JP5576951B2 - Dual frequency antenna - Google Patents

Description

  The present invention relates to a small two-frequency antenna that operates at two frequencies.

As an antenna used for in-vehicle wireless communication, there is a concern about electromagnetic radiation at the time of transmission to passengers in the vehicle cabin due to its operating principle. For this reason, antennas are often installed outside the vehicle such as a roof panel. ing. However, the antenna height of the antenna that protrudes outside the vehicle is restricted due to legal restrictions and the like, so a small antenna with a low attitude is required.
Conventionally, when an antenna that receives and transmits two desired different frequency bands is required, two resonances can be obtained by providing a choke coil between antenna elements, or two independent antennas can be used. Two outputs of frequency were obtained, or two outputs of two frequencies were synthesized to obtain an output.

US Patent Publication No. 2006/0071858 Japanese Patent Application Laid-Open No. 2004-282329 US Patent Publication No. 2006/0158383 US Pat. No. 6,377,227

In the conventional dual-frequency antenna, a choke coil is required when a single antenna is used. However, when the choke coil is used, there is a problem that the low-frequency side resonance band becomes narrow due to the influence of the choke coil.
Therefore, an object of the present invention is to provide a dual-frequency antenna that can operate in two different frequency bands without the need for a choke coil.

  In order to achieve the above object, a dual-frequency antenna according to the present invention is formed in a planar shape from a substantially flat ground, an insulating substrate standing on the ground, and from the lower end to the upper portion of the substrate. Formed in the upper portion of the substrate that does not overlap the first element, a through-hole disposed near the lower end of the first element, and a power supply portion for supplying power to the lower end of the first element. And a power supply line that is led out from the through hole and supplies power to the second element.

  In the dual-frequency antenna of the present invention, the first element operates on the high frequency side of two different frequency bands, the second element operates on the low frequency side, and the power supply line for supplying power to the second element is Since it functions as an inductance, a choke coil can be dispensed with. Further, if the first element and the second element are configured by a print pattern, matching can be made possible by the shape of the print pattern.

It is a front view which shows the structure of the dual frequency antenna concerning the Example of this invention. It is a rear view which shows the structure of the 2 frequency antenna concerning the Example of this invention. It is a Smith chart which shows the frequency characteristic of the impedance of the 2 frequency antenna concerning this invention. It is a figure which shows the frequency characteristic of VSWR of the 2 frequency antenna concerning this invention. It is a figure which shows the directional characteristic in the horizontal plane of each frequency of the AMPS band and PCS band when the elevation angle of the dual-frequency antenna according to the present invention is 0 °. It is a figure which shows the directional characteristics in the horizontal surface of each frequency of an AMPS band and PCS band when the elevation angle of the dual-frequency antenna according to the present invention is 10 °. It is a figure which shows the directional characteristic in the horizontal plane of each frequency of the AMPS band and PCS band when the elevation angle of the dual-frequency antenna according to the present invention is 20 °. It is a figure which shows the directional characteristic in the horizontal surface of each frequency of an AMPS zone | band and a PCS zone | band when the elevation angle of the 2 frequency antenna concerning this invention is 30 degrees.

1 and 2 show the configuration of a dual-frequency antenna 1 that operates in two different frequency bands according to an embodiment of the present invention. FIG. 1 is a front view showing the configuration of the dual frequency antenna 1, and FIG. 2 is a rear view showing the configuration of the dual frequency antenna 1.
As shown in these drawings, the dual-frequency antenna 1 includes a first element 11 and a second element 21 formed as printed patterns on the front and back surfaces of an insulating printed board 10 such as a glass epoxy board. . The printed circuit board 10 has an elongated rectangular shape with a height H and a width W, and is erected almost vertically on a planar ground 14. The first element 11 is formed as a planar printed pattern having a width W and a length L1 from the lower end of the surface of the printed circuit board 10. The lower portion of the first element 11 is formed with a tapered portion 11b toward the lower end. The width is gradually narrowed to adjust the impedance. In addition, a slit 11a having a width S from the substantially center of the upper edge of the first element 11 is formed downward. The first element 11 is fed from the lower end, and a feeding point 13 is provided at the lower end. In addition, a through hole 12 that is electrically connected to the back surface is provided at substantially the center of the printed circuit board 10 at a position at a height L3 from the lower end of the printed circuit board 10 that is the feeding point 13.

  The second element 21 is formed as a planar print pattern having a width W and a length L2 from the upper end of the back surface of the printed circuit board 10, and both sides of the second element 21 are folded downward. The second element 21 is formed on the printed circuit board 10 that does not overlap the first element 11 formed on the surface of the printed circuit board 10. A power supply line 21a having a narrowed width D is drawn out from substantially the center of the second element 21, and the folded portions on both sides of the second element 21 function as top loading. The power supply line 21a also functions as an antenna, is formed substantially vertically from the lower end of the printed circuit board 10 to the position of the height L3, and the lower end of the power supply line 21a is electrically connected to the through hole 12. Since the feeder line 21a is formed in an elongated shape, the impedance component of the feeder line 21a with respect to the low-frequency signal component of the two frequencies is increased by the inductance component generated in the feeder line 21a, and the low-frequency signal component is fed. It becomes difficult to transmit on the line 21a. Thus, since the power supply line 21a acts equivalently as a choke coil, the low-frequency signal component transmitted from the power supply point 13 through the first element 11 and the through hole 12 through the power supply line 21a is the second. Power is supplied to the element 21. The low-frequency received signal of the second element 21 is combined with the high-frequency received signal of the first element 11 via the power supply line 21 a and the through hole 12 and output from the power supply point 13. The width S of the slit 11a in the first element 11 is wider than the width D of the power supply line 21a so that the power supply line 21a is positioned in the slit 11a. As a result, electrical coupling with 21a is prevented as much as possible.

  The dual-frequency antenna 1 is connected to two different frequency bands of AMPS (Advanced Mobile Phone Service) band of 824 to 894 MHz and PCS (Personal Communication Services) band of 1850 to 1990 MHz, or GSM (registered trademark) of 880 to 960 MHz. ) (Global System for Mobile Communications) It can be operated in two different frequency bands, 900 band and 1710-1880 MHz GSM1800 band. An example of the dimensions of the dual-frequency antenna 1 at this time is shown below. First, the width W of the printed circuit board 10 is about 15 mm, the height H is about 50 mm, the thickness is about 1.6 mm, and the relative dielectric constant εr is about 4.6. The length L1 of the first element 11 operating on the high frequency side (PCS / GMS1800) of the two frequencies is about 34.5 mm, and when the wavelength of 1850 MHz is λ1, it is expressed as about 0.21λ1, and the width of the slit 11a S is about 2 mm. The length L2 of the second element 21 operating on the low frequency side (AMPS / GMS900) of the two frequencies is about 15 mm, and the wavelength of the frequency of 824 MHz is represented by about 0.04λ2, The height L3 is about 10 mm and is expressed as about 0.06λ1 or about 0.03λ2.

  Next, FIG. 3 shows a Smith chart showing the frequency characteristics of the impedance of the two-frequency antenna 1 having the above dimensions. Referring to FIG. 3, the resistance is about 25.8Ω and the reactance is about −21.5Ω at the low frequency 824 MHz, and the resistance is about 48.9Ω and the reactance is about 41.4Ω at the frequency 894 MHz. Become. Further, the resistance is about 62.8Ω and the reactance is about 0.1Ω at a frequency of 1850 MHz on the high frequency side, and the resistance is about 74.2Ω and the reactance is about −7.6Ω at a frequency of 1990 MHz. Thus, a better impedance characteristic is shown on the high frequency side.

  Next, the frequency characteristic of the voltage standing wave ratio (VSWR) of the dual-frequency antenna 1 having the above dimensions is shown in FIG. Referring to FIG. 4, about 2.41 is obtained as VSWR at a frequency of 824 MHz on the low frequency side, and about 2.27 is obtained as VSWR at a frequency of 894 MHz, which is the best in the frequency band on the low frequency side of 824 to 894 MHz. As a VSWR, about 1.5 is obtained. Further, about 1.26 is obtained as the VSWR at the frequency of 1850 MHz on the high frequency side, about 1.51 is obtained as the VSWR at the frequency of 1990 MHz, and 1 as the best VSWR in the frequency band on the high frequency side of 1850 to 1990 MHz. .26 is obtained. Thus, a better VSWR characteristic is exhibited on the high frequency side. In general, the VSWR is required to be about 2.5 or less, but in the example shown in FIG. 4, the maximum VSWR in the AMPS band is about 2.4 (840 MHz), and the maximum VSWR in the PCS band is about 1 .5 (1990 MHz), and good VSWR characteristics are obtained at two frequencies. Note that the VSWR can be set to a better value by adding a matching circuit to supply power to the power supply point 13.

Next, the directivity characteristics in the horizontal plane at each frequency of the dual-frequency antenna 1 according to the present invention are shown in FIGS. In this case, the dimensions of the dual-frequency antenna 1 are as described above, and the dual-frequency antenna 1 is erected approximately at the center of the ground 14 having a circular shape with a diameter of about 1 m, so that the polarization is vertical polarization ing.
FIG. 5 shows horizontal plane directivity characteristics when the elevation angle is 0 ° at each frequency of the AMPS band and PCS band according to the dual-frequency antenna 1 of the present invention. Referring to FIG. 5, at 824 MHz, which is the lower limit frequency of the transmission band in the AMPS band, the maximum gain is about −1.7 dBi, the minimum gain is about −2.2 dBi, and the average gain is about −2.0 dBi. Is about 0.6 dB, which is a good directional characteristic with almost no directivity. At 849 MHz, which is the upper limit frequency of the transmission band in the AMPS band, the maximum gain is about -0.8 dBi, the minimum gain is about -1.5 dBi, the average gain is about -1.2 dBi, and the ripple is about 0.1. The directivity characteristic is 7 dB, almost omnidirectional, and the gain is slightly improved. Furthermore, at 869 MHz, which is the lower limit frequency of the reception band in the AMPS band, the maximum gain is about -1.0 dBi, the minimum gain is about -1.7 dBi, the average gain is about -1.4 dBi, and the ripple is about 0.1. The directional characteristic is 8 dB, which is almost non-directional. Furthermore, at 894 MHz, which is the upper limit frequency of the reception band in the AMPS band, the maximum gain is about -1.4 dBi, the minimum gain is about -2.3 dBi, the average gain is -1.8 dBi, and the ripple is about 1. The directivity characteristic is almost zero omnidirectional with 0 dB.

  Referring to FIG. 5, in the PCS band when the elevation angle is set to 0 °, the maximum gain is about 0.5 dBi and the minimum gain is about −0.9 dBi at the lower limit frequency of the transmission band of 1850 MHz. The gain is about -0.2 dBi and the ripple is about 1.4 dB, and the omnidirectional good directivity characteristics are obtained, and a high gain is obtained. In addition, at 1910 MHz which is the upper limit frequency of the transmission band in the PCS band, the maximum gain is about 1.0 dBi, the minimum gain is about -0.5 dBi, the average gain is about 0.2 dBi, and the ripple is about 1.5 dB. The directivity characteristics are almost omnidirectional, and a higher gain is obtained. Further, at 1930 MHz, which is the lower limit frequency of the reception band in the PCS band, the maximum gain is about 1.2 dBi, the minimum gain is about −0.3 dBi, the average gain is about 0.5 dBi, and the ripple is about 1.5 dB. The directivity characteristics are almost omnidirectional, and a higher gain is obtained. Furthermore, at 1990 MHz, which is the upper limit frequency of the reception band in the PCS band, the maximum gain is about 0.3 dBi, the minimum gain is about -1.0 dBi, the average gain is about -0.3 dBi, and the ripple is about 1. The directional characteristics are good with a 3 dB almost non-directional characteristic, and a high gain is obtained.

  FIG. 6 shows horizontal plane directivity characteristics when the elevation angle is 10 ° at each frequency of the AMPS band and PCS band according to the dual-frequency antenna 1 of the present invention. Referring to FIG. 6, at 824 MHz, which is the lower limit frequency of the transmission band in the AMPS band, the maximum gain is about 0.2 dBi, the minimum gain is about −0.4 dBi, the average gain is about −0.2 dBi, and the ripple is The gain is improved with a directional characteristic of about 0.6 dB and almost no directivity. Further, at 849 MHz which is the upper limit frequency of the transmission band in the AMPS band, the maximum gain is about 1.0 dBi, the minimum gain is about 0.5 dBi, the average gain is about 0.7 dBi, and the ripple is about 0.5 dB. The directional characteristics are good with no directivity, and the gain is further improved. Furthermore, at 869 MHz, which is the lower limit frequency of the reception band in the AMPS band, the maximum gain is about 1.0 dBi, the minimum gain is about 0.4 dBi, the average gain is about 0.8 dBi, and the ripple is about 0.6 dB. It is considered to have good omnidirectional directivity characteristics. Furthermore, at 894 MHz, which is the upper limit frequency of the reception band in the AMPS band, the maximum gain is about 1.0 dBi, the minimum gain is about 0.2 dBi, the average gain is 0.7 dBi, and the ripple is about 0.7 dB. It is considered to have good omnidirectional directivity characteristics.

  Referring to FIG. 6, in the PCS band when the elevation angle is 10 °, the maximum gain is about 4.5 dBi and the minimum gain is about 3.4 dBi at 1850 MHz, which is the lower limit frequency of the transmission band. Is about 3.9 dBi and the ripple is about 1.1 dB, and the omnidirectional good directivity characteristic is obtained, and a high gain is obtained. In addition, at 1910 MHz which is the upper limit frequency of the transmission band in the PCS band, the maximum gain is about 4.4 dBi, the minimum gain is about 3.4 dBi, the average gain is about 3.9 dBi, and the ripple is about 1.1 dB. The directional characteristics are good with omnidirectionality, and high gain is maintained. Further, at 1930 MHz, which is the lower limit frequency of the reception band in the PCS band, the maximum gain is about 4.6 dBi, the minimum gain is about 3.5 dBi, the average gain is about 4.1 dBi, and the ripple is about 1.1 dB. The directional characteristics are excellent in omnidirectionality, and a higher gain is obtained. Furthermore, in 1990 MHz which is the upper limit frequency of the reception band in the PCS band, the maximum gain is about 3.6 dBi, the minimum gain is about 2.6 dBi, the average gain is about 3.1 dBi, and the ripple is about 1.0 dB. The directivity characteristics are almost omnidirectional, and a high gain is obtained.

  FIG. 7 shows the horizontal plane directivity when the elevation angle is 20 ° at each frequency of the AMPS band and PCS band according to the dual-frequency antenna 1 of the present invention. Referring to FIG. 7, at 824 MHz, which is the lower limit frequency of the transmission band in the AMPS band, the maximum gain is about 1.8 dBi, the minimum gain is about 1.4 dBi, the average gain is about 1.7 dBi, and the ripple is about 0. .4 dB, almost omnidirectional and good directivity, and high gain is obtained. At 849 MHz, which is the upper limit frequency of the transmission band in the AMPS band, the maximum gain is about 2.6 dBi, the minimum gain is about 2.2 dBi, the average gain is about 2.4 dBi, and the ripple is about 0.5 dB. The directional characteristics are good with no directivity, and the gain is further improved. Further, at 869 MHz, which is the lower limit frequency of the reception band in the AMPS band, the maximum gain is about 3.1 dBi, the minimum gain is about 2.7 dBi, the average gain is about 2.9 dBi, and the ripple is about 0.4 dB. The directional characteristics are good with no directivity, and the gain is further improved. Further, at 894 MHz, which is the upper limit frequency of the reception band in the AMPS band, the maximum gain is about 3.0 dBi, the minimum gain is about 2.6 dBi, the average gain is 2.8 dBi, and the ripple is about 0.4 dB. It has good omnidirectional directivity characteristics and high gain is obtained.

  Referring to FIG. 7, in the PCS band when the elevation angle is 20 °, the maximum gain is about 6.6 dBi and the minimum gain is about 5.8 dBi at the lower limit frequency of the transmission band of 1850 MHz, and the average gain Is about 6.1 dBi and the ripple is about 0.8 dB, and the omnidirectional characteristics are good, and high gain is obtained. At 1910 MHz, which is the upper limit frequency of the transmission band in the PCS band, the maximum gain is about 6.6 dBi, the minimum gain is about 5.7 dBi, the average gain is about 6.2 dBi, and the ripple is about 0.9 dB. The directional characteristics are good with omnidirectionality, and high gain is maintained. Further, at 1930 MHz, which is the lower limit frequency of the reception band in the PCS band, the maximum gain is about 6.7 dBi, the minimum gain is about 5.7 dBi, the average gain is about 6.3 dBi, and the ripple is about 1.0 dB. The directional characteristics are excellent in omnidirectionality, and a higher gain is obtained. Furthermore, in 1990 MHz which is the upper limit frequency of the reception band in the PCS band, the maximum gain is about 5.7 dBi, the minimum gain is about 5.0 dBi, the average gain is about 5.4 dBi, and the ripple is about 0.7 dB. The directivity characteristics are almost omnidirectional, and a high gain is obtained.

  FIG. 8 shows the horizontal plane directivity when the elevation angle is set to 30 ° at each frequency of the AMPS band and the PCS band according to the dual-frequency antenna 1 of the present invention. Referring to FIG. 8, at 824 MHz, which is the lower limit frequency of the transmission band in the AMPS band, the maximum gain is about 2.9 dBi, the minimum gain is about 2.5 dBi, the average gain is about 2.7 dBi, and the ripple is about 0. .3 dB of almost omnidirectional good directivity characteristics, and high gain is obtained. Further, at 849 MHz which is the upper limit frequency of the transmission band in the AMPS band, the maximum gain is about 3.4 dBi, the minimum gain is about 3.0 dBi, the average gain is about 3.2 dBi, and the ripple is about 0.4 dB. The directional characteristics are good with no directivity, and the gain is further improved. Furthermore, at 869 MHz, which is the lower limit frequency of the reception band in the AMPS band, the maximum gain is about 4.0 dBi, the minimum gain is about 3.5 dBi, the average gain is about 3.8 dBi, and the ripple is about 0.5 dB. The directional characteristics are good with no directivity, and the gain is further improved. Furthermore, in the 894 MHz which is the upper limit frequency of the reception band in the AMPS band, the maximum gain is about 3.9 dBi, the minimum gain is about 3.5 dBi, the average gain is 3.8 dBi, and the ripple is about 0.5 dB. It has good omnidirectional directivity characteristics and high gain is obtained.

  Referring to FIG. 8, in the PCS band when the elevation angle is 30 °, the maximum gain is about 5.1 dBi and the minimum gain is about 3.5 dBi at the lower limit frequency of the transmission band of 1850 MHz, and the average gain is Is approximately 4.5 dBi, and the ripple is approximately 1.7 dB. In addition, at 1910 MHz which is the upper limit frequency of the transmission band in the PCS band, the maximum gain is about 5.5 dBi, the minimum gain is about 3.9 dBi, the average gain is about 4.9 dBi, and the ripple is about 1.7 dB. The directional characteristics are good with omnidirectionality, and high gain is maintained. Furthermore, at 1930 MHz which is the lower limit frequency of the reception band in the PCS band, the maximum gain is about 5.7 dBi, the minimum gain is about 4.2 dBi, the average gain is about 5.1 dBi, and the ripple is about 1.5 dB. It has good omnidirectional directivity characteristics and higher gain. Furthermore, in 1990 MHz which is the upper limit frequency of the reception band in the PCS band, the maximum gain is about 4.8 dBi, the minimum gain is about 3.5 dBi, the average gain is about 4.3 dBi, and the ripple is about 1.3 dB. The directivity characteristics are almost omnidirectional, and a high gain is obtained.

  As described above, the dual-frequency antenna 1 of the present invention operates in two different frequency bands, the AMPS band and the PCS band, and can obtain almost omnidirectional directional characteristics even when the elevation angle is 0 ° to 30 °. become able to. Moreover, the gain in the two different frequency bands of the AMPS band and the PCS band of the dual frequency antenna 1 according to the present invention shows a tendency that the gain of the high frequency PCS band is high. In this case, since the gain of the dipole antenna is 2.15 dBi, gain greatly exceeding the gain of the dipole antenna is obtained in two different frequency bands depending on the elevation angle. Further, even if the two different frequency bands are GSM900 / GSM1800 bands, the two-frequency antenna 1 of the present invention can obtain the same electrical characteristics as described above. Therefore, the dual-frequency antenna 1 of the present invention can be an antenna that can sufficiently operate in two different frequency bands. When two different frequency bands to be operated are different bands from the 900 MHz band or the 1800 MHz band, the two desired frequency bands can be changed by changing the dimensions of the first element 11 or the second element 21 according to the band. The dual-frequency antenna 1 of the present invention can be operated in different frequency bands. Further, the dual-frequency antenna 1 according to the present invention can be a small and low-profile antenna having a height of about 50 mm and a width of about 15 mm, and the first element 11 and the second element depending on the printed pattern of the printed circuit board 10. Therefore, it is possible to provide an inexpensive dual-frequency antenna with a simple configuration.

In the dual-frequency antenna 1 according to the present invention described above, the feeder line 21a that feeds power to the second element 21 may have a meander shape so that the antenna height of the dual-frequency antenna 1 can be further suppressed. Further, when the dual frequency antenna 1 of the present invention is mounted on a vehicle, the dual frequency antenna 1 is fixed on the antenna base attached to the vehicle, and a radome with a resin cover covering the dual frequency antenna 1 is attached to the antenna base. Is preferred.
Furthermore, in the dual-frequency antenna 1 of the present invention, two different frequency bands are matched by the pattern shape of the first element 11 formed on the front surface of the printed circuit board 10 and the second element 21 formed on the back surface. Therefore, the two-frequency antenna 1 can be reduced in size and cost. Therefore, it is easy to combine with an AM / FM broadcast receiving antenna, a GPS signal receiving antenna, a terrestrial digital broadcast receiving antenna, a DAB (Digital Audio Broadcast) receiving antenna, an SDARS (Satellite Digital Audio Radio) receiving antenna, and the like. Can do.

DESCRIPTION OF SYMBOLS 1 2 frequency antenna 10 Printed circuit board 11 1st element 11a Slit 11b Tapered part 12 Through hole 13 Feeding point 14 Ground 21 2nd element 21a Feeding line

Claims (4)

A two-frequency antenna operating at two frequencies,
A ground on a substantially plane,
An insulating substrate standing on the ground;
A first element formed in a planar shape from the lower end to the upper part of the substrate;
A power feeding unit for feeding power to the lower end of the first element;
A through hole disposed in the vicinity of the lower end of the first element;
A second element formed on an upper portion of the substrate that does not overlap the first element;
A power supply line that is derived from the through hole and supplies power to the second element;
A dual-frequency antenna comprising:   2. The dual-frequency antenna according to claim 1, wherein a tapered portion is formed from the middle of the first element toward the lower end.   2. The dual-frequency antenna according to claim 1, wherein both sides of the second element are shaped to be folded downward from a portion where a feed line of the second element is led out, and the feed line is the second element. A two-frequency antenna characterized by being pulled out from approximately the center of the antenna.   2. The dual-frequency antenna according to claim 1, wherein the first element and the second element are configured by a printed pattern formed on the substrate.