JPH05275919A - Meander helical antenna for compact portable radio equipment - Google Patents

Abstract

PURPOSE:To provide a compact antenna which requires no separate matching circuit rogether with the high mass productivity and is suitable for a compact portable radio terminal having the maximum size of its casing of <=1/4 working wavelength in an operating state. CONSTITUTION:A 2nd conductor 1 serving as an exciting conductor having a feeding point 5 in a dielectric column 4 and a 1st conductor 2 which is not directly and electrically connected to the conductor 1 and excited by an electromagnetic inductive function are set at each electric length with which both conductors 1 and 2 can resonate within the working frequency range of a radio equipment for which an antenna is applied. Furthermore a 3rd conductor 3 having a casing earth potential is set in the column 4. In such constitution, it is possible to obtain a compact and inexpensive antenna which has a mass producible structure, requires no separate installation of a matching circuit, can secure the satisfactory matching of impedance with a high frequency part of a compact radio equipment having the maximum size of its casing of <=1/4 working wavelength in an extremely wide range, and is suitable for a portable radio equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna applied to a small mobile terminal such as a portable mobile terminal whose maximum housing size is less than 1/4 of a radio wavelength used when the terminal is used.

[0002]

2. Description of the Related Art Conventionally, an antenna such as an inverted F-shaped antenna or a helical antenna has been applied to a small-sized terminal having a small volume such as a portable mobile terminal. However, the impedance matching with the radio frequency part of the radio has been achieved due to the miniaturization. It became difficult and it was necessary to install a matching circuit separately (JP-A-2-22563). In order to solve this problem, as an antenna that realizes impedance matching with the high frequency part of the radio even though it has a small volume, a type that includes another antenna formed by a meander line inside the helical antenna has been proposed. ..

[0003]

In the above prior art, good impedance matching with the high frequency part of the radio is realized, but the antennas having two completely different operating principles of the helical shape and the meander shape are fed in the same way. In order to
There is a problem that a simple procedure for adjusting the characteristics at the time of mass production is not shown, which causes a large cost increase due to the complexity of the adjusting process.

[0004]

Means for Solving the Problems The above problem is that the first conductor having a helical shape is fed as a helical antenna,
Inside it, one meandering conductor that satisfies the resonance condition within the operating frequency of the radio, or a plurality of meandering conductors that do not make direct electrical contact with each other that satisfy the different resonance conditions are formed inside the dielectric, These conductors are excited by electromagnetic coupling without being directly electrically coupled, and a series of conductors, one end of which is included in the meander-shaped conductor without making electrical contact, are electrically connected to the ground potential of the radio, are provided inside the dielectric. Solved by forming the same.

[0005]

Function: The helical conductor formed inside the dielectric is regarded as a normal helical antenna, and impedance matching with the high frequency part of the radio is achieved. If a meandering conductor having an electric length satisfying a resonance condition within the operating frequency band of the radio is coupled to the helical antenna by electromagnetic coupling without electrical contact, sub-resonance will be achieved in the operating frequency band and impedance will be achieved. The matching state has a wide band. When the maximum size of the case of the wireless device is less than 1/4 of the wavelength used,
The impedance of the antenna input section shows a higher value than the impedance of the radio frequency section, making it difficult to achieve sub-resonance in the operating frequency band. In the present invention, a conductor having a potential equivalent to the ground potential of the radio is formed inside the helical antenna, and the excitation potential of the helical conductor is equivalently close to the ground potential. Therefore, the characteristic impedance (Z ₀ ² = L / C) that contributes to the real part of the impedance of the antenna input unit decreases with the increase of the capacitance component (C) due to the proximity of the excitation potential and the ground potential, and as a result, Impedance of the antenna input part is lowered and impedance matching between the radio frequency part and the antenna can be performed very easily.
A large reduction in the electrical characteristic adjustment process during antenna mass production is achieved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a perspective view of an embodiment of a small antenna for a portable wireless device according to the present invention. A second conductor 1 which is an exciting conductor having a feeding point 5 in a dielectric cylinder 4 and a first conductor 2 which is excited by an electromagnetic induction action without being directly electrically coupled thereto are the cylinder. It is formed on a virtual cylindrical surface formed by a closed curved surface that is equidistant from the central axis. A third conductor 3 included in the first conductor and coupled to the ground potential of the radio device at the ground point 6 is formed in the same dielectric cylinder. Length of second conductor 1 in the dielectric (electrical length)
Is set to resonate within the frequency range of the radio to which the antenna is applied, and the first conductor 2 resonates at a frequency different from that of the second conductor within the frequency range of the radio to which the antenna is applied. If both are set to the electrical length, the two are excited by the electromagnetic coupling phenomenon, and double resonance is realized within the operating frequency range. As a result, a very wide and good input impedance matching condition is achieved, and an antenna that radiates output power from a radio device very efficiently is realized without separately installing a matching circuit. The third conductor does not need to be grounded when the maximum housing size during use of the radio is sufficiently large (specifically, when it is larger than ¼ of the wavelength used by the radio), but the same size ¼ wavelength In the case of turning off, the antenna input impedance is lowered by grounding the conductor, and matching with the radio frequency part of the radio can be achieved very easily.

FIG. 2 is a perspective view of another embodiment of the small antenna for portable radio equipment according to the present invention. The difference from FIG. 1 is that the fourth conductor 7 that is not in direct electrical contact with another conductor inside the dielectric cylinder is included in the first conductor, and
The point that exists so as to include the conductor. Since the fourth conductor is excited by electromagnetic coupling like the first conductor, the fourth conductor is different from the first conductor and is set to an electrical length that resonates within the frequency range used by the radio device. As a result, a higher-order double resonance phenomenon is realized compared to the first embodiment, the frequency range that achieves a good input impedance matching condition is further expanded, and the output power from the radio is radiated more efficiently. It

FIG. 3 is a perspective view of still another embodiment of the small antenna for portable radio equipment according to the present invention. 2 is different from FIG. 2 in that the dielectric cylinder 8 having a different dielectric constant is provided inside the dielectric 4 with the virtual cylindrical surface on which the fourth conductor is formed as a boundary.
Is formed. The dielectric constant may be changed not only on the virtual cylindrical surface on which the fourth conductor is formed but also on another virtual cylindrical surface as a boundary. The present embodiment has an advantage that the electrical length of the fourth conductor can be adjusted by the permittivities of a plurality of dielectrics, the degree of freedom in design is increased, and the design is facilitated.

FIG. 4 shows an example of the electrical characteristics of the small antenna for portable radio of the present invention. Specifically, FIG. 4 is a Smith chart showing a matching state with the radio frequency unit of the embodiment of FIG. In this characteristic, VS in the frequency range from a to b
It can be seen that a good matching state of WR <2 is realized, the non-bandwidth of the matching region is 10%, and an antenna having impedance matching in an extremely wide band is realized.

[0010]

According to the present invention, it is possible to mass-produce an antenna satisfying a good matching condition with a radio frequency unit in an extremely wide frequency band without separately installing a matching circuit by an easy adjustment process. Therefore, it is possible to provide a small antenna suitable for a portable wireless device at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of an embodiment of a small antenna for a portable wireless device according to the present invention.

FIG. 2 is a perspective view of another embodiment of a small antenna for a portable wireless device according to the present invention.

FIG. 3 is a perspective view of another embodiment of a small antenna for a portable wireless device according to the present invention.

FIG. 4 is a Smith chart showing an example of electrical characteristics of a small antenna for a portable wireless device according to the present invention, showing a matching state with a high frequency part of a wireless device.

[Explanation of symbols]

 1: Helical conductor (first conductor) 2: Meander conductor (second conductor) 3: Grounded ground potential conductor (third conductor) 4: Dielectric cylinder 5: Feeding point 6: Grounded chassis Potential grounding point 7: Multiple resonance conductor (4th conductor) 8: Dielectric cylinder

Claims (7)

[Claims] 1. Inside a finite columnar dielectric having a central axis,
A first conductor having a meandering shape that covers the periphery of the central axis as a whole while reciprocating in the direction along the center line, and has no electrical contact point with the first conductor and has the center. A second conductor having a helical shape that shares an axis and covers the first conductor; and a first conductor and a second conductor which are arranged in a region included in the first conductor. A straight or meander-shaped third conductor having no electrical contact point, one end of the second conductor serving as a feeding point, and one end of the third conductor wirelessly. A meandering helical antenna for small portable radios that is grounded to the ground potential. 2. A small antenna for a portable wireless device according to claim 1, wherein a plurality of antennas are not in electrical contact with each other inside said dielectric and are not in contact with said first, second and third conductors. A meander-helical antenna for a small portable wireless device, comprising a conductor having a fourth meander shape, and the second and fourth conductors include the third conductor. 3. The small antenna for portable radio device according to claim 2, wherein the electrical length of the second and fourth conductors inside the dielectric is approximately 1 / wavelength of the applied radio device. Two
The meander helical antenna for small portable radios is characterized in that the lengths of the two are not the same. 4. The small antenna for portable wireless device according to any one of claims 1 to 3, wherein the shape of the dielectric is any one of a cylinder, an elliptic cylinder, and a polygonal cylinder. Meander helical antenna for small portable radios. 5. The small antenna for portable radio device according to claim 4, wherein the first, second, third and fourth conductors are present on a virtual cylindrical surface having a cross section of one concentric polygon. Meander-helical antenna for small portable radios. 6. The small antenna for a portable wireless device according to claim 5, wherein the first, second, third and fourth conductors are present on a virtual cylindrical surface having a cross section of the plurality of concentric polygons. A small antenna for mobile radios. 7. A small antenna for a portable wireless device according to claim 5 or 6, wherein said first, second, third,
It is characterized in that the dielectric constants of a plurality of virtual cylinders divided by a virtual cylinder surface having a cross section of the plurality of concentric polygons in which the fourth conductor is present vary in at least one of the virtual cylinder surfaces. Small antenna for portable radios.