JP5673472B2 - Array antenna device - Google Patents

Description

The present invention relates to an array antenna apparatus, and more particularly to a technique for increasing the ratio of the gain of a main radiation component to the gain of a polarization orthogonal to the main radiation component in the array antenna apparatus.

  The array antenna apparatus includes an excitation element for receiving a radio signal, and a plurality of non-excitation elements provided at a predetermined distance from the excitation element, and a plurality of variable elements connected to the respective non-excitation elements. An array antenna apparatus is known in which directivity changes as a reactance value of a reactance element changes (for example, Patent Document 1). This type of array antenna apparatus is often referred to as an electronic scanning waveguide array antenna apparatus, but is hereinafter simply referred to as an array antenna apparatus.

  In the array antenna device, the excitation element and the non-excitation element are provided on a disk-shaped ground conductor in a state of being insulated from the ground conductor. In general, the ground conductor has a radius set to ½ of the wavelength λ of the received radio wave, and the non-excitation element is arranged so that the distance from the center of the ground conductor is ¼ of the wavelength λ. The

  This array antenna apparatus may be used for direction detection of a wireless terminal (for example, a wireless tag) by utilizing the fact that directivity is variable. The array antenna apparatus is usually installed so as to perform horizontal plane scanning, and in this case, has good directivity with respect to vertical polarization. Therefore, if the wireless tag that is the target of direction detection transmits vertical polarization, direction detection with high accuracy becomes possible.

  However, when the wireless tag is carried by a person, the wireless tag is in various directions. Therefore, in the radio wave transmitted by the wireless tag, the horizontal polarization may become the main radiation polarization. Since the array antenna device is not sharp in directivity with respect to the horizontal polarization, if the direction of the wireless tag is estimated by the horizontal polarization, the accuracy cannot be sufficiently obtained. Therefore, even if the radio wave transmitted by the wireless tag has a strong horizontal polarization component and a weak vertical polarization component, it is desired that the array antenna apparatus perform direction estimation based on the vertical polarization component. For this purpose, the array antenna device is desired to have a vertical polarization gain as high as possible as compared to a horizontal polarization gain.

The A-array antenna system, because to be a main radiation components vertically polarized wave is received is required, when viewed as a vertical polarization as the main radiation components, the main radiation components for polarization gain which is perpendicular to the main radiation components A larger gain ratio means that the vertical polarization gain is higher than the horizontal polarization gain. Therefore, in the array antenna apparatus, it is desired to increase the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component when this vertical polarization at the time of reception is viewed as the main radiation component. . Although there is no clear description in Patent Document 1 that the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component is increased , the radius of the ground conductor (finite reflector 1 in Patent Document 1) is set. It can be inferred that the main radiation component gain in the horizontal plane can be increased and the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component at the time of reception can be increased . (Such as paragraph 0017).

JP 2002-16427 A

  However, if the radius of the ground conductor is increased, the array antenna device is increased in size, which is not preferable.

The present invention has been made based on this circumstance, and the object of the present invention is to control the gain of the main radiation component with respect to the gain of the polarization orthogonal to the main radiation component while suppressing an increase in the size of the apparatus. An object of the present invention is to provide an array antenna device that can increase the size of the antenna.

In order to achieve the object, the invention according to claim 1
An excitation element for receiving a radio signal and a plurality of non-excitation elements provided at a predetermined interval from the excitation element are provided on a circular ground conductor in a state insulated from the ground conductor. The array antenna device in which the directivity changes as the reactance values of a plurality of variable reactance elements connected to the non-excitation elements change,
A conductor disk is disposed on the side of the excitation element and the non-excitation element with respect to the ground conductor,
The conductor disk is parallel to the ground conductor, its axis passes through the ground conductor, and the distance d between the upper ends of the excitation element and the non-excitation element and the lower surface of the conductor disk is a conductor circle. The radius r of the plate satisfies any of the following conditions (1) to (8).
(1) 0.008λ <d ≦ 0.074λ, 0.37λ ≦ r ≦ 0.59λ
(2) 0.074λ <d ≦ 0.082λ, 0.37λ ≦ r ≦ 0.60λ
(3) 0.082λ <d ≦ 0.270λ, 0.37λ ≦ r ≦ 0.65λ
(4) 0.270λ <d ≦ 0.278λ, 0.37λ ≦ r ≦ 0.61λ
(5) 0.278λ <d ≦ 0.286λ, 0.38λ ≦ r ≦ 0.59λ
(6) 0.286λ <d ≦ 0.294λ, 0.38λ ≦ r ≦ 0.49λ
(7) 0.294λ <d ≦ 0.302λ, 0.38λ ≦ r ≦ 0.45λ
(8) 0.302λ <d ≦ 0.310λ, 0.38λ ≦ r ≦ 0.41λ
Note that λ is the wavelength of the radio wave received by the array antenna apparatus.

By arranging the conductor disk satisfying the above conditions, the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component when received is the same as that of the array except that there is no conductor disk. It has been confirmed by simulation that it is significantly larger than an antenna device (hereinafter referred to as a conventional array antenna device). For example, in the conventional array antenna apparatus, when the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component is 15.6 dB, the array antenna apparatus of the present invention is orthogonal to the main radiation component. The ratio of the gain of the main radiation component to the gain of the polarization is at least 16.8 dB. Moreover, since the radius r of the conductor disk is 0.65λ at the maximum, considering that the general radius of the ground conductor is 0.5λ even if the size of the conductor disk is maximized, the array is not so much. The antenna device is not enlarged. Also, the radius of the conductor disk can be 0.5λ or less, and in this case, the radial dimension of the array antenna device is not increased at all. Therefore, the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component can be increased while suppressing an increase in the size of the apparatus.

It is a block diagram of a radio | wireless terminal direction detection apparatus provided with the antenna part 1 which is an array antenna apparatus with which this invention was applied. It is a figure which expands and shows the antenna part. It is a figure which compares and shows the array antenna apparatus of this embodiment, and the conventional array antenna apparatus directivity gain. It is a figure which shows the vertical polarization gain (dB) computed by simulation, changing the radius r of the conductor disc 19, and the distance d between the conductor disc 19 and the elements 10 and 11. FIG. It is a figure which shows the horizontal polarization gain (dB) calculated by simulation, changing the radius r of the conductor disc 19, and the distance d between the conductor disc 19 and the elements 10 and 11. FIG. FIG. 6 is a diagram showing the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component, which can be calculated from the simulation results of FIGS. 4 and 5.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a wireless terminal direction finding device including an antenna unit 1 which is an array antenna device to which the present invention is applied.

  This wireless terminal direction finding device includes an antenna unit 1, a power detection circuit 5, and a direction finding computer 6. The antenna unit 1 is an electronically controlled waveguide array antenna device, which will be described later in detail with reference to FIG. 2, and includes one excitation element 10 and six non-excitation elements 11A to 11F. The excitation element 10 and the non-excitation elements 11A to 11F are provided on the ground conductor 17 so as to be insulated from the ground conductor 17. A conductor disk 19 is disposed above the excitation element 10 and the non-excitation elements 11A to 11F.

  A feeding point of the excitation element 10 is connected to the power detection circuit 5 via the coaxial cable 20, and a reception signal indicating a radio wave transmitted from an external wireless terminal and received by the excitation element 10 is supplied to the power detection circuit 5. Is done.

  Variable reactance circuits 18A to 18F are connected to the non-excitation elements 11A to 11F, respectively. The variable reactance circuit 18 is the same circuit as that generally used in an electronically controlled waveguide array antenna apparatus. For example, a variable reactance element (for example, a variable reactance element) whose reactance value changes when a bias voltage is applied. A circuit including a capacitor diode). This circuit is connected to the ground conductor 17 at a high frequency, and the reactance value is electronically changed by a variable reactance control unit 61 (to be described later) of the direction detection computer 6. By changing the reactance value, the azimuth angle φ of the antenna unit 1 changes.

  The power detection circuit 5 is a circuit that detects the power level (power value) of the reception signal supplied from the excitation element 10. As the power detection circuit 5, various known circuits for detecting the power of the radio signal can be used. For example, the power detection circuit 5 has a circuit configuration including a diode detector. A power value signal indicating the power value detected by the power detection circuit 5 is supplied to the direction detection unit 62 of the direction detection computer 6 via an AD conversion circuit (not shown).

  The direction detection computer 6 includes a CPU, a ROM, a RAM, and the like (all not shown), and the CPU executes a program stored in the ROM while using a temporary storage function of the RAM, so that a variable reactance can be obtained. It functions as the control unit 61 and the direction detection unit 62.

  The variable reactance control unit 61 refers to a digital voltage value stored in a memory (not shown) and converts the digital voltage value into an analog bias voltage value using six built-in DA converters (not shown). The bias voltage value is output as reactance value signals C11 (θ) to C16 (θ) to the variable reactance circuits 18A to 18F. The digital voltage values are stored for a plurality of directional beam patterns that form a beam at a plurality of preset azimuth angles (for example, every 30 ° from 0 ° to 330 °). The variable reactance control unit 61 sequentially changes the directional beam pattern to a plurality of azimuth angles by switching the reactance value signals C11 (θ) to C16 (θ). The digital voltage value stored in the memory is a value obtained in advance based on experiments.

  The direction detection unit 62 performs direction detection of the wireless terminal based on the power value supplied from the power detection circuit 5 and the azimuth angle when the reception signal of the power value is received. For example, a power value pattern indicating a change in power value with respect to the azimuth angle is created, and the azimuth angle indicating the peak value in the pattern is determined as the direction of the wireless terminal.

  FIG. 2 is an enlarged view of the antenna unit 1. The excitation element 10 and the six non-excitation elements 11A to 11F are all in the shape of a straight bar and protrude vertically from the ground conductor 17. These elements 10 and 11 have the same length from the upper surface of the ground conductor 17 to the upper end of the element, which is about λ / 4 here. The excitation element 10 is disposed at the center of the ground conductor 17, while the non-excitation elements 11 </ b> A to 11 </ b> F are provided at equal intervals on the circumference centered on the excitation element 10. The distance from the element 11 is also set to λ / 4. Note that λ is the wavelength of the radio wave received by the antenna unit 1.

  The ground conductor 17 is a disk-shaped member having a sufficiently large width with respect to the excitation element 10 and the non-excitation elements 11A to 11F, and has a radius λ / 2 here.

  The conductor disk 19 is also a disk-shaped member like the ground conductor 17. The conductor disk 19 is provided above the excitation element 10 and the non-excitation element 11, that is, on the side of the excitation element 10 and the non-excitation element 11 with respect to the ground conductor 17, and the excitation element 10 and It is provided apart from the non-excitation element 11. The conductor disk 19 is parallel to the ground conductor 17. In the example of FIG. 2, the conductor disk 19 is disposed at a position where the axis of the conductor disk 19 coincides with the axis of the ground conductor 17. The conductor disk 19 is fixed to an antenna housing (not shown) that houses the conductor disk 19 together with the ground conductor 17, the excitation element 10, and the non-excitation element 11.

Here, as shown in FIG. 2, the distance between the upper end of the excitation element 10 or the non-excitation element 11 and the lower surface of the conductor disk 19 is d, and the radius of the conductor disk 19 is r. When the distance d and the radius r satisfy any one of the following conditions (1) to (8) , the main radiating component is present due to the presence of the conductor disk 19 compared to the case where the conductor disk 19 is not present. The ratio of the gain of the main radiation component to the gain of the polarization orthogonal to is improved.
(1) 0.008λ <d ≦ 0.074λ, 0.37λ ≦ r ≦ 0.59λ
(2) 0.074λ <d ≦ 0.082λ, 0.37λ ≦ r ≦ 0.60λ
(3) 0.082λ <d ≦ 0.270λ, 0.37λ ≦ r ≦ 0.65λ
(4) 0.270λ <d ≦ 0.278λ, 0.37λ ≦ r ≦ 0.61λ
(5) 0.278λ <d ≦ 0.286λ, 0.38λ ≦ r ≦ 0.59λ
(6) 0.286λ <d ≦ 0.294λ, 0.38λ ≦ r ≦ 0.49λ
(7) 0.294λ <d ≦ 0.302λ, 0.38λ ≦ r ≦ 0.45λ
(8) 0.302λ <d ≦ 0.310λ, 0.38λ ≦ r ≦ 0.41λ
In the A array antenna apparatus, vertical polarization, be the main radiation component of the received is required, when viewed as a main emission component of the received vertically polarized wave, horizontally polarized wave, perpendicular to the main radiation components polarized It is a wave.

  FIG. 3 shows a comparison of directivity gains at an elevation angle = 0 between the array antenna device of the present embodiment and the conventional array antenna device (same configuration as the array antenna device of the present embodiment except that the conductor disk 19 is not provided). FIG. FIG. 3A is a diagram comparing the directivity gain of vertical polarization, and FIG. 3B is a diagram comparing the directivity gain of horizontal polarization. In FIG. 3, the array antenna apparatus of this embodiment is a case where the distance d is 30 mm, the radius r is 60 mm, and the wavelength λ is 122.4 mm (2.45 GHz) in FIG.

  Further, the gain of FIG. 3 is calculated by simulation using a computer. In the simulation, the ground conductor 17 and the conductor disk 19 are both perfect conductors, and the thicknesses are both 0.02 mm. It is said. However, since the current flows only to the surface of the ground conductor 17 due to the skin effect, it is known that there is no difference in characteristics at 20 μm or more. Similarly, it is considered that the thickness of the conductor disk 19 does not affect the antenna characteristics. In addition, regarding the material, if what is usually used as the ground conductor of the antenna is also used for the conductor disk 19, it is considered that the result is almost the same as this simulation.

As can be seen from FIG. 3 (B), the horizontal polarization directivity gain is reduced as a whole as compared with the conventional apparatus due to the presence of the conductor disk 19. On the other hand, as can be seen from FIG. 3A, the vertical polarization directivity gain hardly changes depending on the presence or absence of the conductor disk 19. Therefore, the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component at the time of reception of the device of the present embodiment including the conductor disk 19 is higher than that of the conventional device.

Next, if the distance d and the radius r are in the above ranges (1) to (8), the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component at the time of reception than the conventional device is It will be described with reference to the large Do Rukoto simulation results. FIG. 4 is a vertical polarization gain (dB) calculated by simulation while changing the radius r of the conductor disk 19 and the distance d between the conductor disk 19 and the elements 10 and 11, and the reactance value is set to a desired value. This is the vertical polarization gain at the azimuth angle φ when the azimuth angle φ is assumed. In this simulation, the frequency is 2.45 GHz, that is, the wavelength λ is about 122.4 mm.

  On the other hand, FIG. 5 shows the horizontal polarization gain (dB) calculated by simulation while changing the radius r of the conductor disk 19 and the distance d between the conductor disk 19 and the elements 10 and 11, This is the maximum horizontal polarization gain within the 360 ° azimuth when the reactance value is the desired azimuth angle φ.

Then, by subtracting the horizontal polarization gain under the condition corresponding to the vertical polarization gain from the horizontal polarization gain shown in FIG. 5 from the vertical polarization gain shown in FIG. 4, various distances d and radii r are obtained. The ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component at can be calculated. FIG. 6 shows the ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the main radiation component at various distances d and radii r.

In FIG. 6, the range surrounded by the thick line is a range defined by the distance d and the radius r described in the claims. Within this range, the main radiation component and the range are compared with those of the conventional array antenna apparatus. The ratio of the gain of the main radiation component to the gain of orthogonal polarization is significantly increased . Specifically, the ratio of the gain of the main radiation components for polarization gain which is perpendicular to the main radiation components of a conventional array antenna apparatus whereas a 15.6DB, Within the range shown by the thick line in FIG. 6, the main The ratio of the gain of the main radiation component to the gain of the polarization orthogonal to the radiation component is at least 16.8 dB. In FIGS. 4 and 5, the range corresponding to FIG. 6 is surrounded by a thick line.

In this way, the conductor disk 19 is arranged on the element 10, 11 side with respect to the ground conductor 17 so as to be parallel to the ground conductor 17 and coincide with the axis, and the conductor disk 19 is arranged on the elements 10, 11. If the distance d and the radius r satisfy the conditions of any of the above (1) to (8), the polarization is orthogonal to the main radiation component at the time of reception as compared with the conventional array antenna apparatus. The ratio of the gain of the main radiation component to the gain of can be significantly increased .

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, It can implement in various changes within the range which does not deviate from a summary.

  For example, in the above-described embodiment, the conductor disk 19 is disposed at a position where its axis coincides with the axis of the ground conductor 17. However, the present invention is not limited to this, and the axis of the conductor disk 19 only needs to pass through the ground conductor 17.

DESCRIPTION OF SYMBOLS 1 Antenna part, 5 Power detection circuit, 6 Direction detection computer, 10 Excitation element, 11 Non-excitation element, 17 Ground conductor, 18 Variable reactance circuit, 19 Conductor disk, 20 Coaxial cable, 61 Variable reactance control part, 62 Direction detection Part

Claims (1)

An excitation element for receiving a radio signal and a plurality of non-excitation elements provided at a predetermined interval from the excitation element are provided on a circular ground conductor in a state insulated from the ground conductor. The array antenna device in which the directivity changes as the reactance values of a plurality of variable reactance elements connected to the non-excitation elements change,
A conductor disk is disposed on the side of the excitation element and the non-excitation element with respect to the ground conductor,
The conductor disk is parallel to the ground conductor, its axis passes through the ground conductor, and the distance d between the upper ends of the excitation element and the non-excitation element and the lower surface of the conductor disk is a conductor circle. An array antenna apparatus, wherein a radius r of the plate satisfies any of the following conditions (1) to (8):
(1) 0.008λ <d ≦ 0.074λ, 0.37λ ≦ r ≦ 0.59λ
(2) 0.074λ <d ≦ 0.082λ, 0.37λ ≦ r ≦ 0.60λ
(3) 0.082λ <d ≦ 0.270λ, 0.37λ ≦ r ≦ 0.65λ
(4) 0.270λ <d ≦ 0.278λ, 0.37λ ≦ r ≦ 0.61λ
(5) 0.278λ <d ≦ 0.286λ, 0.38λ ≦ r ≦ 0.59λ
(6) 0.286λ <d ≦ 0.294λ, 0.38λ ≦ r ≦ 0.49λ
(7) 0.294λ <d ≦ 0.302λ, 0.38λ ≦ r ≦ 0.45λ
(8) 0.302λ <d ≦ 0.310λ, 0.38λ ≦ r ≦ 0.41λ
Note that λ is the wavelength of the radio wave received by the array antenna apparatus.

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