KR101210276B1 - Device and method for transmission of sound signal of frequency modulation form - Google Patents

Abstract

The present invention relates to an apparatus and method for transmitting sound to a human body using a human body as a communication channel, and more particularly, to modulate an audio signal using a frequency modulation method and apply the same to a human body. The present invention relates to a frequency modulation type of sound transmission technology capable of generating sound using a non-linear action generated. The present invention relates to a first modulation unit for frequency-modulating a signal transmitted from a sound source, and then converting a phase. And a second modulator for frequency-modulating after a time delay, and an ultrasonic transducer receiving the respective signals from the first and second modulators, converting the signals into ultrasonic signals, and transmitting the ultrasonic signals.

Acoustic, ultrasonic, frequency modulation, phase shift

Description

Frequency modulation sound transmission apparatus and method {DEVICE AND METHOD FOR TRANSMISSION OF SOUND SIGNAL OF FREQUENCY MODULATION FORM}

The present invention relates to an apparatus and method for transmitting sound to a human body using a human body as a communication channel, and more particularly, to modulate an audio signal using a frequency modulation method and apply the same to a human body. The present invention relates to a frequency modulation type sound transmission apparatus and method capable of generating sound using non-linear action generated.

The present invention is derived from a study conducted as part of the IT source technology development project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development. [Task management number: 2006-S-072-03, Task name: Human communication controller SoC].

Human body communication is a technology that transmits signals using the human body as a communication channel by using the principle that electricity can flow through the human body.

Among the human body communication, a technology for transmitting sound signals directly to a human body and then directly listening to the sound using an ear is called a human body audio transmission and reception technology. A conventional human body audio transmission and reception device transmits an acoustic signal to be transmitted from a human body. After modulating the signal to be transmitted through the human body, the receiving device installed in contact with the human ear demodulates it and converts it into an audio signal in the audible frequency band and provides it as a human-readable signal.

In addition, the present invention provides a human body acoustic transmission apparatus and method using a non-linear action of the human body in order to eliminate the hassle of having to further include a separate receiving device for receiving the acoustic signal transmitted through the human body.

Conventional human body sound transmission apparatus and method using a non-linear action of the human body is to convert the sound signal to be transmitted with a high frequency signal, that is, the amplitude modulation (Amplitude modulation) to convert the ultrasonic band signal of about 20kHz or more. The converted signal is converted into an ultrasonic signal through one or more ultrasonic conversion elements together with a high frequency signal used for mixing and then applied to the human body. The human body has a linear action, that is, a non-linear action, which is proportional to the magnitude of the input signal. Nonlinear effects on two or more signals can be modeled as the product of two signals. When the acoustic signal to be transmitted is called m (t), and the amplitude and frequency of the high frequency signal are A _c and f _c , respectively, the mixed signal with the high frequency signal, that is, the amplitude modulated signal and the high frequency signal are represented by Equation 1 And " (2) "

When two signals are converted into an ultrasonic signal through the ultrasonic transducer and then applied to the human body, each ultrasonic signal is transmitted through the user's body. The same signal is generated.

When Equation 3 is developed using the sine formula, Equation 4 is obtained.

The first term of the above equation is the signal of the ultrasonic band, which cannot be heard by the normal ear, but the second term is the signal of the acoustic band. Therefore, the user can listen to a desired sound signal without a separate receiver.

However, the conventional human body acoustic transmission method as described above has a disadvantage in that the implementation of the system has a simple advantage, but the adjustment of the frequency bandwidth is impossible.

In addition, a signal mixed with a high frequency signal has the same frequency bandwidth as that of an acoustic signal, and in view of the fact that an ordinary acoustic signal has a bandwidth of about 10 kHz, in order to convert the mixed signal into an ultrasonic signal, 10 kHz is applied to an ultrasonic element. Very wide bandwidth characteristics are required.

Therefore, for this wide bandwidth characteristic, the power consumption of the device must be large and the structure of the device must be complicated. In addition, the amplitude modulation method has a disadvantage in that sound quality is degraded because the modulated signal is very vulnerable to noise.

In order to solve the above problems, an object of the present invention is to apply a frequency modulation method to the human body acoustic communication method to adjust the frequency bandwidth of the transmission signal and to improve the noise characteristics of the frequency transmission method and To provide a way.

In order to achieve the above object, a frequency modulation type sound transmission apparatus according to a first embodiment of the present invention includes a first modulation unit for converting a phase after frequency-modulating a signal transmitted from a sound source, and transmitting the signal from the sound source. And a second modulator for frequency modulating the signal after a time delay, and an ultrasonic transducer receiving the respective signals from the first modulator and the second modulator, converting the signals into ultrasonic signals, and transmitting the ultrasonic signals.

In this case, the first modulator is a first frequency modulator for modulating the signal transmitted from the sound source in accordance with a frequency modulation scheme and a phase for converting the phase of the signal modulated by the first frequency modulator and then transmitted to the ultrasonic transducer It includes a converter.

On the other hand, the phase converter is characterized in that for converting the phase of the signal received from the first frequency modulator 90 °.

The second modulator may include a time delay for delaying a signal transmitted from the sound source and a second frequency modulator for modulating the delayed signal according to a frequency modulation scheme.

In addition, the ultrasound transducer may process the signal received from the first modulator and the signal received from the second modulator with separate devices.

In addition, the sound transmission method of the frequency modulation method according to the second embodiment of the present invention is a first step of generating a sound signal from the sound source, a second step of frequency-modulating the signal generated from the sound source, and the sound Three steps of frequency-modulating the signal generated from the source after a time delay, four steps of receiving and converting each of the phase-shifted signal and the frequency-modulated signal into an ultrasonic signal, and transmitting each of the converted signals through a human body. Steps.

In this case, the step 2 includes the step of modulating the signal transmitted from the sound source according to the frequency modulation method and the phase of the frequency-modulated signal.

On the other hand, the step 3 includes the step of time-delaying the signal transmitted from the sound source and the step of modulating the delayed signal according to the frequency modulation method.

In the fourth step, the phase-converted signal and the frequency-modulated signal may be converted sequentially or simultaneously.

As described above, the apparatus for transmitting a frequency modulated sound according to the present invention does not need to include a separate receiving device by using a nonlinear action of the human body, and can adjust the frequency bandwidth in various ways using the frequency modulated method. And, there is an effect capable of acoustic communication using a human body resistant to noise.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a diagram illustrating a configuration of an apparatus for transmitting a frequency modulation in accordance with the present invention.

The apparatus 100 for transmitting a frequency modulation according to the present invention includes a sound source 110, a first frequency modulator 120, a phase shifter 130, a time delay 140, a second frequency modulator 150, and the like. And ultrasonic transducer 160.

The sound source 110 generates a sound to be heard through the user's ear. The acoustic signal generated by the sound source 110 is frequency modulated through frequency modulation and then transmitted to the first frequency modulator 120 to convert the phase of the signal by 90 °.

In addition, the sound signal generated from the sound source 110 is transmitted to the time delay unit 140 for frequency modulation after the time delay.

The first frequency modulator 120 frequency modulates the sound signal transmitted from the sound source 110. The frequency modulation method is a modulation method in which the frequency of the high frequency signal is proportional to the amplitude of the sound signal, and thus the frequency bandwidth of the modulated signal can be adjusted.

The acoustic signal modulated by the first frequency modulator 120 is transmitted to the ultrasound transducer 160 after the phase shift 130 has a 90 ° phase change.

The time delay unit 140 delays the sound signal transmitted from the sound source 110 by a predetermined delay time t _d and then transmits the sound signal to the second frequency modulator 150.

Like the first frequency modulator 120, the second frequency modulator 150 frequency modulates an acoustic signal delayed by t _d and then transmits the acoustic signal to the ultrasonic transducer 160.

The ultrasound transducer 160 converts each signal received from the phase converter 130 and the second frequency modulator 150 into an ultrasound signal and then transmits the signal through the human body channel 170. Here, each of the signals received from the phase converter 130 and the second frequency modulator 150 may be ultrasonically changed by one ultrasonic transducer 160, as well as a separate ultrasonic transducer 160 for each signal. Signals can be processed separately.

The two signals transmitted through the human body are transmitted to the vicinity of the user's ear, and then a sound signal that can be heard by the non-linear action of the human body is generated. Can listen.

FIG. 2 is a view for explaining the change in the sound signal in each configuration of the sound transmission apparatus of the frequency modulation method according to the present invention with specific examples.

As shown, FIG. 2 illustrates a method of transmitting a frequency modulation sound through a process of changing in a frequency modulation sound transmitting device before the sound signal generated from the sound source 110 is transmitted to a human body.

First, a sound signal for a sound to be listened to from the sound source 110 is generated.

The generated acoustic signal is transmitted to each of the first frequency modulator 120 and the time delay 140.

The first frequency modulator 120 performs frequency modulation on the transmitted sound signal to generate a signal as shown in Equation 5 below (S220).

Where m (t) is the acoustic signal, A _C is the amplitude of the high frequency, f _C is the modulation frequency, k _f is the frequency sensitivity, and t is the current time. Can be defined. The frequency modulation scheme is a modulation scheme in which the frequency of the high frequency signal is proportional to the amplitude of the sound signal, thereby enabling the frequency bandwidth of the modulated signal by adjusting the frequency sensitivity k _f . In addition, the modulated signal is more resistant to noise, resulting in better sound quality than the amplitude modulation.

The signal of Equation 5 converted by the first frequency converter 120 is converted into a signal as shown in Equation 6 by changing the phase by 90 ° in the phase converter 130 (S230).

The signal of Equation 6 generated as described above is ultrasonically converted by the ultrasonic transducer 160 (S260).

In addition, the sound signal m (t) transmitted to the time delay unit 140 is delayed by the time t _d (S240).

The time-delayed signal is transmitted to the second frequency modulator 150 to be frequency-modulated and converted into a signal as shown in Equation 7 below. [S250] In Equation 7, t _d represents a preset delay time. m (tt _d ) represents the time delayed signal.

The signal modulated by the second frequency modulator 150 is transmitted to the ultrasonic transducer 160 and is ultrasonically converted (S260) and transmitted through the human body (S270).

When each of the signals ultrasonically converted by the ultrasonic transducer 160 is applied to the human body, the applied signal is transmitted through the human body and then converted by the nonlinear action of the human body near the user's ear as shown in Equation 8 below. .

Using the trigonometric formula, Equation 8 may be developed as in Equation 9 below.

The first term of Equation (9) is a signal of the ultrasonic band that the user cannot hear. On the other hand, when t _d is very small, the second term of Equation 9 may be approximated as shown in Equation 11 from the approximation of the differential term as shown in Equation 10 below.

By Taylor series expansion of the same sine function

In this case, when Equation 13 is satisfied, Equation 11 may be approximated as in Equation 14.

Therefore, the two signals applied to the human body are converted into the acoustic signal m (t) by the nonlinear action of the human body, and thus the user can listen to the acoustic signal m (t).

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those having ordinary knowledge in the technical field to which the present invention pertains. It is not limited by the drawings.

1 is a diagram illustrating a configuration of an apparatus for transmitting a frequency modulation in accordance with the present invention.

FIG. 2 is a view for explaining the change in the sound signal in each configuration of the sound transmission apparatus of the frequency modulation method according to the present invention with specific examples.

<Explanation of symbols for the main parts of the drawings>

110: sound source 120: first frequency modulator

130: phase shifter 140: time delay

150: second frequency modulator 160: ultrasonic transducer

Claims (9)

A first modulator for frequency-modulating a signal transmitted from a sound source and then converting a phase; A second modulator for frequency-modulating the signal transmitted from the sound source after a time delay; And And an ultrasonic transducer receiving each signal from the first modulator and the second modulator, converting the respective signals into ultrasonic signals, and applying the same to the human body. The method of claim 1, wherein the first modulator, A first frequency modulator for modulating a signal transmitted from the sound source according to a frequency modulation method; And And a phase shifter for converting a phase of the signal frequency-modulated by the first frequency modulator and transmitting the phase shift to the ultrasonic transducer. The method of claim 2, wherein the phase shifter, And a phase of the signal received from the first frequency modulator by 90 degrees. The method of claim 1, wherein the second modulator, A time delay for time delaying the signal transmitted from the sound source; And And a second frequency modulator for modulating the delayed signal according to a frequency modulation scheme. Generating a sound signal from a sound source; Modulating a signal generated from the sound source according to a frequency modulation method and converting a phase of the modulated signal; Modulating a signal generated from the sound source according to a frequency modulation method after a time delay; Receiving and converting each of the phase shifted signal and the frequency modulated signal after the time delay into an ultrasonic signal; And And applying each signal converted into the ultrasonic signal to a human body. 6. The method of claim 5, The phase-converted signal is a signal obtained by converting a phase of the modulated signal by 90 ° as shown in Equation 6 below, wherein m (t) represents the sound signal, and Ac is a high frequency amplitude. Fc denotes a frequency of a high frequency signal, t denotes a current time, and kf denotes a frequency sensitivity. <Equation 6>

6. The method of claim 5, The frequency-modulated signal after the time delay is a signal that is frequency-modulated after a time delay as shown in Equation 7 below, where t _d represents a time delay, t represents a current time, and m ( tt _d ) represents a time delayed signal, Ac represents a high frequency amplitude, fc represents a frequency of a high frequency signal, and kf represents a frequency sensitivity. <Equation 7>

6. The method of claim 5, The converting into the ultrasonic signal may include converting each of the phase shifted signal and the frequency modulated signal sequentially or simultaneously. 6. The method of claim 5, Each signal converted into the ultrasonic signal is converted to an acoustic signal by a nonlinear action of the human body when applied to the human body.

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