JP2017038123A - Multiple frequency antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for easy adjustment of the directivity for each frequency, without taking extensive measures.SOLUTION: First and second log periodic antennas 2a, 2b are placed while inclining the whole dielectric substrate 21, so that the distance to a reflector 1 increases as the element length from elements on the side of feeding points 61, 62 becomes longer. The angle of tilt of the dielectric substrate 21 for the reflector 1 and the distance of the feeding points 61, 62 are set so that the distance of respective elements 22, 23 and the reflector 1 become substantially constant, when converted to the wavelength of resonance frequency of respective elements.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multi-frequency antenna device using a log periodic antenna.

  For example, as an antenna device attached to a wall surface in a tunnel, a Yagi type antenna device having directivity in two opposite directions is known. When this type of antenna device is used, radio waves can be efficiently radiated in the longitudinal direction of the tunnel.

  By the way, mobile phone communication systems are being increased in frequency over a wide band in order to increase user demand and further improve communication quality, and broadband characteristics are also required for antenna devices to be used. As a directional antenna device having such a broadband characteristic, an antenna device using a log periodic antenna (also called a log-peri antenna) is known. For example, a logarithmic periodic antenna has a plurality of dipole elements designed so that the element length is sequentially increased logarithmically on both surfaces of a substrate. The antenna apparatus has two such log periodic antennas. use. The two log-periodic antennas are arranged opposite to each other with a certain distance from the reflector, with the short element lengths facing each other, and the elements with the shortest element length are arranged. It is comprised so that electric power may be supplied to the done side. According to the antenna device using such a log periodic antenna, each element constituting the log periodic antenna resonates at a different frequency, so that the antenna device as a whole can achieve wideband characteristics over multiple frequencies. (For example, refer to Patent Document 1).

JP 2006-229337 A

  However, in an antenna device using a log periodic antenna, the directivity for each frequency depends on the distance between the reflector and each element. For this reason, in a configuration in which two log periodic antennas are arranged opposite to each other with their short element lengths facing each other in the opposite direction and arranged parallel to the reflector with a certain distance, directivity depends on the frequency. It is difficult to adjust the directivity for each frequency.

  The present invention has been made paying attention to the above circumstances, and the object of the present invention is to use a multi-logarithmic periodic antenna that makes it possible to easily adjust the directivity for each frequency without taking a major measure. The object is to provide a frequency antenna device.

  To achieve the above object, according to a first aspect of the present invention, there is provided a first logarithm and a second logarithm in which a plurality of elements whose element lengths are sequentially increased in a logarithmic period are arranged on both surfaces of a dielectric substrate. An antenna unit in which a periodic antenna is arranged so that arrangement directions of the plurality of elements are opposite to each other; a feeding circuit that feeds a high-frequency signal to the first and second log periodic antennas; A multi-frequency antenna apparatus comprising: a reflector disposed apart from the first and second log periodic antennas, wherein the first and second log periodic antennas are elements of the plurality of elements. As the length becomes longer, the plurality of elements and the reflecting plate are disposed so as to be inclined with respect to the reflecting plate so that the distance between the plurality of elements and the reflecting plate is increased. Element resonance In which was set to be constant within a range set in advance when converted to a wavelength of the wave number.

  In a second aspect of the present invention, an auxiliary reflector is further erected on the reflector in a direction perpendicular to the arrangement direction of the plurality of elements of the first and second log periodic antennas. It is a thing.

  According to a third aspect of the present invention, a pair of waveguides each made of a parasitic element is further arranged on an extension in the arrangement direction of the plurality of elements of the first and second log periodic antennas. It is a thing.

  According to a fourth aspect of the present invention, among the plurality of elements of the first and second log-periodic antennas, the plurality of elements are positioned adjacent to an element that resonates at a frequency that is a target of directivity adjustment. Matching elements having element lengths different from the logarithmic period are further arranged.

  According to the first aspect of the present invention, the directivity of each frequency can be obtained only by adjusting the distance between each element and the reflector for each log periodic antenna, that is, the inclination angle of each log periodic antenna with respect to the reflector. Can be adjusted to an optimum state.

  According to the second aspect of the present invention, the auxiliary reflector is erected in a direction orthogonal to the arrangement direction of the elements of the first and second log periodic antennas on the reflector, so that the reflector itself is made large. It is possible to increase the effective area of the reflector without reducing the size of the reflector, thereby further improving the directivity of the first and second log periodic antennas while maintaining the miniaturization of the multi-frequency antenna device. .

  According to the third aspect of the present invention, by arranging the directors made of parasitic elements on the extension of the arrangement direction of the elements of the first and second log periodic antennas, While maintaining the miniaturization, it becomes possible to control the directivity for a specific frequency band in the use frequency band, and thereby the directivity in the array direction of the elements of the log periodic antenna is set to a desired state. Can be adjusted.

  According to the fourth aspect of the present invention, the element length different from the logarithmic period is located at a position adjacent to the element that resonates at the frequency whose directivity is to be adjusted among the elements of the first and second log periodic antennas. By arranging the matching elements having the above, it is possible to control the voltage standing wave ratio (VSWR) without separately providing a large matching circuit, thereby improving the broadband property.

  That is, according to the present invention, it is possible to provide a multi-frequency antenna device using a log-periodic antenna that can easily adjust the directivity for each frequency without taking a large measure.

The perspective view which shows the outline | summary of a structure of the multifrequency antenna apparatus which concerns on 1st Embodiment of this invention. 1 shows a specific structure of the multi-frequency antenna device shown in FIG. 1, (a) is a front view thereof, (b) is a side view seen from the long side, and (c) is seen from the short side. Side view. The figure which shows an example of the arrangement | sequence pattern of the element in the logarithmic periodic antenna shown in FIG. The figure which shows antenna operation | movement at the time of making a logarithmic periodic antenna incline with respect to a reflecting plate in the multifrequency antenna apparatus shown in FIG. 1, and not installing an auxiliary reflecting plate and a director. The figure which shows the space | interval of a log periodic antenna and a reflecting plate at the time of arrange | positioning a log periodic antenna with respect to a reflecting plate. The figure which shows the case where the space | interval of a logarithmic periodic antenna and a reflecting plate is made constant. The figure which shows an example of the directivity of each of E surface and H surface in 750 MHz obtained on the conditions shown in FIG. The figure which shows an example of the directivity of each of E surface and H surface in 950 MHz obtained on the conditions shown in FIG. The figure which shows an example of the directivity of each of E surface and H surface in 750 MHz at the time of arrange | positioning a logarithmic periodic antenna in parallel with 150 mm space | interval with respect to the reflecting plate. The figure which shows an example of the directivity of each of E surface and H surface in 950 MHz at the time of arrange | positioning a logarithmic periodic antenna in parallel with 150 mm space | interval with respect to the reflecting plate. The figure which shows an example of the directivity of each of E surface and H surface in 750 MHz at the time of arrange | positioning a logarithmic periodic antenna in parallel with the space | interval of 120 mm with respect to a reflecting plate. The figure which shows an example of the directivity of each of the E surface and H surface in 950 MHz at the time of arrange | positioning a logarithmic periodic antenna in parallel with the space | interval of 120 mm with respect to the reflecting plate. The figure which displayed as a list the measurement value of the half value width of the directivity of each of the E surface and the H surface shown in FIGS. The figure which shows antenna operation | movement at the time of making a logarithmic period type antenna incline with respect to a reflecting plate, installing an auxiliary reflecting plate, and not installing a director in the multifrequency antenna device shown in FIG. FIGS. 15A and 15B show the directivities of the E plane and the H plane obtained under the conditions shown in FIG. 14. FIG. 15A shows the directivity at 750 MHz, and FIG. 15B shows the directivity at 950 MHz. The figure which shows antenna operation | movement at the time of making a logarithmic periodic antenna incline with respect to a reflecting plate, and installing an auxiliary reflecting plate and a director in the multifrequency antenna device shown in FIG. FIGS. 17A and 17B show the directivities of the E plane and the H plane obtained under the conditions shown in FIG. 16, wherein FIG. 17A shows the directivity at 750 MHz, and FIG. 17B shows the directivity at 950 MHz. The figure which shows the VSWR characteristic at the time of arrange | positioning a matching element as shown in FIG. The figure which shows the VSWR characteristic when not arrange | positioning a matching element. The perspective view which shows the structure of the multifrequency antenna apparatus which concerns on 2nd Embodiment of this invention. The perspective view when the structure of the multifrequency antenna apparatus shown in FIG. 20 is seen from another angle. The figure which shows the structure of the power divider | distributor for 4 distributions used with the multifrequency antenna apparatus shown in FIG. The figure which shows the structure of the conventional power divider | distributor for 4 distributions. The figure which shows the VSWR characteristic by the power divider | distributor for 4 distributions shown in FIG. The figure which shows the passage characteristic which shows the performance of isolation by the power divider | distributor for 4 distributions shown in FIG. The figure which shows the phase characteristic by the power divider | distributor for 4 distributions shown in FIG.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
The multi-frequency antenna device according to the first embodiment of the present invention transmits and receives radio high-frequency for mobile phone communication with a railway vehicle such as a Shinkansen traveling in a tunnel, and is fixed to a wall surface in the tunnel. And configured to have directivity in two directions corresponding to the longitudinal direction of the tunnel, that is, the traveling direction of the railway vehicle. Two types of multi-frequency antenna devices, LowBand and HighBand, are prepared, and LowBand devices cover 700, 800, and 900 MHz. On the other hand, HighBand devices cover 1.5, 1.7, and 2.1 GHz. In the present embodiment, a device for LowBand will be described as an example.

  FIG. 1 is a perspective view showing an outline of the configuration of the multi-frequency antenna device according to the first embodiment of the present invention. The multi-frequency antenna device includes a reflector 1 made of a grounded conductive material, first and second log periodic antennas 2a and 2b that are spaced apart from the reflector 1, and the reflector 1 described above. A pair of auxiliary reflectors 3a and 3b erected on the top and a pair of waveguides 4a and 4b disposed on the far end side of the first and second log periodic antennas 2a and 2b are provided. This multi-frequency antenna device is fixed to the wall surface 5 in the tunnel by a gantry (not shown), and a protective cover (not shown) is attached to the front surface of the device.

  As shown in FIGS. 3A and 3B, the first and second log-periodic antennas 2a and 2b are configured such that the element length is sequentially increased in a logarithmic period on the front and back surfaces of the dielectric substrate 21. An arrangement pattern of a plurality of elements 22 and 23 designed in the above is formed, and feed points 61 and 62 are provided at end portions on the side where the shortest element is arranged, respectively. Each arrangement pattern is formed so as to alternately face each other with the dielectric substrate 21 in between, so that each of the elements 22 and 23 operates as a dipole element having directivity in the longitudinal direction of the tunnel.

  FIG. 2 shows a specific configuration of the multi-frequency antenna device, where (a) is a front view, (b) is a side view seen from the long side, and (c) is a side view seen from the short side. FIG. As shown in the figure, the first and second log periodic antennas 2a and 2b are arranged so as to be opposite to each other in a state in which the side on which the longest element is arranged faces each other. And the high frequency electric power is supplied to the feed points 61 and 62 provided in the front-end | tip part of the logarithmic periodic antenna 2a, 2b via the feed line which is not shown in figure. In the figure, reference numeral 6 denotes a connector for connecting the multi-frequency antenna device to an external wireless unit.

  The first and second log periodic antennas 2 a and 2 b are arranged in a state of being inclined in a C shape with respect to the reflector 1. That is, the entire dielectric substrate 21 is inclined so that the distance from the reflecting plate 1 gradually increases as the element length increases from the elements on the feeding points 61 and 62 side. At this time, the inclination angle of the dielectric substrate 21 with respect to the reflecting plate 1 and the distance between the feeding points 61 and 62 are substantially constant when the distance between each element and the reflecting plate 1 is converted to the wavelength of the frequency at which each element resonates. Is set to be Note that the inclination angles of the logarithmic periodic antennas 2a and 2b and the distances between the feeding points 61 and 62 with respect to the reflecting plate 1 are defined by the spacers 5a and 5b.

  In addition, a pair of auxiliary reflectors 3a and 3b are disposed in a direction orthogonal to the element arrangement direction of the logarithmic periodic antennas 2a and 2b, that is, on both sides in the short side direction of the logarithmic periodic antennas 2a and 2b. These auxiliary reflecting plates 3a and 3b are erected on the reflecting plate 1 by screws. The length in the width direction of the auxiliary reflectors 3a and 3b is set so as to face the element corresponding to the low frequency range whose directivity is to be adjusted, and the dimension in the height direction is the log periodic antenna 2a and 2b. Is set to be shorter than the distance from the reflector 1.

  Further, a pair of waveguides 4a and 4b are disposed on the longitudinal extension of the logarithmic periodic antennas 2a and 2b. These waveguides 4a and 4b are attached to the outer surfaces of the spacers 5a and 5b that support the tip portions of the log periodic antennas 2a and 2b, and operate as parasitic elements with respect to the log periodic antennas 2a and 2b.

  Furthermore, in the log periodic antennas 2a and 2b, the arrangement pattern of the elements 23 formed on the back side of the dielectric substrate 21 includes a matching element between the element with the longest element length and the element with the second longest element length. 24 is formed. The element length of the matching element 24 is set to a length different from the logarithmic period of the element 23.

According to the multi-frequency antenna device configured as described above, the following operational effects can be obtained.
(1) The first and second log periodic antennas 2a, 2b are dielectric so that the distance from the reflecting plate 1 gradually increases as the element length increases from the element on the feeding points 61, 62 side. The entire body substrate 21 is disposed to be inclined. At this time, the inclination angle of the dielectric substrate 21 with respect to the reflecting plate 1 and the distance between the feeding points 61 and 62 are substantially constant when the distance between each element and the reflecting plate 1 is converted to the wavelength of the resonance frequency of each element. Is set as follows. As a result, it becomes possible to easily adjust the directivity for each frequency by suppressing the disturbance of directivity for any frequency.

  The above effect is illustrated by the measurement result of directivity. Now, as shown in FIG. 4, the directivities on the electric field plane E (E plane) and the magnetic field plane H (H plane) are measured. The directivity of the electric field plane E was measured in the maximum radiation direction of the magnetic field plane H (H plane).

  First, as shown in FIG. 5, the first and second log periodic antennas 2a and 2b are inclined with respect to the reflector 1, and the distance between the element having the longest element length and the reflector 1 is h1. When the distance between the element having the shortest element length and the reflector 1 is h2 = 120 mm, the directivity E11 on the E plane and the directivity H11 on the H plane at 750 MHz are respectively shown in FIGS. As shown in b). The directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity E11 of the E plane is E11 ′, and the half-value width is 83.2 °. Similarly, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity H11 of the H plane is H11 ′, and the half value width is 44.7 °.

  Further, when the directivity E12 of the E plane and the directivity H12 of the H plane at 950 MHz are measured under the same conditions, the results are as shown in FIGS. The directivity range at the position of −3 dB from the maximum radiation direction with respect to the directivity E12 of the E plane is 64.0 ° in the half width of E12 ′, and −3 dB from the maximum radiation direction with respect to the directivity H12 of the H plane. The directivity range at the position of H12 ′ has a full width at half maximum of 49.0 °.

  That is, by arranging the first and second log periodic antennas 2a and 2b so as to be inclined with respect to the reflector 1, even for a relatively low frequency band typified by 750 MHz, a relatively high frequency of 950 MHz or more. Good directivity can be obtained on both the E plane and the H plane even in a high frequency band.

  Incidentally, as shown in FIG. 6, when the first and second log periodic antennas 2a and 2b are arranged in parallel to the reflector 1, and the distance between them is h1, h2 = 150 mm, the E plane at 750 MHz The directivity E13 and the directivity H13 of the H plane are as shown in FIGS. 9 (a) and 9 (b), respectively. Then, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity E13 of the E plane is E13 ′, and its half-value width is 80.0 °. Similarly, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity H13 of the H plane is H13 ′, and the half width is 41.2 °.

  Further, when the directivity E14 on the E plane and the directivity H14 on the H plane at 950 MHz are measured under the same conditions, the results are as shown in FIGS. 10 (a) and 10 (b). The directivity range at the position of −3 dB from the maximum radiation direction with respect to the directivity E14 of the E plane is 66.7 ° in the half width of E14 ′, and −3 dB from the maximum radiation direction with respect to the directivity H14 of the H plane. As for the directivity range at the position of H14 ′, the half width of H14 ′ is 52.3 °.

  That is, when the distance between the first and second log periodic antennas 2a, 2b and the reflector 1 is h1, h2 = 150 mm, the half-value widths of the directivity on the E plane and the H plane at 950 MHz are both increased. Pass.

  Similarly, when the first and second log periodic antennas 2a and 2b are arranged in parallel to the reflector 1, and the separation distances are h1 and h2 = 120 mm, the directivity E15 and H of the E plane at 750 MHz The surface directivity H15 is as shown in FIGS. 11 (a) and 11 (b), respectively. The directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity E15 on the E plane is E15 ′, and the half-value width is 87.3 °. Similarly, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity H15 of the H plane is H15 ′, and the half width is 79.5 °.

  Further, when the directivity E16 of the E plane and the directivity H16 of the H plane at 950 MHz are measured under the same conditions, the results are as shown in FIGS. The directivity range at the position of −3 dB from the maximum radiation direction with respect to the directivity E16 of the E plane is 60.0 ° in the half width of E16 ′, and −3 dB from the maximum radiation direction with respect to the directivity H16 of the H plane. In the directivity range at the position of H16 ′, the half width of H16 ′ is 48.5 °.

That is, when the distance between the first and second log periodic antennas 2a, 2b and the reflector 1 is h1, h2 = 120 mm, the half-value widths of the directivity on the E plane and the H plane at 750 MHz are both increased. Pass.
FIG. 13 shows a list of determination results for the half-value widths of the directivities shown in FIGS. As can be seen from the figure, the first and second log periodic antennas 2a and 2b are inclined with respect to the reflector 1, and the distance between the element having the longest element length and the reflector 1 is determined. By setting the distance between the element having the shortest element length of h1 = 150 mm and the reflector 1 to h2 = 120 mm, the directivity can be adjusted to be in a good state both at 750 MHz and 950 MHz. That is, it is possible to adjust the directivity of each frequency to an optimum state only by adjusting the inclination angle of each log periodic antenna 2a, 2b with respect to the reflecting plate 1.

  (2) A pair of auxiliary reflectors 3a and 3b are arranged in a direction orthogonal to the element arrangement direction of the log periodic antennas 2a and 2b, that is, on both sides in the short side direction of the log periodic antennas 2a and 2b. For this reason, it is possible to increase the effective area of the reflector 1 without increasing the size of the reflector 1 itself, thereby maintaining the downsizing of the multi-frequency antenna device and the first and second log periodic antennas. The directivity of 2a and 2b can be further improved. This effect is particularly effective when installed in a place where the installation space is restricted, such as a wall surface in a tunnel.

  Now, as shown in FIG. 14, it is assumed that the directivities on the electric field plane E (E plane) and the magnetic field plane H (H plane) are measured. The directivity of the electric field plane E was measured in the maximum radiation direction of the magnetic field plane H (H plane).

  As shown in FIG. 5, the first and second log periodic antennas 2 a and 2 b are arranged to be inclined with respect to the reflector 1, and on both sides of the log periodic antennas 2 a and 2 b on the reflector 1. It is assumed that the auxiliary reflectors 3a and 3b are erected at the corresponding positions. The inclination angles of the log periodic antennas 2a and 2b are such that the distance between the element with the longest element length and the reflector 1 is h1 = 150 mm, and the distance between the element with the shortest element length and the reflector 1 is as follows. Is set so that h2 = 120 mm.

  When the directivity E21 of the E plane and the directivity H21 of the H plane at 750 MHz are measured under this condition, the result is as shown in FIG. The directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity E21 on the E plane is E21 ′, and the half-value width is 45.1 °. Similarly, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity H21 of the H plane is H21 ′, and its half-value width is 57.4 °.

  Further, when the directivity E22 of the E plane and the directivity H22 of the H plane at 950 MHz are measured under the same conditions, the result is as shown in FIG. Then, the directivity range at the position of −3 dB from the maximum radiation direction with respect to the directivity E22 of the E plane is 62.8 ° in the half width of E22 ′, and the directivity H22 of the H plane is −3 dB from the maximum radiation direction. In the directivity range at the position of H22 ′, the half width of H22 ′ is 49.2 °.

  That is, the first and second log periodic antennas 2a and 2b are inclined with respect to the reflector 1 and the auxiliary reflectors 3a and 3b are provided, so that a relatively low frequency band represented by 750 MHz in particular. The directivity can be further improved for both the E plane and the H plane.

  (3) A pair of waveguides 4a and 4b are arranged on the longitudinal extension of the log periodic antennas 2a and 2b. These directors 4a and 4b operate as parasitic elements for the log-periodic antennas 2a and 2b. For this reason, the directivity in the element arrangement direction of the log periodic antennas 2a and 2b can be further increased without increasing the size of the reflecting plate 1.

  Now, assume that the directivities on the electric field plane E (E plane) and the magnetic field plane H (H plane) are measured as shown in FIG. The directivity of the electric field plane E was measured in the maximum radiation direction of the magnetic field plane H (H plane).

  The first and second log periodic antennas 2a and 2b are inclined with respect to the reflector 1, and the auxiliary reflector is located on the reflector 1 at positions corresponding to both sides of the log periodic antennas 2a and 2b. 3a and 3b are erected, and a pair of directors 4a and 4b are disposed on the longitudinal extension of the log periodic antennas 2a and 2b. The inclination angles of the log periodic antennas 2a and 2b are such that the distance between the element with the longest element length and the reflector 1 is h1 = 150 mm, and the distance between the element with the shortest element length and the reflector 1 is as follows. Is set so that h2 = 120 mm.

  When the directivity E31 on the E surface and the directivity H31 on the H surface at 750 MHz are measured under this condition, the result is as shown in FIG. The directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity E31 on the E plane is E31 ′, and the half-value width is 46.2 °. Similarly, the directivity range at a position of −3 dB from the maximum radiation direction with respect to the directivity H31 of the H plane is H31 ′, and its half-value width is 56.2 °.

  Further, when the directivity E32 of the E plane and the directivity H32 of the H plane at 950 MHz are measured under the same conditions, the result is as shown in FIG. The directivity range at the position of −3 dB from the maximum radiation direction with respect to the directivity E32 of the E plane is 44.7 ° in the half width of E32 ′, and −3 dB from the maximum radiation direction with respect to the directivity H32 of the H plane. The directivity range at the position of H32 ′ has a half width of 37.6 °.

  That is, the first and second log periodic antennas 2a and 2b are inclined with respect to the reflector 1, and the auxiliary reflectors 3a and 3b are disposed on both sides of the log periodic antennas 2a and 2b. By arranging the directors 4a and 4b on the longitudinal extensions of the periodic antennas 2a and 2b, the antenna is directed to both the E plane and the H plane, particularly in a relatively low frequency band typified by 750 MHz. The property can be further improved.

  (4) In the arrangement pattern of the elements 23 formed on the back surface side of the dielectric substrate 21 of the logarithmic periodic antennas 2a and 2b, as shown in FIG. A matching element 24 having an element length different from the logarithmic period is formed between the long elements. The matching element 24 can operate as a stub by itself, and also operates as a kind of loading element that is electromagnetically coupled to an adjacent log periodic element. That is, the feature of the matching element 24 is that it is provided only on one pole (one side of the substrate) of the log periodic antenna, and in terms of electrical terms, it is provided asymmetrically (unbalanced) in the balanced circuit. It is. As a result, it is possible to control the VSWR without separately providing a large matching circuit, thereby improving the broadband property.

  FIG. 18 shows an example of the measurement result of the VSWR characteristics of the antenna device according to the present embodiment, and good characteristics can be obtained over a wide band of 750 MHz to 950 MHz. Incidentally, FIG. 19 shows the VSWR characteristics when the matching element 24 is not provided. As is apparent from FIGS. 18 and 19, according to the present embodiment, it is possible to improve the 750 MHz band VSWR characteristic, thereby obtaining a good VSWR characteristic over a wide band from 750 MHz to 950 MHz.

[Second Embodiment]
In the second embodiment of the present invention, as described in the first embodiment, two pairs of logarithmic periodic antennas arranged in opposite directions with the elements having the longest elements facing each other are provided. A pair of logarithmic periodic antennas are arranged in parallel in a state of being inclined like a roof with respect to the reflector.

  FIG. 20 is a perspective view of the appearance of the multi-frequency antenna device according to the second embodiment of the present invention as seen from the front, and FIG. 21 is a perspective view as seen from the side. As shown in these figures, the multi-frequency antenna device according to the second embodiment is in addition to a pair of log periodic antennas 2a and 2b arranged in opposite directions with the elements having the longest elements facing each other. A pair of log periodic antennas 2c and 2d having the same configuration is provided. The log periodic antennas 2a and 2b and the log periodic antennas 2c and 2d are arranged side by side in a direction orthogonal to the arrangement direction of the elements, and the log periodic antennas 2a and 2c and the log periodic antennas 2b and 2d are arranged in parallel. Each is arranged in a state of being inclined like a roof. In the figure, reference numeral 8 denotes a frame for fixing the multi-frequency antenna device to the tunnel wall surface.

  In the multi-frequency antenna device configured as described above, the log periodic antennas 2a, 2b and 2c, 2d are stacked in the same direction and in the same phase, and the antenna gain is maintained while maintaining good directivity. Can be increased.

  On the reflection plate 1, a power distribution unit 7 for four distributions for supplying high frequency power to the log periodic antennas 2a, 2b and 2c, 2d is disposed. As shown in FIG. 22, the power distributor 7 has a ground pattern formed on one surface of a dielectric substrate and a conductor line pattern formed on the other surface. This conductor line pattern has a step-like conductive line configured so that the line width gradually increases as W1, W2, and W3 over three stages from an input terminal P1 connected to a wireless unit (not shown). The line length of the conductive line is set to ¼ wavelength or less. Further, four protruding lines are formed at the front end side of the conductive line having the largest line width (line width = W3), and feed terminals P2 to P5 are provided at the front end portions of these protruding lines, respectively. These feed terminals P2 to P5 are connected to the feed terminals of the log-periodic antennas 2a, 2b and 2c, 2d via coaxial cables or microstrip lines (not shown). Incidentally, FIG. 23 shows a configuration of a 4-distribution power divider that has been conventionally used, and each of the 4-distributed lines is set to have the same line width.

  When the power divider 7 for four distributions configured in this way is used, the line lengths L1, L2, and L3 and the line widths W1, W2, and W3 of the conductive lines formed so that the line width increases stepwise are obtained. By adjusting the logarithmic periodic antennas 2a, 2b and 2c, 2d, the impedance of the power divider 7 is matched with each other, and the lengths of the four protruding lines on the output side are changed to adjust the logarithmic period. It becomes possible to adjust the phase of the radio signal supplied to the power supply terminals of the mold antennas 2a, 2b and 2c, 2d.

  24, 25, and 26, as shown in FIG. 22, the size of the power distributor 7 is 88 mm in length and 50 mm in width, and the line length is L1 = 27 mm, L2 = 15 mm, and L3 = 16.2 mm. The VSWR characteristics, the transmission characteristics indicating the isolation performance, and the phase characteristics when the line width is set to W1 = 7 mm, W2 = 14 mm, and W3 = 18 mm are shown.

[Other Embodiments]
In the first embodiment, the case where the logarithmic periodic antennas 2a and 2b are inclined with respect to the reflector 1 and the directors 4a and 4b are installed in addition to the auxiliary reflectors 3a and 3b has been described. When the auxiliary antennas 3a and 3b are provided with the antennas 2a and 2b tilted with respect to the reflector 1, or the waveguide 4a with the log periodic antennas 2a and 2b tilted with respect to the reflector. , 4b are also included in the scope of the present invention.

  In the first embodiment, the case where one auxiliary reflector 3a, 3b is disposed on each side of the first and second log periodic antennas 2a, 2b has been described as an example. A total of four auxiliary reflectors may be installed independently for each of the log periodic antennas 2a and 2b. Other than this, the frequency band to be covered, the structure of the log periodic antenna itself, the size, shape, and number of auxiliary reflectors, waveguides, matching elements, and power distributors are within the scope of the present invention. You may choose as follows.

  In short, the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in each embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Reflector plate, 2a, 2b, 2c, 2d ... Log periodic antenna, 3a, 3b ... Auxiliary reflector, 4a, 4b ... Waveguide, 5 ... Tunnel wall surface, 6 ... Connector, 7 ... Power divider, 8 Reference numeral 21: Dielectric substrate, 22, 23: Element, 24: Matching element, 61, 62: Feed point.

Claims (4)

The first and second log periodic antennas in which a plurality of elements whose element lengths are set to be logarithmically increased sequentially are arranged on both surfaces of the dielectric substrate, and the arrangement directions of the plurality of elements are opposite to each other. An antenna unit arranged so that
A power feeding circuit that feeds a high-frequency signal to the first and second log periodic antennas;
A reflector disposed apart from the first and second log periodic antennas,
The first and second log periodic antennas are arranged in a state of being inclined with respect to the reflection plate so that the distance between the plurality of elements and the reflection plate is increased as the element length of the plurality of elements is increased. And the frequency between the plurality of elements and the reflecting plate is set to be constant within a preset range when converted to the wavelength of the resonance frequency of the plurality of elements. Antenna device.   The auxiliary reflector is erected on the reflector in a direction perpendicular to the arrangement direction of the plurality of elements of the first and second log periodic antennas. Multi-frequency antenna device.   3. The waveguide according to claim 1, further comprising a parasitic element disposed on an extension of the array direction of the plurality of elements of the first and second log periodic antennas. Multi-frequency antenna device.   Further, among the plurality of elements of the first and second log-periodic antennas, an element length different from the logarithmic period of the plurality of elements at a position adjacent to an element that resonates at a frequency whose directivity is to be adjusted. The multi-frequency antenna device according to claim 1, wherein a matching element having the above is arranged.