JP2010045573A - Antenna apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna apparatus having a high radiation gain and a simple structure. <P>SOLUTION: An antenna apparatus includes: a low-frequency antenna element 2 having a predetermined electrical length; a high-frequency antenna element 4 having an electrical length shorter than that of the low-frequency antenna element 2 and in which a PIN diode 3 is inserted in series; a radiation signal power feeding source 6 that supplies a radiation signal RF to a parallel antenna circuit 5 in which the high-frequency antenna element 4 and the low-frequency antenna element are connected in parallel; a direct current source 7 that applies the direct current signal by superposing a direct current signal to the radiation signal RF; and a switching controller 8 that superposes the direct current signal to cause the PIN diode 3 to conduct when desired that a high-frequency radiation signal RFH is radiated, and does not superpose the direct current to disconnect the PIN diode 3 when desired that a low-frequency radiation signal RFL is radiated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an antenna device having a high radiation gain and a simple configuration.

  An antenna device built in a mobile phone that receives terrestrial digital broadcasts is compatible with a wide frequency band of terrestrial digital broadcasts while being small. FIG. 3 is known as an antenna device used in such a wide band.

  As shown in FIG. 3, the conventional antenna device 31 includes an antenna element 32 that can be switched between a low band and a high band, and a switch 33 that switches a feeding point to the antenna element. Inductor 34 and a large number of variable capacitance elements 35 are alternately connected in series.

  When the antenna element 32 is switched to the low band, the antenna element 32 has a long electrical length and is suitable for reception in a low frequency band (low band). When the antenna element 32 is switched to the high band, the antenna element 32 has a short electrical length and is high. Suitable for reception of frequency band (high band). Switching of the feeding point can be performed by the switch 33.

  Further, by controlling the capacitance of the variable capacitance element 35, the resonance frequency of the antenna element 32 can be finely adjusted and tuned to the frequency of the received radio wave. Since the capacitance of the variable capacitor 35 depends on the applied voltage, it can be easily controlled by a circuit in the mobile phone.

JP 2008-5312 A

  In the prior art, a large number of variable capacitance elements 35 are distributed in series on the antenna element 32. Since the variable capacitance element 35 is not a pure capacitance element but is composed of a semiconductor, it has a series resistance component. Since there are a large number of variable capacitance elements 35 in series, the antenna element 32 has a large series resistance component. For this reason, the radiation gain of the antenna device 31 decreases.

  Further, in the prior art, a tuning control voltage is supplied to each of a large number of variable capacitance elements 35, so that a large number of resistance elements for supplying a control voltage to the variable capacitance elements 35 are required. This leads to complication and cost increase of the antenna device 31.

  In the prior art, an inductor 36 for a matching circuit is inserted in series with the antenna element 32. The inductor 36 has a resistance component. For this reason, the radiation gain of the antenna device 31 decreases.

  Further, in the prior art, since a large number of variable capacitance elements 35 and a large number of inductors 34 are mounted, the number of parts is large, the antenna device 31 is complicated, and the cost is high. In the prior art, since the switch 33 is used to switch the feeding point, the number of parts is large, and the space for arranging the switch 33 is required separately from the space for arranging the antenna element 32. Prevent miniaturization.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an antenna device having a high radiation gain and a simple configuration.

  In order to achieve the above object, the present invention provides a low band antenna element formed of a conductor having a predetermined electrical length, and a switch inserted in series in a conductor having a shorter electrical length than the low band antenna element. The formed high-frequency antenna element, a radiating signal power supply for supplying a radiating signal to a parallel antenna circuit in which the high-frequency antenna element and the low-frequency antenna element are connected in parallel, and the radiating signal If you want to radiate a high-frequency radiation signal and a DC power supply that can apply a direct-current signal, the switch is turned on by superimposing the direct-current signal on the radiation signal, and a low-frequency radiation signal is When it is desired to radiate, a switching control unit is provided that shuts off the switch by not superimposing the DC signal on the radiation signal.

  A variable capacitance element inserted between the parallel antenna circuit and the ground, and a radiation frequency adjustment unit that adjusts the radiation frequency of the high-frequency antenna element or the low-frequency antenna element by controlling the variable capacitance element And may be provided.

  The high band antenna element may be provided closer to the ground than the low band antenna element.

  The present invention exhibits the following excellent effects.

  (1) Radiation gain is high.

  (2) The configuration is simple.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, an antenna device 1 according to the present invention includes a low band antenna element 2 formed of a conductor having a predetermined electrical length, and a conductor having a shorter electrical length than the low band antenna element 2. Radiating signals to a high-frequency antenna element 4 formed by inserting a PIN diode 3 in series into a parallel antenna circuit 5 in which the high-frequency antenna element 4 and the low-frequency antenna element 2 are connected in parallel. A radiating signal power supply 6 that feeds RF, a DC power source 7 that can apply a DC signal DCSWcont superimposed on the radiating signal RF, and a DC signal to the radiating signal RFH when radiating a high frequency radiating signal RFH. When the PIN diode 3 is made conductive by superimposing the signal DCSWcont and the low-frequency emission signal RFL is to be emitted, the direct current signal DCSWc is added to the emission signal RFL. By not superimposing the nt is obtained and a switching control unit 8 to cut off the PIN diode 3.

  The PIN diode 3 is a switch. In addition to a PIN diode, a MEMS switch can be used as the switch.

  Further, the DC power source 7 is connected to the parallel antenna circuit 5 via the inductor 21. The inductor 21 cuts off the radiation signal RF from the radiation signal power supply 6, and the DC signal DCSWcont is applied from the DC power supply 7 to the parallel antenna circuit 5.

  Thus, in the antenna device 1 of the present invention, the electrical length of the conductor constituting the low-frequency antenna element 2 is longer than the electrical length of the conductor constituting the high-frequency antenna element 4, and the high-frequency antenna element 4 includes A PIN diode 3 is inserted in series. The direct current signal DCSWcont is superimposed when the high-frequency radiation signal RFH is emitted, and the direct-current signal DCSWcont is not superimposed when the low-frequency radiation signal RFL is emitted.

  The radiation signal RF fed from the radiation signal power supply 6 to the parallel antenna circuit 5 is the high-frequency radiation signal RFH or the low-frequency radiation signal RFL. The DC signal DCSWcont applied by the DC power source 7 applies a predetermined voltage in the forward direction of the PIN diode 3 to make it conductive. For example, when a PIN diode that conducts at 0.7 V or higher is used as the PIN diode 3, 0.7 V is applied to make it conductive, and when it is 0 V (no voltage is applied), it is turned off.

  The wavelength of the radiation signal RFL radiated from the low band antenna element 2 is longer than the wavelength of the radiation signal RFH radiated from the high band antenna element 4. Therefore, if the low-frequency antenna element 2 is disposed closer to the ground 20 than the high-frequency antenna element 4 as shown in FIG. 4, it is difficult to radiate the radiation signal RFL. Therefore, as shown in FIG. 1, the high-frequency antenna element 4 is arranged closer to the ground 20 than the low-frequency antenna element 2 so that the radiation signal RFL is easily radiated.

  The low-frequency antenna element 2 includes two conductor pieces 9 and 9 formed in a straight line and having a length that divides a predetermined electric length into two, and a DC blocking capacitor 10 inserted in the middle thereof. The high-frequency antenna element 4 includes two conductor pieces 11 and 11 that are formed in a length that bisects an electrical length shorter than that of the low-frequency antenna element 2 and a PIN diode 3 that is inserted between them. With.

  A matching element 12 is connected to the radiation signal feeding end of the parallel antenna circuit 5. The matching element 12 is connected to the ground via a matching element capacitor 13 in series. The matching capacitor 13 blocks the DC signal DCSWcont applied from the DC power supply 7 and does not flow to the ground. It is for doing so.

  The conductor piece 11 located on the cathode side of the PIN diode 3 among the two conductor pieces 11 and 11 constituting the high-frequency antenna element 4 is connected to an inductor 14 that cuts off the radiation signal RF and is grounded in a DC manner. Connected to ground.

  The antenna device 1 according to the present invention includes a variable capacitive element 15 inserted between the parallel antenna circuit 5 and the ground, and the variable capacitive element 15 to control the high band antenna element 4 or the low band element. And a radiation frequency adjusting unit 16 that adjusts the radiation frequency of the antenna element 2.

  A DC blocking capacitor 17 is provided between the parallel antenna circuit 5 and the variable capacitance element 15. Further, a resistor 18 for blocking the radiation signal RF is provided between the radiation frequency adjusting unit 16 and the variable capacitance element 15. As a result, the capacitance of the variable capacitance element 15 changes according to the DC voltage applied to the variable capacitance element 15 by the radiation frequency adjusting unit 16, and the radiation frequency of the parallel antenna circuit 5 changes.

  Hereinafter, the operation of the antenna device of the present invention will be described.

  First, the operation of radiating the high-frequency radiation signal RFH will be described. The radiation signal power supply 6 supplies the parallel antenna circuit 5 with the high-frequency radiation signal RFH. At this time, the switching control unit 8 controls the DC power source 7 to superimpose the DC signal DCSWcont on the high-frequency radiation signal RFH. Therefore, a signal in which the DC signal DCSWcont is superimposed on the high-frequency radiation signal RFH is applied to the parallel antenna circuit 5.

  In the high band antenna element 4, the conductor piece 11 located on the cathode side of the PIN diode 3 is connected to the ground via the inductor 14, so that the DC signal DCSWcont is applied to the PIN diode 3. PIN diode 3 becomes conductive. When the PIN diode 3 is turned on, the high-frequency antenna element 4 is fed with the high-frequency radiation signal RFH. In the high-frequency antenna element 4, the high-frequency radiation signal RFH resonates and radiation is generated. On the other hand, the low-frequency antenna element 2 is also fed with a signal in which the direct-current signal DCSWcont is superimposed on the high-frequency radiation signal RFH, but the direct-current signal DCSWcont is blocked by the direct-current blocking capacitor 10 and In the antenna element 2, the high frequency signal RFH does not resonate and no radiation is generated.

  Next, the operation of radiating the low-frequency radiation signal RFL will be described. The radiation signal power supply 6 feeds the parallel antenna circuit 5 with the low-frequency radiation signal RFL. At this time, the switching control unit 8 controls the DC power supply 7 so that the DC signal DCSWcont is not superimposed on the low-frequency emission signal RFL. Therefore, only the low-frequency radiation signal RFL is applied to the parallel antenna circuit 5.

  Only the low-frequency radiation signal RFL is fed to the low-frequency antenna element 2. In the low-frequency antenna element 2, the low-frequency radiation signal RFL resonates and radiation is generated. On the other hand, in the high band antenna element 4, since the DC signal DCSWcont is not applied to the PIN diode 3, the PIN diode 3 is cut off (non-conductive state). Since the PIN diode 3 is cut off, the low-frequency radiation signal RFL is not fed to the high-frequency antenna element 4, and resonance and radiation do not occur.

  As described above, in the antenna device 1, the PIN diode 3 functions as a low-band and high-band changeover switch, and the control voltage of the changeover switch is superimposed on the RF signal. If the change-over switch is on, high-band radiation is performed, and if the switch is off, low-band radiation is performed. Thereby, the antenna device 1 functions as a two-band antenna. Compared with the antenna device 31 of FIG. 3, the switch 33 for switching the feeding point is unnecessary, so the number of parts is reduced and the space is saved.

  Next, the adjustment (tuning) of the radiating frequency will be described. The radiating frequency adjusting unit 16 adjusts the DC voltage applied to the variable capacitance element 15 to change the capacitance of the variable capacitance element 15 to change the parallel antenna circuit. 5 radiation frequency is controlled. The tuning voltage applied by the radiation frequency adjusting unit 16 is, for example, 0 to 3V.

  As described above, in the parallel antenna circuit 5, the high-frequency antenna element 4 is fed with the high-frequency radiation signal RFH, and the low-frequency antenna element 2 is fed with the low-frequency radiation signal RFL. There is a state. In any state, the radiation frequency of the high-frequency antenna element 4 or the low-frequency antenna element 2 is controlled according to the capacitance change of the variable capacitance element 15. Therefore, the radiation frequency of the high-frequency antenna element 4 or the low-frequency antenna element 2 is adjusted, and tuning to a desired radiation frequency is achieved.

  As described above, in the antenna device 1, the high frequency antenna element 4 and the low frequency antenna element 2 are the same, and the radiation frequency is controlled by the only variable capacitance element 15. Compared with the antenna device 31 of FIG. 3, the high-frequency antenna element 4 and the low-frequency antenna element 2 have only one variable capacitance element 15, so that the series resistance component does not increase. For this reason, the radiation gain of the antenna apparatus 1 becomes high. In addition, since there is only one resistor 18 that adjusts the tuning control voltage, the antenna device 1 is simplified and the cost can be reduced.

  Next, matching will be described. In the antenna device 1, the matching element 12 is connected to the radiation signal feeding end of the parallel antenna circuit 5.

  Since the impedance of the radiation signal feed line 6 is 50Ω, the input impedance of the antenna device 1 is also 50Ω. This is because if the input impedance of the antenna device 1 is not 50Ω, the reception sensitivity of the antenna is deteriorated. Note that the input impedance can be adjusted by the length of the matching element 12 that is an inductor. As the length of the matching element 12 increases, the input impedance of the antenna also increases.

  A specific operation example of the antenna device 1 of the present invention will be described with reference to FIG.

  A characteristic A1 indicated by a solid line is a VSWR characteristic in a low band. At this time, the frequency peak is about 470 MHz. By tuning, the frequency peak can be continuously increased. The frequency peak of the characteristic A2 indicated by the broken line is about 550 MHz. The VSWR characteristic can be arbitrarily adjusted continuously in the range from the characteristic A1 to the characteristic A2.

  A characteristic B1 indicated by a solid line is a VSWR characteristic in a high band. At this time, the frequency peak is about 580 MHz. By tuning, the frequency peak can be continuously increased. The frequency peak of the characteristic B2 indicated by the broken line is about 720 MHz. The VSWR characteristic can be arbitrarily adjusted continuously in the range from the characteristic B1 to the characteristic B2.

  By combining low-band and high-band switching and tuning, a wide band (characteristic A1 to characteristic B2) of about 470 MHz to about 720 MHz can be handled. Therefore, the antenna device 1 of the present invention is suitable for receiving broadcast radio waves in the UHF band used for terrestrial digital broadcasting and the like.

  In the above embodiment, a DC blocking capacitor 10 is disposed between the conductor pieces 9 and 9 constituting the low-frequency antenna element 2, and between the conductor pieces 11 and 11 constituting the high-frequency antenna element 4. However, the present invention is not limited to this.

  As shown in FIG. 5A, the left side of the conductor piece 41 constituting the low-frequency antenna element 2 (radiation signal power supply 6 side) and the right side of the conductor piece 41 as shown in FIG. The DC blocking capacitor 10 may be disposed on the (radiation frequency adjusting unit 16 side). In addition, the conductor piece 41 is corresponded to the thing which put together the conductor pieces 9 and 9 shown in FIG.

  Further, as shown in FIG. 6A, a PIN diode is placed on the left side (radiation signal power supply 6 side) of the conductor piece 51 and on the right side (radiation frequency adjustment unit 16 side) as shown in FIG. 6B. 3 may be arranged. In addition, the conductor piece 51 is corresponded to the thing which put together the conductor pieces 11 and 11 shown in FIG.

  Furthermore, the antenna device 1 may be configured by combining the insertion positions of the elements shown in FIGS. 1, 5, and 6.

  However, as shown in FIG. 7, a PIN diode 3 is connected in series to the low-frequency antenna element 2 and a DC blocking capacitor 10 is connected to the high-frequency antenna element 4 so that the DC signal DCSWcont is generated during low-frequency operation. It is not preferable to superimpose on the radiation signal RFL. Since the low band has a lower gain than the high band, it is better that there is no resistance as much as possible. Therefore, the antenna device of FIG. 7 in which the PIN diode 3 is turned on during low frequency operation and a series resistance is generated is not preferable.

It is a circuit diagram of an antenna device showing one embodiment of the present invention. It is a frequency vs. VSWR characteristic view of the antenna device of the present invention. It is a circuit diagram of the conventional antenna device. It is a circuit diagram of an antenna device showing one embodiment of the present invention. (A), (b) is a partial circuit diagram which shows the modification of the low frequency band antenna element. (A), (b) is a partial circuit diagram which shows the modification of the antenna element for high regions. It is a circuit diagram of an antenna device as a reference example.

Explanation of symbols

1 Antenna device 2 Low band antenna element 3 PIN diode (switch)
4 High-frequency antenna element 5 Parallel antenna circuit 6 Radiation signal power supply 7 DC power supply 8 Switching control unit 12 Matching element 15 Variable capacitance element 16 Radiation frequency adjustment unit

Claims (3)

  A low-frequency antenna element formed of a conductor having a predetermined electrical length; a high-frequency antenna element formed by inserting a switch in series in a conductor having a shorter electrical length than the low-frequency antenna element; and A radiating signal power supply that feeds a radiating signal to a parallel antenna circuit in which a high-frequency antenna element and the low-frequency antenna element are connected in parallel, and a direct current that can be applied to a dc signal superimposed on the radiating signal When it is desired to radiate a power source and a high-frequency radiation signal, the DC signal is superimposed on the radiation signal to make the switch conductive. When a low-frequency radiation signal is desired to be radiated, the direct current signal is applied to the radiation signal. An antenna device comprising: a switching control unit that shuts off the switch by not overlapping the switch.   A variable capacitance element inserted between the parallel antenna circuit and the ground, and a radiation frequency adjustment unit that adjusts the radiation frequency of the high-frequency antenna element or the low-frequency antenna element by controlling the variable capacitance element The antenna device according to claim 1, further comprising:   3. The antenna device according to claim 2, wherein the high band antenna element is provided closer to the ground side than the low band antenna element.

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