JP2006180408A - Antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna device operating over a frequency band larger than a conventional case by approximating two or more resonance frequencies. <P>SOLUTION: The antenna device 100, which resonates with an electric wave of a given frequency, includes a limited ground plate 10 extending in a longitudinal direction and having a recessed part 15 at the long side extending in the longitudinal direction; a power supply point 20 provided in the vicinity of one long-side edge of the limited ground plate; and a linear element 30 fed from the power feeding point and having a length of L<SB>A</SB>from 1/4 to 1/2 of wavelength λ of resonance frequency of the antenna device. It is characterized by satisfying L<SB>A</SB>+L<SB>B</SB>+2*L<SB>C</SB>=λ, where L<SB>B</SB>is a long-side length of the limited ground plate and L<SB>C</SB>is the depth of the recessed part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna device.

  Antennas used for portable wireless devices and portable televisions are becoming smaller year by year. In order to reduce the size of the antenna, for example, a method of making the antenna helical or meandered, a method of lowering the antenna relative to the ground plane, and the like have been proposed. In these methods, the antenna, which is a distributed constant element, is made a lumped constant element to reduce the size. However, since the lumped constant has a higher Q value than the distributed constant, these methods have a problem that the operating frequency band of the antenna becomes narrow.

  Non-Patent Document 1 discloses a method of bringing a first resonance frequency and a third resonance frequency close to each other by using a meander type antenna. However, the third resonance frequency has a frequency that is three times the first resonance frequency. Therefore, it is difficult to widen the operating frequency band of the antenna by bringing the first resonance frequency and the third resonance frequency close to one frequency.

Patent document 1 is disclosing the method of improving a radiation characteristic by making a notch in a housing | casing. However, this incision suppresses current leakage to the housing by blocking current, and is not a technique for expanding the operating frequency band of the antenna.
C.-WPHuang et al. "FDTD CHARACTERIZATION ~" 1999 Progress in Electromagnetics Research, PIER 24, 185-199, 1999 Japanese Patent No. 3251680

  Provided is an antenna device that operates over a wider frequency band than before by bringing a plurality of resonance frequencies closer to each other.

An antenna device according to an embodiment of the present invention is an antenna device that resonates with a radio wave of a certain frequency, has a longitudinal direction, and a finite ground plane provided with a recess on a long side extending in the longitudinal direction; a feeding point provided at one end near the long side of the finite ground plane, power is supplied from the feeding point, having a length of 1/4 to 1/2 of L _a of the wavelength λ of the resonance frequency of the antenna device A linear element,
When the length of the long side of the finite ground plane is L _B and the depth of the recess is L _C , Equation 1
L _A + L _B + 2 * L _C = λ (Formula 1)
It is characterized by satisfying.

  The antenna device according to the present invention operates over a wider frequency band than before by bringing a plurality of resonance frequencies close to each other.

  Embodiments according to the present invention will be described below with reference to the drawings. This embodiment does not limit the present invention.

FIG. 1 is a configuration diagram of an antenna device 100 according to the first embodiment of the present invention. The antenna device 100 includes a finite ground plane 10, a feeding point 20, and a linear element 30. The finite ground plane 10 is formed in a rectangular shape and has two long sides extending in the longitudinal direction. A concave portion 15 is provided on one of these long sides. The recess 15 is, for example, a cut or a slot that extends in a direction perpendicular to the long side of the finite ground plane 10. The finite ground plane 10 is designed to satisfy Equation 1, where the length of the linear element 30 is L _B and the length of the long side of the L _A finite ground plane 10 is L _B and the depth of the recess 15 is L _C.

L _A + L _B + 2 * L _C = λ * (3/4) (Formula 1)
Here, λ is the wavelength of the radio wave having the upper frequency f of the operating frequency band of the antenna device 100.

  The feeding point 20 is provided in the vicinity of one end of the long side where the concave portion 15 is provided among the long sides of the finite ground plane 10. The linear element 30 has a length represented by Formula 2.

λ * (1/4) <L _A <λ * (1/2) (Formula 2)
The linear element 30 is an antenna element formed in a meander shape as shown in FIG. One end of the linear element 30 is connected to the feeding point 20 and the other end is open. The linear element 30 may be an antenna element formed in a coil type or a helical type.

  The finite ground plane 10 may be a casing or a conductor plate provided in the casing. The housing is a box made of a conductor covering an internal circuit in order to suppress noise entering from the outside or noise radiating inside. The finite ground plane 10 may be the casing itself. In some cases, a ground plane is disposed on the circuit board in the housing. In this case, the finite ground plane 10 may be this ground plane. Hereinafter, the case and the ground plane are described as being equivalent.

  Next, the operation of the antenna device 100 will be described. The linear element 30 has a length of λ * (1/4) or more and λ * (1/2) or less. The sum of the length of the linear element 30 and the length of the finite ground plane 10 is equal to λ (one wavelength). The reason why the length of the linear element 30 is set as described above is that, when this element has a half-wavelength, it becomes a parallel resonance state in which the current is minimized at the time of resonance, and matching cannot be achieved. . When set as described above, the amplitude of the current is distributed so as not to be 0 at the position of the feeding point 20, and the radio wave resonates with the antenna device 100.

  If the linear element 30 is linear and not formed into a meander type, coil type or helical type, and the finite ground plane 10 does not have the recess 15, the upper limit frequency of the operating frequency is reduced. A radio wave having a half frequency (ie, f / 2) resonates. If the wavelength of the radio wave having the frequency f / 2 is λ ′ (λ ′ = 2 * λ), the sum of the length of the linear element 30 and the length of the finite ground plane 10 is equal to λ ′ / 2 (half wavelength).

  In the antenna device 100 according to the present embodiment, the linear element 30 is formed into a meander type, a coil type, or a helical type, and the finite ground plane 10 has a recess 15. As a result, the antenna device 100 has an electrical shortening effect, so that the resonance frequency increases.

  The increase in the resonance frequency occurs in both the radio wave having the wavelength λ and the radio wave having the wavelength λ ′. However, the higher the radio wave, the smaller the electrical shortening effect. Accordingly, since the frequency of the radio wave having the wavelength λ ′ rises higher than that of the radio wave having the wavelength λ, the resonance frequency of the radio wave having the wavelength λ ′ approaches the resonance frequency of the radio wave having the wavelength λ. Thereby, a plurality of resonance frequencies are continuous, and the frequency band in the resonance state of the antenna device 100 is expanded. However, as will be described below, it is difficult to generate such a broadband effect only with a conventional meander type, coil type or helical type antenna element.

  In general, when the interval between adjacent bent portions M of the linear element 30 is small (the number of bent portions M is large), a plurality of resonance frequencies are close to each other, but on the other hand, the bandwidth at each resonance frequency is narrowed. For this reason, when the space | interval of the bending part M of the linear element 30 is too small, the state from which the matching is not taken between adjacent resonant frequencies generate | occur | produces and it becomes difficult to widen the frequency band in a resonant state. This is because if the antenna has a meander structure or a coil structure, the radiation from the antenna is reduced, and as a result, the resonance frequency band is narrowed.

  On the other hand, in this embodiment, the recess 15 is provided in the finite ground plane 10. Current concentrates in the recess 15, and current flows along the recess 15. As a result, the recess 15 has a property similar to that of a meander element. That is, the recess 15 generates a function of operating a part of the finite ground plane 10 as a meander element. As a result, the recess 15 assists the effect of bringing the wavelength λ and the wavelength λ ′ closer to each other by the linear element 30 described above. As a result, even if the number Nm of the bent portions M of the linear element 30 is reduced, that is, even if the distance Dm between the bent portions M is kept relatively wide, the narrowing of the adjacent resonance frequency is suppressed. The adjacent resonance frequencies can be brought close to each other. At this time, the number Nm of the bent portions M and the distance Dm between the adjacent bent portions M have the relationship of Expression 3.

Dm = λ / (4 * Nm) (Formula 3)
In the first embodiment, the required number of bent portions M of the linear element 30 can be reduced by providing the recess 15 in the finite ground plane 10. As a result, it is possible to bring adjacent resonance frequencies closer without narrowing the resonance frequency band of the antenna device 100.

  Further, as described in Non-Patent Document 1, even if an attempt is made to approach the resonance frequency of λ / 2 (first resonance frequency) and the resonance frequency of λ * (3/2) (third resonance frequency), the frequencies are mutually different. Since it is far away, it was impossible to widen the resonance frequency. Incidentally, in this case, the resonance frequency (second resonance frequency) of λ is parallel resonance, and the impedance becomes very large, so that it cannot be matched with 50Ω which is the impedance of the feeder line.

  In other words, the conventional technique using a meander element or the like has a major drawback in that resonance is generated only by an antenna and attempts to make them close to each other, and is not suitable for widening the band.

  However, in the first embodiment, by introducing a resonance phenomenon using a housing, adjacent resonances of λ / 2 resonance (first resonance) and λ resonance (second resonance) are used. By optimizing the length of the element 30, the length of the long side of the finite ground plane 10, and the depth of the recess 15 as described above, the resonance frequency of λ / 2 and the resonance frequency of λ can be made closer to each other. . As a result, the two resonance frequencies can be easily brought close to each other as compared with the prior art, and the resonance frequency of the antenna device 100 can be widened. In addition, in the above description, the length of the linear element 30, the finite ground plane 10, and the recessed part 15 shows electrical length.

  2 and 3 are configuration diagrams of a linear element that can be used in place of the linear element 30. FIG. FIG. 2 shows a coil-type or helical-type linear element 31. When the linear element 31 is used in place of the linear element 30, the linear element 31 is designed to follow Equation 3 with the number of turns being Nm and the interval between adjacent windings being Dm. In this case, the number of turns Nm of the linear element 31 can be reduced by providing the recess 15 in the finite ground plane 10. As a result, similar to the first embodiment, adjacent resonance frequencies can be brought closer without narrowing the resonance frequency band of the antenna device 100.

  FIG. 3 shows a meander type linear element 32. The linear element 30 in FIG. 1 travels in the longitudinal direction of the finite ground plane 10 while bending, but the linear element 32 in FIG. 3 extends in the short side direction of the finite ground plane 10 while bending. The linear element 32 is designed so that the number of the bent portions M is Nm, and the distance Dm between the adjacent bent portions M is satisfied. Thereby, the effect of the first embodiment can be obtained.

  FIG. 4A and FIG. 4B are graphs showing simulation results of the impedance variation of the antenna device and the reflection coefficient of the antenna device. FIG. 4A and FIG. 4B show the results of comparing the conventional antenna device and the antenna device 100 of the first embodiment. The smaller the reflection coefficient, the better the performance of the antenna device.

  Both the conventional antenna device used in this simulation and the antenna device 100 of the first embodiment are designed with the upper frequency of the operating frequency set to 620 MHz. That is, the length of the meander or coil-structured linear element 30 is 22 cm, the length of the casing is 26 cm, and the length of the entire antenna device is approximately 48 cm.

  The conventional antenna device does not have a recess in the housing. On the other hand, the antenna device 100 according to the present embodiment has a recess of 4 cm in the housing. This length of 4 cm corresponds to the length of 1/12 wavelength of a radio wave having a center frequency of 620 MHz (one wavelength is about 48 cm).

  As shown in FIG. 4B, the threshold value of the reflection level was set to −4 dB. As a result, the operating frequency of the conventional antenna device is a band of 430 MHz to 535 MHz, and the operating frequency of the antenna device 100 according to the present embodiment is a band of 410 MHz to 625 MHz. That is, the antenna device 100 according to the present embodiment can obtain an operation band twice or more that of the conventional antenna device.

  In the conventional antenna apparatus, other resonance occurs at 900 MHz. However, this resonance frequency is too high, and thus does not contribute to widening the operating frequency. On the other hand, in the first embodiment, the broadband is realized by moving the resonance frequency of the radio wave to a lower frequency and fusing adjacent resonance frequencies.

  In the first embodiment, when the depth of the recess 15 is set to a quarter wavelength or more, the current blocking effect due to the incision disclosed in Patent Document 1 occurs, and the electrical length of the casing is increased. Becomes very short and resonates only at a frequency of 1000 MHz. As a result, a result (not shown) that the operating frequency band is narrowed was obtained. Therefore, it is preferable that the depth of the recess 15 is a cut of 1/8 wavelength or less, and at this time, an effect that the operating frequency band is widened is obtained.

  Referring to FIG. 4A, the impedance of the first embodiment has a variation point between two resonance frequencies. This means that the resonance is switched before and after the mutation point.

(Second Embodiment)
FIG. 5 is a configuration diagram of an antenna device 200 according to the second embodiment of the present invention. The antenna device 200 includes a linear element 33 as an antenna element. One end of the linear element 33 is connected to the feeding point 20, and the other end of the linear element 33 is connected to the finite ground plane 10 via the variable capacitance element 40. The variable capacitance element 40 is a capacitance element that can change a capacitance value, such as a diode or a MEMS element.

  The antenna device 200 further includes a control circuit 50 and a radio circuit 60. The control circuit 50 is a circuit that controls the capacitance value of the variable capacitance element 40. The radio circuit 60 is connected to the control circuit 50 and the linear element 33. The control circuit 50 and the radio circuit 60 are mounted on the finite ground plane 10.

  The operating frequency varies depending on the capacitance value of the variable capacitance element 40. The physical length of the linear element 33 is determined when the capacitance value of the variable capacitance element 40 is minimized. At this time, the antenna device 200 operates at the highest frequency f ″ among the operating frequencies. The electrical length of the linear element 33 combined with the variable capacitance element 40 is set to be equal to or more than a quarter and a half of the wavelength λ ″ of the radio wave having the highest frequency f ″. Yes.

  The length obtained by adding the length of the finite ground plane 10 and the electrical length of the variable capacitance element 40 and the linear element 33 is set to be equal to the wavelength λ ″. As a result, the antenna device 200 resonates with the radio wave having the frequency f ″.

  By changing the capacitance value of the variable capacitance element 40, the operating frequency band moves. For example, by changing the capacitance value of the variable capacitance element 40, the graph of this embodiment shown in FIG. 4B is translated to the high band or the low band. The capacitance value of the variable capacitance element 40 is preferably set to be equal to the stray capacitance at the tip of the actual linear element 33. For example, the stray capacitance at the tip of the actual linear element 33 is 0. If it is several pF, 0. Let it be several pF. This is because if the capacitance value of the variable capacitance element 40 is larger than the stray capacitance at the tip of the linear element 33, the operating frequency band of the antenna device 200 is narrowed.

  FIG. 6 is a diagram illustrating an internal configuration of the variable capacitance element 40. The variable capacitance element 40 includes a capacitance 41, a diode 42, an inductance 43, a variable resistor 44, and a DC power supply 45. The capacitance 41 is arranged so that the voltage from the DC power supply 45 applied to the diode 42 does not leak to the feeding point 20. The diode 42 is a varicap diode whose capacitance value changes depending on the voltage applied from the DC power supply 45. The inductance 43 is arranged so that the high-frequency current from the feeding point 20 does not leak to the control circuit. The resistance value of the variable resistor 44 changes in response to a signal from the control circuit 50. By changing the resistance value of the variable resistor 44, the voltage applied from the DC power supply 45 to the diode 42 changes.

  When receiving the capacitance value switching signal from the radio circuit 60, the control circuit 50 changes the resistance value of the variable resistor 44. Thereby, the voltage applied to the diode 42 changes, and the capacitance value of the diode 42 changes. When the capacitance value of the variable capacitance element 40 changes, the characteristics of the antenna device 200 change. For example, the signal strength of the received signal also changes. When the signal strength of the received signal is weak, the radio circuit 60 further outputs a capacitance value switching signal to the control circuit 50. When the signal strength of the received signal is sufficiently strong, the radio circuit 60 does not output a capacitance value switching signal.

  As described above, in the second embodiment, the operating frequency band of the antenna device 200 can be shifted by changing the capacitance value of the variable capacitance element 40.

  7 to 10 are diagrams showing specific examples of the linear element 33. FIG. FIG. 7 shows a linear element 34 formed in a meander shape in the same manner as the linear element 30 shown in FIG. FIG. 8 shows a linear element 35 formed into a coil type or a helical type in the same manner as the linear element 31 shown in FIG. FIG. 9 shows a linear element 36 formed in a meander shape in the same manner as the linear element 32 shown in FIG. Each tip of the linear elements 34 to 36 in FIGS. 7 to 9 is connected to the finite ground plane 10 via the variable capacitance element 40. By forming the linear element 33 into any one of the linear elements 34 to 36, the electrical length of the antenna device 200 can be increased as in the first embodiment.

  The linear element 37 shown in FIG. 10 has one end connected to the feeding point 20 and the other end open. A node N between one end and the other end of the linear element 37 is connected to the finite ground plane 10 via the variable capacitance element 40. When the capacitance value of the variable capacitance element 40 is high, the variable capacitance element 40 is arranged in the middle of the linear element 37 as shown in FIG. The reason for this arrangement will be described later. The linear element 37 is formed in a meander shape from the node N to the open end.

  In general, the capacitance value of a MEMS element or a diode is initially set to 0. Even if it is several pF, it often becomes 1 pF or more after packaging. This is because stray capacitance existing in the IC package is added when the diode or the MEMS element is packaged.

  In order to cope with this, the variable capacitance element 40 is arranged in the middle of the linear element 37. The tip portion of the linear element 37 performs a capacitive operation. As shown in FIGS. 7 to 9, when the variable capacitance element 40 is connected to the tip of the linear element, the capacitive action of the linear element becomes very strong. On the other hand, the root of the linear element (near the feeding point 20) functions as an inductance. When the variable capacitance element 40 is connected to the root of the linear element, the capacitive function of the linear element is weakened. Therefore, when the capacitance value of the variable capacitance element 40 is large, the function of the variable capacitance element 40 can be adjusted by connecting the variable capacitance element 40 in the middle of the linear element 37 as shown in FIG. . Thereby, the capacitance value of the variable capacitance element 40 can be increased.

  The electrical length of the linear elements 34 to 37 and the electrical length of the finite ground plane 10 including the concave portion 15 satisfy Expression 1 and Expression 2. Thereby, 2nd Embodiment can acquire the effect similar to 1st Embodiment.

  Furthermore, in the second embodiment, by changing the capacitance value of the variable capacitance element 40, the frequency of the operating frequency band can be shifted while keeping the operating frequency band wide.

  FIG. 11 is a perspective view showing a specific example of the antenna portion of the second embodiment. The antenna device 200 further includes a feeder line 210, a signal line 220, and a shield 230. Here, the linear element 34 shown in FIG. 7 is adopted as the antenna element. The feed line 210 feeds the high frequency signal from the radio circuit 60 of FIG. The signal line 220 transmits a control signal from the control circuit 50 of FIG. The shield 230 incorporates the control circuit 50 and the radio circuit 60 and shields them from the high frequency signal.

  The linear element 34 may be formed by forming a wire or punching a sheet metal. One terminal of the variable capacitance element 40 is connected to the linear element 34, and the other terminal is connected to the ground of the finite ground plane 10.

  12 and 13 are perspective views showing other specific examples of the antenna portion of the second embodiment. In these specific examples, a linear element 37a and a linear element 37b having the same configuration as the linear element 37 shown in FIG. 10 are employed as antenna elements. The linear elements 37a and 37b are formed by depositing a metal on the finite ground plane 10 and etching it. The linear elements 37a and 37b are connected to the variable capacitance element 40 in the middle of the bent portion formed in a meander shape.

  A ground is provided on the back surface of the finite ground plane 10. However, grounding in the portion where the linear elements 37a and 37b are arranged (broken line frame in the figure) is excluded. Thus, by forming the linear elements 37a and 37b on the finite ground plane 10, the antenna device 200 can be manufactured at a low cost and with a high yield.

  The linear elements 37a and 37b are different from each other in length. Accordingly, the linear elements 37a and 37b differ in the number Nm of bent portions and the distance Dm between the bent portions. Thereby, the operating frequency bands are different from each other.

  If the wiring connecting the variable capacitance element 40 and the linear elements 37a and 37b is long, stray inductance is generated by the wiring. Thereby, the characteristic of the antenna device 200 may change. Therefore, as shown in FIGS. 12 and 13, the variable capacitance element 104 is arranged in a portion where the linear elements 37 a and 37 b are close to the ground region. As a result, characteristic changes due to stray inductance can be suppressed.

  FIG. 14 is a perspective view showing still another specific example of the antenna portion of the second embodiment. The linear element 37c partially includes a plate element. Thereby, the operating frequency band of the antenna device 200 can be expanded. It is understood that this is due to the increase in the degree of freedom in the way the current flows due to the plate shape, resulting in perturbation in the resonance frequency.

  The resonance frequency band can also be expanded by increasing the line width of the linear elements 37a and 37b shown in FIG. However, in this case, the resonance frequency becomes high.

  As shown in FIG. 14, the linear element 37c can widen the resonance frequency band without increasing the resonance frequency by increasing the width of the finite ground plane 10 in the thickness direction.

(Third embodiment)
FIG. 15 is a configuration diagram of an antenna device 300 according to the third embodiment of the present invention. The finite ground plane 10 of the antenna device 300 is provided with a plurality of recesses. The recesses 16 and 17 may be cuts or slots like the recess 15. However, if the respective depths of the recesses 16 and 17 are L ₁₆ and L ₁₇ , it is necessary to satisfy Expression 4.

L _A + L _B + 2 * (L ₁₆ + L ₁₇ ) = λ) (Formula 4)
In the third embodiment, since the plurality of recesses 16 and 17 are provided, the electrical length can be increased even if the physical length of the finite ground plane 10 is short. As a result, the overall size of the antenna device 300 can be reduced.

N recesses (N = 2, 3, 4,...) Are provided, and the depths of these recesses are L _k (k = 1 to N), respectively. In this case, Expression 5 is satisfied.

L _A + L _B + 2 * ΣL _k = λ (Formula 5)
Here, “Σ” means L ₁ + L ₂ + L ₃ +... L _N−1 + L _N. Thus, the size of the antenna device 300 can be further reduced by providing three or more recesses.

  In the third embodiment, instead of the linear element 35, linear elements 34, 36, and 37 may be employed.

(Fourth embodiment)
FIG. 16 is a configuration diagram of an antenna device 400 according to the fourth embodiment of the present invention. The antenna device 400 includes finite ground planes 10a and 10b. The finite ground planes 10 a and 10 b are connected by a conductor 410. The antenna device 400 is assumed to be a foldable terminal.

  When it is difficult to provide a concave portion on the finite ground plane, the hinge portion of the folding portion may be used as the concave portion as in this embodiment. As a result, the same effects as those of the first and second embodiments can be obtained.

  In the third embodiment, instead of the linear element 36, linear elements 34, 35 and 37 may be employed.

  As a result of the inventor's investigation, it has been clarified that the radiation pattern of the antenna device changes when the depth of the concave portion becomes greater than λ * (1/8). This is because the current flow on the finite ground plane 10 is blocked by the recess as described in Patent Document 1. In the above embodiment, since radiation is generated using the entire finite ground plane 10, if the flow of current on the finite ground plane 10 is blocked, the characteristics of the antenna device are degraded. Therefore, in the above embodiment, the depth of the recess is preferably equal to or less than 1/8 of the wavelength λ of the radio wave having the upper limit frequency of the operating frequency band.

  The above embodiment can be applied to a portable wireless device. Moreover, the above embodiment is applicable to a portable television.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a configuration diagram of an antenna device 100 according to a first embodiment of the present invention. The block diagram of the form of the linear element which can be used instead of the linear element 30. FIG. The block diagram of the form of the linear element which can be used instead of the linear element 30. FIG. The graph which shows the simulation result of the impedance fluctuation of an antenna device, and the reflection coefficient of an antenna device. The block diagram of the antenna apparatus 200 according to 2nd Embodiment which concerns on this invention. The figure which shows the internal structure of the variable capacitance element 40. The figure which shows the linear element. The figure which shows the linear element. The figure which shows the linear element. The figure which shows the linear element 37. FIG. The perspective view which shows the specific example of the antenna part of 2nd Embodiment. The perspective view which shows the other specific example of the antenna part of 2nd Embodiment. The perspective view which shows the other specific example of the antenna part of 2nd Embodiment. The perspective view which shows the other specific example of the antenna part of 2nd Embodiment. The block diagram of the antenna apparatus 300 according to 3rd Embodiment which concerns on this invention. The block diagram of the antenna apparatus 400 according to 4th Embodiment which concerns on this invention.

Explanation of symbols

100 antenna device long side depth of L _C recesses 10 finite ground plane 15 recess 20 feeding point 30 linear element L _B finite ground plane

Claims (8)

An antenna device that resonates with radio waves of a certain frequency,
A finite ground plane having a longitudinal direction and having a recess provided on a long side extending in the longitudinal direction;
A feeding point provided near one end of the long side of the finite ground plane;
_A linear element that is fed from the feeding point and has a length L _A that is not less than ¼ of the wavelength λ of the resonance frequency of the antenna device, and
When the length of the long side of the finite ground plane is L _B and the depth of the recess is L _C , Equation 1
L _A + L _B + 2 * L _C = λ (Formula 1)
An antenna device characterized by satisfying   2. The antenna device according to claim 1, wherein the concave portion is provided at a position separated from one end of the long side of the finite ground plane by (1/4) * λ to (1/2) * λ. .   The antenna device according to claim 1, wherein the depth of the concave portion is (1/8) * λ or less.   The antenna device according to claim 1, wherein a plurality of the concave portions are provided on a long side of the finite ground plane. The recess is provided with N (N = 2, 3, 4...)
When the wavelength of the resonance frequency of the antenna device is λ, the length of the long side of the finite ground plane is L _B , and the depth of the recess is L _k (k = 1 to N), respectively, Equation 5
L _A + L _B + 2 * ΣL _k = λ (where Σ = L ₁ + L ₂ +... L _N−1 + L _N ) (Formula 5)
The antenna device according to claim 4, wherein:   The antenna device according to claim 1, wherein the linear element is a meander type, helical type, or coil type linear element.   The one end of the linear element is connected to the feeding point, and the other end of the linear element is connected to the finite ground plane via a variable capacitance element. An antenna device according to claim 1.   One end of the linear element is connected to the feeding point, the other end of the linear element is opened, and a part between the one end and the other end of the linear element is connected to the finite ground plane via a variable capacitance element. The antenna device according to claim 1, wherein the antenna device is connected to the antenna device.

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