JP2014127808A - Variable frequency antenna device, and mobile terminal electronic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna device corresponding to a plurality of frequencies without the need of a control circuit that requires advanced operation, with an arbitrarily variable radiation element length by a switching element.SOLUTION: A variable frequency antenna 1, including a first switching element 3a and a second switching element 3b disposed on a radiation element, further includes: a voltage supply terminal for applying each control voltage to the first switching element 3a and the second switching element 3b; a first voltage division circuit having one end connected to the voltage supply terminal and the other end connected to one end of the first switching element 3a; and a second voltage division circuit having one end connected to the voltage supply terminal and the other end connected to one end of the second switching element 3b. Using a single external voltage supply source, the first and second switching elements 3a and 3b are controlled simultaneously.

Description

  The present invention relates to a variable frequency antenna device provided with a switching element for adjusting the electrical length of an antenna, and a portable terminal electronic device using the same.

  In recent years, in wireless devices such as mobile phones, the number of antennas tends to increase as the number of wireless systems increases. Further, the occupied volume allowed for the antenna tends to be reduced, and there is a strong demand for downsizing the built-in antenna. However, the antenna characteristics are generally in a trade-off relationship with the size, and with the progress of miniaturization, narrowing of the frequency band and deterioration of efficiency become problems.

JP 2004-96341 A

  Patent Document 1 discloses an antenna device in which a plurality of switching elements are inserted in the middle of a radiating element of an inverted-F antenna. In this antenna device, the ON / OFF operation of the switching element can be controlled by a control circuit, and the electrical length of the antenna can be varied arbitrarily. As a result, an antenna having a resonance frequency corresponding to the electrical length can be realized, so that it is possible to adjust to a wide frequency band range with one antenna. However, since this method requires a control circuit for performing advanced control, problems such as an increase in the number of parts, an increase in the occupied area, and an increase in cost cannot be avoided. Further, in further narrowing of the adjacency, degradation of antenna characteristics due to interference between the control line connected from the control circuit to the switching element and the radiating element becomes a problem.

  The present invention has been made in view of the above, and is capable of operating with a control circuit configured with a simple circuit and capable of suppressing deterioration of antenna characteristics due to interference, and an antenna device using the same An object of the present invention is to provide a portable terminal electronic device.

  In order to achieve the above object, an antenna device according to the present invention includes an open-ended linear radiating element in which a plurality of parts are physically separated, and a plurality of switching elements that electrically connect or disconnect the separated part. An antenna device comprising: a first switching element on a feeding side on a radiation element; a second switching element on a tip side; and a radiation element between the first switching element and the second switching element. A first capacitor is inserted above, a voltage supply terminal for applying a control voltage to the first switching element and the second switching element, one end connected to the voltage supply terminal, and the other end to the first switching element A first voltage dividing circuit connected to one end of the second switching circuit, one end connected to the voltage supply terminal, and the other end connected to one end of the second switching element. Further comprising a composed controller from the second voltage dividing circuit to the first feature.

  According to the present invention having the above characteristics, it is possible to sequentially extend the electrical length of the radiating element in terms of high frequency by sequentially turning on the plurality of switching elements from the antenna feeding side. Basically, the resonant frequency of the antenna is determined by the length of the radiating element, and therefore, by arranging the switching element at a location designed in advance, it is possible to arbitrarily vary a plurality of frequencies. Specifically, the shortest radiating element can be realized by turning off the first switching element and the second switching element.

  Next, by turning on the first switching element and turning off the second switching element, a radiation element having the second length can be realized. Finally, the longest radiating element can be realized by turning on the first switching element and the second switching element. From the above, by adjusting the ON / OFF timing of each switching element, it is possible to realize three types of radiating elements, thereby realizing three types of resonance frequencies.

  Further, according to the antenna device having the above characteristics, the first switching element is turned ON first by continuously applying a voltage from the voltage supply terminal. Thereafter, when a voltage is applied, the first and second switching elements are simultaneously turned ON. For this reason, the antenna device of the present invention can select three types of length of the radiating element, and can vary the resonance frequency of the antenna over a wide range.

  Furthermore, the switching device of the antenna device according to the present invention is characterized in that it is a PIN diode.

  According to the antenna device having the above characteristics, the switching element can be reduced in size by using the PIN diode, and therefore the size of the entire control circuit can be reduced.

  Furthermore, the antenna device according to the present invention includes, as the first voltage dividing circuit, a first resistor having one end connected to the voltage supply terminal and one end connected to the other end of the first resistor. Is composed of a second resistor connected to a reference potential, and as a second voltage dividing circuit, a third resistor having one end connected to the voltage supply terminal and one end connected to the other end of the third resistor A third feature is that the second resistor is connected and connected to the reference potential at the other end.

  According to the antenna device having the above characteristics, it is possible to reduce the size of the control circuit by using a resistance element as a component of the voltage dividing circuit, and therefore the size of the entire matching circuit can also be reduced.

  Furthermore, a fourth feature is that the insertion position of the first capacitor on the radiating element of the antenna device according to the present invention is the latter stage of the second switching element.

  According to the antenna device having the above characteristics, the high-frequency current flowing through the first capacitor is minimized. For this reason, since the loss generated by passing through the first capacitor is reduced, it is possible to prevent the deterioration of the antenna characteristics.

  Further, the antenna device according to the present invention has a fifth feature that a first inductor is provided between the first voltage dividing circuit and the second voltage dividing circuit.

  According to the antenna device having the above characteristics, by providing the first inductor, it is possible to prevent a high frequency component due to coupling with the radiating element of the antenna from flowing into the voltage supply source, and to stabilize the power supply source. Is possible.

  Further, in the antenna device according to the present invention, the first resistor has a lower resistance value than the second resistor, the third resistor has a higher resistance value than the fourth resistor, and the voltage dividing ratio is the first. The sixth feature is that the first voltage dividing circuit is larger than the second voltage dividing circuit.

  According to the antenna device having the above characteristics, by changing the ratio between the first and second resistors connected to the first switching element and the third and fourth resistors connected to the second switching element. The voltage dividing ratio of the voltage applied to each switching element can be changed. As a result, a plurality of switching elements can be controlled by a single voltage supply source.

  Furthermore, an antenna device according to the present invention includes a first high frequency cut element having one end connected to the other end of the first voltage dividing circuit and the other end connected to one end of the first switching element, and one end Is connected to the other end of the first switching element, the other end is connected to the reference potential, the second high-frequency cut element is connected, and one end is connected to the other end of the second voltage dividing circuit, A third high-frequency cut element having the other end connected to one end of the second switching element, and a fourth having one end connected to the other end of the second switching element and the other end connected to the reference potential. A seventh feature is that the high-frequency cut element is provided.

  According to the antenna device having the above characteristics, the control path for the high-frequency signal and the DC signal as the supply voltage can be separated by connecting the high-frequency cut element. As a result, attenuation of the high-frequency signal can be prevented and the switching element can be accurately controlled.

  Furthermore, an eighth feature of the first high-frequency cut element of the antenna device according to the present invention is that it is connected to a signal line below the radiating element on the power feeding side.

  According to the antenna device having the above characteristics, since the first high-frequency cut element is connected to the signal line instead of the radiating element, the DC signal for controlling the first switching element connected in the vicinity of the radiating element can be obtained. It becomes possible to use one control line. Therefore, it is possible to reduce the deterioration of the antenna characteristics due to the interference between the antenna and the conductor line.

  Furthermore, the antenna device according to the present invention has a ninth feature that the first, second, third and fourth high frequency cut elements are choke coils.

  According to the antenna device having the above characteristics, the use of the choke coil as the high frequency cut element can efficiently prevent the high frequency signal from passing. In addition, since it can be handled by a chip inductor, mounting is easy.

  Furthermore, a tenth feature of the control circuit of the antenna device according to the present invention is that it is configured as a module on a substrate.

  According to the antenna device having the above characteristics, the control circuit can be miniaturized, and thus the size of the entire antenna device can be miniaturized.

  Furthermore, a portable terminal electronic device according to the present invention has an eleventh feature that the antenna device according to any one of the above is provided in a casing.

  According to the portable terminal electronic device having the above characteristics, it is possible to provide a multiband portable terminal electronic device associated with a plurality of frequency bands.

According to the present invention, it is possible to provide an antenna device that can operate with a control circuit configured by a simple circuit and that can suppress deterioration of antenna characteristics due to interference, and a portable terminal electronic device using the antenna device. Can do.

1 is a partially cutaway perspective view showing an antenna device provided with a variable frequency antenna according to an embodiment of the present invention. It is a circuit diagram (simplified figure) which shows the structure of the antenna device which concerns on 1st Embodiment. It is a circuit diagram which shows the specific structure of the antenna apparatus which concerns on embodiment of FIG. It is explanatory drawing of operation | movement of the antenna apparatus of FIG. It is the schematic diagram showing VSWR of the antenna device which concerns on 1st Embodiment. It is a schematic diagram showing the efficiency of the antenna device according to the first embodiment. It is a schematic diagram showing the GPS peak efficiency of the antenna device according to the first embodiment. It is a simplification figure of the antenna device concerning a 2nd embodiment.

  Preferred embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are equivalent. Furthermore, the constituent elements described below can be appropriately combined. In addition, various omissions, substitutions, or changes of components can be made without departing from the scope of the present invention.

(Basic configuration of antenna device)
A variable frequency antenna 1 according to an embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. FIG. 1 is a perspective view showing a partially broken antenna device including a variable frequency antenna 1 according to an embodiment of the present invention. As shown in FIG. 1, the frequency variable antenna 1 and the control circuit 10 are provided on the mounting substrate 5 in the portable terminal electronic device 30. The mounting substrate 5 is divided into a non-ground region 6a and a ground region 6b, the frequency variable antenna 1 is formed on the non-ground region 6a, and the control circuit 10 is mounted on the ground region 6b.

  The antenna device provided with the variable frequency antenna 1 is mounted on a portable terminal electronic device such as a cellular phone, and has a function of receiving or transmitting radio waves in a plurality of frequency bands. It is called a multiband antenna (composite antenna). The application target of the antenna device including the variable frequency antenna 1 may be any wireless communication device having a plurality of wireless communication functions, and is not limited to a mobile phone.

  The variable frequency antenna 1 has a linear antenna structure with an open end, the radiating elements 2a and 2b are physically separated, and the first switching element 3a is inserted. Similarly, the radiating elements 2b and 2c are also physically separated and a second switching element 3b is inserted.

  FIG. 2 is a circuit diagram (simplified view) showing the structure of the antenna device 40a according to the first embodiment. This antenna device has a voltage supply terminal 7 for applying a control voltage to a PIN diode as a first switching element and a second switching element, one end connected to the voltage supply terminal 7 and the other end connected to the first switching element. A first voltage dividing circuit 20a connected to one end of the switching element, and a second voltage dividing circuit having one end connected to the voltage supply terminal 7 and the other end connected to one end of the second switching element. 20b.

  The first voltage dividing circuit 20a has one end connected to the voltage supply terminal 7 via the first connection node 9 and one end connected to the other end of the first resistor 8a. Thus, the second resistor 8b is connected to the reference potential 11a at the other end, and one end of the second voltage dividing circuit 20b is connected to the voltage supply terminal 7 via the first connection node 9. The third resistor 8c is connected to the other end of the third resistor 8c, and the other end is connected to the reference potential 11b.

  Further, the variable frequency antenna 1 is connected to the power feeding unit 4 through the signal line 13, and a first capacitor 12a for DC cut is provided on the second radiating element 2b after the second switching element 3b. Has been placed.

(First embodiment)
FIG. 3 is a circuit diagram showing a specific structure of the antenna device 40a according to the first embodiment. The variable frequency antenna 1 is composed of radiating elements 2 a, 2 b, and 2 c and is connected to the power feeding unit 4 via a signal line 13. Further, the control circuit 10 includes a first inductor 15 for high-frequency noise cut, one end of which is connected to the first connection node 9 and the other end is connected to one end of the third resistor 8c. . Further, the resistance value of each resistor is such that the first resistor 8a has a lower resistance value than the second resistor 8b, and the third resistor 8c has a higher resistance value than the fourth resistor 8d. For this reason, the first voltage dividing circuit 20a is larger in the voltage dividing ratio than the second voltage dividing circuit 20b.

  Further, the choke as a first high frequency cut element having one end connected to the other end of the first voltage dividing circuit 20a and the other end connected to one end of the first switching element 3a via the signal line 13. The coil 14a has a choke coil 14b as a second high-frequency cut element having one end connected to the other end of the first switching element 3a and the other end connected to a reference potential, and one end being a second A choke coil 14c as a third high-frequency cut element, the other end of which is connected to the other end of the voltage dividing circuit 20b and the other end connected to one end of the second switching element 3b, and one end of the second switching element 3b. And a choke coil 14d as a fourth high-frequency cut element, the other end of which is connected to the reference potential.

  Furthermore, the choke coil 14a is connected to the signal line 13 in order to separate the DC signal control line from the antenna radiating element, thereby preventing deterioration of the antenna characteristics. The choke coils 14a, 14b, 14c, and 14d play a role of preventing the passage of high-frequency signals without affecting the DC signal. In this embodiment, the choke coil is used as the first, second, third and fourth high frequency cut elements. However, the same effect can be obtained by using a resistance element instead of the choke coil.

  Furthermore, a voltage supply source 16 that controls ON / OFF of the first and second switching elements 3 a and 3 b is connected via a first connection node 9. The first inductor 15 is for cutting high-frequency noise, and the first capacitor 12a is for cutting a DC voltage from the voltage supply source 16 to prevent a malfunction of the switching element. The first capacitor 12a is disposed after the second switching element in order to prevent deterioration of antenna characteristics. Further, by adjusting the resistance value constituting the voltage dividing circuits 20a and 20b, the voltage dividing ratio of the first voltage dividing circuit 20a is larger than that of the second voltage dividing circuit 20b. With these structures, it is possible to arbitrarily select a matching element even when a voltage is simultaneously supplied to a PIN diode as two switching elements from a single voltage supply source. As a result, the control circuit can be simplified, reduced in size, cost, and circuit loss can be reduced.

FIG. 4 shows a specific operation of the antenna device 40a according to the first embodiment. When the control voltage is zero, the first and second switching elements 3a and 3b are turned off. Next, by gradually increasing the control voltage, the first and second switching elements 3a and 3b are continuously turned on. That is, when the voltage is low, the switching element 3a is turned on. When the voltage is continuously increased, both the first and second switching elements 3a and 3b are turned on. The radiation element length in each state is 2a at zero voltage, 2a + 2b at low voltage, and 2a + 2b + 2c at high voltage.

  FIG. 5 is a schematic diagram showing changes in the VSWR (voltage standing wave ratio) characteristics of the antenna device of FIG. In this figure, the vertical axis represents VSWR and the horizontal axis represents frequency.

  FIG. 6 is a schematic diagram showing changes in the efficiency characteristics of the antenna device of FIG. In this figure, the vertical axis represents radiation efficiency and the horizontal axis represents frequency.

  The display of the state S1, the state S2, and the state S3 shown in the graphs of FIGS. 5 and 6 indicates the ON / OFF state of the PIN diode as the first and second switching elements 3a and 3b. As can be seen from these figures, the change of the radiation element length due to the three states of the first and second switching elements 3a and 3b causes the GPS frequency band (1.575 GHz), the Bluetooth frequency band (2.44 GHz) and the W-LAN. The resonance frequency of the frequency 3 state of the frequency band (5 GHz) is realized. The frequency changes in FIGS. 5 and 6 show an example, and are adjusted according to the actual arrangement of the antenna configuration and the mobile terminal electronic device 30.

  For example, the resistance value of this example is the first resistance 8a = 100Ω, the second resistance 8b = 200Ω, the third resistance 8c = 200Ω, the fourth resistance 8d = 100Ω, and the supply voltage is the standard forward voltage. Therefore, the low voltage value is 1.2V and the high voltage value is 2.4V. In this case, the first resistor 8a has a lower resistance value than the second resistor 8b, and the third resistor 8c has a higher resistance value than the fourth resistor 8d. Therefore, the voltage dividing ratio is higher in the first voltage dividing circuit 20a (ratio 0.67) than in the second voltage dividing circuit 20b (ratio 0.33). When the low voltage is supplied, the first switching element 3a is turned on and the second switching element 3b is turned off.

  The variable frequency antenna 1 is composed of three radiating elements 2a, 2b, and 2c, and can realize three types of resonance frequencies by connecting or blocking each radiating element with a switching element. For example, the length of the radiating element of this example is the first radiating element 2a = 11.8 mm, the second radiating element 2b = 15.5 mm, and the third radiating element 2c = 10.5 mm. That is, in the W-LAN frequency band (5 GHz) (state S1), the first radiating element 2a (2a = 11.8 mm) is used as an antenna element, and in the Bluetooth frequency band (2.44 GHz) (state S2), the first The total length (2a + 2b = 27.3 mm) of the radiating element 2a and the second radiating element 2b is used as an antenna element. In the GPS frequency band (1.575 GHz) (state S3), the first radiating element 2a and the second radiating element 2b The total length (2a + 2b + 2c = 37.8 mm) of the two radiating elements 2b and the third radiating element 2c is used as the antenna element. Since the length of these radiating elements is affected by the antenna structure, the distance between GNDs, the material of the housing, etc., when mounted on an actual portable wireless device, the length should be adjusted to the characteristics of each resonance frequency. It needs to be adjusted.

  FIG. 7 is a schematic diagram showing changes in the GPS peak efficiency characteristics of the antenna device of FIG. In this figure, the vertical axis represents the peak value of the radiation efficiency of the GPS antenna, and the horizontal axis represents the distance between the first capacitor 12a and the first switching element 3a. In a monopole type linear antenna, a large amount of high-frequency current flows at the base of the radiating element. Therefore, the first capacitor 12a having a resistance component can be prevented from deteriorating the antenna characteristics when arranged at the tip of the radiating element. . Since the first capacitor 12a is disposed between the first switching element 3a and the second switching element 3b, the first capacitor 12a is disposed in the vicinity of the second switching element that is farthest from the first switching element 3a. Can prevent deterioration of antenna characteristics.

  The antenna device of the present embodiment configures two voltage dividing circuits as control circuits for controlling the switching elements. For this reason, it is possible to realize three resonance frequencies by gradually increasing the applied voltage from one supply voltage source. According to this structure, it is not necessary to perform a complicated operation for controlling each switching element, and an advanced control circuit is not necessary. As a result, it is possible to reduce the number of components, reduce the size of the circuit, and reduce the cost.

(Second Embodiment)
FIG. 8 shows a simplified diagram of an antenna device 40b according to the second embodiment. A difference from the antenna device 40a according to the first embodiment shown in FIG. 2 is that a switching element and a voltage dividing circuit are configured in three stages. In the first embodiment, three resonance frequencies can be realized by a two-stage switching element, but by adding a third switching element 3c and a third voltage dividing circuit 20c, four resonance frequencies can be obtained. It can be realized. At this time, all switching elements are turned off at a voltage of zero, the first switching element 3a is turned on at a low voltage, the first and second switching elements 3a and 3b are turned on at a medium voltage, and the first switching element 3a and 3b are turned on at a high voltage. The first, second and third switching elements 3a, 3b and 3c are turned on. Further, the voltage dividing ratio is a relationship of the first voltage dividing circuit 20a, the second voltage dividing circuit 20b, and the third voltage dividing circuit 20c in order of the high ratio.

  The present invention is effective for a composite antenna that realizes a large number of frequencies such as a main antenna or an application other than voice (for example, GPS, Bluetooth (registered trademark), W-LAN) mounted on a portable wireless device.

  Further, the control circuit of the present invention can be configured as a module on a substrate, or can be configured in one chip by a thin film structure. By configuring in a module or one chip, it becomes possible to reduce the height and size, and to reduce the line loss.

  The preferred embodiments of the present invention have been described above. However, it is possible to change the embodiments other than those described above.

  As described above, the antenna device according to the present invention has a structure capable of adjusting the resonance frequency of the antenna over a wide band using a simple control circuit. Since this antenna device can realize an antenna that can handle a plurality of applications, the antenna can be miniaturized, the number of components can be reduced, and the added value of the antenna can be greatly improved.

DESCRIPTION OF SYMBOLS 1 Frequency variable antenna 2a 1st radiation element, 2b 2nd radiation element 2c 3rd radiation element 3a 1st switching element, 3b 2nd switching element 3c 3rd switching element 4 Feeding part 5 Mounting board 6a Non-ground region, 6b Ground region 7 Voltage supply terminal 8a 1st resistor, 8b 2nd resistor, 8c 3rd resistor, 8d 4th resistor 8e 5th resistor, 8f 6th resistor 9 1st connection Node 10 Control circuit 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h, 11i Reference potential (GND)
12a First capacitor, 12b Second capacitor 13 Signal line 14a First high frequency cut element, 14b Second high frequency cut element 14c Third high frequency cut element, 14d Fourth high frequency cut element 15 First inductor 16 Voltage supply source 17a First current limiting resistor, 17b Second current limiting resistor 18 Electrostatic countermeasure capacitor 20a First voltage dividing circuit, 20b Second voltage dividing circuit, 20c Third voltage dividing circuit 30 Mobile phone Terminal electronics 40a Antenna device of the first embodiment, 40b Antenna device of the second embodiment

Claims (11)

An antenna device comprising: an open-ended linear radiating element in which a plurality of parts are physically separated; and a plurality of switching elements that electrically connect or disconnect the separated part;
A first switching element on the power feeding side on the radiation element and a second switching element on the tip side;
A first capacitor is inserted on a radiating element between the first switching element and the second switching element;
A voltage supply terminal for applying a control voltage to the first switching element and the second switching element;
A first voltage dividing circuit having one end connected to the voltage supply terminal and the other end connected to one end of the first switching element;
An antenna apparatus comprising: a control circuit including a second voltage dividing circuit having one end connected to the voltage supply terminal and the other end connected to one end of the second switching element.   The antenna device according to claim 1, wherein the switching element is a PIN diode. As the first voltage dividing circuit, one end is connected to the voltage supply terminal, one end is connected to the other end of the first resistor, and the other end is connected to a reference potential. A second resistor comprising:
As the second voltage dividing circuit, one end is connected to the voltage supply terminal, one end is connected to the other end of the third resistor, and the other end is connected to a reference potential. The antenna device according to claim 1, wherein the antenna device comprises a fourth resistor.   The antenna device according to claim 1, wherein the insertion position of the first capacitor on the radiating element is a stage subsequent to the second switching element.   The antenna device according to claim 1, further comprising a first inductor between the first voltage dividing circuit and the second voltage dividing circuit.   The first resistor has a lower resistance value than the second resistor, the third resistor has a higher resistance value than the fourth resistor, and a voltage dividing ratio is higher than that of the second voltage dividing circuit. The antenna device according to claim 3, wherein the first voltage dividing circuit is larger. A first high-frequency cut element having one end connected to the other end of the first voltage dividing circuit and the other end connected to one end of the first switching element; and one end of the first switching element A second high-frequency cut element connected to the other end and connected to the reference potential at the other end;
A third high-frequency cut element having one end connected to the other end of the second voltage dividing circuit and the other end connected to one end of the second switching element; and one end of the second switching element The antenna device according to claim 1, further comprising a fourth high-frequency cut element connected to the other end and connected to the reference potential at the other end.   The antenna device according to claim 7, wherein the first high-frequency cut element is connected to a signal line under a radiating element on a power feeding side.   9. The antenna device according to claim 7, wherein the first, second, third and fourth high frequency cut elements are choke coils.   The antenna device according to claim 1, wherein the control circuit is configured as a module on a substrate.   A portable terminal electronic device comprising the antenna device in a housing.

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