric lens apparatus of any of the preceding claims, wherein said respective dielectric constants of said dielectric layers (14a, ..., 14n) increase from layer to layer in a thickness direction throughout said laminated element (12). The dielectric lens apparatus of any of the preceding claims, wherein said respective dielectric constants of said dielectric layers (14a, ..., 14n) increase from layer to layer in a thickness direction in part of said laminated element (12) and decrease from layer to layer in said direction in another part of said laminated element (12).

Inventors: HIGASHI KAZUTAKA, ISHIKAWA YOHEI, SAITOH YASUAKI, YAMADA HIDEAKI, HIGASHI, KAZUTAKA, ISHIKAWA, YOHEI, SAITOH, YASUAKI, YAMADA, HIDEAKI
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H01Q15
IPC codes: H01Q19, H01Q15