JP2009130459A - Communication system for sound signal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a sound signal communicating/reproducing apparatus such as a wireless headphone without degrading reception performance or sound quality, and to reduce the number of components and reduce the cost. <P>SOLUTION: A communication system for sound signals includes a transmitter 1 for converting a modulated sound signal to an electromagnetic field signal and transmitting this signal, a receiver 3 for demodulating the electromagnetic field signal to the sound signal to output the demodulated sound signal, and a transmission medium 2 for transmitting the sound signal from the transmitter 1 to the receiver 3 via the electromagnetic field signal. The receiver 2 includes a speaker 33 having a voice coil 331 allowing the electromagnetic field signal and the demodulated sound signal to pass therethrough, a signal detection circuit 34 for detecting the electromagnetic field signal having passed the voice coil 331, and a demodulation circuit 31 for demodulating the signal detected by the signal detection circuit 34 into the sound signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an audio signal communication system that transmits and receives audio signals via a transmission medium such as a human body or space and outputs the audio signals.

  In a system for reproducing an audio signal, for example, an audio signal modulated by a method such as AM, FM, or FSK is transmitted as an electromagnetic wave signal from a transmitter and transmitted to a receiver via a transmission medium such as a human body or space. The receiver is demodulated into an audio signal, and the demodulated audio signal is reproduced as audio from an output means such as a speaker. In this system, a receiver includes a signal detection circuit that detects a modulated audio signal, a demodulation circuit that demodulates the detected audio signal, an amplification circuit that amplifies the demodulated audio signal, and a speaker that outputs audio. And a voice coil that drives the speaker.

In such a system, a resonant circuit combining an inductor L and a capacitor C is often used as an FM detector (Patent Document 1). In addition, technology for transmitting audio signals by applying communication technology via the human body has been developed (Patent Document 2).
JP-A-61-53802 JP 2006-303736 A

  For example, when wireless headphones, particularly small headphones embedded in ears, are made wireless, it is necessary to reduce the number of components and reduce the size of individual components. However, if the inductor coil of the FM detector and the voice coil of the speaker are made smaller, the inductance value becomes smaller. As a result, the reception performance is deteriorated in the detection coil, and the sound quality is deteriorated in the voice coil. Components with a large inductance value play an important role in performance and increase in volume, but they are unavoidably used in order to prevent performance degradation. Thus, it is difficult to reduce the size of a communication system mounted on wireless headphones or the like.

  The present invention has been made in view of the above points, and can reduce the size of an audio signal communication / playback device such as a wireless headphone without deteriorating reception performance and sound quality, and can reduce the number of components and cost. It is an object to provide a communication system for audio signals that can be reduced.

  The audio signal communication system according to the present invention includes a transmitter that modulates an audio signal, converts the signal into an electromagnetic field signal, and transmits the demodulated signal. The receiver demodulates the audio signal from the electromagnetic field signal and outputs the demodulated audio signal. And a transmission medium for transmitting the audio signal from the transmitter to the receiver via the electromagnetic field signal, wherein the receiver passes the electromagnetic field signal and the demodulated audio signal. Output means having a voice coil, a signal detection circuit for detecting the electromagnetic field signal that has passed through the voice coil, and a demodulation circuit for demodulating the signal detected by the signal detection circuit into the voice signal. It is characterized by.

  According to this configuration, since at least a part of the inductor in the signal detection circuit in the receiver can be supplemented by the inductance of the voice coil, the apparatus can be reduced in size. In this case, since it is not necessary to reduce the inductance values necessary for the signal detection circuit and the voice coil, it is possible to achieve downsizing without degrading performance.

  In the communication system for audio signals of the present invention, it is preferable that an LC resonance circuit is formed by the voice coil and a capacitor in the detection circuit. In the audio signal communication system according to the present invention, the signal detection circuit includes at least one inductor and a capacitor, and the at least one inductor, the capacitor, and the voice coil form an LC resonance circuit. Is preferred. According to these configurations, the number of parts can be reduced without reducing the performance, and the size and cost can be reduced.

  In the audio signal communication system according to the present invention, it is preferable that the receiver includes a low-pass filter or a band-pass filter that removes a high-frequency component from the demodulated audio signal. According to this configuration, the demodulated high-frequency signal and the audio signal can be reliably separated, and the influence on the sound quality and the like can be more reliably suppressed.

  In the audio signal communication system of the present invention, it is preferable that the receiver includes a high-pass filter or a band-pass filter connected to a subsequent stage of the voice coil. According to this configuration, it is possible to reliably separate the high-frequency signal and the audio signal before demodulation, and it is possible to more reliably suppress the influence on the sound quality and the like.

  An audio signal communication system according to the present invention includes a transmitter that modulates an audio signal, converts the signal into an electromagnetic field, and transmits the signal. The electromagnetic signal is received, demodulated into the audio signal, and the demodulated audio signal is output. A receiver and a transmission medium for transmitting the audio signal from the transmitter to the receiver via the electromagnetic field signal, the receiver receiving the electromagnetic field signal and the demodulated audio signal. Since it has an output means having a voice coil to pass, a signal detection circuit for detecting an electromagnetic field that has passed through the voice coil, and a demodulation circuit for demodulating the signal detected by the signal detection circuit into the audio signal, An apparatus for communicating / reproducing audio signals such as wireless headphones can be reduced in size without deteriorating reception performance and sound quality, and the number of parts can be reduced and the cost can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an audio signal communication system according to an embodiment of the present invention. The communication system for audio signals shown in FIG. 1 includes a transmitter 1 that modulates an audio signal, converts it into an electromagnetic field (electromagnetic wave) signal, and transmits it, and a human body or space that transmits the audio signal through the electromagnetic field signal. The transmission medium 2 and the receiver 3 that detects an electromagnetic field signal via the transmission medium 2, demodulates the electromagnetic field signal into an audio signal, and outputs the demodulated audio signal.

  The receiver 3 includes a speaker 33 (output means) having a voice coil 331 that allows the received electromagnetic field signal and demodulated sound signal to pass through, a signal detection circuit 34 that detects the electromagnetic field signal that has passed through the voice coil 331, and It has a demodulation circuit 31 that demodulates the signal detected by the signal detection circuit 34 into an audio signal, and an audio amplification circuit 32 that amplifies the demodulated audio signal.

  In the receiver 3 shown in FIG. 2, a voice coil 331 for the speaker 33 is interposed between the antenna 35 and the signal detection circuit 34, and the inductance of the voice coil 331 is used as one LC resonance circuit of the signal detection circuit 34. We use as department. The signal detection circuit 34 includes a capacitor 37 and an inductor 332 that form a part of the LC resonance circuit. The voice coil 331, the inductor 332, and the capacitor 37 constitute an LC resonance circuit. In such a configuration, when the carrier frequency of the received electromagnetic field signal is 10 MHz, L is preferably about 10 μH as a realistic value from a combination of L and C components. On the other hand, the voice coil 331 is about 5 μH to 10 μH in the case of headphones inserted into the ear. For this reason, for example, when the inductance of the voice coil 331 is 5 μH, the inductance of the inductor 332 in the signal detection circuit 34 is set to 5 μH. Then, the sum of the inductances of the voice coil 331 and the inductor 332 becomes 10 μH, and an inductance value (10 μH) necessary for the LC resonance circuit can be achieved. Further, since the inductor can be reduced in size as the inductance becomes smaller, the inductor 332 can be used in a smaller size than the conventional one, and the receiver 3 can be reduced in size. The antenna 35 may be a receiving electrode for human body communication.

  An operation in the case of performing communication in the audio signal communication system having the above configuration will be described. Here, a case where the communication system is a wireless headphone system will be described.

  First, in the transmitter 1 which is an audio signal source, for example, an audio signal (20 kHz or less) is modulated with a carrier wave having a frequency (several hundred kHz to several tens of MHz) at which the human body exhibits conductivity to obtain a modulated signal. This modulated signal is amplified and converted into a voltage change, thereby becoming an electromagnetic field signal corresponding to the modulated signal. This electromagnetic field signal is applied to the human body that is the transmission medium 2. There is no particular limitation on the modulation method in the transmitter 1.

  The electromagnetic field signal applied to the human body is received by the antenna 35 (or the reception electrode for human body communication) of the receiver 3. The electromagnetic field signal (high frequency signal) applied to the antenna 35 passes through the voice coil 331 of the speaker 33. At this time, the signal flowing through the voice coil 331 is an audio signal amplified by the audio amplifier circuit 32 and a received high-frequency signal, as shown in FIG. Here, for the audio signal, a current of several mA or more flows through the voice coil, and for the high-frequency signal, a minute current of about several μA flows. At this time, the current that flows due to the passage of the high-frequency signal is much smaller than the current that flows due to the passage of the audio signal, so the high-frequency signal has little effect on the driving of the speaker 33 by the voice coil 331. In FIG. 5, the signal intensity on the vertical axis is normalized with the peak of each signal as 100.

  Only a high-frequency signal is detected from the current flowing through the voice coil 331 by the LC resonance circuit including the voice coil 331, the inductor 332, and the capacitor 37. The high frequency signal is amplified by the amplifier circuit 40 in the signal detection circuit 34 and sent to the demodulator circuit 31. The demodulator circuit 31 demodulates using the carrier wave used in the transmitter 1 to obtain an audio signal. The audio signal is amplified by the audio amplifying circuit 32 and then sent to the voice coil 331 of the speaker 33, so that the speaker 33 is driven and output as audio.

  When the voice coil 331 has an inductance value necessary for the LC resonance circuit, the voice coil 331 can also be used as L of the LC parallel resonance circuit as shown in FIG. That is, when the carrier frequency of the received electromagnetic field signal is 10 MHz and the inductance of the voice coil 331 is 10 μH, the inductor for the LC resonance circuit is eliminated from the signal detection circuit 34, and the capacitor 37 and the voice coil 331 perform LC parallel. A resonant circuit can also be configured. As a result, the device can be further downsized. The capacitor 36 is introduced to couple the antenna 35 or the reception electrode for electric field communication and the voice coil at high frequency and insulate them in terms of DC.

  In this embodiment, only a high-frequency signal is detected from the current flowing through the voice coil 331 by the LC resonance circuit including the voice coil 331 and the capacitor 37. The high frequency signal is amplified by the amplifier circuit 40 in the signal detection circuit 34 and sent to the demodulator circuit 31. The demodulator circuit 31 demodulates using the carrier wave used in the transmitter 1 to obtain an audio signal. The audio signal is amplified by the audio amplifying circuit 32 and then sent to the voice coil 331 of the speaker 33, so that the speaker 33 is driven and output as audio.

  Here, if there is a possibility that the voice amplification circuit 32 may be affected by the addition of an electromagnetic field signal (high frequency signal) before demodulation to the voice coil 331, as shown in FIG. It is preferable to provide a low pass filter 38 or a band pass filter between the coils 331. Thereby, an extra high frequency component can be removed from the audio signal before demodulation. In this case, the inductance of the voice coil 331 can be a part of the filter. Thereby, the inductor at the time of comprising a filter can be reduced in size or eliminated, and the performance can be improved without increasing the size of the apparatus.

  Further, since the audio signal supplied to the voice coil 331 is extremely larger than the electromagnetic field signal, the audio signal may adversely affect the signal detection circuit 34. In this case, as shown in FIG. 4, it is preferable to provide a high-pass filter 39 or a band-pass filter downstream of the voice coil 331. Even in this case, the inductance of the voice coil 331 can be a part of the filter. Thereby, the inductor at the time of comprising a filter can be reduced in size or eliminated, and the performance can be improved without increasing the size of the apparatus.

  As described above, in the audio signal communication system according to the present invention, at least a part of the inductor in the signal detection circuit 34 in the receiver 3 can be supplemented by the inductance of the voice coil 331, or the inductor can also be used as the voice coil. Therefore, the receiver 3 can be downsized. In this case, since the inductance values necessary for the signal detection circuit 34 and the voice coil 331 can be obtained, the size can be reduced without degrading the performance.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, in the above embodiment, the case where the signal before demodulation passing through the voice coil is a signal obtained by modulating a voice signal by human body communication is described, but the present invention is not limited to this, and the voice coil is The present invention can also be applied to a case where a signal before demodulation that passes through is a radio broadcast signal or a TV sound broadcast signal. The circuit configuration, the number of parts, numerical values, and the like in the above embodiment are merely examples, and the present invention is not limited thereto and can be implemented with appropriate modifications. Other modifications can be made without departing from the scope of the present invention.

  The present invention can be applied to various communication systems using an inductor in a signal detection circuit of a receiver.

It is a schematic block diagram which shows the communication system for audio | voice signals which concerns on embodiment of this invention. It is a figure which shows the receiver of the communication system for audio | voice signals shown in FIG. It is a figure which shows the other example of the receiver of the communication system for audio | voice signals shown in FIG. It is a figure which shows the other example of the receiver of the communication system for audio | voice signals shown in FIG. It is a figure which shows the relationship between a frequency and signal strength. It is a figure which shows the relationship between a frequency and output intensity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Transmission medium 3 Receiver 31 Demodulator circuit 32 Audio amplifier circuit 33 Speaker 34 Signal detection circuit 35 Antenna 36, 37 Capacitor 38 Low pass filter 39 High pass filter 40 Amplifier circuit

Claims (5)

  A transmitter that modulates and converts an audio signal into an electromagnetic field signal and transmits; a receiver that demodulates the audio signal from the electromagnetic field signal and outputs a demodulated audio signal; and the electromagnetic field signal through the electromagnetic field signal A transmission medium for transmitting an audio signal from the transmitter to the receiver, wherein the receiver has a voice coil for passing the electromagnetic field signal and the demodulated audio signal, and the voice An audio signal communication system comprising: a signal detection circuit that detects the electromagnetic field signal that has passed through the coil; and a demodulation circuit that demodulates the signal detected by the signal detection circuit into the audio signal.   2. An audio signal communication system according to claim 1, wherein an LC resonance circuit is formed by the voice coil and a capacitor in the signal detection circuit.   The voice signal communication according to claim 1, wherein the signal detection circuit includes at least one inductor and a capacitor, and an LC resonance circuit is formed by the at least one inductor, the capacitor, and the voice coil. system.   The audio signal communication system according to any one of claims 1 to 3, wherein the receiver includes a low-pass filter or a band-pass filter that removes a high-frequency component from the demodulated audio signal.   5. The audio signal communication system according to claim 1, wherein the receiver includes a high-pass filter or a band-pass filter connected to a subsequent stage of the voice coil. 6.

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