JP3280204B2 - Coaxial resonant slot antenna and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna suitable for use in a portable radio terminal, and more particularly to a slot antenna using a coaxial resonator.

[0002]

2. Description of the Related Art In a portable radio terminal (for example, a simple portable telephone system: PHS), an antenna is being built in from the viewpoint of improving portability. Conventionally, antennas that can be built into a terminal include an inverted F-type antenna and a microstrip antenna. However, in order to secure a sufficient band, it is necessary to increase the overall size of the antenna. It has been difficult to incorporate it into a small terminal such as a portable telephone system.

[0003] To solve these problems, TEM
A slot antenna using a coaxial resonator operating in a (Transverse Electromagnetic) state has been proposed (for example, see Japanese Patent Application Laid-Open No. 5-14047). In this antenna, as shown in FIG. 24, an elongated strip-shaped conductor 53 is disposed along the resonance axis direction in the internal space of a flat conductor box 51 which is a rectangular parallelepiped as a whole, and both ends 57 are formed on end walls 54 of the conductor box 51. It is fixed by electrical contact (FIG. 24).
b). Surface of conductor box 51 (radiation surface)
A slot 52 for transmitting and receiving radio waves is formed so as to intersect one end of the strip conductor 53, and a strip conductor 53 is provided on the inner wall of the conductor box 51 located at the other end of the strip conductor 53.
The extension conductor 55 of the center conductor (not shown) of the coaxial line is provided along the longitudinal direction (resonance axis direction). In addition,
The conductor box 51 is maintained at the ground potential by the outer conductor 56 of the coaxial line.

[0004] The conductor box 51 and the strip conductor 53 cooperate with each other to form a coaxial resonance circuit in the form of a TEM. Therefore,
The electromagnetic wave (transmission signal) supplied into the conductor box 51 via the extension conductor 55 travels along the strip conductor 53 and is radiated to the external space via the slot 52. On the other hand, an electromagnetic wave (received signal) that has entered the conductor box 51 from the external space via the slot 52 travels in the opposite direction along the strip conductor 53 and is picked up by the extension conductor 55.

In this slot antenna, since both ends 57 of the strip conductor 53 are electrically connected to the conductor box 51, it is necessary to set the entire length to 全長 of the used wavelength. Only when this is set, twice the length of the conductor box 51 (or the strip conductor 53) is T.
As a result of the resonance wavelength in the EM state, the electric field strength (amplitude) of the electromagnetic wave traveling in the conductor box 51 becomes zero at both ends 57 of the strip conductor 53 and becomes maximum at the center thereof. This means that it is impossible in principle to incorporate a slot antenna into a wireless terminal having a length in the direction of the resonance axis equal to or less than の of the used wavelength. For example,
At the frequency of 1.9 GHz employed in the PHS, the half wavelength is approximately 80 mm, and the length of the wireless terminal cannot be reduced to 80 mm or less. That is, FIG.
In the case where the conventional slot antenna described in (1) is adopted, there is a problem in that the length of the terminal cannot be reduced to １ ／ or less of the used wavelength.

[0006]

SUMMARY OF THE INVENTION The main object of the present invention is to solve the above-mentioned problems of the prior art and to provide a coaxial resonance type slot antenna having a novel structure capable of further miniaturizing a portable radio terminal. It is in. It is another object of the present invention to provide a novel method for manufacturing such a slot antenna and a portable wireless terminal having a novel structure employing such a slot antenna.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to dispose the entire strip conductor in a space inside the flat conductor box and insulate it from the flat conductor box, and the wavelength is approximately 1/4 wavelength from one end of the strip conductor. The problem can be solved effectively by providing a coupling portion between the conductor and the high-frequency signal transmission line at a position. It is necessary to insulate between the strip-shaped conductor and the flat conductor box by an appropriate means, but generally, it is necessary to support the strip-shaped conductor by filling the inner space of the flat conductor box with an insulating material. desirable. As the insulating material to be filled in the internal space of the flat conductor box, a synthetic resin material having an appropriate dielectric constant (for example, a dielectric constant substantially equal to that of the external space) can be used, but good resonance characteristics can be obtained. To further reduce the antenna size, use a dielectric material (for example, ceramics) having a high dielectric constant and good high-frequency characteristics, a synthetic resin material containing a magnetic material in an appropriate ratio, or a good insulating material. It is desirable to use a magnetic material (for example, an oxide magnetic material) having a property (low conductivity). The dimensions of the antenna can be reduced approximately to the square root of the permittivity or the square root of the magnetic permeability.

The slot antenna of the present invention can be easily manufactured by disposing a strip conductor in the internal space of a flat conductor box formed by molding a metal plate into a hollow rectangular parallelepiped. However, in consideration of mass production, as will be specifically illustrated later, an insulating substrate formed in a two-layer structure is used, a first metal film is formed on the surface of an upper insulating substrate, and a lower insulating substrate is formed. Forming a second metal film on the back surface of
A radio wave transmission / reception slot is formed in at least one of the first metal film and the second metal film, a third metal film is formed between the upper insulating substrate and the lower insulating substrate, and the upper insulating substrate and the lower insulating substrate are formed. It is desirable to manufacture the slot antenna of the present invention by forming a plurality of plated through holes through the periphery. In this case, a flat conductor box is formed by the first metal film and the second metal film and the plurality of plated through holes, and a strip-shaped conductor is formed by the third metal film.

[0009]

In the antenna structure of the present invention, a coaxial line is formed in which the conductor box is an outer conductor and the strip conductor is an inner conductor. When a signal is supplied from the coupling portion to the strip conductor, the electromagnetic wave is generated along the longitudinal direction of the strip conductor. And propagate in a TEM form. When the signal is at the used wavelength, the electric field intensity is maximized at the one end of the strip conductor and minimized at the coupling portion.
/ 4 wavelength resonance can be caused. Radio waves are radiated from the slots to the external space by the electromagnetic waves that have formed resonance.

When the antenna is used as a receiving antenna, the electromagnetic wave that is absorbed from the slot and forms resonance in the conductor box and travels toward the coupling part is picked up by the coupling part.

The box space including the strip conductor from the joint on the strip conductor to the other end opposite to the one end can be used as a kind of stub (matching circuit) if necessary. It is. By changing the length from the other end to the coupling portion, the impedance matching of the resonator can be adjusted, and good impedance matching conditions can be realized. Since the adjustment only slightly corrects the impedance, the length is generally very short as compared with １ ／ of the wavelength used. Therefore, the depth of the conductor box can be set to slightly exceed the １ ／ wavelength, and the size of the conventional antenna, which is １ ／ wavelength, can be substantially reduced by half.

Further, when the slots are arranged so as to intersect with the traveling direction of the electromagnetic waves, the electromagnetic waves in the TEM form propagating in the conductor box become radio waves and are strongly radiated from the slots, and radio waves in the external space are strongly absorbed. You. In particular, when the total length of the slot is close to half the used wavelength, the internal electromagnetic wave and the external radio wave are strongly coupled to the slot. And
If the slot is bent in the middle, the entire length (length of straightness) becomes the length that determines the efficiency. Therefore, by adopting such a shape, the width of the box (the other side with respect to the length of the box surface) can be reduced, as will be described in detail later. Actually, the width of the box can be selected from about 1/4 to 1/8 of the used wavelength. In this way, the width of the conductor box is also reduced by half or reduced by one-half from the conventional size of 1/2 wavelength, if necessary.
/ 4 can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a coaxial resonator type slot antenna according to the present invention will be described in more detail with reference to several embodiments shown in the drawings.

<First Embodiment> In FIG. 1, 1 is a flat rectangular parallelepiped conductor box, 2 is a slot formed in the surface of the conductor box 1, and 3 is a belt-like shape installed inside the box 1 parallel to the same surface. A conductor 20 is a support for the band-shaped conductor 3 made of an insulating material filled in the inside of the box 1, and 9 is a small hole formed in the back of the box 1,
Reference numeral 1 denotes a coupling portion with the external high-frequency transmission line on the conductor 3;
Are the ground points of the high-frequency transmission line on the back of the box 1;
A line conductor connected from the outside of the box 1 to the joint 41 through the small hole 9, 30 is a high-frequency circuit that generates a transmission signal and processes a reception signal, 43 is an end wall of the box 1, and 44 and 45 are conductors. 3
Shows the end of.

The positional relationship between the box 1, the slot 2, and the conductor 3 is shown in a sectional view along the line AA (FIG. 1b) and a sectional view along the line BB (FIG. 1c) in FIG. 1a. The inside of the box 1 was filled with an insulating material having substantially the same dielectric constant as the free space and having good insulating properties and high-frequency characteristics. Support 2
As 0, the ends 44 and 45 of the strip-shaped conductor 3 are slightly separated from the end wall 43 so that the conductor is arranged without being in electrical contact with any surface of the box 1. Further, the length between one end 44 of the conductor 3 and the coupling part 41 was set to １ ／ of the used wavelength. Further, the slot 2 is disposed near the end 44 so as to cross the strip-shaped conductor 3. By adopting such a structure, the conductor 3 is used as a central conductor and the conductor box 1 is used as an external conductor.
A coaxial resonator in the EM form can be formed. The resonance frequency is set to 1.9 GHz, and the length (depth) of the box 1 is slightly larger than １ ／ of the used wavelength (approximately 40 mm).
And

The power supply and the power reception of the present antenna are performed at the joint 4 on the conductor 3 to which the line conductor 10 is connected via the high-frequency transmission line.
1 and the grounding point 42 on the back of the box 1. The transmission circuit output impedance and the reception circuit input impedance of the high-frequency circuit 30 connected to the high-frequency transmission line were both set low (50Ω). The ground potential of the circuit 30 is equal to that of the box 1, and the signal of the circuit 30 is supplied to the conductor 3 through the line conductor 10, and the signal from the conductor 3 is transmitted to the circuit 30. The supplied signal turns into an electromagnetic wave having high-frequency energy and travels in the longitudinal direction of the conductor 3 in the TEM mode in the slot direction. In addition, the electromagnetic waves absorbed from the slots also travel in the longitudinal direction in the TEM state in the joining direction.

Since the electromagnetic wave is in the TEM form, there is no lower limit of the cut-off frequency on a plane orthogonal to the strip conductor in the longitudinal direction. Therefore, the height of box 1 (box dimension in the direction perpendicular to the surface of box 1)
Even if is reduced, transmission of high-frequency energy will not be hindered as long as dielectric breakdown does not occur between the conductor 3 and the box 1. The restriction on the height of the conductor box is determined by the dielectric breakdown and the mechanical strength, and in practice, about 1/100 of the used wavelength is possible. In this embodiment, the height is set to about 1/75 of the wavelength.
(Almost 2 mm).

When the high-frequency energy travels as electromagnetic waves in the form of a TEM, and a current is induced on the conductor 3, a current flows in the opposite direction on the surface of the box 1. The current in the opposite direction is concentrated on the portion closest to the conductor 3. Therefore, when the conductor 3 intersects the slot 2 immediately below the slot 2, the high-frequency energy supplied from the coupling portion of the conductor 3 is concentrated in the slot 2, is coupled to the slot 2, and is radiated to the external space. For this reason, the slot 2 is made to intersect the longitudinal direction of the conductor 3 (the direction of the line segment BB in FIG. 1) immediately above the conductor 3 and at a position near the end 44 where the amplitude of the electric field becomes large inside the box 1. Placed. Note that the current induced in the conductor 3 becomes zero at the end 44 because the conductor 3 is open. Therefore, if the portion from the end 44 to the wall surface 43 immediately below the slot 2 is included, the slot 2 is not sufficiently excited, and the high-frequency energy is not efficiently radiated to the external space. Therefore, the slot 2 is arranged so that the conductor 3 intersects the slot 2 immediately below the slot 2 without any gap.

The surface of the conductor box 1 is at the ground potential, and each surface of the box 1 acts as a reflector against the energy concentrated in the slot 2, so that the slot 2 is concentrated in one side perpendicular to the surface. Can emit radio waves. Therefore, when the antenna of this structure is mounted on a portable wireless terminal, it is possible to arrange the radio wave so that the radiation direction is opposite to the body and radiate the radio wave in a direction that does not face the body. Become. As a result, the sensitivity of the wireless terminal during a call can be improved.

In the present antenna, the conductor 3 is supported by the support 20 filled in the box 1. However, depending on the rigidity of the conductor 3, the conductor 3 is partially supported using a plurality of small support blocks. It is possible to do so.

Further, a slot can be provided on the back surface of the box 1. Radio waves can be emitted from both sides using two slots.

<Embodiment 2> An embodiment in which the shape of the slot 2 is changed will be described with reference to FIGS. FIG. 2 shows an example in which the shape of the slot is a U-shaped slot 4. As shown in the figure, of the three elongated slot elements forming the U-shaped slot, the central element having no end is arranged to intersect the strip conductor 3 in the longitudinal direction. High-frequency energy that has propagated through the band-shaped conductor 3 from the coupling portion is coupled to the slot 4 and radiated to the external space. To increase the radiation efficiency, the entire length of the slot 4 was set to の of the used wavelength. By bending the slot, the width of the box 1 can be reduced to １ ／ to ８ wavelength (40 mm to 20 mm in this embodiment), and the size of the antenna can be reduced.

This structure was manufactured by the manufacturing method shown in FIG. Two insulating substrates 15 and 16 were used. The substrate 15 had a conductor film formed only on the surface thereof, and was subjected to pattern processing by etching to form a pattern for forming the surface of the box 1 by opening the slot 4 (upper left of FIG. 3). Substrate 1
Reference numeral 6 denotes a conductor film formed on both surfaces. The surface is subjected to pattern processing by etching to form a pattern to be the conductor 3 (right in the upper part of FIG. 3), and the small holes for the coupling portion are etched on the rear surface. 9 was opened (not shown) to form a pattern to be the back surface of the box 1. The conductor 3 is provided inside the small hole 9.
Then, a plated through hole penetrating through was formed to form a joint (not shown). The back surface of the substrate 15 and the front surface of the substrate 16 were bonded together (middle diagram in FIG. 3). Next, the peripheral wall surface of the bonded two-layer substrate is covered with a conductive film 17, and the film is fixed so as to be in electrical contact with the metal film on the front and back surfaces of the two-layer substrate (FIG. 3). (See below), the wall of Box 1. According to the present manufacturing method, it is possible to use a printed circuit board for the substrates 15 and 16, and it is possible to reduce the manufacturing cost.

FIG. 4 shows an example in which the strip-shaped conductor 3 'is installed at a position shifted from the center of the box 1 (parallel to the upper surface of the box 1). However, the conductor 3 ′ is installed in a range that does not overlap the left and right slots of the U-shape with the end. In this embodiment, box 1
Above the inner conductor 3 ', the slot 4 is formed crossing the longitudinal direction of the conductor 3', so that high-frequency energy is efficiently radiated from the slot 4. The coupling portion is shifted together with the conductor 3 ', and conversely, the position of the coupling portion can be determined first to set the conductor 3'. With this configuration, the degree of freedom in selecting the position of the coupling portion is generated, and when the present antenna is mounted inside the housing, the position of the high-frequency circuit can be freely set to some extent.

FIG. 5 shows an example in which a slot 5 is provided in which the end of the U-shaped slot 4 of FIG. 3 is bent inward along a direction perpendicular to the longitudinal direction of the conductor 3. The effective length of the slot 5 can be further reduced, and thus the box 1
Can be further reduced, and the effect of reducing the size of the antenna can be obtained.

FIG. 6 shows an example in which the end of the slot 5 has a slot 6 which is bent further inward along the longitudinal direction of the strip conductor. According to this embodiment, the width of the box 1 can be further reduced, and the effect of reducing the size of the antenna can be obtained.

FIGS. 7 and 8 show that both ends of the slots 7 and 8 are in a "undulating path" shape, but in FIG. 7 they extend in the direction in which the conductor 3 exists, and in FIG. This is an example in which it extends toward a portion that joins with No. 3. According to this embodiment, the width dimension of the box 1 can be further reduced,
The effect of reducing the size of the antenna can be obtained.

Each of the slots shown in FIGS. 5 to 8 has a central portion (a portion to which a lead is attached in the drawing) as a basic slot, and has longitudinal ends at both ends perpendicular to the longitudinal direction of the basic slot. The structure is such that slots having a direction and slots having a longitudinal direction in the horizontal direction are continuously and alternately added. In such a structure, slots other than the basic slot pass through the midpoint of the central axis in the longitudinal direction of the basic slot so as to be symmetrical with respect to an axis in a direction perpendicular to the longitudinal direction. The shapes were opposed to each other. In addition, the basic slot crossed the band-shaped conductor 3.
In that case, slots other than the basic slots were not overlapped with the conductor 3.

Next, the relationship between the distribution of the electric field induced in the slot having the shape of this embodiment and the radiated electromagnetic energy will be described with reference to the slot 6 in FIG. 6 as an example. FIG.
Shows the distribution of the electric field induced in the slot 6. As shown in the lower diagram of FIG. 9, a sinusoidal electric field is induced along the slot 6, but as shown in the upper diagram of FIG. 9, the ab, gh, cd, and Electromagnetic energy radiated from the electric field generated in the portion of ef cancels each other and does not contribute to the radiation. The directions of the electric field generated in the portions bc and fg of the slot 6 and the direction of the electric field generated in the portion de of the slot 6 cancel each other, but the amplitudes of the electric fields greatly differ as shown in the figure below. Therefore, the electromagnetic energy from the de portion of the slot is A-
It is radiated around the part B.

Therefore, regarding the slots shown in FIGS. 2 to 8, it can be said that the portion mainly emitting the electromagnetic energy is the portion directly above the conductor 3 where there is no cancellation of the electric field. It is desirable to shorten a portion of the folded slot that is perpendicular to the conductor 3 and that cancels out a portion that emits electromagnetic energy.

As an example of the radiation characteristics of the slot antenna according to the present invention, FIG. 10 shows the directional characteristics (directional characteristics in a plane orthogonal to the conductor 3 in the longitudinal direction) of the slot-shaped antenna shown in FIG. The dimensions of the antenna are approximately 1 length
Wavelength, １ ／ wavelength in width, and 1/75 wavelength in height. The direction outside the normal direction of the plane where the slot exists is 1 in FIG.
Coincides with 80 degrees. As is clear from FIG. 10, the difference between the radiation energy of the electromagnetic wave to the surface on the opposite side (0 degrees and 360 degrees) to the surface where the slot exists is 8 dB, and the radiation to the surface where the slot does not exist is suppressed. I have. Therefore, by using this antenna as a built-in antenna of a portable wireless terminal, a terminal having one-side directivity can be realized.

<Embodiment 3> The connecting portion is connected to the end wall 43 on the end 45 side.
The slot antenna provided through will be described. FIG. 11A is a perspective view of the slot antenna, and FIG.
b shows an AA sectional view, and FIG. 11c shows a BB sectional view. In FIG. 11, reference numeral 11 denotes a small hole formed in the end wall 43 of the conductor box 1, and reference numeral 12 denotes a line conductor connected to the coupling portion 41 of the strip-shaped conductor 3 through the small hole 11. Coupling part 4 of strip conductor 3
1 coincides with end 45. One point 4 on the back of box 1
And 2. In addition, the ground point 42 is not limited to the back surface,
The end wall 43 near the surface may be used. In the antenna of this embodiment, the entire length of the conductor 3 is set to １ ／ of the used wavelength.

<Example 4> A slot antenna filled with a dielectric material having a higher dielectric constant than that of Example 1 and having a small high-frequency loss was used. The dielectric serves as a support for supporting the strip-shaped conductor 3 as in the case of the first embodiment. FIG. 12A is a perspective view of the slot antenna, FIG. 12B is a sectional view taken along line AA, and FIG. 12C is a sectional view taken along line BB. In FIG. 12, reference numeral 13 denotes a dielectric filled in the box 1. Either the first embodiment or the third embodiment can be adopted as the coupling portion (the description is omitted). Since the electromagnetic field inside the box 1 is shortened by the square root of the permittivity of the dielectric 13, the resonance frequency is reduced to the value obtained by dividing the square root of the permittivity with the same size. It can be set to a small value divided by the square root of the dielectric constant.

Since the discontinuity of the dielectric constant occurs between the external space and the space inside the box 1 with the surface of the slot 2 as a boundary, the reflection of the high-frequency energy radiated from the slot is caused by the frequency band outside the resonance frequency of the slot. Increase. Therefore, the antenna of this structure has a characteristic that the frequency bandwidth is narrow, and it is desirable to use the antenna in an application where such a restriction is allowed.

It should be noted that, instead of the dielectric material, the filler can be made of a magnetic material having a small electric conductivity such that the decrease of the resonance Q inside the box 1 is slightly reduced. Also in this case, the size of the box is a value obtained by dividing the size without the filler by the square root of the magnetic permeability.

<Embodiment 5> A description will be given of a slot antenna in which a dielectric is filled only between the bottom surface inside the conductor box 1 and the plane formed by the plane of the strip-shaped conductor 3. FIG. 13A is a perspective view of the slot antenna, FIG.
3c shows a BB sectional view. In FIG. 13, 14 is
2 shows a filled dielectric. The conductor 3 was disposed on the upper surface of the dielectric 14.

According to the fourth embodiment, the effect of size reduction can be obtained by the present embodiment.
However, since there is no discontinuity in the dielectric constant between the external space and the space in the box 1, the reflection of the high-frequency energy radiated from the slot 2 does not occur, and the reduction of the frequency bandwidth is suppressed.

The conductor 3 and the space 46 on the upper surface inside the box 1
Can be filled with a material having a dielectric constant lower than that of the dielectric 14. An intermediate characteristic between the case of the structure of FIG. 13 and the structure of the fourth embodiment can be obtained.

Also in the present embodiment, it is possible to use a magnetic material having a small electric conductivity such that the decrease of the resonance Q inside the box 1 is slightly reduced instead of the dielectric material. The same effect as in the case of the dielectric can be obtained.

<Embodiment 6> A slot antenna formed by using a manufacturing method different from that described in Embodiment 2 will be described. 14, 18 shows a two-layer insulating substrate, FIG. 14a shows a top view of an upper-layer substrate of the two-layer insulating substrate 18, and FIG. 14b shows a cross-sectional view along AA. A conductor film serving as a ground substrate is formed on the entire back surface of the lower insulating substrate of the substrate 18. A strip-shaped conductor 3 was formed between the upper insulating substrate and the lower insulating substrate by pattern processing, and a conductor having a slot 2 on the surface of the upper insulating substrate was formed by the same pattern processing.

Next, a plurality of holes penetrating the peripheral edges of the upper insulating substrate and the lower insulating substrate were formed, and the holes were plated with through holes to form plated through holes 19. The plating through hole 19 is for electrically connecting the conductor on the upper surface of the upper insulating substrate and the conductor on the lower surface of the lower insulating substrate. The intervals between the through holes 19 were less than 1/100 of the wavelength used so that the electromagnetic waves could not seep out of the space surrounded by the through holes.

With the above structure, the grounding substrate on the back surface of the substrate 18 is the back surface of the conductor box 1, the conductor on the surface of the substrate is the front surface of the box, and the plurality of plated through holes 19 are the wall surfaces of the box. A structure for performing the operation could be formed.

Although the connecting portion is not shown, a small hole slightly larger than the diameter of the through hole is formed in the grounding board immediately below the connecting portion of the conductor 3 and only reaches the conductor 3 inside the small hole. A plated through hole was formed.

The present manufacturing method has no three-dimensional manufacturing process.
Since a normal two-dimensional printed circuit board manufacturing method can be applied, manufacturing costs can be reduced.

The two-layer insulating substrate 18 can be formed of a flexible material. If the slot antenna thus formed is not bent in the longitudinal direction of the strip-shaped conductor 3 in which the electromagnetic wave travels, but is bent gently in a direction perpendicular to the longitudinal direction, the electromagnetic field inside the slot antenna becomes coaxial with a large diameter. It is similar to a track. Therefore, the TEM state of the electromagnetic field is maintained, and the antenna operation is maintained.

<Embodiment 7> By incorporating a slot antenna in which a slot is formed only on one side into a portable radio terminal, a small and high-performance terminal can be realized.

The radiation characteristic of the radio wave is described by an electric field crossing the slot in the width direction or a magnetic field on the upper surface of the conductor box and orthogonal to the electric field. Since the magnetic field forms a positive mirror image with respect to the conductor surface, the electromagnetic wave has a directivity peak in a direction where the magnetic field exists when viewed from the conductor surface, and hardly emits in a direction where the magnetic field does not exist . Therefore, if this antenna is installed such that the back surface is in contact with the surface of the housing of the wireless terminal, the electromagnetic wave radiated from the slot is hardly radiated to the housing side. The current induced on the housing surface is suppressed.

Since the radio waves radiate strongly in the outward direction perpendicular to the plane of the slot, the radiation direction is the human body,
In particular, by arranging the antenna so that it is opposite to the head , radio waves can be concentrated and emitted in a direction that does not face the body.
And the sensitivity of the terminal during a call is improved.

On the other hand, when the portable terminal is used away from the human body during standby or the like, there are many multipaths in the radio waves, such as in a premises or an urban area, and the radio waves from the base station are transmitted from an unspecified number of directions. In the incoming environment, calls are possible even if the antenna is unidirectional. However, in an environment where the structure that scatters radio waves from the base station is extremely small, if the base station to be communicated is in a direction where no slot exists when viewed from the terminal housing, there is a possibility that a call cannot be made.

The surface facing the user or the surface contacted by ears or the like during a telephone call is used as the front surface, and the antenna of the present invention is arranged on the front, back and, for example, the side surfaces of the housing. If a system is adopted that excites and disconnects from the slot antenna placed on the front side during a call, the terminal maintains high sensitivity characteristics during a call and almost uniform directivity by combining antennas during a standby. Can be kept.

The comparison of the sensitivity between a wireless terminal having a plurality of antennas according to the present invention having a unidirectional directivity and a wireless terminal having an antenna having a uniform directivity, and a wireless terminal having an antenna having a uniform directivity, is shown in FIG. It is important in evaluating the method of a wireless terminal using the. Normally, since the direction in which the base station exists is unknown to the user, such an incommunicable state with the base station is determined by the direction in which the user is facing and the positional relationship of the base station. It is reasonable to think.

Assuming that digital communication is performed on such a premise, power for obtaining the same code error rate as in the case of using an omnidirectional antenna was obtained by calculation. Vertical 1 resembling a housing
A case where two, three and four of them are arranged symmetrically with respect to a point using the directivity in which a magnetic current element for radio wave radiation is arranged at the center of a conductor plate having ４ wavelength and 横 wavelength in the horizontal direction as a reference pattern. Was calculated. FIG. 15 shows the results. The amount of increase in the power, that is, the required gain increase, was taken as the amount of deterioration, and is plotted on the vertical axis in the figure. In addition, FIG. 16 shows the directivity of the antenna thus arranged in the case where the number of antennas is 1, 2, and 3.

As shown in FIG. 15, as the number of antennas increases, the gain required to realize the same sensitivity as that of the omnidirectional antenna is sharply suppressed. In the figure, even when the two directivities are combined, that is, even when the antenna is arranged only on the rear and front surfaces of the housing, the required gain increase is one.
Less than dB. Therefore, using the unidirectional antenna according to the present invention, the antennas are installed on a plurality of surfaces of the housing, or at least on the front and back surfaces of the housing, and all of these antennas are excited during standby, and the housing is closed during a call. By using the method of disconnecting the antenna installed on the front side, the same terminal sensitivity as a terminal equipped with a drawer antenna or an external antenna at the time of withdrawal at the time of standby is realized. It is possible to realize a portable wireless terminal having higher sensitivity.

FIG. 17 shows the configuration of a portable radio terminal incorporating two slot antennas each having a slot formed on only one side of the present invention, and FIG. 18 shows a connection circuit to the antenna. FIG.
7, reference numeral 31 denotes a housing of the portable wireless terminal, 21 denotes a slot antenna disposed on the front surface of the housing 31, and 22 denotes a housing 3
1 shows a slot antenna arranged on the back side of the first embodiment. In FIG. 18, 23, 24, and 25 are connection lines, 26 is a branching device, and 2
7a and 27b are changeover switches, 28 is a call state monitoring circuit, 29a and 29b are control signal lines, and 30 is a high frequency circuit. The front face was defined as the face facing the user or the face against the ear, and the back face was defined as the face facing the opposite direction to the human body.

The antenna 21 is connected to one branch end of a branch circuit 26 via a connection line 23, and the antenna 22
Is connected to a common contact of the changeover switch 27a via a connection line 24, and the other branch end of the branch circuit 26 is connected to one changeover contact of the changeover switch 27a. Further, one end of the connection line 25 is connected to another switching contact of the changeover switch 27a, and the other end of the connection line 25 is connected to one switching contact of the changeover switch 27b. The common contact of the changeover switch 27 b is connected to the common end of the branch circuit 26, and is connected to the high frequency circuit 30.

The call state monitoring circuit 28 controls the switches 27a and 27b via control signal lines 29a and 29b according to the call state and the standby state. In a call state, the branch circuit 26 is separated from the antenna 22 and the high-frequency circuit 30, and only the antenna 22 is connected to the high-frequency circuit 30. In the standby state, the antennas 21 and 22 are connected to the high frequency circuit 30 via the branch circuit 26.

The antenna directivity at the time of standby is shown in FIG. 16 for the number of antennas 2, and the gain deterioration amount for the non-directional antenna is reduced to a small value of approximately 0.6 dB from FIG. It can be seen that the gain degradation caused during standby is suppressed to a low level. In addition, during a call, the emission of radio waves toward the human body, which is an absorber of high-frequency radio waves, is suppressed, so that when installed on a terminal, the antenna gain increases compared to an antenna with uniform directivity, The effect of improving machine sensitivity is obtained.

FIG. 19 shows an example of arrangement of an actual portable radio terminal. The speaker 35 and the microphone 36 were installed on the front surface of the housing 31, and the antenna 21 was arranged on the same surface as the speaker 35 and the microphone 36. The antenna 22 was disposed on the back opposite to the front. With such an arrangement, the front face inevitably faces the user during a call, and the antenna 22 can be directed in a direction opposite to the human body.

Next, FIG. 20 shows an example in which a third antenna 32 is further provided on the upper surface of the housing 31 in addition to the antennas 21 and 22. The antenna 32 was connected to the antenna 22 for use. The connection diagram is shown in FIG. Antenna 32
Is connected to the common contact of the changeover switch 27a together with the antenna 22 via the connection line 33. According to this configuration,
Since three antennas are excited during standby, the combined directivity of these three antennas approaches uniform directivity as compared with the above-described two antennas, so that the amount of deterioration in antenna sensitivity during standby is further reduced. The effect to be obtained is obtained.

FIG. 22 shows an example in which the third antenna is arranged not on the upper surface but on the side surface. In FIG. 22, 37
Is a third antenna so arranged. Compared with the case of two antennas, the uniformity of directivity in a plane perpendicular to the longitudinal direction of the housing 31 is improved, so that the effect of further reducing deterioration of the terminal sensitivity during standby can be obtained. .

Next, FIG. 23 shows an example in which the slot antenna 38 of the flexible substrate described in the sixth embodiment is arranged on the back surface of the housing 31. The antenna 38 is a band-shaped conductor 3
9 is bent in a curved manner with the longitudinal direction as a central axis, and is arranged so as to cover the back surface and the wall surface of the housing 31 of the portable wireless terminal. Since the antenna 38 has no change due to bending in the longitudinal direction of the band-shaped conductor 39 in which the electromagnetic waves propagate therein, and is gently bent in a direction perpendicular to the longitudinal direction, the electromagnetic field inside the antenna 38 has a large diameter coaxial line. Similar to the above, the TEM state of the electromagnetic field is maintained, and there is no change in the antenna operation. In this structure, since a part of the slot 40 reaches the side surface of the housing 31, the electromagnetic wave energy radiated from the slot is smaller than that of a case where an antenna without bending is arranged only on the back surface of the housing 31. The directivity in a plane orthogonal to the longitudinal direction of the 39 approaches uniform directivity. for that reason,
The effect of improving the sensitivity of the wireless terminal during standby can be obtained.

[0062]

According to the present invention, a slot antenna having a flat structure having one-side directivity can be significantly reduced in size as compared with the related art. Therefore, the antenna according to the present invention
It is suitable for use as a built-in antenna of a portable wireless terminal, and it is easy to incorporate a plurality of built-in antennas. When the antenna of the present invention is arranged on a plurality of surfaces of a portable wireless terminal,
By operating all antennas during standby and disconnecting the antenna facing the user during a call, compared to terminals with a built-in omnidirectional antenna, while maintaining the terminal sensitivity to the same level during standby, during a call The effect of improving the terminal sensitivity can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view and a sectional view for explaining a first embodiment of a coaxial resonance type slot antenna according to the present invention.

FIG. 2 is a plan view for explaining a second embodiment of the present invention.

FIG. 3 is an exemplary perspective view for explaining a method of manufacturing the slot antenna shown in FIG. 2;

FIG. 4 is a plan view for explaining a second embodiment of the present invention.

FIG. 5 is a plan view for explaining a second embodiment of the present invention.

FIG. 6 is a plan view for explaining a second embodiment of the present invention.

FIG. 7 is a plan view for explaining a second embodiment of the present invention.

FIG. 8 is a plan view for explaining a second embodiment of the present invention.

9 is a curve diagram for explaining the electric field distribution of the slot antenna shown in FIG.

FIG. 10 is a curve diagram for explaining the radiation characteristics of the slot antenna shown in FIG. 5;

FIG. 11 is a perspective view and a cross-sectional view for explaining a third embodiment of the present invention.

FIG. 12 is a perspective view and a cross-sectional view for explaining a fourth embodiment of the present invention.

FIG. 13 is a perspective view and a sectional view for explaining a fifth embodiment of the present invention.

FIG. 14 is a perspective view and a cross-sectional view for explaining a sixth embodiment of the present invention.

FIG. 15 is a diagram for explaining a degree of deterioration when one to four slot antennas are arranged.

FIG. 16 is a curve diagram showing directivity when one to three slot antennas are arranged.

FIG. 17 is a conceptual diagram for explaining the structure of a seventh embodiment of the present invention.

FIG. 18 is a circuit diagram for explaining antenna connection according to a seventh embodiment of the present invention.

FIG. 19 is a conceptual diagram for explaining the structure of a seventh embodiment of the present invention.

FIG. 20 is a conceptual diagram for explaining the structure of a seventh embodiment of the present invention.

FIG. 21 is a circuit diagram illustrating antenna connection according to a seventh embodiment of the present invention.

FIG. 22 is a conceptual diagram for explaining the structure of a seventh embodiment of the present invention.

FIG. 23 is a conceptual diagram for explaining the structure of a seventh embodiment of the present invention.

FIG. 24 is a perspective view and a sectional view for explaining a conventional coaxial resonance type slot antenna.

[Explanation of symbols]

 1, 51 conductor box 2-8, 40, 52 slot 3, 3 ', 39, 53 strip conductor 9, 11 small hole 10, 12 wire conductor 13, 14 dielectric 15, 16 substrate 17 ... wall conductor film 18 ... two-layer insulating substrate 19 ... plated through hole 20 ... support member 21,22,32,37,38 ... slot antenna 23-23,33 ... connection line 26 ... branch circuit 27 ... selection switch 28 ... communication State monitoring circuit 29 ... Control signal line 30 ... High frequency circuit 31 ... Housing

Claims (6)

(57) [Claims] 1. A conductor box shape of a rectangular parallelepiped, and the strip conductor having a longitudinal direction in resonance direction of the inner space of the conductor box, radio transmission and reception slots formed on one surface of the electrically <br/> body box And
The slot for transmitting and receiving radio waves is perpendicular to the resonance axis direction.
The slot portion A whose crossing direction is the longitudinal direction and the resonance
A slot portion B whose longitudinal direction is the axial direction;
The direction perpendicular to the direction is the longitudinal direction, and the slot
Connect the ends of the slot portion C shorter than A in the order of CBABC.
The slot portion A is connected to the band
A coaxial resonance type slot antenna, wherein the coaxial resonance type slot antenna is disposed so as to intersect with the conductor, and the whole of the strip conductor is insulated from the conductor box. 2. The longitudinal length of the slot C is shorter than 1/2 of the longitudinal length of the slot A.
The slot antenna according to claim 1, wherein the slot portions (B) and (C) are arranged so as not to overlap with the strip-shaped conductor. 3. A conductor box having a rectangular parallelepiped shape, a strip conductor having a longitudinal direction in a resonance axis direction of an inner space of the conductor box, and a radio wave transmitting / receiving slot formed on one surface of the conductor box. The slot for radio wave transmission / reception has a slot A having a longitudinal direction perpendicular to the resonance axis direction, a slot B having a longitudinal direction perpendicular to the resonance axis direction, and a longitudinal direction perpendicular to the resonance axis direction. And a slot portion C shorter than the slot portion A and an end portion of a slot portion D having a direction perpendicular to the resonance axis direction as a longitudinal direction and shorter than the length of the slot portion B are successively arranged in the order of DCBABCD. Wherein the slot portion A is disposed so as to intersect with the band-shaped conductor, and the entire band-shaped conductor is disposed insulated from the conductor box. Container. 4. The longitudinal length of said slot C is less than half the longitudinal length of said slot A,
The slot antenna according to claim 3, wherein the slot portions (B), (C) and (D) are arranged so as not to overlap with the strip-shaped conductor. 5. The coaxial cable according to claim 1, wherein the total length from one end of the radio wave transmission / reception slot to the other is about の of a used wavelength. Resonant slot antenna. 6. A coaxial resonance type slot antenna according to claim 1, wherein the inside of said conductor box is filled with a dielectric.