Antenna device, communication device, matching circuit device

Abstract

This antenna device (201) is provided with a feeder circuit (1) that processes signals in a first frequency band and in a second frequency band that is higher than the first frequency band, a radiating element (2), and a matching circuit (101) connected between the feeder circuit (1) and the radiating element (2). The matching circuit (101) is provided with a first series resonant circuit (RC1) that is connected in series between the radiating element (2) and the feeder circuit (1) and includes a first inductor (LA) and first capacitors (C1A, C1B), and a second inductor (LB) that is shunt-connected between the first series resonant circuit (RC1) and a reference potential and forms a magnetic field coupling with the first inductor (LA). The resonance frequency of the first series resonant circuit (RC1) is in the first frequency band.

Description

[Technical field]

[0001] The present invention relates to an antenna device, a communication device including the same, and a matching circuit device. [Background technology]

[0002] As wireless communication devices such as mobile phones become smaller, antennas also become smaller and their impedance tends to become lower. Therefore, if a feeder circuit and an antenna, whose impedance is much lower than that of the feeder circuit, are matched using a reactance element, the bandwidth becomes narrow.

[0003] On the other hand, one antenna is often made compatible with multiple communication systems. When making it compatible with low-band (e.g., 2.4 GHz band) and high-band (e.g., 5.6 GHz band) communication systems, the fundamental resonance mode and higher-order resonance mode of one radiating element are used. However, since the impedance of the radiating element differs depending on the frequency, if a matching circuit is provided to match one frequency band, matching cannot be achieved at the other frequency.

[0004] In order to solve the above problems, as shown in Patent Document 1, an impedance conversion circuit using a transformer circuit as a matching circuit has been proposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6048593 Summary of the Invention [Problem to be solved by the invention]

[0006] In the impedance conversion circuit described in Patent Document 1, a transformer is provided that includes a first inductor connected in series to a signal line and a second inductor that is magnetically coupled to the first inductor and connected in shunt between the signal line and a reference potential. When impedance matching is performed over a wide band in the high band, the susceptance of the second inductor has a large effect on the low band, causing a large deviation from the impedance matching state. Therefore, the impedance conversion circuit cannot be used in the low band. On the other hand, if impedance matching is newly adjusted for the low band, the loss caused by inserting the impedance conversion circuit increases due to the loss in the circuit.

[0007] Therefore, an object of the present invention is to provide an antenna device capable of reducing the influence of an inductor (second inductor) on the shunt connection side of a transformer for impedance conversion, and ensuring impedance matching in a first frequency band and a second frequency band higher than the first frequency band. 、 A communication device equipped with the same and a matching circuit device for ensuring the impedance matching. The purpose of this invention is to provide [Means for solving the problem]

[0008] (A) An antenna device as an example of the present disclosure is a first frequency band Signal and a power supply circuit for processing signals in a second frequency band higher than the first frequency band. An antenna device connected to the matching circuit includes a first series resonant circuit connected in series between the radiating element and the power feed circuit and including a first inductor and a first capacitor, and a second inductor shunt-connected between the first series resonant circuit and a reference potential and magnetically coupled to the first inductor, and the resonant frequency of the first series resonant circuit is in the first frequency band.

[0009] (B) A communication device as an example of the present disclosure is characterized by including the antenna device described above in (A) and a power supply circuit connected thereto. Effect of the Invention

[0010] According to the present invention, an antenna device is provided that can ensure impedance matching in a first frequency band and a second frequency band higher than the first frequency band by reducing the influence of an inductor on the shunt connection side of a transformer for impedance conversion. 、 A communication device equipped with the same and a matching circuit device for ensuring the impedance matching. is obtained. [Brief description of the drawings]

[0011] [Figure 1] Fig. 1A is a circuit diagram of a matching circuit 101 and a communication device 301 according to the first embodiment. Fig. 1B is a diagram showing the configuration of the communication device 301. [Diagram 2] FIG. 2 is a Smith chart showing frequency characteristics of impedance of the matching circuit 101 according to the first embodiment when viewed from the power feed circuit 1 to the matching circuit 101 side. [Diagram 3] FIG. 3 is a diagram showing frequency characteristics of the magnitude of an S parameter S21 when looking at the matching circuit 101 side from the power supply circuit 1. In FIG. [Figure 4] FIG. 4 is a diagram showing frequency characteristics of the current flowing through each part of matching circuit 101 shown in FIGS. 1(A) and 1(B). [Diagram 5] FIG. 5 is a circuit diagram of a matching circuit 102 and a communication device 302 according to the second embodiment. [Figure 6] FIG. 6 is a Smith chart showing frequency characteristics of impedance of the matching circuit 102 according to the second embodiment when viewed from the power feed circuit 1 to the matching circuit 102 side. [Figure 7] FIG. 7 is a diagram showing frequency characteristics of the current flowing in each part of matching circuit 102 shown in FIG. [Figure 8] FIG. 8 is a circuit diagram of a matching circuit 103 and a communication device 303 according to the third embodiment. [Figure 9] FIG. 9 is a circuit diagram of a matching circuit 104 and a communication device 304 according to the fourth embodiment. [Figure 10] FIG. 10 is a circuit diagram of a matching circuit 105 and a communication device 305 according to the fifth embodiment. [Figure 11]FIG. 11 is a circuit diagram of a matching circuit and a communication device as a comparative example. [Figure 12] FIG. 12 is a Smith chart showing frequency characteristics of impedance of a matching circuit as a comparative example, when viewed from the power feed circuit 1 toward the matching circuit. [Figure 13] FIG. 13 is a diagram showing frequency characteristics of the magnitude of S parameter S21 when looking at the matching circuit side from the power supply circuit 1 shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, several specific examples will be given with reference to the drawings to show several embodiments for carrying out the present invention. In each drawing, the same reference numerals are given to the same parts. In consideration of the ease of explanation or understanding of the main points, the embodiments are shown divided into several embodiments for convenience of explanation, but partial replacement or combination of the configurations shown in different embodiments is possible. In the second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar actions and effects due to similar configurations will not be mentioned in each embodiment.

[0013] First Embodiment 1A is a circuit diagram of a matching circuit 101, an antenna device 201, and a communication device 301 according to the first embodiment.

[0014] The communication device 301 is a mobile phone terminal or the like. FIG. 1(B) shows the main parts inside the housing of the communication device 301. A radiating element 2 and a circuit board are provided inside the housing, and the circuit board is provided with a ground conductor 3, a matching circuit 101 as an impedance matching circuit, and a power supply circuit 1. The matching circuit 101 may be formed by mounting a passive element on the circuit board, or may be formed as one circuit module. Furthermore, the matching circuit 1 may be formed as one circuit module including the power supply circuit 1. The radiating element 2 is a T-branch antenna. The ground conductor 3 acts as an image forming conductor for the radiating element 2, or acts as a radiating element together with the radiating element 2.

[0015] 1(A), communication device 301 includes a radiating element 2, a feeding circuit 1 that feeds a signal to the radiating element 2, and a matching circuit 101. The matching circuit 101 is provided between the feeding circuit 1 and the radiating element 2. The matching circuit 101 and the radiating element 2 configure an antenna device 201. The feeding circuit 1 is a circuit that processes signals in a first frequency band and a second frequency band that is higher than the first frequency band, and is typically a circuit that communicates using signals in the first frequency band and the second frequency band.

[0016] The matching circuit 101 is an impedance matching circuit that matches the feed circuit 1 and the radiating element 2 for low-band and high-band signals. Here, the "low-band" is an example of the "first frequency band" according to the present invention, and the "high-band" is an example of the "second frequency band" according to the present invention.

[0017] The matching circuit 101 includes a signal line SL, a first inductor LA, a second inductor LB, first capacitors C1A and C1B, a second capacitor C2, and a third inductor L2. The signal line SL has an output section OS connected to the radiating element 2 and an input section IS connected to the power supply circuit 1. The first inductor LA and the first capacitors C1A and C1B are connected in series to the signal line SL. The second inductor LB is connected in shunt between the signal line SL and a reference potential (ground potential). A node where the second inductor LB connects to the signal line SL (a node of the shunt connection) is on the connection line between the first inductor LA and the first capacitor C1A.

[0018] The first inductor LA and the second inductor LB are magnetically coupled to each other to form an autotransformer. The first inductor LA and the first capacitors C1A and C1B form a first series resonant circuit RC1.

[0019] The third inductor L2 and the second capacitor C2 are connected in series between the input part IS and the output part OS of the signal line SL. In this example, the third inductor L2 and the second capacitor C2 form a second series resonant circuit RC2.

[0020] The resonant frequency of the first series resonant circuit RC1 is in the low-band frequency band, and the resonant frequency of the second series resonant circuit RC2 is also in the low-band frequency band.

[0021] Fig. 2 is a Smith chart showing frequency characteristics of impedance of the matching circuit 101 according to the first embodiment when viewed from the power feed circuit 1 to the matching circuit 101 side. Fig. 3 is a diagram showing frequency characteristics of the magnitude of an S parameter S21 when viewed from the power feed circuit 1 to the matching circuit 101 side.

[0022] In FIG. 3, characteristic curve A indicates the matching characteristics of matching circuit 101 according to this embodiment, characteristic curve B indicates the matching characteristics of a matching circuit constituted only by a conventional autotransformer, and characteristic curve C indicates the matching characteristics in a state without a matching circuit.

[0023] The constants in Figure 1 are C1A: 6.64pF, C1B: 6.64pF, C2: 2.1pF, LA: 1.3nH, LB: 0.6nH, and L2: 2nH. In Figures 2 and 3, the relationship between each marker and frequency is as follows:

[0024] M01: 2.44GHz M02: 5.15GHz M03: 6.15GHz M04: 7.15GHz 2 and 3, matching is achieved in both the low band (2.4 GHz band) and the high band (5.6 GHz band). Moreover, matching is achieved over a wide band even in the low band.

[0025] In this manner, by using the matching circuit 101 according to this embodiment, the second inductor LB has almost no effect in the low band, and the impedance conversion effect of the autotransformer formed by the first inductor LA and the second inductor LB can be utilized in the high band.

[0026] Furthermore, it is advisable to divide the first capacitor into two, first capacitor C1A and first capacitor C1B, and place them on both ends of the autotransformer. This configuration makes it easier to adjust the impedance in the high band and enables more accurate matching.

[0027] Fig. 4 is a diagram showing the frequency characteristics of the current flowing through each part of the matching circuit 101 shown in Fig. 1(A) and Fig. 1(B). In Fig. 4, characteristic curve A is the frequency characteristic of the current flowing through the input part IS of the matching circuit 101, characteristic curve B is the frequency characteristic of the current flowing through the output part OS of the matching circuit 101, and characteristic curve C is the frequency characteristic of the current flowing on the reference potential (ground) side of the second inductor LB.

[0028] As shown in Fig. 4, in the low band (2.4 GHz), the current flowing to the reference potential (ground) side of the second inductor LB is very small, and it can be seen that the second inductor LB has almost no effect in the low band. This is because the first series resonant circuit RC1 and the second series resonant circuit RC2 each resonate in series in the low band (2.4 GHz), and their reactance becomes approximately 0. In other words, in Fig. 1(A), although the current path C1A-LB or the current path C1B-LA-LB exists, almost no current flows through the second inductor LB, which has a large inductive reactance. Therefore, the second inductor LB has almost no effect in the low band.

[0029] 1A illustrates a matching circuit 101 in which one second series resonant circuit RC2 including the third inductor L2 and the second capacitor C2 is connected in series between the input section IS and the output section OS, but multiple second series resonant circuits RC2 may be connected in series between the input section IS and the output section OS. Even in such a configuration, the first series resonant circuit RC1 and the multiple second series resonant circuits RC2 each resonate in series in the low band (2.4 GHz), and their reactances become approximately 0. As a result, the second inductor LB has almost no effect in the low band.

[0030] Second Embodiment In the second embodiment, an antenna device having a different configuration from the example shown in the first embodiment is provided. 、 Communication Equipment and matching circuit device An example is given below.

[0031] 5 is a circuit diagram of a matching circuit 102, an antenna device 202, and a communication device 302 according to the second embodiment. The communication device 302 includes a radiating element 2, a power feed circuit 1 that feeds power to the radiating element 2, and a matching circuit 102. The matching circuit 102 and the radiating element 2 form the antenna device 202.

[0032] The matching circuit 102 is an impedance matching circuit that matches the feed circuit 1 and the radiating element 2 for low-band and high-band signals.

[0033] The matching circuit 102 includes a signal line SL, a first inductor LA, a second inductor LB, and first capacitors C1A and C1B. The signal line SL has an output OS connected to the radiating element 2 and an input IS connected to the feeding circuit 1. The first inductor LA and the first capacitors C1A and C1B are connected in series to the signal line SL. The second inductor LB is connected in shunt between the signal line SL and a reference potential (ground potential).

[0034] The first inductor LA and the second inductor LB are magnetically coupled to each other to form an autotransformer. The first inductor LA and the first capacitors C1A and C1B form a first series resonant circuit RC1. The resonant frequency of the first series resonant circuit RC1 is in the low band.

[0035] The matching circuit 102 according to this embodiment differs from the matching circuit 101 shown in FIG. 1(A) in that it does not include the second series resonant circuit RC2.

[0036] Fig. 6 is a Smith chart showing frequency characteristics of impedance of the matching circuit 102 according to the second embodiment when viewed from the power feed circuit 1 to the matching circuit 102. In Fig. 6, the relationship between each marker and frequency is the same as that shown in the first embodiment. In the example shown in Fig. 6, there is a frequency band where impedance matching is achieved between 2.44 GHz indicated by marker M01 and 5.15 GHz indicated by marker M02.

[0037] FIG. 7 is a diagram showing frequency characteristics of the current flowing in each part of matching circuit 102 shown in FIG.

[0038] Fig. 11 is a circuit diagram of a matching circuit and a communication device as a comparative example. The matching circuit provided between the power supply circuit 1 and the radiating element 2 includes a signal line SL, a first inductor LA, a second inductor LB, a second capacitor C2, and a third inductor L2. The second inductor LB is connected in shunt between the signal line SL and a reference potential (ground potential). The matching circuit as a comparative example shown in Fig. 11 differs from the matching circuit 101 shown in Fig. 1(A) in that it does not include the first capacitors C1A and C1B.

[0039] 12 is a Smith chart showing the frequency characteristics of impedance of the matching circuit as the comparative example when viewed from the power feed circuit 1. In FIG. 12, the relationship between each marker and frequency is the same as that shown in FIG.

[0040] FIG. 13 is a diagram showing frequency characteristics of currents flowing through the respective parts of the matching circuit shown in FIG.

[0041] 6 and 12, the relationship between each marker and frequency is the same as that shown in the first embodiment. In Fig. 7 and 13, characteristic curve A is the frequency characteristic of the current flowing in the input section IS of the matching circuit, characteristic curve B is the frequency characteristic of the current flowing in the output section OS of the matching circuit, and characteristic curve C is the frequency characteristic of the current flowing on the reference potential (ground) side of the second inductor LB.

[0042] 7, the current (characteristic curve C) flowing through the second inductor LB on the reference potential (ground) side is smaller in the low band (2.4 GHz) than in the comparative example of FIG 13. Also, the current (characteristic curve B) flowing through the output section OS is larger in the low band (2.4 GHz) than in the comparative example of FIG 13. That is, in the comparative example of FIG 11, the effect of the second inductor LB is large in the low band, but in the matching circuit according to this embodiment of FIG 5, the effect of the second inductor LB is small in the low band.

[0043] Third embodiment In the third embodiment, an antenna device having a different configuration from the example shown in the first embodiment is provided. 、 Communication Equipment and matching circuit device An example is given below.

[0044] 8 is a circuit diagram of a matching circuit 103, an antenna device 203, and a communication device 303 according to the third embodiment. The communication device 303 includes a radiating element 2, a power feed circuit 1 that feeds power to the radiating element 2, and a matching circuit 103. The matching circuit 103 is provided between the power feed circuit 1 and the radiating element 2. The matching circuit 103 and the radiating element 2 configure the antenna device 203.

[0045] The matching circuit 103 includes a first series resonant circuit RC1 and a second series resonant circuit RC2. The configuration of the first series resonant circuit RC1 is the same as that of the first series resonant circuit RC1 shown in FIG. 1A. The second series resonant circuit RC2 is configured with a series circuit of a third inductor L2 and a second capacitor C2. In this second series resonant circuit RC2, the connection order of the third inductor L2 and the second capacitor C2 is reversed compared to the second series resonant circuit RC2 shown in FIG. 1A.

[0046] In this way, the third inductor L2 and the second capacitor C2, which are connected in series between the input part IS and the output part OS, may be connected in either order.

[0047] Fourth embodiment In the fourth embodiment, an antenna device including a parasitic capacitance and a parasitic inductance 、 Communication Equipment and matching circuit device An example is given below.

[0048] 9 is a circuit diagram of a matching circuit 104, an antenna device 204, and a communication device 304 according to the fourth embodiment. The communication device 304 includes a radiating element 2, a power feed circuit 1 that feeds power to the radiating element 2, and a matching circuit 104. The matching circuit 104 is provided between the power feed circuit 1 and the radiating element 2. The matching circuit 104 and the radiating element 2 form the antenna device 204.

[0049] The matching circuit 104 includes a first series resonant circuit RC1 and a second series resonant circuit RC2. The first series resonant circuit RC1 includes a first inductor LA connected in series to the signal line, first capacitors C1A and C1B connected in series to the signal line, and a second inductor LB magnetically coupled to the first inductor LA and connected in shunt between the signal line and a reference potential. The first inductor LA and the second inductor LB are magnetically coupled to each other to form an autotransformer. The second series resonant circuit RC2 includes a third inductor L2 and a second capacitor C2 connected in series between the input section IS and the output section OS.

[0050] The first series resonant circuit RC1 includes parasitic capacitances Cp11, Cp12, and Cp13 and parasitic inductances Lp11 and Lp12, while the second series resonant circuit RC2 includes parasitic capacitances Cp21, Cp22, Cp23, and Cp24 and parasitic inductances Lp21 and Lp22.

[0051] The parasitic capacitances Cp11 and Cp13 are parasitic capacitance components occurring between the signal line of the first series resonant circuit RC1 and the reference potential (ground). The parasitic capacitance Cp12 is a parasitic capacitance component occurring in the first inductor LA. The parasitic inductances Lp11 and Lp12 are parasitic inductance components occurring in the signal line of the first series resonant circuit RC1.

[0052] The parasitic capacitances Cp21, Cp22, and Cp24 are parasitic capacitance components occurring between the signal line of the second series resonant circuit RC2 and the reference potential (ground). The parasitic capacitance Cp23 is a parasitic capacitance component occurring in the third inductor L2. The parasitic inductances Lp21 and Lp22 are parasitic inductance components occurring in the signal line of the second series resonant circuit RC2.

[0053] The resonant frequency of the first series resonant circuit RC1 is in the low-band frequency band, and the resonant frequency of the second series resonant circuit RC2 is also in the low-band frequency band.

[0054] As shown in this embodiment, when parasitic components are present in each part of the first series resonant circuit RC1 and the second series resonant circuit RC2, it is sufficient that the resonant frequency of the first series resonant circuit RC1 is in the low band frequency band and the resonant frequency of the second series resonant circuit RC2 is also in the low band frequency band, including these parasitic components.

[0055] In the example shown in FIG. 9, a matching circuit including a first series resonant circuit RC1 and a second series resonant circuit RC2 is illustrated, but similarly, a matching circuit including only the first series resonant circuit RC1 without the second series resonant circuit RC2 may be used as long as the resonant frequency of the first series resonant circuit RC1 is in the low band frequency band with the first series resonant circuit RC1 including a parasitic component.

[0056] Fifth embodiment In the fifth embodiment, an antenna device having a circuit configuration different from the examples shown so far is used. 、 Communication Equipment and matching circuit device An example is given below.

[0057] 10 is a circuit diagram of a matching circuit 105, an antenna device 205, and a communication device 305 according to the fifth embodiment. The communication device 305 includes a radiating element 2, a power feed circuit 1 that feeds power to the radiating element 2, and a matching circuit 105. The matching circuit 105 is provided between the power feed circuit 1 and the radiating element 2. The matching circuit 105 and the radiating element 2 form the antenna device 205.

[0058] The matching circuit 105 includes a first series resonant circuit RC1 and a second series resonant circuit RC2. The first series resonant circuit RC1 and the second series resonant circuit RC2 are connected in parallel. An input circuit MC1 is connected between one end of the parallel connection circuit and the power feed circuit 1. In addition, an output circuit MC2 is connected between the other end of the parallel connection circuit and the radiating element 2.

[0059] The input circuit MC1 and the output circuit MC2 are, for example, an impedance matching circuit or a switch. When the input circuit MC1 is an impedance matching circuit, the input circuit MC1 performs impedance matching between the feed circuit 1 and the parallel circuit. When the output circuit MC2 is an impedance matching circuit, the output circuit MC2 performs impedance matching between the radiating element 2 and the parallel circuit.

[0060] When the input circuit MC1 and the output circuit MC2 are switches, the input circuit MC1 and the output circuit MC2 match impedances in a wider band by switching the matching circuits using the switches.

[0061] In the example shown in FIG. 10, an example is shown in which both the input section circuit MC1 and the output section circuit MC2 are provided, but only one of them may be provided.

[0062] Finally, the present invention is not limited to the above-described embodiments. Appropriate modifications and changes are possible by those skilled in the art. The scope of the present invention is indicated by the claims, not the above-described embodiments. Furthermore, the scope of the present invention includes modifications and changes from the embodiments within the scope of the claims and the equivalent scope. [Explanation of symbols]

[0063] C1A, C1B…First capacitor C2: Second capacitor Cp11, Cp12, Cp13...parasitic capacitance Cp21, Cp22, Cp23, Cp24...parasitic capacitance IS: Input section LA…First inductor LB: Second inductor L2: Third inductor Lp11, Lp12: Parasitic inductance Lp21, Lp22: Parasitic inductance MC1: Input circuit MC2: Output circuit OS: Output section RC1...1st series resonant circuit RC2…Second series resonant circuit SL: Signal line 1...Power supply circuit 2...Radiating element 3…Ground conductor 101~105…matching circuit 201~205…Antenna equipment 301-305: Communication equipment

Claims

1. an antenna device connected to a power supply circuit that processes signals in a first frequency band and signals in a second frequency band higher than the first frequency band, A radiating element; a matching circuit connected between the feeding circuit and the radiating element, The matching circuit includes: a first series resonant circuit connected in series between the radiating element and the feeding circuit, the first series resonant circuit including a first inductor and a first capacitor; a second inductor that is shunt-connected between the first series resonant circuit and a reference potential and that is magnetically coupled to the first inductor; the first capacitor is composed of two or more capacitors; the two or more capacitors include at least one capacitor connected to the power supply circuit side of the node at which the second inductor is shunt-connected, and at least one capacitor connected to the radiating element side; The resonant frequency of the first series resonant circuit is in the first frequency band. Antenna device.

2. a second series resonant circuit connected in series between the radiating element and the feeding circuit and connected in parallel to the first series resonant circuit, the second series resonant circuit including a third inductor and a second capacitor connected in series to the third inductor; the resonant frequency of the second series resonant circuit is in the first frequency band; 2. The antenna device according to claim 1.

3. There are a plurality of the second series resonant circuits.

3. The antenna device according to claim 2.

4. A communication device comprising: the antenna device according to claim 1; and the power supply circuit connected to the antenna device.

5. a matching circuit device connected between a power supply circuit that processes signals in a first frequency band and signals in a second frequency band higher than the first frequency band, and a radiating element; a first series resonant circuit connected in series between the feeding circuit and the radiating element, the first series resonant circuit including a first inductor and a first capacitor; a second inductor that is shunt-connected between the first series resonant circuit and a reference potential and that is magnetically coupled to the first inductor; the first capacitor is composed of two or more capacitors; the two or more capacitors include at least one capacitor connected to the power supply circuit side of the node at which the second inductor is shunt-connected, and at least one capacitor connected to the radiating element side; A matching circuit device, wherein the resonant frequency of the first series resonant circuit is in the first frequency band.

6. A second series resonant circuit is connected in parallel to the first series resonant circuit, the second series resonant circuit including a third inductor and a second capacitor connected in series to the third inductor; the resonant frequency of the second series resonant circuit is in the first frequency band; 6. The matching circuit device according to claim 5.

7. The matching circuit device is formed of one circuit module.

7. A matching circuit device according to claim 5 or 6.

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