JP6330357B2 - Antenna device - Google Patents

Description

  The disclosed embodiment relates to an antenna device or the like.

  In the technical field of mobile communications, various technologies have been developed for the purpose of high-speed, large-capacity and low-delay. For example, in a communication system such as Long Term Evolution (LTE) Advance (LTE-Advance), it is allowed to increase the throughput by simultaneously using a plurality of carrier frequencies. The simultaneous use of a plurality of carrier frequencies is called carrier aggregation (CA).

  There are a number of candidate bands that can be used for carrier aggregation (CA), and the number is increasing. The communication quality of each band varies depending on the communication environment. Therefore, when user equipment (User Equipment: UE) performs carrier aggregation (CA), it is preferable to switch appropriately the band used for actual communication among various candidates.

  One method of switching the band is to change the physical shape of the antenna by switching a switch provided in the middle of the antenna radiation conductor. However, if the physical shape of the antenna changes, the characteristics of the antenna (e.g., the frequency dependence of the reflection coefficient) also change, and the frequency range that can be used before and after the switch is changed within each band. There is concern that it will be impossible to secure.

  Another way to switch bands is to keep the antenna's physical shape unchanged while keeping the antenna always resonant in all bands, whether or not they are actually used in carrier aggregation (CA). It is. In this case, since the physical shape of the antenna does not change, the characteristics do not change. However, since the antenna is not optimized for the band used for actual communication, there is a concern that a frequency range usable in each band cannot be sufficiently secured.

JP 2007-235635 A

  An object of an embodiment in one aspect is to sufficiently secure a bandwidth that can be used for communication in individual bands for carrier aggregation (CA).

The antenna device according to the embodiment
2 to _n C _m matching circuits corresponding to combinations of m bands used simultaneously among n bands provided in advance (n> m ≧ 2);
An antenna having a plurality of resonances and electrically connected to one of the matching circuits;
And a switch for selecting a matching circuit corresponding to a desired combination of m bands to be used at the same time and connecting to the antenna.

  It is possible to secure a sufficient bandwidth that can be used for communication in individual bands for carrier aggregation.

1 is a diagram illustrating a communication device that can be used in an embodiment. FIG. 4 is a diagram showing a specific example of an antenna element A. It shows a circuit example of a case where three matching circuit MAT ₁ -mat ₃ is used. It shows the parameter values of the device used in three circuit example of the matching circuit MAT ₁ -mat _3. The figure for demonstrating a mode that an inconvenience arises when a subswitch is not provided. The figure for demonstrating that a switch should be inserted in an appropriate place. The figure which shows that a switch should be provided between an electric power feeding circuit and a matching circuit. The figure shown with the flowchart of an operation example. The figure which shows the combination which uses two bands among three bands. The figure which shows the conventional antenna device. It shows the frequency dependence of the reflection coefficient S ₁₁ of the the conventional antenna device. The figure which shows the conventional antenna device. It shows the frequency dependence of the reflection coefficient S ₁₁ of the the conventional antenna device. The figure which shows the antenna device ANT by embodiment. It shows the frequency dependence of the reflection coefficient S ₁₁ of the antenna device ANT according to the embodiment. FIG. 4 is a diagram showing a specific example of an antenna element A. The figure which shows an antenna element when switch SW _L12 is closed (SW _L12 = ON). The figure which shows an antenna element when switch SW _L12 is open _| released (SW _L12 = OFF). The figure which shows the combination which uses two bands among five bands. The figure which shows the conventional antenna device. It shows the frequency dependence of the reflection coefficient S ₁₁ of the the conventional antenna device. The figure which shows the frequency dependence of the total efficiency (eta) about the conventional antenna apparatus. The figure which shows the antenna device ANT by embodiment. Diagram illustrating a circuit example in which five of the matching circuit MAT ₁ -mat ₅ is used. Five shows the parameter values of the elements used in the circuit example of the matching circuit MAT ₁ -mat _5. Shows in the antenna device according to the embodiment, the frequency dependence of the reflection coefficient S ₁₁ of the case where a combination of a band to be used has been selected matching circuit MAT ₁ according to was state 1 (LB1, MB) . Diagram showing the frequency dependence of the total efficiency η when the matching circuit MAT ₁ in response to the combination of the band to be used is in a state 1 (LB1, MB) has been selected. Shows in the antenna device according to the embodiment, the frequency dependence of the reflection coefficient S ₁₁ of the case where a combination of a band to be used has been selected matching circuit MAT ₂ in response to was state 2 (LB2, MB) . Diagram showing the frequency dependence of the total efficiency η when the combination of the band to be used matching circuit MAT ₂ in response to was state 2 (LB2, MB) has been selected. Shows in the antenna device according to the embodiment, the frequency dependence of the reflection coefficient S ₁₁ of the case where a combination of a band to be used is state 3 aligned in response to was (LB2, MB) circuit MAT ₃ is selected . Diagram showing the frequency dependence of the total efficiency η when the combination of the band used is state 3 matching circuit MAT ₃ in accordance with (LB2, MB) and which was has been selected. Shows in the antenna device according to the embodiment, the frequency dependence of the reflection coefficient S ₁₁ of the case where a combination of a band to be used is state 4 matching circuit MAT ₄ in response to was (LB2, HB) is selected . Diagram showing the frequency dependence of the total efficiency η when the combination of the band used is state 4 matching circuit MAT ₄ in response to was (LB2, HB) is selected. Shows in the antenna device according to the embodiment, the combination of the band used is state 5 (MB, HB) the frequency dependence of the reflection coefficient S ₁₁ of the case where the matching circuit MAT ₅ in response to which was a is selected . The combination of bands used is state 5 (MB, HB) diagram showing the frequency dependence of the total efficiency η when the matching circuit MAT ₅ in response to was selected.

  Embodiments will be described from the following viewpoints with reference to the accompanying drawings. In the figures, similar elements are given the same reference numbers or reference signs.

1. 1. Communication device Operation 3. Effect 4. Application example (4 bands)
4.1 Antenna device 4.2 Simulation results The classification of these items in the following description is not essential to the embodiment, and the items described in two or more items may be used in combination as necessary. However, matters described in one item may apply to items described in another item (unless they contradict each other).

< 1. Communication device >
FIG. 1 shows a communication device 10 that can be used in the embodiment. The communication device 10 may be any suitable device capable of transmitting and receiving signals. The communication device 10 may be a mobile terminal or a fixed terminal, but at least can perform communication by carrier aggregation (CA). The communication device 10 is specifically a user device such as a user device, a mobile phone, an information terminal, a mobile terminal, a high-performance mobile phone, a smartphone, a personal digital assistant, a stand-alone personal computer, a portable personal computer, or the like. However, the present invention is not limited to this, and may be a system device such as an access point or a base station.

FIG. 1 shows elements related to the embodiment among various elements included in the communication device 10. FIG. 1 shows an antenna element A, an RF module RFM, a filter FIL, a feeding circuit FEED, a matching circuit MAT ₁ -MAT _NA , a main switch SWx, a sub switch SWy ₁ -SWy _NA, and a control circuit CONT. Is shown. In the figure, dotted arrows indicate control signals.

  The antenna element A can be various elements that can be used for wireless communication, but is preferably an element that can resonate in a plurality of bands or bands. For example, when the communication device 10 is a small portable terminal, one antenna element should resonate in a plurality of bands in order to reduce the area or volume occupied by the antenna element.

  FIG. 2 shows a specific example of the antenna element A. In the example shown in FIG. 2, the antenna element A can resonate at the same time in at most three bands. The antenna element A shown in FIG. 2 is formed as a monopole antenna in which an inverted L antenna is combined, but an inverted F antenna or any other structure can be used. As an example, the three bands are a low frequency band (LB), an intermediate frequency band (MB), and a high frequency band (HB). As an example, the low frequency band (LB) is an 800 MHz band, the intermediate frequency band (MB) is a 1.5 GHz band, and the high frequency band (HB) is a 1.7 to 2.1 GHz band.

Antenna element A extends from point Q along the y-axis to point R _M0 and branches in two directions, the one extending to the right reaches point R _M1 , and the one extending along the y-axis extends to point R _HL A line element that branches in two left and right directions and that extends to the left side extends to a point _RH, and that that extends to the right side has a line element extending to a point _RL . An antenna element that resonates in a low-frequency band (LB) is formed by a line element that extends from the point Q to the point _RL through the point _RHL . An antenna element that resonates in an intermediate frequency band (MB) is formed by a line element that extends from the point Q to the point R _M1 through the point R _M0 . An antenna element that resonates in a high-frequency band (HB) is formed by a line element from point Q to point R _HL to point _RH .

  When performing communication using the antenna element A shown in FIG. 2, the following seven states are conceivable.

  State 1: Only the low frequency band (LB) is used for communication.

  State 2: Only the intermediate frequency band (MB) is used for communication.

  State 3: Only the high frequency band (HB) is used for communication.

  State 4: Three low, medium and high frequency bands (LB, MB, LB) are used simultaneously for communication.

  State 5: Two of the three bands, the low frequency band (LB) and the intermediate frequency band (MB), are used for communication at the same time, and the high frequency band (HB) is not used.

  State 6: Two of the three bands, the low frequency band (LB) and the high frequency band (HB), are used for communication at the same time, and the intermediate frequency band (MB) is not used.

  State 7: Of the three bands, two of the intermediate frequency band (MB) and the high frequency band (HB) are used for communication at the same time, and the low frequency band (LB) is not used.

  In the case of state 1-3, it is not considered because it is not carrier aggregation (CA).

  Conventionally, the antenna element A as shown in FIG. 2 resonates in all three bands not only in the state 4 in which three bands are used but also in the state 5-7 in which only two bands are used. Thus, a matching circuit is set. In state 5-7, only two of the three bands are used for communication, so if the matching circuit is set so that communication is possible in all three bands as before, the two bands actually used Each usable bandwidth is narrowed. In the embodiment, in the case of the state 5-7 (when only two of the three bands are used at the same time), the antenna element A is not resonated in all three bands, but the two actually used Any one matching circuit optimized under a relaxed resonance condition is selected as appropriate so as to resonate with the band.

  More generally speaking, the antenna element A can technically resonate in n bands, but the actual number of bands m used for carrier aggregation (CA) was less than n. In this case, the matching circuit is selected so as to resonate in m bands. n is the total number of band candidates that can be used for carrier aggregation (CA), and is an integer of 3 or more. m is the number of bands actually used for carrier aggregation (CA), and is an integer of 2 or more and less than n. From the viewpoint of performing carrier aggregation (CA), the relationship of n ≧ m ≧ 2 is generally satisfied, but in the preferred example, the relationship of n> m ≧ 2 is satisfied. In the case of the above state 5-7, n = 3 and m = 2.

  The RF module RFM shown in FIG. 1 creates a signal that is the basis of a signal to be transmitted through the antenna element A, while restoring the transmitted signal from the signal received through the antenna element A. Perform the process. The signal processing is executed according to the band used for communication.

  The filter FIL passes (combines or separates) a band or band signal used for communication. As an example, when the total number n of usable bands is 3 (n = 3), the filter FIL is a triplexer or demultiplexer that inputs and outputs signals in the low, medium and high frequency bands (LB, MB, HB). It may be formed by a vessel. For example, the triplexer may be formed of a low-pass filter, a high-pass filter, a band-pass filter, or the like. Bands selected by the filter FIL may be determined according to candidate bands used for carrier aggregation (CA).

  The power feeding circuit FEED converts the signal output from the filter FIL into a high-frequency signal to be transmitted via the antenna element A and outputs the high-frequency signal received via the antenna element A inside the communication device 10. Convert to signal and output to filter FIL.

Matching circuits MAT ₁ -MAT _NA are shown in FIG. NA represents a value of 2 or more and _n C _m or less (2 ≦ NA ≦ _n C _m ). However, _n C _m represents the number of combinations when selecting m out of n. _n C _m = _n P _m / m! = n! / [(nm)! m!]. In the case of the above state 5-7, since n = 3 and m = 2, NA is assumed to be ₃ C ₂ = 3. However, if the number of bands n is 3, the communication device 10 can perform communication not only in the state 5-7 but also in the case of the state 1-4. In addition to the matching circuit, there may be a matching circuit for states 1-4. Since the embodiment is advantageous when n> m ≧ 2, in FIG. 1, if there are NA matching circuits (if n = 3, 3 (= ₃ C ₂ ) matchings corresponding to states 5-7 Circuit). Incidentally, when n = 4, m = 2 or 3, and NA is 6 (= ₄ C ₂ ) or 4 (= ₄ C ₃ ). This example will be described in “4. Application Examples”. It is not essential that there are _n C _m matching circuits. Generally, two or more matching circuits only need to exist _n C _m or less, and therefore 2 ≦ NA ≦ _n C _m . This is because when any combination of the m band selection methods is prohibited, a matching circuit corresponding to the prohibited combination is unnecessary.

Each of the matching circuits MAT ₁ -MAT _NA adjusts the impedance of the signal transmission path so that the signal appropriately flows between the portion on the antenna element A side and the portion on the feeding circuit FEED side. Specifically, since the impedance on the antenna element A side is low and the impedance on the feeder circuit FEED side is a matching impedance (for example, 50Ω), the impedance of the transmission path is adjusted so that a high-frequency signal flows appropriately between them. It is adjusted by. The high frequency signal has different frequency components depending on what band is actually used for carrier aggregation (CA). Selection In embodiments, depending on the combination of bands used in carrier aggregation (CA), one of the matching circuit MAT ₁ -mat _NA, by a switch (main switch SWx and the sub switch SWy ₁ -SWy _NA) Is done.

In the case of the above state 5-7, since n = 3 and m = 2, there are three matching circuits MAT ₁ , MAT ₂ , and MAT ₃ . For example, the matching circuit MAT ₁ is optimized so that the antenna element A as shown in FIG. 2 resonates in a low frequency band (LB) and an intermediate frequency band (MB). For example, the matching circuit MAT ₂ is optimized so that the antenna element A resonates in a low frequency band (LB) and a high frequency band (HB). The matching circuit MAT ₃ is optimized so that the antenna element A resonates in an intermediate frequency band (MB) and a high frequency band (HB). In this respect, the present invention is greatly different from the conventional technique in which one matching circuit that always resonates the antenna element A in three bands of low, middle, and high frequencies is used regardless of what band is used.

FIG. 3 shows circuit examples of _three matching circuits MAT ₁ , MAT ₂ , and MAT ₃ when n = 3 and m = 2. A specific circuit for realizing the matching circuit is not limited to the example shown in FIG. 3, and any appropriate circuit capable of adjusting the impedance of the transmission path may be used.

FIG. 4 shows specific values (capacitance of the capacitor and inductance of the inductor) of the elements appearing in the circuit examples of the _three matching circuits MAT ₁ , MAT ₂ , and MAT ₃ shown in FIG. The specific values of the elements shown in FIG. 4 are merely examples, and other values may be used as necessary.

The main switch SWx shown in FIG. 1 selects the matching circuit MAT _i from the NA matching circuits in response to an instruction from the control circuit CONT, and any one of the matching circuits MAT _i is connected to the feeding circuit FEED and A high frequency signal is allowed to flow between the antenna elements A. This selection is performed by the cooperation of the main switch SWx and the sub switches SWy ₁ -SWy _NA . The sub-switch SWy ₁ -SWy _NA is controlled by the control circuit CONT so that any one of the selected matching circuits MAT _i flows a high-frequency signal and the other matching circuits MAT _j (j ≠ i) do not flow a high-frequency signal. It is controlled according to the instruction.

  In the example shown in FIG. 1, an SPKT (Single Pole K Throw) switch having one input port and K output ports is used, but this is not essential to the embodiment. K represents the value of NA. One single input single output (SPST) switch may be used for each matching circuit. In the example shown in FIG. 1, the sub switch is formed by a single input single output (SPST) switch, and the SPST switch is provided for each matching circuit. However, the embodiment is limited to this example. Not. A sub switch may be formed using a SPKT switch. K represents the value of NA.

The control circuit CONT controls operations of various elements included in the communication device 10. For example, the control circuit CONT controls the main switch SWx and the sub switches SWy ₁ -SWy _NA to select the matching circuit. For example, if the matching circuit MAT _i is selected, the control circuit CONT switches the main switch SWx to select the matching circuit MAT _i. Further, along with the operation of the main switch SWx, the control circuit CONT closes the sub switch SWy _i so that the matching circuit MAT _i is connected to a reference potential source (for example, GND), while the matching circuit MAT _j (j ≠ i ) Is opened from the reference potential source so that the sub-switch SWy _j (j ≠ i) is opened. However, 1 ≦ i, j ≦ NA.

The reason why not only the main switch SWx but also the sub switches SWy ₁ -SWy _NA are provided is as follows. Suppose there is no sub-switch SWy ₁ -SWy _NA, and all the MAT ₁ -mat _NA were connected to a reference potential source. For example, in a state where the MAT ₁ -mat ₃ as shown in FIG. 5 is connected to a reference potential source GND, and the matching circuit MAT ₁ by the main switch SWx is selected. Since the matching circuit MAT ₁ is connected in parallel to another matching circuit MAT ₂ and the matching circuit MAT ₃ on the way to the antenna element A, the high-frequency signal is not only the matching circuit MAT ₁ but also the matching circuit MAT _2. And the matching circuit MAT ₃ also flows improperly. In this case, the state of impedance to be realized by the matching circuit MAT ₁ is not optimal for the high-frequency signal. Therefore, in the examples shown in FIGS. 1, 3 and 4, the sub-switch SWy ₁ -SWy _NA is provided, and the unselected matching circuit not selected by the main switch SWx is set to the floating state, and the selected matching circuit is selected. Only have it work properly. That is, not only the main switch SWx but also the sub switches SWy ₁ -SWy _NA are provided so that the high-frequency signal does not flow inappropriately in the non-selected matching circuit that is not selected by the main switch SWx.

In the example shown in FIG. 1, the main switch SWx is provided between the power feeding circuit FEED and the matching circuits MAT ₁ -MAT _NA . From the viewpoint of selecting one of a plurality of matching circuits MAT ₁ -mat _NA, also conceivable to provide the main switch SWx between the matching circuit MAT ₁ -mat _NA and the antenna elements A. However, the main switch SWx is preferably provided between the feeding circuit FEED and the matching circuit MAT ₁ -MAT _NA .

  As shown in FIG. 6, generally, the switch SW related to the antenna is designed to be provided in a transmission path having a matching impedance such as 50Ω, and the performance in that case (for example, the insertion loss is 0.3 dB) Are described in catalogs and specifications. Therefore, even when a switch is used to select the matching circuit, it is preferable to provide the switch SW between the power feeding circuit FEED and the matching circuit MAT as shown in FIG. Since the impedance of the transmission line between the matching circuit MAT and the antenna element A is lower than the matching impedance, if a switch is provided in such a low-impedance location, the performance of the switch indicated in the catalog or specifications should be demonstrated. Cannot be expected. For example, even if the insertion loss is 0.3 dB in catalogs and specifications, there is a concern that if a switch is installed at a location as shown by the dotted line in FIG. 7, the insertion loss due to that switch will become quite large. The

Although not essential, in FIG. 1, antenna element A, matching circuit MAT ₁ -MAT _NA , feeder circuit FEED, main switch SWx and sub switch SWy ₁ -SWy _NA are referred to as elements included in the “antenna device ANT”. May be. A portion of the control circuit CONT that controls switching of the main switch SWx and the sub switches SWy ₁ -SWy _NA may be included in the “antenna device ANT”. However, it should be noted that the block boundaries corresponding to the individual elements in the block diagram are not strict, but merely convenient.

< 2. Action >
FIG. 8 is a flowchart illustrating an example of a procedure executed when the communication device 10 illustrated in FIG. 1 performs communication by carrier aggregation (CA).

  When the flow starts, in step 81, for example, the communication apparatus 10 that is the user apparatus UE, from a communication node such as the base station eNB, determines whether or not communication by carrier aggregation (CA) is possible, and which band may be used. Get notifications about whether or not to use. For example, three bands are available, and carrier aggregation (CA) of two of the three bands is allowed (n = 3 and m = 2).

Next, in step 83, the communication device 10 switches the main switch SWx and the sub switches SWy ₁ -SWy _NA according to the notification. For example, the control circuit CONT switches the main switch SWx to select the matching circuit MAT _i, while connecting the matching circuit MAT _i to a reference potential source GND (closing SWy _i), the matching circuit MAT _{j (j} ≠ i) the separated from the reference potential source (open the SWy _{j (j} ≠ i)) switches the sub switch SWy ₁ -SWy _NA as.

  Next, although it is not essential as indicated by the dotted line, the control circuit CONT changes the configuration of the antenna element A in step 85. When the antenna element A has a structure as shown in FIG. 2, since there is no such switch, step 85 is not executed. In the case of the antenna element A used when described in “4. Application Examples”, a switch for changing the structure of the antenna element A is switched in step 85.

  Next, in step 87, communication by carrier aggregation (CA) is performed using the notified band. Then, the flow ends.

< 3. Effect >
The effect by embodiment is qualitatively demonstrated. For convenience of explanation, it is assumed that an antenna element A as shown in FIG. Therefore, the antenna element A can resonate at the same time in at most three bands. As an example, the three bands are a low frequency band (LB) that is 800 MHz band, an intermediate frequency band (MB) that is 1.5 GHz band, and a high frequency band (HB) that is 1.7 to 2.1 GHz band. To do. It is assumed that the communication apparatus 10 performs communication using two of the three bands simultaneously by carrier aggregation (CA). In this case, three states are possible as shown in FIG. The state 1-3 illustrated in FIG. 9 corresponds to the state 5-7 among the seven states 1-7 that have appeared in the description regarding FIG.

FIG. 10 shows a conventional antenna device shown as a comparative example. The antenna device includes an antenna element Asw, a feed circuit FD, and a matching circuit MT connected between the antenna element Asw and the feed circuit FD. The antenna element Asw can resonate in a total of three bands depending on the states of the switches SW _MH and SW _HL .

Antenna element Asw branches to left and right directions extending from the point Q to the point R _H0, extends to the point R _M who extending to the left through the point R _H1 and switch SW _MH, who extended the right It has a line element that extends to point R _L via point R _H2 and switch SW _HL . The physical shape of the antenna element A is changed by opening and closing the switch SW _MH or SW _HL .

When the switch SW _MH and the switch SW _HL are closed, an antenna element that resonates in a low frequency band (LB) is formed by a line element extending from the point Q to the point R _L through the point R _H0 . Further, the antenna element resonating at the intermediate frequency band (MB) is formed by a line element extending from the point Q to the point R _M through the point R _H0.

When the switch SW _HL is closed and the switch SW _MH is opened, an antenna element that resonates in a low frequency band (LB) is formed by a line element from the point Q to the point R _L through the point R _H0. . Further, an antenna element that resonates in a high frequency band (HB) is formed by a line element extending from the point Q to the point R _H1 through the point R _H0 .

When the switch SW _MH is closed and the switch SW _HL is opened, the antenna element resonating at the intermediate frequency band (MB) is formed by a line element extending from the point Q to the point R _M through the point R _H0. Further, an antenna element that resonates in a high frequency band (HB) is formed by a line element extending from the point Q to the point R _H2 through the point R _H0 .

Figure 11 qualitatively illustrates the frequency dependence of the reflection coefficient or S parameter S ₁₁ of the antenna device shown in FIG. 10. A thick solid line and a thick dotted line correspond to the case where the switch SW _MH and the switch SW _HL are closed. In this case, the antenna apparatus resonates in a low frequency band (LB) and an intermediate frequency band (MB) corresponding to the state 1 in FIG. A thin dotted line and a thin alternate long and short dash line correspond to a case where the switch SW _MH is closed and the switch SW _HL is opened. In this case, the antenna device resonates in an intermediate frequency band (MB) and a high frequency band (HB) corresponding to the state 3 in FIG. In either case, communication is performed in the intermediate frequency band (MB), but the reflection to the intermediate frequency band (MB) is caused by the change in the shape of the antenna element Asw by opening and closing the switches SW _MH and SW _HL. The frequency dependency of the coefficient S11 also varies. For this reason, in the intermediate frequency band (MB), the usable bandwidth becomes narrow regardless of switching of the switch.

FIG. 12 shows a conventional antenna device shown as a comparative example. The antenna device includes an antenna element A _ALL , a feed circuit FD, and a matching circuit MT connected between the antenna element A _ALL and the feed circuit FD. The physical shape (geometric shape) of the antenna element A _{ALL is} the same as that of the antenna element A shown in FIG. 2, but the matching circuit MT is set so as to resonate in all three bands. This is different from the antenna device ANT shown in FIG.

Figure 13 qualitatively illustrates the frequency dependence of the reflection coefficient or S parameter S ₁₁ of the antenna device shown in FIG. 12. There are three types of antenna devices, a low frequency band (LB), an intermediate frequency band (MB), and a high frequency band (HB), regardless of which band is actually used in carrier aggregation (CA). It always resonates in all bands. For this reason, the bandwidth that can be used in each band is narrowed.

  FIG. 14 shows an antenna device ANT according to the embodiment. The antenna device ANT shown in FIG. 14 is a simplified depiction of the antenna device ANT shown in FIG. 1 (therefore, the configuration and operation of the device are the same as the example shown in FIG. 1).

Figure 15 qualitatively illustrates the frequency dependence of the antenna reflection coefficient of the device ANT or S parameter S ₁₁ shown in FIG. 1 and FIG. 14. The antenna device ANT selects any one of the _three matching circuits MAT _{1 to} MAT ₃ depending on which band is actually used in the carrier aggregation (CA). Therefore, in the state where the low frequency band (LB) and the intermediate frequency band (MB) are used (state 1 in FIG. 9), the matching circuit MAT ₁ optimized for these two bands is performed. The frequency dependence of the reflection coefficient S _{11 in this} case is shown by a thick solid line and a thick dotted line in FIG. In the case where the intermediate frequency band (MB) and the high frequency band (HB) are used (state 3 in FIG. 9), the matching circuit MAT ₃ optimized for these two bands is performed. The frequency dependence of the reflection coefficient S ₁₁ is indicated by a thin dotted line and a thin one-dot chain line in FIG.

Comparing FIG. 11 (conventional example for switching the antenna shape), FIG. 13 (conventional example always resonating in three bands) and FIG. 15 (embodiment), in the embodiment (FIG. 15), the antenna element A shape is unchanged, because only occurs characteristic variation due to the switching of the matching circuit, the frequency dependence of the reflection coefficient S ₁₁ of the antenna device hardly changes. For this reason, in the example shown in FIG. 15, the characteristic with respect to the band (MB) of the intermediate frequency hardly fluctuates. In addition, the matching circuit is optimized for two bands that are actually used, and it is not always necessary to resonate in the three bands. Therefore, the usable bandwidth in each band is not narrowed.

  More generally speaking, according to the embodiment, when m <n, the number of resonances of the antenna is deliberately reduced from the maximum number without changing the shape of the antenna. n is the number of bands in which the antenna can resonate. m is the number of bands m actually used for carrier aggregation (CA). Each of the plurality of matching circuits is optimized for each combination of bands actually used. In the embodiment, one optimum matching circuit is selected from the plurality of matching circuits according to the combination of bands actually used (FIG. 9). As a result, even if the choices of bands for carrier aggregation increase, a sufficiently wide bandwidth that can be used for communication in each band can be secured.

< 4. Application example (4 bands) >
Next, an application example in which there are four carrier aggregation (CA) band candidates and carrier aggregation (CA) is performed using two of the four bands will be considered.

< 4.1 Antenna device >
FIG. 16 shows a specific example of the antenna element A that can be used as the antenna element A of FIG. In the example shown in FIG. 16, the antenna element A can resonate at the same time in at most four bands. The antenna element A shown in FIG. 16 is formed as a monopole antenna in which an inverted L antenna is combined, but an inverted F antenna or any other structure can be used. As an example, the four bands are a first low frequency band (LB1), a second low frequency band (LB2), an intermediate frequency band (MB), and a high frequency band (HB). As an example, the first low frequency band (LB1) is 700MHz band, the second low frequency band (LB2) is 800MHz band, the intermediate frequency band (MB) is 1.5GHz band, and the high frequency band (HB ) Is the 1.7-2.1 GHz band.

Antenna element A extends from point Q along the y-axis to point R _M0 and branches in two directions, the one extending to the right reaches point R _M1 , and the one extending along the y-axis extends to point R _HL The one branching left and right and extending to the left side has a line element extending to the point _RH , and the one extending to the right side has a line element extending to the point R _L1 via the point R _L2 and the switch SW _L12 .

As shown in FIG. 17, when the switch SW _L12 is closed (SW _L12 = ON), the first low-frequency band by the line elements from the point R _L1 through the point R _HL from the point Q (LB1) A resonant antenna element is formed. Further, an antenna element that resonates in a band (MB) of an intermediate frequency is formed by a line element extending from the point Q to the point R _M1 through the point R _M0 . Furthermore, the antenna element resonating at a high frequency band (HB) is formed by a line element extending from the point Q to the point R _H through the point R _HL.

As shown in FIG. 18, when the switch SW _L12 is opened (SW _L12 = OFF), the second low frequency band by the line elements from the point R _L2 through the point R _HL from the point Q (LB2) A resonant antenna element is formed. Further, an antenna element that resonates in a band (MB) of an intermediate frequency is formed by a line element extending from the point Q to the point R _M1 through the point R _M0 . Furthermore, the antenna element resonating at a high frequency band (HB) is formed by a line element extending from the point Q to the point R _H through the point R _HL.

Therefore, two antenna elements that can resonate at most in three bands are switched by opening and closing the switch SW _L12 . When antenna element A shown in FIG. 16 is used, combinations of bands using two of the four bands for carrier aggregation (CA) can be expressed as the following five states (FIG. 19).

  State 1: The first low frequency band (LB1) and the intermediate frequency band (MB) are used.

  State 2: The first low frequency band (LB1) and the high frequency band (HB) are used.

  State 3: The second low frequency band (LB2) and the intermediate frequency band (MB) are used.

  State 4: The second low frequency band (LB2) and the high frequency band (HB) are used.

  State 5: An intermediate frequency band (MB) and a high frequency band (HB) are used.

As shown in FIG. 17 and FIG. 18, which of the first and second low frequency bands (LB1, LB2) is used is switched by switching the switch SW _L12 . Therefore, there is a restriction that the first and second low frequency bands (LB1, LB2) cannot be used simultaneously. However, this restriction is only a limitation caused by using the antenna element A as shown in FIG. 16, and is not essential. By using other antenna element structures, simultaneous use of the first and second low-frequency bands (LB1, LB2) may be realized.

< 4.2 Simulation results >
FIG. 20 shows a conventional antenna device shown as a comparative example. The antenna device includes an antenna element Asw, a feed circuit FD, and a matching circuit MT connected between the antenna element Asw and the feed circuit FD. Similarly to the antenna element A shown in FIG. 16, the antenna element Asw can switch between two states that can resonate at most in three bands according to the state of the switch SW _L12 . Specifically, (i) a state that resonates in at most three bands, a first low frequency (LB1), an intermediate frequency (MB), and a high frequency band (HB), and (ii) a second low frequency ( LB2), an intermediate frequency (MB), and a high frequency band (HB) can be switched between states that resonate with at most three bands. Therefore, in the matching circuit MT, when the state of the switch SW _L12 is (i), the antenna device resonates in the three bands of the first low frequency (LB1), the intermediate frequency (MB), and the high frequency (HB). It is set to be. Furthermore, in the matching circuit MT, when the state of the switch SW _L12 is (ii), the antenna device resonates in three bands of the second low frequency (LB2), intermediate frequency (MB), and high frequency (HB). It is set to be.

Figure 21 shows the frequency dependence of the reflection coefficient or S parameter S ₁₁ of the antenna device shown in FIG. 20. A thick solid line, a thick dotted line, and a thick alternate long and short dash line correspond to the case where the switch SW _L12 is closed (in the case of (i) above). A thin solid line, a thin dotted line, and a thin alternate long and short dash line correspond to the case where the switch SW _L12 is opened (in the case of (ii) above). In the case of (i), the antenna device uses the first low frequency (LB1), intermediate frequency (MB), and high frequency bands (irrespective of which band is actually used in carrier aggregation (CA) ( Resonates in three bands called HB). In the case of (ii), the antenna device uses the second low frequency (LB2), intermediate frequency (MB), and high frequency bands (irrespective of which band is actually used in carrier aggregation (CA) ( Resonates in three bands called HB). Since the band which does not need to resonate also resonates, the usable bandwidth in each band is narrowed.

FIG. 22 shows the frequency dependence of the total efficiency η [dB] for the antenna device as shown in FIG. Total efficiency η is a reference power P _ref outputted from the power supply circuit FD, it is derived from the ratio of the radiation power P _rad actually radiated from the antenna element Asw. That is, η∝log ₁₀ (P _rad / P _ref ).

First, as shown in the upper side of FIG. 22, high efficiency of about −4 dB is achieved in the first low frequency band (LB1), and about −2 dB in the second low frequency band (LB1). High efficiency is achieved. However, by switching the switch SW _L12 , as shown in the lower side of FIG. 22, the efficiency with respect to the band (MB) of the intermediate frequency is greatly degraded by about 4 dB from about −2 dB to about −6 dB. This is because, in FIG. 21, by switching the switch SW _L12, the reflection coefficient S ₁₁ corresponds to that they've vary greatly in the band of the intermediate frequency (MB). As shown in FIG. 22, the efficiency for the high frequency band (HB) is degraded by about 1.5 dB from about −5.5 dB to about −7 dB (at 1.7 GHz). The degree of degradation for the high frequency band (HB) is been finished less, at 21, by switching the switch SW _L12, the reflection coefficient S ₁₁ is not significantly varied in the high frequency band (HB) Corresponding to

FIG. 23 shows an antenna device ANT according to the embodiment. The antenna device ANT shown in FIG. 23 is a simplified depiction of the antenna device ANT shown in FIG. 1 (therefore, the configuration and operation of the device are the same as the example shown in FIG. 1). In the antenna device shown in FIG. 23, the antenna element A is the same as the antenna element Asw in FIG. 20, but any one of the _five matching circuits MAT _{1 to} MAT ₅ is selectively used. However, this is different from the conventional antenna apparatus shown in FIG.

FIG. 24 shows a specific circuit example of the _five matching circuits MAT _{1 to} MAT ₅ shown in FIG. Since n = 4 and m = 2 and _n C _m = ₄ C ₂ = 6, NA is 2 or more and 6 or less. Since the combination of the first and second low frequency bands (the combination of LB1 and LB2) is excluded, NA is 2 or more and 5 or less. In the examples shown in FIGS. 23 and 24, NA = 5. A specific circuit for realizing the matching circuits MAT _{1 to} MAT ₅ is not limited to the example shown in FIG. 24, and any appropriate circuit capable of adjusting the impedance of the transmission path may be used.

FIG. 25 shows specific values (capacitance of the capacitor and inductance of the inductor) of elements appearing in the circuit example of the _five matching circuits MAT _{1 to} MAT ₅ shown in FIG. The specific values of the elements shown in FIG. 25 are merely examples, and other values may be used as necessary.

[State 1 (LB1, MB)]
FIG. 26 shows a reflection coefficient S ₁₁ when the matching circuit MAT ₁ is selected in accordance with the combination of bands used in the antenna device shown in FIG. 23 being in state 1 (LB1, MB) in FIG. The frequency dependence of is shown. In the figure, the graphs of LB1, MB, and HB correspond to the portions LB1, MB, and HB of the antenna elements (FIG. 23) that resonate in individual bands, respectively. The reflection coefficient S ₁₁ reaches a considerably low value (about -7.5 dB at the peak) over a relatively wide range of the first low-frequency band (LB1: 700 MHz band). Further, the reflection coefficient S ₁₁ reaches a considerably low value over a relatively wide range of the intermediate frequency band (MB: 1.5 GHz band).

FIG. 27 shows the frequency dependence of the total efficiency η [dB] when the matching circuit MAT ₂ is selected according to the combination of bands used in state 1 (LB1, MB) of FIG. . Total efficiency η is a reference power P _ref outputted from the power supply circuit FEED, it is derived from the ratio of the radiation power P _rad actually radiated from the antenna element A. That is, η∝log ₁₀ (P _rad / P _ref ). In the first low frequency band (LB1), a high efficiency of about −4 dB is achieved. Even in the intermediate frequency band (MB), a high efficiency of about -4 dB is achieved.

[State 2 (LB1, HB)]
FIG. 28 shows a reflection coefficient S ₁₁ when the matching circuit MAT ₂ is selected in accordance with the combination of bands used in the antenna device shown in FIG. 23 being in state 2 (LB1, HB) in FIG. The frequency dependence of is shown. In the figure, the graphs of LB1, MB, and HB correspond to the portions LB1, MB, and HB of the antenna elements (FIG. 23) that resonate in individual bands, respectively. The reflection coefficient S ₁₁ reaches a considerably low value (about −9 dB at the peak) over a relatively wide range of the first low-frequency band (LB1: 700 MHz band). Further, the reflection coefficient S _11, the high frequency band: over a relatively wide range of (HB 1.7~2.1GHz band), has reached a fairly low value.

FIG. 29 shows the frequency dependence of the total efficiency η [dB] when the matching circuit MAT ₂ is selected according to the combination of bands used in state 2 (LB1, HB) of FIG. . In the first low frequency band (LB1), a high efficiency of about −4 dB is achieved. Even in the high frequency band (HB), a high efficiency of about -2 dB is achieved.

[State 3 (LB2, MB)]
FIG. 30 shows a reflection coefficient S ₁₁ when the matching circuit MAT ₃ is selected in accordance with the combination of bands used in state 3 (LB2, MB) in FIG. 19 in the antenna device shown in FIG. The frequency dependence of is shown. In the figure, the graphs of LB2, MB, and HB correspond to the portions LB2, MB, and HB of the antenna elements (FIG. 23) that resonate in individual bands, respectively. The reflection coefficient S ₁₁ reaches a considerably low value (about -14 dB at the peak) over a relatively wide range of the second low-frequency band (LB2: 800 MHz band). Further, the reflection coefficient S ₁₁ reaches a considerably low value over a relatively wide range of the intermediate frequency band (MB: 1.5 GHz band).

FIG. 31 shows the frequency dependence of the total efficiency η [dB] when the matching circuit MAT ₃ is selected according to the combination of bands used in state 3 (LB2, MB) of FIG. . In the second low frequency band (LB2), a high efficiency of about −3 dB is achieved. Even in the intermediate frequency band (MB), high efficiency of about −3 dB is achieved.

[State 4 (LB2, HB)]
FIG. 32 shows a reflection coefficient S ₁₁ when the matching circuit MAT ₄ is selected in accordance with the combination of bands used in the antenna device shown in FIG. 23 being in state 4 (LB2, HB) in FIG. The frequency dependence of is shown. In the figure, the graphs of LB2, MB, and HB correspond to the portions LB2, MB, and HB of the antenna elements (FIG. 23) that resonate in individual bands, respectively. The reflection coefficient S ₁₁ reaches a considerably low value (about -14 dB at the peak) over a relatively wide range of the second low-frequency band (LB2: 800 MHz band). Further, the reflection coefficient S _11, the high frequency band: over a relatively wide range of (HB 1.7~2.1GHz band), has reached a fairly low value.

FIG. 33 shows the frequency dependence of the total efficiency η [dB] when the matching circuit MAT ₄ is selected according to the combination of bands used in state 4 (LB2, HB) of FIG. . In the second low frequency band (LB2), a high efficiency of about −3 dB is achieved. Even in the high frequency band (HB), a high efficiency of about -2 dB is achieved.

[State 5 (MB, HB)]
FIG. 34 shows a reflection coefficient S ₁₁ when the matching circuit MAT ₅ is selected in response to the combination of bands used in the antenna device shown in FIG. 23 being in state 5 (MB, HB) in FIG. The frequency dependence of is shown. In the figure, the graphs of LB1 or LB2, MB, and HB correspond to the portions LB1 or LB2, MB, and HB of the antenna elements (FIG. 23) that resonate in individual bands, respectively. Reflection coefficient S _11, the intermediate frequency band: over a relatively wide range of (MB 1.5 GHz band), has reached a fairly low value. Further, the reflection coefficient S _11, the high frequency band: over a relatively wide range of (HB 1.7~2.1GHz band), has reached a fairly low value.

FIG. 35 shows the frequency dependence of the total efficiency η [dB] when the matching circuit MAT ₅ is selected according to the combination of bands used in the state 5 (MB, HB) of FIG. . A high efficiency of about -4 dB is achieved in the intermediate frequency band (MB). Even in the high frequency band (HB), a high efficiency of about -4 dB is achieved.

[effect]
In the embodiment, when the combination of bands actually used is any one of the states 1-5 (for example, the state 1 (LB1, MB)), the antenna device has a performance capable of resonating in three bands. If so, a matching circuit optimized for that state (eg, state 1) is used. One matching circuit that resonates in all bands is not always used, but a matching circuit with a small number of resonances is used. The main switch SWx and the sub switch are connected so that the matching circuit (for example, MAT ₁ ) optimized for the state is connected to the antenna element A and the other matching circuits (for example, MAT ₂ -MAT ₅ ) are in a floating state. SWy ₁ -SWy ₅ are controlled. As a result, communication can be performed in a state suitable for transmitting and receiving a high-frequency signal in a band actually used. For example, communication can be performed using an antenna device that operates in a relaxed resonance state that only needs to resonate with LB1 and MB in state 1 (LB1, MB). Even if the number of band options for carrier aggregation (CA) increases by selecting a matching circuit optimized for each band combination according to the band combination actually used, communication is performed in each band. The available bandwidth can be secured widely.

Comparing the simulation results for state 1 (LB1, MB) (Figs. 26, 27) with the simulation results for state 3 (LB2, MB) (Figs. 30, 31), the switch SW _L12 was switched. You can see what effect occurred on the intermediate frequency band (MB). In FIG. 26 relating to state 1, the reflection coefficient S ₁₁ is low in the range of about 1.2 GHz to about 1.6 GHz, and in FIG. 30 relating to state 3, the reflection coefficient S ₁₁ is low in the range of about 1.4 GHz to about 1.6 GHz. It has become. In FIG. 27 for state 1 and FIG. 31 for state 3, similar total efficiencies are achieved over a range of about 1.3 GHz to about 1.6 GHz. Therefore, it can be seen that the reflection coefficient S ₁₁ and the total efficiency η related to the band (MB) of the intermediate frequency are the same before and after the switch SW _L12 is switched.

Comparing the simulation results for state 2 (LB1, HB) (Figs. 28, 29) and the simulation results for state 4 (LB2, HB) (Figs. 32, 33), switching switch SW _L12 You can see how the high frequency band (HB) is affected. In FIG. 28 relating to state 2, the reflection coefficient S ₁₁ is low in the range of about 1.8 GHz to about 2.5 GHz, and in FIG. 32 relating to state 4, the reflection coefficient S ₁₁ is low in the range of about 1.7 GHz to about 2.4 GHz. It has become. In FIG. 29 for state 2 and FIG. 33 for state 4, similar total efficiencies are achieved over a range of about 1.6 GHz to about 2.1 GHz. Thus, the reflection coefficient S ₁₁ and total efficiency η to a high frequency band (HB), is found to be similar before and after switching the switch SW _L12.

Thus, the shape of the antenna elements A, although the changeover switch SW _L12 shape changes, an intermediate frequency band (MB) and a high frequency band (HB) antenna characteristics regarding (a reflection coefficient S ₁₁ and total efficiency eta) Can be made substantially unchanged.

  As described above, the communication apparatus that performs carrier aggregation (CA) of two bands and the antenna apparatus therefor have been described, but the embodiments are not limited to the examples described in the specific examples, and those skilled in the art will recognize various modifications. You will understand modifications, alternatives, substitutions, etc. Although specific numerical examples have been described to facilitate understanding of the embodiment, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. The classification of items in the above description is not essential to the disclosed embodiment, and items described in two or more items may be used in combination as necessary, or items described in a certain item May apply to matters described in other items (unless they conflict). For convenience of explanation, the devices used in the embodiments have been described with functional block diagrams, but it should be noted that the boundaries of the individual blocks shown in the block diagrams do not necessarily correspond to physical boundaries. Cost. The function of an element expressed in one block may be physically demonstrated in multiple parts, and conversely, the function of an element expressed in multiple blocks is physically demonstrated in one part. May be. In the above description, it should be noted that “embodiments” do not necessarily indicate the same forms. The embodiments are not limited to the above examples, and various modifications, modifications, alternatives, substitutions, and the like will be apparent to those skilled in the art without departing from the spirit of the disclosed embodiments. Such variations, modifications, alternatives, substitutions and the like are intended to be included within the scope of the appended claims.

Regarding the above embodiment, the following additional notes are disclosed.
(Appendix 1)
2 to _n C _m matching circuits corresponding to combinations of m bands used simultaneously among n bands provided in advance (n> m ≧ 2);
An antenna having a plurality of resonances and electrically connected to one of the matching circuits;
An antenna device comprising: a switch that selects a matching circuit corresponding to a desired combination of m bands to be used simultaneously and connects to the antenna.
(Appendix 2)
The antenna device according to appendix 1, further comprising a sub switch that connects or separates each of the two or more _n C _m or less matching circuits and a reference potential source.
(Appendix 3)
The antenna device according to attachment 2, further comprising a control circuit that controls operations of the switch and the sub-switch.
(Appendix 4)
The control circuit connects the sub-switch so that a matching circuit electrically connected to the antenna is connected to the reference potential source, and a matching circuit not electrically connected to the antenna is separated from the reference potential source. 4. The antenna device according to appendix 3, which controls the operation of.
(Appendix 5)
The antenna device according to any one of appendices 1 to 4, wherein the switch is provided between the two or more _n C _m or less matching circuits and a power feeding circuit.
(Appendix 6)
The antenna device according to any one of appendices 1 to 5, wherein the m bands to be used simultaneously are used for communication by carrier aggregation.
(Appendix 7)
The antenna device according to any one of appendices 1 to 6, wherein the antenna is formed by a monopole antenna having two or more branches.

A Antenna element
RFM RF module
FIL filter
FEED feeding circuit
MAT ₁ -MAT _NA matching circuit
SWx main switch
SWy ₁ -SWy _NA sub switch
CONT control circuit

Claims (4)

Optimized more than _n C _m or less and the matching circuit in pairs to the combination of the m band used at the same time among the n bands which is previously set in the communication system (n> m ≧ 2 ),
An antenna capable of resonating in the n bands and electrically connected to one of the matching circuits;
It provided between the two or more _n C _m or less matching the feeding circuit, and the antenna select an optimized matching circuit against the desired combination of m band used at the same time possess a switch for connecting, the m band used at the same time is used for communication by the carrier aggregation, the antenna device. 2. The antenna device according to claim 1, further comprising a sub-switch for connecting or separating each of the two or more _n C _m or less matching circuits and a reference potential source.   The antenna device according to claim 2, further comprising a control circuit that controls operations of the switch and the sub switch.   The control circuit connects the sub-switch so that a matching circuit electrically connected to the antenna is connected to the reference potential source, and a matching circuit not electrically connected to the antenna is separated from the reference potential source. The antenna device according to claim 3, wherein the operation of the antenna device is controlled.

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