JP2005333555A - Multiband compatible circularly-polarized microstrip antenna and radio system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiband compatible circularly-polarized microstrip antenna technology that is compatible with multifrequencies using one feeding point and is easy to be connected with an RF circuit and further can realize good transmission efficiency and good reception efficiency. <P>SOLUTION: The antenna includes a radiating element 16 in which a feeding element 12 and a nonfeeding element 14 that have the feeding point 13 on a dielectric 10 are arranged and these elements 12, 14 are connected by a switch 15. When a side of the feeding element 12 is L/W in length, a distance between a side W and the feeding point 13 is Li, a distance between a side L and the feeding point 13 is Wi, a side corresponding to the side L among sides of the radiating element 16 is L' in length, a side corresponding to the side W among the sides thereof is W' in length, a distance between the side W' and the feeding point 13 is Li', and a distance between the side L' and the feeding point 13 is Wi', defined are L/W= L'/W', Li/L= Li'/ L', and Wi/W= Wi'/ W'. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multiband-compatible circularly polarized antenna technology, and more particularly to a multiband capable of supporting multiple frequencies at a single feeding point, easily connecting to an RF circuit, and realizing good transmission efficiency and reception efficiency. The present invention relates to a corresponding circularly polarized microstrip antenna and a radio system using the same.

  Currently, mobile phones are second-generation mobile phones such as PDC (Personal Digital Celluler), FOMA, CDMA2000, PHS (Personal Handyphone System), and wireless LANs are IEEE802.11a, 802.11b, 802.11g, Bluetooth, etc., ITS (Intelligent Transport Systems (GPS) uses multiple frequencies corresponding to wireless standards such as GPS (Global Positioning System), VICS (Vehicle Information Communication System), ETC (Electronic Toll Collection System), etc., and multiple frequencies will coexist in the future. The environment is expected to continue.

  However, since a single-frequency antenna is used in conventional wireless communication, a wireless device corresponding to a plurality of frequencies needs to be provided with a plurality of single-frequency antennas, which is increased in size.

  In addition, the area where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited, and there is a limit to installing all antennas in a favorable radio wave environment. Therefore, in recent years, multi-frequency (multi-band) compatible antennas that can handle a plurality of frequencies with one antenna have attracted attention.

  As a conventional example of a multiband antenna, one has a structure in which a radiation element corresponding to a plurality of frequencies is provided in the antenna. For example, as a structure using a plurality of radiating elements having different resonance lengths, a design and measurement result of a three-frequency resonance antenna having a multilayer plate configuration (Technical Report of IEICE, AP2002-141, p41-46, 2003) (Non-Patent Document 1), "Multifrequency Microstrip Patch Antenna Using Multiple Stacked Elements (IEEE Microwave and Wireless Components Letters, vol.13, No.3, p123-124, 2003)" (Non-Patent Document 2), "2 A study on a configuration method of a frequency shared microstrip antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-161) ”(Non-patent Document 3) and the like.

  However, the above antenna has a structure in which a plurality of antennas are arranged in one place, and since a region where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited, it is difficult to transmit and receive all desired radio waves satisfactorily. there were.

  A structure in which one radiating element has a plurality of resonance lengths has also been proposed. For example, "A Study on Radiation Characteristics of Modified Sirpinski Type Microstrip Antenna (2003 IEICE Communication Society Conference, Lecture Number B-1-162)" (Non-Patent Document 4), "Double Frequency Slot Bowtie Antenna" (2003 IEICE Communication Society Conference, Lecture No. B-1-176) ”(Non-Patent Document 5).

  However, the modified Sirpinski-type microstrip antenna has a problem that radiation patterns are different in the three bands, and three frequencies cannot be transmitted and received under the same conditions in the same area. Also, it seems that the dual-frequency slot bow tie antenna can only handle up to about three frequencies.

  Thus, many methods for switching the resonance length of the antenna with a switch have been proposed. For example, JP 2000-236209 A (Patent Document 1), JP 2002-261533 A (Patent Document 2), JP 2003-124730 A (Patent Document 3), US Pat. No. 6,198,438 (Patent Document 4), and the like. There is.

  In Japanese Unexamined Patent Publication No. 2000-236209 (Patent Document 1), as shown in FIG. 13, a metal piece 101 is connected by a PIN diode 102 to form a dipole antenna. A bias is applied to the PIN diode 102 to switch the conduction / cutoff of the PIN diode 102 to change the resonance length.

  For this reason, resonance can occur only for one frequency and the gain can be reduced for radio waves having frequencies other than the desired frequency, so that the S / N reduction of the signal can be suppressed. The dipole antenna used in Japanese Unexamined Patent Publication No. 2000-236209 (Patent Document 1) needs to be excited with a balanced current.

  However, the line used for the RF circuit often uses an unbalanced current such as a microstrip line or a coplanar line. When a balanced current is required, a balun must be provided between the antenna and the line.

  In general, since the balun has a narrow band, it cannot cope with a plurality of frequencies, and one balun is required for each frequency. Therefore, in order to support multiband, it is necessary to arrange baluns in the vicinity of the feeding point of the dipole antenna as many as the number of multibands, and the number of multibands is limited by the balun installation area. Therefore, Japanese Patent Laid-Open No. 2000-236209 (Patent Document 1) can be used when there are few frequency bands such as a dual band, but cannot be applied to multibands with many frequency bands.

  In Japanese Patent Application Laid-Open No. 2002-261533 (Patent Document 2), as shown in FIG. 14, one feeding point (feeding pattern) 219 and a plurality of grounding points (grounding patterns) 220 a, 220 b, 220 c are included in the antenna element pattern 218. , 220d, and these grounding points 220a, 220b, 220c, 220d are respectively switched by switches SW221a, SW221b, SW221c, SW221d to change the resonance length. Reference numeral 211 denotes an antenna unit, 212 denotes a wiring board, 213 denotes a ground pattern, and 214 denotes an RF module.

  However, in Japanese Patent Laid-Open No. 2002-261533 (Patent Document 2), since the short-circuit point is switched by a switch, the input impedance of the antenna changes at each frequency. Therefore, the ground point can be moved only within a matching range, and it seems that the frequency range that can be varied in multiband cannot be increased.

  Actually, the variable frequency band disclosed in Japanese Patent Laid-Open No. 2002-261533 (Patent Document 2) is 1.55 to 2.2 GHz, which is as small as 30% with respect to the center frequency of 1.8 GHz. Therefore, it is possible to cope with the case of using a relatively close frequency band such as a cellular phone, but it is not possible to cope with the use of the 2.4 GHz band and the 5.2 GHz band as in a wireless LAN.

  In Japanese Patent Application Laid-Open No. 2003-124730 (Patent Document 3), as shown in FIGS. 15A and 15B, the first radiating element 320, the second radiating element 330, and the third radiating element 340 are switched. The power feeding point and the short-circuit point are shared, and four frequency bands are realized by switching the power feeding point and the short-circuit point by the switches SW360 and SW362. 300 is an antenna structure, 305 is a short-circuit plane, 310 is a sub-antenna structure, 322 is a first end, 324 is a feed line, 332 is a second end, 334 is an interval, 342 is a third end, 350 Is a feed line, 370 and 372 are radio frequency modules, and A1 and A2 are openings.

  However, in Japanese Patent Laid-Open No. 2003-124730 (Patent Document 3), it is necessary to arrange the three radiating elements 320, 330, and 340 on the same plane, and the area where radio waves can be transmitted and received satisfactorily on the surface of the wireless device is limited. Therefore, it is difficult to transmit and receive all four radio waves satisfactorily.

  In US Pat. No. 6,1984,438 (Patent Document 4), as shown in FIG. 16, element elements 400 arranged in a matrix are connected by MEMS switches 420, respectively.

  When all the MEMS switches 420 are turned off (shut off state), one side of each element element has a resonance length and corresponds to a high frequency. On the other hand, when all the MEMS switches are turned on (conducting state), the individual element elements are connected to form one rectangular radiating element as a whole and resonate at a low frequency.

  Here, in US Pat. No. 6,198,438 (Patent Document 4), a high-frequency feed point 405 (provided for each individual element) and a low-frequency feed point 410 are used to match the characteristic impedance of the line (usually 50Ω is used). Different points are used (one is provided in total). Therefore, there is a drawback that the number of multibands that can be handled is limited by the number of feeding points that can be arranged in the array antenna arranged in a matrix.

  In addition, since a switch for switching the feeding point is required, the structure of the antenna becomes complicated. Furthermore, there is a drawback that it is difficult to provide a feeding point on the MEMS switch 420. In the example of FIG. 16, the high-frequency feed point 405 that resonates with one element element and the low-frequency feed point 410 that resonates with the entire 3 × 3 array can be arranged on the element element (radiating element 400). When resonance is desired, the feeding point comes on the MEMS switch, so even if a 3 × 3 array is used, only two frequencies can be handled.

  In addition, when many communication standards coexist, a method of improving communication capacity by controlling not only the frequency but also the polarization has been taken. In the past, a single linear polarization was used, but polarization diversity and circular polarization that switch between horizontal polarization and vertical polarization are attracting attention. Already, GPS (Global Positioning System), ETC (Electronic Toll Collection System) , SADARS (Satellite Digital Audio Radio Services) and the like employ circular polarization.

  In the conventional example described above, the GPS antenna and the ETC antenna correspond to circular polarization in the three-frequency resonance antenna having a multilayer plate structure disclosed in Patent Document 1. However, in a three-frequency resonant antenna having a multilayer plate configuration, one radiating element corresponds to one frequency, and one frequency becomes one polarization and does not have a function of switching the polarization itself. Therefore, when switching the polarization at the same frequency, the number of radiating elements corresponding to the polarization is required, and there is a disadvantage that the antenna becomes large.

  Further, in Patent Documents 1 to 4 that disclose a method of switching the resonance length of an antenna with a switch, circularly polarized waves are not realized and the function of switching polarizations is not provided.

  The applicant has filed a patent application regarding the tapered slot antenna. For example, JP-A-10-13141 (Patent Document 5), JP-A-10-13143 (Patent Document 6), JP-A-10-173432 (Patent Document 7), JP-A-11-163626 (Patent Document) Reference 8). The tapered slot antenna has a constant input impedance over a wide band, and is classified into a wide band antenna. Although it can transmit and receive in a relatively wide frequency band, it does not have polarization switching / directivity control functions.

JP 2000-236209 A JP 2002-261533 A JP 2003-124730 A US Pat. No. 6,198,438 Japanese Patent Laid-Open No. 10-13141 Japanese Patent Laid-Open No. 10-13143 Japanese Patent Laid-Open No. 10-173432 JP 11-163626 A Design and measurement results of a three-frequency resonant antenna with a multi-layer configuration (Technical Report of IEICE, AP2002-141, p41-46, 2003) Multifrequency Microstrip Patch Antenna Using Multiple Stacked Elements (IEEE Microwave and Wireless Components Letters, vol.13, No.3, p123-124, 2003) A study on the configuration method of dual-band microstrip antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-161) A Study on Radiation Characteristics of Modified Sirpinski Type Microstrip Antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-162) Dual Frequency Slot Bowtie Antenna (2003 IEICE Communication Society Conference, Lecture No. B-1-176)

  The present invention provides a multi-band circularly polarized microstrip antenna technology that can handle multiple frequencies at a single feeding point, can be easily connected to an RF circuit, and can realize good transmission efficiency and reception efficiency. It is intended. The purpose of each claim is described below.

  Claims 1 to 8 are structures of a multiband-compatible circularly polarized microstrip antenna that can handle multiple frequencies at a single feeding point, can be easily connected to an RF circuit, and can realize good transmission efficiency and reception efficiency. The purpose is to provide.

  The object of the present invention is to provide a multiband-compatible circularly polarized microstrip antenna structure that can handle higher frequencies and a multiband-compatible circularly polarized microstrip antenna structure that can support low frequencies such as ETC and GPS. It is said.

  It is an object of the present invention to provide a multiband-compatible circularly polarized microstrip antenna structure with a wider bandwidth by devising the shape of the switch.

  The object of the twelfth aspect is to provide a structure of a wireless system capable of performing good transmission, reception or transmission / reception.

  In order to achieve the above object, the present invention has the following configuration. Hereinafter, the structure for each claim will be described.

a) According to the first aspect of the present invention, a rectangular feeding element having a feeding point on a diagonal line on the upper surface of a dielectric and a rectangular parasitic element surrounding the feeding element are arranged in a matrix, and the feeding element and the In a multiband-compatible circularly polarized microstrip antenna having a structure in which a parasitic element and a neighboring parasitic element are connected by a switch to form a rectangular radiating element, the length of one side of the rectangular feeding element is L , W is the length of the other side, Li is the smaller of the distances between the two sides on the W side and the feeding point, Wi is the smaller of the distances between the two sides on the L side and the feeding point, The length of the side corresponding to the L side among the sides of the rectangular radiating elements connected by the switch is L ′, and the length of the side corresponding to the W side among the sides of the rectangular radiating elements connected by the switch W ', two sides of W' side and front L / W = L '/ W', Li, where Li 'is the smaller distance from the feeding point and Wi' is the smaller distance between the two sides on the L 'side and the feeding point. It is characterized by / L = Li '/ L' and Wi / W = Wi '/ W'.

b) The invention according to claim 2 is the multiband-compatible circularly polarized microstrip antenna according to claim 1, wherein L / W = L '/ W', Li / L = Li '/ L', Wi / W = The shape of the rectangular radiating element in relation to Wi '/ W' can be formed by a plurality of the feeding element, the parasitic element, and the switch connecting adjacent parasitic elements. It is characterized by that.

c) The invention according to claim 3 is the multiband-compatible circularly polarized microstrip antenna according to claim 1 or 2, wherein L / W = L ′ / W ′, Li / L = Li ′ / L ′, Wi The outer shape of the parasitic element, the spacing between the feeding element and the parasitic element, and the spacing between the parasitic elements are adjusted so that / W = Wi ′ / W ′.

d) The invention according to claim 4 is the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 3, wherein a matching circuit connected to the feeding point by a changeover switch is provided. It is said.

e) The invention according to claim 5 has a rectangular feeding element on the upper surface of the dielectric, and the feeding element is fed from one vertex of the rectangle and constitutes a vertex facing the feeding point of the feeding element. Multiband having a structure in which rectangular parasitic elements surrounding two sides are arranged in a matrix, and the feeding element and the parasitic element, and the adjacent parasitic elements are connected by a switch to form a rectangular radiating element A corresponding circularly polarized microstrip antenna, wherein the length of one side of the rectangular feeding element is L, the length of the other side is W, on the L side of the sides of the rectangular radiating elements connected by the switch When the length of the corresponding side is L ′ and the length of the side corresponding to the W side among the sides of the rectangular radiating elements connected by the switch is W ′, L / W = L ′ / W ′ It is characterized by being.

f) The invention according to claim 6 is the multiband-compatible circularly polarized microstrip antenna according to claim 5, wherein the shape of the rectangular radiating element having a relationship of L / W = L ′ / W ′ is A plurality of feed elements, the parasitic elements, and the switches connecting adjacent parasitic elements can be formed.

g) The invention according to claim 7 is the multiband-compatible circularly polarized microstrip antenna according to claim 5 or 6, wherein the parasitic element has an outer shape such that L / W = L '/ W'. The distance between the feeding element and the parasitic element and the distance between the parasitic elements are adjusted.

h) The invention according to claim 8 is the multiband-compatible circularly polarized microstrip antenna according to claims 5 to 7, wherein a matching circuit is provided at the feeding point.

i) The invention according to claim 9 is the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 8, wherein the switch is at least one of a MEMS switch and a PIN diode. .

j) The invention according to claim 10 is the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 9, wherein the switch has substantially the same length as a side of the feeding element or the parasitic element. It is characterized by being formed over.

k) The invention according to claim 11 is the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 9, wherein each of the switches has a shape of a tip portion facing the other switch as V. It is characterized in that it is extended in a letter shape so that the gap between the four switches facing each other becomes an X letter.

l) A twelfth aspect of the invention is a transmission, reception or transmission / reception radio system using the multiband-compatible circularly polarized microstrip antenna according to any one of the first to eleventh aspects.

  The present invention has the following effects by having the above configuration. The effects of each claim will be described below.

a) A multi-band circularly polarized microstrip antenna according to claim 1, wherein a rectangular feed element having a feed point on a diagonal line on the upper surface of the dielectric and a rectangular parasitic element surrounding the feed element are arranged in a matrix The feeding element and the parasitic element, and the adjacent parasitic elements are connected by a switch to form a rectangular radiating element. Furthermore, the length of one side of the rectangular feeding element is L, the length of the other side is W, the smaller of the distance between the two sides on the W side and the feeding point is Li, the two sides on the L side and the feeding point Wi is the smaller of the distances to and L ′ of the sides of the rectangular radiating element connected by the switch is L ′, and the length of the side corresponding to the W side is W ′. , Where L ′ is the smaller distance between the two sides on the W ′ side and the feeding point, and Wi ′ is the smaller distance between the two sides on the L ′ side and the feeding point, L / W = L '/ W', Li / L = Li '/ L', Wi / W = Wi '/ W'.

  Therefore, when all the switches are OFF, the feeding element is separated from the parasitic element and resonates only with the feeding element. When a rectangular feeding element is fed diagonally, two orthogonal modes are excited on the L and W sides, and if the ratio of the L and W lengths is selected appropriately, the phase difference between the two orthogonal modes is 90 degrees. And circular polarization can be realized.

  In addition, when a rectangular radiating element is formed by connecting a feed element, a parasitic element, and an adjacent parasitic element with a switch, L / W = L '/ W', Li / L = Li '/ L' Since Wi / W = Wi ′ / W ′, the external shape of the radiating element connected by the switch is similar to that of the power feeding element, and power is fed from the diagonal line.

  Therefore, the rectangular radiation elements connected by the switch radiate circularly polarized waves having different resonance frequencies. As described above, the circularly polarized antenna of the present invention resonates only at a high frequency when all the switches are turned off, and resonates only at a low frequency when the switches are turned on. Therefore, the dual-band antenna has an antenna area corresponding to the low frequency. The antenna can be miniaturized.

  Further, since the feeding element is included in the rectangular radiating element, the feeding element can be placed in an excellent radio wave condition by arranging the rectangular radiating element in a region having the best radio wave condition on the wireless device.

  Further, since both the feed element and the rectangular radiation element have a simple circularly polarized microstrip antenna structure, the same radiation pattern is obtained.

  Further, since the feed element has a microstrip antenna structure, it can be excited by an unbalanced current using a coaxial line. Therefore, unlike Japanese Patent Laid-Open No. 2000-236209 (Patent Document 1), a balun is not required and connection with an RF circuit is facilitated.

  As for the input impedance, the rectangular radiating element connected to the rectangular feeding element with the switch has the similar outer shape and the same relative position of the feeding point, so the input impedance and switch when the feeding element alone resonates The input impedance of the rectangular radiating elements connected at is almost the same value.

  For this reason, at each frequency that can be selected by turning the switch ON and OFF, it is almost matched at one feeding point, reflection is suppressed, and radio waves can be transmitted or received efficiently. Therefore, unlike US Pat. No. US Pat. No. 6,198,438 (Patent Document 4), it is not necessary to switch the feeding point for each frequency, and only the feeding point of the feeding element can cope with multiple frequencies, and the structure is simpler than that of the US Pat. No. US Pat. No. 6,198,438 (Patent Document 4). Become.

b) In the multiband-compatible circularly polarized microstrip antenna according to claim 2, L / W = L '/ W', Li / L = Li '/ L', Wi / W = Wi '/ W' A plurality of rectangular radiating elements having a relationship can be formed by the above-described switch for connecting between a feeding element, a parasitic element, and adjacent parasitic elements.

  Therefore, when all the switches are turned off and when the switches are turned on to form a plurality of rectangular radiating elements, the resonance frequencies are all different, and a plurality of frequency bands can be selected by connecting the switches.

  In addition, if L and W are selected so that they are circularly polarized when the feed element is resonated, multiple rectangular radiating elements have a similar relationship in their external shapes and relative positions of the feed points. Radiate waves.

  Moreover, since the antenna size may be the antenna area corresponding to the lowest frequency, the antenna can be miniaturized. Also, since the feed element and the rectangular radiation elements are included in the rectangular radiation element that resonates at the lowest frequency, the rectangular radiation element that resonates at the lowest frequency is placed in the region with the best radio wave conditions on the radio. By doing so, the feeding element and the rectangular radiating element can be placed in a favorable radio wave condition. Furthermore, since both the feed element and the rectangular radiation element have a simple circularly polarized microstrip antenna structure, the same radiation pattern is obtained.

  Further, since the feed element has a microstrip antenna structure, it is excited by an unbalanced current. This facilitates connection to the RF circuit.

  Furthermore, the rectangular radiating elements connected by the switch are L / W = L '/ W', Li / L = Li '/ L', Wi / W = Wi '/ W' with respect to the feeding element. Since the relationship is established, the input impedance of the plurality of rectangular radiating elements connected by the switch is close to the input impedance of the rectangular feeding element alone.

  Therefore, even if the same feed point is used, the feed element alone and the plurality of rectangular radiating elements connected by the switch are substantially matched to the characteristic impedance of the feed line, and reflection can be suppressed. As a result, good circular polarization can be realized in all multiband frequency bands using one feeding point.

c) The multi-band circularly polarized microstrip antenna according to claim 3 is such that L / W = L '/ W', Li / L = Li '/ L', Wi / W = Wi '/ W'. In addition, since the outer shape of the parasitic element, the interval between the feeder element and the parasitic element, and the interval between the parasitic elements are adjusted, the multiband-compatible circularly polarized microstrip antenna according to claim 1 or 2 can be realized.

d) The multiband-compatible circularly polarized microstrip antenna according to claim 4 is provided with a matching circuit connected to the feeding point by a changeover switch. If the characteristic impedance of the feeder line is matched to the input impedance of the feeder element, the switch is turned off when all the switches between the feeder element and the parasitic element and the adjacent parasitic element are turned off and excited by the feeder element. By cutting off the matching circuit from the feed line, the feed element and the feed line are matched.

  In addition, when a rectangular radiating element is formed by connecting a switch, if the current in the antenna is limited by the gap surrounded by the switch and the input impedance is slightly different from that of the feeder element alone, the changeover switch is turned on and the antenna is By connecting to the matching circuit, the input impedance of the antenna can be matched with the characteristic impedance of the feeder line. As a result, good reception efficiency and transmission efficiency can be obtained in each multiband frequency band that can realize circular polarization.

e) In the multiband-compatible circularly polarized microstrip antenna according to claim 5, a rectangular feeding element is provided on the upper surface of the dielectric, and the feeding element is fed from one vertex of the rectangle, and the feeding point of the feeding element A structure in which rectangular parasitic elements surrounding two sides constituting the apex opposite to each other are arranged in a matrix, and a rectangular radiating element can be formed by connecting a feeding element and a parasitic element and a neighboring parasitic element by a switch. It has become.

  Further, the length of one side of the rectangular feeding element is L, the length of the other side is W, and the length of the side corresponding to the L side among the sides of the rectangular radiating element connected by the switch is L ′. When the length of the side corresponding to the W side is W ′, L / W = L ′ / W ′.

  Therefore, when all the switches are OFF, the feeding element is separated from the parasitic element and resonates only with the feeding element.

  When a rectangular feeding element is fed from the apex, two modes orthogonal to the L side and the W side are excited. Here, if the ratio of the lengths L and W is appropriately selected, the phase difference between the two orthogonal modes becomes 90 degrees, and circular polarization can be realized.

  In addition, when a rectangular radiating element is formed by connecting two rectangular parasitic elements surrounding two sides constituting the apex opposite to the feeding point of the feeding element, the feeding elements, and adjacent parasitic elements with a switch Since L / W = L ′ / W ′, the external shape of the radiating element connected by the switch is similar to that of the feeding element, and power is fed from the top of the radiating element. Therefore, the rectangular radiating elements connected by the switch radiate circularly polarized waves having different resonance frequencies.

  As described above, the circularly polarized antenna of the present invention resonates only at a high frequency when all the switches are turned off, and resonates only at a low frequency when the switches are turned on. Therefore, the dual-band antenna has an antenna area corresponding to the low frequency. The antenna can be miniaturized.

  Further, since the feeding element is included in the rectangular radiating element, the feeding element can be placed in an excellent radio wave condition by arranging the rectangular radiating element in a region having the best radio wave condition on the wireless device. Furthermore, since both the feed element and the rectangular radiation element have a simple circularly polarized microstrip antenna structure, the same radiation pattern is obtained.

  Further, since the feed element has a microstrip antenna structure, it can be excited by an unbalanced current using a coaxial line.

  Looking at the input impedance, the rectangular radiating element connected to the rectangular feed element with a switch is similar in shape and fed from the top, so the rectangle connected by the switch to the input impedance when resonating with the feed element alone The input impedance of the radiating element is almost the same value. For this reason, at each frequency that can be selected by turning the switch on and off, it is almost matched at one feeding point, reflection is suppressed, and radio waves can be transmitted or received efficiently.

f) In the multiband-compatible circularly polarized microstrip antenna according to claim 6, the shape of the rectangular radiating element having a relationship of L / W = L ′ / W ′ includes a feeding element, a parasitic element, and an adjacent element. A plurality of switches can be taken by the switches connecting the parasitic elements.

  Therefore, when all the switches are turned off and when the switches are turned on to form a plurality of rectangular radiating elements, the resonance frequencies are all different, and a plurality of frequency bands can be selected by the switches.

  In addition, when L and W are selected so that the circularly polarized wave is obtained when the feed element alone is resonated, the multiple rectangular radiating elements have a similar relationship in their external shapes and the relative positions of the feed points. Radiate.

  Moreover, since the antenna size may be the antenna area corresponding to the lowest frequency, the antenna can be miniaturized. In addition, since the feed element and the rectangular radiation elements are included in the rectangular radiation element that resonates at the lowest frequency, the rectangular radiation element that resonates at the lowest frequency is placed in the area with the best radio wave conditions on the radio. By doing so, the feeding element and the rectangular radiating element can be placed in a favorable radio wave condition.

  Furthermore, since both the feed element and the rectangular radiation element have a simple circularly polarized microstrip antenna structure, the same radiation pattern is obtained. Further, since the feed element has a microstrip antenna structure, it can be excited by an unbalanced current using a coaxial line.

  Furthermore, since the relation of L / W = L '/ W' is established for the plurality of rectangular radiating elements connected by the switch, the input impedance of the plurality of rectangular radiating elements connected by the switch is The value is close to the input impedance of the rectangular feed element alone. Therefore, even if the same feed point is used, the feed element alone and the plurality of rectangular radiating elements connected by the switch are substantially matched to the characteristic impedance of the feed line, and reflection can be suppressed.

g) In the multiband-compatible circularly polarized microstrip antenna according to claim 7, the external shape of the parasitic element, the distance between the feeding element and the parasitic element, and the absence of L / W = L ′ / W ′. Since the interval between the feeding elements is adjusted, the multiband-compatible circularly polarized microstrip antenna according to claims 5 and 6 can be realized.

h) In the multiband-compatible circularly polarized microstrip antenna according to claim 8, a matching circuit is provided at the feeding point. Here, if the constant of the matching circuit is selected so that the input impedance of the feed element matches the output impedance of the RF circuit, reflection between the feed element and the RF circuit can be suppressed.

  In addition, when a rectangular radiating element is formed by turning on a switch that connects between a feeding element, a parasitic element, and adjacent parasitic elements, the input impedance of the rectangular radiating element is almost the same as the input impedance of the feeding element. Therefore, even when a switch is connected to form a rectangular radiating element, reflection can be suppressed between the antenna and the RF circuit.

i) In the multi-band-compatible circularly polarized microstrip antenna according to claim 9, at least one of the MEMS switch and the PIN diode is a switch that connects between the feeding element, the parasitic element, and the adjacent parasitic element.

  When a MEMS switch is used, it is possible to cut off signals well even at high frequencies up to about 100 GHz, and the insertion loss is also small. Can be configured.

  On the other hand, PIN diodes can be obtained at low cost and can block signals well up to 10 to 20 GHz, and therefore can be applied to low-frequency circularly polarized waves such as GPS and ETC.

j) In the multiband circularly polarized microstrip antenna according to claim 10, since the gap between the switches can be reduced, a multiband circularly polarized microstrip antenna with a wider band can be realized.

k) In the multiband circularly polarized microstrip antenna according to claim 11, since the gap between the switches can be made smaller, a multiband circularly polarized microstrip antenna having a wider band can be realized.

l) Since the radio system according to claim 12 uses the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 11, it can correspond to a plurality of radio standards. Further, since a good circular polarization is realized at a desired frequency, good transmission / reception or transmission / reception can be performed.

  Further, since the antenna has only one feeding point, the antenna structure is simpler than that of US Pat. As a result, it is possible to manufacture a wireless system compatible with circular polarization having good transmission / reception or transmission / reception characteristics at a lower cost.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

<Example 1>
FIG. 1 is a diagram showing an example of a multiband-compatible circularly polarized microstrip antenna of the present invention. FIG. 4A is a top view and FIG. 4B is a cross-sectional view.

  The multiband-compatible circularly polarized microstrip antenna of this example corresponds to two frequencies, and a ground plane 11 made of a copper foil pattern is formed on the lower surface of a dielectric 10 made of a quartz substrate having a relative dielectric constant of 3.9. On the upper surface of the dielectric 10, there is one rectangular feeding element 12 made of a copper foil pattern. The feeding element 12 has one feeding point 13 on a rectangular diagonal line.

  In addition, rectangular parasitic elements 14 surrounding the feeding element 12 are arranged in a matrix, and the feeding element 12 and the parasitic element 14 and the adjacent parasitic elements 14 can be connected by a switch 15. .

  In this configuration, when all the switches 15 are turned on, a rectangular radiating element 16 is formed. As shown in FIG. 2B, the power feeding element 12 has a structure in which inset power feeding is performed by a coaxial line 17 penetrating the dielectric 10.

  Here, the length of one side of the rectangular feeding element 12 is L, the length of the other side is W, and the smaller of the distances between the two sides on the W side and the feeding point 13 is Li and the two on the L side. The smaller of the distance between the side and the feeding point 13 is defined as Wi.

  On the other hand, when all the switches 15 are OFF, the feeding element 12 is separated from the parasitic element 14 and resonates only with the feeding element 12. When the rectangular feeding element 12 is fed from a diagonal line, two modes orthogonal to the L side and the W side are excited. Here, if the ratio of the lengths L and W is appropriately selected, the phase difference between the two orthogonal modes becomes 90 degrees, and circular polarization can be realized.

Specifically, when the unloaded Q of a square microstrip antenna when both sides are equal is Qo, if L <W,
W / L = 1 + (1 / Qo)
Then, it becomes circular polarization. The concept of the present invention can be similarly applied to elliptically polarized waves whose axial ratio is deviated from 1, so that the present invention includes elliptically polarized waves.

  Next, the case where the feed element 12 and the parasitic element 14 and the adjacent parasitic elements 14 are connected by the switch 15 to form the rectangular radiation element 16 will be described.

  Of the sides of the rectangular radiating element 16, the length of the side corresponding to the L side is L ′, the length of the side corresponding to the W side is W ′, and the distance between the two sides on the W ′ side and the feeding point 13 is The smaller one is Li ′, and the smaller one of the distances between the two sides on the L ′ side and the feeding point 13 is Wi ′. The rectangular radiating element 16 connected by the switch 15 also uses the same feeding point 13 as the feeding element 12 as the feeding point.

The feature of the present invention is that
L / W = L '/ W' (1)
Li / L = Li '/ L' (2)
Wi / W = Wi '/ W' (3)
It is to become. In this example, the radiating element 16 connected by the switch 15 is twice as large as the feeding element 12, and L ′ = 2L and W ′ = 2W.

  The radiating element 16 connected by the switch 15 also has a gap surrounded by the switch 15, but its outer shape is almost rectangular, and is similar to the feeding element 12 from the relationship of the expression (1).

  Here, the ratio of L and W of the power feeding element 12 is set so that the phase difference between the two modes is 90 degrees when power is fed from a diagonal line. When the sides L ′ and W ′ of the radiating element 16 connected by the switch are also fed from diagonal lines, the phase difference between the two orthogonal modes is 90 degrees although the resonance frequencies are different.

  Further, from the relationship of the expressions (2) and (3), the relative position of the feeding point 13 with respect to the feeding element 12 is the same as the relative position of the feeding point 13 with respect to the radiating element 16 connected by the switch 15. In this example, since the feeding point 13 is on the diagonal line of the feeding element 12, the feeding point 13 is also on the diagonal line of the rectangular radiation element 16 for the radiation element 16 connected by the switch 15.

  Therefore, since the above equations (1) to (3) are satisfied, the rectangular radiating element 16 connected by the switch 15 can also realize circular polarization. In this case, the resonance frequency is determined by the lengths of the sides L and W of the radiating element 16 connected by the switch 15. In this example, L ′ = 2L and W ′ = 2W. The frequency is / 2. As a result, the antenna of this example can cope with circularly polarized waves of two frequencies together with the case where the feeding element 12 is resonated alone.

  As described above, the circularly polarized antenna of this example resonates only at a high frequency when all the switches are turned off, and resonates only at a low frequency when all the switches are turned on. Can support dual-band circularly polarized waves, and the antenna can be downsized.

  Further, since the feeding element 12 is included in the rectangular radiating element 16, the feeding element 12 can be placed in a good radio wave condition by arranging the rectangular radiating element 16 in a region having the best radio wave condition on the wireless device. it can. Further, since both the feed element 12 and the rectangular radiating element 16 have a simple circularly polarized microstrip antenna structure, similar radiation patterns are obtained.

  Further, since the feed element 12 has a microstrip antenna structure, it can be excited by an unbalanced current using a coaxial line. Therefore, unlike Japanese Patent Laid-Open No. 2000-236209 (Patent Document 1), a balun is not required and connection with an RF circuit is facilitated. It should be noted that excitation can also be performed using an unbalanced mode such as a microstrip line or a coplanar line instead of the coaxial line 17.

Next, consider the input impedance of the radiating element 16 connected by the switch 15.
When the microstrip antenna performs inset power feeding from the center of the side (see FIG. 2), the input impedance of the antenna can be obtained from an approximate expression.

The length of the side of the microstrip antenna in the excitation direction is Y, the length of the side orthogonal to the excitation direction is X, the distance between the feed point 13 and the side orthogonal to the excitation direction is Yi, the relative dielectric constant of the dielectric is εr, Assuming that the input impedance at the antenna end is Ra and the input impedance at the inset feed is Rin, it is described as follows.
Ra = 90 {(εr ² / (εr-1)) (Y / X) ² } (4)
Rin = Ra {cos ((π / Y) Yi ′)} ² (5)

As can be seen from the above equation, in the rectangular microstrip antenna, the input impedance Ra at the antenna end is proportional to (Y / X) ² and the input impedance Rin at the inset feed is affected by (Yi '/ Y). The

  The case where power is supplied from a diagonal line can be considered in the same manner. Since the power supply element 12 and the radiating element 16 connected by the switch are also inset power supply, the input impedance Zin is a mode on the L side or L ′ side. (L / W), (L '/ W'), (Li / L), (Li '/ L'), and in the W side mode (L / W), (L '/ W'), (Wi / W), (Wi '/ W').

Here in this example
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
Is true.

  Therefore, in the radiating element 16 in this example in which the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 12 are connected by the switch 15, the input impedance Zin ′ in the inset feeding is the input impedance Zin in the feeding element 12 alone. Is almost the same value.

  In general, in inset feeding, the feeding point 13 of the feeding element 12 is provided at a position where it can match the characteristic impedance (usually 50Ω) of the coaxial line 17. In the antenna of this example, since the input impedance Zin ′ of the radiating element 16 connected by the switch 15 is close to the input impedance Zin of the feeding element 12, the characteristic impedance of the coaxial line 17 ( (Normally 50Ω), the reflection is suppressed, and radio waves can be transmitted or received efficiently.

  Therefore, unlike US Pat. No. 6,198,438 (Patent Document 4), it is not necessary to switch the feeding point 13 for each frequency, and only the feeding point 13 of the feeding element 12 can handle two frequencies. It becomes simpler than the structure.

In this example, in order to satisfy the relationship of the formulas (1), (2), and (3), as shown in FIG. 3, eight parasitic elements P1 to P8 arranged around the feed element 12 and The external shape of the switch 15 was as follows.
PL1 + SL1 = L-Li (6)
PL2 + SL2 = Li (7)
PW1 + SW1 = Wi (8)
PW2 + SW2 = W-Wi (9)

here,
L1, length of P1, P2, P3: PL1,
L4 side length of P4 and P5: L,
Length of excitation direction of P6, P7, P8: PL2,
L1-side length of the switch connecting P1-P4, P2-feed element, P3-P5: SL1,
L4-side length of the switch connecting P4-P6, feeding element-P8, P5-P8: SL2,
P1, P4, P6 W 'side length: PW1,
P2, P7 W 'side length: W,
W3 side length of P3, P5, P8: PW2,
W1-side length of the switch connecting P1-P2, P4-feed element, P6-P7: SW1,
W2-side length of the switch connecting P2-P3, feed element-P5, P7-P8: SW2,

Since the external shapes and intervals of the parasitic elements P1 to P8 and the switch 15 are set as in the expressions (6), (7), (8), and (9), the rectangular radiation element 16 connected by the switch 15 The outline is
L '= PL1 + SL1 + L + SL2 + PL2 = (L-Li) + L + (Li) = 2L
W '= PW1 + SW1 + W + SW2 + PW2 = (Wi) + W + (W-Wi) = 2W
∴L / W = L '/ W'
Thus, the radiating element 16 that satisfies the equation (1) and is connected by the switch 15 is twice as large as the feeding element 12.

When looking at the position of the feeding point 13 of the radiating element 16 connected by the switch 15, the L ′ side is
Li '= PL2 + SL2 + Li = (Li) + Li = 2Li
Since in this example L '= 2L,
Li '/ L' = 2Li / 2L = Li / L
It can be seen that the expression (2) is satisfied.

For W 'side,
Wi '= PW1 + SW1 + Wi = (Wi) + Wi = 2Wi
Since in this example W '= 2W,
Wi '/ W' = 2Wi / 2W = Wi / W
It can be seen that the expression (3) is satisfied.

  Other switch dimensions, that is, the length of the W ′ side of the switch 15 connecting P1-P4 and P4-P6 is equal to or less than PW1, and the length of the W ′ side of the switch 15 connecting the P2-feed element and the feed element-P8. The length on the W 'side of the switch 15 connecting P3-P5, P5-P8 is PW2 or less, and the length on the L' side of the switch 15 connecting P1-P2, P2-P3 is PL1 or less. The length of the L ′ side of the switch 15 connecting P6-P7 and P7-P8 is not more than PL2, and the length of the L ′ side of the switch 15 connecting the P4-feeding element 12 and feeding element 12-P5 is not more than L. And it is sufficient.

  The relations of the expressions (6) to (9) are such that the outer shape of the rectangular radiating element 16 and the feeding element 12 connected by the switch 15 and the relative position of the feeding point 13 are the following expressions (1) to (3). There is only one condition for satisfying the present invention, and the present invention need not be limited to the expressions (6) to (9).

The present invention
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
The outer shape of the parasitic element, the interval between the feeder element 12 and the parasitic element, and the interval between the parasitic elements may be adjusted so that Any adjustment of the distance between the element 12 and the parasitic element and the distance between the parasitic elements is included in the present invention.

  In this example, it is desirable that the switch 15 for connecting the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14 is a MEMS switch or a PIN diode.

  When a MEMS switch is used, a high frequency up to about 100 GHz can be satisfactorily blocked, and the insertion loss is also small. Therefore, a dual-frequency circularly polarized microstrip antenna for a higher frequency, for example, a millimeter wave, is used. Can be configured.

  On the other hand, PIN diodes can be obtained at low cost and can cut off signals well up to 10 to 20 GHz, so that they are suitable for low frequency, circularly polarized, multifrequency applications such as GPS and ETC.

  The MEMS switch and the PIN diode may be provided on the dielectric surface by surface mounting, and the feeding element 12 and the parasitic element 14 or the parasitic element 14 may be connected. When a high-resistance semiconductor substrate such as a GaAs substrate is used as the dielectric 10, a MEMS switch or a PIN diode is formed on the semiconductor substrate by using a semiconductor process, and the feeding element 12 and the parasitic element 14 or the parasitic element 14 is connected. Can be connected.

<Example 2>
FIG. 4 is a diagram showing another example of the multiband-compatible circularly polarized microstrip antenna of the present invention.

  The circularly polarized microstrip antenna corresponding to the multiband of this example has a ground plate (not shown) made of a copper foil pattern formed on the lower surface of the dielectric 10 made of an alumina substrate having a relative dielectric constant of about 10. The dielectric 10 There is one rectangular feeding element 12 made of a copper foil pattern on the upper surface of the, and the feeding element 12 has one feeding point 13 on a rectangular diagonal line.

  In addition, a rectangular parasitic element 14 that doublely surrounds the feeding element 12 is arranged in a matrix, and the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14 can be connected by a switch 15. It has become.

  When the parasitic element 14 surrounding the feeding element 12 in a single layer and the switch 15 connecting the feeding element 12 and the switch 15 connecting the parasitic element 14 surrounding the feeding element 12 in a single layer are turned on, the first When the rectangular radiation element 161 (outer shape is L ′ × W ′) is formed and all the switches 15 are turned on, the second rectangular radiation element 162 (outer shape is L ″ × W ″). Is formed.

  Also in this example, the power feeding element 12 has a structure in which inset power feeding is performed by a coaxial line (not shown) penetrating the dielectric 10 as in the first embodiment.

The feature of the present invention is that
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
The rectangular radiating element having a relationship with the above can be provided in a plurality of shapes by the switch 15 connecting the feeding element, the parasitic element, and the adjacent parasitic element.

In this example, the first radiating element 161 connected by the switch 15 and the second radiating element 162 connected by the switch 15 are connected to the feeding element 12.
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
Is in a relationship.

That is, it is formed when the parasitic element 14 surrounding the feeding element 12 in a single layer, the switch 15 connecting the feeding element 12 and the switch 15 connecting the parasitic elements surrounding the feeding element 12 in a single layer are turned on. In the first rectangular radiating element 161 (the outer shape is L ′ × W ′), the length of the side corresponding to the L side of the feeding element 12 is L ′, and the length of the side corresponding to the W side is W ′, W The smaller one of the distances between the two sides on the side and the feeding point 13 is Li ', the smaller one of the distances between the two sides on the L' side and the feeding point 13 is Wi ', and the feeding element 12 is single. When the switch 15 that connects the parasitic element 14 and the feeder element 12 that are surrounded by and the switch 15 that connects the parasitic element 14 that surrounds the feeder element 12 in a double manner are turned on, that is, all the switches 15 are turned on. Second rectangular radiating element 162 formed in the case (the outer shape is L ″ × W ″) ), The length of the side corresponding to the L side of the feeding element 12 is L ″, the length of the side corresponding to the W side is W ″, and the distance between the two sides on the W ″ side and the feeding point 13 If the smaller one is Li '' and the smaller one of the distances between the two sides on the L '' side and the feeding point 13 is Wi '',
L / W = L '/ W' = L '' / W '' (10)
Li / L = Li '/ L' = Li '' / L '' (11)
Wi / W = Wi '/ W' = Wi '' / W '' (12)
It has become. The first and second rectangular radiating elements also use the same feeding point 13 as the feeding element 12 as the feeding point.

  In the present embodiment, the first radiating element 161 connected by the switch 15 is twice as large as the feeding element 12, L ′ = 2L, W ′ = 2W, Li ′ = 2Li, Wi ′ = 2Wi, The second radiating element 162 connected by the switch 15 has a size three times that of the feeding element 12, and L ″ = 3L, W ″ = 3W, Li ″ = 3Li, and Wi ″ = 3Wi.

  When all the switches 15 are OFF, the power feeding element 12 alone resonates. When the rectangular feeding element 12 is fed from a diagonal line, two modes orthogonal to the L side and the W side are excited. Here, if the ratio of the lengths L and W is appropriately selected, the phase difference between the two orthogonal modes becomes 90 degrees, and circular polarization can be realized. Let the resonant frequency at that time be f.

  Since the first rectangular radiating element 161 and the second rectangular radiating element 162 connected by the switch 15 satisfy the expressions (10) to (12), the outer shape and the relative position of the feeding point are similar to those of the feeding element 12. Become a relationship.

  Therefore, in the first rectangular radiating element 161, each side (L ′, W ′) is twice as long as each side (L, W) of the feeding element 12, so that circular polarization of about f / 2 is generated. discharge. Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into account, so that the resonance frequency slightly deviates from f / 2.

  Further, in the second rectangular radiating element 162, each side (L ″, W ″) is three times each side (L, W) of the feeding element 12. Release waves. Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into account, so that the resonance frequency slightly deviates from f / 3.

  Therefore, the antenna of this example can selectively cope with three frequencies by turning on / off the switch 15. As a result, the antenna area corresponding to the low frequency can cope with the circular polarization of the three frequencies, and the antenna can be downsized.

  Further, since the feeding element 12 and the first radiating element 161 are included in the second radiating element 162, the second radiating element 162 is arranged in a region having the best radio wave condition on the wireless device. In addition, both the first radiating element 161 can be placed in a good radio wave condition.

  Furthermore, since the feed element 12, the first radiating element 161, and the second radiating element 162 have a simple circularly polarized microstrip antenna structure, they have the same radiation pattern.

  In addition, since the antenna of this example has the structure of the microstrip antenna as in the first embodiment, it can be excited with an unbalanced current, so that it can be easily connected to the RF circuit. Become.

  Next, the input impedance Zin ′ of the first radiating element 161 and the input impedance Zin ″ of the second rectangular radiating element 162 will be described.

  Also in this example, the first radiating element 161 connected by the switch 15 has a gap surrounded by the switch 15, but the outer shape is rectangular. Therefore, the input impedance Zin ′ is (L ′ / L) in the mode on the L ′ side. W ') and (Li' / L '), and the mode on the W' side is affected by (L '/ W') and (Wi '/ W').

  Since the second radiating element 162 also has a gap surrounded by the switch 15 but has a rectangular outer shape, its input impedance Zin ″ is (L ″ / W ″) and (Li) in the L ″ side mode. In '' / L '') and W '' modes, it is affected by (L '' / W '') and (Wi '' / W '').

Here, in this example,
L / W = L '/ W' = L`` / W ''
Li / L = Li '/ L' = Li`` / L ''
Wi / W = Wi '/ W' = Wi`` / W ''
Therefore, the input impedances Zin ′ and Zin ″ of the first radiating element 161 and the second radiating element 162 connected by the switch 15 are substantially close to the input impedance Zin of the feeding element 12 alone.

  Therefore, even when the first radiating element 161 and the second radiating element 162 are formed by the connection of the switch 15 so as to correspond to a lower frequency than the feeding element 12, the characteristic impedance of the coaxial line 17 is substantially matched. Reflection is suppressed and radio waves can be transmitted or received efficiently. Therefore, unlike US Pat. No. 6,198,438 (Patent Document 4), there is no need to switch the feeding point 13 for each frequency, and only the feeding point of the feeding element 12 can cope with three frequencies.

Also in this example, as in the first embodiment, the outer shape of the parasitic element 14, the interval between the feeding element 12 and the parasitic element 14, and the interval between the parasitic elements 14 are adjusted.
L / W = L '/ W' = L`` / W ''
Li / L = Li '/ L' = Li`` / L ''
Wi / W = Wi '/ W' = Wi`` / W ''
It was. Further, a MEMS switch or a PIN diode can be used as the switch 15 that connects the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14.

  In the first embodiment, a circularly polarized antenna corresponding to two frequencies and in this example corresponding to a three frequencies has been described. However, the antenna of the present invention is not limited to two frequencies or three frequencies.

In the case of supporting more frequency bands, the feeding element 12 is surrounded more than once by the parasitic element 14 and the feeding element 12 and the parasitic element 14 and the parasitic element 14 can be connected by the switch 15. At each frequency
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
The outer shape of the parasitic element 14, the distance between the feeding element 12 and the parasitic element 14, the distance between the parasitic elements 14, and the like may be adjusted.

<Example 3>
FIG. 5 is a diagram showing another example of the multiband-compatible circularly polarized microstrip antenna of the present invention. FIG. 4A is a top view and FIG. 4B is a cross-sectional view.

  The multiband-compatible circularly polarized microstrip antenna of this example is provided with a matching circuit 18 connected by changeover switches 181 and 182 between the feeding point 13 and the RF circuit 19 of the antenna of the first embodiment.

In the first embodiment, the radiating element 16 connected by the switch 15 is:
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
However, since the gap surrounded by the switch 15 limits the current in the antenna, the input impedance Zin ′ in the inset power supply slightly deviates from the input impedance Zin of the power supply element.

  Generally, in inset feeding, the feeding point 13 of the feeding element 12 is provided at a position where it can be matched with the output impedance (usually 50Ω) of the RF circuit 19, so that the radiating element 16 connected by the switch 15 completely matches the output impedance of the RF circuit 19. Cannot be matched, and the transmission / reception efficiency of radio waves slightly decreases.

  In this example, the matching circuit 18 connected by the changeover switches 181 and 182 is provided immediately below the feed point 13 of the antenna. When the feed element 12 is made to resonate so as to correspond to the high frequency, the changeover switches 181 and 182 are turned OFF, The feed element 12 is directly excited by the coaxial line 17.

  On the other hand, when using the radiating element 16 connected by the switch 15 to support low frequency, the changeover switches 181 and 182 are turned on to connect the antenna to the matching circuit 18 and the input impedance of the antenna is matched to 50Ω. Connected to the RF circuit 19. Therefore, efficient transmission / reception is possible even in a low frequency response using the radiation element 16 connected by the switch 15.

  In this example, the case where the matching circuit 18 matches the input impedance of the radiating element 16 connected by the switch 15 has been described. However, the input impedance of the radiating element 16 connected by the switch 15 is matched to the output impedance of the RF circuit 19, When the feed element 12 is excited, the matching may be performed by turning on the changeover switches 181 and 182 and connecting the matching circuit 18 and the antenna.

  As a configuration of the matching circuit 18, a circuit in which lumped constant elements such as a capacitor and an inductor are configured in an L type, a π type, and a T type may be used when the resonance frequency of the antenna is relatively small. When the resonant frequency of the antenna is high, a circuit in which a distributed constant circuit such as a stub is configured in an L type, a π type, or a T type can be used.

  Further, the matching circuit 18 may be constituted by a phase shifter and a capacitor, and a generally known matching circuit may be used in accordance with the resonance frequency of the antenna.

  Since Example 1 is compatible with two frequencies, when the feed element 12 is matched to 50Ω, a fixed circuit is suitable because a matching circuit 18 that matches the radiation element 16 connected by the switch 15 to 50Ω may be provided. Yes.

  On the other hand, in Example 2, since it corresponds to three frequencies, when the feeding element 12 is matched to 50Ω, in the fixed type matching circuit, only one of the first or second radiating element is matched to 50Ω and the other is matched. It cannot be matched to 50Ω.

  In order to further improve the reception and transmission efficiency of the first and second radiating elements, a matching circuit is provided for each frequency, and a selection switch is selected for each frequency, or a variable capacitor or a variable phase shifter is provided. A variable matching circuit including one or more may be provided.

<Example 4>
FIG. 6 is a diagram showing another example of the multiband-compatible circularly polarized microstrip antenna of the present invention. FIG. 4A is a top view and FIG. 4B is a cross-sectional view.

  The multiband-compatible circularly polarized microstrip antenna of this example supports two frequencies, and a ground plane 11 made of an Au foil pattern is formed on the lower surface of a dielectric 10 made of a quartz substrate having a dielectric constant of 3.9, A rectangular feeding element 12 made of an Au foil pattern is provided on the upper surface of the dielectric 10, and the feeding element 12 is fed from a feeding point 131 at one vertex of the rectangle. The feed line 130 is formed of a microstrip line on the dielectric 10 and is connected to one vertex of the rectangular feed element 12.

  Further, rectangular parasitic elements 14 surrounding two sides constituting the apex facing the feeding point 131 of the feeding element 12 are arranged in a matrix. Further, the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14 can be connected by a switch 15, and when all the switches 15 are turned on, a rectangular radiating element 16 is formed. The Here, the length of one side of the rectangular feeding element 12 is L, and the length of the other side is W.

  When all the switches 15 are OFF, the feed element 12 is separated from the parasitic element 14 and resonates only with the feed element 12.

  When the rectangular feeding element 12 is fed from the feeding point 131 at the apex, two modes orthogonal to the L side and the W side are excited. Here, if the ratio of the lengths of L and W is appropriately selected, the phase difference between the two orthogonal modes becomes 90 degrees, and circular polarization can be realized.

Specifically, if the unloaded Q of a square microstrip antenna with equal sides is Qo, and L <W
W / L = 1 + (1 / Qo)
Then, it becomes circular polarization.

  The concept of the present invention can be similarly applied to elliptically polarized waves whose axial ratio is deviated from 1, so that the present invention includes elliptically polarized waves.

  Next, two rectangular parasitic elements 14 surrounding the two sides constituting the apex of the feeding element 12 facing the feeding point 131 and the feeding element 12 and the adjacent parasitic elements 14 are connected by a switch 15. The case where the rectangular radiation element 16 is formed will be described.

  Of the sides of the rectangular radiating element 16, the length of the side corresponding to the L side is L ′, and the length of the side corresponding to the W side is W ′. The radiating element 16 connected by the switch 15 also uses the same feeding point 131 as the feeding element 12.

Features of the present invention are
L / W = L '/ W' (13)
It is to become.

  In this example, the radiating element 16 connected by the switch 15 is twice as large as the feeding element 12, and L ′ = 2L and W ′ = 2W. The radiating element 16 connected by the switch 15 also has a gap surrounded by the switch 15, but its outer shape is almost rectangular, and is similar to the feeding element 12 from the relationship of the expression (13).

  Here, since the ratio of L and W of the power feeding element 12 is set so that the phase difference between the two modes is 90 degrees when power is fed from the apex, the switch 15 having a similar relationship with the power feeding element 12 is used. When the sides L ′ and W ′ of the connected radiating element 16 are also fed from the apex, the resonance frequency is different, but the two modes have a phase difference of 90 degrees.

  Since the rectangular radiating element 16 has a shape in which the two parasitic parasitic elements 14 surrounding the two sides constituting the vertex facing the feeding point 131 and the feeding element 12 are connected, the feeding point 131 of the radiating element 16 is rectangular. Becomes the apex of the radiating element 16.

  Therefore, the rectangular radiating element 16 connected by the switch 15 is also fed from the rectangular vertex, and the rectangular radiating element 16 can also realize circular polarization. In this case, the resonance frequency is determined by the lengths of the sides L ′ and W ′ of the radiating element 16 connected by the switch 15. In this example, L ′ = 2L and W ′ = 2W. The frequency is 1/2.

  As described above, when the structure of this example is used, when all the switches 15 are turned off, high-frequency circularly polarized waves that resonate with the feed element 12 alone are radiated, and when all the switches 15 are turned on, the low-frequency waves are emitted. Since the circularly polarized wave is radiated, a circularly polarized wave of two frequencies can be realized. Further, the size of the antenna may be only the antenna area corresponding to the low frequency, and the antenna can be miniaturized.

  Further, since the feeding element 12 is included in the rectangular radiating element 16, the feeding element 12 can be placed in a good radio wave condition by arranging the rectangular radiating element 16 in a region having the best radio wave condition on the wireless device. it can.

  Furthermore, since the feed element 12 and the rectangular radiating element 16 have a simple circularly polarized microstrip antenna structure, similar radiation patterns are obtained.

  Further, since the feed element 12 has a microstrip antenna structure, it can be excited by a microstrip line. Therefore, unlike Japanese Patent Laid-Open No. 2000-236209 (Patent Document 1), a balun is not required and connection with an RF circuit is facilitated.

Next, the input impedance of the antenna of this example will be described.
When all the switches 15 are turned off to resonate only with the power feeding element 12, the power feeding element 12 is fed from the antenna end, so the input impedance Za is set to the ratio (L / W) of the two sides constituting the power feeding element 12. Affected.

  On the other hand, when the rectangular radiating element 16 is formed by connecting the feeding element 12, the parasitic element 14, and the adjacent parasitic element 14 with the switch 15, the outer shape is almost rectangular and the power is fed from the top. The input impedance is affected by the length (L ′ / W ′) of two sides constituting the rectangle. Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into account, but the input impedance is not greatly changed.

Here in this example
L / W = L '/ W'
Therefore, the input impedance Za ′ of the radiating element 16 connected by the switch 15 is almost the same as the input impedance Za of the feeding element 12 alone.

  When power is supplied from the apex of the feed element 12, the characteristic impedance of the microstrip line is used so as to match the input impedance of the feed element 12, or the resistance value of the 50Ω microstrip line is converted by using a λ / 4 line to supply power. In general, it is used by matching with the input impedance of the element 12.

  In the antenna of this example, since the input impedance Za ′ of the radiating element 16 connected by the switch 15 is close to the input impedance Za of the feeding element 12, the microstrip line that is the feeding line 130 even when the switch 15 is turned on to correspond to the low frequency. It is in a state of being substantially matched with the other, reflection is suppressed, and radio waves can be transmitted or received efficiently.

  Therefore, in this example as well, unlike the US Pat. No. US Pat. No. 6,198,438 (Patent Document 4), it is not necessary to switch the feeding point 131 for each frequency. The structure is simpler than that of the antenna of Document 4).

In this example, in order to satisfy the relationship of the expression (13), the external shapes of the three parasitic elements 14 (P1 to P3) and the switch 15 arranged around the feeder element 12 as shown in FIG. I made it.
PL + SL = L (14)
PW + SW = W (15)

here,
P1, P2 L 'side length: PL
L3 side length of P3: L
L1-side length of switch connecting P1-feed element and P2-P3: SL
P1 W 'side length: W
P2, P3 W 'side length: PW
W 'side length of switch connecting P1-P2 and feed element-P3: SW

Since the external shape and interval of the parasitic element 14 (P1 to P3) and the switch 15 are set as in the equations (14) and (15), the external shape of the radiating element 16 connected by the switch 15 is
L '= PL + SL + L = (L) + L = 2L
W '= W + SW + PW = W + (W) = 2W
∴L / W = L '/ W'
This satisfies the equation (13). In this example, the radiating element 16 connected by the switch 15 is twice as large as the feeding element 12.

  The other switch 15 dimensions, that is, the length of the L ′ side of the switch 15 connecting P1-P2 is PL or less, the length of the L ′ side of the switch 15 connecting the feeding element-P3 is L or less, P1 -The length on the W 'side of the switch 15 to which the feeding element is connected may be W or less, and the length on the W' side of the switch 15 to which P2-P3 is connected may be PW or less.

The relationship between the equations (14) and (15) is only one condition for the outer shape of the rectangular radiating element 16 and the feeding element 12 connected by the switch 15 to satisfy the equation (13). It is not limited to (14) Formula and (15) Formula.
L / W = L '/ W'
As long as the outer shape of the parasitic element 14, the interval between the feeder element 12 and the parasitic element 14, and the interval between the parasitic elements 14 are adjusted, the present invention includes the present invention.

  Also in this example, it is preferable to use a MEMS switch or a PIN diode as the switch 15 for connecting the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14.

<Example 5>
FIG. 8 is a diagram showing another example of the multiband-compatible circularly polarized microstrip antenna of the present invention.

  The multiband-compatible circularly polarized microstrip antenna of this example has a ground plate (not shown) made of an Au foil pattern formed on the lower surface of a dielectric 10 made of an alumina substrate having a relative dielectric constant of about 10. A rectangular feeding element 12 made of an Au foil pattern is disposed on the upper surface, and the feeding element 12 is fed at one vertex of a rectangle by a feeding line 130 formed of a microstrip line provided on the dielectric 10. The power is supplied from 131.

  In addition, the rectangular parasitic elements 14 surrounding the two sides constituting the apex facing the feeding point 131 of the feeding element 12 are arranged in a double matrix.

  Here, the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14 can be connected to each other by the switch 15, and two sides constituting the vertex of the feeding element 12 facing the feeding point 131 are defined as 1 side. The rectangular parasitic element 14 and the switch 15 that connect the feeder element 12 that are surrounded by the overlap, and the rectangular parasitic element 14 that surrounds the two sides that form the apex opposite to the feeding point 131 of the feeder element 12 are connected. When the switch 15 to be turned on is formed, a first rectangular radiating element 161 (the outer shape is L ′ × W ′) is formed. When all the switches 15 are turned on, the second rectangular radiating element 162 is formed. (External dimension is L ″ × W ″).

The feature of the present invention is that
L / W = L '/ W'
The shape of the rectangular radiating element in relation to the above can be taken by a plurality of the switches 15 connecting the feeding element 12, the parasitic element 14, and the adjacent parasitic elements 14.

In this example, the first radiating element 161 connected by the switch 15 and the second radiating element 162 connected by the switch 15 are connected to the feeding element 12.
L / W = L '/ W'
Is in a relationship.

In other words, the rectangular parasitic element 14 that surrounds the two sides constituting the vertex facing the feeding point 131 of the feeding element 12 in a single layer, the switch 15 that connects the feeding element 12, and the feeding point 131 of the feeding element 12 are opposed. L of the first rectangular radiating element 161 (the outer shape is L ′ × W ′) formed when the switch 15 connecting the rectangular parasitic elements 14 surrounding the two sides constituting the apex in a single layer is turned on. The length of the side corresponding to the side is L ′, the length of the side corresponding to W is W ′, and the rectangular parasitic power supply surrounding the two sides constituting the vertex facing the feeding point 131 of the feeding element 12 in a single layer. When the switch 15 that connects the element 14 and the feed element 12 and the switch 15 that connects between the rectangular parasitic elements 14 that surround the two sides forming the apex opposite to the feed point 131 of the feed element 12 are turned on. That is, all the switches 15 are ON The length of the side corresponding to the L side of the second rectangular radiating element 162 (the outer shape is L ″ × W ″) formed in this case is L ″ and the length of the side corresponding to W is W ''
L / W = L '/ W' = L '' / W '' (16)
It has become. The first rectangular radiating element 161 and the second rectangular radiating element 162 also use the same feeding point 131 as the feeding element 12 as the feeding point.

  In this embodiment, the first radiating element 161 connected by the switch 15 is twice as large as the feeding element 12, and L ′ = 2L, W ′ = 2W, and the second radiating element 162 connected by the switch 15 is The size is three times as large as that of the feeding element 12, and L ″ = 3L and W ″ = 3W.

  When all the switches 15 are OFF, the power feeding element 12 alone resonates. When the rectangular feeding element 12 is fed from the apex, two modes orthogonal to the L side and the W side are excited. Here, if the ratio of the lengths of L and W is appropriately selected, the phase difference between the two orthogonal modes becomes 90 degrees, and circular polarization can be realized. Let the resonant frequency at that time be f.

  Since the first rectangular radiating element 161 and the second rectangular radiating element 162 connected by the switch 15 satisfy the equation (16), the outer shape and the relative position of the feeding point are similar to those of the feeding element 12.

  Since each side (L ′, W ′) of the first rectangular radiating element 161 connected by the switch 15 is twice the side (L, W) of the feeding element 12, circular polarization of about f / 2. Radiate. Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into account, so that it slightly deviates from f / 2.

  Further, in the second rectangular radiating element 162 connected by the switch 15, each side (L ″, W ″) is three times the side (L, W) of the feeding element 12, and therefore, about f / 3. Radiates circularly polarized waves. Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into consideration, and therefore, it slightly deviates from f / 3.

  Therefore, the antenna of this example can selectively radiate three-frequency circularly polarized waves by turning the switch 15 on and off. Further, since the antenna area may be the antenna area corresponding to the lowest frequency, the antenna can be miniaturized.

  Further, since the feeding element 12 and the first radiating element 161 are included in the second radiating element 162, the second rectangular radiating element 162 is placed in an area in the best radio wave condition on the wireless device to feed power. The element 12 and the first radiating element 161 can be placed in a favorable radio wave condition. Further, since the feed element 12, the first radiating element 161, and the second radiating element 162 have a simple circularly polarized microstrip antenna structure, the same radiation pattern is obtained.

  Further, since the antenna of this example can be fed with a microstrip line as in the fourth embodiment, it can be easily connected to the RF circuit.

Next, the input impedance of the antenna of this example will be described.
When all the switches 15 are turned off to resonate only with the power feeding element 12, since the power feeding element 12 is fed from the antenna end, the input impedance Za affects the ratio (L / W) of the two sides constituting the power feeding element 12. Is done.

  On the other hand, the first rectangular radiating element 161 and the second rectangular radiating element 162 have substantially rectangular outer shapes and are fed from the apex, so that the input impedance is the length of two sides (L '/ W') and (L '' / W ''). Strictly speaking, the influence of the air gap surrounded by the switch 15 must be taken into account, but the input impedance is not greatly changed.

Here in this example
L / W = L '/ W' = L`` / W ''
Therefore, the input impedance Za ′ of the first radiating element 161 connected by the switch 15 and the input impedance Za ″ of the second radiating element 162 are substantially close to the input impedance Za of the feeder element 12 alone. Become.

  Therefore, when the feed line 130 is configured using a characteristic impedance equal to the input impedance Za of the feed element 12, the first radiating element 161 and the second radiating element 162 connected by the switch 15 also resonate. Since the input impedances Za ′ and Za ″ are close to the characteristic impedance of the feeder line, reflection is suppressed and radio waves can be transmitted or received efficiently.

  Therefore, unlike US Pat. No. 6,198,438 (Patent Document 4), there is no need to switch the feeding point for each frequency, and only the feeding point 131 of the feeding element 12 can cope with three frequencies.

Also in this example, as in the fourth embodiment, the outer shape of the parasitic element 14, the distance between the feeding element 12 and the parasitic element 14, and the distance between the parasitic elements 14 are adjusted.
L / W = L '/ W' = L`` / W ''
It was. Further, a MEMS switch or a PIN diode is suitable for the switch 15 that connects the feeding element 12 and the parasitic element 14 and the adjacent parasitic element 14.

  In the fourth embodiment, the circularly polarized antenna corresponding to two frequencies and the present example corresponding to three frequencies have been described. However, the antenna of the present invention is not limited to two frequencies or three frequencies.

When dealing with a larger number of frequency bands, the two sides constituting the apex opposite to the feeding point of the feeding element 12 are more surrounded by the rectangular parasitic element 14, and the feeding element 12, the parasitic element 14, A structure in which the elements 14 can be connected by the switch 15 and each frequency of the multiband,
L / W = L '/ W'
The outer shape of the parasitic element 14, the distance between the feeding element 12 and the parasitic element 14, the distance between the parasitic elements 14, and the like may be adjusted.

<Example 6>
FIG. 9 is a diagram showing another example of the multiband-compatible circularly polarized microstrip antenna of the present invention. The multiband-compatible circularly polarized microstrip antenna of this example has a matching circuit 18 provided at the feeding point 131 of the antenna of the fourth embodiment.

  A feed line 130 having a characteristic impedance of 50 Ω, which is composed of a microstrip line on the surface of SiO 2 under the ground plane 11, is connected to the matching circuit 18 through the via hole 20, and then connected to the feed point 131 at the apex of the feed element 12. . The other of the feeder line 130 is connected to an RF circuit (not shown).

  The multiband circularly polarized microstrip antenna of the fourth embodiment is fed from the top of the antenna. Therefore, the characteristic impedance of the feeder 130 must be close to the input impedance Za of the feeder element 12 and the input impedance Za ′ of the rectangular radiating element 16 connected by the switch 15.

  However, the input / output impedance of the PA, LNA, mixer, etc. constituting the RF circuit is 50Ω, and when used as it is in the antenna of the fourth embodiment, the reflection becomes large, and radio waves cannot be efficiently received / transmitted.

  In this example, the input impedances Za and Za ′ of the radiating element 16 connected by the feed element 12 and the switch 15 are matched with the characteristic impedance of the feed line 130 by the matching circuit 18 and then connected to the RF circuit. Reflection between circuits can be suppressed, and radio waves can be received and transmitted efficiently.

In addition, in Example 4, the radiating element 16 connected by the switch 15 is:
L / W = L '/ W'
However, the current in the antenna is limited by the gap surrounded by the switch 15, and the input impedance Za ′ of the rectangular radiating element 16 slightly deviates from Za of the feeding element 12.

  For this reason, in the fixed matching circuit that matches the input impedance Za of the power feeding element 12 to 50Ω, the radiating element 16 connected by the switch 15 cannot be perfectly matched, and the efficiency of transmission / reception of radio waves slightly decreases. In order to improve the transmission / reception efficiency of the radiating element 16 connected by the switch 15, a variable matching circuit 18 including one or more variable capacitors and variable phase shifters is provided, and the radiating element 16 connected by the switch 15 is also 50Ω. It is necessary to be consistent with.

  The matching circuit 18 used in this example is the same as that of the second embodiment. Specifically, the lumped constant circuit in which the lumped constant elements of capacitors and inductors are configured in L type, π type, and T type, and the distribution of stubs, etc. A circuit in which a constant circuit is configured in an L-type, π-type, or T-type, a matching circuit using a phase shifter and a capacitor, or the like may be used depending on the resonance frequency of the antenna.

Next, an example of improving the switch shape will be described.
FIG. 10 is a diagram for explaining an improved switch.
As shown in FIG. 10, the switch 151 of the present example has a structure that conducts or cuts off between almost the entire sides between the adjacent rectangular feeding elements 12 and the parasitic elements 14 and between the parasitic elements 14.

  By adopting the shape of the switch 151 as shown in FIG. 10, the space surrounded by the four switches 151 inside the radiating element 16 becomes smaller than in the case of FIG. Therefore, the band of the radiating element can be expanded as compared with the case of FIG.

FIG. 11 is a diagram showing a switch shape that further reduces the gap.
In this example, as shown in the figure, the tip of the four switches 151 facing each other is extended to a V shape so that the gap between the four switches 151 becomes an X shape. The void surrounded by 151 can be substantially eliminated, and the band can be further expanded, which is effective in improving the characteristics.

  Needless to say, the shape of the switch shown in FIGS. 10 and 11 is applicable to other embodiments of the present invention.

<Example 7>
FIG. 12 is a diagram illustrating an example of a transmission / reception wireless system according to the present invention.
This example is a radio system capable of transmitting and receiving dual bands corresponding to right-hand circularly polarized 1.575 GHz GPS and 5.8 GHz ETC, and has the same configuration as that of the first embodiment (dual-band compatible microstrip antenna). 30 is used.

A matching circuit 31 is provided between the antenna 30 and the transmission / reception selector switch 33 by a π-type lumped constant circuit composed of C, L, and C connected by a selector switch 32.

  When resonance occurs only at the power feeding element 12 and supports 5.8 GHz, the changeover switch 32 is turned off (switched to the side not passing through the matching circuit 31), and the power feeding element 12 is connected to the front end circuit via the transmission / reception changeover switch 33. 50 is directly connected.

  In addition, when the feed element 12 and the parasitic element 14 and the adjacent parasitic elements 14 are connected by the switch 15 to form the rectangular radiating element 16 and resonate at 1.575 GHz, the changeover switch is turned ON (matching circuit). The rectangular radiating element 16 is connected to the front-end circuit 50 via the matching circuit 31 that matches the input impedance of the radiating element 16 to 50Ω and the transmission / reception selector switch 33.

Next, the transmission / reception operation will be specifically described.
In the case of 5.8 GHz (ETC) compatibility, all of the power supply element 12, the parasitic element 14, and the switch 15 between the adjacent parasitic elements 14 are turned off, and excitation is performed using only the rectangular power supply element 12. For reception at 5.8 GHz, the changeover switch 32 is turned off (switched to the side not passing through the matching circuit 31), and the matching circuit is cut off from the feeder line.

  Further, the transmission / reception selector switch 33 is set to the receiving side, and only the frequency selection switch SW1 (34) among the frequency selection switches SW1 to SW4 is turned on, and the others are turned off.

  A signal received by the power feeding element 12 enters the reception-side front-end circuit 50 through the transmission / reception selector switch 33 and enters the 5.8 GHz side through the frequency selection switch SW1 (34).

  The signal is amplified by the LNA 36, the band is limited by the BPF 37, down-converted by the mixer 38 to an intermediate frequency, and then sent to the baseband circuit. On the other hand, in the transmission at 5.8 GHz, the changeover switch 32 is turned OFF and the matching circuit is cut off from the feeder line.

  Further, the transmission / reception change-over switch 33 is set to the transmission side, and in the frequency selection switches SW1 to SW4, only the frequency selection switch SW4 (46) is turned on, and the others are turned off.

  The signal generated by the baseband circuit is up-converted to an intermediate frequency and then up-converted to 5.8 GHz by the mixer 41. Thereafter, the band is limited by the BPF 43, amplified by the PA 44, and radiated as a radio wave from the power feeding element 12 through the frequency selection switch SW 4 (46) and the transmission / reception selector switch 33.

  In correspondence with 1.575 GHz (GPS), the power supply element 12, the parasitic element 14, and the switch 15 between the adjacent parasitic elements 14 are all turned on to form a rectangular radiation element. For reception at 1.575 GHz, the changeover switch 32 is turned on (switched to the side through which the matching circuit 31 is passed) and the matching circuit is connected to the feeder line.

  Also, the transmission / reception selector switch 33 is set to the receiving side, and only the frequency selection switch SW2 (35) is turned on in the frequency selection switches SW1 to SW4, and the others are turned off.

  A signal received by the power feeding element 12 enters the reception-side front end circuit 50 through the matching circuit 31 and the transmission / reception selector switch 33, and enters the 1.575 GHz side through the frequency selection switch SW2 (35). The signal is amplified by the LNA 36, the band is limited by the BPF 37, down-converted by the mixer 38 to an intermediate frequency, and then sent to the baseband circuit.

  On the other hand, in the transmission at 1.575 GHz, the changeover switch 31 is turned ON (switched to the side through which the matching circuit 31 is passed), and the matching circuit 31 is connected to the feeder line.

  The transmission / reception selector switch 33 is on the transmission side, and only the frequency selection switch SW3 (45) is turned on in the frequency selection switches SW1 to SW4, and the others are turned off.

  The signal generated by the baseband circuit is up-converted to an intermediate frequency and then up-converted to 1.575 GHz by the mixer 41.

  Thereafter, the band is limited by the BPF 43, amplified by the PA 44, and radiated as a radio wave from the power feeding element 12 through the frequency selection switch SW 3 (45), the transmission / reception selector switch 33, and the matching circuit 31. The axial ratios at 5.8 GHz and 1.575 GHz were 3 dB or less, and the two frequencies were good circularly polarized waves.

  As described above, in the wireless system of this example, in the case of 5.8 GHz, only the feeding element 12 is excited, and in the case of 1.575 GHz, the feeding element 12, the parasitic element 14, and the adjacent parasitic element 14 are connected. All the switches 15 are turned on and excited by the rectangular radiating element 16, so that two wireless standards can be supported.

  In addition, since the matching circuit 31 is connected to the antenna and the input impedance of the antenna can be matched to 50Ω, the reflection at the antenna 30 and the front end circuit 50 can be suppressed in the 1.575 GHz compatible. As a result, the S / N of the signal can be increased, and good transmission / reception can be performed even at 1.575 GHz.

  Further, the antenna of this example has one feeding point, and the antenna structure is simpler than that of US Pat. No. 6,198,438 (Patent Document 4), so that the antenna can be manufactured at a lower cost. As a result, a wireless system compatible with circular polarization having good transmission / reception or transmission / reception characteristics can be manufactured at a lower cost.

  In this example, the two-frequency radio system has been described. However, if the antennas of the second and fifth embodiments are used and the front-end circuit of the reception system / transmission system corresponding to each frequency band is provided, the circular polarization corresponding to the three frequencies. A wireless system can be configured.

  Furthermore, as described in the second embodiment, an antenna corresponding to four or more frequencies can be used in the present invention, and a multiband radio system capable of supporting more frequencies can be configured by using such an antenna.

  In this example, a wireless system capable of transmitting and receiving has been described. However, a wireless system only for transmission and reception is included in the present invention if it is compatible with multiband.

It is a figure which shows an example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is explanatory drawing in the case of carrying out inset electric power feeding of a microstrip antenna. FIG. 3 is a diagram for explaining dimensions of the microstrip antenna of Example 1. It is a figure which shows another example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is a figure which shows another example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is a figure which shows another example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is a figure for demonstrating the dimension of the microstrip antenna of Example 4. FIG. It is a figure which shows another example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is a figure which shows another example of the multiband-compatible circularly polarized microstrip antenna of this invention. It is a figure for demonstrating the improved switch (what enlarged the area). It is a figure for demonstrating the shape of the improved switch (what made the opposing part V shape). It is a figure which shows an example of the radio | wireless system of this invention. It is a figure which shows a prior art example (Unexamined-Japanese-Patent No. 2000-236209). It is a figure which shows a prior art example (Unexamined-Japanese-Patent No. 2002-261533). It is a figure which shows a prior art example (Unexamined-Japanese-Patent No. 2003-124730). It is a figure which shows a prior art example (US Pat. No. 6,198,438).

Explanation of symbols

10: Dielectric 11: Ground plane 12: Rectangular feeding element 13: Feeding point 130: Feeding line 131: Top feeding point 14: Parasitic element 15, 151: Switch 16: Rectangular radiating element 161: First rectangular Radiating element 162: second rectangular radiating element 17: coaxial line 18: matching circuit 181, 182: changeover switch 19: RF circuit 20: via hole 30: antenna (dual-band compatible microstrip antenna)
31: Matching circuit 32: Changeover switch 33: Transmission / reception changeover switch 34: Switch SW1
35: Switch SW2
36, 44: PA
37, 43: BPF
38, 41: Mixer 39: 5.8 GHz transmitter 40: 1.575 GHz transmitter 42: 5.8 GHz transmitter 45: Switch SW3
46: Switch SW4
50: Front-end circuit 60: GPS / ETC shared wireless system 101: Metal piece 102: PIN diode 211: Antenna unit 212: Wiring board 213: Ground pattern 214: RF module 218: Antenna element pattern 219: Feed point (feed pattern)
220a to 220d: grounding points 221a to 221d: switch 300: antenna structure 305: short-circuit plane 310: sub-antenna structure 320: first radiating element 322: first end 324: feed line 330: second radiating element 332 : Second end 334: spacing 340: third radiating element 342: third end 350: feed line 360, 362: switch 370, 372: radio frequency module A 1, A 2: aperture 400: radiating element 405: High frequency feed point 410: Low frequency feed point 420: MEMS switch

Claims (12)

A rectangular feeding element having a feeding point on a diagonal line on the upper surface of the dielectric, and a rectangular parasitic element surrounding the feeding element are arranged in a matrix, and the feeding element, the parasitic element, and the adjacent parasitic element In a multiband-compatible circularly polarized microstrip antenna having a structure in which elements are connected by a switch to form a rectangular radiating element,
The length of one side of the rectangular feeding element is L, the length of the other side is W, the smaller of the distances between the two sides on the W side and the feeding point is Li, the two sides on the L side and the side The smaller of the distance to the feeding point is Wi, the length of the side corresponding to the L side of the sides of the rectangular radiating element connected by the switch is L ′, the rectangular radiating element connected by the switch Of the sides, the length of the side corresponding to the W side is W ′, the smaller of the distances between the two sides on the W ′ side and the feeding point is Li ′, the two sides on the L ′ side and the feeding point If the smaller of the distances is Wi ',
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
A multiband-compatible circularly polarized microstrip antenna. In the multiband-compatible circularly polarized microstrip antenna according to claim 1,
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
It is possible to form a plurality of the rectangular radiating elements having a relationship with each other by the switch that connects between the feeding element, the parasitic element, and the adjacent parasitic element. Multi-band circularly polarized microstrip antenna. The multiband-compatible circularly polarized microstrip antenna according to claim 1 or 2,
L / W = L '/ W'
Li / L = Li '/ L'
Wi / W = Wi '/ W'
The multiband-compatible circularly polarized microstrip antenna, wherein the external shape of the parasitic element, the interval between the feeder element and the parasitic element, and the interval between the parasitic elements are adjusted so that In the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 3,
A multi-band circularly polarized microstrip antenna having a matching circuit connected to the feeding point by a changeover switch. A rectangular feed element is provided on the top surface of the dielectric, and the feed element is fed from one vertex of the rectangle and has a rectangular parasitic element surrounding two sides constituting the vertex facing the feed point of the feed element. A multiband-compatible circularly polarized microstrip antenna that is arranged in a matrix and has a structure in which a rectangular radiating element is formed by connecting the feeding element and the parasitic element, and the adjacent parasitic element by a switch. ,
The length of one side of the rectangular feeding element is L, the length of the other side is W, the length of the side corresponding to the L side of the sides of the rectangular radiating element connected by the switch is L ′, When the length of the side corresponding to the W side among the sides of the rectangular radiating elements connected by the switch is W ′,
L / W = L '/ W'
A multiband-compatible circularly polarized microstrip antenna. The multiband-compatible circularly polarized microstrip antenna according to claim 5,
L / W = L '/ W'
A rectangular radiation element having a relationship with a multi-element can be formed by a plurality of the power supply element, the parasitic element, and the switch connecting adjacent parasitic elements. Band-compatible circularly polarized microstrip antenna. The multiband-compatible circularly polarized microstrip antenna according to claim 5 or 6,
L / W = L '/ W'
The multiband-compatible circularly polarized microstrip antenna, wherein the external shape of the parasitic element, the interval between the parasitic element and the parasitic element, and the interval between the parasitic elements are adjusted so that In the multiband-compatible circularly polarized microstrip antenna according to claim 5-7,
A multiband-compatible circularly polarized microstrip antenna, wherein a matching circuit is provided at the feeding point. In the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 8,
The multiband-compatible circularly polarized microstrip antenna, wherein the switch is at least one of a MEMS switch and a PIN diode. In the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 9,
The multiband-compatible circularly polarized microstrip antenna, wherein the switch is formed over substantially the same length as a side of the feeding element or the parasitic element. In the multiband-compatible circularly polarized microstrip antenna according to any one of claims 1 to 9,
In each of the switches, the shape of the tip portion facing the other switch is extended to a V shape, and the gap between the four switches facing each other is made an X shape. Wave microstrip antenna.   A wireless system using the multiband-compatible circularly polarized microstrip antenna according to claim 1.

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