JP2008263369A - Chip antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip antenna operating as a helical antenna for establishing both the promotion of miniaturization and the improvement of radiation efficiency. <P>SOLUTION: This chip antenna 1 is provided with: a cylindrical base 2 configured of a dielectric or the like; and a radiation conductor 3 formed by winding the surface of the base 2 with a continuous spiral conductor pattern, wherein one end side of the radiation conductor 3 is formed as a power supply part P and the other end side is formed as an open end Q. The open end Q side of the radiation conductor 3 is configured of a narrow pitch part 3a whose spiral pitch is narrower than that at the power supply P side. That is, the radiation conductor 3 is configured so that the power supply P side is formed of the rough spiral conductor pattern whose gap d1 is wide and the open end Q side is formed of the dense spiral conductor pattern whose gap d2 is narrow. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a chip antenna in which a radiation conductor is provided on the surface of a substrate made of a dielectric material or a magnetic material, and in particular, a continuous helical conductor pattern is wound around the surface of a columnar substrate to form a radiation conductor. To a monopole chip antenna.

  In recent years, chip antennas are frequently used as antenna devices built in cellular phones and the like. This type of chip antenna includes a base made of a dielectric or magnetic substance and a radiation conductor having a predetermined shape provided on the surface of the base, and in particular, a continuous spiral conductor pattern on the surface of the columnar base. A monopole type chip antenna that operates as a helical antenna by winding a wire to form a radiation conductor is widely known. That is, in the monopole chip antenna, the electrical length of the radiating conductor can be set to about 1/4 of the free space wavelength of the tuning radio wave, and the mechanical length of the radiating conductor can be set short by the wavelength shortening effect of the base material. If this radiating conductor is spirally wound around the substrate, the entire antenna can be easily downsized. Further, since the chip antenna can be easily mounted on the circuit board, the mounting cost can be reduced.

In this type of conventional chip antenna, the radiation conductor is patterned on the surface of the base body at a constant spiral pitch, and one end side of the radiation conductor is a feeding portion and the other end side is an open end. The radiating conductor is excited by supplying a predetermined feeding signal from the side of the circuit board on which the chip antenna is mounted to the feeding portion of the radiating conductor. Since the chip antenna is a monopole type, the circuit board is provided with a ground pattern in a region adjacent to the chip antenna (see, for example, Patent Document 1).
Japanese Patent Laying-Open No. 2005-57357 (page 4-6, FIG. 1)

  By the way, in the conventional chip antenna described above, if the helical pitch of the radiating conductor is set to be small in order to promote downsizing, undesired electromagnetic coupling is likely to occur and loss is increased, so that radiation efficiency is deteriorated. was there. In other words, with a conventional chip antenna that operates as a helical antenna, it is difficult to promote downsizing without sacrificing radiation efficiency, and it is also difficult to improve radiation efficiency while maintaining downsizing for the same reason. Met.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide a chip antenna that can operate both as a helical antenna and capable of achieving both a reduction in size and an improvement in radiation efficiency.

  In order to achieve the above object, the present invention comprises a columnar substrate made of a dielectric or magnetic material, and a radiation conductor formed by winding a continuous helical conductor pattern around the surface of the substrate, A chip antenna in which one end side of the radiating conductor is a feeding portion and the other end side is an open end, and the opening end side of the radiating conductor is a spiral conductor pattern wound more densely than the feeding portion side.

  The chip antenna configured in this manner is such that the radiation conductor is spirally wound around the surface of the base body and operates as a helical antenna. The open end side of the radiation conductor has a small current and a large voltage. Since the spiral pitch is narrowed only in the region of (the tip side region where the electric field is strong), it is sufficiently wide in the region on the power feeding part side (base region where the magnetic field is strong) of the radiation conductor where the current is large and the voltage is small. It is possible to secure a helical pitch, avoid loss due to undesired electromagnetic coupling, and increase the electrical length and radiation area because the helical pitch in the open end region is narrow. Therefore, it is easy to promote downsizing of this chip antenna without sacrificing radiation efficiency, and it is also easy to improve radiation efficiency while maintaining downsizing.

  In the above configuration, the radiating conductor has a narrow pitch composed of a spiral conductor pattern in which a region from the substantially intermediate position in the extending direction along the spiral to the open end is wound more densely than the remaining region of the radiating conductor. If it is a part, radiation efficiency can be improved reliably. In this case, it is preferable to keep the spiral pitch constant within the range of the narrow pitch portion.

  Further, in the above configuration, substantially the same effect can be expected when the helical pitch of the radiating conductor is gradually decreased from the vicinity of the power feeding portion toward the vicinity of the open end.

  In the chip antenna of the present invention, the spiral pitch is narrowed only in the region on the open end side of the radiating conductor spirally wound on the surface of the base, so that a sufficiently wide spiral pitch is provided in the region on the power feeding unit side. The loss due to undesired electromagnetic coupling can be ensured and the helical pitch of the open end side region is narrow, so the electrical length and radiation area can be increased. Therefore, this chip antenna can achieve both the promotion of miniaturization and the improvement of radiation efficiency. For example, the chip antenna can promote miniaturization without sacrificing radiation efficiency or improve radiation efficiency while maintaining miniaturization. It becomes easy.

  An embodiment of the invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing a state in which a chip antenna according to a first embodiment of the present invention is mounted on a circuit board, and FIG. It is a characteristic view which shows radiation efficiency with a comparative example.

  A chip antenna 1 shown in FIG. 1 includes a columnar base 2 made of a dielectric material (or a magnetic material), a radiating conductor 3 formed by winding a continuous spiral conductor pattern around the surface of the base 2, and a base 2. An electronic element group (not shown) disposed at one end of the upper surface, a feed line 4, a ground line 5, and the like are included. The chip antenna 1 is mounted on the edge of the circuit board 20 and connected to a power supply circuit (not shown) on the circuit board 20 side.

  The radiation conductor 3 extending in a spiral shape has a power supply portion P on one end side and an open end Q on the other end side, but the helical pitch is not uniform, and reaches the open end Q from a substantially intermediate position in the extending direction along the spiral. The region on the tip side is a narrow pitch portion 3a. That is, about half of the radiation conductor 3 is formed by a sparse spiral conductor pattern having a wide gap d1 on the half of the power supply portion P side, and about half of the open end Q side is formed by a dense spiral conductor pattern having a narrow gap d2. ing. The electrical length of the narrow pitch portion 3a is about 1/8 of the free space wavelength λ of the tuning radio wave, and the spiral pitch is constant (d2 is constant) within the range of the narrow pitch portion 3a. Further, in the remaining region of the radiating conductor 3 excluding the narrow pitch portion 3a, that is, the region having an electrical length of about λ / 8 on the power feeding portion P side, the wider spiral pitch is constant (d1 is constant).

  The feed line 4 is connected to the feed part P of the radiation conductor 3. A feed signal is supplied from the circuit board 20 side to the feed part P via the feed line 4, and the high-frequency signal received by the radiation conductor 3 is It is supplied to a receiving circuit or the like on the circuit board 20 side. The ground line 5 is connected to a ground pattern (not shown) provided on the circuit board 20. The feeder line 4 and the ground line 5 are also connected to the electronic element group disposed on the base 2. In the case of the present embodiment example, since the electronic element group includes a matching circuit and a tuning circuit, the resonance frequency of the radiation conductor 3 can be changed by supplying a bias control signal from the circuit board 20 side.

  The chip antenna 1 configured in this manner is operated as a helical antenna by supplying a predetermined power supply signal to the power supply portion P because the radiation conductor 3 is spirally wound around the surface of the columnar base 2. be able to. In this chip antenna 1, the region on the open end Q side where the current is small and the voltage is large in the radiating conductor 3 is formed as a narrow pitch portion 3 a with a narrow helical pitch. Electric length and radiation area can be increased. In addition, since a sufficient helical pitch is secured in the region of the radiating conductor 3 on the power supply portion P side where the current is large and the voltage is small, undesired electromagnetic coupling occurs in the proximal end region where the magnetic field is strong. It has become difficult. Therefore, the chip antenna 1 has a small loss, easily improves the radiation efficiency, and facilitates the downsizing.

  A curve indicated by a solid line in FIG. 2 represents the radiation efficiency when the radiation conductor 3 of the chip antenna 1 is resonated in a predetermined frequency band (470 to 750 MHz). 2 represents the radiation efficiency when the radiation conductor is resonated in the same frequency band with respect to the chip antenna of the comparative example in which the spiral pitch of the radiation conductor is made uniform over the entire length. . All other conditions of this comparative example are set to be equivalent to the chip antenna 1. As is clear from FIG. 2, the radiation efficiency of the chip antenna 1 in which the region on the open end Q side of the radiating conductor 3 is the narrow pitch portion 3a is a comparative example in which the helical pitch of the radiating conductor is uniform over the entire length. This is certainly better than the conventional structure. Therefore, the chip antenna 1 according to the present embodiment can easily promote downsizing without sacrificing radiation efficiency, and can easily improve the radiation efficiency while maintaining downsizing.

  In the above embodiment, a tuned chip antenna that can change the resonance frequency of the radiating conductor 3 has been described. However, the present invention can also be applied to a chip antenna that has a constant resonance frequency of the radiating conductor 3. Needless to say.

  FIG. 3 is a schematic plan view of a chip antenna according to the second embodiment of the present invention, and the same reference numerals are given to the portions corresponding to those in FIG.

  In the chip antenna 10 shown in FIG. 3, the helical pitch of the radiating conductor 3 is gradually decreased from the vicinity of the power feeding part P toward the open end Q. Also in this case, since the open end Q side of the radiating conductor 3 can be formed into a spiral conductor pattern wound more densely than the power feeding part P side, substantially the same effect as the first embodiment described above is expected. it can.

It is a schematic perspective view which shows the state which mounted the chip antenna which concerns on the example of 1st Embodiment of this invention on the circuit board. It is a characteristic view which shows the radiation efficiency of the chip antenna which concerns on the example of 1st Embodiment with a comparative example. It is a schematic plan view of the chip antenna which concerns on the example of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Chip antenna 2 Base | substrate 3 Radiation conductor 3a Narrow pitch part 4 Feeding line 5 Grounding line 20 Circuit board d1, d2 Gap P Feeding part Q Open end

Claims (4)

A columnar substrate made of a dielectric or magnetic material, and a radiation conductor formed by winding a continuous spiral conductor pattern around the surface of the substrate, one end side of the radiation conductor being a feeding portion and the other end side being an open end Is a chip antenna,
A chip antenna characterized in that the open end side of the radiating conductor is a spiral conductor pattern wound more densely than the feeding portion side.   2. The radiating conductor according to claim 1, wherein the radiating conductor has a region extending from a substantially intermediate position in the extending direction along the spiral to an open end, from a spiral conductor pattern wound more densely than the remaining region of the radiating conductor. A chip antenna having a narrow pitch portion.   3. The chip antenna according to claim 2, wherein the helical pitch is constant within the range of the narrow pitch portion.   2. The chip antenna according to claim 1, wherein the helical pitch of the radiating conductor is gradually decreased from the vicinity of the feeding portion toward the vicinity of the open end.

Images