JP2013005100A - Broad-band antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an array antenna in which occurrence of a null point, where the radiation level goes zero, is minimized.SOLUTION: A 6-stage colinear antenna is configured by arranging a series supply 3-stage colinear antenna 10 on the upper stage and a series supply 3-stage colinear antenna 20 on the lower stage. The tilt angle of the 3-stage colinear antenna 10 is differentiated from that of the 3-stage colinear antenna 20, and the 3-stage colinear antenna 10 and the 3-stage colinear antenna 20 are fed in parallel from a distributor 30. The radiation pattern of the 3-stage colinear antenna 10 and the radiation pattern of the 3-stage colinear antenna 20 are synthesized thus producing a radiation pattern in which a null point, where the radiation level goes zero, is minimized.

Description

  The present invention relates to an array antenna with improved radiation characteristics.

As a base station antenna, an array antenna is known in which a plurality of antenna elements are linearly arranged in multiple stages to obtain a sharp beam radiation directivity with high gain and omnidirectional characteristics in a horizontal plane. This array antenna is classified into a series feed type that feeds power by connecting a plurality of antenna elements in series, and a parallel feed type that feeds power to the plurality of antenna elements by distributing power. The directivity characteristic of the array antenna is a directivity characteristic corresponding to the excitation power amount (amplitude value) supplied to each antenna element and the excitation phase.
FIG. 12 shows the configuration of a conventional six-stage collinear antenna 100 that is a series-feed type array antenna. In FIG. 12, the structure of the 1st step element 111 thru | or the 6th step element 116 is shown with sectional drawing.
The conventional six-stage collinear antenna 100 shown in FIG. 12 is configured by stacking six stages of first-stage elements 111 to sixth-stage elements 116 that constitute a dipole antenna. That is, in the six-stage collinear antenna 100, the second stage element 112 is stacked below the first stage element 111, the third stage element 113 is stacked below the second stage element 112, and the third stage element 113 is stacked. A fourth stage element 114 is stacked below, a fifth stage element 115 is stacked below the fourth stage element 114, and a sixth stage element 116 is stacked below the fifth stage element 115. . However, the fourth stage element 114 is omitted. A sleeve feeding portion provided substantially at the center of the first stage element 111 to the sixth stage element 116 is excited by a coaxial cable 120 serving as a transmission line, and a connector 122 is connected to the lower end of the coaxial cable 120 to be coaxial. The cable 120 is introduced into the sixth stage element 116 via the matching unit 121.

  The first-stage element 111 to the sixth-stage element 116 have substantially the same configuration, and are configured by a dipole antenna in which a cylindrical upper sleeve and a lower sleeve are opposed to each other. For example, the first stage element 111 is configured such that an upper sleeve 111a having a joint fitted to the lower end and a lower sleeve 111b having a joint fitted to the upper end face each other. An excitation slot is configured by a configuration in which the upper sleeve 111a and the lower sleeve 111b face each other at a distance Fg10. This excitation slot constitutes the sleeve feeding portion 111c, and the outer conductor of the coaxial cable 120 in the excitation slot is removed, so that the upper sleeve 111a and the lower sleeve 111b are excited by radiation from the inner conductor. However, in the uppermost first stage element 111, the core wire of the coaxial cable 120 is electrically connected to the joint fitted to the lower end of the upper stage sleeve 111a to be fed. The electrical length of the upper sleeve 111a and the lower sleeve 111b constituting the dipole antenna is about λ / 4 when the wavelength of the high-frequency signal to be fed is λ. Further, when the elements 111 to 116 at the respective stages are excited in the same phase, the electrical length of the length L10 of the coaxial cable 120 between the sleeve feeding portions is about 1λ (or an integer multiple thereof). The physical length of the coaxial cable 120 is a length corresponding to the wavelength shortening rate of the coaxial cable 120.

FIG. 13 shows the configuration of a conventional five-stage array antenna 200 that is a series-feed type planar array antenna.
A conventional five-stage array antenna 200 shown in FIG. 13 is configured by stacking five rectangular patch elements on a printed circuit board 210 with good high-frequency characteristics. In the 5-stage array antenna 200, a fourth stage element 214 is stacked on the fifth stage element 215, a third stage element 213 is stacked on the fourth stage element 214, and the third stage element 213 is Is stacked with a second stage element 212, and a first stage element 211 is stacked on the second stage element 212. The elements of the first stage element 211 to the fifth stage element 215 are connected by a strip line 217 serving as a transmission line, and the center of the lower side of each stage element is excited by the strip line 217. An end portion of the strip line 217 led out from the fifth stage element 215 is a feeding point 216 of the five-stage array antenna 200. When the electrical length of the length L20 of the elements 211 to 215 at each stage is about 1λ (or an integer multiple thereof), the elements 211 to 215 at each stage are excited in the same phase.

JP 2010-268289 A

The series-feed type six-stage collinear antenna 100 shown in FIG. 12 has a vertical polarization specification, and FIG. 14 shows the directivity characteristics of the vertical plane when the elements 111 to 116 of each stage are excited in the same phase. Referring to FIG. 14, a sharp main lobe is obtained in the direction of ± about 90 °, and the first null point, the first side lobe, the second null point, and the second side are symmetrically about the main lobe as a base axis. This is a radiation pattern in which a number of null points and side lobes are generated. The directivity characteristic of the horizontal plane at this time is an omnidirectional characteristic although not shown.
The directivity shown in FIG. 14 is that the length L10 between the six-stage sleeve feeding portions is about 1λ (or an integer multiple thereof) so that the six-stage elements 111 to 116 are excited in phase. This is the case. Here, the main lobe of the six-stage collinear antenna 100 can be tilted by changing the electrical length of the length L10. FIG. 15 shows the directivity characteristics of the vertical plane of the six-stage collinear antenna 100 when the electrical length of the length L10 is changed so that a tilt angle of 5 ° is obtained. Referring to FIG. 15, a sharp main lobe tilted downward by about 5 ° (± about 95 ° direction) is obtained, and the first null point, the first side lobe, It can be seen that the radiation pattern has multiple null points and side lobes of the second null point, the second side lobe,.
The directivity shown in FIG. 14 is a simulation result when the 6-stage collinear antenna 100 is designed to have a tilt angle of 5 °. FIG. 16 shows measured data of the directivity of the 6-stage collinear antenna 100 designed in this way. . Referring to FIG. 16, a sharp main beam tilted by about 4 ° in a direction of about ± 94 ° is obtained, and the first null point, the first side lobe, and the second null are symmetrically about the main lobe. It is a radiation mode in which a number of null points and side lobes are generated.

  By the way, since the radiation level at the null point is almost 0, there is a possibility that the irradiation area corresponding to the null direction may become unreceivable, or the error rate may increase in communication, image reception, etc. and normal reception may not be possible. . In the conventional series-feed type six-stage collinear antenna 100 shown in FIG. 12, a number of null points are generated between the main lobe and each side lobe, and the null point induces level reduction and level fluctuation. was there.

  Accordingly, an object of the present invention is to provide an array antenna in which a null point where the radiation level becomes 0 is not generated as much as possible.

  In order to achieve the above object, an array antenna of the present invention is a series feeding type that feeds power to a plurality of antenna elements in series and has a first tilt antenna directivity characteristic; It is a series feed type that feeds power to a plurality of antenna elements in series, has a directivity characteristic of a second tilt angle different from the first tilt angle, and is linearly arranged with the first array antenna unit. And the second array antenna unit, and a parallel feeding unit that feeds power in parallel to the first array antenna unit and the second array antenna unit.

  In the array antenna according to the present invention, the first array antenna unit has the first tilt angle directivity characteristic, and the second array antenna unit has the second tilt angle directivity characteristic. The position of the null point and the side lobe shape in the array antenna unit are different from the position of the null point and the side lobe shape in the second array antenna unit. Then, since the first array antenna unit and the second array antenna unit are fed in parallel and the radiation pattern is synthesized, the null point between the first array antenna unit and the second array antenna unit is By being compensated by the mutual directivity, an array antenna can be obtained in which a null point of 0 level is not generated as much as possible.

It is a figure which shows the structure of the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a perspective view which shows the structure of the unit element of the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is sectional drawing which shows the detailed structure of the 1st step element of the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is sectional drawing which shows the detailed structure of the 2nd step element of the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is sectional drawing which shows the length between the sleeve electric power feeding parts of the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the radiation directivity characteristic of the vertical surface of the 3 step | paragraph collinear antenna in the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the other radiation directivity characteristic of the vertical surface of the 3 step | paragraph collinear antenna in the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the other radiation | emission directivity characteristic of the vertical surface of the 3 step | paragraph collinear antenna in the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the radiation directivity characteristic of the vertical surface in the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the other radiation directivity characteristic of the vertical surface in the 6 step | paragraph collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the measurement data of the radiation directivity characteristic of the vertical surface in the 6-stage collinear antenna made into the Example of the array antenna of this invention. It is a figure which shows the structure of the 6 step | paragraph collinear antenna which is the conventional array antenna. It is a figure which shows the structure of the 5-stage array antenna which is the conventional array antenna. It is a figure which shows the directional characteristic in the vertical surface of the 6 step | paragraph collinear antenna which is a conventional array antenna. It is a figure which shows the other directional characteristic in the vertical plane of the 6 step | paragraph collinear antenna which is the conventional array antenna. It is a figure which shows the measured data of the directivity in the vertical plane of the 6-stage collinear antenna which is the conventional array antenna.

FIG. 1 shows the configuration of a six-stage collinear antenna 1 that is an embodiment of the array antenna of the present invention. In FIG. 1, the structure of the 1st stage element 11 thru | or the 3rd stage element 13, and the 4th stage element 21 thru | or the 6th stage element 23 is shown with sectional drawing.
A collinear antenna 1 which is an embodiment of the array antenna of the present invention shown in FIG. 1 includes a series-feed type three-stage collinear antenna section 10 arranged in the upper stage, and a lower stage substantially coaxial with the three-stage collinear antenna section 10. And a three-stage collinear antenna unit 20 of a series feeding type. The three-stage collinear antenna unit 10 disposed in the upper stage is configured by stacking a first-stage element 11, a second-stage element 12, and a third-stage element 13 that constitute a dipole antenna. That is, the second stage element 12 is stacked on the third stage element 13, and the uppermost first stage element 11 is stacked on the second stage element 12. The first-stage element 11 to the third-stage element 13 are supplied with power from a coaxial cable 14 serving as a transmission line to sleeve power supply portions 11e to 13e provided at substantially the center thereof. A connector 15 is provided. The connector 15 is connected to the other end of a feeder line 31 made of a coaxial cable, one end of which is connected to the first terminal of the distributor 30.

  The three-stage collinear antenna unit 20 disposed in the lower stage is configured by stacking a fourth-stage element 21, a fifth-stage element 22, and a sixth-stage element 23 that constitute a dipole antenna. That is, the fifth stage element 22 is stacked on the sixth stage element 21, and the fourth stage element 21 is stacked on the fifth stage element 22. The fourth-stage element 21 to the sixth-stage element 23 are supplied with power from a coaxial cable 24 serving as a transmission line to sleeve power supply portions 21 e to 23 e provided at substantially the center thereof. Is provided with a connector 25. The connector 25 is connected to the other end of a feeder line 32 made of a coaxial cable, one end of which is connected to the second terminal of the distributor 30. The distributor 30 distributes the high-frequency signal power input through the connector 30a into two, and supplies power in parallel to the three-stage collinear antenna unit 10 and the three-stage collinear antenna unit 20 through the feeder line 31 and the feeder line 32. ing. Thus, the distributor 30 is a parallel feeding unit to the three-stage collinear antenna unit 10 and the three-stage collinear antenna unit 20, and the six-stage collinear antenna 1 according to the embodiment of the present invention is a series-feed type three-stage collinear antenna unit. 10 and a three-stage collinear antenna unit 20 of series feed type are configured to feed power in parallel from a distributor 30. Note that if the lengths of the feeder line 31 and the feeder line 32 are made different, the phases of the high-frequency signals fed to the three-stage collinear antenna unit 10 and the three-stage collinear antenna part 20 can be made different.

Next, FIG. 2 is a perspective view showing the configuration of the unit element 2 constituting the elements of each stage of the three-stage collinear antenna section 10 and the three-stage collinear antenna section 20.
As shown in FIG. 2, the unit element 2 is arranged such that a lower end surface of a cylindrical upper sleeve 2a made of metal and an upper end surface of a cylindrical lower sleeve 2b face each other to form a dipole antenna. ing. The first stage element 11 to the third stage element 13 and the fourth stage element 21 to the sixth stage element 23 of the three-stage collinear antenna unit 10 and the three-stage collinear antenna unit 20 shown in FIG. It is comprised by. That is, as shown in FIG. 1, the first stage element 11 of the three-stage collinear antenna unit 10 is configured by an upper sleeve 11a and a lower sleeve 11b facing each other, and the second stage element 12 includes an upper sleeve 12a and a lower sleeve 12b. The third stage element 13 is configured by facing an upper sleeve 13a and a lower sleeve 13b. Further, the fourth stage element 21 of the three-stage collinear antenna unit 20 is configured by the upper stage sleeve 21a and the lower stage sleeve 21b facing each other, and the fifth stage element 22 is configured by the upper stage sleeve 22a and the lower stage sleeve 22b facing each other. The sixth stage element 23 is configured by an upper sleeve 23a and a lower sleeve 23b facing each other.

The first stage element 11 of the three-stage collinear antenna section 10 and the fourth stage element 21 of the three-stage collinear antenna section 20 in the collinear antenna 1 according to the embodiment of the present invention shown in FIG. 3 shows a detailed configuration of the first stage element 11 in a cross-sectional view.
The first stage element 11 shown in FIG. 3 is arranged such that the lower end surface of a cylindrical upper sleeve 11a made of metal and the upper end surface of a cylindrical lower sleeve 11b made of metal face each other. An antenna is configured. When the wavelength of the high frequency signal fed to the dipole antenna is λ, the electrical length of the upper sleeve 11a and the lower sleeve 11b is about λ / 4. A metal upper joint 11c is fitted inside the lower end of the upper sleeve 11a, and a metal lower joint 11d is fitted inside the upper end of the lower sleeve 11b. A coaxial cable 14 led out from the adjacent second lower stage element 12 is inserted into the lower sleeve 11b, and the coaxial cable 14 is inserted into an insertion hole formed at substantially the center of the lower joint 11d. Thus, the outer conductor 14c of the coaxial cable 14 is electrically connected to the lower joint 11d.

Further, the outer conductor 14c of the coaxial cable 14 is removed at the boundary portion between the lower sleeve 11b and the upper sleeve 11a, and the insulator 14b that insulates and holds the center conductor 14a from the outer conductor 14c is exposed. The insulator 14b is removed at a portion beyond the boundary portion to expose the central conductor 14a, and the central conductor 14a is inserted into an insertion hole formed at a substantially central portion of the upper joint 11c. In the insertion hole, the upper joint 11c is electrically connected. The upper joint 11c and the lower joint 11d that are arranged to face each other with the sleeve interval Fg constitute a sleeve feeding portion 11e that serves as an excitation slot. The sleeve feeding portion 11e excites the upper sleeve 11a and the lower sleeve 11b constituting the dipole antenna by the high frequency signal transmitted through the coaxial cable 14.
Similarly, the upper sleeve 21 a and the lower sleeve 21 b constituting the dipole antenna of the fourth stage element 21 are excited by the high frequency signal transmitted through the coaxial cable 24.

Next, the second stage element 12 and the third stage element 13 of the three-stage collinear antenna unit 10 and the fifth stage element 22 and the sixth stage of the three-stage collinear antenna unit 20 in the collinear antenna 1 according to the present invention shown in FIG. The element 23 has the same configuration, and the detailed configuration of the second stage element 12 is shown in FIG.
The second stage element 12 shown in FIG. 4 is arranged such that the lower end surface of a cylindrical upper sleeve 12a made of metal and the upper end surface of a cylindrical lower sleeve 12b made of metal face each other. An antenna is configured. When the wavelength of the high-frequency signal fed to the dipole antenna is λ, the electrical length of the upper sleeve 12a and the lower sleeve 12b is about λ / 4. A metal upper joint 12c is fitted inside the lower end of the upper sleeve 12a, and a metal lower joint 12d is fitted inside the upper end of the lower sleeve 12b. A coaxial cable 14 is inserted into the lower sleeve 12b from below, the coaxial cable 14 is inserted into an insertion hole formed at a substantially central portion of the lower joint 12d, and an outer conductor 14c thereof is connected to the lower joint 12d. Is electrically connected. The coaxial cable 14 led out from the lower sleeve 12b is inserted into the upper sleeve 12a, the coaxial cable 14 is inserted into an insertion hole formed in the substantially central portion of the upper joint 12c, and the outer conductor 14c is connected to the upper sleeve 12b. It is electrically connected to the joint 12c.

Further, the outer conductor 14c of the coaxial cable 14 is removed at the boundary between the lower sleeve 12b and the upper sleeve 12a, and the insulator 14b is exposed. A sleeve feeding portion 12e serving as an excitation slot is configured by the central conductor 14a located inside the insulator 14b, and the upper joint 12c and the lower joint 12d arranged to face each other. The sleeve feeding portion 12e excites the upper sleeve 12a and the lower sleeve 12b constituting the dipole antenna by a high frequency signal transmitted through the coaxial cable 14.
Similarly, the upper sleeve 13a and the lower sleeve 13b constituting the dipole antenna of the third stage element 13 are excited by the high frequency signal transmitted through the coaxial cable 14 in the sleeve feeding portion 13e. Further, the upper sleeves 22a and 23a and the lower sleeves 22b and 23b constituting the dipole antenna of the fifth stage element 22 and the sixth stage element 23 transmit the coaxial cable 24 in the sleeve feeding portions 22e and 23e in the same manner. Excited by the high frequency signal.

ただし、（１）式においてf(θ)は隣接するエレメントとの間隔ｄと給電電流Ｉｎにより決定される配列係数であり、下記の（２）式で表される。

式（２）において、ｋは波数（２π／λ）であり、δはアレーアンテナのアンテナビーム方向に関わる位相項である。 By the way, as shown in FIG. 5, in the three-stage collinear antenna unit 10, the distance between the sleeve power feeding part 12e of the second stage element 12 and the sleeve power feeding part 13e of the adjacent third stage element 13 is d. The distance between the eleven sleeve feeding portions 11e and the sleeve feeding portion 12e of the adjacent second stage element 12 is also d. This distance d corresponds to the physical length of the coaxial cable 14 between adjacent sleeve feeding portions. In the case where the radiation beam is not tilted in the three-stage collinear antenna section 10, the first-stage element 11 to the third-stage element 13, which are fed from the coaxial cable 14, are excited in the same phase by high-frequency signals in the respective sleeve feeding sections. .
Here, in an array antenna such as the three-stage collinear antenna unit 10 in which the elements of each stage are arranged in a straight line, the directivity characteristic corresponding to the number of stages is formed by the amplitude and phase excited by the elements of each stage. . When elements with the same structure and performance are arranged in a straight line at equal intervals in N stages, and the complex current taking into account the phase of the current supplied to each stage element is In, the directivity characteristics of each stage element is Do (θ ), The directivity of the array antenna is expressed by the following equation (1).

In the equation (1), f (θ) is an arrangement coefficient determined by the distance d between adjacent elements and the feeding current In, and is represented by the following equation (2).

In Equation (2), k is the wave number (2π / λ), and δ is a phase term related to the antenna beam direction of the array antenna.

Here, E (electric field) is defined as a vertical plane when excited in the same phase by a high-frequency signal having a wavelength λ in each of the sleeve feeding portions in the first-stage element 11 to the third-stage element 13 in the three-stage collinear antenna section 10. The surface directivity is shown in FIG. The directivity shown in FIG. 6 is the directivity calculated by the above (1) and (2).
Referring to FIG. 6, a sharp main lobe is obtained in a direction of about ± 90 °, and the first null point, the first side lobe, the second null point, and the second side are symmetrically about the main lobe as a base axis. The radiation pattern has lobes and third null points.
Also in the three-stage collinear antenna section 20, when the respective sleeve feeding sections in the fourth-stage element 21 to the sixth-stage element 23 are excited in the same phase by a high-frequency signal of wavelength λ, the E (electric field) plane shown in FIG. The directivity characteristics can be obtained.

  In addition, when the radiation beam of the three-stage collinear antenna unit 10 is tilted downward, excitation is performed by giving a phase difference to the excitation phase of the adjacent stage element. That is, by changing the distance d (physical length of the coaxial cable 14) between the adjacent sleeve feeding parts, a phase difference is generated in the excitation phase of the first stage element 11 to the third stage element 13. Let In this case, when the wavelength of the high-frequency signal to be fed is λ, the length of the interval d is changed so that the electrical length between the adjacent sleeve feeding portion and the sleeve feeding portion is slightly shorter than about 1λ. The radiation beam of the three-stage collinear antenna unit 10 can be tilted downward. Further, the radiation beam of the three-stage collinear antenna unit 10 is tilted upward by changing the length of the interval d so that the electrical length between the adjacent sleeve feeding units is slightly longer than about 1λ. be able to. The physical length of the coaxial cable 14 is a length obtained by multiplying the electrical length of the coaxial cable 14 by the wavelength reduction rate.

  Similarly, in the three-stage collinear antenna section 20, the length of the interval d ′ is changed so that the electrical length between the adjacent sleeve feeding section and the sleeve feeding section is slightly shorter than about 1λ. The radiation beam of the antenna unit 20 can be tilted downward. Further, the radiation beam of the three-stage collinear antenna section 20 is tilted upward by changing the length of the interval d ′ so that the electrical length between the adjacent sleeve feeding section and the sleeve feeding section is slightly longer than about 1λ. Can be made.

  Here, the characteristic configuration of the six-stage collinear antenna 1 according to the embodiment of the present invention will be described. Sleeve feeding of the first-stage element 11 to the third-stage element 13 in the three-stage collinear antenna unit 10 arranged in the upper stage is explained. The interval d between the parts is slightly different from the interval d ′ between the sleeve feeding portions of the fourth-stage element 21 to the sixth-stage element 23 in the three-stage collinear antenna part 20 arranged in the lower stage. . Thereby, the phase difference of the excitation phase between the elements in the first stage element 11 to the third stage element 13 in the three-stage collinear antenna unit 10 and the fourth stage element 21 to the sixth stage element 23 in the three-stage collinear antenna part 20 are obtained. The phase difference of the excitation phase between the elements becomes different, and the tilt angles of the main lobes and the side lobe radiation patterns of the three-stage collinear antenna section 10 and the three-stage collinear antenna section 20 become slightly different from each other. . That is, the position and shape of the null in the radiation pattern of the three-stage collinear antenna unit 10 are different from the position and shape of the null in the radiation pattern of the three-stage collinear antenna unit 20. The radiation pattern of the six-stage collinear antenna 1 is a radiation pattern obtained by combining the radiation pattern of the three-stage collinear antenna unit 10 and the radiation pattern of the three-stage collinear antenna unit 20. Thereby, the level of the null point whose level in the radiation pattern of the three-stage collinear antenna unit 10 is close to 0 is compensated by the radiation pattern of the three-stage collinear antenna part 20, and the level in the radiation pattern of the three-stage collinear antenna part 20 is zero. The level of the null point close to is compensated by the radiation pattern of the three-stage collinear antenna unit 10. Therefore, the level of the null points in the radiation pattern of the six-stage collinear antenna 1 is improved, the number of null points can be reduced, and communication can be performed even in the irradiation area corresponding to the null direction. become able to.

ただし、式（３）において、θoはチルト角度である。 Next, a specific example of the characteristic configuration of the above-described six-stage collinear antenna 1 according to the embodiment of the present invention will be described. In this example, the tilt angle of the main lobe of the three-stage collinear antenna unit 20 disposed in the lower stage is designed so that the tilt angle of the main lobe of the three-stage collinear antenna unit 10 disposed in the upper stage is −2 ° (uptilt). It is assumed that the angle is designed to be 5 ° (down tilt), and the radiation patterns of the three-stage collinear antenna unit 10 and the three-stage collinear antenna unit 20 are combined.
A theoretical calculation formula for forming the main lobe at the desired tilt angle in the upper three-stage collinear antenna unit 10 and the lower three-stage collinear antenna is expressed by Expression (3). In this case, the first stage element 11 to the third stage element 13 or the fourth stage element 21 to the sixth stage element 23 are half-wave dipoles.

However, in Formula (3), θo is a tilt angle.

ただし、（４）式および（５）式において、ｍは上段の３段コリニアアンテナ部１０の段数、ｎは下段の３段コリニアアンテナ部２０の段数、Ｉｍは上段の３段コリニアアンテナ部１０の電流励振値、Ｉｎは下段の３段コリニアアンテナ部２０の電流励振値、ｋは波数（２π／λ）、ｄは上段の３段コリニアアンテナ部１０の隣接するエレメントとの間隔、ｄ’は下段の３段コリニアアンテナ部２０の隣接するエレメントとの間隔、δｍは上段の３段コリニアアンテナ部１０のアンテナビーム方向に関わる位相項、δｎは下段の３段コリニアアンテナ部２０のアンテナビーム方向に関わる位相項である。 The directivity D1 (θ) when the tilt angle of the main lobe of the upper three-stage collinear antenna unit 10 is set to −2 ° (uptilt) using the above equation (3) is the following equation (4): The directivity D2 (θ) when the tilt angle of the main lobe of the lower three-stage collinear antenna unit 20 is designed to be 5 ° (downtilt) is expressed by the following equation (5). .

However, in the equations (4) and (5), m is the number of stages of the upper three-stage collinear antenna unit 10, n is the number of stages of the lower three-stage collinear antenna unit 20, and Im is the number of stages of the upper three-stage collinear antenna unit 10. The current excitation value, In is the current excitation value of the lower three-stage collinear antenna unit 20, k is the wave number (2π / λ), d is the distance between adjacent elements of the upper three-stage collinear antenna unit 10, and d 'is the lower stage Δm is a phase term related to the antenna beam direction of the upper three-stage collinear antenna unit 10, and δn is related to the antenna beam direction of the lower three-stage collinear antenna unit 20. It is a phase term.

Here, FIG. 7 shows the directivity characteristics calculated from the above equation (4) in the case where the main lobe tilt angle of the upper three-stage collinear antenna unit 10 is designed to be −2 ° (up-tilt). Referring to FIG. 7, a sharp main lobe is obtained in the direction of ± about 88 °, and a radiation pattern in which several null points and side lobes are generated approximately symmetrically from side to side with the main lobe as a base axis. However, the level of the side lobe generated above the ± 90 ° axis is lower than the side lobe generated below.
Further, FIG. 8 shows directivity characteristics calculated from the above equation (5) when the lower lobe three-stage collinear antenna unit 20 is designed so that the tilt angle of the main lobe is 5 ° (down tilt). Referring to FIG. 8, a sharp main lobe is obtained in a direction of ± about 94 °, and a radiation pattern in which several null points and side lobes are generated symmetrically about the main lobe as a base axis. However, there are four large side lobes on the upper side of the ± 90 ° axis and only two smaller side lobes on the lower side.
As described above, when the tilt angle is varied, the radiation direction of the main lobe is naturally different, but the position and level of the null point and the shape and number of the side lobes are different.

ただし、（６）式においてｄｃは上段の３段コリニアアンテナ部１０と下段の３段コリニアアンテナ部２０との間隔であり、δｃは上段の３段コリニアアンテナ部１０と下段の３段コリニアアンテナ部２０との指向特性合成時のビーム方向に関わる位相項である。上記（６）式で計算された６段コリニアアンテナ１の合成された指向特性を図９に示す。図９を参照すると、ほぼ±約９０°方向により先鋭な主ローブが得られており、この主ローブを基軸として左右ほぼ対称に少ない数のヌル点とサイドローブが生じている放射パターンとなっている。この場合、サイドローブの形状は大きく異なるようになって０°と１８０°方向にはヌル点が生じているが、±約６０°方向および±約１２０°方向のヌル点のレベルが改善されている。このように、３段コリニアアンテナ部１０の放射パターンにおけるヌル点のレベルは、３段コリニアアンテナ部２０の放射パターンにより補償され、３段コリニアアンテナ部２０の放射パターンにおけるヌル点のレベルは、３段コリニアアンテナ部１０の放射パターンにより補償されるようになる。従って、６段コリニアアンテナ１の放射パターンにおけるヌル点のレベルが改善されるようになり、ヌル点の数を減少させることができると共にサイドローブの形状が異なるようになってヌル方向に該当する照射地域においても通信を可能とすることができるようになる。 The radiation pattern of the six-stage collinear antenna 1 according to the embodiment of the present invention is a radiation pattern obtained by combining the radiation pattern of the three-stage collinear antenna unit 10 and the radiation pattern of the three-stage collinear antenna unit 20. The synthesized radiation pattern directivity characteristic D (θ) is expressed by the following equation (6).

In equation (6), dc is the distance between the upper three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20, and δc is the upper three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20. 20 is a phase term related to the beam direction at the time of directional characteristic synthesis with 20. FIG. 9 shows synthesized directivity characteristics of the six-stage collinear antenna 1 calculated by the above equation (6). Referring to FIG. 9, a sharp main lobe is obtained in a direction of approximately ± 90 °, and a radiation pattern in which a small number of null points and side lobes are generated symmetrically with respect to the main lobe as a base axis. Yes. In this case, the shape of the side lobe is greatly different and null points are generated in the directions of 0 ° and 180 °, but the levels of the null points in the directions of ± about 60 ° and ± about 120 ° are improved. Yes. Thus, the level of the null point in the radiation pattern of the three-stage collinear antenna unit 10 is compensated by the radiation pattern of the three-stage collinear antenna unit 20, and the level of the null point in the radiation pattern of the three-stage collinear antenna unit 20 is 3 It is compensated by the radiation pattern of the staged collinear antenna unit 10. Therefore, the level of the null points in the radiation pattern of the six-stage collinear antenna 1 is improved, the number of null points can be reduced, and the side lobe shape is different so that irradiation corresponding to the null direction is performed. Communication can also be made possible in the area.

  The directivity shown in FIG. 9 is when the interval dc between the upper three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20 is about 1λ (or an integer multiple thereof). In other words, the electrical length of the feeder 31 that feeds power from the distributor 30 shown in FIG. 1 to the upper three-stage collinear antenna unit 10 is the same as the length of the feeder 32 that feeds power to the lower three-stage collinear antenna unit 20 ( Alternatively, the difference in electrical length is an integer multiple of λ), and power is supplied in the same phase. In this case, the electrical length of the feeder line 31 and the electrical length of the feeder line 32 are made different to give a phase difference to the excitation phases of the three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20. The directivity characteristics of the six-stage collinear antenna 1 according to the embodiment can be tilted. The design of the tilt angle can be calculated by regarding the three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20 as unit antennas in the above equation (3).

  A phase difference giving a tilt angle of 5 ° is given to the excitation phase of the upper three-stage collinear antenna unit 10 designed for a tilt angle of −2 ° and the lower three-stage collinear antenna unit 20 designed for a tilt angle of 5 °. FIG. 10 shows the directivity characteristics when the radiation patterns of the upper three-stage collinear antenna unit 10 and the lower three-stage collinear antenna unit 20 are combined. This directivity characteristic is calculated by the above equation (6). Referring to FIG. 10, a sharp main lobe is obtained in a direction of ± about 94 °, and side lobes are generated symmetrically with respect to the main lobe as a base axis, and a radiation pattern with almost no null points is obtained. Yes. In this case, the shape of the side lobe is greatly different, and null points are generated only in the directions of 0 ° and 180 °. The number of null points is reduced and the shape of the side lobe is different. Communication can be made possible even in the irradiation area corresponding to the direction.

  Next, the excitation phase between the upper three-stage collinear antenna unit 10 designed for a tilt angle of −2 ° and the lower three-stage collinear antenna unit 20 designed for a tilt angle of 5 ° is such that the tilt angle is 2 °. FIG. 11 shows measured data of the directivity of the six-stage collinear antenna 1 according to the embodiment of the present invention designed with a phase difference. Referring to FIG. 11, a sharp main lobe is obtained in the direction of ± about 92 °, and side lobes are generated symmetrically with respect to the main lobe as a base axis, resulting in a radiation pattern with almost no null points. Yes. In this case, a null point is generated in the 180 ° direction and a null point having an improved level in the ± 60 ° direction is generated, and the radiation of the six-stage collinear antenna 1 according to the embodiment of the present invention is performed. The level of the null points in the pattern can be improved, the number of null points can be reduced, and communication can be performed even in the irradiation area corresponding to the null direction.

In the collinear antenna according to the present invention described above, the collinear antennas are arranged in the upper stage and the lower stage, but three or more collinear antennas may be arranged in a straight line.
In the collinear antenna according to the present invention described above, the sleeve interval Fg, which is the interval between the feeding portions provided in the elements of each stage, is maintained while the upper joint and the lower joint, which are conductors, maintain parallelism. Each joint is configured to be electrically connected to an upper sleeve or a lower sleeve forming an element. The surfaces where the joints face each other are smooth, and the capacity between the joints changes depending on the space between the sleeves Fg and the area of the joints facing each other. That is, the feeding point impedance of each stage element varies depending on the dimension of the sleeve interval Fg. When the feed point impedance of each stage element changes, the excited current amplitude changes, and as a result, the excitation amplitude mode of each stage element can be electrically controlled.
Furthermore, in the collinear antenna according to the embodiment of the present invention, a coaxial cable such as a semi-rigid cable, a semi-flexible cable, or a flexible cable can be used as a coaxial cable used as a transmission line. Furthermore, the array antenna according to the present invention is not limited to the collinear antenna, but may be formed by arranging coaxially the multi-stage array antenna shown in FIG.

1 6-stage collinear antenna, 2 Unit element, 2a Upper sleeve, 2b Lower sleeve, 10 3-stage collinear antenna, 11 First stage element, 11a Upper sleeve, 11b Lower sleeve, 11c Upper joint, 11d Lower joint, 11e Sleeve feed , 12 2nd stage element, 12a Upper stage sleeve, 12b Lower stage sleeve, 12c Upper stage joint, 12d Lower stage joint, 12e Sleeve feeding part, 13 3rd stage element, 13a Upper stage sleeve, 13b Lower stage sleeve, 13e Sleeve feeding part, 14 Coaxial Cable, 14a Center conductor, 14b Insulator, 14c Outer conductor, 15 Connector, 20 3-stage collinear antenna, 21 Fourth-stage element, 21a Upper-stage sleeve, 21b Lower-stage sleeve, 21e Feed section, 22 5th stage element, 22a Upper sleeve, 22b Lower sleeve, 22e Sleeve feed section, 23 6th stage element, 23a Upper sleeve, 23b Lower sleeve, 23e Sleeve feed section, 24 Coaxial cable, 25 Connector, 30 Distributor, 30a connector, 31 feeder, 32 feeder, 100 6-stage collinear antenna, 111 first stage element, 111a upper sleeve, 111b lower sleeve, 111c sleeve feeder, 112 second stage element, 113 third stage element , 114 Fourth stage element, 115 Fifth stage element, 116 Sixth stage element, 120 Coaxial cable, 121 Matching unit, 122 Connector, 200 Five stage array antenna, 210 Printed circuit board, 211 First stage element, 21 2 2nd stage element, 213 3rd stage element, 214 4th stage element, 215 5th stage element, 216 Feed point, 217 Strip line

Claims (2)

A first array antenna unit that is a series feed type that feeds power to a plurality of antenna elements in series and has directivity characteristics of a first tilt angle;
It is a series feed type that feeds power to a plurality of antenna elements in series, has a directivity characteristic of a second tilt angle different from the first tilt angle, and is linearly arranged with the first array antenna unit. A second array antenna section,
A parallel feeding unit that feeds power in parallel to the first array antenna unit and the second array antenna unit;
An array antenna comprising:   The parallel feeding unit is configured to obtain a tilted directional characteristic by providing a phase difference between the excitation phase of the first array antenna unit and the excitation phase of the second array antenna unit. The array antenna according to claim 1, wherein:

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