JP2013012952A - Antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antenna operational in a wideband while avoiding interference on a portion of the band.SOLUTION: An antenna 1 includes dielectric substrate 10, radiation element 11, power supply line 12 and base plate 13. The power supply line 12 is a stripe-shaped conductor having an uneven width, in which a folding portion is folded to form a smooth curve. By the power supply line 12 and the base plate 13 mutually overlapped through the dielectric substrate 10, a microstrip line functioning as a BRF (band reject filter) is configured.

Description

  The present invention relates to an antenna having a wide operating band such as a microwave band (3.1 GHz to 10.6 GHz) used for UWB (Ultra Wide Band).

  In recent years, there has been an increasing demand for a broadband antenna having a wide operating band such as a microwave band used for UWB. However, this microwave band includes a 5 GHz band used for other wireless communication standards, for example, a wireless LAN (IEEE802.11a). Therefore, such a broadband antenna is strongly required to have a low coherence that does not interfere with a band used for other wireless communication standards in addition to a wide band covering the microwave band.

  As an antenna satisfying such a requirement, for example, a patch antenna described in Patent Document 1 is known. In the patch antenna described in Patent Document 1, a wide band is achieved by forming a stub on the radiating element or forming a step on the ground plane. In addition, interference with the wireless LAN is reduced by forming a slit in the radiating element.

  As a BRF (Band Reject Filter) for a radio station of a UWB system, the one described in Patent Document 2 is known. The BRF described in Patent Document 2 has a microstrip line with a non-uniform width in order to increase the reflection coefficient in a specific band (a band where interference should be avoided).

Special table 2008-535372 (publication date: August 28, 2008) JP 2010-50653 (release date: March 4, 2010)

  However, in the patch antenna described in Patent Document 1, it is necessary to design a slit corresponding to a band in which interference should be avoided, but there is a problem that this design is difficult. Specifically, although a guideline indicating that a slit having a length of about half the wavelength corresponding to the band where interference should be avoided is provided, the expected reflection coefficient can be obtained by bending the slit. However, in order to obtain the expected reflection coefficient, there was a problem that the prototype had to be repeated. On the other hand, when a linear slit having a length corresponding to about half the wavelength corresponding to the band where interference should be avoided is provided, there is a problem that the size of the radiating element is increased.

  Further, although the BRF described in Patent Document 2 has a desirable property that a reflection coefficient can be obtained as expected even when the microstrip line is folded, a method for integrating this with the antenna has not been known. In addition, when the antenna and the filter are integrated, there has been no known design method for maintaining the same level of characteristics as the single antenna outside the band where interference should be avoided.

  The present invention has been made in view of the above problems, and an object of the present invention is an antenna that can operate in a wide band but avoids interference in a part of the band, and is easier to design than the conventional one. It is to realize a small antenna.

  In order to solve the above problems, an antenna according to the present invention includes a dielectric substrate, a radiating element and a feed line formed on one main surface of the dielectric substrate, and the other main surface of the dielectric substrate. An antenna including a formed ground plane, wherein the feeder line is a strip-like conductor having a non-uniform width folded so that a folded portion draws a smooth curve, and overlaps with each other via the dielectric substrate A microstrip line that functions as a BRF (Band Reject Filter) is constituted by the power supply line and the ground plane.

  According to the above configuration, since the microstrip line constituted by the feeder line and the ground plane functions as a BRF (Band Reject Filter), it can operate in a wide band, but interferes with a part of the band. An avoided antenna can be realized. At this time, since the microstrip line is formed on the ground plane, there is no possibility of causing an increase in size of the antenna in order to avoid interference. In addition, the band in which interference can be avoided is determined by the width of each part of the feed line, and does not vary greatly depending on how the feed line is folded back, so the degree of freedom in design is high.

  In the antenna according to the present invention, the feeding line has a maximum width W [mm], and its central axis is folded so as to draw an arc having a radius R [mm], and the ratio R / It is preferable that W is 2.5 or more.

  According to said structure, S11 in frequencies other than the band which should avoid interference can be made smaller than S11 when ratio R / W is 2.5 or less.

  In the antenna according to the present invention, the ratio R / W is preferably 3.0 or more.

  According to said structure, S11 in frequencies other than the band which should avoid interference can be made smaller than -5dB.

  In the antenna according to the present invention, the ratio R / W is preferably 3.5 or more.

  According to said structure, S11 in frequencies other than the band which should avoid interference can be made smaller than -10 dB.

  In the antenna according to the present invention, the radiating element is formed in a bell shape including a rectangular part and a semi-elliptical semi-elliptical part, and the height h of the rectangular part with respect to the width w of the rectangular part. The ratio h / w is preferably 0.5 or more and 0.75 or less.

  According to said structure, VSWR in frequencies other than the band which should avoid interference can be restrained to 3.5 or less.

  In the antenna according to the present invention, the radiating element is formed into a bell shape including a rectangular part and a semi-elliptical semi-elliptical part, and the length of the semi-ellipse with respect to the short axis b of the semi-elliptical part. The ratio b / a of the axis a is preferably 0.5 or more and 1.0 or less.

  According to said structure, VSWR in frequencies other than the band which should avoid interference can be restrained to 3.5 or less.

The antenna according to the present invention further includes a rectangular matching portion interposed between the radiating element and the feed line, and a ratio w of a width w ′ of the matching portion to a height h ^′ of the matching portion. It is preferable that '/ h ^' is 2.

  According to said structure, VSWR in frequencies other than the band which should avoid interference can be suppressed to 4 or less.

  In the antenna according to the present invention, a microstrip line that functions as a BRF (Band Reject Filter) is configured by a feed line and a ground plane that overlap each other via a dielectric substrate. Therefore, it is possible to realize a small antenna that can operate in a wide band but avoids interference in a part of the band and has a structure that can avoid interference more easily than in the past.

It is a figure which shows the structure of the antenna which concerns on one Embodiment of this invention. (A) is the top view which looked at the antenna from the upper surface, (b) is the top view which looked at the antenna from the lower surface, (c) is sectional drawing of an antenna. It is a figure which shows the structure of the feeder provided with the antenna shown in FIG. (A) is the top view which looked at the feed line from the upper surface, (b) is an enlarged view of the linear part of a feed line, (c) is an enlarged view of the return part of a feed line. It is a circuit diagram which shows the equivalent circuit equivalent to the wire element of the microstrip line comprised by the feeder provided with the antenna shown in FIG. 1, and a ground plane. It is a graph which shows the frequency characteristic of the VSWR value of the antenna shown in FIG. (A) shows a VSWR characteristic when a linear strip-shaped conductor having a uniform width is used as a feed line, and (b) shows a strip-shaped conductor folded back with a non-uniform width as a feed line (shown in FIG. 2). The VSWR characteristics when using the above-mentioned (1) are shown. The dotted line corresponds to the theoretical value (calculated value), and the solid line corresponds to the actually measured value (measured value). It is a graph which shows the frequency characteristic of | S11 | when R = 4mm, when R = 5mm, and when R = 6mm. A graph in which R / W is obtained by dividing R by the maximum value of the width W of the feeder line, and the maximum value of | S11 | in the band of 1 GHz to 5 GHz and 6 GHz to 11 GHz is plotted while changing R. . The frequency characteristic of | S11 | calculated from q (x) obtained by solving the Zakharov-Shabat equations (3) and (4) using the Runge-Kutta method (dotted line) and the measured | S11 | It is a graph which shows a frequency characteristic (solid line). It is a top view which shows the structure of the radiation element with which the antenna shown in FIG. 1 is provided. It is the graph which showed how the frequency characteristic of a VSWR value changes with the shape of the 1st rectangular part of the radiation element shown in FIG. It is the graph which showed how the frequency characteristic of a VSWR value changes with the shape of the semi-ellipse part of the radiation element shown in FIG. It is the graph which showed how the frequency characteristic of a VSWR value changes with the shape of the 2nd rectangular part of the radiation element shown in FIG. It is a graph which shows the radiation pattern in XY plane of the antenna shown in FIG. (A) shows a radiation pattern at 4 GHz, (b) shows a radiation pattern at 5.5 GHz, and (c) shows a radiation pattern at 8 GHz.

  The antenna according to this embodiment will be described below with reference to the drawings.

  The antenna according to this embodiment is used for a wireless LAN (IEEE802.11a) from a microwave band (3.1 GHz to 10.6 GHz) used for UWB (Ultra Wide Band). The band excluding the 5 GHz band (5.15 GHz to 5.85 GHz) is set as the operation band. However, the present invention can be generally applied to an antenna that operates in a band excluding the second band from the first band, and the combination of the first band and the second band is the above-described microwave band. It is not limited to the combination of and 5 GHz band.

  In the following description, of the six surfaces constituting the plate-like member, two surfaces having the largest area are described as “main surfaces”, and four surfaces excluding the main surfaces are described as “end surfaces”. . When it is necessary to distinguish two main surfaces from each other, one main surface is described as “upper surface” and the other main surface is described as “lower surface”. The descriptions of “upper surface” and “lower surface” are for distinguishing the two main surfaces from each other, and do not limit the arrangement of the plate-like members.

[Antenna structure]
The structure of the antenna 1 according to this embodiment will be described with reference to FIG. 1A is a plan view of the antenna 1 as viewed from above, FIG. 1B is a plan view of the antenna 1 as viewed from below, and FIG. 1C is a cross-sectional view taken along line AA ′. It is sectional drawing of the antenna 1 in (refer Fig.1 (a)).

  As shown in FIGS. 1A to 1C, the antenna 1 includes a dielectric substrate 10 and a radiating element 11 formed on one main surface (hereinafter referred to as “upper surface”) of the dielectric substrate 10. And a power supply line 12 and a ground plane 13 formed on the other main surface (hereinafter referred to as “lower surface”) of the dielectric substrate 10. The antenna 1 is supplied with a high frequency current from an end point 12b of the feed line 12 and a feed point provided on an end side 13a of the ground plane 13, and functions as a monopole antenna.

  The dielectric substrate 10 is a plate-shaped dielectric having a rectangular main surface. In the present embodiment, the long side length WZ of the main surface is 100 mm, the short side length WY of the main surface is 60 mm, the thickness is 1.27 mm, and the dielectric constant is 10.2. In the following description, as shown in FIGS. 1A to 1C, the thickness direction of the dielectric substrate 10 is the X-axis direction, and the short side direction of the main surface of the dielectric substrate 10 is the Y-axis direction. The long side direction of the main surface of the dielectric substrate 10 is taken as the Z-axis direction.

  The radiating element 11 is a bell-shaped conductor foil formed in a rectangular region of Wa × WY (Wa = 20 mm in the present embodiment) occupying the Z-axis positive direction side of the upper surface of the dielectric substrate 10. On the other hand, the feed line 12 has a width formed in a region of (Wb + Wc) × WY (Wb = 5 mm, Wc = 75 mm in the present embodiment) occupying the Z-axis negative direction side of the upper surface of the dielectric substrate 10. It is a non-uniform strip-shaped conductor foil. The radiating element 11 and the feeder 12 are integrally formed as a single conductor foil.

  The ground plane 13 is a rectangular conductor foil that covers the entire rectangular area of (Wb + Wc) × WY that occupies the negative Z-axis side of the lower surface of the dielectric substrate 10. That is, the ground plane 13 overlaps with the feeder line 12 and does not overlap with the radiating element 11. The above-described feed line 12 forms a microstrip line together with the ground plane 13 by overlapping with the ground plane 13 and the dielectric substrate 10.

  The radiating element 11 is designed to operate in a microwave band (3.1 GHz to 10.6 GHz) used for UWB. On the other hand, the feed line 12 (more precisely, a part of the feed line 12 formed in a Wc × WY region occupying the Z-axis negative direction side of the upper surface of the dielectric substrate 10) and the ground plane 13 are configured. The microstrip line is designed to function as a BRF (Band Reject Filter) that selectively reflects the 5 GHz band (5.15 GHz to 5.85 GHz) used in wireless LAN (IEEE802.11a). . For this reason, the antenna 1 operates in a band excluding the 5 GHz band (5.15 GHz to 5.85 GHz) from the microwave band (3.1 GHz to 10.6 GHz).

[Structure and function of feeder line]
The structure of the feeder 12 will be described with reference to FIG. 2A is a plan view of the feeder line 12 as viewed from above, FIG. 2B is an enlarged view of a straight line portion of the feeder line 12, and FIG. It is an enlarged view of a return part. 2A shows a portion of the feeder 12 that functions as a BRF, that is, a Wc × WY region that occupies the negative side of the Z-axis on the top surface of the dielectric substrate 10. It is a formed part, and its total length is 227 mm.

  As shown in FIGS. 2B to 2C, the power supply line 12 is a strip-like conductor having a non-uniform width, and as shown in FIG. 2A, the folded portion draws a smooth curve. It is folded back. The reason why the width of the feeder line 12 is not uniform is that the microstrip line formed by the feeder line 12 and the ground plane 13 is a BRF that selectively reflects the 5 GHz band (5.15 GHz to 5.85 GHz). This is to make it function and reduce the area. On the other hand, the reason why the folded structure (meander structure) is adopted is to arrange the feeder 12 in a space of Wc × WY = 75 mm × 60 mm. Note that 227 mm corresponds to two wavelengths of the waveguide mode at 1 GHz, and is considered to be sufficient for causing the microstrip line constituted by the feeder line 12 and the ground plane 13 to function as a BRF. It is. Further, the width W (z) of the feeder line 12 is 2 mm at the maximum.

  The shape of the feeder line 12 can be expressed as follows. That is, as shown in FIG. 2A, the feeder 12 includes (1) a linear portion 12c connected to the radiating element 11 and extending in the negative Z-axis direction, and (2) a radiating element 11 side of the linear portion 12c. A quadrant-shaped folded portion 12d connected to the opposite end point; and (3) a linear portion 12e extending in the negative Y-axis direction connected to the opposite end point of the folded portion 12d to the linear portion 12c side; 4) A semicircular folded portion 12f connected to the end of the straight portion 12e opposite to the folded portion 12d, and (5) a Y-axis connected to the end of the folded portion 12f opposite to the linear portion 12e. A straight portion 12g extending in the forward direction; (6) a semicircular folded portion 12h connected to an end of the straight portion 12g opposite to the folded portion 12f; and (7) a straight portion 12g side of the folded portion 12h. A straight portion 12i extending in the negative direction of the Y-axis connected to the opposite end point; and (8) a straight portion 12i. A semicircular folded portion 12j connected to an end point on the opposite side to the folded portion 12h side, and (9) a straight line portion extending in the positive direction of the Y axis connected to an end point on the opposite side to the linear portion 12i side of the folded portion 12j. 12k, (10) a semicircular folded portion 12l connected to the end of the straight portion 12k opposite to the folded portion 12j, and (11) connected to an end of the folded portion 12l opposite to the straight portion 12k. A linear portion 12m extending in the negative Y-axis direction, (12) a quadrant-shaped folded portion 12n connected to the end of the straight portion 12m opposite to the folded portion 12l side, and (13) the folded portion 12n It is comprised by the linear part 12o extended in the Z-axis negative direction connected to the end point on the opposite side to the linear part 12m side.

  Here, it should be noted that each folded portion constituting the feeder line 12 is folded so as to draw a smooth curve, more specifically, an arc (quadrant or semicircle) is drawn. It is a point that is folded. For this reason, a corner | angular part does not arise in each folding | turning part of the feeder 12. Therefore, a high-order mode current concentrated at the corner is generated, and the characteristics are hardly deteriorated by radiation caused by the high-order mode. Note that the setting of the radius R of the arc drawn by the feeder 12 in each folded portion will be described later with reference to another drawing.

  Next, a method for designing the feeder line 12, that is, a method for determining the width W (z) and a method for determining the return pattern will be described. Here, the arc length parameter of the curve drawn by the central axis of the feed line 12 is z, and the width of the feed line 12 at the point P (z) on the curve (the width in the direction perpendicular to the tangent line of the curve) is W ( z) (see FIGS. 2B and 2C). The design method of the feeder 12 includes the following four steps. Steps 1 and 2 are methods for determining the width W (z), and steps 3 to 4 are methods for determining a folding pattern.

  Step 1: Impedance Z (z) at each point on the feeder 12 is determined so that a desired reflection coefficient r (ω) (frequency dependence of the reflection coefficient) is obtained.

  Step 2: The width W (z) of the feeder line 12 is determined so that the impedance Z (z) at each point on the feeder line 12 becomes the value determined in Step 1.

  Step 3: The length of the straight line portion 12o constituting the end portion of the feeder line 12 is determined so as to reduce multiple reflection.

  Step 4: Determine the radius R of the folded portion (see FIG. 2C) and the number N of folded times.

  Here, the reason why Step 3 is performed before Step 4 is performed is as follows. That is, when the straight part is shortened and the folded part is brought close to the feeding point, reflection due to impedance mismatch occurring at the boundary between the external device (for example, coaxial cable) and the feeding line 12 and reflection at the folded part Multiple reflections in which are superimposed. Therefore, the length of the straight line portion 12o constituting the end portion of the feeder line 12 is secured in advance to suppress the occurrence of multiple reflections, and then the folded structure of the remaining portion of the feeder line 12 is designed.

  A method of determining the impedance Z (z) in step 1 will be described with reference to FIG. FIG. 3 is a circuit diagram showing an equivalent circuit equivalent to a line element of a microstrip line constituted by the feeder line 12 and the ground plane 13. In the figure, z represents an arc length parameter of the central axis (curve) of the feeder line 12, L (z) represents an inductance per unit length at a point P (z) on the feeder line 12, and C (Z) represents a capacitance per unit length at a point P (z) on the feeder line 12.

  The telegraph equations for voltage V and current I with time term exp (−jωt) are given by equations (1) and (2).

  From the telegraph equations (1) and (2), the Zakharov-Shabat equations (3) and (4) are derived.

  Note that variable transformations (5) and (6) were used in deriving the Zakharov-Shabat equations (3) and (4).

  When the reflection coefficient r (ω) is defined as in the equation (7), the inverse Fourier transform R (x) is given as in the equation (8). Note that r (ω) has no poles in the upper half-plane.

  Between the solution q (x) of Zakharov-Shabat equations (3) and (4) and the solution A2 (x, y) of Gel'fand-Levitan-Marchenko type integral equations (9) and (10) , (11) there is a relationship shown. Therefore, in order to obtain the solution q (x) of the Zakharov-Shabat equations (3) and (4), the integral equations (9) and (10) are solved, and from the solution A2 (x, y) to the equation (11) Q (x) may be obtained according to

  The impedance Z (x) can be obtained according to the equation (12) from q (x).

  It can be confirmed from FIG. 4 that the microstrip line constituted by the feeder line 12 and the ground plane 13 functions as a BRF. FIG. 4A is a graph showing the frequency characteristics of the VSWR value when a linear strip-shaped conductor having a uniform width is used as the feeder line 12, and FIG. It is a graph which shows the frequency characteristic of the VSWR value at the time of using the strip | belt-shaped conductor by which the width | variety shown to a) is non-uniform | heterogenous.

  When a linear strip conductor having a uniform width is used as the feeder line 12, the VSWR value is 3. over the entire microwave band (3.1 GHz to 10.6 GHz) as shown in FIG. On the other hand, when a strip-like conductor with a non-uniform width is used as a power supply line, it is 5 GHz or less, as shown in FIG. 4B, in the 5 GHz band (5.15 GHz to 5.85 GHz). The VSWR value jumps up. That is, it can be confirmed that the microstrip line composed of the feeder line 12 and the ground plane 13 functions as a BRF that reflects the 5 GHz band.

  Next, in step 4 described above, a method for setting the radius R of the arc drawn by the feeder 12 at each turn-back portion will be described with reference to FIGS. 5 and 6. FIG. 5 is a graph showing the frequency characteristics of | S11 | when R = 4 mm, R = 5 mm, and R = 6 mm. In FIG. 6, R / W is obtained by dividing R by the maximum value of the width W (z) of the feeder line 12, and the maximum value of | S11 | in the bands of 1 GHz to 5 GHz and 6 GHz to 11 GHz is R Plotting while changing.

  If R / W is made smaller than 2.5, | S11 | max sticks to a high value of −5 dB or more even in a band other than the 5 GHz band, whereas if R / W is made 2.5 or more, R It can be seen from FIG. 6 that | S11 | max gradually decreases as / W increases. That is, in order to obtain good antenna characteristics in a band other than the 5 GHz band, it is preferable that at least R / W is 2.5 or more. For example, when R = 4 mm (R / W = 2), it can be seen from FIG. 5 that peaks other than 5 GHz band are dotted with | S11 |> 5 dB.

  Note that as S / W increases, | S11 | max gradually decreases because the coupling between the linear portions constituting the feeder 12 gradually weakens and unexpected reflections that occur in the folded portion (assumed at the time of design) This is considered to be because selective reflection occurs only in the 5 GHz band as designed.

  Further, if R / W is set to 3.0 or more, | S11 | in a band other than the 5 GHz band can be made smaller than −5 dB. It can be seen from FIG. 6 that | S11 | in the band can be made smaller than −10 dB. That is, in order to obtain better antenna characteristics in a band other than the 5 GHz band, R / W is preferably 3.0 or more, and more preferably R / W is 3.5 or more.

  Finally, the effectiveness of the design using the Zakharov-Shabat equations (3) and (4) is confirmed with reference to FIG. In FIG. 7, the dotted line indicates | S11 | calculated from q (x) obtained by solving the Zakharov-Shabat equations (3) and (4) using the Runge-Kutta method, and the solid line indicates the measured | S11 | is shown. A good agreement between the calculated value (dotted line) and the measured value (solid line) can be seen from FIG.

[Structure and function of radiation element]
The structure of the radiation element 11 will be described with reference to FIG. FIG. 8 is a plan view of the radiating element 11 as viewed from above.

  As shown in FIG. 8, the radiating element 11 includes a first rectangular portion 11a, a semi-elliptical portion 11b, and a second rectangular portion 11c.

  The first rectangular portion 11a is a rectangular conductor foil having a width 2a (2a = 15 mm in the present embodiment) and a height h (h = 10 mm in the present embodiment). The semi-elliptical portion 11b divides an ellipse having a major axis radius a (a = 7.5 mm in the present embodiment) and a minor axis radius b (b = 7.5 mm in the present embodiment) into two equal parts along the major axis. The obtained semi-elliptical conductor foil has a long axis connected to the end of the first rectangular portion 11 having the width 2a. The second rectangular portion 11c interposed between the radiating element 11 and the feed line 12 is for impedance matching between the radiating element 11 and the feed line 12. In the present embodiment, the second rectangular portion 11c is used. A rectangular conductor foil having a width W ′ (W ′ = 4 mm in the present embodiment) and a height h ′ (h ′ = 2 mm in the present embodiment) is used as the portion 11c.

  FIG. 9 is a graph showing how the frequency characteristic of the VSWR value changes depending on the shape of the first rectangular portion 11a. Here, the ratio h / a is taken as a parameter that defines the shape of the first rectangular portion 11a.

  According to FIG. 9, when 1.0 ≦ h / a ≦ 1.5, the VSWR value can be suppressed to 3.5 or less over the entire microwave band (3.1 GHz to 10.8 GHz). I understand. If the width of the first rectangular portion 11a is w (= 2a), the above range can be restated as 0.5 ≦ h / w ≦ 0.75.

  FIG. 10 is a graph showing how the frequency characteristics of the VSWR value change depending on the shape of the semi-elliptical portion 11b. Here, the ratio b / a is taken as a parameter that defines the shape of the semi-elliptical portion 11b.

  According to FIG. 10, when 0.5 ≦ b / a ≦ 1.0, the VSWR value can be suppressed to 3.5 or less over the entire microwave band (3.1 GHz to 10.8 GHz). I understand.

  FIG. 11 is a graph showing how the frequency characteristic of the VSWR value changes depending on the shape of the second rectangular portion 11c. Here, the ratio w ′ / h ′ is taken as a parameter that defines the shape of the second rectangular portion.

  As can be seen from FIG. 11, when w ′ / h′≈2, the VSWR value can be suppressed to 4.0 or less over the entire microwave band (3.1 GHz to 10.6 GHz).

  In the measurement of the VSWR value shown in FIGS. 9 to 11, a linear strip-shaped conductor having a uniform width is used as the feeder line 12. However, even in the case of using a folded strip-shaped conductor having a non-uniform width shown in FIG. 2A as the feeder line 12, the VSWR value in a band other than the 5 GHz band (5.15 GHz to 5.85 GHz) is In general, this corresponds to that shown in FIGS.

[Direction of antenna]
Finally, the radiation pattern (direction dependence of the radiation gain) of the antenna 1 will be described with reference to FIG. 12A is a graph showing a radiation pattern in the XY plane at 4 GHz, and FIG. 12B is a graph showing a radiation pattern in the XY plane at 5.5 GHz. ) Is a graph showing a radiation pattern in the XY plane at 8 GHz. Comparing FIG. 12A to FIG. 12C, it can be seen that radiation is suppressed at 5.5 GHz belonging to the 5 GHz band (5.15 GHz to 5.85 GHz). It can also be seen that a good radiation pattern with low directivity is realized in other bands.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The antenna according to the present invention can be used as an antenna that can operate in a wide band but avoids interference in a part of the band. For example, while operating in a microwave band (3.1 GHz to 10.6 GHz) used for UWB (Ultra Wide Band), a 5 GHz band (used for a wireless LAN (IEEE802.11a)) ( (5.15 GHz to 5.85 GHz) interference can be used as an antenna.

DESCRIPTION OF SYMBOLS 1 Antenna 10 Dielectric substrate 11 Radiating element 11a, 11b End point of a radiating element 12 Feed line 12a End side

Claims (7)

An antenna comprising a dielectric substrate, a radiation element and a feed line formed on one main surface of the dielectric substrate, and a ground plane formed on the other main surface of the dielectric substrate,
The feeder line is a strip-like conductor having a non-uniform width folded back so that the folded portion draws a smooth curve. The feeder line and the ground plane overlap each other via the dielectric substrate, and a BRF (Band RejectFilter). The antenna is characterized in that a microstrip line functioning as a) is configured. The power supply line is folded so that the maximum value of its width is W [mm], and its central axis draws an arc of radius R [mm],
The antenna according to claim 1, wherein the ratio R / W is 2.5 or more.   The antenna according to claim 2, wherein the ratio R / W is 3.0 or more.   The antenna according to claim 3, wherein the ratio R / W is 3.5 or more.   The radiating element is formed into a bell shape composed of a rectangular portion and a semi-elliptical semi-elliptical portion, and the ratio h / w of the height h of the rectangular portion to the width w of the rectangular portion is 0. 5 or more and 0.75 or less, The antenna according to any one of claims 1 to 4.   The radiating element is formed into a bell shape including a rectangular portion and a semi-elliptical semi-elliptical portion, and the ratio b / a of the major axis a of the semi-elliptical to the minor axis b of the semi-elliptical portion. The antenna according to any one of claims 1 to 5, wherein is not less than 0.5 and not more than 1.0.   A rectangular matching portion interposed between the radiating element and the feeder line is further provided, and the ratio w ′ / h ′ of the width w ′ of the matching portion to the height h ′ of the matching portion is 2. The antenna according to any one of claims 1 to 6, wherein the antenna is provided.