JP2005303348A - Antenna and communications apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized, broadband antenna having desirable characteristics as an antenna, usable particularly for UWB communication such as group delay characteristics, radiation pattern characteristics, and port characteristics, which are flat over a broad band. <P>SOLUTION: In the antenna comprising a radiator 2 and a ground plane 3, a figure, obtained by carrying out a conversion operation T for a finite number of times, is employed for the shape of the radiator 2, wherein the conversion operation T includes that a two-dimensional planar figure is reduced; n sets of the reduced figures are copied, the copies are arranged on a circle; and the resulting figure is overwritten on the original figure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna and a communication apparatus, and is particularly suitable for application to a wideband antenna used for UWB (Ultra Wide Band) communication.

  A communication method called UWB is a communication method using a pulse signal having a very narrow pulse width and a very wide band. That is, in UWB, a specific frequency, that is, a ratio between a center frequency and a frequency bandwidth is 25% or more, or a wide frequency band having a width of 500 MHz or more is used, and information is transmitted as a stream of ultrashort pulses, which is about several meters. High-speed communication of several hundred Mbps can be realized within a short distance. In UWB, high-speed and high-capacity communication can be performed without disturbing existing communication systems by using a wide frequency band and suppressing the energy density per unit frequency low.

In this UWB communication, since a signal covers a wide band, a wide band element is necessary for actual communication. In particular, a small antenna having a wide band characteristic is required. In addition, the characteristics of the antenna used for UWB communication are required to have not only port characteristics such as the S parameter S ₁₁ but also flat directivity patterns and impulse responses (group delay characteristics). In particular, the group delay characteristic is important in UWB communication using ultrashort pulses. If this group delay characteristic is not flat, the pulse waveform radiated from the antenna is distorted, and the quality of UWB communication that is mainly processed in the time domain is significantly degraded.

  As a candidate for this antenna, a traveling wave type antenna such as a conical type or a log periodic type antenna can be cited. In addition, so-called fractal antennas that use self-similar figures as antenna shapes are said to be small and have broadband characteristics, as disclosed in Patent Documents 1 to 4 and Non-Patent Document 1. A typical example of this fractal antenna is one using a shellpinski figure.

FIG. 12A is a perspective view illustrating a schematic configuration of a shell pin ski antenna, and FIGS. 12B to 12D are plan views illustrating a method for generating a shell pin ski figure.
In FIG. 12A, a radiator 131 is disposed vertically on the ground plane 132, and a power supply 133 is connected between the radiator 131 and the ground plane 132. Here, the radiator 131 uses a self-similar triangular antenna pattern called a Shellpinsky figure.

As shown in FIGS. 12B to 12D, the Sherpinski figure can be generated by repeatedly performing conversion that sequentially removes the center of the triangle. In other words, this transformation takes a coordinate axis, and operates an arbitrary point S (x, y) in a triangle surrounded by the origin O, the point P (a, b), and the point Q (-a, b) as follows. Is an operation for mapping to three points S ₀ (x ₀ , y ₀ ), S ₁ (x ₁ , y ₁ ), and S ₂ (x ₂ , y ₂ ).

S (x, y) → S ₀ (0.5x, 0.5y)
→ S ₁ (0.5a + 0.5x, 0.5b + 0.5y)
→ S ₂ (-0.5a-0.5x, 0.5b + 0.5y)
FIG. 12B illustrates a case where P (a, b) = P (1, √3) and Q (a, b) = Q (−1, √3). If this conversion is repeated, it can be changed sequentially as shown in FIG. 12 (B) → FIG. 12 (C) → FIG. 12 (D). FIG. 12A shows a case where this conversion is performed four times. Since this conversion is repeated, it becomes a self-similar shape, and when this figure is enlarged twice, it can be overlaid on the original figure. In other words, if the height of the original triangle is H, the height of the triangle removed by the first transformation is H / 2, and the height of the triangle removed by the second transformation is H / 4. The height of the triangle removed by the conversion is H / 8, and the height of the triangle removed by the fourth conversion is H / 16. When an antenna is configured using a self-similar figure, its frequency characteristic is repeated geometrically due to the characteristic shape of self-similarity.
Spanish Patent PR No. PCT / ES99 / 00296 (WO0122528) Specification Japanese translation of PCT publication No. 2003-510871 US Pat. No. 6,104,349 US Patent No. US6127777 IEEE TRANS. ANTENNAS AND PROPAGATION, VOL. 46, no. 4. APRIL 1998

However, in a traveling wave type antenna such as a conical type or a log periodic antenna, the size of the antenna increases when attempting to obtain uniform characteristics over a wide band. In addition, although the fractal antenna is small and can realize a wide band characteristic, the characteristic in the band is not uniform, and an attempt to obtain a uniform characteristic increases the size of the antenna.
When the antenna becomes larger, the directivity characteristic generally has frequency characteristics. On the other hand, when the size of these antennas is limited, the frequency characteristics are generally not flat. For example, in a fractal antenna using a shellpinski figure, the ripple period changes geometrically with a term ratio of 2. Become. In Patent Documents 1 to 4, it is said that if a fractal graphic is used for the antenna element, it is possible to increase the bandwidth and reduce the size. However, in these documents, a wideband frequency characteristic that can be used for UWB communication, The fractal figure from which directivity pattern characteristics and group delay characteristics are obtained is not specified.

In recent years, the frequency band for UWB communication approved by the US FCC is 3.1 GHz to 10.6 GHz. The ratio band is 100% or more, and no small antenna that can be used in such a wide frequency band has been reported.
Accordingly, an object of the present invention is to provide an antenna and a communication apparatus that can ensure the flatness of the group delay characteristic, the radiation pattern characteristic, and the two-port characteristic over a wide band while reducing the size.

In order to solve the above-described problem, according to the antenna of one embodiment of the present invention, an operation in which the shape of the radiator is arranged on the circumference of a figure obtained by reducing a two-dimensional plane figure, and It is a figure obtained by performing transformation including the operation of overwriting the placed part over the original figure a finite number of times.
As a result, the shape of the radiator becomes a self-similar figure, and it is possible to reduce the size and bandwidth of the antenna, and to arrange the reduced figure on the circumference to flatten the group delay characteristic. it can.

  Further, according to the antenna of one embodiment of the present invention, in the antenna including the radiator and the ground plane, the shape of the radiator includes an operation for reducing a two-dimensional plane figure and the reduced figure as n ( n including an operation of duplicating only n), an operation of placing the duplicated figure on the circumference, and an operation of overwriting the original figure on the figure arranged on the circumference Is a figure obtained by performing finite times.

Thereby, it becomes possible to make the shape of a radiator into a self-similar figure, and it becomes possible to lengthen the electric current path which goes around outside. For this reason, it is possible to reduce the size of the antenna while increasing the bandwidth, and it is possible to flatten the group delay characteristic by arranging the reduced figure on the circumference.
According to the antenna of one embodiment of the present invention, the ground plane is placed on the same substrate as the radiator.

  As a result, the ground plane and the radiator can be arranged on the same plane, and a complicated three-dimensional structure is not required, and an antenna can be mounted as a printed pattern on a printed board or the like. For this reason, it becomes possible to facilitate the mounting of the antenna, it is possible to flatten the group delay characteristic of the antenna while suppressing an increase in cost, and it is possible to reduce the size and increase the bandwidth. .

Further, according to the antenna of one aspect of the present invention, the ground plane includes a microstrip line that is disposed on a surface facing the substrate surface on which the radiator is disposed, and is connected to the radiator. And
Thereby, it becomes possible to feed power from the opposite side of the substrate surface on which the radiator is arranged. For this reason, it is possible to share the board on which the radiator is disposed with the printed circuit board, and it is possible to place electronic components on the board on which the radiator is disposed, and to move the feeding point by the microstrip line. Therefore, the degree of freedom of component placement is increased, and the communication device equipped with the antenna can be downsized.

According to the antenna of one embodiment of the present invention, the ground plane is placed orthogonal to the plane of the radiator.
As a result, power can be supplied to the antenna from the lower side of the ground plane, and the radiator can be separated from the power supply circuit. For this reason, unnecessary coupling can be eliminated and the influence of noise and unnecessary radiation can be reduced, and the group delay characteristic can be flattened while the antenna can be downsized and widened.

According to the antenna of one aspect of the present invention, the graphic arranged on the circumference is arranged so that at least a part thereof overlaps the original graphic.
As a result, it is possible to electromagnetically couple self-similar figures while arranging reduced figures on the circumference, and it is possible to achieve a wider band while reducing the size of the antenna and to achieve group delay. The characteristics can be flattened.

In the antenna according to one aspect of the present invention, the area of the overlapping portion is in the range of 20 to 80% of the area of the reduced figure arranged on the circumference.
As a result, it is possible to generate a self-similar figure while suppressing an increase in the acute angle portion, and it is possible to reduce multiple reflections and suppress deterioration in phase characteristics. For this reason, it is possible to efficiently transmit ultrashort pulses, and it is possible to suppress distortion of the pulse waveform and improve the quality of UWB communication.

According to the antenna of one embodiment of the present invention, the two-dimensional plane figure is a ring shape, an ellipse, or a saddle shape.
Accordingly, it is possible to generate a self-similar figure while suppressing an increase in the acute angle portion, and it is possible to flatten the group delay characteristic.
Further, according to the antenna of one embodiment of the present invention, in the antenna including the radiator and the ground plane, the shape of the radiator includes an operation for reducing a two-dimensional plane figure and the reduced figure as n ( n including an operation of duplicating only n), an operation of placing the duplicated figure on the circumference, and an operation of overwriting the original figure on the figure arranged on the circumference Is a figure obtained by further reducing or enlarging a figure obtained by performing finite times in the horizontal direction.

As a result, the frequency characteristics of the antenna can be adjusted to be flatter and wider, and the degree of freedom in designing a wideband antenna can be improved.
The antenna according to one aspect of the present invention is characterized in that the number of conversions is 1 and the number of replicas n is 8.
Thereby, when generating a self-similar figure, it becomes possible to ensure that the antenna characteristic is ensured, and to prevent the radiator from being miniaturized in shape. As a result, the antenna can be easily designed and the processing accuracy at the time of antenna creation can be relaxed, and the antenna can be reduced in size and bandwidth while suppressing an increase in cost. In addition, the group delay characteristic can be flattened.

According to the antenna of one embodiment of the present invention, in an antenna including a radiator and a ground plane, the shape of the radiator is a first annular ring and a first annular ring reduced in size. And an N-th ring (N is an integer having two or more consecutive values) arranged on the circumference so as to be electromagnetically coupled to the (N-1) ring. .
As a result, it is possible to make the shape of the radiator self-similar while suppressing an increase in the acute angle portion, and it is possible to reduce the multiple reflection and to increase the current path around the outside. Become. For this reason, it is possible to reduce the size and bandwidth of the antenna and to suppress the deterioration of the phase characteristics, and to flatten the group delay characteristics.

Moreover, according to the communication apparatus which concerns on 1 aspect of this invention, it has one of the antennas mentioned above, It is characterized by the above-mentioned.
As a result, it is possible to flatten the group delay characteristic while enabling the antenna to be downsized and widened, and the high-speed communication of several hundreds of Mbps at a short distance within several tens of meters while miniaturizing the communication device. Can be realized.

Hereinafter, a broadband antenna according to an embodiment of the present invention will be described with reference to the drawings.
1A is a plan view showing a schematic configuration of the wideband antenna according to the first embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line aa ′ in FIG. is there.
In FIG. 1, the broadband antenna is provided with a substrate 1, a radiator 2, and a ground plane 3, and the radiator 2 and the ground plane 3 are disposed on the same surface of the substrate 1. In addition, the board | substrate 1 is comprised from a dielectric material, and the radiator 2 and the ground plane 3 are comprised from conductors, such as a metal. Further, the radiator 2 and the ground plane 3 are respectively provided with feeding points 4 and 5.

  Here, the radiator 2 is provided with conductor patterns 2a and 2b. In the shape of the radiator 2, the conductor pattern 2a is reduced and duplicated by n (n is an integer of 1 or more), and the duplicated conductor pattern 2b is arranged at equal intervals on the circumference. The figure includes a figure obtained by performing a finite number of conversions overwriting the conductor pattern 2b over the conductor pattern 2b arranged on the circumference. The overwriting means replacing the portion where the conductor pattern 2b is arranged with the conductor pattern 2a while keeping the shape of the conductor pattern 2b, that is, preventing the hole portion of the conductor pattern 2b from being crushed by the conductor pattern 2a. That means.

Thereby, it becomes possible to make the shape of radiator 2 into a self-similar figure, and it becomes possible to lengthen the current path around the outside. For this reason, it is possible to reduce the size of the wideband antenna and to increase the bandwidth, and to flatten the group delay characteristics by arranging the conductor pattern 2b similar to the conductor pattern 2a on the circumference. be able to.
Further, it is preferable that at least a part of the conductor pattern 2b is arranged so as to overlap the conductor pattern 2a, and the area of the overlapping portion of the conductor patterns 2a and 2b is filled when the inside of the conductor patterns 2a and 2b is respectively filled. It is preferable to be within a range of 20 to 80% of the area of the conductor pattern 2b. Moreover, it is preferable that the shape of the conductor patterns 2a and 2b is a closed curve such as an annular shape, an ellipse, or a saddle shape. As a result, it is possible to generate a self-similar figure while suppressing the occurrence of an acute angle portion in the shape of the radiator 2, to reduce multiple reflections, and to suppress deterioration of phase characteristics. it can. For this reason, in ultra-short-time pulse transmission, distortion of the pulse waveform can be suppressed, communication can be performed efficiently, and the quality of UWB communication can be improved.

  In the broadband antenna of FIG. 1, the number of conversions is 1, and the number n of the conductor patterns 2b obtained by duplicating the conductor pattern 2a is 8. Thereby, it becomes possible to make the shape of a radiator into a self-similar figure while suppressing complication of the shape of the radiator 2. For this reason, it is possible to easily design a wideband antenna, and it is possible to reduce processing accuracy when creating the wideband antenna.

  In addition, by disposing the radiator 2 and the ground plane 3 on the same surface of the substrate 1, it is possible to mount a broadband antenna as a printed pattern on a printed circuit board or the like without requiring a complicated three-dimensional structure. For this reason, it is possible to facilitate the mounting of the wideband antenna, and it is possible to flatten the group delay characteristic of the wideband antenna while suppressing an increase in cost, and it is possible to reduce the size and increase the bandwidth. It becomes.

  Table 1 shows preferable dimensions when the antenna shown in FIG. 1 is used for UWB communication of 3.1 GHz to 10.6 GHz.

However, in the example of Table 1, it was (first figure the underlying transform) I ₀ the conductive patterns 2a initiator. Further, a is a reduction ratio when generating the conductor pattern 2b by reducing the conductor pattern 2a, and r is a radius of the circle when the conductor pattern 2b is arranged on the circumference. Further, h is a quarter of the wavelength (52.337 mm) of the electromagnetic wave having the geometric mean frequency (5.732 GHz) of the lower limit (3.1 GHz) and the upper limit (10.6 GHz) of the UWB band, that is, 13. 08 mm. Further, the outer radius r _o of the initiator I ₀ indicates a value normalized by h. From Table 1, the height of the radiator, that is, the size of the antenna, can be made much smaller than a quarter (24.2 mm) of the wavelength of the electromagnetic wave at the lower limit frequency of the UWB band. In the wideband antenna according to the present embodiment, since the frequency characteristics are flat, sufficient performance can be obtained within the range of about ± 20% of the dimensional specifications shown in Table 1.

FIG. 2 is a diagram for explaining the S parameter S ₁₁ characteristics of the wideband antenna of FIG. In the S parameter S ₁₁ characteristics of FIG. 3, the standardized impedance of the broadband antenna of FIG. 1 is 50Ω.
2, plot K1 of FIG. 2 shows the S parameter S ₁₁ characteristics of the antenna of FIG. Note that plot K2 in the figure, there is shown by comparing the S parameter S ₁₁ characteristics of the antenna in the case of using the pattern of FIG. 9 as a radiator 2. As can be seen from FIG. 2, the wideband antenna of FIG. 1 can obtain good S-parameter S ₁₁ characteristics over a wide frequency range.

FIG. 3 is a diagram for explaining radiation pattern characteristics in a horizontal plane of the broadband antenna of FIG. 1, that is, a plane perpendicular to the cross section aa ′ and the substrate surface of FIG. 1, and FIG. It is a figure explaining the radiation pattern characteristic in the surface containing the cross section aa 'of FIG. This radiation pattern is an omnidirectional characteristic.
3 and 4, it can be seen that the radiation pattern is almost uniform regardless of the frequency within the band, and exhibits a very good broadband characteristic. It can also be seen that the directivity pattern is non-directional in the horizontal plane and has almost no frequency characteristics.

Also, the antenna size is 1.07h to the protrusion, which is about 1/7 of the wavelength of the band lower limit frequency, and is very small. For this reason, it can be seen that a good phase characteristic (group delay characteristic) can be obtained with little phase center shift.
In addition, in this embodiment mentioned above, although the characteristic in a specific frequency with a specific dimension is illustrated, it is not restricted to this. As is well known, Maxwell's equations are the same if normalized by the wavelength of the electromagnetic wave, so the antenna dimensions should be adjusted in proportion to the wavelength used (ie, inversely proportional to the frequency). Thus, the same characteristics can be obtained.

Hereinafter, a method for generating a radiator shape according to an embodiment of the present invention will be generalized and described.
5A to 5D are plan views illustrating a configuration example of a monopole antenna.
In FIG. 5A, the linear radiator 12 and the ground plane 13 are arranged on the same plane. In addition, feed points 14 and 15 are provided between the linear radiator 12 and the ground plane 13, respectively. Here, the broadband antenna of FIG. 1 is a kind of monopole antenna as shown in FIG. 5A, and it is known that the monopole antenna has a wider frequency characteristic as the shape of the radiator 12 is thicker. .

In FIG. 5B, the disk radiator 22 and the ground plane 23 are arranged on the same plane. In addition, feed points 24 and 25 are provided between the disk radiator 22 and the ground plane 23, respectively.
In FIG. 5C, the annular radiator 32 and the ground plane 33 are arranged on a horizontal plane. Further, feed points 34 and 35 are provided between the annular radiator 32 and the ground plane 33, respectively.

Here, instead of the linear radiator 12 shown in FIG. 5A, when the disk radiator 22 shown in FIG. 5B is used, or when the annular radiator 32 shown in FIG. 5C is used. Compared with the linear radiator 12 of FIG. 5A, the frequency band of both the S parameter S ₁₁ characteristic and the radiation pattern can be expanded.
In FIG. 5D, a double annular radiator 42 and a ground plane 43 are arranged on a horizontal plane. In addition, feed points 44 and 45 are provided between the double annular radiator 42 and the ground plane 43, respectively. Note that the double annular radiator 42 is formed by connecting a plurality of circular rings of different sizes in parallel.

FIG. 6 is a diagram for explaining the S parameter S ₁₁ characteristics of the antenna patterns of FIGS. 5 (A) to 5 (D). The heights of radiators 12, 22, 32, and 42 (the heights measured from the upper ends of ground planes 13, 23, 33, and 43) were all unified to 1.14h.
In FIG. 6, plots K11 to K14 show the disk radiator 22 in FIG. 5B, the annular radiator 32 in FIG. 5C, the linear radiator 12 in FIG. 5A, and FIG. 5D. The S parameter S ₁₁ characteristics of the double annular radiator 42 are respectively shown.

As can be seen from FIG. 6, the disk radiator 22 exhibits a wide band characteristic, but has a high reflectivity and poor efficiency. Moreover, in the annular radiator 22, radiation at a specific frequency becomes strong. It can be seen that these shapes of radiators 22, 32 are not wide enough to be used for UWB.
Further, as shown in FIG. 5 (D), two circular rings of different sizes, for example, two circular rings having a size of 1: 2 are connected in parallel to form a double annular radiator 42, aiming at broadening the bandwidth. It can be seen from FIG. 6 that there is almost no effect in widening the bandwidth.

On the other hand, when a figure obtained by repeatedly overlapping annulus in a self-similar manner by the transformation T as described below is used as a radiator, good frequency characteristics can be obtained. That is, when the initiator and I _0, using the graphic I _n obtained the transformation T to the initiator I ₀ applies only n times as radiator shape.
Here, if the i-th figure is I _i ,
I _{i + 1} = TI _i
It is. Where T is

It is.
Here, M (x, y) is a transformation that moves the figure in the x and y directions (x, y), S (a) is a transformation that resizes the figure to a times, and * is two transformations. Represents the bond of. That is, the term of the symbol Σ means that a given figure is size-converted to a times (reduced when a <1), and is arranged at n equal intervals on the circumference of the radius r. The last term 1 is the identity transformation and indicates that it is superimposed on the original figure. Note that the term of Σ is overwritten so that the interior (hole) of I _i is not crushed by the original figure as a result of superposition with the original figure.

By making the figure obtained by such conversion T into the shape of the radiator, the group delay characteristic can be flattened while making it possible to reduce the size and increase the bandwidth of the broadband antenna.
FIG. 7 is a plan view showing a specific example of a method for generating a radiator shape of a broadband antenna according to the second embodiment of the present invention.

In FIG. 7A, as the initiator I ₀ , a ring S1 having an outer radius = 1 and an inner radius = 0.75 is used. Then, in the case of r = 1, n = 8, and a = 0.25, the ring S2 is overwritten on the ring S1 in FIG. to obtain a conversion figure I ₁ in FIG. 7 (B).
Further, by applying the transformation T with respect to the annular S2, to obtain a conversion figure I ₂ in Figure 7 Figure 7 that the annular S3 on the ring S1, S2 of (B) is overwritten (C). Further, by applying transformation T with respect to the annular S3, to give the 7 ring S1, S2, converts graphics I ₃ of FIG. 7 annular S4 is overwritten on the S3 (D) of the (C) .

Here, when the reduction ratio a is small, the figure obtained by repeating the conversion T is rapidly refined. On the other hand, a very fine structure with respect to the wavelength does not affect the antenna characteristics. For this reason, one conversion is sufficient when the number of conversions is n = 8.
In FIG. 7E, the ring S2 ′ is overwritten on the ring S1 ′, and the ring S3 ′ is overwritten on the ring S2 ′. In addition, the arrangement | positioning relationship of circular rings S1'-S3 'of FIG.7 (E) is the same as that of circular rings S1-S3 of FIG.7 (C), and the shape of FIG.7 (E) is a circular ring. The line width of S1 ′ to S3 ′ is constant. Thereby, it becomes possible to prevent the line widths of the circular rings S1 ′ to S3 ′ from becoming sharply narrow due to the repetition of the transformation T, and it is possible to facilitate the antenna processing while maintaining the necessary antenna characteristics. Become.

  FIG. 8 is a plan view illustrating the radiator shape of the broadband antenna according to third to seventh embodiments of the present invention. In addition, the radiator shape of FIG. 8 (A)-(D) was each produced | generated based on the item of Table 2 below.

In FIG. 8A, when n = 3, it has a structure similar to a Sherpinski figure and the characteristics are close to that. However, in the figure of FIG. 8A, since the initiator I ₀ is a ring, the broadband characteristic of the initiator I ₀ appears, and more preferable antenna characteristics can be obtained. When the transformation T shown in the equation (1) is performed, the upside down figure of FIG. 8A is obtained. In FIG. 8A, it is easy to see on the assumption that the feeding point is below. Inverted.

Further, FIG. 8 (B), the in (C), by smaller than the outer diameter r _o of the initiator I ₀ values of r, repeating shapes for each of the conversion can be generated graphic stand out on the inside. Further, in FIG. 8 (D), the by larger than the outer diameter r _o of the initiator I ₀ values of r, graphics for each repetition of the conversion can be generated graphic stand out to the outside. Here, the figure in FIG. 8D can make the current path around the outside longer, and better antenna characteristics can be obtained than the figures in FIGS. 8B and 8C.

Further, by appropriately adjusting r, as shown in FIG. 8 (E), it is possible to make a figure in which only a hole portion is opened in the initiator I ₀ without making a business trip to the outside or inside even if conversion is repeated. Can do. 8A and 8D in which the length of the outer periphery is the longest is the most suitable for miniaturization.
Note that any of the figures in FIGS. 8A to 8E may be used as the radiator shape of the broadband antenna. However, it seems that the specifications shown in Table 1 show good characteristics as a UWB antenna having a band of 3.1 GHz to 10.6 GHz.

The thickness of the dielectric substrate of the antenna illustrated here is 2 mm or less and the non-dielectric constant is about 4. However, there is no significant difference in characteristics unless the substrate is extremely thick. Further, the antenna characteristics on the wide area side can be improved by lowering the relative dielectric constant of the substrate.
FIG. 9 is a plan view showing a radiator shape of the wideband antenna according to the eighth embodiment of the present invention.

In FIG. 9, the shape of radiator 2 ′ is expanded or reduced by a factor of b in the lateral direction while maintaining a constant height with respect to the shape of radiator 2 of FIG. 1. In FIG. 9, the case of b = 0.8 is illustrated. This makes it possible to improve the characteristics of S parameters S _11. This is shown in the plot K2 in FIG. That is, compared with the radiator 2 of FIG. 1 that does not reduce in the horizontal direction, the radiator 2 ′ that is reduced in the horizontal direction can extend the broadband side, and can improve the characteristics. However, since the heights of the radiators 2 and 2 'are the same, the characteristics in the low band are almost the same.

FIG. 10A is a plan view showing a schematic configuration of the wideband antenna according to the ninth embodiment of the present invention, and FIG. 10B is a cross-sectional view taken along the line bb ′ of FIG. is there.
In FIG. 10, the broadband antenna is provided with a substrate 111, a radiator 112, a ground plane 113, and a microstrip line 116. Here, the radiator 112 and the microstrip line 116 are disposed on one surface of the substrate 111, and the radiator 112 is connected to the microstrip line 116. In addition, the ground plane 113 is disposed on a surface facing the substrate surface on which the radiator 112 is disposed, and the microstrip line 116 is led out to the back surface of the substrate 111. The ground plane 113 and the microstrip line 116 are provided with feeding points 114 and 115, respectively, and can feed the radiator 112 via the microstrip line 116. The width of the microstrip line 116 can be determined by the dielectric constant and thickness of the substrate 111 and can be adjusted so that the normalized impedance is 1.

  The radiator 112 is provided with conductor patterns 112a and 112b. In the shape of the radiator 112, the conductor pattern 112a is reduced and duplicated by n pieces, the duplicated conductor patterns 112b are arranged at equal intervals on the circumference, and the conductors arranged on the circumference are arranged. A figure obtained by performing a limited number of conversions to overwrite the conductor pattern 112a with the pattern 112b is included.

Here, by arranging the ground plane 113 on a surface opposite to the substrate surface on which the radiator 112 is disposed, power can be supplied from the opposite side of the substrate surface on which the radiator 112 is disposed. Therefore, the substrate 111 on which the radiator 112 is disposed can be shared with the printed circuit board, and electronic components and the like can be disposed on the substrate surface and the ground plane surface on which the radiator 112 is disposed. The mounted communication apparatus can be reduced in size. The characteristics of the wideband antenna shown in FIG. 10 are the same as those shown in FIGS. 3 to 5, and good antenna characteristics can be obtained for UWB communication.

FIG. 11 is a perspective view showing a schematic configuration of the wideband antenna according to the tenth embodiment of the present invention.
In FIG. 11, the broadband antenna is provided with a radiator 122 and a ground plane 123, and the radiator 122 is arranged perpendicular to the ground plane 123. Further, the radiator 122 and the ground plane 123 are provided with feeding points 124 and 125, respectively. The feeding to the radiator 122 can be performed from the back side of the ground plane 123 via a coaxial cable. Here, the radiator 122 is provided with conductor patterns 122a and 122b, and the shapes of the conductor patterns 122a and 122b are self-similar figures created by the method described above with the circular ring as the initiator I _0. Can do.

  Here, by arranging the radiator 122 perpendicular to the ground plane 123, the radiator 122 can be placed on the opposite side of the ground plane 123. For this reason, the influence of the sneaking into the radiator 122 such as noise generated by the circuit can be reduced, and the communication quality can be improved. This is particularly effective when used as a receiving antenna. The characteristics of the broadband antenna shown in FIG. 11 can be the same as those of the broadband antenna shown in FIGS.

As described above, the above-described broadband antenna has a small size, a simple structure, and sufficient broadband characteristics. In particular, not only the port characteristics represented by the S parameter S ₁₁ but also the radiation pattern and phase characteristics (group delay characteristics). ) Also exhibits a flat broadband characteristic and is highly practical in UWB communication. For this reason, by applying the above-described broadband antenna to a wireless PAN (Personal Area Network) or the like, high-speed communication of several hundreds Mbps can be realized in a short distance of about several meters while downsizing the communication device. .

The figure which shows schematic structure of the wideband antenna which concerns on 1st Embodiment of this invention. Diagram illustrating the S parameter S ₁₁ characteristics of the antenna of FIG. The figure explaining the radiation pattern characteristic in the horizontal surface of the broadband antenna of FIG. The figure explaining the radiation pattern characteristic in the vertical plane of the broadband antenna of FIG. The top view which shows the structural example of a monopole antenna. Diagram illustrating the S parameter S ₁₁ characteristics of the antenna pattern in FIG. The top view which shows the production | generation method of the radiator shape of the wideband antenna which concerns on 2nd Embodiment of this invention. The top view which illustrates the radiator shape of the wideband antenna which concerns on the 3rd-7th embodiment of this invention. The top view which shows the radiator shape of the wideband antenna which concerns on 8th Embodiment of this invention. The figure which shows schematic structure of the wideband antenna which concerns on 9th Embodiment of this invention. The figure which shows schematic structure of the wideband antenna which concerns on 10th Embodiment of this invention. The figure which shows an example of the conventional wideband antenna.

Explanation of symbols

  1, 111 substrate, 2, 2 ′, 12, 22, 32, 42, 112, 122 radiator, 2a, 2b, 112a, 112b, 122a, 122b conductor pattern 3, 13, 23, 33, 43, 113, 123 Ground plane 4, 5, 14, 15, 24, 25, 34, 35, 44, 45, 114, 115, 124, 125 Feed point, 51-54, 51'-53 'Ring, 116 Microstrip line

Claims (12)

  Perform a finite number of transformations, including the operation of placing the figure obtained by reducing the two-dimensional plane figure on the circumference and the operation of overwriting the placed part on the original figure. An antenna characterized by being a figure to be obtained. In antennas including radiators and ground planes,
The shape of the radiator includes an operation for reducing a two-dimensional plane figure, an operation for duplicating the reduced figure by n (n is an integer of 1 or more), and arranging the duplicated figure on the circumference. The antenna is obtained by performing a limited number of transformations including an operation for performing an operation for overwriting an original graphic with a graphic arranged on the circumference.   The antenna according to claim 2, wherein the ground plane is placed on the same substrate as the radiator.   3. The antenna according to claim 2, wherein the ground plane includes a microstrip line disposed on a surface opposite to a substrate surface on which the radiator is disposed, and connected to the radiator.   The antenna according to claim 2, wherein the ground plane is placed perpendicular to a plane of the radiator.   6. The antenna according to claim 1, wherein the graphic arranged on the circumference is arranged so that at least a part thereof overlaps the original graphic.   The antenna according to claim 6, wherein an area of the overlapping portion is in a range of 20 to 80% of an area of the reduced figure arranged on the circumference.   The antenna according to claim 1, wherein the two-dimensional plane figure is a ring shape, an ellipse shape, or a saddle shape. In antennas including radiators and ground planes,
The shape of the radiator includes an operation for reducing a two-dimensional plane figure, an operation for duplicating the reduced figure by n (n is an integer of 1 or more), and arranging the duplicated figure on the circumference. And a figure obtained by further reducing or enlarging a figure obtained by performing a finite number of transformations including an operation to overwrite the original figure with a figure placed on the circumference. Characteristic antenna.   The antenna according to any one of claims 2 to 9, wherein the number of conversions is 1, and the number of replicas n is 8. In antennas including radiators and ground planes,
The shape of the radiator is a first ring and a first ring arranged on the circumference so that the first ring can be reduced and electromagnetically coupled to the (N-1) -th ring. An antenna having N rings (N is an integer having two or more consecutive values).   A communication apparatus comprising the antenna according to claim 1.

Images