JP5169208B2 - Wireless speaker device - Google Patents

Description

  The present invention relates to a wireless speaker device that wirelessly receives and emits an audio signal.

An example of this type of wireless speaker device is disclosed in Patent Document 1. The apparatus disclosed in Patent Document 1 is configured by attaching a receiver, a battery, and a speaker to clothes worn by a worker on a construction site. The receiver receives an audio signal such as voice for instruction and supplies the audio signal to a speaker to emit the voice. Since this type of device does not need to be connected to the audio signal supply source by a cord when used, there are few restrictions on the user's behavior and it has the advantage of being easy to use.
JP 2003-268609 A

  By the way, the conventional wireless speaker device disclosed in Patent Document 1 has a problem that it is necessary to incorporate a battery or connect to an AC power source in order to operate the receiver and the speaker. Further, when the battery is built in, there is a problem that the battery must be replaced every time the battery is consumed.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a wireless speaker device that does not require a power source such as a battery.

The present invention includes a receiving antenna and an electrostatic speaker that vibrates and radiates a diaphragm in accordance with an applied AC voltage, and the AC voltage applied to the electrostatic speaker from the AC voltage generated in the receiving antenna. The wireless speaker device is configured to generate the above.
In such a wireless speaker device, an AC voltage applied to the electrostatic speaker is generated from an AC voltage generated in the receiving antenna, and the diaphragm of the electrostatic speaker is vibrated and radiated. Here, the electrostatic loudspeaker is a capacitive load with little loss, and can efficiently convert the applied power into the motion of the diaphragm. Therefore, the audio signal can be received by the receiving antenna of the wireless speaker device and output as a sound from the electrostatic speaker without supplying power to the wireless speaker device by a battery or the like.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a wireless audio transmission system including a wireless speaker device 100 according to an embodiment of the present invention. The wireless speaker device 100 according to the present embodiment is a speaker device that is carried by a user, receives an audio signal from the outside without receiving power from a battery or the like, and outputs it as sound. The wireless audio transmission system shown in FIG. 1 includes a transmission device 200 that transmits a carrier wave on which an audio signal is superimposed to the wireless speaker device 100.

  In the present embodiment, magnetic field resonance type power transmission is performed between the transmission device 200 and the wireless speaker device 100. As a means for that, the transmission apparatus 200 includes a transmission circuit 201 and a transmission antenna 202. Here, the transmission circuit 201 generates a carrier wave that is a pulse train having a constant frequency, performs AM (Amplitude Modulation) modulation on the carrier wave by an audio signal to be transmitted, and transmits a high-frequency current corresponding to the modulated carrier wave. A circuit that flows through the antenna 202. The transmission antenna 202 includes a coil 202L formed by, for example, winding a copper wire once in a circular shape. In the middle of the coil 202L, two electrodes facing each other and spaced apart are inserted, and a dielectric is sandwiched between the two electrodes to constitute a capacitor 202C. Here, the coil 202L and the capacitor 202C constitute a series resonance circuit having a resonance frequency identical to the frequency of the carrier wave generated by the transmission circuit 201.

  Next, the wireless speaker device 100 according to the present embodiment will be described. The wireless speaker device 100 includes a reception antenna 2 as a means for receiving magnetic field resonance type power transmission from the transmission device 200. Similar to the transmission antenna 202 on the transmission apparatus 200 side, the reception antenna 2 includes a coil 2L in which a copper wire is wound once in a circular shape. Further, in the middle of the coil 2L, two electrodes facing each other and spaced apart are interposed, and a dielectric is sandwiched between the two electrodes to constitute a capacitor 2C. Here, the coil 2L and the capacitor 2C constitute a series resonance circuit having the same resonance frequency as the resonance frequency of the transmission antenna 202 on the transmission device 200 side.

Here, various conditions for causing good magnetic field resonance type power transmission between the transmitting antenna 202 and the receiving antenna 2 will be described. First, the resonance frequency ω of the receiving antenna 2 and the transmitting antenna 202 is given by the following equation, where L is the inductance of the coil 2L or 202L and C is the capacitance value of the capacitor 2C or 202C.
ω = 1 / √ (LC) (1)
Therefore, when determining the configurations of the reception antenna 2 and the transmission antenna 202, the inductance L and the capacitance value C are adjusted by adjusting the size and shape of the antenna so that the resonance frequency ω becomes the same as the frequency of the carrier wave. There is a need.

  More specifically, in order to perform power transmission on the magnetic field resonance side, the wavelength λ of the alternating magnetic field generated between the transmitting antenna 202 and the receiving antenna 2, the distance D between the transmitting antenna 202 and the receiving antenna 2, The ratio λ: D: r between the single turn coils 202L and the radius r of 2L is preferably about 100: 10 or less: 1. Therefore, for example, if the frequency of the carrier wave (= frequency of the alternating magnetic field) is 20 MHz, the wavelength λ of the alternating magnetic field is the speed of light / 20 MHz = 15 m, and the distance D between the transmitting antenna 202 and the receiving antenna 2 is 1.5 m. In this case, the diameter 2r of the one-turn coils 202L and 2L is about 30 cm. Therefore, when the magnetic field resonance type power transmission is performed under the condition of the distance between transmission and reception D = 1.5 m, the inductance L of the one-turn coils 202L and 2L having such a diameter 2r = about 30 cm is calculated, and the above formula ( The capacitance values C of the capacitors 202C and 2C are determined so that the resonance frequency ω obtained in 1) is 20 MHz.

Further, the Q of the receiving antenna 2 is desirably 1000 or more. This Q is obtained by the following equation.
Q = ωL / Rabs (2)
Here, Rabs is a resistance of the one-turn coil 2L, and is a loss generated when the one-turn coil 2L radiates a magnetic field in free space in addition to the ohmic resistance of the lead wire of the one-turn coil 2L. Includes minutes. This resistance Rabs is given by the following equation.
Rabs≈ηc · r / a (3)
Here, a is the thickness (diameter) of the winding of the one-turn coil 2L. Ηc is given by the following equation.
ηc = √ ((μc · ω) / (2σ)) (4)
Here, μc is the magnetic permeability of the coil material used as the winding of the one-turn coil 2L, and σ is the conductivity of the coil material. As the resonance frequency ω increases, the effective diameter a of the winding of the one-turn coil 2L becomes shorter due to the skin effect. Therefore, when the resonance frequency ω is high and the influence of the skin effect cannot be ignored, it is necessary to thicken the winding in consideration of the influence.

  In the wireless speaker device 100 according to the present embodiment, a step-up transformer 4 is provided at the subsequent stage of the receiving antenna 2. The step-up transformer 4 is a transformer composed of a primary side coil 4A and a secondary side coil 4B, both of which are air cores. An AC voltage generated in the receiving antenna 2 is applied to the primary side coil 4 </ b> A, and the AC voltage generated in the secondary side coil 4 </ b> B is used to drive the electrostatic speaker 1. The step-up transformer 4 has a step-up ratio sufficient to generate an AC voltage necessary for driving the electrostatic speaker 1 from the secondary coil 4B.

  The DC voltage generation circuit 5 includes a rectifier circuit 6 and a limiter 7 and is composed of passive elements such as a resistor, a capacitor, a diode, and a constant voltage diode. Here, the rectifier circuit 6 rectifies the AC voltage applied to the primary coil 4A of the step-up transformer 4 and outputs a DC voltage. The limiter 7 outputs the output voltage of the rectifier circuit 6 to the electrostatic speaker 1 as a predetermined DC bias voltage VB, and limits the DC bias voltage so as to maintain a constant value.

  The electrostatic speaker 1 is a device that outputs an alternating voltage generated in the secondary coil 4B of the step-up transformer 4 as sound. FIG. 2 is a perspective view showing the external appearance of the electrostatic speaker 1. In FIG. 2, the diaphragm 10 is not shown in order to prevent the drawing from becoming complicated.

  As shown in the figure, the electrostatic speaker 1 is composed of a diaphragm 10, conductive cloths 20U and 20L, elastic members 30U and 30L, and a thread 40. In the present embodiment, the configurations of the conductive cloths 20U and 20L are the same, and the configurations of the elastic members 30U and 30L are the same. Therefore, when there is no particular need to distinguish the two, “L” and “U” Is omitted. Also, the dimensions of the components such as the diaphragm and the conductive cloth in FIG. 2 are different from the actual dimensions so that the shapes of the components can be easily understood.

  The diaphragm 10 is obtained by depositing a metal film or applying a conductive paint on a film such as PET (polyethylene terephthalate) or PP (polypropylene), and has a thickness of several μm to The thickness is about several tens of μm.

  The elastic member 30 is formed, for example, by compressing a batting which is an insulator by applying heat, and allows air to pass therethrough, and has a rectangular shape. The elastic member 30 is deformed when a force is applied from the outside, and returns to its original shape when the force applied from the outside is removed.

  The conductive cloth 20 is a cloth obtained by plain weaving conductive warp and weft having the same conductivity. The conductive cloth 20 has a rectangular shape and is plain woven so that air can pass therethrough, so that sound transmission is ensured. The thread 40 is, for example, a thread for sewing the conductive cloth 20, the elastic member 30, and the diaphragm 10, and the material thereof is a material that does not have conductivity, such as cotton.

  When assembling such an electrostatic speaker 1, first, the elastic member 30L is placed on the conductive cloth 20L. When placing the elastic member 30L on the conductive cloth 20L, the elastic member 30L is placed on the conductive cloth 20L such that each side of the elastic member 30L is positioned outside each side of the conductive cloth 20L.

  Next, the diaphragm 10 is placed on the elastic member 30L. When the diaphragm 10 is placed on the elastic member 30L, the diaphragm 10 is placed on the elastic member 30L such that each side of the diaphragm 10 is positioned inside each side of the elastic member 30L.

  Then, the elastic member 30U is placed on the diaphragm 10. When the elastic member 30U is placed on the diaphragm 10, the positions of the four corners of the elastic member 30U and the elastic member 30L overlap with each side of the elastic member 30U positioned outside each side of the diaphragm 10. In this way, the elastic member 30L is placed on the diaphragm 10. Here, since the lengths of the elastic member 30 in the X direction and the Y direction are longer than the lengths of the vibration plate 10 in the X direction and the Y direction, each side of the rectangular vibration plate 10 has an elastic member 30U and an elastic member 30L. It is located between the elastic members 30U and 30L without protruding from between them.

  Next, the conductive cloth 20U is placed on the elastic member 30U. When placing the conductive cloth 20U on the elastic member 30U, the positions of the four corners of the conductive cloth 20U and the conductive cloth 20L are Z while the respective sides of the conductive cloth 20U are positioned on the inner side of the respective sides of the elastic member 30U. The conductive cloth 20U is placed on the elastic member 30U so as to overlap in the direction.

  Then, after the conductive cloth 20, the diaphragm 10, and the elastic member 30 are overlaid, the respective members are sewn together with a thread 40 having no conductivity. As shown in FIG. 2, the members are sewn and restrained by the thread 40 penetrating the members, so that the conductive cloth 20, the elastic member 30, and the vibration plate 10 do not shift even when deformed. In addition, the elastic member 30 having insulation has a larger area than the diaphragm 10 and the conductive cloth 20, and each side of the elastic member 30 is located outside the respective sides of the diaphragm 10 and the conductive cloth 20. The conductive cloth 20 and the diaphragm 10 do not contact and short-circuit.

  Next, the electrical configuration of the electrostatic speaker 1 will be described. As shown in FIG. 1, a DC bias voltage VB output from the limiter 7 of the DC voltage generating circuit 5 is applied to the midpoint of the diaphragm 10 and the secondary coil 4B of the electrostatic speaker 1. For this reason, an electric field directed from the diaphragm 10 toward the conductive cloth 20U and an electric field directed from the diaphragm 10 toward the conductive cloth 20L are generated inside the electrostatic speaker 1. On the other hand, the output voltage of the secondary coil 4B of the step-up transformer 4 is applied to the conductive cloths 20U and 20L of the electrostatic speaker 1. Here, when the secondary coil 4B outputs a positive voltage such that the conductive cloth 20U side has a high potential and the conductive cloth 20L side has a low potential, the electric field generated between the conductive cloths 20U and 20L by this output voltage is The electric field from the diaphragm 10 toward the conductive cloth 20U is weakened, and the electric field from the diaphragm 10 toward the conductive cloth 20L is strengthened. As a result, the diaphragm 10 moves to the conductive cloth 20L side. On the other hand, when the secondary coil 4B outputs a negative voltage such that the conductive cloth 20U side has a low potential and the conductive cloth 20L side has a high potential, the electric field generated between the conductive cloths 20U and 20L by this output voltage is The electric field from the diaphragm 10 toward the conductive cloth 20U is strengthened, and the electric field from the diaphragm 10 toward the conductive cloth 20L is weakened. As a result, the diaphragm 10 moves to the conductive cloth 20U side. Thus, in the electrostatic speaker 1, the diaphragm 10 moves in a direction corresponding to the polarity of the voltage generated in the secondary coil 4B. Accordingly, when an AC voltage is output from the secondary coil 4B, the diaphragm 10 vibrates in the Z-axis direction shown in FIG. 2 according to the AC voltage, and according to the vibration state (frequency, amplitude, phase). Sound is generated from the diaphragm 10. The generated sound passes through at least one conductive cloth 20 and is radiated to the outside of the electrostatic speaker 1.

In this embodiment, the diaphragm 10, the conductive cloth 20, and the elastic member 30 constituting the electrostatic speaker 1 are restrained by the thread 40, so that the shape and structure of the electrostatic speaker 1 can be changed even if the electrostatic speaker 1 is deformed. The conductive cloth 20, the elastic member 30, and the diaphragm 10 do not come off without collapsing.
Moreover, since the diaphragm 10, the conductive cloth 20, and the elastic member 30 are flexible, they can be deformed into an arc shape, deformed along a curved surface, or freely deformed, and can be attached to clothes. .

  Moreover, since each member is flexible, there is no possibility of damaging the human body even if the human body collides. For this reason, if it is attached to the headrest or placed inside a full-face helmet, it can be pronounced at the ear without damaging the human body.

  As an aspect of mounting the wireless speaker device 100 according to this embodiment, there is mounting on clothes worn by a user. With reference to FIG. 3 and FIG. 4, the aspect of mounting on the clothes will be described.

  As already described, the electrostatic loudspeaker 1 has a cloth-like form as a whole and is highly flexible, so that it is suitable for mounting on clothes. In order to facilitate the mounting of the wireless speaker device 100 on clothes, it is preferable that parts other than the electrostatic speaker 1 are also formed in a cloth form in advance. Therefore, in the embodiment shown in FIG. 3, the receiving antenna 2 is mounted on the cloth 301, and the primary side coil 4A and the secondary side coil 4B of the step-up transformer 4 are mounted on another cloth 302. Various methods of mounting the receiving antenna 2 can be considered. For the one-turn coil 2L, a copper foil pattern having a width of about 100 μm is thermally bonded to the cloth 301, and the one-turn coil 2L is formed on the cloth 301. May be. Alternatively, the one-turn coil 2 </ b> L may be formed on the cloth 301 by sewing a SUS (Steel Use Stainless) wire having a diameter of about 0.1 mm into the cloth 301. The mounting of the primary side coil 4A and the secondary side coil 4B to the cloth 302 is the same. Note that the one-turn coil 2L mounted on the cloth 301 does not have to be circular as long as a necessary inductance L is obtained, and may be rectangular, for example. For example, the DC voltage generating circuit 5 may be mounted in an area of the cloth 302 where the step-up transformer 4 is not mounted.

  In order to reduce the required mounting area of the entire wireless speaker device 100, the cloth 302 on which the step-up transformer 4 and the DC voltage generating circuit 5 are mounted and the electrostatic speaker 1 may be stacked and integrated. However, the cloth 301 on which the receiving antenna 2 is mounted needs to be separated so as not to overlap the electrostatic speaker 1 and the cloth 302. If there is a metal material having a magnetic shielding effect on the coil surface of the single turn coil 2L of the receiving antenna 2, that is, the space before and after facing the cloth 301 to which the single turn coil 2L is fixed in FIG. This is because there is a problem in causing magnetic field resonance type power transmission between the transmitting antenna 202 and the receiving antenna 2.

  4A to 4C show examples in which the wireless speaker device 100 is mounted on a jumper 300, respectively. In the example shown in FIG. 4A, the cloth 301 on which the receiving antenna 2 is mounted is sewn on the chest portion of the jumper 300 as shown in FIG. 3 and the step-up transformer 4 and the DC voltage generating circuit 5 are mounted. What united 302 and the electrostatic type speaker 1 is sewn on the shoulder part of the jumper 300. FIG. In the example shown in FIG. 4C, the sewing position of the cloth 301 on which the receiving antenna 2 is mounted is different from that in FIG. In this example, the cloth 301 on which the receiving antenna 2 is mounted is sewn to the sleeve portion of the jumper 300. In the example shown in FIG. 4B, the receiving antenna 2 is not mounted in advance on the cloth 301 as shown in FIG. 3, but the receiving antenna 2 surrounds the arm of the user who wears the jumper 300. It is fixed to 300 arm parts.

  In order to perform magnetic resonance type power transmission satisfactorily, it is preferable that the coil surface of the transmitting antenna 202 and the coil surface of the receiving antenna 2 face each other. Therefore, the mounting mode of the receiving antenna 2 in FIGS. 4A and 4C is suitable when the transmitting antenna 202 is fixed to the wall. On the other hand, the mounting mode of the receiving antenna 2 in FIG. 4B is suitable when the transmitting antenna 202 is fixed to the floor or ceiling.

  As mentioned above, although the example which mounted the wireless speaker apparatus 100 in the jumper 300 was given, these are an example to the last, and each part of the wireless speaker apparatus 100 can be mounted in various places of the jumper 300. Further, for example, a plurality of reception antennas 2 facing different directions may be mounted on the jumper 300 and the reception antenna 2 suitable for receiving power transmission from the transmission antenna 202 may be used. Alternatively, for example, each unit of the two wireless speaker devices 100 can be mounted on a single jumper 300.

  Next, with reference to FIG. 5, an operation example of the entire wireless audio transmission apparatus including the wireless speaker apparatus 100 and the transmission apparatus 200 will be described. In the example illustrated in FIG. 5, the transmission antenna 202 of the transmission device 200 is fixed to one place on the wall that sandwiches the passage. This passage is, for example, a passage for an exhibition of pictures, and the width is about 3 m. The optimum value of the transmission / reception end distance D in the wireless audio transmission system is about 1.5 m.

  In FIG. 5, the user wearing the jumper 300 is walking along the passage. As shown in the example of FIG. 4C, the jumper 300 includes a cloth 301 on which the receiving antenna 2 is mounted and is sewn on a sleeve portion, and the step-up transformer 4 and the DC voltage generating circuit 5 are mounted on the jumper 300. What integrated 302 and the electrostatic speaker 1 is sewn on the shoulder part. When the user proceeds to the position of the transmission antenna 202 fixed to the wall, the transmission antenna 202 and the reception antenna 2 mounted on the jumper 300 worn by the user face each other. Further, since the optimum value of the distance D between the transmitting and receiving ends is half of the width of the passage, the distance between the transmitting antenna 202 fixed to the wall of the passage and the receiving antenna 2 fixed to the person walking in the middle of the passage is also the optimum value. Therefore, the magnetic resonance type power transmission can be performed under favorable conditions.

  The transmission circuit 201 (not shown in FIG. 5; see FIG. 1) AM-modulates the carrier wave by an audio signal of the guidance voice related to the picture being exhibited, for example, and passes a high-frequency current that is the AM-modulated wave to the transmission antenna 202. . Here, the transmitting antenna 202 and the receiving antenna 2 are resonant circuits having the same resonant frequency. Then, when a high-frequency current having the same carrier frequency as this resonance frequency is energized to the transmission antenna 202, a resonance magnetic field is formed in the space between the transmission antenna 202 and the reception antenna 2, and through this resonance magnetic field, The AM modulated wave on which the audio signal is superimposed is transmitted from the transmitting antenna 202 to the receiving antenna 2 with low loss.

  In the wireless speaker device 100 (not shown in FIG. 5, see FIG. 1) mounted on the jumper 300, the AC voltage taken out from the receiving antenna 2 is boosted by the step-up transformer 4 and the conductive cloth 20 </ b> U of the electrostatic speaker 1. And 20L. Further, a DC bias voltage VB is generated from the voltage applied to the primary coil 4A of the step-up transformer 4 by the DC voltage generating circuit 5, and the vibration plate 10 of the electrostatic speaker 1 and each of the conductive cloths 20U and 20L. Given in between. Thereby, the diaphragm 10 vibrates according to the output voltage of the step-up transformer 4, and sound is generated from the electrostatic speaker 1 located at the shoulder of the jumper 300. Here, the AC voltage extracted from the receiving antenna 2 is a carrier wave (pulse train) that is AM-modulated by the audio signal of the guidance voice, but the role of the step-up transformer 4 and the electrostatic speaker 1 as a low-pass filter that performs AM demodulation. Therefore, the electrostatic speaker 1 emits a guidance voice corresponding to the audio signal used for AM modulation of the carrier wave.

  As described above, according to the present embodiment, since the electrostatic speaker 1 with high power conversion efficiency is adopted as a speaker for radiation in the wireless speaker device 100, power is not supplied to the wireless speaker device by a battery or the like. Alternatively, the receiving antenna 2 can receive an audio signal and output it as sound. Further, according to the present embodiment, magnetic field resonance type power transmission is adopted as a power transmission method between the transmission antenna 202 and the reception antenna 2, and therefore the distance D between the transmission and reception ends can be made relatively long and is relatively low. A carrier wave on which an audio signal is superimposed can be transmitted with loss. In addition, according to the present embodiment, since each part of the wireless speaker device 100 is made into a flexible cloth, it can be mounted on clothes and the like, and a wireless audio transmission system that is easy to use for the user is realized. can do.

  Although one embodiment of the present invention has been described above, the present invention may have other embodiments. For example:

(1) FIG. 6 shows an example in which each part of the wireless speaker device 100 is mounted in a full-face helmet. In this example, the cloth 301 on which the receiving antenna 2 is mounted is sewed on the portion of the helmet that is in contact with the chin, and the cloth 302 on which the step-up transformer 4 and the DC voltage generating circuit 5 are mounted and the electrostatic speaker 1 are connected. The integrated piece is sewn on the inner part of the helmet where the ear hits. A motorcycle (not shown) is provided with a radio (not shown) and a transmission device 200. Here, the transmission circuit 201 of the transmission apparatus 200 AM-modulates the carrier wave with an audio signal such as traffic congestion information received by the radio, and passes a high-frequency current that is the AM-modulated wave to the transmission antenna 202. Thereby, magnetic field resonance type power transmission is performed between the transmission antenna 202 and the reception antenna 2 of the cloth 301 in the helmet, and traffic congestion information and the like are radiated from the electrostatic speaker 1 in the helmet.

(2) In the above embodiment, AM modulation is adopted as a carrier wave modulation method using an audio signal, but other modulation methods may be adopted. FIG. 7 is a diagram showing a configuration of a wireless audio transmission system employing FM (Frequency Modulation) modulation as a carrier wave modulation method. In this figure, the same parts as those shown in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  In the transmission apparatus 200A of the wireless audio transmission system, the transmission circuit 201A FM modulates a carrier wave, which is a pulse train having a predetermined frequency, with an audio signal, and causes a high-frequency current that is an FM modulated wave to flow through the transmission antenna 202. The carrier frequency is 20 MHz, for example. In this case, even if FM modulation of ± 10 kHz is performed by the audio signal, the deviation of the FM modulated wave from the carrier frequency is at most ± 0.05%, and there is no problem of influence on the magnetic field resonance system.

  As the modulation scheme of the transmission circuit 201A is changed to the FM modulation scheme, the demodulation circuit 8 is provided in the wireless speaker device 100A on the reception side. The demodulating circuit 8 performs FM demodulation of the AC voltage generated in the secondary coil 4B of the step-up transformer 4, generates an audio signal, and applies it to the conductive cloths 20U and 20L of the electrostatic speaker 1. Since the FM modulated wave given from the receiving antenna 2 to the primary coil 4A of the step-up transformer 4 has a constant amplitude, a DC voltage obtained by rectifying the FM modulated wave is a constant voltage. Therefore, the limiter 7 that was necessary when the AM modulation method was adopted is unnecessary. The AC voltage generated in the primary side coil 4A of the step-up transformer 4 is rectified to generate a DC voltage, and the DC voltage is generated at the midpoint of the diaphragm 10 of the electrostatic speaker 1 and the secondary side coil 4B of the step-up transformer 4. To give. In the example shown in FIG. 7, a known multistage voltage doubler rectifier circuit 9 is used as a rectifier circuit for generating the DC voltage.

  In this aspect, the same effect as the above embodiment can be obtained. In this aspect, it is necessary to use an active element for the demodulation circuit 8, and a power supply voltage for operating the active element is required. However, the demodulating circuit 8 may be a well-known small-scale circuit that performs FM demodulation, and can operate sufficiently by providing a DC voltage obtained from the multistage voltage doubler rectifier circuit 9 as a power supply voltage without providing a battery or the like. It is possible.

It is a figure which shows the structure of the wireless audio transmission system containing the wireless speaker apparatus 100 which is one Embodiment of this invention. It is a perspective view which shows the external appearance of the electrostatic speaker 1 in the same embodiment. It is a figure explaining the mounting method of each part of the wireless speaker apparatus 100 in the embodiment. It is a figure which shows the example of mounting to the jumper 300 of each part of the wireless speaker apparatus 100 in the embodiment. It is a figure explaining operation | movement as the whole wireless transmission system. It is a figure which shows the example of mounting to the helmet of each part of the wireless speaker apparatus 100 in the embodiment. It is a figure which shows the structure of the wireless audio transmission system containing 100 A of wireless speaker apparatuses which are other Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless speaker apparatus, 200 ... Transmission apparatus, 201, 201A ... Transmission circuit, 202 ... Transmission antenna, 2 ... Reception antenna, 202L, 2L ... Single turn coil, 202C, 2C ... Capacitor, 4 ... transformer, 4A ... primary coil, 4B ... secondary coil, 1 ... electrostatic speaker, 20U, 20L ... conductive cloth, 10 ... diaphragm, 30U, 30L ... elastic member 5 ... DC voltage generation circuit, 6 ... rectification circuit, 7 ... limiter, 8 ... demodulation circuit, 9 ... multi-stage voltage doubler rectification circuit.

Claims (3)

A receiving antenna;
An electrostatic speaker having a diaphragm and two electrodes sandwiching the diaphragm via an insulating and elastic member;
An alternating voltage generated in the receiving antenna is applied to the primary coil, and an alternating voltage generated in the secondary coil is applied to the two electrodes of the electrostatic speaker;
A DC voltage generating circuit that rectifies an AC voltage applied to a primary coil of the transformer to generate a DC voltage, and applies the DC voltage to a diaphragm of the electrostatic speaker and a midpoint of the secondary coil; Comprising
A wireless speaker device , wherein a signal obtained by modulating a carrier wave with an audio signal is received by the receiving antenna, and the transformer and the electrostatic speaker function as a low-pass filter that demodulates a received signal of the receiving antenna. . 2. The wireless device according to claim 1, wherein the reception antenna includes a loop-shaped coil and a capacitor interposed in the middle thereof, and constitutes a series resonance circuit having the same resonance frequency as the frequency of the carrier wave. Speaker device. The wireless speaker device according to claim 1, wherein each of the electrostatic speaker and the receiving antenna is in the form of a flexible cloth .

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