JP2007235832A - Planar loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar loop antenna to be configured by a print circuit board which is laminated a conductive plate on a surface of a substrate, and having a large bandwidth in a reception frequency. <P>SOLUTION: The conductive plate 2 is formed to be roughly rectangular in outline, and is made to be a loop shape by forming an opening 3 having a roughly rectangular shape at the center portion of the conductive plate 2. A notch portion 4 for making the conductive plate 2 having the loop shape discontinued is provided at a lower side, and the opening 3 is communicated with a lower end of the outline. One of opposing positions pinching the notch portion 4 is made as a feeding point. Width of the conductive plate 2 is made not to be larger than 2/3 of a wave length. Width of the opening 3 at the center portion of the conductive plate 2 is made not to be larger than 2/3 of outline width of the conductive plate 2. Width of the notch portion 4 is made not to be larger than 1/5 of outline width of the conductive plate 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a planar loop antenna having a wide bandwidth regardless of its small size.

  The loop antenna is formed by rounding a wire into a circular ring shape or a quadrangular ring shape and connecting it to a receiver. If the length of one round is the same, the performance as an antenna is the same regardless of whether the shape is circular, square, or triangular. The loop antenna exhibits power when tuned to the target radio wave, and the sensitivity is greatly improved when the loop antenna and the variable capacitor are tuned to the frequency of the target radio wave.

  The number of windings of the loop is closely related to the frequency coverage, and if the number of windings is excessive, the frequency decreases and the high frequency region cannot be covered. In addition, when the number of turns is small, the frequency shifts to a higher frequency and the low frequency region cannot be covered. When the shape is made larger, the number of turns is reduced, and when the shape is made smaller, the number of turns is increased.

  In this way, the loop antenna can be made by winding a wire, so it is easy to make. However, when receiving a weak radio wave with directivity, it is necessary to turn the loop antenna to find an appropriate direction. It becomes.

  "Wideband antenna element and wideband indoor antenna" according to Japanese Patent Application Laid-Open No. 2005-45331 is an antenna element that receives radio waves having a frequency over a wide band with a simple structure, and a conductive conductor plate formed in a quadrilateral shape; A cutout hole formed of an opening having a shape in which the distance between the edge portions facing each other located at substantially the center of the conductor plate gradually increases or decreases, and opens to be connected to the cutout hole and reaches one side of the conductor plate. And a pair of feeding points provided in the vicinity of the communicating hole, and the radio wave received by the conductor plate can be fed as an electrical signal to the feeding point.

  A “slot antenna” according to Japanese Patent Application Laid-Open No. 11-186836 is a slot antenna that opens a straight slot in a conductor plate and feeds power to the conductor plate by a feed line, and uses a T-shaped slot shape to feed power. Is λ / 4, the vertical dimension of the T-shaped slot is approximately λ / 4, and the horizontal dimension is approximately λ / 2. Therefore, it can be made smaller and smaller than the conventional one having a cross-shaped slot.

The basic form of these antennas is a loop antenna, and a conductor plate is used instead of a wire loop. By using the conductor plate, the reception area can be expanded to receive radio waves having a frequency over a wide band, and the shape can be reduced. The frequency of terrestrial digital broadcasting, which will become the mainstream in the future, has a large bandwidth of 470 MHz to 770 MHz, and it must be an antenna capable of receiving these.
"Broadband antenna element and broadband indoor antenna" according to JP-A-2005-45331 "Slot antenna" according to Japanese Patent Laid-Open No. 11-186836

  As described above, a loop antenna using a conductive plate can receive a radio wave having a frequency over a wide band while being small in size, but an antenna having a wider band VSWR characteristic is required. The present invention provides a broadband planar loop antenna having a wide bandwidth of VSWR 2 or less, a small size, a low manufacturing cost, and a simple structure.

  The broadband planar loop antenna according to the present invention comprises a printed circuit board by laminating a substantially rectangular conductor plate on one surface of the substrate, the conductor plate having a wide loop shape, and an opening at the center of the conductor plate. is doing. Similarly, the opening has a substantially rectangular shape, a discontinuous structure in which a part of the loop-shaped conductor plate is cut out, and a feeding point is provided in the cutout portion. Here, the opening can form a hole opened together with the substrate, and the notch is provided below or above the opening. On the other hand, it may be composed only of a conductor plate without being laminated on the substrate.

  By the way, in the present invention, in order to increase the bandwidth of the reception frequency, the outer width of the conductor plate is 2/3 or less of the wavelength, and the width of the opening without the conductor plate in the central portion of the printed circuit board is the width of the conductor plate. 2/3 or less, and the width of the notch that is a discontinuous portion is 1/5 or less of the outer width of the conductor plate. And it is set as the structure which bonded another board | substrate on the conductor board side of the printed circuit board which stuck the conductor board on the one surface of the said board | substrate, ie, sandwiched the conductor board between two board | substrates. You can also

  The planar loop antenna according to the present invention has a structure in which a conductor plate is attached to a substrate in a loop shape, and the frequency bandwidth that can be received is wider than a basic loop antenna having a wire loop shape. In the present invention, the width of the conductor plate is 2/3 or less of the wavelength, the width of the opening at the center of the printed circuit board without the conductor plate is 2/3 or less of the width of the conductor plate, and By setting the width to 1/5 or less of the outer width of the conductor plate, the bandwidth of the frequency that can be received is further increased.

  FIG. 1 is an embodiment showing a broadband planar loop antenna according to the present invention. In the figure, 1 denotes a substrate, 2 denotes a conductor plate, and the substrate 1 is generally a resin plate, and the conductor plate 2 is a metal plate having good conductivity, such as a copper plate, a brass plate, an aluminum plate, a steel plate. A board or the like is used. The conductor plate 2 is attached to the surface of a square resin substrate 1. Here, there are various methods of attaching the conductor plate 2, and it can be fixed or pinned with an adhesive. Further, instead of sticking, the substrate 1 may be plated with a loop-shaped conductor plate 2 or the central opening 3 and the cutout 4 of the plated rectangular conductor plate may be etched.

  By the way, the conductor plate 2 has a loop shape, a rectangular opening 3 is formed in the center portion, and a part of the conductor plate 2 is cut out to have a cutout portion 4. It communicates with the opening 3. The conductor plate 2 is also rectangular in shape but smaller than the substrate 1. However, the outer shape of the conductor plate 2 and the outer shape of the substrate 1 may be a rectangle having the same size.

  FIG. 2 shows a conductor plate 2 having a notch 4. This figure shows the dimensions of each part of the conductor plate 2. The conductor plate 2 has a rectangular outer shape, and has a small rectangular opening 3 at the center, and the notch 4 has an opening 3 and an outer shape. Are connected. Here, L is the outer width of the conductor plate 2, M is the width of the opening 3 of the conductor plate 2, d is the width of the notch 4, r is the width of the conductor plate 2, and h is from the lower edge 5. The power feeding positions are respectively shown.

  FIG. 3 shows a contour line of a specific band (%) when the impedance is 75Ω. The horizontal axis represents the notch width dimension d with respect to the outer width dimension L, and the vertical axis represents the opening width dimension M with respect to the outer width dimension L. As is clear from the figure, the region with the feeding width d / L around 0.1 and the inner diameter M / L around 0.45 has the highest specific bandwidth. In particular, the position of the black mark in the figure is the highest specific bandwidth. That is, at this position, if the feed width d / L is 0.1 and the opening width M / L is 0.5, the specific bandwidth is 105.68%.

  FIG. 4 shows a specific conductor plate of the planar loop antenna of the present invention. The outer width L = 200 mm, the opening width M = 100 mm, the notch width d = 10 mm, and The height of the outer shape is 200 mm, and the width dimension r of the conductor plate is 50 mm.

  FIG. 5 shows the VSWR characteristics of the planar loop antenna provided with the conductor plate of FIG. 4. As is apparent from FIG. 5, the frequency of VSWR <2 is 430 MHz to 1030 MHz. That is, the planar loop antenna of FIG. 4 can receive frequencies in this band. Therefore, this specific bandwidth is 82.2%, which provides a sufficient required bandwidth.

  6 represents the radiation directivity in the XY plane, and FIG. 7 represents the radiation directivity in the XZ plane. Here, the direction of the conductor plate 2 shown in FIG. 4, that is, the surface on which the planar loop antenna is installed is YZ. FIGS. 6 and 7 show the radiation directivity in the XY plane and the radiation directivity in the XZ plane when a planar loop antenna is installed on the YZ plane, respectively.

  FIG. 8 shows another specific conductor plate of the planar loop antenna of the present invention. The outer width L = 200 mm, the opening width M = 100 mm, and the notch width d = 10 mm. The height of the outer shape is 160 mm and the width r of the conductor plate is 50 mm.

  FIG. 9 shows the VSWR characteristics of the planar loop antenna provided with the conductor plate 2 shown in FIG. 8. As is clear from the figure, the frequency of VSWR <2 is 420 MHz to 1050 MHz. That is, the planar loop antenna of FIG. 8 can receive frequencies in this band. Therefore, this specific bandwidth is 85.71%, which provides a sufficient required bandwidth.

  FIG. 10 shows the radiation directivity in the XY plane, and FIG. 11 shows the radiation directivity in the XZ plane. Here, the direction of the conductor plate 2 shown in FIG. 8, that is, the surface on which the planar loop antenna is installed is YZ. FIGS. 10 and 11 show the radiation directivity in the XY plane and the radiation directivity in the XZ plane when a planar loop antenna is installed on the YZ plane, respectively.

  FIG. 12 shows a planar loop antenna configured by sandwiching a conductor plate 2 between both substrates 1 and 1. By sandwiching the conductor plate 2 between the substrates 1 and 1, the conductor plate 2 can be prevented from being corroded without being exposed to wind and rain, and the performance as an antenna is not deteriorated.

1 shows an embodiment of a planar loop antenna according to the present invention. A conductor plate constituting a planar loop antenna. The contour line of the specific band (%) of the planar loop antenna is shown. The specific example of the conductor board which comprises the planar loop antenna of this invention. The VSWR characteristic of the planar loop antenna provided with the conductor plate of FIG. FIG. 4 shows radiation directivity in the XY plane of a planar loop antenna in which the conductor plate of FIG. 4 is in the YZ plane. FIG. 4 shows radiation directivity in the XZ plane of a planar loop antenna in which the conductor plate of FIG. 4 is in the YZ plane. The specific example of the conductor board which comprises the planar loop antenna of invention. The VSWR characteristic of the planar loop antenna provided with the conductor plate of FIG. 8 shows radiation directivity in the XY plane of a planar loop antenna in which the conductor plate in FIG. 8 is in the YZ plane. Eight conductor plates represent radiation directivities in the XZ plane of a planar loop antenna having the YZ plane. The other specific example of the conductor board which comprises the planar loop antenna of this invention.

Explanation of symbols

1 Substrate 2 Conductor plate 3 Opening 4 Notch 5 Lower edge

Claims (6)

In a planar loop antenna constituted by a printed circuit board provided by laminating a conductor plate on one surface of the substrate, the conductor plate has a substantially rectangular outer shape, and a substantially rectangular opening is formed in the central portion of the conductor plate. Therefore, a notch for discontinuous loop-shaped conductor plate is provided on the lower side, the opening and the lower edge of the outer shape are communicated, and the opposite position with the notch is sandwiched as the feeding point Further, the width of the conductor plate is 2/3 or less of the wavelength, the width of the central opening of the conductor plate is 2/3 or less of the outer width of the conductor plate, and the width of the notch is equal to the outer width of the conductor plate. A planar loop antenna characterized by being 1/5 or less. In a planar loop antenna constituted by a printed circuit board provided by laminating a conductor plate on one surface of the substrate, the conductor plate has a substantially rectangular outer shape, and a substantially rectangular opening is formed in the central portion of the conductor plate. By forming a loop shape, a notch for discontinuous loop-shaped conductor plate is provided on the upper side, the opening and the upper edge of the outer shape are communicated, and the opposite position sandwiching the notch is a feeding point, Further, the width of the conductor plate is 2/3 or less of the wavelength, the width of the central opening of the conductor plate is 2/3 or less of the outer width of the conductor plate, and the width of the notch is 1 of the outer width of the conductor plate. A flat loop antenna characterized by being / 5 or less. The planar loop antenna according to claim 1, wherein another substrate is bonded to the conductor plate, and the conductor plate is sandwiched between the two substrates. The planar loop antenna according to claim 1, wherein a surface of the conductor plate is coated. In a planar loop antenna having a conductor plate, the conductor plate has a substantially rectangular outer shape, and a substantially rectangular opening is formed at the center of the conductor plate to form a loop shape. A notch portion is formed on the lower side to make it continuous, the opening and the lower edge of the outer shape communicate with each other, and the opposing position with the notch portion sandwiched between is a feeding point, and the width of the conductor plate is 2/3 of the wavelength. A planar loop characterized in that the width of the opening at the center of the conductor plate is 2/3 or less of the outer width of the conductor plate and the width of the notch is 1/5 or less of the outer width of the conductor plate. antenna. In a planar loop antenna having a conductor plate, the conductor plate has a substantially rectangular outer shape, and a substantially rectangular opening is formed at the center of the conductor plate to form a loop shape. A notch for continuous connection is provided on the upper side so that the opening and the upper edge of the outer shape communicate with each other, and the opposite position across the notch is used as a feeding point, and the width of the conductor plate is 2/3 or less of the wavelength. A planar loop antenna characterized in that the width of the opening at the center of the conductor plate is 2/3 or less of the outer width of the conductor plate, and the width of the notch is 1/5 or less of the outer width of the conductor plate. .