Patent Grant
7227509
The present invention relates to an antenna device used in mobile communications, which may be suitably applied to, for example, fixed wireless apparatuses and wireless terminals configured in a wireless LAN system.
In wideband wireless communications through, for example, a wireless LAN system, such a problem has arisen that the quality of transmission is deteriorated due to multi-path fading or shadowing, especially in indoor applications. For this reason, it is required to develop a directive antenna mounted on a wireless apparatus capable of being controlled so that a primary beam radiated from it may advance toward any direction to maintain the quality of transmission at a moderate level even in a poor radio-wave propagation environment affected by multi-path fading or shadowing.
In addition, it is further required that an antenna, which is mounted on a notebook-PC type of terminal wireless apparatus for using on a desk or on a fixed type of wireless apparatus attached to a ceiling, has a planar structure because of these apparatuses' configurations. It is also required that the elevation angle of a primary beam tilts toward the horizontal direction from the vertical direction relative to the antenna plane.
As an example of a sector antenna providing such a radiation characteristic, a Yagi-Uda slot array planar multi-sector antenna has been disclosed in Journal of the Institute of Electronics, Information and Communication Engineers of Japan (IEICE) ((B) Vol. J85-B, No. 9, pp. 1633-1643, 2002). In the following paragraphs, the sector antenna is briefly described.
As another type of antenna, an end-open diamond-shape antenna, has been disclosed in the patent document JP-A No. 355030/1999 and Journal of the Institute of Electronics, Information and Communication Engineers of Japan (IEICE) ((B) Vol. J82-B, No. 10, pp. 1915 to 1922, 1999).
The conventional Yagi-Uda slot array planar multi-sector antenna aforementioned, however, has such a problem that it is difficult to mount on small size wireless apparatuses because the dimension of its plane incorporating six sectors is large and furthermore, the sectors need to be placed so that they may draw a circle.
Besides, the conventional end-open diamond-shape antenna aforementioned, of which primary beam advances in the direction perpendicular to the antenna plane, thereby does not tilt horizontally, has such a problem that it may not suitably mounted on the notebook-PC type of wireless terminal or the fixed wireless apparatus attached to the ceiling.
An object of the present invention is to provide an antenna device, which may be suitably mounted on any of small wireless apparatuses and forms a primary beam, of which horizontally-polarized wave or vertically-polarized wave tilts toward the horizontal plane.
The object of the present invention aforementioned may be achieved by placing each of the delay elements at one of the opposite apex pairs and a reflector is inserted at a given distance in parallel to the antenna plane, on which the elements have been placed in the case of the end-open diamond-shape antenna, of which each side has a length equivalent to half a wavelength.
Now, preferred embodiments of the present invention re mentioned in reference to accompanying drawings.
Linear elements 101a to 101d are conductors having an element length L1 equivalent to half a wavelength (30 mm) and an element width, for example, 1 mm. These linear elements 101a to 101d are placed so that they may draw a diamond shape together as shown in
In the figure, delay elements 102a and 102b are conductors, which have been bent at a point equivalent to one eighth wavelength (7.5 mm), have a total length equivalent to one fourth wavelength (15 mm) and an element width of 1 mm, wherein a length L2 indicates the length of one of their longitudinal sides. The linear elements 101a and 101c are connected one another via the delay element 102a, while the linear elements 101b and 101d are connected one another via the delay element 102b.
A feeding point 103 is connected to one end of the linear element 101c and one end of the linear element 101a for feeding power to them. Note that a gap of length L3 is left between the tips of the linear elements 101c and 101d.
The diamond-shape antenna shown in
A reflector 104 is placed at a position on the −Z side, leaving a distance h equivalent to 0.42 wavelength (25 mm) from the plane on which the diamond-shape antenna having delay elements is placed. The reflector 104 is a square conductor plate with a length of each side almost equivalent to one (60 mm) or more wavelength. In one of the methods for stabilizing the distance h by firmly fixing the diamond-shape antenna with delay elements and the reflector 104, for example, a resin spacer is used to mechanically support them. This method has less influence on antenna performance.
Then, the operating principle of the antenna device having the aforementioned configuration is mentioned in reference to the accompanying drawings.
In
Similarly, in
Assuming that no delay elements 102a and 102b have incorporated, and the linear elements 101a and 101c are connected one another while the linear elements 101b and 101d being connected one another, the primary beam advances along Z-axis and the primary polarized wave is related to the Y-axis. This is the operating principle of the conventional diamond-shape antenna shown in
Then, focusing on a vertical X-Z plane, the operating principle of the antenna device, of which delay elements 101a and 101b are connected one another, shown in
One of models focusing exclusively on the vertical X-Y plane is a point source model shown in
It is assumed that the point sources 303 and 304 are placed at a distance 2 h (0.84 wavelength: 50 mm) from the point sources 301 and 302 to model the effect of the reflector 104. Based on the principle of transformation, the excitation phases of the point sources 303 and 304 may reverse their courses by 180° relative to those of the point sources 301 and 302.
Since the position of each point source along the X-axis is assumed to be the center of each linear element, the interval L4 between the point sources along the X-axis is equivalent to 0.71 wavelength (42.4 mm).
With four point sources 301 to 304 placed in this way, the array radiates the primary beam advancing toward the direction tilting from the Z-axis at an angle α (45°) The insertion of the reflector 104, in particular, may provide an effective tilt angle according to the embodiment 1 of the present invention.
In
As aforementioned, according to the antenna device according to the embodiment 1 of the present invention, by placing the linear elements with a length equivalent to half a wavelength so that they may draw a diamond shape and incorporating the delay elements at the opposite apex pairs, the antenna device suitably mounted on a small wireless apparatus may be achieved and further, the primary beam of which horizontally-polarized wave has a tilt angle of 45°, may be formed.
Note that in the embodiment 1, which has been mentioned assuming that the distance h from the linear elements to the reflector is equivalent to 0.42 wavelength, by changing the distance h, the tilt angle α may be varied. As the distance h is decreased, the tilt angle narrows and as it being increased, the tilt angle augments. Note that an increase in distance h may cause an unwanted maximum point (minor lobe) of directivity to occur along the −X-axis. For this reason, by selecting the distance h from a range of values from one fourth wavelength to half a wavelength depending on the application of the antenna, the gain of the antenna may be improved. In the embodiment 1, h has been set to 0.42 wavelength, achieving the optimal tilt angle and directivity.
In addition, in the embodiment 1, which has been mentioned assuming that the length of delay elements is equivalent to one fourth wavelength, by changing the length of the delay elements, the tilt angle a may be varied. As the length of the delay elements is decreased, the tilt angle narrows and as the length being increased, the tilt angle widens. Note that an increase in length of the delay elements may cause a minor lobe of directivity to occur along the −X-axis. For this reason, by selecting the length of the delay elements of the antenna from a range of values from 0.2 to 0.35 wavelength depending on the application of the antenna, the gain of the antenna may be improved. In the embodiment 1, the length of the delay elements is set to one fourth wavelength, achieving the optimal tilt angle and directivity.
Furthermore, in the embodiment 1, conductor type of delay lines are used, though the use of lumped constant parts, for example, inductors, may have the same effects as those aforementioned.
It goes without saying that although the linear elements, which have been placed so that they may draw a diamond shape, have been mentioned so far, the elements may be placed so that they may draw a square.
Moreover, in the embodiment 1, which has been mentioned using four linear elements, according to the present invention, two linear elements are bent to form linear delay elements, enabling the diamond-shape with delay elements to be achieved. This may not only have a less number of parts compared with the antenna composed of four linear elements but also make easy the process of manufacturing antennas.
In
Thus, according to the antenna device according to the embodiment 2 of the present invention, the addition of the director element to the antenna device mentioned in the description of the embodiment 1 may improve the gain in the direction of the director element.
Note that the distance L6 between the director element 501 and the linear elements 101c or 101d, and the length of the director length L5 are given as only examples. By modifying these parameters to change both the directivity and gain of the antenna device, appropriate parameters may be selected depending on the application of the antenna.
Two or more director elements instead of only one element may be incorporated in a row along the X-axis to achieve a further higher gain.
In the embodiment 3, an antenna device, in which the linear elements of the antenna device mentioned in the embodiment 1 have been replaced with slot (gap) elements.
In
A copper foil layer 702 indicates the copper foil adhered to the side Z of the substrate 701. Slot elements 703a to 703d are the slot elements, which have been formed by denuding the cupper foil layer 702. Slot delay elements 704a and 704b are also formed by denuding the cupper foil layer 702. The length L7 of each of the slot elements 703a to 703d is set to ½λe (25 mm). The element length of each of the delay elements 704a and 704b is ¼λe (12.6 mm) and the length L8 of each of their longitudinal sides is set to ⅛λe (6.3 mm).
A gap L10 with the cupper foil layer left, which is defined between the tips of the slot elements 703c and 703d, is 2 mm. A slot (gap) is connected to the elements 703a and 703b.
A slot diamond-shape antenna with delay elements having a length L9 equivalent to 0.702λe (35.4 mm) is composed of the slot elements 703a to 703d and the slot delay elements 704a and 704b formed in the aforementioned way.
A micro strip line 705 is formed using the copper foil layer along the X-axis in the vicinity of the connection between the slot elements 703a and 703b on the −Z side on the substrate 701. The width W of the micro strip line 705 is 4.3 mm and its characteristic impedance is set to 50Ω. The distance L12 between the tip of the micro strip line 705 and the connection between the slot elements 703a and 703b is set to, for example, 4.5 mm.
This configuration enables the micro strip line 705 and the slot diamond-shape antenna with delay elements are electro-magnetically coupled to one another, allowing the micro strip line 705 to operate as a feeding line. This makes it possible to feed power with impedances balanced, resulting in easy power feed to the dielectric substrate from the micro strip line, a plane circuit. Thus, the antenna device may be further miniaturized.
In the diamond-shape antenna with delay elements according the embodiment 3 shown in
In
Thus, according to the antenna device according to the embodiment 3, not only the antenna device, which may be suitably mounted on a small wireless apparatus, may be provided but also the tilt angle of 35° may be used and the vertical polarized wave (Eθ) component is used as the primary polarized wave component by placing the slot elements with a length equivalent to half a width so that they may draw a diamond shape and incorporating the delay slot elements at the opposite apex pairs to make the plane smaller.
Note that although in the embodiment 3, the slot elements have been formed using the copper foil layer on the dielectric substrate, almost the same effect may be achieved, for example, by forming the slots (gaps) on the conductor plate.
In
Thus, since the formation of the director slot element 901 enables the beam radiated from the slot diamond-shape antenna with delay elements to converge along the X-axis, improving the ratio (F/B ratio) between the gains along the X and −X axes.
As known from
Thus, according to the antenna device according to the embodiment of the present invention, the formation of the director slot element on the antenna device mentioned in the embodiment 3 enables the tilt angle to be enlarged and higher F/B ratio to be achieved.
Note that the distance L14 between the director slot element 901 and the slot elements 703c and 703d, as well as the length L13 of the director slot element 901, are just examples taken in describing this embodiment. It is preferable to select appropriate parameters according to individual applications because the directivity and gain of the antenna may change as these parameters are modified.
In addition, more than one director slot element(s) may be used. Rather, two or more of the director slot elements aligned in line along the X axis would offer further higher F/B ratio.
In
The outer dimension of the six-sector antenna shown in
In the case where the operating frequency of the antenna is 25 GHz, the shape of the six-sector antenna shown in
As known from
By selectively feeding power to the slot diamond-shape antennas with delay elements 1101a to 1101f configured as aforementioned, switching may be achieved among the sectors obtained by dividing 360° on the horizontal plane by six. This provides the six-sector antenna.
Thus, according to the embodiment 5 of the present invention, by placing six slot diamond-shape antennas with the delay elements on the rectangular plane while rotating them by 60° and selectively feeding power to the antennas, higher gains may be achieved in all the radial directions, providing a small six-sector antenna.
Note that in the embodiment 5, the method for achieving the six-sector antenna has been mentioned but the present invention is not limited to this type of antennas and may be applicable to the method for manufacturing a plurality of sector antennas.
Although in the embodiment 5, the antenna device shown in the embodiment 3 has been mentioned, the antenna device described in any other embodiment may be used.
The antenna device of the present invention comprises four linear elements, each of which has a length equivalent to a half wavelength of an operating frequency, the elements being placed so that they may draw a diamond shape on a plane, a feeding section that feeds power to one end of a first linear element and one end of a second linear element, the section being put at one of the apexes of a diamond shape, a first delay section connected to the other end of the first linear element and one end of a third linear element for delaying the phase of an antenna current by a given phase, a second delay section connected to the other end of the second linear element and one end of a fourth linear element for delaying the phase of an antenna current by the same phase as that of the first delay section, and a reflector placed at a given distance in parallel to a plane, on which the linear elements have been placed.
Since according to this configuration, the phases of the antenna currents are delayed by the given phase component by means of the first delay means and the second delay means, the phases are shifted between the antenna currents flowing on the first and second linear elements and between the antenna currents flowing on the second and fourth linear elements. This composes an electric wave radiated and an electric wave reflected at the reflector, achieving the antenna device capable of forming the primary beam tilting toward the horizontal place.
In the aforementioned configuration of the antenna device of the present invention, the first delay section and the second delay section have a length within a given range, the sections being linear elements having a bent form.
According to this configuration, by changing the length of the bent linear elements to any other one within the given limits, the amount of delayed phase component of the antenna current may be varied, resulting in a tilt angle modified to a desired one.
In the aforementioned configuration of the antenna device of the present invention, the first delay means and the second delay means are lumped constant parts.
According to this configuration, by changing the lumped constant of the lumped constant parts to any other one, the amount of delayed phase component of the antenna current may be varied, resulting in a tilt angle modified to a desired one.
The aforementioned configuration of the antenna device of the present invention comprises: at least one director element having a length equivalent to a half wavelength or less, the director element being placed at a given distance from an open end of the linear element.
According to this configuration, the radio wave radiated from the diamond-shape antenna device may be converged toward the director element, improving the gain in the direction of the director element.
The antenna device of the present invention comprises two linear elements having the same length, a bending part formed by bending the two linear elements at the centers of the elements with a length within a given range, a feeding section connected to one end of the two linear elements to feed power, and the reflector placed at a given distance in parallel to a plane containing the two linear elements, wherein the two linear elements are bent and placed so that they draw a diamond shape, of which one side has a length equivalent to a half wavelength of an operating frequency and the other ends of the two linear elements are open.
According to this configuration, by inserting two bent linear elements, the diamond-shape with delay elements may be formed, enabling the antenna device to be assembled using less number of parts. This makes easy the process of manufacturing antenna devices.
The antenna device comprises a dielectric substrate with a given dielectric constant,
a conductor layer formed on the dielectric substrate,
a diamond-shape slot element formed on the conductor substrate, of which each side has a length equivalent to a half wavelength of an operating frequency,
the first delay section and the second delay section, which have been placed at each of opposite apex pairs of the diamond shape to delay the phase of an antenna current,
the feeding section, which have been placed on either of another one of the opposite apex pairs of the diamond shape, for feeding power to the slot elements,
a termination part formed at the other of another one of the opposite apex pairs of the diamond shape, for terminating the slot elements, and
the reflector placed beyond the substrate at a given distance from and in parallel to the conductor layer.
Since according to this configuration, the delay means delay the phases of the antenna currents, the phases may be out of phase between the antenna currents flowing through the slot element from the feeding means to the delay means and flowing through the slot element from the delay means to termination part. This composes the electric wave radiated and the electric wave reflected at the reflector, achieving the antenna device, which may form the primary beam, of which vertically-polarized wave tilts toward the horizontal plane.
In the aforementioned configuration of the antenna device of the present invention, the first delay section and the second delay section are the slot elements having a bent form with a length within the given range, which are formed on the conductor layer.
Since according to this configuration, by changing the length of each of the bent slot elements to any other one within the given limits, the amount of the delayed phase component of the antenna current, resulting in the modified tilt angle. This brings the desired tilt angle.
In the aforementioned configuration of the antenna device of the present invention, the feeding section feeds power using a micro strip line laid on a rear plane of the substrate, on which the conductor layer has been formed.
According to this configuration, the feeding means may feed power to the slot elements with impedances well-balanced, providing not only easier power feed but also a further miniaturized antenna device.
In the aforementioned configuration of the antenna device of the present invention, at least one director slot element with a length equivalent to a half wavelength or less, which has been formed at a given distance from the termination part of the slot element.
According to this configuration, the radio wave radiated from the diamond-shape antenna device may be converged toward the director element, improving the gain in the direction of the director element.
The sector antenna of the present invention has been configured so that a plurality of antenna devices according to claim 1 are used, the antenna devices being placed on a plane while being shifted at equal angle from each other.
According to this configuration, the sector antenna capable of forming the primary beam advancing toward the desired direction may be achieved.
In the aforementioned configuration of the sector antenna of the present invention, six antenna devices have been placed in a row on a given rectangular plane, the six antenna devices being shifted by 60° from each other.
According to this configuration, by rotating the diamond-shape six antenna devices by 60° relative to adjacent ones when being placed on the rectangular place, a six-sector antenna capable of forming the primary beams advancing toward six different directions at an equal interval may be obtained, achieving a sector antenna suitably mounted on any of small wireless apparatuses.
As aforementioned, according to the present invention, the open-end diamond-shape antenna, of which one side has a length equivalent to half a wavelength, wherein the delay elements are placed at each of the opposite apex pairs and a reflector is inserted at a given distance in parallel to the plane, in which the elements are place, may form the primary beam, of which horizontally-polarized or vertically-polarized wave tilts toward the horizontal plane. In addition, the diamond-shape antennas with delay elements may be rotated at an even angle when being placed on the rectangular plane, achieving a sector antenna suitably mounted on any of small wireless apparatuses.
This specification was prepared based on the patent application No. 2003-022369 filed on Jan. 30, 2003. This statement is specifically contained here.
The present invention may be suitably applied to fixed wireless apparatuses and wireless terminals configured in a wireless LAN system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-022369 | Jan 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2004/000274 | 1/16/2004 | WO | 00 | 7/20/2005 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2004/068635 | 8/12/2004 | WO | A |
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