Antenna unit

Abstract: The antenna unit (10) comprises an antenna body (11,21) and a power radiation electrode (12). The antenna body (11,21) comprises a rectangular-prism-like substrate (13,23) comprising a dielectric material, whose major ingredients are e.g., barium oxide, aluminum oxide and silica. A power supply conductor (14) is provided in the substrate (13,23) and is made of copper or copper alloy and is wound in a spiral in the direction of height of the substrate (13,23). A power supply terminal (19) for applying a voltage to the power supply conductor (14) is provided on a surface of the substrate (13,23). Further, a power radiation electrode (12), which comprises, e.g., a nearly rectangular metallic plate made of copper, copper alloy or aluminum, is provided on the surface of the substrate (13,23) of the antenna body (11,21). This power radiation electrode (12) is electrically isolated from the power supply conductor.

Description: The present invention generally relates to an antenna unit and, more particularly, to an antenna unit for use in a mobile communication system and in a local area network (LAN). Fig. 10 is a side view of a conventional tip antenna. The tip antenna 50 consists of: a rectangular-prism-like insulator 51 formed by stacking up insulating layers (not shown) made of powdery insulating materials such as alumina and steatite; a conductor 52 which is made of silver or silver-palladium alloy or the like and is formed like a coil in the insulator 51; a magnetic element 53 which is made of magnetic powder such as ferric powder and is formed inside the insulator 51 and the coil-like conductor 52; external connecting terminals 54a and 54b which are made to adhere and are baked in such a manner as to stick to the lead-out end (not shown) of the conductor 52 after the firing of the insulator 51. Namely, the tip antenna 50 is configured so that the coil-like conductor 52 is wound around the magnetic element 53 and a space therearound is filled with the insulator 51. Further, by using a material having a low relative permeability as the magnetic element 53, a tip antenna 50 which has a low resonance frequency of tens to hundreds MHz can be produced. A similar antenna in e.g. disclosed in JP-A-59017705. However, the aforementioned conventional tip antenna has a problem in that when produced as a small-sized antenna having a low resonance frequency, the gain and bandwidth thereof are degraded. EP 0 473 981 A discloses an integrated circuit card for a data processing device having a patch antenna provided on a surface of the card and which is connected by microstrip lines for impedance conversion to respective antenna receiving and transmitting circuits. US-A-5,386,214 relates to an electronic circuit device having a printed circuit board on which a circuit pattern is formed and on which components are mounted. On a second surface a coupling stub is formed which is connected to the circuit pattern and a plane antenna having an antenna element formed on a first surface of a dielectric substrate is placed on the second surface of the printed circuit board. US-A-5,185,613 discloses a hybrid structure having a lens, an antenna array and a semiconductor microcircuit wherein the antenna array is formed on a surface of the lens or on a surface of the substrate and wherein the respective antennas are in turn connected by bump bonds to the microcircuit. US-A-4,888,597 discloses a millimeter and submillimeter wave antenna wherein the antenna structure includes a horn disposed on a substrate for focussing electromagnetic energy with respect to an antenna. It is the object of the present invention to provide an antenna unit which has a high gain and a wide bandwidth at a low resonance frequency. This object is achieved by an antenna unit according to claim 1. The present invention provides an antenna unit comprising an antenna body having a substrate, the substrate having a first main surface and a mounting surface parallel to the first main surface, and a side surface connecting the first main surface and the mounting surface, the substrate comprising at least one of a dielectric material and a magnetic material; at least one power supply conductor having a power supply end and a free end; at least one power supply terminal for applying a voltage to the power supply end of the power supply conductor; and a power radiation conductor electrically insulated from and electromagentically coupled to the power supply conductor, the power radiation conductor arranged at the first main surface; wherein the at least one power supply conductor is spirally wound and arranged inside the substrate, the spirally wound conductor having a spiral axis extending parallel to the mounting surface; the at least one power supply terminal is arranged on the side surface of the substrate of the antenna body. The antenna unit according to the present invention is provided with a power supply conductor and a power radiation conductor. Therefore, the power radiation conductor can be operated as a radiating plate (namely, a radiator). Moreover, the power supply conductor can be operated as an exciter. In the antenna unit of the present invention, the power radiation conductor operates as a radiating plate, while the power supply conductor operates as an exciter. Thus, there is electromagnetic coupling between the power radiation conductor and the power supply conductor. Consequently, in comparison with the conventional antenna unit, at a low resonance frequency, a higher gain and a wider bandwidth can be obtained. Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings. Fig. 1 is a perspective view of an antenna unit according to the present invention; Fig. 2 is a front view of an electronic device on which the antenna unit of FIG. 1 is mounted; Fig. 3 is a sectional view of the electronic device taken in the direction of the arrows on line V-V of Fig. 2; Fig. 4 is a sectional view of a first modification of the electronic device of Fig. 2; Fig. 5(a) is a sectional view of a second modification of the electronic device of Fig. 2; Fig. 5(b) is a sectional view of a third modification of the electronic device of Fig. 2; Fig. 6 is a front view of another electronic device, on which an antenna unit according to the present invention is mounted; Fig. 7 is a sectional view of the electronic device taken in the direction of the arrows on line IV-IV of Fig. 5; Fig. 8 (a) is a sectional view of a first modification of the electronic device of Fig. 6; Fig. 8(b) is a sectional view of a second modification of the electronic device of Fig. 6; Fig. 9 (a) is a sectional view of a third modification of the electronic device of Fig. 6; Fig. 9(b) is a sectional view of a fourth modification of the electronic device of Fig. 6; and Fig. 10 is a diagram showing the conventional antenna body. Fig.1 is a perspective view of an antenna unit according to the present invention. In the antenna unit 20 a power supply conductor 22 is wound such that the winding axis C of the power supply conductor 22 of the antenna body 21 is parallel to a mounting surface 231, namely, the power supply conductor 22 is wound in a spiral in the longitudinal direction of a substrate 23. The antenna unit 20 has a spiral power supply conductor 22 and further has a nearly rectangular power radiation conductor 12. Further, there is provided electromagnetic coupling between the power supply conductor 22 and the power radiation conductor 12. Thus, there is generated a capacitance between the power radiation conductor 12 and a ground electrode (not shown). Consequently, the antenna unit 20 becomes an antenna, which has a low resonance frequency. Next, cases in which the antenna unit 20 is mounted on electronic devices, will be described hereinbelow. Fig. 2 and Fig. 3 are, respectively, a top view and a sectional view of an electronic device on which the antenna unit 20 is mounted. The antenna unit 20 is mounted on a printed circuit board 32 on which electronic parts composing an RF control portion 31 of an electronic device 30 are mounted. The antenna unit 20 is connected to the RF control portion 30 through a transmission line (not shown) or the like. Further, the printed circuit board 32, on which the antenna unit 20 is mounted, is placed in a casing 33 of the electronic device 30. The power radiation conductor 12 of the antenna unit 20 may be in contact with the casing 33 thereof but need not be in contact therewith. Fig. 4 is a sectional view of a modification of the electronic device in a case that the antenna unit 20 is mounted thereon. In the case of this modification, the casing 33 of the electronic device 30 comprises a carrying case 33a and a cover or lid 33b reclosably connected to the carrying case 33a. Further, the printed circuit board 32, on which the RF control portion 31 of the electronic device 30 is mounted, is provided in the carrying case 33a. Moreover, the antenna unit 20 is provided on the back surface of the cover 33b. The antenna unit 20 is connected to the RF control portion 31 of the electronic device 30 through a cable (not shown) or the like. In this case, the antenna unit 20 can be disposed in an orientation in which radiation reception/transmission is optimum. Incidentally, Fig. 4 illustrates the usage conditions of the electronic device. Usually, the electronic device is carried in a state in which the cover 33b is put on the carrying case 33a. Further, the electronic device may be used in a state in which the cover 33b is down on the carrying case 33a. Moreover, the electronic device may be used in a state, in which the cover 33b is detached therefrom, by preliminarily putting the carrying case 33a and the cover 33b in a detachable state. Figs. 2 to 4 illustrate the case that the antenna unit 20 is placed in the casing 33 of the electronic device 30. As shown in Fig. 5(a), the antenna unit 20 may be externally provided and added to the device 30 through a cable 43. In this case, the antenna unit 20 can be installed at a place where radiation reception/transmission is best. Moreover, a connector 34a may be attached to an end portion, which is at the side of the electronic device 30, of the cable 34. Furthermore, a connector (not shown) may be attached to the other end portion, which is at the side of the antenna unit 20, of the cable 34. Alternatively, connectors (not shown) may be attached to both of the end portions, which are at the sides of the electronic device 30 and the antenna unit 20, of the cable 34, respectively. In these cases, the antenna unit 20 can be detached from the electronic device 30. Moreover, such electronic devices and antennas in these cases are convenient to carry. Fig. 6 and Fig. 7 are a front view and a sectional view of an antenna unit according to the present invention, which is a third embodiment of the present invention, respectively, in a case where the antenna unit is placed in an electronic device. The electronic device 35 is configured by placing an antenna body 21 in a casing 36. The casing 36 has a power radiation conductor 37 that comprises a nearly rectangular metallic plate formed by performing e.g., printing, vapor deposition, laminating or plating of copper, copper alloy or aluminum. This power radiation conductor 37 is electrically isolated from the casing and the power supply conductor. The antenna body 21 is mounted on a printed circuit board 39 on which electronic parts comprising an RF control portion of the electronic device 35 are also mounted. The antenna body 21 is connected to the RF control portion 38 of the electronic device 35 through a transmission line (not shown) or the like. Further, the printed circuit board 39 is placed in the casing 36 of the electronic device 35. As above described, in the case of the structure of the electronic device 35, an antenna unit 40 consists of the antenna body 21 and the power radiation conductor 37 provided on the casing 36. Further, there is electromagnetic coupling between the power supply conductor 22 (Fig. 1), which is provided in the antenna body 21, and the power radiation conductor 37. Moreover, there is capacitance between the power radiation conductor 37 and the ground electrode (not shown). Consequently, the antenna unit comprises an antenna having a low resonance frequency. Fig. 8(a) and Fig. 8(b) are sectional views of first and second modifications of the antenna unit 40, which is the third embodiment of the present invention. In the case of the modification of Fig. 8(a), the casing 36 of the electronic device 35 comprises a carrying case 36a and a cover 36b reclosably connected to the carrying case 36a. Further, a printed circuit board 39, on which an RF control portion 38 of the electronic device 35 is mounted, is provided in the carrying case 36a. Moreover, the antenna unit 21 is provided on the back surface of the cover 36b. The antenna unit 21 is connected to the RF control portion 38 of the electronic device 35 through a cable (not shown). In the case of the modification of Fig. 8(b), the casing 36 of the electronic device 35 comprises a carrying case 36a and a cover 36b reclosably connected to the carrying case 36a. Further, a printed circuit board 39, on which an RF control portion 38 of the electronic device 35 is mounted, is provided in the carrying case 36a. Moreover, the antenna unit 21 is provided in the carrying case 36a. The power radiation conductor is provided on the cover 36b. The antenna unit 21 is connected to the RF control portion 31 of the electronic device 35 through a transmission line (not shown). In these cases, the power radiation conductor 37 can be oriented in a position in which radio reception/transmission is optimum. Incidentally, FIGS. 8(a) and 8(b) illustrate the usage conditions of the electronic device. Usually, the electronic device is carried with the cover 36b disposed on the carrying case 36a. Further, the electronic device may be used with the cover 36b disposed down on the carrying case 36a. Moreover, the electronic device may be used with the cover 36b detached therefrom, by preliminarily putting the carrying case 36a and the cover 36b in a detachable state. FIGS. 6 to 8 illustrate the case that the power radiation conductor is placed in the casing 33 of the electronic device 35. As shown in Fig. 9(a), the power radiation conductor 37 may be externally provided and added to the device 35 through a cable 41. In this case, the power radiation conductor 37 can be installed at a location where radio reception/transmission is optimum. Moreover, as illustrated in Fig. 9(b), a connector 41a may be attached to an end portion, which is at the side of the electronic device 35, of the cable 41. Furthermore, a connector (not shown) may be attached to the other end portion, which is at the side of the power radiation conductor 37, of the cable 41. Alternatively, connectors (not shown) may be attached to both of the end portions, which are at the sides of the electronic device 35 and the power radiation conductor 37, of the cable 41, respectively. In these cases, the power radiation conductor 37 can be detached from the electronic device 35. Moreover, such electronic devices and antennas in these cases are convenient to carry. Furthermore, the antenna body 21 and the power radiation conductor 37 can be separated from each other in a range in which the electromagnetic coupling therebetween can be established. The power radiation conductor 37 can be oriented in a position wherein radio reception/transmission is optimum, by, for instance, attaching the power radiation conductor 37 to the casing 33 of the electronic device 35. Incidentally, regarding the embodiments, there has been described the case that the substrate of the antenna body comprises a dielectric material containing barium oxide, aluminum oxide and silica as major ingredients. However, the material of the substrate is not limited thereto. For example, another dielectric material whose ingredients are titanium oxide and neodymium oxide, a magnetic material whose ingredients are nickel, cobalt and iron, or a combination of a dielectric material and a magnetic material may be employed as the material of the substrate of the antenna body. Further, although there has been described the case that the shape of the cross section of each winding orthogonal to the winding axis C of the power supply conductor wound in a spiral is nearly rectangular, the shape of the cross section of the winding has only to contain a linear part. In this case, the antenna unit of the present invention responds to primary polarized waves, which come from the direction of the winding axis, and cross polarized waves which come from a direction perpendicular to the winding axis. Thus, the antenna unit of the present invention is a non-directional one. Additionally, although there has been described the case that the number of the power supply conductors provided in or on the antenna body is one, two power supply conductors or more may be provided therein. In such a case, the antenna unit can have a plurality of resonance frequencies. Although there has been described the case that the power radiation conductor is a nearly rectangular metallic plate, the shape of the power radiation conductor is not limited to nearly rectangular. Further, similar advantages are obtained even if metallic foil or a mesh conductor is used instead of the metallic plate.

Claims: An antenna unit comprising: an antenna body (21) having a substrate (23), said substrate having a first main surface and a mounting surface (231) parallel to said first main surface, and a side surface connecting said first main surface and said mounting surface (231), said substrate (23) comprising at least one of a dielectric material and a magnetic material; at least one power supply conductor (22) having a power supply end (18a) and a free end (18b); at least one power supply terminal (19) for applying a voltage to said power supply end (18a) of said power supply conductor (22); and a power radiation conductor (12;37) electrically insulated from and electromagentically coupled to said power supply conductor (22), said power radiation conductor (12;37) arranged at said first main surface; characterized in that said at least one power supply conductor (22) is spirally wound and arranged inside said substrate (23), said spirally wound conductor (22) having a spiral axis extending parallel to said mounting surface (231); and said at least one power supply terminal (19) is arranged on said side surface of said substrate (23) of said antenna body (21). The antenna unit of claim 1, wherein said power radiation conductor (12; 37) is provided at an electronic device (30; 35) on which said antenna body (21) is mounted or at said substrate (23) of said antenna body (21). The antenna unit of any of claims 1 or 2, wherein the power supply conductor (22) has a substantially rectangular shape in transverse cross section. The antenna unit of any of claims 1 to 3, wherein the substrate (23) comprises a dielectric material comprising barium oxide, aluminum oxide, and silica. The antenna unit of any of claims 1 to 3, wherein the substrate (23) comprises a dielectric material comprising titanium oxide and neodymium oxide. The antenna unit of any of claims 1 to 3, wherein the substrate (23) comprises a magnetic material comprising nickel, cobalt and iron. The antenna unit of any of claims 1 to 6, wherein the substrate (23) comprises a combination of a dielectric material and a magnetic material. The antenna unit of any of claims 1 to 7, wherein the power radiation conductor (12) is at least one of an electrically conductive plate, electrically conductive foil and electrically conductive mesh. The antenna unit of any of claims 1 to 8, wherein the mounting surface (231) is for mounting the substrate on a printed circuit board (32). The antenna unit of claim 2, wherein the power radiation conductor (12) is provided on a casing (33) of the electronic device (30). The antenna unit of claim 2, wherein the substrate (23) is mounted on a printed circuit board (32) of the electronic device (30), the electronic device (30) having a radio frequency control portion (31), the power supply conductor (22) of the antenna unit (20; 40) being coupled to the radio frequency control portion (31) through a transmission line. The antenna unit of claim 2, wherein the electronic device (30) has two components, a carrying case portion (33a; 36a) housing the radio frequency control portion (31) and a cover portion (33b; 36b), the substrate (23) having the power supply conductor (22) and the power radiation conductor (12) being disposed in the cover portion. The antenna unit of claim 12, wherein the cover portion (33b; 36b) is movable with respect to the carrying case portion (33a; 36a). The antenna unit of claim 12, wherein the cover portion (33b; 36b) is detachable from the carrying case portion (33a; 36a). The antenna unit of claim 2, wherein the antenna unit (20) comprising the power radiation conductor (12) and the substrate (23) with the power supply conductor (22) is movable with respect to the electronic device (30; 35) and connectable to the electronic device (30) by a cable (34). The antenna unit of claim 2, wherein the power radiation conductor (12) is disposed in the cover portion (36b) and the substrate (23) having the power supply conductor (22) is disposed in the carrying case portion (36a) with the radio frequency control portion (31). The antenna unit of claim 2, wherein the power radiation conductor (12) is separable from the substrate (23) having the power supply conductor (22) and connectable to the electronic device (30; 35) by a cable (34; 41).

Inventors: MANDAI HARUFUMI, TSURU TERUHISA, MANDAI, HARUFUMI, TSURU, TERUHISA
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H01Q23
IPC codes: H01Q1, H01Q9, H01Q23