JP6218069B2 - antenna - Google Patents

Description

  The present invention relates to an antenna, and can be suitably used for, for example, an antenna that can handle a plurality of frequency bands.

  In recent years, the importance of wireless communication taking advantage of features that do not require wiring has increased. Many communication systems are provided for wireless communication. In order to provide services that realize these good points, a multi-communication system equipped with a plurality of communication systems has been developed. For this reason, development of a radio circuit that can be used in a multi-frequency band has been energetically promoted so that communication devices can be miniaturized by sharing the radio circuit among a plurality of systems.

  In particular, since the antenna has a large size among wireless circuits, a small multi-frequency antenna is being developed as a key device for miniaturization. As for a multi-frequency antenna, as shown in cited document 1 (Japanese Patent Laid-Open No. 2011-55306), a single small antenna is resonated in the lowest-order mode and higher-order mode by a built-in lumped element. A technique capable of operating at multiple frequencies by controlling the frequency is known. Still, it is extremely difficult to cope with the bandwidth in each of a large number of communication systems. In particular, regarding the adjacent bands, it is necessary to make the value of the lumped constant element extremely large in order to bring the resonance frequency of the high-order mode far away from the resonance frequency of the lowest-order mode close to the lowest frequency, which is particularly difficult.

JP 2011-55306 A

  Provided is an antenna having multi-frequency characteristics and variable in each band, that is, a multi-frequency reconfigurable antenna. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  The means for solving the problem will be described below using the numbers used in the (DETAILED DESCRIPTION). These numbers are added to clarify the correspondence between the description of (Claims) and (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  According to one embodiment, a plurality of antenna conductors (21 to 23, etc.) constituting an antenna are connected in series via a plurality of impedance circuit portions (31 to 37). Variable impedance elements (C31, C33, C34, etc.) such as varactors are provided in the plurality of impedance circuit portions (31-34, etc.).

  According to the embodiment, the antenna characteristics can be adjusted for each of a plurality of usable frequency bands by appropriately changing the capacitance values of the plurality of variable capacitance elements.

FIG. 1A is a cross-sectional view taken along a cross-sectional line AA, showing the configuration of the antenna according to the first embodiment. FIG. 1B is a top view showing the configuration of the antenna according to the first embodiment. FIG. 1C is a bottom view showing the configuration of the antenna according to the first embodiment. FIG. 1D is a circuit diagram showing an equivalent circuit of the antenna according to the first embodiment. FIG. 1E is a circuit diagram showing an equivalent circuit of another antenna according to the first embodiment. FIG. 2A is a top view showing an example of dimensions of the antenna according to the first embodiment. FIG. 2B is a bottom view showing a dimension example of the antenna according to the first embodiment. FIG. 3A is a graph illustrating a first characteristic example of the antenna according to the first embodiment. FIG. 3B is a graph illustrating a second characteristic example of the antenna according to the first embodiment. FIG. 3C is a graph illustrating a third characteristic example of the antenna according to the first embodiment. FIG. 3D is a graph illustrating a fourth characteristic example of the antenna according to the first embodiment. FIG. 4A is a circuit diagram showing an equivalent circuit of the antenna according to the second embodiment. FIG. 4B is a circuit diagram showing an equivalent circuit of another antenna according to the second embodiment. FIG. 5A is a graph comparing characteristic examples of antennas according to the first and second embodiments. FIG. 5B is a graph comparing characteristic examples of the antennas according to the first and second embodiments. FIG. 6A is a top view showing the configuration of the antenna according to the third embodiment. FIG. 6B is a circuit diagram showing an equivalent circuit of the antenna according to the third embodiment. FIG. 6C is a circuit diagram showing an equivalent circuit of another antenna according to the third embodiment. FIG. 7 is a graph illustrating an example of characteristics of the antenna according to the third embodiment. FIG. 8A is a top view showing the configuration of the antenna according to the fourth embodiment. FIG. 8B is a bottom view showing the configuration of the antenna according to the fourth embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments for implementing an antenna according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1A is a cross-sectional view taken along a cross-sectional line AA showing the configuration of the antenna according to the first embodiment. FIG. 1B is a top view showing the configuration of the antenna according to the first embodiment. FIG. 1C is a bottom view showing the configuration of the antenna according to the first embodiment. The components of the antenna according to the first embodiment shown in FIGS. 1A to 1C will be described.

  The antenna according to the first embodiment includes a power feeding unit 11, a dielectric substrate 12, a first ground conductor 17, a first via group 41, a second ground conductor 18, and a first antenna conductor 21. The first impedance circuit section 31, the second antenna conductor 22, the second impedance circuit section 32, the third antenna conductor 23, the second via group 42, the connection conductor 15, 3 impedance circuit portion 33 and line conductor 13.

  The first ground conductor 17, the second ground conductor 18, the first antenna conductor 21, the second antenna conductor 22, the third antenna conductor 23, the connection conductor 15, and the line conductor 13 are It is comprised with conductors, such as copper (Cu).

  The connection relationship of the components of the antenna according to the first embodiment will be described. A first ground conductor 17 and first to third antenna conductors 21 to 23 are provided on the surface of the dielectric substrate 12. A second ground conductor 18, a line conductor 13, and a connection conductor 15 are provided on the back surface of the dielectric substrate 12. The first and second via groups 41 and 42 are provided through the dielectric substrate 12.

  The power feeding unit 11 and the first and second impedance circuit units 31 and 32 are preferably provided on the surface of the dielectric substrate 12, but may be provided at other locations. The third impedance circuit unit 33 is preferably provided on the back surface of the dielectric substrate 12, but may be provided at other locations.

  One feeding point of the feeding unit 11 is connected to one end of the first antenna conductor 21. The other end portion of the first antenna conductor 21 is connected to one end portion of the first impedance circuit portion 31. The other end of the first impedance circuit unit 31 is connected to one end of the second antenna conductor 22. The other end portion of the second antenna conductor 22 is connected to one end portion of the second impedance circuit portion 32. The other end of the second impedance circuit unit 32 is connected to one end of the third antenna conductor 23. One end of each of the second via groups 42 is connected to a predetermined position of the third antenna conductor 23. The other end of each of the second via groups 42 is connected to a predetermined position of the connection conductor 15. One end of the third impedance circuit unit 33 is connected to one end of the connection conductor 15. One end portion of the line conductor 13 is connected to the other end portion of the third impedance circuit portion 33. The other end of the line conductor 13 is connected to one end of the second ground conductor 18. One end of each of the first via groups 41 is connected to a predetermined position of the second ground conductor 18. The other end of each of the first via groups 41 is connected to a predetermined position of the first ground conductor 17. One end of the first ground conductor 17 is connected to the other feeding point of the feeding unit 11.

  FIG. 1D is a circuit diagram showing an equivalent circuit of the antenna according to the first embodiment. Components of the circuit diagram shown in FIG. 1D will be described. The circuit diagram shown in FIG. 1D shows the first feeding point 11A, the second feeding point 11B, the first impedance circuit unit 31, the second impedance circuit unit 32, and the third antenna conductor 23. An equivalent circuit, a third impedance circuit unit 33, and a coupling circuit 20 are included. The coupling circuit 20 is an equivalent circuit showing coupling between an antenna and space.

  The first impedance circuit unit 31 includes a varactor C31 and an inductor L31. The second impedance circuit unit 32 includes a capacitor C32. The equalization circuit for the third antenna conductor 23 includes a capacitor C23, a first inductor L23A, and a second inductor L23B. The third impedance circuit unit 33 includes a varactor C33 and an inductor L33. The coupling circuit 20 includes a capacitor C20, an inductor L20, and a resistor R20.

  Here, the varactor is an element whose capacitance value changes according to an applied DC voltage or the like, and hereinafter, the variable capacitance element is generically referred to as a varactor. Although described later in detail, such a varactor can also be realized by using a diode and a capacitor connected in series.

A connection relation of components in the circuit diagram illustrated in FIG. 1D will be described.
The first feeding point 11 </ b> A is connected to one end of the first impedance circuit unit 31.
One end of the first impedance circuit unit 31 is commonly connected to one end of the varactor C31 and one end of the inductor L31.
The other end of the varactor C31 and the other end of the inductor L31 are commonly connected to the other end of the first impedance circuit section 31.
The other end of the first impedance circuit unit 31 is connected to one end of the second impedance circuit unit 32.
One end of the second impedance circuit unit 32 is connected to one end of the capacitor C32.
The other end of the capacitor C32 is connected to the other end of the second impedance circuit unit 32.
The other end of the second impedance circuit unit 32 is connected to the first end of the third antenna conductor 23.
The first end of the third antenna conductor 23 is connected to one end of the first inductor L23A.
The other end of the first inductor L23A is commonly connected to one end of the second inductor L23B and one end of the capacitor C23.
The other end of the second inductor L23B is connected to the second end of the third antenna conductor 23. The other end of the capacitor C23 is connected to the third end of the third antenna conductor 23. The second end portion of the third antenna conductor 23 is commonly connected to one end portion of the third impedance circuit portion 33 and one end portion of the coupling circuit 20. One end of the third impedance circuit unit 33 is commonly connected to one end of the varactor C33 and one end of the inductor L33. The other end of the varactor C33 and the other end of the inductor L33 are commonly connected to the other end of the third impedance circuit section 33. One end of the coupling circuit 20 is connected to one end of the capacitor C20. The other end of the capacitor C20 is commonly connected to one end of the inductor L20 and one end of the resistor R20. The other end of the inductor L20 and the other end of the resistor R20 are commonly connected to the other end of the coupling circuit 20. The third end portion of the third antenna conductor 23, the other end portion of the third impedance circuit portion 33, and the other end portion of the coupling circuit 20 are commonly connected to the second feeding point 11B. Yes.

  The operation of the antenna according to the first embodiment will be described using the equivalent circuit shown in FIG. 1D. The coupling circuit 20 represents the radiation phenomenon at the operating antenna, ie the coupling of the antenna and space. In the coupling circuit 20, the resistor R20 represents that power supplied from the feeding points 11A and 11B to the antenna is consumed. This consumed power represents the power lost from the antenna that spreads to infinity due to radiation from the antenna to space.

  The largest third antenna conductor 23 among the first to third antenna conductors 21 to 23 can be interpreted as a distributed constant line. In the equivalent circuit shown in FIG. 1D, two inductors L23A and L23B are used. In addition, it is expressed as an aggregate of one shunt capacitor C23. The first and second antenna conductors 21 and 22 have a sufficiently small area as compared with the third antenna conductor 23, and therefore can be interpreted as being connected to a lumped constant element. It is omitted in the equivalent circuit shown.

  In order for the antenna to operate effectively, impedance matching at the feed points 11A and 11B is necessary so that all of the power supplied to the feed points 11A and 11B can enter the antenna. This impedance matching is realized when the impedance at the feeding points 11A and 11B and the impedance when the antenna is viewed from the feeding points 11A and 11B are in a complex conjugate relationship. However, the impedance at the feeding points 11A and 11B is usually a real number. Therefore, it is necessary to adjust the impedance of the antenna side viewed from the feeding points 11A and 11B to the same real number as the impedance at the feeding points 11A and 11B.

  In order to realize this adjustment at a desired frequency at which the antenna operates, the first to third impedance circuit units 31 to 33 are provided in the antenna of this embodiment. However, the impedances of the inductors L31 and L33 and the capacitors or varactors C31 to C33, which are lumped elements, vary according to the frequency. Therefore, impedance matching can be obtained only at a specific frequency. This particular frequency that is impedance matched is called the operating frequency in the sense of the frequency at which the antenna operates effectively.

  Actually, since the frequency that can be used for communication is determined by laws and regulations, it is necessary to adjust the impedance value of each lumped constant element in accordance with the determined frequency. In other words, the operating frequency can be made variable by making the impedance value of the lumped constant element variable. In the antenna according to the first embodiment, the varactor C31 provided in the first impedance circuit unit 31 and the varactor C33 provided in the third impedance circuit unit 33 have a capacitance that changes according to the applied DC voltage. Have.

  The varactors C31 and C33 shown in FIG. 1D can adjust the capacitance value by appropriately applying a DC voltage, but the diode also has a capacitance that changes according to the applied DC voltage. When diodes are used as the varactors C31 and C33, it is desirable to provide a capacitor connected in series with the diodes. This is because the inductors L31 and L33 are connected in parallel to the varactors C31 and C33, respectively, and if there is no capacitor connected in series with the diode, the DC voltage is applied to the diode via the inductors L31 and L33. This is because they are short-circuited. In other words, in the varactors C31 and C33, when a diode and a capacitor are connected in series and a DC voltage is applied to both ends thereof, the capacitor is opened and a bias voltage can be applied to the diode. At this time, the capacitance values of the varactors C31 and C33 are the total amount of the capacitance of the capacitor and the capacitance of the diode, and the value can be appropriately controlled by appropriately selecting the capacitance of the capacitors arranged in series. Is clear.

  The antenna according to the present invention provides an antenna structure in which the operating frequency can be varied without largely deviating from impedance matching by appropriately adjusting the DC voltage applied to each varactor.

  The antenna according to the first embodiment is configured so that matching can be achieved at two frequencies by arranging lumped constant elements, that is, first to third impedance circuit units 31 to 33 as in the equivalent circuit shown in FIG. 1D. It has become. Hereinafter, the effectiveness of changing the frequency of use of the antenna using this configuration will be described. Here, an example in the case of using 2.5 GHz (gigahertz) and 5 GHz as specific operating frequencies will be described.

  FIG. 2A is a top view showing an example of dimensions of the antenna according to the first embodiment. 2A shows the length and width of the first to third antenna conductors 21 to 23 shown in FIG. 1B. That is, in the first antenna conductor 21, the length is set to X1, and the width is set to Y1. In the second antenna conductor 22, the length is set as X2, and the width is set as Y2. In the third antenna conductor 23, its length is set as X3, and its width is set as Y3.

  FIG. 2B is a bottom view showing a dimension example of the antenna according to the first embodiment. 2B shows the length and width of the line conductor 13 and the connection conductor 15 shown in FIG. 1C. That is, in the line conductor 13, the length is set as X4 and the width is set as Y4. In the connection conductor 15, the length is set to X5, and the width is set to Y5.

The numerical values of the dimensions X1 to X5 and Y1 to Y5 shown in FIGS. 2A and 2B are as follows.
X1 = 1.3mm (millimeter)
Y1 = 1.0mm
X2 = 0.9mm
Y2 = 0.6mm
X3 = 7.9mm
Y3 = 3.3mm
X4 = 2.8mm
Y4 = 0.2mm
X5 = 0.9mm
Y5 = 0.9mm

  The dielectric substrate 12 has a relative dielectric constant of 4.6, a dielectric loss tangent of 0.01, and a thickness of 1 mm.

  FIG. 3A is a graph illustrating a first characteristic example of the antenna according to the first embodiment. FIG. 3A includes first to fifth graphs (a) to (e). In common to these first to fifth graphs (a) to (e), the horizontal axis indicates the frequency of the power supplied to the antenna, and the vertical axis indicates the S11 parameter of the antenna, that is, the reflection loss. .

  The conditions of the example shown in FIG. 3A are as follows. The impedance at the feeding points 11A and 11B is 25Ω (ohms). In the first impedance circuit unit 31, the capacitance value of the varactor C31 is fixed to zero, and the inductance value of the inductor L31 is 1.4 nH (nanohenry). In the second impedance circuit section 32, the capacitance value of the capacitor C32 is 0.15 pF (picofarad). In the third impedance circuit unit 33, the inductance value of the inductor L33 is 3.4 nH.

  In addition to these conditions, the first to fifth graphs (a) to (e) shown in FIG. 3A indicate the capacitance value of the varactor C33 provided in the third impedance circuit unit 33 as 0 to 0.4 pF. The characteristic of the antenna when it changes in the range is shown. The first graph (a) shows the antenna characteristics when the capacitance value of the varactor C33 is 0 pF. The second graph (b) shows the antenna characteristics when the capacitance value of the varactor C33 is 0.1 pF. The third graph (c) shows the antenna characteristics when the capacitance value of the varactor C33 is 0.2 pF. The fourth graph (d) shows the antenna characteristics when the capacitance value of the varactor C33 is 0.3 pF. The fifth graph (e) shows the antenna characteristics when the capacitance value of the varactor C33 is 0.4 pF.

  As can be seen from FIG. 3A, in the 2.5 GHz band, as the capacity of the varactor C33 increases, the amount of change in reflection loss decreases, and the usable band moves in a lower direction. From the viewpoint of the antenna reflection loss, the S11 parameter can be sufficiently used if it is −10 dB or less, and therefore a slight change in the reflection loss shown in FIG. 3A is not a big problem.

  FIG. 3B is a graph illustrating a second characteristic example of the antenna according to the first embodiment. 3B also includes the first to fifth graphs (a) to (e) as in FIG. 3A, the horizontal axis indicates the frequency of the power supplied to the antenna, and the vertical axis indicates the S11 parameter of the antenna. That is, the reflection loss is shown.

  The conditions of the example shown in FIG. 3B are the same as in the case of FIG. 3A, but a band of 5 GHz is used as a use frequency. As can be read from the graph group shown in FIG. 3B, the antenna according to the first embodiment can also be used in the 5 GHz band. However, the frequency that can be used in the 5 GHz band is substantially constant. Since the reflection loss in the 5 GHz band becomes worse as the capacity value of the varactor C33 increases, the capacity value of the varactor C33 may be fixed to 0 pF when this antenna is used in the 5 GHz band. desirable.

  In the example shown in FIGS. 3A and 3B, the impedance of the feeding points 11A and 11B is set to 25Ω, but this impedance value is merely an example. By appropriately changing the impedance value of each lumped element, the impedance of the feeding points 11A and 11B can be set to a desired value, and the resonance frequency of the antenna can be made variable.

  Next, by partially changing the conditions used in FIGS. 3A and 3B, the capacitance value of the varactor C33 is fixed to 0, and the capacitance value of the varactor C31 is changed in the range of 0 to 0.4 pF. A third characteristic example in the 2.5 GHz band and a fourth characteristic example in the 5 GHz band will be described.

  FIG. 3C is a graph illustrating a third characteristic example of the antenna according to the first embodiment. FIG. 3D is a graph illustrating a fourth characteristic example of the antenna according to the first embodiment. 3C and 3D both include the first to fifth graphs (a) to (e) as in FIG. 3A, and the horizontal axis indicates the frequency of the power supplied to the antenna, and the vertical axis The axis indicates the S11 parameter of the antenna, that is, the reflection loss. Similarly to the case of FIG. 3A, in the first to fifth graphs (a) to (e) in FIGS. 3C and 3D, the capacitance values of the varactor C31 are 0 pF, 0.1 pF, 0. This corresponds to the case of 2 pF, 0.3 pF and 0.4 pF.

  FIG. 3C shows an example of antenna characteristics in the 2.5 GHz band. As can be seen from FIG. 3C, even if the capacitance value of the varactor C31 changes, the reflection loss of the antenna hardly changes.

  FIG. 3D shows an example of antenna characteristics in the 5 GHz band. As can be read from FIG. 3D, the frequency band in which the antenna can be used moves in the lower direction as the capacitance value of the varactor C31 increases.

  3C and 3D show that by controlling the capacitance value of the varactor C31, it is possible to adjust the operating frequency in the 5 GHz band while maintaining the characteristics in the 2.5 GHz band.

  In the example shown in FIGS. 3C and 3D, the impedance of the feeding points 11A and 11B is set to 25Ω, but this impedance value is merely an example. By appropriately changing the impedance value of each lumped element, the impedance of the feeding points 11A and 11B can be set to a desired value, and the resonance frequency of the antenna can be made variable.

  A modification of the antenna according to the present embodiment will be described. FIG. 1E is a circuit diagram showing an equivalent circuit of another antenna according to the first embodiment.

  A configuration of the antenna illustrated in FIG. 1E will be described. The antenna shown in FIG. 1E can be obtained by making the following changes to the antenna shown in FIG. 1D. That is, in each of the first impedance circuit unit 31 and the third impedance circuit unit 33, the varactor and the inductor connected in parallel in the configuration shown in FIG. 1D are connected in series in the configuration shown in FIG. 1E. Connecting.

  More specifically, first, in the first impedance circuit unit 31, the inductor L31 and the varactor C31 are connected in series between the first feeding point 11A and the capacitor C32.

  Next, in the third impedance circuit unit 33, the inductor L33 and the varactor C33 are connected in series between the connection point of the inductor L23B and the capacitor C20 and the second feeding point 11B.

  In the other antenna shown in FIG. 1E, one of the first impedance circuit unit 31 and the third impedance circuit unit 33 may have a serial connection configuration and the other may have a parallel connection configuration. Other configurations of the other antenna in the first embodiment shown in FIG. 1E are the same as those in the case of FIGS. 1A to 1D, and thus further detailed description is omitted.

  The operation of another antenna according to the first embodiment having the configuration shown in FIG. 1E will be described. In the antenna shown in FIG. 1E, as in the case of FIG. 1D, the impedance values of the first impedance circuit unit 31 and the third impedance circuit unit 33, particularly the reactance values of the respective inductors, can be adjusted appropriately. The resonance frequency can be set to a desired value.

(Second Embodiment)
In the first embodiment, as a result of increasing the capacitance value of the varactor C33 provided in the third impedance circuit unit 33 to 0.4 pF, the usable frequency at which the S11 parameter representing the reflection loss is −10 dB or less is The lowest. At this time, the S11 parameter gradually deteriorates compared to the case where the capacity value of the varactor C33 is smaller.

  Therefore, in the second embodiment, an antenna structure is provided in which the capacity value of the varactor C33 is further increased to extend the usable frequency to a lower range, and at the same time, the S11 parameter representing the reflection loss is maintained at a good value. .

  FIG. 4A is a circuit diagram showing an equivalent circuit of the antenna according to the second embodiment. The configuration of the antenna according to the second embodiment shown in FIG. 4A is obtained by replacing the capacitor C32 of the second impedance circuit unit 32 with the varactor C32 in the antenna according to the first embodiment shown in FIGS. 1A to 1D. Equal to the thing. The cross-sectional view, the top view, and the bottom view of the antenna according to the second embodiment are the same as those in the first embodiment shown in FIGS. 1A to 1C, and thus illustration and further detailed description thereof are omitted. .

  In the antenna according to the second embodiment, the capacity value of the varactor C33 provided in the third impedance circuit unit 33 is increased to 1 pF or 2 pF, so that the usable frequency band is in the vicinity of 1.6 GHz or 1.95 GHz. It is moved. Of these frequency bands, a characteristic example obtained in the former case is shown in FIG. 5A, and a characteristic example obtained in the latter case is shown in FIG. 5B.

  FIG. 5A and FIG. 5B are graphs comparing characteristic examples of antennas according to the first and second embodiments. Each of FIG. 5A and FIG. 5B includes first to third graphs (a) to (c). In common with the first to third graphs (a) to (c) shown in FIGS. 5A and 5B, the horizontal axis indicates the frequency, and the vertical axis indicates the S11 parameter indicating the reflection loss.

  5A and 5B, in the first graph (a), the capacitance value of the capacitor C32 provided in the second impedance circuit unit 32 of the antenna according to the first embodiment is set to 0.15 pF. The example of the characteristic obtained in the case is shown. Similarly, the second graph (b) shows a characteristic example obtained when the capacitance value of the varactor C32 provided in the second impedance circuit unit 32 of the antenna according to the first embodiment is set to 0.10 pF. Is shown. Similarly, the third graph (c) shows a characteristic example obtained when the capacitance value of the varactor C33 is further increased by 0.1 pF from the condition of the second graph (b).

  As can be seen from FIGS. 5A and 5B, in any case, in the antenna according to the first embodiment, the S11 parameter representing the reflection loss is in the vicinity of −10 dB. On the other hand, in the case of the second graph (b) of the second embodiment, although the band is slightly higher, the S11 parameter is significantly reduced. As can be read from the third graph (c) of the second embodiment, the increased bandwidth can be lowered by further increasing the capacitance value of the varactor C33. Even if the bandwidth is lowered to the same value as in the first embodiment, the S11 parameter can be significantly reduced.

  A modification of the antenna according to the present embodiment will be described. FIG. 4B is a circuit diagram showing an equivalent circuit of another antenna according to the second embodiment.

  The configuration of the antenna shown in FIG. 4B will be described. The antenna shown in FIG. 4B can be obtained by adding the same changes to the antenna shown in FIG. 4A as in the case of FIG. 1D to FIG. 1E in the first embodiment. That is, in each of the first impedance circuit unit 31 and the third impedance circuit unit 33, the varactor and the inductor connected in parallel in the configuration shown in FIG. 4A are connected in series in the configuration shown in FIG. 4B. Connecting.

  The other configurations of the other antennas in the second embodiment shown in FIG. 4B are the same as those in FIGS. 1A to 1C, FIG. 1E, and FIG.

  The operation of another antenna according to the second embodiment having the configuration shown in FIG. 4B is also the same as that in FIGS. 1A to 1C, 1E, and 4A, and thus further detailed description is omitted.

(Third embodiment)
The third embodiment provides an antenna structure that is effective in the vicinity of 2.5 GHz and in the vicinity of 5 GHz under the same conditions as in the first embodiment.

  FIG. 6A is a top view showing the configuration of the antenna according to the third embodiment. FIG. 6B is a circuit diagram showing an equivalent circuit of the antenna according to the third embodiment. The configuration of the antenna according to the third embodiment shown in FIGS. 6A and 6B is the same as that of the antenna according to the first embodiment shown in FIGS. 1A to 1D except that the capacitor C32 of the second impedance circuit unit 32 is replaced with the varactor C32. Further, it is equivalent to a configuration in which a fourth impedance circuit unit 34 connected in parallel to the power feeding unit 11 is added. The cross-sectional view and the bottom view of the antenna according to the third embodiment are the same as those of the first embodiment shown in FIGS. 1A and 1C, and thus illustration and further detailed description thereof are omitted.

  FIG. 7 is a graph illustrating an example of characteristics of the antenna according to the third embodiment. FIG. 7 includes first to third graphs (a) to (c). In common with the first to third graphs (a) to (c), the horizontal axis indicates the frequency, and the vertical axis indicates the S11 parameter indicating the reflection coefficient.

  In the first to third graphs (a) to (c) shown in FIG. 7, the capacitance value of the varactor C34 provided in the fourth impedance circuit unit 34 is set to 0 pF, 0.2 pF, and 0.4 pF. Each case is shown. Other conditions are the same as in the first embodiment. That is, the impedance of the feeding points 11A and 11B is 25Ω. In the third impedance circuit unit 33, the inductance of the inductor L33 is fixed to 3.4 nH, and the capacitance value of the varactor C33 is fixed to 0. The capacitance provided in the second impedance circuit section 32 or the capacitance value of the varactor C32 is fixed to 0.15 pF. In the first impedance circuit unit 31, the inductance value of the inductor L31 is fixed to 1.4 nH, and the capacitance value of the varactor C31 is fixed to 0 pF.

  In the antenna according to the third embodiment, as can be read from the graph shown in FIG. 7, the usable frequency band moves in the higher direction by increasing the capacitance value of the varactor C34.

  Since this moving direction is the opposite direction to that of the antenna according to the first embodiment shown in FIGS. 3A and 3D, it is possible to cancel the movement of the used frequency. Therefore, the characteristics of the antenna according to the present invention can be adjusted more freely by appropriately changing the capacitance values of the plurality of varactors C31, C33 and C34 provided in the antenna according to the third embodiment.

  A modification of the antenna according to the present embodiment will be described. FIG. 6C is a circuit diagram showing an equivalent circuit of another antenna according to the third embodiment.

  A configuration of the antenna illustrated in FIG. 6C will be described. The antenna shown in FIG. 6C is obtained by making the same change as the case of FIG. 1D from FIG. 1D to FIG. 1E in the antenna shown in FIG. 6B. That is, in each of the first impedance circuit unit 31 and the third impedance circuit unit 33, the varactor and the inductor connected in parallel in the configuration shown in FIG. 6B are connected in series in the configuration shown in FIG. 6C. Connecting.

  The other configurations of the other antennas in the second embodiment shown in FIG. 6C are the same as those in FIGS. 1A to 1C, FIG. 1E, and FIG. 6B, and thus further detailed description is omitted.

  The operation of another antenna according to the second embodiment having the configuration shown in FIG. 6C is also the same as that in FIGS. 1A to 1C, FIG. 1E, and FIG.

(Fourth embodiment)
In the first to third embodiments, a so-called monopole antenna structure is provided in which a conductor constituting the antenna is arranged on one side from the power feeding portion 11. In the fourth embodiment, a so-called dipole antenna structure is provided in which two sets of components of the antenna according to the first embodiment are arranged symmetrically with the feeding unit 11 in between.

  FIG. 8A is a top view showing the configuration of the antenna according to the fourth embodiment. FIG. 8B is a bottom view showing the configuration of the antenna according to the fourth embodiment. The components of the antenna according to the fourth embodiment shown in FIGS. 8A and 8B will be described.

  The antenna according to the fourth embodiment includes a dielectric substrate 12, a power feeding unit 11, first to sixth antenna conductors 21 to 26, first to sixth impedance circuit units 31 to 33, and 35 to 37. , First and second connection conductors 15 and 16, line conductor 14, and first and second via groups (not shown).

  Among the components of the antenna according to the fourth embodiment, the first to third antenna conductors 21 to 23 are disposed on the surface of the dielectric substrate 12, and the first and second connection conductors 15 and 16, The line conductor 14 is disposed on the back surface of the dielectric substrate 12. The first and second via groups are provided through the dielectric substrate 12.

  The power feeding unit 11 and the first, second, fourth, and fifth impedance circuit units 31, 32, 35, and 36 are preferably provided on the surface of the dielectric substrate 12, but in other places. It is also possible to provide it. The third and sixth impedance circuit portions 33 and 37 are preferably provided on the back surface of the dielectric substrate 12, but may be provided at other locations.

  The connection relationship of the components of the antenna according to the fourth embodiment will be described. One end of the power feeding unit 11 is connected to one end of the first antenna conductor 21. The other end portion of the first antenna conductor 21 is connected to one end portion of the first impedance circuit portion 31. The other end of the first impedance circuit unit 31 is connected to one end of the second antenna conductor 22. The other end portion of the second antenna conductor 22 is connected to one end portion of the second impedance circuit portion 32. The other end of the second impedance circuit unit 32 is connected to one end of the third antenna conductor 23. One end of each of the first via groups is connected to a predetermined position of the third antenna conductor 23. The other end of each of the first via groups is connected to a predetermined position of the first connection conductor 15. One end portion of the first connection conductor 15 is connected to one end portion of the third impedance circuit portion 33. The other end of the third impedance circuit unit 33 is connected to one end of the line conductor 14.

The other end of the power feeding unit 11 is connected to one end of the fourth antenna conductor 24. The other end of the fourth antenna conductor 24 is connected to one end of the fourth impedance circuit unit 35. The other end of the fourth impedance circuit unit 35 is connected to one end of the fifth antenna conductor 25. The other end portion of the fifth antenna conductor 25 is connected to one end portion of the fifth impedance circuit portion 36. The other end portion of the fifth impedance circuit portion 36 is connected to one end portion of the sixth antenna conductor 26. One end of each of the second via groups is connected to a predetermined position of the sixth antenna conductor 26. The other end of each of the second via groups is connected to a predetermined position of the second connection conductor 16. One end portion of the second connection conductor 16 is connected to one end portion of the sixth impedance circuit portion 37. The other end of the sixth impedance circuit portion 37 is connected to the other end of the line conductor 14.

  In the first impedance circuit unit 31, a varactor C31 and an inductor L31 are connected in parallel between one end and the other end. In the second impedance circuit section 32, a capacitor C32 is connected between one end and the other end. In the third impedance circuit unit 33, a varactor C33 and an inductor L33 are connected in parallel between one end and the other end. In the fourth impedance circuit unit 35, a varactor C35 and an inductor L35 are connected in parallel between one end and the other end. In the fifth impedance circuit section 36, a capacitor C36 is connected between one end and the other end. In the sixth impedance circuit unit 37, a varactor C37 and an inductor L37 are connected in parallel between one end and the other end.

  In other words, in the antenna according to the fourth embodiment shown in FIGS. 8A and 8B, the portions other than the ground conductors 17 and 18 of the antenna according to the first embodiment shown in FIGS. 1B and 1C are folded. Equivalent to a symmetrical arrangement. That is, the 1st-3rd antenna conductors 21-23 by 4th Embodiment, the 1st-3rd impedance circuit parts 31-33, and the connection conductor 15 are the same as that of the case of 1st Embodiment. It is configured. Further, the fourth to sixth antenna conductors 24 to 26, the fourth to sixth impedance circuit portions 35 to 37 and the connection conductor 16 according to the fourth embodiment are the first to third antenna conductors according to the first embodiment. The antenna conductors 21 to 23, the first to third impedance circuit parts 31 to 33, and the connection conductor 15 are configured in a similar manner and are arranged symmetrically with respect to the power feeding part 11. However, the two feeding points of the feeding unit 11 are connected to the first and fourth antenna conductors 21 and 24, respectively, and the line conductor 14 is integrated.

  The differential antenna according to the fourth embodiment shown in FIGS. 8A and 8B can obtain the same characteristics as those of the antenna according to the first embodiment. Similarly, if a part of the antenna according to the fourth embodiment is changed and the capacitors C32 and C36 provided in the second and fifth impedance circuit portions 32 and 36 are replaced with varactors, the antenna according to the second embodiment is obtained. Similar characteristics are obtained. Similarly, if a part of the antenna according to the fourth embodiment is changed and a varactor C34 connected in parallel to the power feeding unit 11 is added, characteristics similar to those of the antenna according to the third embodiment can be obtained.

  Furthermore, even in the differential antenna according to the fourth embodiment shown in FIGS. 8A and 8B, the first impedance circuit unit 31, the third impedance circuit unit 33, the fourth impedance circuit unit 35, and the sixth impedance circuit unit In the impedance circuit unit 37, the connection relationship between the inductor and the varactor may be changed from parallel to serial as shown in FIG. 1E, FIG. 4B, or FIG. 6C. By doing so, the same characteristics as those of the other antennas in the first to third embodiments can be obtained. Furthermore, some of the first impedance circuit unit 31, the third impedance circuit unit 33, the fourth impedance circuit unit 35, and the sixth impedance circuit unit 37 have a series connection configuration, and the rest have a parallel connection configuration. Also good.

  As described above, by using the antenna according to the present invention, it is possible to switch between two operating frequencies without greatly changing the reflection loss, and it is possible to deal with various communication systems with a single antenna. . In particular, since the frequencies of adjacent modes are controlled when dealing with adjacent bands, the difference in resonance frequency that must be essentially changed is small. For this reason, the antenna according to the present invention can easily cope with a close band.

  The invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say. In addition, the features described in the embodiments can be freely combined within a technically consistent range.

DESCRIPTION OF SYMBOLS 11 Feed part 11A, 11B Feed point 12 Dielectric substrate 13, 14 Line conductor 15, 16 Connection conductor 17, 18 Ground conductor 20 Coupling circuit 21-26 Antenna conductor 31-37 Impedance circuit part 41-43 Via group C20, C23, C31 to C34 Capacitance, varactor R20 Resistance L20, L23A, L23B, L31, L33 Inductor

Claims (14)

An antenna having a first resonance frequency that can be adjusted by being included in a first frequency band and a second resonance frequency that can be adjusted by being included in a second frequency band different from the first frequency band,
A power feeding unit;
A first conductor connected to one end of the power feeding unit;
A first impedance circuit unit having one end connected to the first conductor;
A second conductor separated from the first conductor and connected to the other end of the first impedance circuit section;
A second impedance circuit unit having one end connected to the second conductor;
A third conductor separated from the first conductor and the second conductor and connected to the other end of the second impedance circuit section;
A via having one end connected to the third conductor;
A connection conductor separated from the first to third conductors and connected to the other end of the via;
A third impedance circuit unit having one end connected to the connection conductor;
The first to third conductors and the connection conductor are separated from each other, and one end is connected to the third impedance circuit unit, and the other end is connected to the other end of the power feeding unit. Line conductors, and
The first impedance circuit unit includes:
A first inductor connected between the one end and the other end;
A first varactor connected to the first inductor;
The second impedance circuit unit includes:
Comprising a series capacitor connected between the one end and the other end;
The third impedance circuit unit is:
A second inductor connected between the one end and the other end;
A second varactor connected to the second inductor ;
The first resonance frequency can be set to a desired value by adjusting the second impedance value of the third impedance circuit unit while fixing the first impedance value of the first impedance circuit unit, and Even if the first impedance value is changed while the second impedance value is fixed,
The second resonance frequency can be set to a desired value by adjusting the first impedance value while the second impedance value is fixed, and the second resonance frequency is fixed while the first impedance value is fixed. An antenna that remains constant even when the impedance value is changed . The antenna according to claim 1, wherein
A first grounding conductor connected to the one end of the power feeding unit;
A second ground conductor connected to the other end of the line conductor;
A power supply via group connecting the first ground conductor and the second ground conductor;
And further comprising a substrate penetrating the via and the power supply via,
The first to third conductors and the first ground conductor are disposed on one surface of the substrate,
On the other surface of the substrate, the connection conductor, the line conductor and the second ground conductor are disposed,
The first varactor is connected in parallel or in series with the first inductor,
The second varactor is connected in parallel or in series with the second inductor. The antenna according to claim 1 or 2,
The series capacitance is
An antenna with a series varactor. The antenna according to claim 3,
An antenna further comprising a parallel varactor connected in parallel with the power feeding unit. The antenna according to claim 2, wherein
A fourth conductor disposed on the one surface of the substrate and connected to the other end of the power feeding unit;
A fourth impedance circuit unit having one end connected to the fourth conductor;
A fifth conductor disposed on the one surface of the substrate, separated from the first to fourth conductors and the connection conductor, and connected to the other end of the fourth impedance circuit section;
A fifth impedance circuit unit having one end connected to the fifth conductor;
A sixth conductor disposed on the one surface of the substrate, separated from the first to fifth conductors and the connection conductor, and connected to the other end of the fifth impedance circuit section;
Another via penetrating the substrate and having one end connected to the sixth conductor;
Another connection conductor disposed on the other surface of the substrate, separated from the first to sixth conductors and the connection conductor, and connected to the other end of the other via;
A sixth impedance circuit unit, one end of which is connected to the other connection conductor, and the other end of which is connected to the other end of the line conductor;
The fourth impedance circuit unit includes:
A third varactor and a third inductor connected in parallel or in series between the one end and the other end;
The fifth impedance circuit unit is:
Comprising another series capacitance connected between the one end and the other end;
The sixth impedance circuit unit is
An antenna comprising a fourth varactor and a fourth inductor connected in parallel or in series between the one end and the other end. The antenna according to claim 5, wherein
The first conductor and the fourth conductor are symmetric with respect to the power feeding unit,
The second conductor and the fifth conductor are symmetric with respect to the feeding portion,
The third conductor and the sixth conductor are symmetric with respect to the feeding portion,
The connection conductor and the other connection conductor are symmetrical with respect to the power feeding unit. The antenna according to claim 5 or 6,
The series capacitance is
It has a series varactor,
The other series capacitance is
Antenna with other series varactors. The antenna according to claim 7, wherein
An antenna further comprising a parallel varactor connected in parallel to the power feeding unit. The antenna according to any one of claims 1 to 4,
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
An antenna comprising: a second capacitor connected in series to the second diode. The antenna according to claim 3 or 4,
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
A second capacitor connected in series with the second diode;
The series varactor is
A series diode whose capacity changes according to the applied DC voltage;
An antenna comprising: a series capacitor connected in series to the series diode. The antenna according to claim 4, wherein
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
A second capacitor connected in series with the second diode;
The series varactor is
A series diode whose capacity changes according to the applied DC voltage;
A series capacitor connected in series to the series diode;
The parallel varactor is
A diode whose capacitance changes according to the applied DC voltage;
An antenna comprising a capacitor connected in series to the diode. The antenna according to any one of claims 5 to 8,
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
A second capacitor connected in series with the second diode;
The third varactor is
A third diode whose capacitance changes in accordance with the applied DC voltage;
A third capacitor connected in series with the third diode;
The fourth varactor is
A fourth diode whose capacitance changes according to the applied DC voltage;
An antenna comprising: a fourth capacitor connected in series to the fourth diode. The antenna according to claim 7 or 8,
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
A second capacitor connected in series with the second diode;
The third varactor is
A third diode whose capacitance changes in accordance with the applied DC voltage;
A third capacitor connected in series with the third diode;
The fourth varactor is
A fourth diode whose capacitance changes according to the applied DC voltage;
A fourth capacitor connected in series to the fourth diode;
The series varactor is
A series diode whose capacity changes according to the applied DC voltage;
A series capacitor connected in series to the series diode;
The other series varactor is:
Other series diodes whose capacitance changes according to the applied DC voltage,
An antenna comprising: another series capacitor connected in series to the other series diode. The antenna according to claim 8, wherein
The first varactor is
A first diode whose capacity changes in accordance with the applied DC voltage;
A first capacitor connected in series to the first diode;
The second varactor is
A second diode whose capacitance changes in accordance with the applied DC voltage;
A second capacitor connected in series with the second diode;
The third varactor is
A third diode whose capacitance changes in accordance with the applied DC voltage;
A third capacitor connected in series with the third diode;
The fourth varactor is
A fourth diode whose capacitance changes according to the applied DC voltage;
A fourth capacitor connected in series to the fourth diode;
The series varactor is
A series diode whose capacity changes according to the applied DC voltage;
A series capacitor connected in series to the series diode;
The other series varactor is:
Other series diodes whose capacitance changes according to the applied DC voltage,
Another series capacitor connected in series to the other series diode,
The parallel varactor is
A diode whose capacitance changes according to the applied DC voltage;
An antenna comprising a capacitor connected in series to the diode.

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