JP2008028734A - Surface mounting antenna and communication apparatus mounting it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna which is used in the case to mount a plurality of bands on one portable terminal apparatus and obtains a high gain and a non-directional property in a wide bandwidth. <P>SOLUTION: A small-sized surface mounting antenna to make impedance matching easy and to have the high gain and the non-directional property in the wide bandwidth thereby is obtained by making a radiation electrode of the antenna line-symmetrical with regard to a symmetrical axis of its shape and by giving an impedance matching function with an inductance other than each capacitance between the radiation electrode and a ground electrode, between the radiation electrode and a power feeding electrode and to the radiation electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a small antenna based on a dielectric or magnetic material using ceramics, resin, or the like as a base material, and in particular, a surface-mounted antenna provided with a symmetrical antenna element shape and separately provided with an impedance matching function, and the like. It relates to communication equipment.

  In the field of mobile terminal devices that use UHF radio waves as a carrier wave, there is a need for a technology that can use multiple bands such as GSM, DCS, PCS, and UMTS bands in a single mobile terminal device. A surface mount antenna is used for an antenna circuit used in the portable terminal device. Miniaturization and multibanding of portable terminal devices are progressing at a rapid speed, and surface-mounted antennas are also required to have good radiation efficiency over a wide band and be non-directional. However, conventional surface mount antennas are not always satisfactory for realizing sufficient gain and omnidirectional characteristics in a wide band because the antenna gain decreases and the directivity is disturbed at a particularly high frequency when used in a wide band. It wasn't. This is because it is difficult to achieve impedance matching between the antenna and the transmitter circuit in order to obtain sufficient gain and omnidirectional characteristics in multiple bands in a wide band, and further miniaturization to solve the problem of impedance matching. Was more difficult.

  For example, a surface-mounted antenna described in Japanese Patent Application No. 2001-295743 discloses an antenna in which the radiation electrode is provided substantially symmetrically with respect to the central portion. This antenna can maintain omnidirectionality because the main polarization direction is aligned due to the substantially symmetry of the radiation electrode. However, impedance matching on the feeding side of the radiating electrode is performed by adjusting the position where the feeding conductor line is connected to the radiating electrode, how the feeding conductor line is routed, and the distance between them. There were an infinite number of combinations, and the performance had to be verified with many patterns to find the optimum point. On the other hand, the grounding point side of the radiation electrode is not directly connected but is coupled only by capacitance, and inductance is not used for impedance matching. For this reason, when the antenna is reduced in size and height, impedance matching is difficult to achieve. As a result, there has been a problem that a high-performance antenna cannot be obtained in a wide band.

  Further, for example, a surface-mounted antenna described in Japanese Patent Application Laid-Open No. 2003-179426 discloses an antenna in which a resonance circuit is inserted only between a power feeding unit of the antenna and a radio circuit. However, in this case, since the resonance circuit is only between the power feeding unit and the radio circuit, it is easy to achieve impedance matching in a specific band, but impedance matching can be achieved without degrading antenna performance in a plurality of bands. difficult. As a result, if the antenna gain and omnidirectionality are maintained, it will be difficult to achieve a wide band. In particular, if the band is widened, nulls are likely to occur, and the omnidirectionality will be maintained. There was a problem of becoming difficult.

Japanese Patent Application No. 2001-295743

JP 2003-179426 A

  In the conventional surface mount antenna, when a plurality of bands are mounted on one portable terminal device, impedance matching is easy while being small and low in profile, and a broadband antenna with high antenna characteristics cannot be obtained. However, an antenna used for a cellular phone or the like needs to have a wide band and a high gain and maintain omnidirectionality. Conventionally, consideration and examination on this point have not been sufficient. An object of the present invention is to make the shape of the radiation electrode line-symmetric with respect to the axis of symmetry, provide an impedance matching portion by capacitance and inductance between the ground end of the radiation electrode and the ground electrode, and In addition, an impedance matching portion is provided between the capacitor and the inductance, and the antenna has a matching function between the capacitance and the inductance in the shape of the radiation electrode. An object of the present invention is to provide a surface mount antenna that is suitable for a mobile phone or the like mounted on a communication device, and has high gain and omnidirectionality in a wide band. Another object of the present invention is to provide a communication device for a headphone, a personal computer, a notebook computer, a digital camera or the like equipped with this surface mount antenna.

  As a result of diligent research in view of the above object, the impedance matching function has the radiation electrode symmetrical with respect to the axis of symmetry of the shape, and has inductance in addition to capacitance between the radiation electrode and the ground electrode and between the radiation electrode and the feeding electrode. Thus, the present inventors have found that a small surface-mount antenna having impedance matching, high gain and omnidirectional characteristics in a wide band can be obtained.

  A radiation electrode provided on at least the upper surface of the circuit board, a ground electrode provided on the circuit board so as to face one end of the radiation electrode, and provided on the circuit board so as to face the other end of the radiation electrode The radiation electrode is line symmetric with respect to the axis of symmetry of the shape, one end of the radiation electrode is a ground end, and the other end is a feed end, A load having an impedance matching portion which is a loading element configured by capacitance and inductance between the ground end and the ground electrode, and is also configured by capacitance and inductance between the power supply end and the power supply electrode. It has the impedance matching part which is an element, It is characterized by the above-mentioned. This impedance matching section is composed of one port, and is preferably connected to the grounding end and the feeding end of the radiation electrode.

  In this invention, it is preferable that the said radiation electrode is an antenna which consists of a conductor pattern provided in the surface of the plate-shaped or substantially rectangular parallelepiped base | substrate mounted in the said circuit board. The shape of the substrate is not limited to a substantially rectangular parallelepiped shape, and the cross-sectional shape is a U shape, a B shape, an L shape, a trapezoidal shape, or a cross section shape in the longitudinal direction of the substrate is a U shape, a B shape, There are appropriate shapes such as arcs. The base material may be a magnetic material, a dielectric material, or a laminate thereof. Here, since the substrate is a magnetic material or a dielectric, the dielectric constant is increased by using the substrate, and when the radiating electrode made of a conductor pattern is wound around the substrate, the entire length of the radiating electrode is longer than when the substrate is not used. The length can be shortened. Therefore, the entire antenna can be reduced. The radiation electrode may be an antenna formed of a conductor pattern provided on a sub-board placed on the surface of the circuit board. The radiation electrode is disposed in a region where no ground conductor exists through a gap with respect to an edge of the ground conductor on the transmission / reception circuit side of the circuit board, and the feeding electrode is disposed on the transmission / reception circuit side. preferable.

  In another preferred embodiment of the present invention, it is preferable that impedance matching can be performed by adjusting capacitance and inductance by changing the shape and position of the radiation electrode. The radiating electrode has a loop shape and has a shape that is line symmetric with respect to the symmetry axis of the shape, and a part of the radiating electrode of the loop has any of a U shape, a U shape, or a crankshaft shape. It is preferable to have an impedance matching function by the capacitance between the opposing radiation electrodes in this portion and the inductance due to the length of the radiation electrode. The length of the radiation electrode is preferably 1/2 or 1/4 wavelength of the radio wave used for transmission / reception.

  In another preferred embodiment of the present invention, one end of the radiation electrode is a ground end, the other end is a power supply end, and an impedance matching unit with capacitance and inductance between the ground end and the ground electrode; The impedance matching portion by capacitance and inductance between the power supply end and the power supply electrode is formed on the surface of the circuit board with a conductor pattern. If the antenna is mounted on the circuit board surface without the ground conductor of the circuit board, the maximum characteristics can be expected, but the antenna performance is slightly inferior, but it can be mounted on the ground conductor surface.

  As described above, according to the present invention, when a plurality of bands that could not be realized in the past are mounted on one device, impedance matching is easy while being small and low-profile, and high gain and omnidirectionality are achieved in a wide band. An antenna device can be obtained. In addition, when used for not only a mobile phone but also a GPS, a wireless LAN, or the like, it is possible to provide a mobile communication device that sufficiently draws out the performance of the device.

  Hereinafter, the present invention will be described in detail with embodiments shown in the drawings. First, the reason why impedance matching becomes difficult will be described. When a radiation electrode, a ground electrode, a power supply electrode, and the like are arranged on the substrate, a capacitance is generated between the electrodes. Increasing the capacitance between the feed electrode and the radiating electrode lowers the input impedance and causes impedance mismatch.

  FIG. 1 shows an example of an embodiment of an antenna device which is a two-port antenna in which a radiation electrode is formed in a conductor pattern on a circuit board of the present invention, and impedance matching portions as loading elements are connected to both ends of the radiation electrode. FIG. In FIG. 1, 2A denotes an antenna device which is a 2-port type conductor pattern antenna, and 24 denotes a loading element. FIG. 17 is a diagram illustrating an example of the loading element 24.

  In the two-port antenna device having the impedance matching portion port which is a loading element at the grounding end and the feeding end of the radiation electrode of this embodiment, the radiation electrode 22 is placed in the region 1a of the circuit board 1 where the ground conductor does not exist. The conductor pattern is printed and formed in line symmetry with respect to the symmetry axis m of the shape. Therefore, the antenna device is connected to the radiation electrode 22 formed in a conductor pattern in the region 1 a where no ground conductor exists, the loading element 24 b connected to the ground end 23 b of the radiation electrode 22, and the feeding end 23 a of the radiation electrode 22. And a loading element 24a. The loading element 24b is an impedance matching portion due to capacitance and inductance between the ground end 23b and the ground electrode 25b, and the loading element 24a is an impedance matching portion due to capacitance and inductance between the feeding end 23a and the feeding electrode 25a. is there. The position and shape of the radiation electrode 22 are determined by impedance matching so that sufficient gain and omnidirectionality can be obtained in each frequency band. In this case, the area 1a where the ground conductor does not exist and the circuit board 1 can have substantially the same thickness, and the height of the portable communication device using the present invention can be significantly reduced.

  In this example, capacitance and inductance elements are shown as loading elements. However, the loading elements can also be a conductor pattern printed on the circuit board. In this case, the board is also printed on the portion where the loading elements are printed. The thickness can be made substantially the same, and the height of the portable communication device according to the present invention can be greatly reduced.

  The antenna device of the two-port system according to the present invention is configured such that the radiation electrode is formed line-symmetrically with respect to the symmetry axis of the shape, and the impedance matching portion by capacitance and inductance is provided between the ground end which is one end of the radiation electrode and the ground electrode. The impedance matching is achieved by inserting an impedance matching portion based on capacitance and inductance between the feeding end and the feeding electrode, which is the other end of the radiation electrode. In the conventional antenna of this type, only the capacitance on the equivalent circuit is provided. However, according to the present invention, the loading element that can acquire the inductance in addition to the capacitance on the equivalent circuit is provided between one end of the radiation electrode and the ground electrode and between the radiation electrode. One of the major features of the present invention is that impedance matching is made easier in a wide band by mounting between the other end and the feeding electrode.

Further, since the two-port antenna device of the present invention has various forms depending on the application, the impedance matching condition needs to satisfy these extensive requirements. For this reason, since the radiation electrode can be regarded as a combination of the parallel component L _i (i = 1, 2, 3) of the inductance and the parallel component C _{i of the} capacitance, the radiation electrode is formed in a loop shape and further in the middle of the radiation electrode. Inductance and capacitance can be arbitrarily set by forming a radiating electrode portion having a U-shape, U-shape, crankshaft shape, or a combination thereof. Inductance is proportional to the length of the radiating electrode, and capacitance is a function of the opposing length of the ground electrode and the radiating electrode, or the radiating electrode and another portion of the radiating electrode. Therefore, when impedance matching is performed using the radiation electrode of the present invention, first, it is roughly determined which one of L _i and C _{i in} the equivalent circuit should be. Next, L _i is proportional to the length of the radiating electrode, and C _i is a function of the opposing length of the radiating electrode and the ground electrode or the radiating electrode and another portion of the radiating electrode. Therefore, it is possible to easily set the shape of the radiation electrode that satisfies the desired parameters.

  In order to determine the overall length of the antenna, which is the 2-port antenna device of the present invention, the shape of the bent portion, the length, etc., considering the impedance matching conditions as described above, the resonance frequency of the antenna in each frequency band is It is necessary to decide. First, the overall length of the discharge electrode formed in a loop shape is determined, and it is set to a length that resonates at a quarter wavelength in the GSM band which is a low frequency band. Next, in the radiation electrode formed in a loop shape, a U-shaped or U-shaped bent portion is provided at a position that is substantially symmetrical with respect to the center point of the shape. On the other hand, the length of the discharge electrode obtained by short-passing the radiation electrode portion having the bent shape is made to be a length that resonates at a ½ wavelength in the DCS / PCS band of the high frequency band. The total length is determined excluding the radiation electrode part. As a result, the basic antenna length condition for resonating in a plurality of bands can be determined.

  On the other hand, in order to efficiently radiate radio waves from the radiation electrode in the air without causing a disturbance of directivity, that is, without causing a null point, the impedance at the ground end of the radiation electrode is high impedance when used in the GSM band. Therefore, when used in the DCS / PCS band, the impedance becomes low impedance (characteristic impedance: 50Ω), and both the GSM band and the DCS / PCS band need to have low impedance at the feeding end of the radiation electrode. In order to achieve impedance matching in this manner, after determining the overall length of the radiation electrode and the shape of the bent portion, first the transmitter / receiver circuit is operated in the GSM band and the transmitter / receiver circuit in the DCS / PCS band is set to have high impedance at the ground end. The L and C of the loading element inserted between the ground point end and the ground electrode are adjusted so as to be low impedance at the ground end, and the values of L and C are roughly determined. However, at the stage where the values of L and C are determined, there is a match at the ground end, but there is a shift in impedance at the feed end. Therefore, when high-frequency power from the transmission / reception circuit is transmitted to the power supply electrode via the power supply line of the circuit board, it is necessary to prevent voltage reflection from occurring at the power supply end, but both the GSM band and the DCS / PCS band are low. The values of L and C are determined by adjusting L and C of the loading element inserted between the power supply end and the power supply electrode again and again so as to be impedance. A standard for achieving this matching is that the voltage standing wave ratio (hereinafter referred to as VSWR) is about 3 or less in the target frequency band.

  Furthermore, in the present invention, not only the length and shape of the radiation electrode are set appropriately, but also a U-shape or U-shape on the radiation electrode formed in a loop shape at a position that is line symmetric with respect to the symmetry axis of the shape. A portion having a bent shape is provided, and impedance matching in a plurality of bands is facilitated by increasing / decreasing L and C formed in the bent portion, whereby the bandwidth BW can be arbitrarily set. Since L and C formed in the bent portion can be regarded as parallel resonance, BW∝1 / Q and Q = 1 / R√ (C / L) between the bandwidths BW and Q and C / L. There is a relationship, and if C or C / L is controlled by increasing or decreasing L and C formed in the bent portion, the bandwidth BW can be widened. For example, if the portion where the conductor pattern of the bent portion is opposed is lengthened, the inductance (L) and capacitance (C) can be increased. Further, if the part of the conductor pattern that forms the bent shape is separated, the inductance (L) can be increased, but the capacitance (C) can be decreased. As a result, impedance matching can be facilitated even in a wide band including up to the UMTS band, which is a slightly higher frequency band than the DCS / PCS band. Therefore, the four bands of the GSM band, the DCS / PCS band, and the UMTS band can be reduced. An antenna having high gain and omnidirectionality in a wide band including the antenna can be obtained. That is, the conductor pattern antenna which is the antenna device 2A according to the present invention has an equivalent circuit shown in FIG.

  FIG. 3 is a plan view showing a state in which an antenna device 2B composed of a chip antenna using the two-port type substrate described in the second embodiment of the present invention is mounted. This antenna includes a radiation electrode 22 disposed on the upper surface of a rectangular parallelepiped base 21, a loading element 24b connected to the grounding end 23b of the radiation electrode 22, and a loading element connected to the feeding end 23a of the radiation electrode 22. 24a. The base 21 used for the chip antenna has a substantially rectangular parallelepiped shape, and its cross-sectional shape is a U-shape, a B-shape, an L-shape, a trapezoidal shape, or a longitudinal cross-sectional shape is a U-shape. A rectangular shape with a letter shape or a curved shape may be used. The antenna device 2B according to the second embodiment of the present invention has a similar configuration in that a loading element is inserted between the feeding end and the feeding electrode in the surface mount antenna described in Japanese Patent Laid-Open No. 2003-179426. However, the difference is that the loading element 24b is inserted between the grounding end 23b of the radiation electrode 22 and the grounding electrode 25b, and the loading element 24a is inserted between the feeding end 23a of the radiation electrode 22 and the feeding electrode 25a. Since no electrode other than the soldering electrode is disposed on the bottom surface 21a of the base body 21 and the antenna device 2B composed of a chip antenna is mounted on the area 1a on the circuit board 1 where no ground conductor exists, There is little capacitive coupling with the ground conductor, and an almost uniform radiation electric field pattern is exhibited in any direction, resulting in good omnidirectionality. The radiation electrode 22 is a radiation electrode formed in a loop shape, and the radiation electrode 22 is bent in a U-shape or U-shape at a position that is line-symmetric with respect to the symmetry axis m of the radiation electrode 22. The part which makes is provided. The radiation electrode 22 has a grounding end 23b connected to the grounding electrode 25b via the loading element 24b at one end and a feeding end 23a connected to the feeding electrode 25a of the transmission / reception circuit via the loading element 24a at the other end. . The conductor pattern length portion of the bent shape provided on the loop-shaped radiation electrode 22 generates an inductance necessary for resonating in the GSM band, and the conductor pattern of the portion of the radiation electrode 22 forming the bent shape. Capacitance is generated in the opposite length portion. Therefore, the chip antenna which is the antenna device 2B according to the present invention has the equivalent circuit shown in FIG.

In addition, in the second embodiment of the present invention, the inductances L ₁ , L ₂ , and L ₃ correspond to the conductor patterns 221, 222, and 223 that constitute the bent portions of the radiation electrode 22, respectively. The capacitance C _i is formed between the opposing portions of the conductive pattern 221 and the conductive pattern 223 of the radiation electrode 22. Therefore, by changing the set length and shape of the conductor patterns 221, 222, 223 constituting the portion forming the bent shape of the radiation electrode 22 as appropriate _{L 1,} L 2, _{L 3} and _{C i,} the feeding end the input impedance Z _in viewing the radiation electrode from can be matched to 50 Omega. In this manner, the portion of the radiation electrode 22 that is bent is formed separately from the matching circuit by the loading element in which the input impedance matching is provided between one end of the radiation electrode and the ground electrode and between the other end of the radiation electrode and the feeding electrode. In addition to the inductances of the conductor patterns 221, 222, and 223, the capacitances are adjusted by adjusting the lengths of the conductor patterns 221 and 223 of the radiation electrode 22 and the distance between the opposing length portions of the conductor patterns 221 and 223. Is an important feature of the present invention.

  4 and 5 show examples of conductor pattern shapes printed on the base of an antenna device 2B constituted by a two-port chip antenna according to the second embodiment of the present invention. 4 and 5 are possible because of the arrangement space on the circuit board. However, in order to achieve a good antenna performance in a wide band, the straight line portion of the radiation electrode loop portion farthest from the end face of the ground conductor It is preferable that the conductor pattern 224 and the conductor pattern 221 of the radiation electrode 22 closest to the loading element be as far as possible because the degree of capacitive coupling between the electrode portions is reduced. 3 and FIG. 4, in FIG. 3, the conductor pattern 224 (not shown) of the linear portion of the loop portion of the radiation electrode 22 is different from the upper surface on which the linear portion 221 of the conductor pattern of the radiation electrode 22 is printed. Shows that it is printed on the invisible side. Further, FIG. 4 shows that the conductor pattern 224 of the linear portion of the loop portion of the radiation electrode 22 is printed on the upper surface of the base 21. Therefore, compared to the distance between the conductor pattern 221 of the radiation electrode 22 and the conductor pattern 224 of the loop portion of the radiation electrode 22 in FIG. 3, the conductor pattern 221 of the radiation electrode 22 and the loop portion of the radiation electrode 22 in FIG. Since the distance between the conductor patterns 224 in the straight line portion is short, the capacitance is larger. That is, the capacitive coupling in FIG. 3 is less, and a wider band can be achieved. FIG. 5 shows the case where all of the conductor patterns 221, 222, and 223 in the bent shape of the radiation electrode 22 are on one side of the base 21 in the case of FIG. 3, and the degree of capacitive coupling is shown in FIG. A little bigger. However, in FIG. 5, although the height of the space required for the antenna device 2B is slightly increased, the projected area viewed from above can be reduced, and thus the circuit board can be reduced accordingly.

  6, 7 and 8 show examples of other substrate shapes in the second embodiment of the present invention. The cross-sectional shapes of the bases 21a to 21f are U-shaped, B-shaped, L-shaped, trapezoidal as shown in FIGS. 6 and 7, or the longitudinal cross-sectional shapes of the bases 21g to 21f are as shown in FIG. The shape may be a square shape, a square shape, an arc shape, or the like. In this way, by cutting away a portion of the substrate 21, the volume of the dielectric can be reduced and the dielectric constant can be lowered. As a result, the capacitance can be reduced and the bandwidth can be increased. Further, since a part of the substrate is scraped off, the weight can be reduced accordingly. As shown in FIG. 8, when using a base whose cross-sectional shape in the longitudinal direction is a U shape, a B shape, an arc shape, etc., a conductor pattern that is a straight portion of the loop portion of the radiation electrode farthest from the ground conductor side Since the 224 can be arranged so as to be further away from the ground conductor side, the capacitance can be further reduced and the bandwidth can be increased.

  FIG. 9 shows a 2-port antenna device 2C according to a third embodiment of the present invention. The same parts as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. This antenna is connected to the radiation electrode 22 disposed on the surface of the standing sub-board 31 placed on the area 1 a where the ground conductor of the circuit board 1 does not exist, and to the ground end 23 b of the radiation electrode 22. It has a loading element 24b and a loading element 24a connected to the feeding end 23a of the radiation electrode 22. No electrode other than the soldering electrode for fixing the radiation electrode 22 and the standing sub-board 31 is arranged on the standing sub-board 31, and the standing sub-board 31 is also on the circuit board 1. Since it is mounted in the region 1a where no grounding conductor exists, the capacitance coupling with the grounding conductor is reduced, so that a substantially uniform radiation electric field pattern is exhibited in any direction, and as a result, good omnidirectionality is obtained. It is done. The radiation electrode 22 disposed on the surface of the sub-board 31 may be provided on one side of the sub-board 31 provided upright, or may extend over both sides. Further, since the thickness of the sub-board is increased to become a rectangular parallelepiped, the third embodiment of the present invention is another aspect of the chip antenna which is the antenna device 2B described in the second embodiment of the present invention. . The radiation electrode 22 is a radiation electrode formed in a loop shape, and is formed in a bent shape of the U-shaped or U-shaped radiation electrode 22 in a line-symmetrical position with respect to the symmetry axis m of the shape of the radiation electrode 22. Provide a part. The radiation electrode 22 has a grounding end 23b connected to the grounding electrode 25b via the loading element 24b at one end and a feeding end 23a connected to the feeding electrode 25a of the transmission / reception circuit via the loading element 24a at the other end. . The conductor pattern portion of the bent portion provided on the loop-shaped radiation electrode 22 generates an inductance necessary for resonating in the GSM band, and the relative portion of the conductor pattern portion of the portion of the radiation electrode 22 that bends. Capacitance is generated in the part to do. In this way, the radiation electrode 22 is printed and formed on the surface of the standing sub-board 31 placed on the area 1a where the ground conductor does not exist on the circuit board 1, so that the radiation electrode can be used without using a base. Since the portion can be configured, a small and inexpensive portable communication terminal device can be provided. Therefore, the antenna device 2C according to the present invention has the equivalent circuit shown in FIG.

In this embodiment, as in the first embodiment, the inductances L ₁ , L ₂ , and L ₃ correspond to the conductor patterns 221, 222, and 223 that form the bent portions of the radiation electrode 22, respectively, and the capacitance C _i is formed between opposite portions of the conductive pattern 221 and conductive pattern 223 of the radiation electrode 22. Therefore, by changing the set length and shape of the conductor patterns 221, 222, 223 constituting the portion forming the bent shape of the radiation electrode 22 as appropriate _{L 1,} L 2, _{L 3} and C _i, the feeding end the input impedance Z _in viewing the radiation electrode from can be matched to 50 [Omega. In this manner, the portion of the radiation electrode 22 that is bent is formed separately from the matching circuit by the loading element in which the input impedance matching is provided between one end of the radiation electrode and the ground electrode and between the other end of the radiation electrode and the feeding electrode. In addition to the inductance of the conductor patterns 221, 222, and 223 to be adjusted, the length of the conductor pattern 221 and the conductor pattern 223 of the radiation electrode 22 and the distance between the opposing length portions of the conductor pattern 221 and the conductor pattern 223 are adjusted. The ability to manipulate the capacitance is an important feature of the present invention that has high gain and omnidirectionality over a wide band.

  FIG. 10 shows a 2-port antenna device 2D according to a fourth embodiment of the present invention. The same parts as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted. This antenna has a radiation electrode 22 printed on the surface of a planar sub-board 41 placed on the circuit board 1 with a certain space in parallel to the circuit board 1 in a region 1 a where the ground conductor is not present on the circuit board 1. And a loading element 24b connected to the ground end 23b of the radiation electrode 22 and a loading element 24a connected to the power feed end 23a of the radiation electrode 22. The sub-board 41 is not printed with any electrode other than the radiation electrode 22 and the soldering electrode for fixing the sub-board, and the sub-board 41 is placed on the area 1 a where the ground conductor does not exist on the circuit board 1. Therefore, by reducing the capacitive coupling with the ground conductor, a substantially uniform radiation electric field pattern is exhibited in any direction, and as a result, good omnidirectionality can be obtained. The radiation electrode 22 printed on the surface of the sub-board 41 may be on one side of the sub-board 41 or on both sides. The radiation electrode 22 is an electrode formed in a loop shape, and is a portion that forms a bent shape of the radiation electrode 22 that is U-shaped or U-shaped at a line-symmetrical position with respect to the symmetry axis m of the shape of the radiation electrode 22. Is provided. The radiation electrode 22 has a grounding end 23b connected to the grounding electrode 25b via the loading element 24b at one end and a feeding end 23a connected to the feeding electrode 25a of the transmission / reception circuit via the loading element 24a at the other end. . The portion of the conductor pattern length of the bent portion provided on the radiation electrode 22 formed in a loop shape generates the inductance necessary for resonating in the GSM band, and the portion of the radiation electrode 22 having the bent shape Capacitance is generated in the opposite portion of the conductor pattern portion. Thus, by forming the radiation electrode 22 on the surface of the planar sub-board 41 placed in the area 1a where the ground conductor does not exist on the circuit board 1 in parallel with the circuit board 1, the conductor pattern is formed. Since the antenna circuit portion can be configured without using an antenna chip as a printed substrate, a small and thin portable communication terminal device can be provided. Therefore, the antenna device 2D according to the present invention has the equivalent circuit shown in FIG.

In this embodiment, as in the first embodiment, the inductances L ₁ , L ₂ , and L ₃ correspond to the conductor patterns 221, 222, and 223 that constitute the bent portions of the radiation electrode 22, respectively, and the capacitance C _i is formed between the length portion against the conductor patterns 221 and the conductor patterns 223 of the radiation electrode 22. Accordingly, by changing the lengths and shapes of the conductor patterns 221, 222, and 223 that constitute the bent portion of the radiation electrode 22 and changing L ₁ , L ₂ , L _3, and C _i , the feeding point the input impedance Z _in viewing the radiation electrode from can be matched to 50 [Omega. In this manner, the portion of the radiation electrode 22 that is bent is formed separately from the matching circuit by the loading element in which the input impedance matching is provided between one end of the radiation electrode and the ground electrode and between the other end of the radiation electrode and the feeding electrode. In addition to the inductance of the conductor patterns 221, 222, and 223 to be adjusted, the length of the conductor pattern 221 and the conductor pattern 223 of the radiation electrode 22 and the distance between the opposing length portions of the conductor pattern 221 and the conductor pattern 223 are adjusted. The ability to manipulate the capacitance is an important feature of the present invention that has high gain and omnidirectionality over a wide band.

  Next, the function and effect of the antenna device that is the two-port system of this embodiment will be described. The present inventor conducted antenna characteristic tests on Example 1 shown in FIG. 1 and Example 2 shown in FIG. 3 in order to verify the operational effects of the antenna device described above. In order to facilitate impedance matching, in the first and second embodiments, impedance matching portions by loading elements are provided between the ground end and the ground electrode and between the power supply end and the power supply electrode, respectively. The substrate 21 of Example 2 was formed of a ceramic dielectric having a relative dielectric constant εr of 8. In Example 2, the substrate dimensions were 30 mm long × 3 mm wide × 2 mm thick. In general, it has been confirmed that the planar antenna of the first embodiment has better omnidirectionality than the chip antenna of the second embodiment. Better than 2 is obtained. Therefore, the measurement propagation frequency band is the bandwidth BW (MHz) and the average gain (dBi) at VSWR2 in the GSM band and the DCS / PCS band for the first embodiment, and the GSM band and the DCS / PCS for the second embodiment. As the band and the UMTS band, the bandwidth BW (MHz), average gain (dBi), and directivity in VSWR 2 were measured. The reason why the VSWR is measured at 2 is that the practicality can be sufficiently secured if the VSWR is 3 or less in the band as the performance of the mobile communication terminal device.

  FIG. 11 shows a GSM band, a DCS / PCS band, and a UMTS band of an antenna device 2A that is a two-port system in which a radiation electrode is formed in a conductor pattern on a circuit board of the present invention, and loading elements are connected to both ends of the radiation electrode. It is a figure which shows the measurement result of VSWR in. The VSWR is measured by connecting the power supply terminal provided at one end of the antenna mounting board and the input terminal of the network analyzer via a coaxial cable (characteristic impedance 50 Ω), and the antenna terminal viewed from the network analyzer side at the power supply terminal. The VSWR was calculated based on this value by measuring the scattering parameter. In the data shown in FIG. 11, a value of VSWR of 3 or less is obtained in the target GSM band, DCS / PCS band, and UMTS band, and the power transmitted to the antenna is less reflected and efficiently transmitted to the antenna. It can be seen that sufficient characteristics are obtained for practical communication of the device.

FIG. 12 is a diagram showing a gain measurement result in the GSM band of the antenna device 2B configured by the 2-port chip antenna according to the present invention. When measuring the gain, a signal generator was connected to the power supply terminal of the antenna under test (transmission side) in an anechoic chamber, and the power radiated from the antenna was received by a reference antenna for reception. If the received power coming from the antenna under test is P _a and the received power measured by the transmission reference antenna having a known gain G _r is Pr, the gain G _a of the antenna under test is G _a = G _r × P _a / _Pr . For directivity, the antenna element under test is mounted on a turntable, and the gain measurement is performed while rotating the antenna under test, so that the X axis, Y axis, and Z axis can be adjusted as shown in FIGS. The gain with respect to the rotation angle when rotated as the center was measured for each of the GSM band, DCS band, and UMTS band. The X axis is the horizontal direction with the operation surface of the mobile communication terminal device as the front, the Y axis is the vertical direction with the operation surface of the mobile communication terminal device as the front, and the Z axis is vertical with the operation surface of the mobile communication terminal device as the front. Align with the direction. In particular, there are many cases where the operation of mobile communication terminal equipment is used with the Y-axis generally pointing to the ground because of its operation form, and since the base station uses vertical polarization, the omnidirectionality of vertical polarization in the XZ plane is important. The gain in that case may be -6 dBi or more over the entire circumference of the Y axis. The gain measurement result in the GSM band of FIG. 12 shows that the average gain of the vertical polarization in the XZ plane is -0.18 dBi and the maximum gain is 0.71 dBi, and sufficient vertical polarization gain and omnidirectionality can be obtained. You can see that Similarly, the gain measurement result in the DCS band in FIG. 13 shows that the average gain of the vertical polarization in the XZ plane is −5.38 dBi and the maximum gain is −3.22 dBi, and the sufficient vertical polarization gain and omnidirectionality are obtained. It can be seen that is obtained. Similarly, in the gain measurement result in the UMTS band of FIG. 14, the average gain of the vertical polarization in the XZ plane is −5.55 dBi and the maximum gain is −3.67 dBi, and the sufficient vertical polarization gain and omnidirectionality are obtained. It can be seen that is obtained. Here, there is no measurement data in the PCS band close to the DCS band, but there is sufficient vertical polarization gain and omnidirectionality even in the DCS band close to the PCS band and the UMTS band, which is a higher frequency band than the PCS band. Thus, it can be said that sufficient vertical polarization gain and omnidirectionality are obtained even in the PCS band between the DCS band and the UMTS band.

  FIG. 15 shows the result of measuring the average gain of vertical polarization in the XZ plane in the GSM band of the antenna device 2A constituted by the two-port conductor pattern according to the present invention, and FIG. 16 is constituted by the conductor pattern according to the present invention. 3 is a result of measuring the average gain of vertically polarized waves in the XZ plane in the DCS / PCS band of the antenna apparatus 2A. In the gain measurement result in the GSM band of FIG. 15, the lower limit of the average gain of the vertical polarization in the XZ plane is about −3 dBi, and in the gain measurement result in the DCS / PCS band and the UMTS band of FIG. The lower limit of the average gain of the vertical polarization at −4 dBi. Since the conductor pattern antenna generally has better directivity characteristics than the chip antenna, the average gain of the conductor pattern antenna is not less than -6 dBi, so that sufficient omnidirectionality of the vertical polarization in the XZ plane is obtained. It can be said that

  From the above results, the antenna device 2A configured with the 2-port conductor pattern of Example 1 has a VSWR of 3 or less in any of the GSM band, the DCS / PCS band, and the UMTS band, which is sufficient for practical communication. In the case of the GSM band, the antenna gain was -3 db or more in the ZX plane and -4 db or more in the DCS / PCS band, and it was found that sufficient omnidirectionality for practical communication was obtained. Further, although the antenna of Example 2 had a slightly lower radiation gain than that of Example 1, the gain was almost close to a circle in the ZX plane, and practical omnidirectionality was obtained. As described above, the antennas of Example 1 and Example 2 were able to obtain good antenna performance balanced in all of the bandwidth, radiation gain, and directivity.

It is a top view of antenna device 2A which shows the 1st example of the present invention. It is an equivalent circuit diagram of the antenna device of the present invention. It is a top view of the antenna apparatus 2B which shows the 2nd Example of this invention. It is a perspective view which shows the example of another conductor pattern shape printed on the base | substrate of the antenna apparatus 2B by 2nd Example of this invention. It is a perspective view which shows another example of conductor pattern shape printed on the base | substrate of the antenna apparatus 2B by the 2nd Example of this invention. It is a figure which shows the example of the other base | substrate shape in the 2nd Example of this invention. It is a figure which shows the example of the other base | substrate shape in the 2nd Example of this invention. It is a figure which shows the example of the other base | substrate shape in the 2nd Example of this invention. FIG. 10 is a perspective view of an antenna device 2C according to a third embodiment of the present invention. It is a perspective view of antenna device 2D by the 4th example of the present invention. It is a figure which shows the measurement result of VSWR in GSM band, DCS / PCS band, and UMTS band of 2 A of antenna apparatuses by this invention. It is a gain measurement result in the GSM band of the antenna device 2B according to the present invention. It is a gain measurement result in the DCS band of the antenna device 2B according to the present invention. It is a gain measurement result in the UMTS band of the antenna device 2B according to the present invention. It is a gain measurement result in the GSM band of 2 A of antenna apparatuses by this invention. It is a gain measurement result in the DCS / PCS band of the antenna device 2A according to the present invention. It is a figure which shows an example of the loading element 24 used for the antenna apparatus of this invention.

Explanation of symbols

1: Circuit board 1a: Region 1b where no ground conductor exists 1b: Region 2A, 2B, 2C, 2D where ground conductor exists: Antenna devices 21, 21a to 21k: Base 22: Radiation electrode 23a: Feed end 23b: Ground end 24 24a, 24b: Loading element 25a: Feed electrode 25b: Ground electrodes 221, 222, 223, 224: Conductor pattern 31: Standing sub-board 41: Sub-board m: Symmetry axes L, L _i , L ₀ , L ₁ , L ₂ , L ₃ : Inductance C, C _i : Capacitance

Claims (8)

A radiation electrode provided on at least the upper surface of the circuit board, a ground electrode provided on the circuit board so as to face one end of the radiation electrode, and provided on the circuit board so as to face the other end of the radiation electrode The radiation electrode is line symmetric with respect to the axis of symmetry of the shape, one end of the radiation electrode is a ground end, and the other end is a feed end, An antenna having an impedance matching portion based on capacitance and inductance between the ground end and the ground electrode, and an impedance matching portion based on capacitance and inductance between the feeding end and the feeding electrode. apparatus. 2. The surface-mounted antenna according to claim 1, wherein the radiation electrode is a conductor pattern provided on a surface of a plate-like or substantially rectangular parallelepiped base mounted on the circuit board. 2. The surface-mount antenna according to claim 1, wherein the radiation electrode is a conductor pattern provided on a sub-board placed on the circuit board. 4. The antenna device according to claim 1, wherein impedance matching can be performed by adjusting capacitance and inductance by changing a shape and a position of the radiation electrode. The antenna device according to any one of claims 1 to 3, wherein the radiation electrode has a loop shape, and a part of the loop radiation electrode has a U shape, a U shape, or a crankshaft shape. An antenna device having any shape. 6. The antenna device according to claim 1, wherein the length of the radiation electrode is 1/2 wavelength or 1/4 wavelength of a radio wave used for transmission / reception. 7. The antenna device according to claim 1, wherein one end of the radiation electrode is a ground end, the other end is a feeding end, and an impedance due to a capacitance and an inductance between the ground end and the ground electrode. The antenna device, wherein the matching portion and the impedance matching portion due to capacitance and inductance between the feeding end and the feeding electrode are formed in a conductor pattern on the surface of the circuit board. A portable communication device comprising the antenna device according to claim 1.

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