JP2010010990A - Shared dual-band omnidirectional antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shared dual-band shared omnidirectional antenna which has shared dual-band omnidirectionality and which reduces its installation space. <P>SOLUTION: A shared dual-band antenna element 6a is constituted of a dipole antenna 4a and the dipole antenna 4a is fed with signals at frequencies F1 and F2 from a feed line, and resonates at the frequency F1, and a parasitic element 5a, which is arranged near and parallel with the dipole antenna 4a, and resonates at the frequency F2. A plurality of shared dual-band antenna elements 6a and 6b are arranged vertically, and furthermore the shared dual-band antenna elements 6a and 6b are arranged with point symmetry. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a dual-frequency omnidirectional antenna that is omnidirectional for two frequencies and can be installed in a small space.

  In mobile radio communications such as mobile phones and PHS (Personal Handyphone System), an omnidirectional antenna is used as a base station antenna in order to configure a service area concentrically around a base station.

  In general, it is preferable that the antenna can be formed relatively thin because a structure for installing the antenna is simplified.

  As mobile radio communication is widely used, the communication capacity is increased and the communication speed is increased. For this reason, sufficient communication capacity / communication speed cannot be obtained in one frequency band, and the communication capacity / communication speed is secured by assigning the second and third frequency bands to each communication company.

  When one mobile radio communication has a plurality of frequency bands, it is preferable to configure the antennas separately for each frequency band and use the plurality of antennas in different frequency bands. However, it may be difficult to install multiple antennas due to the location of the base station. For this reason, the need for a frequency sharing antenna is increasing.

  The following are known as base station antennas for mobile radio communications.

  A plurality of coaxial dipole antenna elements are arranged in the vertical direction, and external conductors in adjacent coaxial dipole antenna elements are alternately connected to internal conductors in adjacent coaxial dipole antenna elements (Patent Documents 1 and 2) .

  The first and second dipole antenna arrays in which a plurality of dipole antennas are vertically arranged are provided symmetrically with respect to the vertical center line, and the length between the common feed point and the feed points of each dipole antenna is approximately equal in electrical length. Connected by a power supply line (Patent Document 3).

  A pair of first dipole antennas sandwiching a cylindrical reflector and a pair of second dipole antennas sandwiching the reflector without overlapping with the first dipole antenna, and the radiation waves from the first and second dipole antennas Those with different frequencies (Patent Document 4).

  An antenna element is composed of a dipole antenna that is fed with two frequencies and radiates a radio wave in the low frequency band, and a parasitic element that radiates a radio wave in the high frequency band by electromagnetic coupling with the dipole antenna. Of n reflectors on the same circumference on the same horizontal plane (Patent Document 5).

  A unit antenna element is constituted by a first dipole that resonates at the first frequency F1 and a second dipole that is disposed in front of the first dipole and resonates at the second frequency F2 (F2> F1). A plurality of unit antenna elements arranged in a vertical direction in front of a plate (Patent Document 6).

  A plurality of dipole antennas are arranged in the vertical direction, and a common feed point and the feed points of each dipole antenna are connected by a feed line having substantially the same electrical length (Patent Documents 7 and 8).

JP-A-60-216606 Japanese Patent Application Laid-Open No. 6-177641 JP 62-91005 A JP 2002-198731 A JP 2005-117493 A JP 2006-325255 A JP 2003-298347 A JP 2004-266484 A

  Corini antennas composed of coaxial dipole antenna elements disclosed in Patent Documents 1 and 2 are antennas for a single frequency and it is difficult to obtain resonance at a plurality of frequencies in response to the need for a frequency sharing antenna. Even if the Corini antenna can resonate at a plurality of frequencies, the Corini antenna feeds each coaxial dipole antenna element in series, so that the vertical omnidirectional (main beam direction and It is difficult to control the side lobe).

  The antennas of Patent Documents 4, 5, and 6 achieve omnidirectionality by arranging a plurality of antenna elements around a reflector or a structure having the same effect as the reflector. Compared with a conventional omnidirectional antenna such as a Corini antenna, the size of the antenna in the radial direction becomes extremely large.

  The antennas of Patent Documents 7 and 8 are difficult to radiate radio waves having a plurality of frequencies, like the antennas of Patent Documents 1 and 2.

  From the above viewpoint, it is desired to realize a non-directional antenna that is shared by two frequencies and has the same size as a conventional omnidirectional antenna for a single frequency.

  Accordingly, an object of the present invention is to provide a dual-frequency omnidirectional antenna that solves the above-described problems and has dual-frequency shared omnidirectionality and can reduce the installation space.

  In order to achieve the above object, the present invention provides a dielectric substrate and a frequency F2 provided on the surface of the dielectric substrate and fed with a frequency F1 and a signal having a frequency F2 higher than the frequency F1, and resonates at the frequency F1. A dipole antenna, a parasitic element provided on the surface of the dielectric substrate, provided in parallel to the dipole antenna, fed with a signal of the frequency F2 from the dipole antenna, and resonated at the frequency F2, and the dielectric In the dual-frequency omnidirectional antenna having a plurality of dual-frequency antenna elements provided on the back surface of the substrate and having a feed line for feeding the signals of the frequencies F1 and F2 to the dipole antenna. The dipole antenna included in each dual-frequency antenna element is connected to a grounding portion provided on the surface of the dielectric substrate. With the earth, the two-frequency antenna elements are provided side by side in the vertical direction, two of the two-frequency antenna elements, each of the adjacent are those provided in point symmetry.

  The frequency F2 fed to the dipole antenna may be less than twice the frequency F1.

  The frequency F2 fed to the dipole antenna may be less than twice the frequency F1.

  A common feed line for feeding power to each of the plurality of dual-frequency shared antenna elements arranged in the vertical direction is provided on the back surface of the dielectric substrate, A broadband distributor that distributes a signal fed from the common feeder line to a plurality of parts may be provided, and branch feeder lines may be wired from the broadband distributor to each of the plurality of dual-frequency antenna elements.

  A phase delay unit that delays the phase of the signal to be fed may be added to at least one of the plurality of feed lines that feed power to the plurality of dual-frequency antenna elements arranged in the vertical direction.

  The horizontal arrangement interval between the even-numbered parasitic elements and the odd-numbered parasitic elements of the plurality of dual-frequency shared antenna elements arranged in the vertical direction may be less than ¼ wavelength at the frequency F1.

  The present invention exhibits the following excellent effects.

  (1) Dual-frequency sharing and non-directionality.

  (2) The installation space can be reduced.

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

  As shown in FIGS. 1A and 1B, the dual-frequency omnidirectional antenna 1 according to the present invention includes two radiating elements 2a and 3a extending above and below the gap with a gap therebetween. A dipole antenna 4a that is fed with signals of frequencies F1 and F2 (2F1> F2> F1) from the feed line 9a and resonates at the frequency F1, shorter than the entire length of the dipole antenna 4a, and from the length of one radiation element 2a (3a) A two-frequency shared antenna element 6a is constituted by a long parasitic element 5a that is provided close to the dipole antenna 4a in parallel with the dipole antenna 4a and resonates at the frequency F2, and the two-frequency shared antenna elements 6a and 6b are vertically moved. A plurality of antenna elements 6a and 6b are arranged side by side in the direction and arranged so as to have a point-symmetrical positional relationship. The reason why the relationship between the frequencies F1 and F2 is determined as described above will be described later.

  In the dual-frequency omnidirectional antenna 1 of the present invention, a conductor wire (conductor pattern) such as a microstrip line is disposed on the front and back surfaces of a dielectric substrate 7 extending vertically, thereby providing a radiation element, a feed line, a parasitic line, and the like. Elements, a grounding portion, and the like are formed. Here, in order to simplify the description, a reference line C extending vertically through the middle in the width direction of the dielectric substrate 7 is virtually provided. Further, in FIG. 1A showing the surface of the dielectric substrate 7, the left side of the reference line C is the front and the right side is the rear. In FIG. 1B showing the back surface of the dielectric substrate 7, the left side is rear and the right side is front. In the following description, a direction orthogonal to the reference line C is referred to as a horizontal direction, and a direction parallel to the reference line C is referred to as an up-down direction.

  As illustrated, in this embodiment, the dual-frequency omnidirectional antenna 1 has two dual-frequency antenna elements 6a and 6b arranged in the vertical direction.

  The dual-frequency shared antenna element 6a located below will be described. In the dual-frequency shared antenna element 6a located below, a grounding portion 8 is provided, which has a reference line C as a front end and occupies a large area in the top and bottom and front and rear on the surface of the dielectric substrate 7 behind the reference line C. Of the two radiating elements 2a and 3a constituting the dipole antenna 4a of the dual-frequency shared antenna element 6a, the radiating element 2a located below extends forward from the reference line C, which is the front end of the grounding portion 8, by a predetermined length. It consists of a horizontal branch and a vertical branch extending a predetermined length downward from the front end of the horizontal branch, and has a Γ shape. The radiating element 3a located thereabove has a horizontal branch extending a predetermined length forward from the reference line C with a gap of a predetermined width in the vertical direction from the horizontal branch of the lower radiating element 2a, and upward from the front end of the horizontal branch. It consists of a vertical branch extending a predetermined length and has an L-shape.

Here, the antenna characteristics of the dipole antenna 4a are measured, and the lengths of the horizontal branches of the radiating elements 2a and 3a and the gap between the radiating elements 2a and 3a are obtained by appropriately adjusting so as to obtain desired antenna characteristics. It is done. The total length of the vertical branch of the radiating element 2a, the length of the vertical branch of the radiating element 3a, and the gap between the radiating elements 2a and 3a is approximately 1 of the radio wave having the frequency F1 radiated from the dipole antenna 4a. / 2 wavelength (approximately λ _F1 / 2).

  On the back surface of the dielectric substrate 7, a feed line 9a is provided at a horizontal position overlapping the radiation elements 2a and 3a of the dipole antenna 4a. The radiating elements 2a and 3a and the feeder line 9a are electrically connected by electrostatic coupling. The feed line 9a has a horizontal branch that extends forward from a branch feed line 12a, which will be described later, and overlaps with the horizontal branch of the lower radiating element 2a, and extends upward from the rear end of the horizontal branch by a predetermined length. It consists of vertical branches that overlap the vertical part of the radiating element 3a, and has an L shape that is flipped from side to side.

The length of the parasitic element 5a in the vertical direction is the total length of the dipole antenna 4a, that is, the length of the vertical branch of the radiating element 2a, the length of the vertical branch of the radiating element 3a, and the length of the gap between the radiating elements 2a and 3a. It is shorter than the total sum and longer than the length of the vertical branch of one radiating element 2a, 3a, and is approximately ½ wavelength (approximately λ _F2 / 2) of the radio wave of frequency F2 radiated from this parasitic element 5a. In this embodiment, the upper and lower midpoints of the parasitic element 5a are located between the gaps that are the upper and lower midpoints of the entire dipole antenna 4a. The parasitic element 5a is in front of the dipole antenna 4a and is close to the dipole antenna 4a by electromagnetic coupling with the dipole antenna 4a so that at least a signal of the frequency F2 can be fed from the dipole antenna 4a. Provided in parallel.

  When actually manufacturing the dual-frequency omnidirectional antenna 1, the distance between the parasitic element 5a and the dipole antenna 4a is gradually reduced from a wide state, and the optimum distance is determined by simulation. To determine the distance between the parasitic element 5a and the dipole antenna 4a. The proximity is an interval determined in this way.

  On the other hand, in the dual-frequency shared antenna element 6b located on the upper side, the reference line C is set as the rear end in the opposite direction to the lower dual-frequency shared antenna element 6a. And the grounding part 8 which occupies a large area in the front and rear is provided. Of the two radiating elements 2b and 3b constituting the dipole antenna 4b of the dual-frequency shared antenna element 6b, the radiating element 2b located below extends backward from the reference line C, which is the rear end of the grounding portion 8, by a predetermined length. It has a horizontal branch and a vertical branch extending a predetermined length downward from the rear end of the horizontal branch. The radiating element 3b located above the horizontal branch extends from the horizontal branch of the lower radiating element 2b by a predetermined width in the vertical direction and extends backward from the reference line C by a predetermined length and from the rear end of the horizontal branch. It has a vertical branch extending a predetermined length and has an L-shape that is flipped right and left.

Here, the length of the horizontal branches of the radiating elements 2b and 3b and the gap between the radiating elements 2b and 3b are appropriately adjusted so that the desired antenna characteristics can be obtained by measuring the antenna characteristics of the dipole antenna 4b. Desired. The total length of the vertical branches of the radiating element 2b and the radiating element 3b and the gap between the radiating elements 2b and 3b is approximately ½ wavelength of the radio wave having the frequency F1 radiated from the dipole antenna 4b (approximately λ _F1 / 2).

  On the back surface of the dielectric substrate 7, a feed line 9b is provided at a horizontal position overlapping the radiation elements 2b and 3b of the dipole antenna 4b on the front surface. The radiating elements 2b and 3b and the feeder line 9b are electrically connected by electrostatic coupling. The feed line 9b extends from a phase delay unit 13 (described later) to a predetermined length and overlaps with the horizontal branch of the lower radiating element 2b, and the upper radiating element extends a predetermined length upward from the front end of the horizontal branch. It consists of vertical branches that overlap the vertical part of 3b and has an L-shape.

The length of the parasitic element 5b in the vertical direction is the total length of the dipole antenna 4b, that is, the length of the vertical branch of the radiating element 2b, the length of the vertical branch of the radiating element 3b, and the length of the gap between the radiating elements 2b and 3b. It is shorter than the total sum and longer than the length of the vertical branch of one radiating element 2b, 3b, and is approximately ½ wavelength (approximately λ _F2 / 2) of the radio wave of frequency F2 radiated from this parasitic element 5b.

  In this embodiment, the upper and lower midpoints of the parasitic element 5b are located between the gaps that are the upper and lower midpoints of the entire dipole antenna 4b. The parasitic element 5b is located behind the dipole antenna 4b and close to the dipole antenna 4b so that at least a signal having the frequency F2 can be fed from the dipole antenna 4b by electromagnetic coupling with the dipole antenna 4b. Provided in parallel.

  In the present embodiment, the horizontal interval between the parasitic element 5b and the dipole antenna 4b in the upper dual-frequency antenna element 6b is equal to the horizontal interval between the parasitic element 5a and the dipole antenna 4a in the lower dual-frequency antenna element 6a. The same.

  In the present embodiment, the lengths of the parasitic element 5b and the parasitic element 5a are the same, and the entire length of the dipole antenna 4b and the entire length of the dipole antenna 4a are the same.

  As described above, in the dual-frequency omnidirectional antenna 1 according to the present invention, the parasitic element 5b is positioned behind the dipole antenna 4b in the dual-frequency shared antenna element 6b positioned above, while In the shared antenna element 6a, the parasitic element 5a is positioned in front of the dipole antenna 4a. That is, the two (even number) dual-frequency shared antenna elements 6a and 6b arranged in the vertical direction are arranged point-symmetrically.

The vertical arrangement interval D2 of the two dual-frequency antenna elements 6a and 6b arranged in the vertical direction shown in FIGS. 1A and 1B is set to the gap center point of the dipole antenna 4a and the gap center point of the dipole antenna 4b. It is defined by the distance between. The vertical arrangement interval D2 is less than one wavelength (λ _F2 ) at the frequency F2. This is because no grating globe is generated in the vertical directivity of the frequency F2. The gain is reduced when the gray gloves are large. Therefore, by setting the vertical arrangement interval D2 of the two dual-frequency antenna elements 6a and 6b arranged in the vertical direction to be less than one wavelength at the frequency F2, it is possible to prevent the occurrence of a gratin grove in the vertical directivity of the frequency F2. Can do.

  The horizontal width D1 of the dielectric substrate 7 shown in FIGS. 1A and 1B is less than a quarter wavelength at the frequency F1, and the radome in which the dual-frequency omnidirectional antenna 1 is incorporated. The diameter (not shown) was made small. Further, by setting the horizontal width D1 of the dielectric substrate 7 as described above, the horizontal arrangement interval between the two dual-frequency antenna elements 6a and 6b arranged on the dielectric substrate 7 in the vertical direction is arranged. Is less than a quarter wavelength at the frequency F1. Thus, by determining the horizontal arrangement interval of the dual-frequency antenna elements 6a and 6b, the distance from the reference line C to the dual-frequency antenna elements 6a and 6b can be reduced. If the distance from the reference line C to the dual-frequency antenna elements 6a and 6b becomes too large, the radio wave radiated forward from the dual-frequency antenna element 6a and the radio wave radiated forward from the dual-frequency antenna element 6b The phase difference between them increases. Similarly, the phase difference between the radio wave radiated backward from the dual-frequency shared antenna element 6a and the radio wave radiated backward from the dual-frequency shared antenna element 6b increases. When the phase difference between the radiated radio waves increases in this way, there is a problem that the side lobe increases in the vertical directivity at the frequencies F1 and F2.

  Therefore, the side lobe can be prevented from increasing in the vertical directivity by setting the horizontal arrangement interval between the two dual-frequency antenna elements 6a and 6b arranged in the vertical direction to be less than ¼ wavelength at the frequency F1. .

  In order to reduce the phase difference of the radiated radio wave, the length of the horizontal branch of the radiating elements 2a, 2b, 3a, 3b is set to zero, and the vertical branch of the grounding portion 8 and the radiating elements 2a, 2b, 3a, 3b is set. Are positioned on the reference line C, the radiating elements 2a, 2b, 3a, 3b do not function as antennas. Therefore, the lengths of the horizontal branches of the radiating elements 2a, 2b, 3a, 3b are set to be as small as possible in order to make the lengths larger than zero and to suppress the side lobes.

  As shown in FIGS. 1 (a) and 1 (b), the dual-frequency omnidirectional antenna 1 according to the present invention is provided for both of two dual-frequency antenna elements 6a and 6b arranged in the vertical direction. A common power supply line 10 for supplying power is provided. The common feed line 10 is formed of a microstrip line and is wired on the back surface of the dielectric substrate 7. The common feed line 10 extends linearly above a feed point (not shown) below the dielectric substrate 7 and is connected to the broadband two-way divider 11 in the middle region between the upper and lower dual-frequency antenna elements 6a and 6b.

  In the middle region between the two dual-frequency antenna elements, a broadband two-partitioner 11 surrounded by an ellipse in FIG. 1B is provided. The broadband two distributor 11 distributes the signal fed from the common feed line 10 into two. The distribution ratio may be equal distribution or unequal distribution so that the power distribution ratio can be arbitrarily set. Branch feed lines 12a and 12b are wired from the broadband dual distributor 11 to the respective dual-frequency antenna elements 6a and 6b.

  Delay the phase of the signal to be fed to at least one of the two feed lines 9a and 9b that feed the two dual-frequency shared antenna elements 6a and 6b arranged in the vertical direction shown in FIGS. 1 (a) and 1 (b). A phase delay unit 13 may be added. In the present embodiment, the phase delay unit 13 surrounded by an ellipse in FIG. 1B is formed in the branch feed line 12b from the broadband two-way divider 11 to the upper dual-frequency antenna element 6b. Has been. The phase delay unit 13 is a conductor pattern of the branch feed line 12b formed in a zigzag shape. By this shape, the length of the branch feed line 12b is made longer than the linear distance, thereby increasing the length of the feed path. The phase of the radio wave radiated from the frequency sharing antenna element 6b can be delayed.

  The operation of the dual-frequency omnidirectional antenna of the present invention will be described below.

  Signals having frequencies F1 and F2 (2F1> F2> F1) are fed to a feeding point (not shown) below the dielectric substrate 7. The fed signal is transmitted to the broadband bi-distributor 11 through a common feed line 10 made of a microstrip line. In the broadband two distributor 11, unequal distribution is possible, but it is assumed here that equal distribution is performed. The feed signal equally distributed by the broadband dual distributor 11 is fed to each of the two dual-frequency antenna elements 6a and 6b arranged in the vertical direction via the respective branch feed lines 12a and 12b. At this time, since the phase delay unit 13 is formed in the branch feed line 12b leading to the upper dual-frequency antenna element 6b and added to the feed line 9b, the upper dual-frequency antenna element 6b receives a feed signal below. Arrives later than the dual-frequency antenna element 6a.

  In the dual frequency antenna element 6a, a signal is fed from the feed line 9a to the two radiating elements 2a and 3a of the dipole antenna 4a. Of the signals fed to the radiating elements 2a and 3a, the signal having the frequency F1 is excited by the dipole antenna 4a including the two radiating elements 2a and 3a, and the radio wave having the frequency F1 is radiated from the dipole antenna 4a. On the other hand, the signal of frequency F2 is secondarily fed from the radiating elements 2a and 3a to the parasitic element 5a. The signal fed to the parasitic element 5a is excited in the parasitic element 5a, and a radio wave having a frequency F2 is radiated from the parasitic element 5a.

  In the dual-frequency antenna element 6b, after the above-described phase delay, similarly to the dual-frequency antenna element 6a, a radio wave having the frequency F1 is radiated from the dipole antenna 4b and a radio wave having the frequency F2 is radiated from the parasitic element 5b. .

  The horizontal plane directivity of a dipole antenna is theoretically omnidirectional. However, in the dipole antennas 4a and 4b of the dual-frequency omnidirectional antenna 1, the horizontal plane directivity becomes like a wide-angle beam due to the influence of a grounding part and a parasitic element provided on the dielectric substrate.

  Therefore, in the present invention, in order to make the horizontal plane directivity of the dipole antenna non-directional, the two dual-frequency antenna elements 6a and 6b are arranged on the same plane so as to be point-symmetric.

  In particular, in the dual-frequency omnidirectional antenna 1 of the present invention, the horizontal plane directivities at the frequencies F1 and F2 are omnidirectional by the two dual-frequency shared antenna elements 6a and 6b. Therefore, in comparison with a three-dimensional dual-frequency omnidirectional antenna in which four dual-frequency shared antenna elements are arranged at intervals of 90 degrees on the same circumference around a conventional cylindrical reflector, The dual-frequency omnidirectional antenna 1 is excellent in cost reduction by reducing the number of antenna elements and space saving by being formed planarly. Moreover, since the dual-frequency omnidirectional antenna 1 of the present invention has the vertical arrangement interval D2 of less than one wavelength at the frequency F2, no grating lobe is generated in the vertical directivity of the frequency F2.

  FIG. 2 shows the horizontal plane directivity of the dipole antennas 4a and 4b (single unit, combined surface) at the frequency F1 (1.9 GHz). L1 is the horizontal plane directivity of the dipole antenna 4b alone, L2 is the horizontal plane directivity of the dipole antenna 4a alone, and L3 is a composite surface of the horizontal plane directivities of the dipole antennas 4a and 4b.

  L1 becomes horizontal directionality strong in the backward direction. L2 becomes horizontal directionality strong in the forward direction. When the horizontal plane directivity of L1 and the horizontal plane directivity of L2 are combined, it becomes omnidirectional.

  Looking at L3, the horizontal plane directivity at the frequency F1 is almost circular. This shows that omnidirectionality is obtained.

  The horizontal plane directivities of the parasitic elements 5a and 5b (single unit, combined surface) at the frequency F2 (2.5 GHz) also have the same tendency as in FIG.

  In the dual-frequency omnidirectional antenna 1 of the present invention, for example, when dual-frequency sharing of a 1.9 GHz band (frequency F1) and a 2.5 GHz band (frequency F2) is considered, the dual-frequency omnidirectional antenna 1 The radome with the built-in diameter is less than 40 mm. This diameter is approximately the same as the diameter of the radome in which the omnidirectional antenna employed in the conventional PHS base station antenna is built, and securing the installation space does not become a problem.

  In the present invention, a common feed line 10 is provided for feeding power to both of the two dual-frequency antenna elements 6a and 6b arranged in the vertical direction, and is provided in an intermediate region between the two dual-frequency antenna elements 6a and 6b. A wide-band bi-distributor 11 that divides the signal fed from the common power-feed line 10 into two is provided, and branch feed lines 12a and 12b are wired from the wide-band bi-distributor 11 to the respective dual-frequency shared antenna elements 6a and 6b. A phase delay unit 13 that delays the phase of the signal to be fed is added to at least one of the two feeding lines 9a and 9b that feed the two dual-frequency antenna elements 6a and 6b arranged in the direction. By these wideband two distributors 11 and the phase delay unit 13, the power supply conditions (phase, amplitude, etc.) to the dual-frequency shared antenna elements 6a and 6b can be set in detail. Thereby, the horizontal plane directivity of the beam emitted in the forward direction and the beam emitted in the backward direction can be adjusted so that the beam becomes more omnidirectional.

In the present invention, the vertical arrangement interval D2 of the plurality of dual-frequency shared antenna elements 6a and 6b arranged in the vertical direction is less than one wavelength at the frequency F2. As a result, it is possible to avoid a decrease in gain due to the occurrence of a gratin grove on the vertical directivity surface of frequency 2F. Furthermore, since the length of the dipole antenna in the vertical direction is generally ½ of the wavelength of the radiated radio wave, the vertical arrangement interval D2 of the dual-frequency antenna element may be larger than ½ wavelength in the frequency F1. preferable. When the vertical arrangement interval D2 is equal to or less than ½ wavelength at the frequency F1, the grounding portion 8 provided on the surface side of the dielectric substrate 7 does not exist in the middle portion in the vertical direction of the dual-frequency shared antenna elements 6a and 6b. Instead, the dielectric composed of the dielectric substrate 7 is exposed. In this case, since the ground corresponding to the common feed line 10 provided on the back side of the dielectric substrate 7 disappears in the intermediate portion, the common feed line 10 does not become a microstrip line. Therefore, if the wavelength at the frequency F1 is λ _F1 and the wavelength at the frequency F2 is λ _F2 ,
λ _F1 / 2 <D2 <λ _F2
It becomes.

Further, in order to satisfy the relationship of λ _F1 / 2 <λ _F2 as described above, it is necessary to satisfy the relationship of F1 <2F2. The dipole antennas 4a and 4b to which the signals of the frequencies F1 and F2 are fed are secondarily fed with the signal of the frequency F2 to the parasitic elements 5a and 5b, and the signal of the frequency F2 is radiated from the parasitic elements 5a and 5b. In order to achieve this, it is necessary to satisfy the relationship of F1 <F2. From the above, the frequency of the signal fed to the dual-frequency shared antenna elements 6a and 6b needs to satisfy the relationship of F1 <F2 <2F2.

  In the present embodiment, the dipole antennas 4a and 4b of the dual-frequency shared antenna elements 6a and 6b employ a DC open type excitation method, but the dual-frequency shared antenna elements 6a and 6b formed on the surface of the dielectric substrate 7 are used. 6b and the feed line 9a. A DC short-circuit type in which 9b is electrically connected through a through hole may be used.

  The dual-frequency omnidirectional antenna 1 of the present invention is suitable for a base station antenna for mobile radio communication having a plurality of frequency bands because it has omnidirectionality for two frequencies and can have a small installation space. For example, a dual-frequency omnidirectional antenna for a second generation mobile phone (1.5 GHz band) and a third generation mobile phone (2 GHz band), a third generation mobile phone (1.7 GHz band) and a third generation mobile phone Dual frequency omnidirectional antenna for telephone (2 GHz band), dual frequency omnidirectional antenna for PHS (1.9 GHz) and next generation PHS or WiMAX (2.5 GHz band), third generation mobile phone (2 GHz band) and a dual-frequency omnidirectional antenna for the next generation PHS or WiMAX (2.5 GHz band) can be considered.

  The dual-frequency omnidirectional antenna 1 according to the present invention has been described as an example including two dual-frequency shared antenna elements 6a and 6b. However, the present invention is applicable even when three or more dual-frequency shared antenna elements are used. Is applicable. Specifically, when two or more odd two-frequency shared antenna elements are arranged and when four or more even two-frequency shared antenna elements are arranged, the same as in the case of two What is necessary is just to form so that a dual frequency shared antenna element may be located alternately in order on the left side and the right side of the reference line C. That is, the dual-frequency shared antenna elements are provided side by side in the vertical direction, and each two adjacent dual-frequency shared antenna elements may be provided point-symmetrically. In addition, a signal fed from a common feed line is distributed to a plurality of signals by a broadband distributor formed on the back surface of the dielectric substrate, and then the signals are fed to the plurality of dual-frequency antenna elements. . At this time, a phase delay unit may be formed in at least one of the plurality of feed lines.

(A) Elevated view seen from the surface of the dielectric substrate of the dual-frequency omnidirectional antenna showing an embodiment of the present invention, (b) Elevated view seen from the back surface of the dielectric substrate. It is a horizontal plane directivity characteristic view of the dual-frequency omnidirectional antenna of the present invention.

Explanation of symbols

1 Dual-frequency omnidirectional antenna 2a, 3a, 2b, 3b Radiating element 4a, 4b Dipole antenna 5a, 5b Parasitic element 6a, 6b Dual-frequency shared antenna element 7 Dielectric substrate 8 Grounding part 9a, 9b Feed line 10 Common feed Line 11 Broadband double distributor 12a, 12b Branch feed line 13 Phase delay unit

Claims (6)

A dielectric substrate;
A dipole antenna provided on the surface of the dielectric substrate, fed with a frequency F1 and a signal having a frequency F2 higher than the frequency F1, and resonating at the frequency F1,
A parasitic element provided on the surface of the dielectric substrate, provided in parallel to the dipole antenna, fed with a signal of the frequency F2 from the dipole antenna, and resonating at the frequency F2.
A dual-frequency omnidirectional antenna having a plurality of dual-frequency antenna elements provided on the back surface of the dielectric substrate and including a feed line for feeding the signals of the frequencies F1 and F2 to the dipole antenna.
The dipole antenna included in each of the plurality of dual-frequency antenna elements is grounded to a ground portion provided on the surface of the dielectric substrate, and the dual-frequency antenna elements are provided side by side in the vertical direction, Each of the two adjacent dual-frequency antenna elements adjacent to each other is provided point-symmetrically, and the dual-frequency omnidirectional antenna.   2. The vertical arrangement interval of the plurality of dual-frequency antenna elements arranged in the vertical direction is greater than a half wavelength at the frequency F1 and less than one wavelength at the frequency F2. Dual frequency omnidirectional antenna.   The dual-frequency omnidirectional antenna according to claim 1, wherein the frequency F2 fed to the dipole antenna is less than twice the frequency F1.   A common feed line for feeding power to each of the plurality of dual-frequency shared antenna elements arranged in the vertical direction is provided on the back surface of the dielectric substrate, A broadband feeder for distributing a plurality of signals fed from a common feeder line is provided, and branch feeder lines are wired from the broadband distributor to each of the plurality of dual-frequency antenna elements. The dual-frequency omnidirectional antenna according to any one of 1 to 3.   The phase delay unit that delays the phase of the signal to be fed is added to at least one of the plurality of feed lines that feed the plurality of dual-frequency antenna elements arranged in the vertical direction. 4. The dual-frequency omnidirectional antenna according to any one of 4 above.   The horizontal arrangement interval between the even-numbered parasitic elements and the odd-numbered parasitic elements of the plurality of dual-frequency shared antenna elements arranged in the vertical direction is less than a quarter wavelength at the frequency F1. Item 6. The dual-frequency omnidirectional antenna according to any one of Items 1 to 5.

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