JP5003628B2 - Tunable antenna and receiving device equipped with tunable antenna - Google Patents

Description

The present invention relates to a tunable antenna for use in a portable wireless terminal such as a mobile phone, a personal computer, a PDA (Personal Digital Assistants), and a game machine, and a receiver equipped with the tunable antenna.

  It has been proposed to use a monopole antenna as a prior art antenna that is applied to a radio system that receives a radio wave having a frequency lower than that of a mobile phone, such as terrestrial analog broadcasting and terrestrial digital broadcasting (for example, Patent Document 1).

  Such an antenna has a wide band and can correspond to the entire frequency band used by the system, but the wavelength of the radio wave to be received by this antenna is, for example, 64 cm in the case of Japanese terrestrial digital television broadcasting, Therefore, there is a problem that it is difficult to incorporate it into a portable wireless terminal such as a current cellular phone, PDA, or receiver having a size of about 20 cm.

  Currently, mobile wireless terminals are becoming more sophisticated. For example, in mobile phones, it is conceivable that reception functions such as television broadcasting and radio broadcasting will be combined in the future in addition to telephone functions. Each of these broadcasting systems is assigned a different frequency band, and uses a channel obtained by frequency-dividing these bands. For example, UHF groups of 470 MHz to 770 MHz are allocated to Japanese terrestrial digital television broadcasting, and 13 to 62 channels are given at 6 MHz intervals within this band. In order to view a television broadcast, the viewer selects a desired channel.

  When all the wide frequency bands used by each wireless system are received by one antenna, unnecessary radio waves are input as interference waves to the received waves. From the viewpoint of interference wave suppression, it is desirable to receive only a necessary band in a narrow band. Therefore, in order to prevent the reception of signals from other wireless systems that would interfere with the television system, unnecessary frequency channels other than the desired frequency channel are removed by a tracking filter circuit provided after the antenna. There is also a mechanism that is provided.

On the other hand, since portable wireless terminals are required to be downsized from the viewpoint of improving portability, downsizing of each antenna is also required. In such a background, a receiving terminal using a so-called tunable antenna is proposed in which the center frequency of impedance matching of a tuning antenna is controlled in accordance with the receiving frequency (for example, Patent Document 2). reference).
The tuning circuit of the tunable antenna incorporates a variable capacitance diode as variable capacitance means. The center frequency of impedance matching of the antenna can be changed by controlling the voltage applied to the variable capacitance diode from the outside of the antenna. The center frequency (resonance frequency) of impedance matching is roughly determined by the inductance value (L) of the antenna receiving element portion and the capacitance value (C) of the variable capacitance means, and the receivable frequency range is that of the variable capacitance means. It depends on the capacity change ratio. The antenna gain of the tunable antenna depends on the size of the receiving element, that is, its inductance value (L). In order to increase the antenna gain, it is necessary to increase the inductance value of the receiving element.

  FIG. 9 shows a conventional example of a receiving apparatus provided with a tunable antenna. The tunable antenna is mainly composed of a wave receiving element 11, variable capacitance means 21 electrically connected to the wave receiving element 11, and a high-frequency signal feeding unit 3 including a high-frequency signal output terminal 31. These components are provided on the printed wiring board 1.

In order to house the tunable antenna in a housing and use it as a built-in antenna, the printed wiring board 1 is mounted on the receiver main body substrate 10 and a high frequency signal output terminal of the tunable antenna provided on the receiver main body substrate The tuner circuit 101 is electrically connected to 31 and the control circuit 103 is electrically connected to the variable capacitance means 21 to control the resonance frequency from the outside of the antenna. In order to receive 470 to 770 MHz of the entire UHF band allocated to terrestrial digital television broadcasting, it is necessary to greatly change the capacitance value of the variable capacitance means 21 provided in the tunable antenna.
On the other hand, in order to obtain sufficient sensitivity, it is necessary to enlarge the receiving element to some extent. When the length of the receiving element is about 40 mm, which is a size that can be accommodated in a mobile phone, the capacitance change of the variable capacitance diode as the variable capacitance means needs to change from about 1 pF to about 4.5 pF. In the current variable capacitance diode, an applied voltage of about 6 V is required to set the capacitance value to 1 pF. Further, in order to make the capacitance value up to 4.5 pF, the applied voltage needs to be lowered to 0V.
FIG. 10 shows the characteristics of a conventional tunable antenna. The solid line characteristics indicate the case where the control voltage of the variable capacitance diode is 0.0V. At this time, the VSWR (standing wave ratio) is low in the band 111 in which the wave receiving element 11 is receivable, indicating that the antenna is receivable on this channel. On the other hand, the broken line characteristic indicates the characteristic when the control voltage is 6.0 V, and the VSWR is low in the band 112 where the wave receiving element 11 can be received. That is, the conventional tunable antenna requires a control voltage of about 0 to 6 V in order to cover the entire band of 470 to 770 MHz as shown in FIG.

  In addition to terrestrial digital broadcasting, analog broadcasting is currently broadcast using the VHF band. In order to receive the analog broadcast VHF band, an antenna including a receiving element and a tuning circuit dedicated to reception of the VHF band has been proposed (for example, see Patent Document 3).

  Patent Document 3 describes a tuning antenna in which two sets of an antenna coil, a conductor (wire) wound around the antenna coil, and a tuning circuit 2 are prepared. This is a VHF in two or more separate bands. -F / VHF-F / UHF is received by each antenna core.

In the invention described in Patent Document 3, the first output terminal and the second output terminal are connected to form one output terminal in order to receive the separated bands by each antenna core. The two tuned antennas are separated into the lower frequency band and the higher frequency band, respectively, so that sufficient isolation can be obtained between them, so that they do not interfere with each other. ing. As a result, the number of output terminals can be reduced to one, the size can be reduced, and handling is facilitated.
JP 2001-251131 A JP 2003-298341 A JP 2003-142928 A

  In a general mobile phone device, a lithium ion battery is used, and a voltage of 0 to 3 V can be easily applied, but a voltage higher than that cannot be applied. Even if a voltage of 3 V or higher is applied using a booster circuit, the occupied portion of the circuit becomes an obstacle to downsizing of the apparatus. In addition, there is a problem that the booster circuit becomes an obstacle to lowering power consumption and a problem that the reception sensitivity is deteriorated due to noise generated from the booster circuit.

For the above reasons, when using a tunable antenna in a portable wireless terminal such as a cellular phone, it is desirable to control with an applied voltage of about 0 to 3V. However, at present, in order to make the tunable antenna controllable from 0 to 3.0 V and to be able to receive up to 470 to 770 MHz, it is necessary to reduce the receiving element to receive this band and reduce its inductance value. There is no way. As a result, there is a problem that the antenna gain is reduced and sufficient reception sensitivity cannot be obtained.

  In the invention described in Patent Document 3, since two or more separated bands are received by each antenna core, the reception is performed in the lower frequency band and the higher frequency band. In this case, sufficient isolation can be obtained between them, and they do not interfere with each other, so that one output terminal can be provided and miniaturization can be achieved. However, when two continuous tuning circuits (UHF) are to be received by two tuning circuits, sufficient isolation cannot be obtained between the lower frequency band and the higher frequency band. However, there is a problem that the output terminal cannot be made one.

  An object of the present invention is to provide a tunable antenna capable of obtaining a sufficient reception sensitivity and outputting a high-frequency signal at one output terminal even when one continuous band is received by two antennas. And providing a receiving apparatus including the same.

According to the first aspect of the present invention, in a tunable antenna that receives a high-frequency signal in one continuous frequency band, a first receiving element made of a metal conductor and one end of the first receiving element A first tuning circuit having a first variable capacitance means electrically connected, and receiving a high frequency signal on a low frequency band side of the frequency band; a second receiving element made of a metal conductor; A second tuning circuit electrically connected to one end of the second receiving element, and receiving a high-frequency signal on the high- frequency band side of the frequency band; and The first and second receiving elements are electrically connected to the other end of the first receiving element of the first tuning circuit and the other end of the second receiving element of the second tuning circuit. A high-frequency signal power supply unit for supplying power to the wave element, and electrically connected to the high-frequency signal power supply unit Comprises a high frequency signal output terminal for outputting the high-frequency signals received respectively by said first and second tuning circuits, and a ground terminal that is grounded together with the the high-frequency signal feed electrically connected to the second The tuning frequency of the first tuning circuit is larger than the receiving frequency band of the first tuning circuit, the length of the first receiving element is longer than the length of the second receiving element, and the first variable A tunable antenna is provided in which the capacity change ratio of the capacity means is smaller than the capacity change ratio of the second variable capacity means .
Since high frequency signals in one continuous frequency band are received by the two tuning circuits, sufficient reception sensitivity can be obtained. In addition, since the ground terminal is provided in the high-frequency signal feeder, the high-frequency signals received by the first and second tuning circuits can be output and received from one high-frequency signal output terminal without interfering with each other. it can.

Further, when the reception frequency band of the second tuning circuit is larger than the reception frequency band of the first tuning circuit, the upper limit of the frequency change received by the first tuning circuit can be set low, and the first receiving element The length can be increased and the capacity change ratio of the first variable capacity means can be reduced. Accordingly, if the length of the first receiving element is made longer than the length of the second receiving element and the capacitance change ratio of the first variable capacitance means is made smaller than the capacitance change ratio of the second variable capacitance means, the resistance Since the component becomes small, the gain of the frequency band received by the first tuning circuit can be improved.

The upper limit value of the reception frequency that can be controlled by the first wave receiving element and the first variable capacitance means is the lower limit value of the reception frequency that can be controlled by the second wave receiving element and the second variable capacitance means. Higher is preferred.
The upper limit value of the reception frequency that can be controlled by the first wave receiving element and the first variable capacitance means is higher than the upper limit value of the reception frequency that can be controlled by the second wave receiving element and the second variable capacitance means. Then, the gain of the first tuning circuit is improved and the gain of the second tuning circuit is deteriorated. However, since the antenna gain is originally higher as the frequency is higher, the antenna gain can be leveled.

  According to the second aspect of the present invention, the tunable antenna according to the first aspect, the tuner circuit electrically connected to the high-frequency signal output terminal, and the first and second variable capacitance means are provided. There is provided a receiving device including a tunable antenna having a control circuit for applying a common control voltage to control the first and second variable capacitance means. Since the ground terminal is provided in the high-frequency signal feeding unit and the ground terminal is grounded, the impedance matching of the two tuning circuits is taken to separate the high-frequency signals received by the first and second tuning circuits, respectively. Therefore, it is possible to provide a receiving apparatus that can output and receive from one high-frequency signal output terminal without interfering with each other.

According to the third aspect of the present invention, in a receiving apparatus including a tunable antenna that receives a high-frequency signal in one continuous frequency band, the first receiving element made of a metal conductor and the first receiving element A first tuning circuit that is electrically connected to one end of the wave receiving element and that receives a high-frequency signal on the low frequency band side of the frequency band; and a metal conductor. And a second variable capacitance means electrically connected to one end of the second receiving element and receiving a high frequency signal on the high frequency band side of the frequency band. Two tuning circuits, a high-frequency signal feeder electrically connected to the first receiving element of the first tuning circuit and the second receiving element of the second tuning circuit, and the high-frequency signal Provided in the power feeding unit and received by the first and second tuning circuits, respectively A high-frequency signal output terminal for outputting a high-frequency signal, a coaxial line electrically connected to the high-frequency signal output terminal, a tuner circuit connected to the high-frequency signal output terminal via the coaxial line, and the high-frequency signal A capacitor electrically connected to the power supply unit, a ground terminal electrically connected to the other end of the capacitor and grounded, and a control voltage applied to the first and second variable capacitance means are applied to the high frequency A control voltage superimposing circuit for superimposing on the high-frequency signal output from the signal output terminal, and electrically connected to the control voltage superimposing circuit, from the high-frequency signal output terminal via the first and second receiving elements possess a control circuit for controlling the capacity of said first and said control voltage is applied to the second variable capacitance means and the first and second variable capacitance means, said second tuning circuit The reception frequency band is larger than the reception frequency band of the first tuning circuit, the length of the first reception element is longer than the length of the second reception element, and the capacitance of the first variable capacitance means There is provided a receiving apparatus including a tunable antenna whose change ratio is smaller than the capacity change ratio of the second variable capacitance means .

  Since high frequency signals in one continuous frequency band are received by the two tuning circuits, sufficient reception sensitivity can be obtained. Further, since the high-frequency signal output terminal and the tuner are electrically connected by a coaxial line, the high-frequency signals received by the first and second tuning circuits can be combined into one high-frequency signal without interfering with each other. It can be output from the signal output terminal and received. In addition, a capacitor is electrically connected to the high frequency signal output terminal, and a control voltage superimposing circuit for superimposing a control voltage on the high frequency signal output output from the high frequency signal output terminal is provided. Since the control voltage is applied to the two variable capacitance means, the high-frequency signal output line and the control voltage line can be unified.

  According to the present invention, one continuous frequency band is divided into a low frequency band side and a high frequency band side, and a high frequency signal is output from one output terminal even when two antennas receive each frequency. In addition, sufficient reception sensitivity (output intensity) can be obtained.

Embodiments of the present invention will be described below.
[First Embodiment]

  FIG. 1 is a diagram illustrating a basic configuration example of a receiving apparatus including a tunable antenna according to the first embodiment of this invention.

  The receiving apparatus includes a tunable antenna 100 and a main body 200 on which the tunable antenna is mounted.

  The tunable antenna 100 is electrically connected to two receiving elements 11 and 12 printed on the printed wiring board 1 and one end portion (one end or a place away from one end) of each receiving element 11 and 12. The variable capacity means 21 and 22 are connected to each other and one high-frequency signal power supply unit 3. The first receiving circuit 11 and the first variable capacitance means 21 constitute a first tuning circuit, and the second receiving element 12 and the second variable capacitance means 22 constitute a second tuning circuit. Is done. The first tuning circuit and the high-frequency signal feeding unit 3 constitute a first antenna, and the second tuning circuit and the high-frequency signal feeding unit 3 constitute a second antenna.

  Each of the variable capacitance means 21 and 22 is connected to the connection portions 41 and 42 serving as one end portions of the wave receiving elements 11 and 12 and the frequency control terminals 51 and 52 for applying a control voltage for controlling the reception frequency. And ground terminals 61 and 62 for variable capacitance means.

  The cathodes of the variable capacitance diodes 71 and 72 are electrically connected to the connection portions 41 and 42 of the wave receiving elements 11 and 12, and the chip capacitors 81 and 82 and one ends of the chip resistors 91 and 92 are connected to the anode. Electrically connected.

  The other ends of the chip resistors 91 and 92 are electrically connected to one ends of the frequency control terminals 51 and 52. The chip resistors 91 and 92 apply a control voltage for controlling the capacitance values of the variable capacitance diodes 71 and 72, and a high frequency signal received by the wave receiving elements 11 and 12 flows into the frequency control terminals 51 and 52. It works to prevent it.

  The other ends of the chip capacitors 81 and 82 are electrically connected to one ends of the variable capacitance means ground terminals 61 and 62. The chip capacitors 81 and 82 act as a DC cut for preventing the control voltage from being applied to the variable capacitance means ground terminals 61 and 62.

The other ends of the wave receiving elements 11 and 12 are electrically connected to each other, and are further electrically connected to the high-frequency signal power supply unit 3. The high-frequency signal power supply unit 3 includes a high-frequency signal output terminal 31 and an impedance matching ground terminal 32. With the ground connection of the impedance matching ground terminal 32, the characteristic impedance of the tunable antenna can be matched to approximately 50Ω.
Further, by providing the impedance matching ground terminal 32, each high frequency signal is output from one high frequency signal output terminal 31 without causing interference between the high frequency signals respectively received by the first and second tuning circuits. Can be taken out and received. Note that the two high-frequency signals output from the high-frequency signal output terminal 31 are input to a tuner circuit 101 to be described later, and then only a desired high-frequency signal is processed.
The other ends of the wave receiving elements 11 and 12 are not electrically connected to each other (the other end is not made common), and the other ends of the wave receiving elements 11 and 12 are formed separately, and each other end (the other end) Alternatively, a place at a distance from the other end may be electrically connected to the high-frequency signal power supply unit 3.

A main body 200 on which the tunable antenna 100 is mounted includes a receiving apparatus main body substrate 10 mainly including a tuner circuit 101 and a reception frequency control circuit 103. The printed circuit board 1 on which the tunable antenna 100 is mounted is mounted on the receiver main body substrate 10. The other ends of the variable capacitance means ground terminals 61 and 62 and the other end of the impedance matching ground terminal 32 of the tunable antenna 100 are electrically connected to a ground surface (not shown) of the receiving device main body substrate 10. The high frequency signal output terminal 31 is electrically connected to the input terminal 102 of the tuner circuit 101 through a wiring 106. The frequency control terminals 51 and 52 are electrically connected to the reception frequency control circuit 103 outside the tunable antenna through a wiring 105. The reception frequency control circuit 103 controls the capacitance values of the variable capacitance diodes 71 and 72 with a single control voltage.

  Next, the operation of the tunable antenna according to the first embodiment will be described with reference to FIG. FIG. 2 shows VSWR on the horizontal axis as viewed from the high-frequency signal output terminal 31 of the tunable antenna of FIG. The characteristic (A) of the solid line shown in FIG. 2 shows when the control voltage of the variable capacitance diodes 71 and 72 is 0.0V. At this time, the VSWR is low in two bands, ie, the band 111 where the wave receiving element 11 can be received and the band 112 where the wave receiving element 12 can be received, and this tunable antenna can be received through these two channels. It is shown that.

  On the other hand, the broken line characteristic (B) shown in FIG. 2 shows the characteristic when the control voltage is set to 3.0 V, and the band 113 in which the wave receiving element 11 can be received and the wave receiving element 12 receives the wave. The VSWR is low in the two 114 possible bands.

  From the above, the band received by the wave receiving element 11 with the control voltage of 0.0 V to 3.0 V is the band from 111 to 113. That is, about 1/2 of the entire band of 470 MHz to 770 MHz can be covered. On the other hand, the receiving element 12 can receive from the band 112 to the band 114. That is, the remaining half of the bandwidth can be covered.

Therefore, in order to tune to each channel assigned to the entire band from 470 MHz to 770 MHz, control may be performed according to two corresponding curves of the solid line (A) among the corresponding curves of the reception frequency and the control voltage shown in FIG. .
As shown in FIG. 2, the high frequency side of the band (111 to 113) received by the first tuning circuit overlaps the low frequency side of the band (112 to 114) received by the second tuning circuit. Thus, the first and second tuning circuits are designed. In the overlapping frequency band, it is preferable to use a tuning circuit that increases the voltage applied to the variable capacitance diode. That is, when receiving 620 MHz as shown in FIG. 2, it is preferable to use the first tuning circuit (at 3.0 V). This is because the higher the voltage applied to the variable capacitance diode, the smaller the resistance component of the variable capacitance diode and the better the antenna gain.

  In the tunable antenna according to the conventional example, since one receiving element covers the entire band of 470 to 770 MHz, the receiving element having the same inductance value as the receiving element 11 or the receiving element 12 is shown in FIG. As shown by the broken line (B), the control voltage must be applied from 0 to 6V. In addition, if it is designed so that one receiving element covers the entire band of 470 to 770 MHz and can be controlled from 0 V to 3 V, the receiving frequency is proportional to the magnitude of the inductance L. It is necessary to make the wave element small, and a decrease in antenna gain is inevitable.

According to the tunable antenna and the receiving apparatus of the first embodiment, one or more of the following effects are provided.
(1) It is possible to control a tunable antenna with a control voltage of 3V, which is normally provided in mobile terminals, by receiving a high-frequency signal having a continuous frequency band of 470 to 770 MHz by two tuning circuits. Therefore, it is not necessary to make the receiving element small in order to reduce the inductance value, the antenna gain is not lowered, and sufficient reception sensitivity can be obtained.
(2) In a case where a high frequency signal having one continuous frequency band is divided and received by two tuning circuits, when two tuning circuits are electrically connected to be taken out from one high frequency output terminal, The high-frequency signals received by the first and second tuning circuits interfere with each other and cannot be separated, but according to the first embodiment, the high-frequency signal power supply unit and the high-frequency signal output terminal together with the impedance matching ground terminal Therefore, if the impedance matching ground terminal is grounded and impedance matching of the two tuning circuits is performed, one high frequency signal received by each of the first and second tuning circuits is not interfered with each other. It can be taken out from the high-frequency signal output terminal and separated.
Note that the impedance matching matching of the two tuning circuits is performed by changing the shape of the U-shaped portion (slit portion) of the power feeding unit 3.
(3) Further, the tunable antenna can be reduced in size so that it can be built in the casing of the wireless device.
[Second Embodiment]

  FIG. 4 shows a second embodiment of the present invention and is a diagram showing a modified configuration example of a receiving apparatus provided with a tunable antenna. 4 differs from FIG. 1 in that the control voltage is superimposed on the high-frequency signal output terminal.

As in the first embodiment, the tunable antenna according to the second embodiment includes two receiving elements 11 and 12 and variable capacitance means 21 electrically connected to one end of each receiving element, 22 and one high-frequency signal feeder 3 electrically connected to the other end of each receiving element. Each of the variable capacitance means 21 and 22 includes connection portions 41 and 42 to the wave receiving elements and variable capacitance means ground terminals 61 and 62 for ground connection.
Unlike the tunable antenna of the first embodiment, in the tunable antenna of the second embodiment, the voltage is applied to the variable capacitance diodes 71 and 72 from the receiving elements 11 and 12 side. The receiving element connection portions 41 and 42 and the anodes of the variable capacitance diodes 71 and 72 are electrically connected. On the other hand, in the tunable antenna according to the first embodiment, since voltage is applied to the variable capacitance diodes 71 and 72 from the capacitors 81 and 82 side, the receiving element connection portions 41 and 42 and the variable capacitance are connected. The cathodes of the diodes 71 and 72 are electrically connected.
Chip capacitors 81 and 82 and chip resistors 91 and 92 are electrically connected in parallel between the cathodes of the variable capacitance diodes 71 and 72 and the ground terminals 61 and 62 for variable capacitance means. The chip resistors 91 and 92 function to prevent electric charges from being accumulated at the cathodes of the variable capacitance diodes 71 and 72.

  The chip capacitors 81 and 82 are electrically connected in series with the variable capacitance diodes 71 and 72 to be used for fine adjustment of the capacitance values of the variable capacitance means 21 and 22. The other ends of the wave receiving elements 11 and 12 are electrically connected to the high-frequency signal feeding unit 3. The high-frequency signal power supply unit 3 includes a high-frequency signal output terminal 31 and a DC cut chip capacitor 33.

In the second embodiment, since a control voltage for controlling the reception frequency is superimposed on the high frequency signal output terminal 31, a DC cut chip capacitor 33 having a DC cut action is required. The DC cut chip capacitor 33 is electrically connected to a ground surface (not shown) of the receiving apparatus main body substrate 10 via a DC cut ground terminal 32a.
Further, according to the second embodiment, the DC cut chip capacitor 33 electrically connected to the high frequency signal output terminal 31 is provided, and one end thereof is grounded via the DC cut ground terminal 32a, and the two The impedance matching matching of the tuning circuit is performed. This prevents the control voltage to be applied to the variable capacitance means 71 and 72 from being applied to the DC cut ground terminal 32a and also interferes with the high-frequency signals received by the first and second tuning circuits, respectively. Without being performed, the signal can be taken out from one high-frequency signal output terminal 31 and received.

The high frequency signal output terminal 31 is electrically connected to the tuner circuit 101 via the coaxial cable 121. As a result, the high-frequency signals received by the two receiving elements 11 and 12 are input to the tuner circuit 101 via the coaxial cable 121 serving as a coaxial line. Further, a control voltage is applied to the variable capacitance diodes 71 and 72 provided in the respective tuning circuits using the coaxial cable 121. Thus, in order to superimpose the high-frequency signal received by each receiving element and this control voltage, it is necessary to incorporate the superimposing circuit 123 on the tuner circuit 101 side. The superposition circuit 123 includes a chip capacitor 125 provided between the tuner input terminal 102 and the core wire 122 of the coaxial cable 121, and a chip resistor 126 provided between the core wire 122 of the coaxial cable 121 and the reception frequency control circuit 103. Composed.

  In the second embodiment, the characteristic impedance of the tunable antenna is matched to about 50Ω by the coaxial cable 121 instead of the impedance matching ground terminal 32 used in the first embodiment.

According to the second embodiment, since the control voltage can be superimposed on the high-frequency signal output terminal 31, the frequency control terminals 51 and 52 required in the first embodiment are not necessary. In particular, when the tunable antenna 100 and the tuner circuit 101 are installed at a distance from each other, the number of wirings can be reduced by one and the wiring cost can be reduced.
Particularly, it is suitable for a mobile phone having a hinge part composed of two axes, and the tunable antenna 100 is arranged on the liquid crystal display side, the receiver main body substrate 10 is arranged on the keyboard side, and the coaxial cable 121 is arranged on the hinge part. That's fine.
Note that a microstrip line may be used instead of the coaxial cable 121. [Third embodiment]

FIG. 5 shows the third embodiment of the present invention and is a diagram showing a modified configuration example of a receiving apparatus including a tunable antenna. The configuration of FIG. 5 is different from that of FIG. 4 in that the length ratio (inductance ratio) between the first receiving element 11 and the second receiving element 12 is changed.
The length of the first wave receiving element 11 is a distance a from the connection part 41 to the power feeding part 3, and the length of the second wave receiving element 12 is a distance b from the connection part 42 to the power feeding part 3. is there.

  Similar to the second embodiment, the tunable antenna of the third embodiment includes two receiving elements 11 and 12 and variable capacitance means 21 electrically connected to the respective receiving elements 11 and 12. , 22 and one high-frequency signal output terminal 31. Each variable capacitance means 21, 22 includes variable capacitance diodes 71, 72. In the third embodiment, the length (a) of the first receiving element 11 is set larger than the length (b) of the second receiving element 12. This is because the inductance L of the first wave receiving element 11 on the low frequency receiving side is increased to improve the antenna gain. Furthermore, the capacitance change ratio of the variable capacitance diode 72 electrically connected to the second wave receiving element 12 is set larger than the capacitance change ratio of the variable capacitance diode 71 electrically connected to the first wave receiving element 11. is doing.

  Next, the operation of the tunable antenna according to the third embodiment will be described with reference to FIGS. FIG. 6 shows the VSWR in terms of the horizontal axis frequency as viewed from the high-frequency signal output end 31 of the tunable antenna of FIG. A characteristic (C) indicated by a solid line in FIG. 6 indicates a characteristic when the control voltage applied to the variable capacitance diodes 71 and 72 is 0.0V. A characteristic (D) indicated by a broken line in the figure indicates a characteristic when the control voltage is set to 3.0V. When the control voltage is changed from 0.0 V to 3.0 V, the band that can be received by the first receiving element 11 changes from the band 111 to the band 113, and is about 1/3 of the entire band of 470 MHz to 770 MHz. That is, it covers from 470 MHz to 570 MHz.

On the other hand, the 112 band that can be received by the second receiving element 12 changes to the 114 band and covers the remaining 2/3 band. By setting the band that the first receiving element 11 must receive to about 1/3 of the entire band, the upper limit of the frequency change can be set as low as 570 MHz, and the length of the first receiving element 11 is increased. In addition, the capacitance change ratio of the variable capacitance diode 71 can be reduced. When the capacitance change ratio of the variable capacitance diode is small, the resistance component is small, so that the first receiving element 11 can be lengthened, and the band received by the first receiving element 11, the antenna gain of 470 to 570 MHz. The effect of improvement can be expected.

  FIG. 7 shows the relationship between the reception frequency and the control voltage of the tunable antenna according to the third embodiment. In order to tune to each channel allocated to the entire band from 470 MHz to 770 MHz, control may be performed according to two corresponding curves of the solid line (A) among the corresponding curves of the reception frequency and the control voltage shown in FIG. When receiving 570 MHz, the first tuning circuit (at 3.0 V) is used. The larger the voltage applied to the variable capacitance diode 71, the smaller the resistance component of the variable capacitance diode. Therefore, the antenna gain is good.

  FIG. 8 shows the relationship between the reception frequency and antenna gain of the tunable antenna according to the third embodiment. The antenna gain of the third embodiment degrades the antenna gain at 570 to 770 MHz as much as the antenna gain in the 470 to 570 MHz band is improved as shown by the solid curve (E). However, in the tunable antenna built in the cellular phone casing, as shown in the gain (F) of the conventional example, the antenna gain is originally higher as the frequency is higher. Therefore, according to the third embodiment, the antenna gain is leveled, which is convenient.

  In each of the above-described embodiments, the case where the tunable antenna is applied to the receiving device has been described. However, the present invention is not limited to this and can be applied to the transmitting device and the transmitting / receiving device. It is.

  Preferred forms of the present invention will be additionally described.

  The antenna is a tunable antenna whose resonance frequency can be controlled from the outside of the antenna, and includes a receiving element that is a metal conductor and variable capacitance means that can be controlled from outside the antenna, and the receiving element and the variable capacitance means include: It is composed of two sets, and these receiving elements are electrically connected to one high-frequency signal output terminal, and this high-frequency signal section is grounded.

  The variable capacitance means is controlled in its capacitance value by a control voltage applied from an external circuit of the antenna, and the control voltage is a single system voltage for all the variable capacitance means included in the tunable antenna. It is characterized by controlling.

  The control voltage is superimposed on the high-frequency signal terminal, and the variable capacitance means is applied with the control voltage via the receiving element.

  A first receiving element (for low-frequency reception); a second receiving element (for high-frequency reception); a first variable capacitance means connected to the first receiving element; And a second variable capacitance means connected to the wave receiving element. The inductance value of the first wave receiving element is larger than that of the second wave receiving element, and the capacitance change of the first variable capacitance means. The ratio is smaller than the second variable capacitance means.

  Further, the resonance frequency upper limit value that can be controlled by the first wave receiving element and the first variable capacitance means is higher than the resonance frequency lower limit value that can be controlled by the second wave receiving element and the second variable capacitance means. In the frequency band to be received, the first receiving element receives a high-frequency signal.

  Further, the present invention is a receiving device, a transmitting device, and a transmitting / receiving device provided with the tunable antenna.

[Example 1]

  Example of experiment with 2 tuning circuits with 0-3V drive

  For the tunable antenna of the first embodiment shown in FIG. 1, in order to cover the entire band of 470 to 770 MHz, an experiment was performed by setting the values of the variable capacitance diode, the chip capacitor, and the inductance as follows. 1. The tuning frequency of the second antenna was measured. This experiment is common to the tunable antenna of the second embodiment shown in FIG.

The total length (longitudinal direction) of the first wave receiving element 11 and the second wave receiving element 12 was set to 40 mm, which is a size that can be accommodated in a mobile phone. The first and second variable capacitance diodes 71 and 72 which are the first and second variable capacitance means 21 and 22 both have capacitance changes from 1.8 pF to 4.4.
What changed to 5 pF was used. The applied voltage for driving these variable capacitance diodes 71 and 72 was set to 0 to 3V. The capacitance values of the chip capacitors 81 and 82 of the first and second antennas were 6 pF and 2 pF. The inductances of the first and second antennas are both 45 nH. These set values and measurement results are shown in FIG.

The tuning frequency of the first antenna was 470 MHz to 640 MHz, and the tuning frequency of the second antenna was 620 MHz to 770 MHz. The voltage applied to the variable capacitance diode of the tunable antenna was in the range of 0 to 3 V, and the inductance could be increased. As a result, the size of the antenna can be increased, and the antenna gain can be improved.
[Comparative Example 1]

  Example of experiment when 0 to 6V drive and one tuning circuit

  In order to cover the entire band of 470 to 770 MHz, the tunable antenna of the conventional example shown in FIG. 9 was tested by setting the values of the variable capacitance diode, the chip capacitor, and the inductance as follows. The tuning frequency of the antenna was measured.

The length (longitudinal direction) of the wave receiving element 11 was set to 40 mm, which is a size that can be accommodated in a mobile phone as in the first embodiment. The variable capacitance diode which is the variable capacitance means 21 has a capacitance change of 1.0.
What changed from pF to 4.5 pF was used. The chip capacitor capacitance value of the antenna was 6 pF. The inductance of the antenna was 45 nH. These set values and measurement results are shown in FIG. In order to cover the entire band of 470 to 770 MHz, the variable capacitance diode had to be driven with an applied voltage of 0 to 6V.
[Comparative Example 2]

  Experimental example when one tuning circuit is used with 0-3V drive

  Comparative Example 2 uses a tunable antenna having basically the same configuration as Comparative Example 1, and in order to drive from 0 to 3 V, the values of variable capacitance diode, chip capacitor, and inductance are set as follows. The tuning frequency of the antenna was measured.

The variable capacitance diode, which is a variable capacitance means, has a capacitance change of 1.8 pF to 4.5 p.
What changed to F was used. The inductance of the antenna was 25 nH. These set values and measurement results are shown in FIG. In order to cover the entire band of 470 to 770 MHz, the chip capacitor capacitance value of the antenna had to be 1000 pF.

As shown in FIG. 14, when the same variable capacitance diode as that of the first embodiment is used in the comparative example 2, it is necessary to reduce the inductance value in order to achieve low voltage driving (0 to 3 V driving). Then, it is necessary to make the antenna element small (proportional to the magnitude of the inductance), the reception sensitivity is also reduced, and the antenna gain is reduced.
[Example 2]

  Experimental example when 0 to 3V drive with two tuning circuits and the length is changed

  With respect to the tunable antenna of the third embodiment shown in FIG. 5, in order to cover the entire band of 470 to 770 MHz, an experiment was performed by setting the values of the variable capacitance diode, the chip capacitor, and the inductance as follows. 1. The tuning frequency of the second antenna was measured.

The total length (longitudinal direction) of the first wave receiving element and the second wave receiving element was set to 40 mm, which is a size that can be accommodated in the mobile phone as in the first embodiment. As the first variable capacitance diode which is the first variable capacitance means, one whose capacitance change is changed from 1.8 pF to 4.5 pF was used. As the second variable capacitance diode which is the second variable capacitance means, one having a capacitance change from 1.8 pF to 4.5 pF was used. The applied voltage for driving these variable capacitance diodes was 0-3V. The chip capacitor capacitance values of the first and second antennas were both 4 pF. The inductances of the first and second antennas were 52 nH and 35 nH. The lengths of the first and second antennas were 45 mm and 24 mm. These set values and measurement results are shown in FIG.

  The tuning frequency of the first antenna was 470 MHz to 570 MHz, and the tuning frequency of the second antenna was 560 MHz to 770 MHz. The inductance of the first antenna (low frequency receiving antenna) could be further increased. As a result, the reception sensitivity in the low frequency band (470 to 570 MHz) could be improved.

The figure which shows the structure of the receiver provided with the tunable antenna by the 1st Embodiment of this invention. The figure which shows the input characteristic (VSWR) of the tunable antenna by the 1st Embodiment of this invention. The figure which shows the relationship between the receiving frequency and control voltage of a tunable antenna by the 1st Example of this invention. The figure which shows the structure of the receiver provided with the tunable antenna by the 2nd Embodiment of this invention. The figure which shows the structure of the receiver provided with the tunable antenna by the 3rd Embodiment of this invention. The figure which shows the input characteristic (VSWR) of the tunable antenna by the 3rd Embodiment of this invention. The figure which shows the relationship between the receiving frequency and control voltage of a tunable antenna by the 3rd Embodiment of this invention. The figure which shows the relationship between the receiving frequency and antenna gain of a tunable antenna by the 3rd Embodiment of this invention. The figure which shows the structure of the receiver provided with the tunable antenna by a prior art example. The figure which shows the input characteristic (VSWR) of the tunable antenna by a prior art example. The figure which shows the relationship between the receiving frequency and control voltage of a tunable antenna by a prior art example. The figure which shows the experimental result of Example 1 of this invention. The figure which shows the experimental result of the comparative example 1. The figure which shows the experimental result of the comparative example 2. FIG. The figure which shows the experimental result of Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed wiring board 10 Reception apparatus main body board | substrates 11 and 12 Receive element 21 and 22 Variable capacity | capacitance means 3 High frequency signal electric power feeding part 31 High frequency signal output terminal 32 Impedance matching ground terminal 32a DC cut ground terminal 33 DC cut chip capacitor 41 , 42 Receiving element connecting portions 51, 52 Frequency control terminals 61, 62 Variable capacitance means ground terminals 71, 72 Variable capacitance diodes 81, 82 Chip capacitors 91, 92 Chip resistors 10 Receiver main body substrate 100 Tunable antenna 101 Tuner circuit 102 Tuner Input 103 Reception Frequency Control Circuit 105, 106 Wiring 111 Band 112 Received by the First Wave Receiver Element Band Band Received by the Second Wave Receiver Element 121 Coaxial Cable (Coaxial Line)
122 coaxial cable core 123 control voltage superposition circuit 200 main body

Claims (5)

In a tunable antenna that receives a high-frequency signal in one continuous frequency band,
A first receiving element made of a metal conductor and a first variable capacitance means electrically connected to one end of the first receiving element, and a high frequency on a low frequency band side of the frequency band A first tuning circuit for receiving a signal;
And a second variable capacitance means electrically connected to one end of the second wave receiving element and the second wave receiving element comprising a metal conductor, a high frequency band side of the high-frequency signal of the frequency band A second tuning circuit for receiving
The first and second receiving elements are electrically connected to the other end of the first receiving element of the first tuning circuit and the other end of the second receiving element of the second tuning circuit. A high-frequency signal power supply unit for supplying power to the receiving element;
A high-frequency signal output terminal that is electrically connected to the high-frequency signal power supply unit and outputs a high-frequency signal received by each of the first and second tuning circuits;
A ground terminal that is electrically connected to the high-frequency signal power supply unit and grounded;
Equipped with a,
The reception frequency band of the second tuning circuit is larger than the reception frequency band of the first tuning circuit,
The length of the first receiving element is longer than the length of the second receiving element,
A tunable antenna characterized in that the capacitance change ratio of the first variable capacitance means is smaller than the capacitance change ratio of the second variable capacitance means . The tunable antenna according to claim 1 .
The upper limit value of the receiving frequency that can be controlled by the first receiving element and the first variable capacitance means is the lower limit value of the receiving frequency that can be controlled by the second receiving element and the second variable capacitance means. A tunable antenna characterized by being higher. The tunable antenna according to claim 1 or 2,
The length of the first receiving element is a length from a connection portion with the first variable capacitance means to the high-frequency signal power supply portion,
The length of the second receiving element is a length from a connection portion with the second variable capacitance means to the high-frequency signal feeding portion . A tunable antenna according to any one of claims 1 to 3,
A tuner circuit electrically connected to the high-frequency signal output terminal;
A control circuit for controlling the first and second variable capacitance means by applying a common control voltage to the first and second variable capacitance means;
Receiving device provided with a tunable antenna. In a receiving apparatus including a tunable antenna that receives a high-frequency signal in one continuous frequency band,
A first receiving element made of a metal conductor and a first variable capacitance means electrically connected to one end of the first receiving element, and a high frequency on a low frequency band side of the frequency band A first tuning circuit for receiving a signal;
And a second variable capacitance means electrically connected to one end of the second wave receiving element and the second wave receiving element comprising a metal conductor, a high frequency band side of the high-frequency signal of the frequency band A second tuning circuit for receiving
A high-frequency signal feeder that is electrically connected to the first receiving element of the first tuning circuit and the second receiving element of the second tuning circuit;
A high-frequency signal output terminal that is provided in the high-frequency signal power supply unit and outputs a high-frequency signal received by each of the first and second tuning circuits;
A coaxial line electrically connected to the high-frequency signal output terminal;
A tuner circuit connected to the high-frequency signal output terminal via the coaxial line;
A capacitor electrically connected to the high-frequency signal power supply unit;
A ground terminal electrically connected to the other end of the capacitor and grounded;
A control voltage superimposing circuit for superimposing a control voltage applied to the first and second variable capacitor means on the high frequency signal output from the high frequency signal output terminal;
Electrically connected to the control voltage superimposing circuit, applying the control voltage from the high-frequency signal output terminal to the first and second variable capacitance means via the first and second receiving elements, and A control circuit for controlling the capacity of the first and second variable capacity means;
Have,
The reception frequency band of the second tuning circuit is larger than the reception frequency band of the first tuning circuit,
The length of the first receiving element is longer than the length of the second receiving element,
A receiving apparatus comprising a tunable antenna having a capacitance change ratio of the first variable capacitance means smaller than a capacitance change ratio of the second variable capacitance means .

Images