Antenna apparatus and communication apparatus using the same

Abstract: A method of mounting a surface mounting antenna (10) on a mounting substrate (11), which can improve the gain. An electromotive type surface mounting antenna is mounted in the vicinity of one corner defined by the intersection of two sides (11a, 11b) of a mounting substrate (11). The surface mounting antenna (10) is mounted on the mounting substrate so (11) that an open end (2a) of a radiation electrode (2) of the surface mounting antenna (10) faces in a direction away from at least one side (11a) of the two sides (11a, 11b).

Description: The present invention relates to a method of mounting or packaging a surface mounting antenna on a mounting substrate, which is applicable to mobile body communication equipment such as a portable telephone system and radio LAN (Local Area Network) systems, and a communication apparatus equipped with this mounting substrate. Referring to Fig. 11, a description will be made hereinbelow of the prior method of mounting a surface mounting antenna on a mounting substrate. In the illustration, numeral 40 represents a surface mounting antenna which is mounted in the vicinity of one corner of the surface of a mounting substrate 41. In this surface mounting antenna 40, an L-shaped radiation electrode 42 and a supply electrode 43 are formed such that a gap g is interposed therebetween. However, in the case of the prior art method of mounting the surface mounting antenna 40 on the mounting substrate 41, an open end 42a of the radiation electrode 42 of the surface mounting antenna 40 faces one side 41a of two sides constituting the aforesaid one corner of the mounting substrate 41 as indicated by an arrow, which lowers the gain. This is because an image current flowing in a ground electrode (a portion indicated by dotted lines) gathers in the vicinity of the one side 41a and an electromagnetic field in the Z direction (toward the upper end portion of the mounting substrate) wraps around an edge to produce a conductor loss. In addition, a communication apparatus having such a mounting substrate also causes the gain to lower. JP-A-07221537 discloses an antenna including a dielectric substrate, a radiation electrode, a feeding electrode formed on a side surface of the dielectric substrate, a side electrode formed on that side surface of the dielectric substrate on which the feeding electrode is formed and being electrically insulated from the feeding electrode. The antenna further comprises a side electrode formed on a side surface opposite to the side electrode and electrically connected to the radiation electrode. The antenna is placed on the printed circuit board such that the feeding electrode and an electrode pattern on the printed circuit board are soldered to each other and such that the side electrode and the grounding electrode are soldered to each other, thereby surface-mounting the antenna on the printed circuit board. The radiation antenna is provided on a side surface being adjacent to a mounting surface of the dielectric substrate. On the surface of the dielectric substrate which is opposite to the mounting surface, no electrodes are provided. Accordingly, it is an object of the present invention to provide a method of mounting a surface mounting antenna on a mounting substrate, which is capable of making the image current flow in the central portion of the mounting substrate to reduce the conductor loss, and further to provide a communication apparatus equipped with this mounting substrate. This object is achieved by a method according to claim 1 or a communication apparatus according to claim 4. For this purpose, in a surface mounting antenna mounting method according to the present invention, when an electromagnetic type surface mounting antenna is mounted in the vicinity of one corner defined by the intersection of two sides of a mounting substrate, the surface mounting antenna is mounted on the mounting substrate so that an open end of a radiation electrode of the surface mounting antenna faces in a direction away from at least one side of the two sides. Furthermore, in accordance with this invention, the above-mentioned surface mounting antenna is constructed as an electromagnetic type surface mounting antenna, wherein the radiation electrode is bent to have a substantially L-shaped or substantially U-shaped configuration so that one end is open and the other end is short-circuited, and the radiation electrode and a supply electrode for exciting it are formed on one main surface of a base, made of a dielectric or magnetic substance, in a state where a gap is interposed therebetween, and the radiation electrode and the supply electrode are respectively connected to a ground terminal and a supply terminal formed on any one of end surfaces of the base. Still further, in accordance with this invention, there is provided a communication apparatus equipped with a mounting substrate having the aforesaid surface mounting antenna. As described above, according to this invention, since, when mounting the surface mounting antenna in the vicinity of one corner of the mounting substrate, the surface mounting antenna is mounted on the mounting substrate so that the open end of the surface mounting antenna faces in a direction of separating from at least one side of the two sides producing that corner, the image current flows in the central portion of the mounting substrate to lessen the wrapping of the electromagnetic field in the Z direction around the edge for reducing the conductor loss while increasing the gain. In addition, a communication apparatus having the mounting substrate equipped with this surface mounting antenna is also capable of improving the gain. The objects and features of the present invention will become more readily apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings in which: Fig. 1 is a perspective view useful for describing a method of mounting a surface mounting antenna on a mounting substrate according to the present invention; Fig. 2 is an enlarged perspective view showing the surface mounting antenna of Fig. 1; Fig. 3 is a perspective view showing a surface mounting antenna on a mounting substrate according to a further embodiment of the present invention; Fig. 4 is an enlarged perspective view showing another surface mounting antenna; Fig. 5 is a perspective view showing the surface mounting antenna of Fig. 4 mounted on a mounting substrate; Fig. 6 is an illustration of a radiation pattern characteristic of a mounting substrate according to the invention in an X-Y plane; Fig. 7 is an illustration of a radiation pattern characteristic of a prior art mounting substrate in an X-Y plane; Fig. 8 is an illustration of a radiation pattern characteristic of a mounting substrate according to the invention in an X-Z plane; Fig. 9 is an illustration of a radiation pattern characteristic of a prior art mounting substrate in an X-Z plane; Fig. 10 is a perspective view showing a communication apparatus according to the invention; and Fig. 11 is a perspective view available for explaining a prior art method of mounting a surface mounting antenna on a mounting substrate. Referring to the drawings, a description will be made hereinbelow of an embodiment of the present invention. Fig. 1 is a perspective view useful for describing a method of mounting a surface mounting antenna on a mounting substrate. In the illustration, numeral 10 designates a surface mounting antenna which is also shown in an enlarged condition in Fig. 2. On a surface of a base 1 of the surface mounting antenna 10, made of a dielectric substance or magnetic substance, a radiation electrode 2 of λ/4 approximation and with an L-shaped configuration and a supply electrode 3 are formed in a state where a gap g is interposed therebetween. The radiation electrode 2 has an open end 2a at its one end and further has a short-circuited end 2b at its other end. This short-circuited end 2b is connected to a short-circuiting terminal 4 formed to extend over one end surface 1a and rear surface of the base 1, whereas the supply electrode 3 is connected to a supply terminal 5 made to extend over the one end surface 1a and rear surface of the base 1. The supply electrode 3 and the open end 2a of the radiation electrode 2 are spaced by a distance d on average from each other and come into an electric field coupling to each other by a capacity Cd developed due to the separation of the distance d therebetween. Although the supply electrode 3 and the radiation electrode 2 are in the closest relation to each other by way of the gap g disposed therebetween, the short-circuited end 2b portion is inductive and hence the degree of coupling therebetween is small. On the other hand, although the supply electrode 3 and the open end 2a are separated from each other, the surface mounting antenna 10 itself is small in size so that the degree of coupling therebetween is relatively large. With the above-described construction, the surface mounting antenna 10 can be mounted in the vicinity of one corner of a mounting substrate 11 as shown in Fig. 1. The surface antenna 10 is mounted on the mounting substrate 11 so that the open end 2a of the radiation electrode 2 faces in a direction away from at least one side 11a of two sides or edges constituting one corner as indicated by an arrow. Owing to this mounting of the surface mounting antenna 10 on the mounting substrate 11, the image current flows in the central portion of the mounting substrate 11, with the result that the wrapping of the electromagnetic field in the Z direction around the edge is reducible to lessen the conductor loss. In this case, although not separating from the other side 11b, the separation from at least the one side 11a causes the gain to heighten. Fig. 3 illustrates a further embodiment according to the present invention. The structure of the surface mounting antenna 10 is substantially the same as the structure of the antenna described with reference to Fig. 1. As shown in Fig. 3, the surface antenna 10 is mounted on the mounting substrate 11 such that the open end 2a of the radiation electrode 2 faces in a direction that faces away from both sides 11a, 11b of the mounting substrate 11. Fig. 4 illustrates a surface mounting antenna 20 having a radiation electrode 22 with a substantially U-shaped configuration. Also with this structure, owing to a capacity Cd produced between an open end 22a of the radiation electrode 22 and the supply electrode 3, the supply electrode 3 and the radiation electrode 22 chiefly come into electromagnetic field coupling to each other. Fig. 5 illustrates the surface mounting antenna shown in Fig. 4 mounted on a mountin substrate 11. The surface antenna 20 is mounted to the mounting substrate 11 such that the open end 2a of the radiation electrode 22 faces in a direction away from the two sides or edges consituting one corner of the substrate 11. Secondly, the radiation pattern characteristics of the mounting substrate of Fig. 1 and the prior art mounting substrate of Fig. 11 will be described hereinbelow with reference to Figs. 6 to 9. Figs. 6 and 7 show the radiation pattern characteristic of the Fig. 1 embodiment and the radiation pattern characteristic of the Fig. 11 prior art example in an X-Y plane, respectively. In the case of the embodiment shown in Fig. 6, the average gain is -8.5 dB at 1.9 GHz. On the other hand, in the case of the prior art example shown in Fig. 7, the average gain is -12.2 dB at 1.9 GHz. Further, Figs. 8 and 9 show the radiation pattern characteristics of the Fig. 1 embodiment and the Fig. 11 prior art example in an X-Y plane, respectively. In the case of the embodiment shown in Fig. 8, the average gain is -8.1 dB at 1.9 GHz. On the other hand, in the case of the prior art example shown in Fig. 9, the average gain is -11.4 dB at 1.9 GHz. As obvious from Figs. 6 to 9, the average gain in the radiation pattern characteristic of this embodiment improves by 3 to 4 dB as compared with that of the prior art example. Furthermore, referring to Fig. 10, a description will be made hereinbelow of a communication apparatus having a mounting substrate equipped with a surface mounting antenna according to the invention. The mounting substrate (or a sub-mounting substrate) 11 on which the surface mounting antenna 10 (20) is mounted as described above is installed in a communication apparatus 30. Also in this instance, its radiation pattern characteristics are similar to those as shown in Figs. 6 and 8. According to the invention, since, when a surface mounting antenna is mounted in the vicinity of one corner of a mounting substrate, the surface mounting antenna is mounted on the mounting substrate so that an open end of a radiation electrode faces in a direction away from at least one side of two sides constituting the corner, the image current passes through the central portion of the mounting substrate, with the result that the wrapping of the electromagnetic field in the Z direction around an edge is reducible to lessen the conductor loss so that the gain improves. In addition, a communication apparatus having the mounting substrate equipped with the surface mounting antenna mounted as mentioned before can also produce the improvement in the gain. Further to the embodiments described above, it is noted that the shape of the radiation electrode 2, 22 is not restricted to the described shapes. The radiation electrode 2, 22 of the surface mounting antenna 10, 20 can also be formed as a stright strip line.

Claims: A method of mounting an electromagnetic type surface mounting antenna (10; 20) on a mounting substrate (11), the surface mounting antenna having an antenna base (1), the antenna base (1) having a mounting surface to be mounted to the mounting substrate (11) and a radiation electrode surface being opposite to the mounting surface, and a radiation electrode (2) disposed on the radiation electrode surface, the radiation electrode having an open end (2a), comprising the step of: mounting the surface mounting antenna (10; 20) in the vicinity of the corner defined by an intersection of two sides (11a, 11b) of said mounting substrate (11) so that the mounting surface of the antenna base is placed on a surface of the mounting substrate (11), wherein said surface mounting antenna (10; 20) is disposed on said mounting substrate (11) such that the open end (2a; 22a) of the radiation electrode (2; 22) faces in a direction away from at least one side (11a) of said two sides (11a, 11b) of the mounting substrate (11). A method in accordance with claim 1, wherein said surface mounting antenna (10; 20) is disposed on said mounting substrate (10) such that the open end (2a; 22a) of the radiation electrode (2; 22) faces in a direction away from both of said two sides (11a, 11b) of the substrate (11). The method of claim 1 or 2, in which said radiation electrode (2; 22) of said surface mounting antenna (10; 20) is formed to have one of a substantially L-shaped configuration and a substantially U-shaped configuration with a first end portion being open (2a; 22a) and a second end portion being short-circuited (2b), wherein said radiation electrode (2; 22) and a supply electrode (3) for exciting said radiation electrode (2; 22) are arranged with a gap (g) therebetween on a main surface of the substrate comprising at least one of a dielectric substance and a magnetic substance, the method further comprising the following step: connecting said radiation electrode (2; 22) and said supply electrode (3) respectively to a ground terminal and a supply terminal formed on at least one end surface of said substrate (11). A communication apparatus (30) comprising: at least one of an electromagnetic frequency transmitter circuit and an electromagnetic frequency receiver circuit; and a surface mounting antenna (10; 20) disposed on a mounting substrate (11) connected to at least one of the transmitter circuit and receiver circuit, the electromagnetic surface mounting antenna having: an antenna base (1), the antenna base (1) having a mounting surface to be mounted to the mounting substrate (11) and a radiation electrode surface being opposite to the mounting surface, and a radiation electrode (2) disposed on the radiation electrode surface, the radiation electrode having an open end (2a), the surface mounting antenna being mounted in the vicinity of the corner defined by an intersection of two sides (11a, 11b) of said mounting substrate (11), so that the mounting surface of the antenna base is placed on a surface of the mounting substrate (11), and the surface mounting antenna (10; 20) being disposed on said mounting substrate (11) such that the open end (2a; 22a) of the radiation electrode (2; 22) faces in a direction away from at least one side (11a) of said two sides (11a, 11b) of the substrate (11). A communication apparatus (30) according to claim 4, in which the surface mounting antenna (10; 20) is disposed on said mounting substrate (11) such that the open end (2a; 22a) of the radiation electrode (2; 22) faces in a direction away from both of said two sides (11a, 11b) of the substrate (11). The communication apparatus of claim 4 or 5, wherein the radiation electrode (2; 22) of said surface mounting antenna (10; 20) has one of a substantially L-shaped configuration and a substantially U-shaped configuration with a first end portion being open (2a; 22a) and a second end portion being short-circuited (2b), wherein a supply electrode (3) is disposed adjacent the radiation electrode (2; 22) , the supply electrode (3) being disposed adjacent the radiation electrode (2; 22) with a gap (g) therebetween and being provided for exciting the radiation electrode (2; 22), the radiation electrode (2; 22) and the supply electrode (3) being provided on a main surface of the substrate comprising one of a dielectric substance and a magnetic substance, the radiation electrode (2; 22) and the supply electrode (3) being connected respectively to a ground terminal and a supply terminal formed on at least one end surface of said substrate.

Inventors: KAWAHATA KAZUNARI, OKADA KEN, KAWAHATA, KAZUNARI, OKADA, KEN
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1997
Main classification: H01Q9
IPC codes: H01Q9, H01Q1