JP2006186851A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system having simple structure of which the directivity is considerably changed. <P>SOLUTION: The antenna system is provided with a feed element 1 and a parasitic element 2. The feed element 1 has a folded distal end part 1a and has an electric length resonating with prescribed frequency. Similarly, the parasitic element 2 has a folded distal end part 2a. The distal end parts 1a and 2a are arranged nearby facing each other. On the parasitic element 2, three switches SW1, SW2, and SW3 for variably controlling the electric length of the parasitic element 2 are provided. The distal end part of the feed element 1 and the distal end part of the parasitic element 2 are arranged nearby facing each other and switches are provided for a proximal end part and the distal end part of the parasitic element 2. Thus, by switching on/off the switches optionally, the variable control of electric length of the parasitic element 2 can be realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna device capable of changing directivity.

A technique for changing directivity using a parasitic element has been proposed (see Patent Document 1). As a conventional technology of this type, it is possible to direct the directivity of the antenna in the direction in which the element is arranged within the plane where the element is arranged. A Yagi-Uta antenna is known in which the operation of an element is switched between a director and a reflector, and the directivity is switched within the plane where the element is arranged. In addition, there is an Esper antenna in which a plurality of parasitic elements are arranged around a feeding element, and directivity is changed by switching the parasitic element to be used with a switch.
JP 2004-128557 A

  However, with the Yagi / Uta antenna described above, the phase difference between the feed element and the parasitic element can be changed around 150 to 180 degrees. For this reason, directivity cannot be changed significantly. Further, the above-described esper antenna has a problem that the configuration is complicated.

  The present invention provides an antenna device that can change the directivity with a simple configuration.

  According to one aspect of the present invention, a feed element having an electrical length that resonates at a predetermined frequency, having a feed point and a bent first tip portion, and disposed adjacent to the first tip portion and bent. An antenna device comprising: a parasitic element having a second tip portion; and an electrical length switching unit that is provided on the parasitic element and is capable of changing an electrical length of the parasitic element. Is to provide.

  According to the present invention, directivity can be significantly changed without complicating the structure.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic shape of an antenna device according to a first embodiment of the present invention. The antenna device of FIG. 1 includes a feeding element 1 and a parasitic element 2. The feed element 1 has a bent tip 1a and has an electrical length that resonates at a predetermined frequency. Similarly, the parasitic element 2 has a bent end portion 2a. These tip portions 1a and 2a are arranged close to each other so as to face each other.

  The feeding element 1 has a symmetrical structure with the feeding point 3 interposed therebetween. Three switches SW1, SW2 and SW3 for variably controlling the electrical length of the parasitic element 2 are provided on the parasitic element 2, and these switches can be individually turned on / off. The switch SW2 is provided at the center of the parasitic element 2, and the parasitic element 2 has a symmetrical structure with the switch SW2 interposed therebetween. The switches SW2 and SW3 are provided at the tip 2a of the parasitic element 2.

  When all the switches SW1 to SW3 are turned on, the electrical length of the parasitic element 2 is the longest. When the switch SW2 is turned off, the electrical length of the parasitic element 2 becomes a length that does not operate at a predetermined frequency. When one of the switches SW1 or SW3 is turned off, the electrical length of the parasitic element 2 is shortened.

  Thus, the electrical length of the parasitic element 2 can be changed in three ways by switching the switches SW1 to SW3 on and off. By changing the electrical length of the parasitic element 2, the phase difference between the currents flowing through the feeding element 1 and the parasitic element 2 changes, and the directivity pattern of the antenna device of FIG. 1 also changes greatly. In the case of the present embodiment, the phase difference between the currents flowing through the feed element 1 and the parasitic element 2 varies greatly from around 0 degree to around 130 degrees.

  FIG. 2 is a modification of the antenna device of FIG. 1, and is a diagram showing a schematic shape of the antenna device that exhibits the same characteristics as the antenna device of FIG. The antenna device of FIG. 2 includes a feed element 1 disposed above a feed point 3 provided on a conductor plate 4, a parasitic element 2 having one end connected to the conductor plate 4 and disposed above the conductor plate 4. It has.

  The antenna device of FIG. 2 has a shape in which only the upper half of the antenna device of FIG. 1 is taken out. In the case of the antenna device of FIG. 2, since an image current flows through the conductor plate 4, it electrically exhibits the same characteristics as the antenna device of FIG. The feed element 1 has a bent tip portion 1a, and similarly, the parasitic element 2 also has a bent tip portion 2a. These tip portions 1a and 2a are arranged close to each other so as to face each other.

  A switch SW1 is provided at the distal end 2a of the parasitic element 2, and a switch SW2 is provided at the proximal end. One end of the base end is connected to the tip 2 a and the other end is connected to the conductor plate 4.

  The switches SW1 and SW2 can be individually turned on / off, and the electrical length of the parasitic element 2 changes depending on the on / off of these switches. When both switches SW1 and SW2 are turned on, the electrical length of the parasitic element 2 is maximized. When the switch SW1 is turned off and the switch SW2 is turned on, the electrical length of the parasitic element 2 is shortened. When the switch SW2 is turned off, The electrical length of the parasitic element 2 is a length that does not operate at a predetermined frequency. Thus, the electrical length of the parasitic element 2 can be changed in three ways by turning on and off the switches SW1 and SW2.

  FIG. 3 is a diagram showing how the phase difference between the currents of the feed element 1 and the parasitic element 2 changes depending on whether the switches SW1 and SW2 are turned on or off. The horizontal axis in FIG. 3 indicates the electrical length of the parasitic element 2. The electrical length of the parasitic element 2 is changed by turning the switches SW1 and SW2 on and off. However, the phase difference between the currents of the feeding element 1 and the parasitic element 2 is changed by the electrical length of the parasitic element 2. In the case of FIG. 3, the phase difference varies from −20 degrees to 140 degrees. When the phase difference changes, the radio wave directivity pattern also changes.

  FIG. 4 is a diagram showing the relationship between on / off of the switches SW1 and SW2 and the directivity of radio waves, and FIG. 5 is a diagram showing a directivity pattern showing the directivity of radio waves. 5A shows the directivity pattern in state 1 (both switches SW1 and SW2 are on) in FIG. 4, and FIG. 5B shows the directivity in state 2 in FIG. 4 (switch SW1 is off and switch SW2 is on). FIG. 5C shows the directivity pattern in state 3 (both switches SW1 and SW2 are off) in FIG.

  The on / off control of the switches SW1 and SW2 may be performed manually, but can also be performed automatically according to radio wave reception conditions.

  FIG. 6 is a block diagram showing an example of an antenna device that automates on / off control of the switches SW1 and SW2. In FIG. 6, diodes are used as specific examples of the switches SW1 and SW2. Instead of the diode, other switching means such as a transistor may be used.

  The antenna device of FIG. 6 includes a feeding element 1 and a parasitic element 2 formed in a copper pattern on a dielectric substrate 5, diodes D1 and D2 provided on the parasitic element 2, and a parasitic element 2. Bias lines b1 and b2 to be connected, inductor elements 6 and 7 connected to the bias lines b1 and b2, power supplies PS1 and PS2 for controlling on / off of the diodes D1 and D2, and power supplies PS1 and PS2 are controlled. The control part 8 which performs and the reception power detection part 9 which detects the reception power of the antenna of FIG. 6 are provided.

  For example, a feed line 10 including a coaxial cable 10 is connected to the feed point 3, an outer conductor of the feed line 10 is grounded to the conductor plate 4, and an inner conductor is connected to the feed element 1.

  The diodes D1 and D2 and the inductor element are, for example, chip parts, and are individually mounted on the dielectric substrate 5. The power supplies PS1 and PS2 can switch and output positive and negative voltages based on an instruction from the control unit 8. The control unit 8 controls the power supplies PS1 and PS2 so that the received power is increased based on the received power of the antenna apparatus of FIG.

  The phase difference between the currents of the feed element 1 and the parasitic element 2 varies depending on the interval between the feed point 3 on the conductor plate 4 and the ground point of the parasitic element 2 (hereinafter, the connection position interval). By controlling the direction of the voltage applied to the diodes D1 and D2 with respect to this phase difference, a phase difference that cancels radiation in the X direction or Y direction in FIG. 5 is generated.

  The connection position interval is set to, for example, 0.35 wavelength to 0.65 wavelength. The total length of the parasitic element 2 is set to, for example, 0.25 wavelength to 0.3 wavelength. The lengths of the base end portions of the feeding element 1 and the parasitic element 2 (the length from the conductor plate 4 to the bent position) are set to, for example, 0.05 wavelength to 0.25 wavelength. The total length of the feed element 1 is set to 1/4 times the wavelength of the resonance frequency of the antenna device of FIG.

  As an example, the length of the proximal end portion (from the feeding point 3 to the bent position) of the power feeding element 1 is 0.1 wavelength, and the length of the distal end portion (from the bent position to the distal end position) is 0.2 wavelength. The length of the base end portion (from the connection position of the conductor plate 4 to the bent position) of the parasitic element 2 is 0.1 wavelength, and the length of the tip end portion (from the bent position to the tip position) is 0.16 wavelength. The distance (connection position interval) between the feed point 3 of the feed element 1 and the connection point of the conductor plate 4 of the parasitic element 2 is 0.387 wavelength, and the gap between the tips of the feed element 1 and the parasitic element 2 is 0.034 wavelength. It is. The connection position of the switch SW1 is a position of 0.14 wavelength from the bent position of the parasitic element 2 toward the tip, and the connection position of the switch SW2 is a connection point between the parasitic element 2 and the conductor plate 4.

  The power supplies PS1 and PS2 are controlled by the control unit 8 so that the + side terminal is set to 3V and the − side terminal is set to 0V, or the + side terminal is set to 0V and the − side terminal is set to 3V.

  When the + side terminal of the power supply PS1 is 3V and the − side terminal is 0V, the diode D1 is forward biased, and a current flows through the diode D1. That is, this state corresponds to a state in which the switch SW1 is on. On the other hand, when the positive side terminal of the power source PS1 is 0V and the negative side terminal is 3V, the diode D1 is reverse-biased and no current flows through the diode D1. That is, this state corresponds to a state in which the switch SW1 is off.

  When the + side terminal of the power source PS2 becomes 3V and the − side terminal becomes 0V, a forward bias is applied to the diode D2, and a current flows through the diode D2. That is, this state corresponds to a state in which the switch SW1 is on. On the other hand, when the positive side terminal of the power source PS2 is 0V and the negative side terminal is 3V, the diode D2 is reverse-biased and no current flows through the diode D2. That is, this state corresponds to a state in which the switch SW1 is off.

  When both of the diodes D1 and D2 are forward biased, it corresponds to the state 1 in FIG. 4 and a directivity pattern extending in the Y direction in FIG. 6 is obtained as shown in FIG. When the diode D1 is reverse-biased and the diode D2 is forward-biased, a directivity pattern extending in the X direction in FIG. 6 is obtained as shown in FIG. When the diode D2 is reverse-biased, it corresponds to the state 3 in FIG. 4, and a radiation pattern of only the feed element 1 is obtained as shown in FIG. 5C.

  Thus, in the first embodiment, the distal end portion of the feed element 1 and the distal end portion of the parasitic element 2 are arranged close to each other, and the switches SW1 and SW2 are provided at the proximal end portion and the distal end portion of the parasitic element 2. By providing and arbitrarily turning these switches on and off, the electrical length of the parasitic element 2 can be variably controlled, and the directivity pattern of the antenna device can be greatly varied.

(Second Embodiment)
The second embodiment is characterized in that the shape of the feeding element 1 is different from that of the first embodiment.

  FIG. 7 is a diagram showing a schematic shape of an antenna device according to the second embodiment of the present invention. In the antenna device of FIG. 7, the shape of the feed element 1 is different from that of the feed element 1 of FIG. Specifically, the matching element 11 is added to the feeding element 1 of FIG. The matching elements 11 are connected to the base end portion of the power feeding element 1, and are provided two symmetrically with the power feeding point 3 interposed therebetween. The structure of the parasitic element 2 is the same as that shown in FIG.

  The reason for adding such a matching element 11 is to prevent the impedance of the antenna device viewed from the feeding point 3 from changing even when the switches SW1 and SW2 on the parasitic element 2 are turned on / off. Yes, by providing the matching element 11, the matching between the feeder line 10 and the antenna device is not shifted.

  The matching element 11 is not limited to the linear element as shown in FIG. 7, and various shapes are conceivable.

  FIG. 8 is a view showing a first modification of the matching element 11. The matching element 11 is connected to the proximal end portion having the feeding point 3 substantially in parallel, and both the proximal end portion and the matching element 11 are connected to the distal end portion 1a.

  FIG. 9 is a view showing a second modification of the matching element 11. Matching elements 11 are connected to both ends of the feed point 3, and only the base end is connected to the tip 1a.

  Also in the second embodiment, similarly to the first embodiment, by using an image current, only the upper half of the antenna elements of FIGS. 7 to 9 is electrically equivalent to FIGS. 7 to 9. Characteristics can be obtained.

  FIG. 10 is a diagram showing a schematic shape of an antenna device having the same electrical characteristics as those in FIG. A matching element 11 having one end connected to the base end near the feeding point 3 is provided. In the case of the antenna device of FIG. 10, the impedance is determined by the sum of the length of the matching element 11 and the length from the connection point of the matching element 11 to the tip position of the feed element 1.

  FIG. 11 is a diagram showing a schematic shape of an antenna device having the same electrical characteristics as those in FIG. In the case of the antenna device of FIG. 11, the impedance depends on the length from the connection position of the matching element 11 to the conductor plate 4 to the tip position of the feed element 1 and the length from the feed point 3 to the tip position of the feed element 1. It is determined.

  FIG. 12 is a diagram showing a schematic shape of an antenna device having the same electrical characteristics as those in FIG. In the case of the antenna device of FIG. 12, the impedance depends on the length from the connection point of the matching element 11 to the conductor plate 4 to the tip position of the feed element 1 and the length from the feed point 3 to the tip position of the feed element 1. It is determined.

  FIG. 13 is a detailed block diagram of an antenna apparatus according to the second embodiment of the present invention. In FIG. 13, the same reference numerals are given to components common to FIG. 6, and the differences will be mainly described below. The antenna device of FIG. 13 is obtained by adding a matching element 11 having the same shape as that of FIG. 10 to the antenna device of FIG. The structure of the parasitic element 2 is the same as that of FIG. 6, and diodes D1 and D2 are provided as switches SW1 and SW2 on the parasitic element 2, and by applying a forward bias or a reverse bias to these diodes D1 and D2, The electrical length of the parasitic element 2 is changed.

  Thus, in the case of the antenna device according to the second embodiment shown in FIG. 13, since the matching element 11 is provided, the impedance of the antenna device does not shift even when the electrical length of the parasitic element 2 changes, and the antenna device And the feeder line 10 are more consistent.

  In each embodiment described above, two switches SW1 and SW2 (diodes D1 and D2) are provided on the parasitic element 2, but the number is not limited as long as the number of switches is one or more.

The figure which shows schematic shape of the antenna device which concerns on the 1st Embodiment of this invention. FIG. 3 is a diagram illustrating a schematic shape of an antenna device that is a modification of the antenna device of FIG. 1 and that exhibits the same electrical characteristics as the antenna device of FIG. 1. The figure which shows a mode that the phase difference of the electric current of the feed element 1 and the parasitic element 2 changes with ON / OFF of switch SW1, SW2. The figure which shows the relationship between ON / OFF of switch SW1, SW2 and the directivity of an electromagnetic wave. The figure which shows the directivity pattern which shows the directivity of an electromagnetic wave. The block diagram which shows an example of the antenna apparatus which automated on / off control of switch SW1, SW2. The figure which shows schematic shape of the antenna device which concerns on the 2nd Embodiment of this invention. The figure which shows the 1st modification of the element 11 for matching. The figure which shows the 2nd modification of the element 11 for a matching. FIG. 8 is a diagram illustrating a schematic shape of an antenna device having the same electrical characteristics as FIG. 7. FIG. 9 is a diagram showing a schematic shape of an antenna device having the same electrical characteristics as FIG. FIG. 10 is a diagram illustrating a schematic shape of an antenna device having the same electrical characteristics as FIG. 9. The detailed block diagram of the antenna device which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feeding element 2 Parasitic element 3 Feeding point 4 Conductor plate 5 Dielectric substrate 6,7 Inductor element 8 Control part 9 Received power detection part

Claims (9)

A feed element having an electrical length that resonates at a predetermined frequency and having a feed point and a bent first tip;
A parasitic element having a second tip portion that is disposed in close proximity to the first tip portion and bent;
An antenna device comprising: an electrical length switching unit provided on at least one of the parasitic elements and capable of changing an electrical length of the parasitic element.   The antenna apparatus according to claim 1, wherein the electrical length switching unit is arranged at a position where a phase difference between currents flowing through the feeding element and the parasitic element changes due to the switching.   A matching element having one end connected between the feeding point and the first tip is provided so that the impedance viewed from the feeding point does not change even when switching is performed by the electrical length switching unit. The antenna device according to claim 1 or 2.   The impedance viewed from the feeding point is determined by a sum of a length of the matching element and a length from a connection point of the matching element to the first tip portion. Antenna device. A conductive plate to which the feeding point is arranged and to which one end of the parasitic element is connected;
The antenna device according to claim 1, wherein the feeding element and the parasitic element are arranged on one surface of the conductor plate. The feeding element has a symmetric structure with respect to a plane passing through the feeding point,
The antenna device according to claim 1, wherein the parasitic element has a symmetrical structure with respect to the surface. The parasitic element includes the second distal end portion and a proximal end portion connected to the second distal end portion,
The electrical length switching unit
A first switching portion provided at a predetermined position on the base end portion;
The antenna device according to claim 1, further comprising a second switching unit provided at a predetermined position on the second tip.   The electrical length of the parasitic element is set to a value corresponding to a length obtained by closing the first and second switching portions and combining the base end portion and the second distal end portion, or setting the first switching portion to Close and open the second switching unit to set a value corresponding to the length of the base end, or open the first switching unit and set the length of the parasitic element not to operate at the predetermined frequency The antenna device according to claim 7, further comprising: a switching control unit that performs switching control of whether to set to the antenna device. A switching control unit for controlling switching of the electrical length switching unit;
The electrical length switching unit is at least one diode,
The antenna apparatus according to claim 1, wherein the switching control unit varies the electrical length of the parasitic element by controlling a direction of a voltage applied to the diode.

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