JP2014068255A - Radio communication device and electronic camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which audible noise having a frequency component of an audible range is generated when an electromagnetic wave emitted from a radio communication device that transmits in the form of a burst enters into an instrument through a cord or the like of an external microphone and a signal that is pseudo-envelope-detected by a voice amplifier circuit or the like mixes in a voice processing circuit.SOLUTION: To reduce audible noise while continuing radio communication, a reverse phase signal of the audible noise having a frequency component of an audible range is generated by a high frequency circuit of the own device by synchronizing with a transmission burst of a radio signal and added to an envelope-detected voice signal.

Description

  The present invention relates to a wireless communication apparatus and an electronic camera having a function for reducing audible noise caused by a high-frequency signal radiated in a burst manner.

  In devices that radiate high-frequency signals in bursts in digital wireless communication, such as TDMA and wireless LAN, audible noise caused by radio signals radiated in bursts is mixed into the audio processing circuits included in the devices and peripheral devices. It is known.

  As an example of measures against such noise in an electronic camera, there has been proposed a method of stopping generation of a carrier wave used in wireless communication during recording or recording (Patent Document 1).

  In addition, a method has been proposed in which a built-in antenna is provided in the vicinity of an external microphone to detect interference noise components and cancel each other by generating an electromotive force having a phase opposite to that of the interference noise components (Patent Document 2).

Japanese Patent No. 3807477 JP 2001-186041 A

  However, the solution disclosed in Patent Document 1 has a problem in that use cases are limited because wireless communication and recording or recording cannot be performed simultaneously. Further, with the solution disclosed in Patent Document 2, there is a problem that it is difficult to achieve temporal synchronization with bursty audible noise radiated from the device itself, and the influence from the outside by using an antenna. There is a problem that it is easy to receive. In addition, in general, a band rejection filter built in for noise removal has a problem that noise detected by envelope detection cannot be removed when an audio amplification circuit is attached to an external microphone.

  Therefore, the present invention realizes a technique for reducing audible noise without stopping wireless communication without using a dedicated built-in antenna or band filter.

  According to an aspect of the present invention, wireless communication means for transmitting a transmission burst via an antenna, voice input means for inputting a voice signal, amplification means for amplifying the input voice signal, and the voice input means The transmission burst component is mixed into the audio signal through the path by the path between the amplifier and the amplification means acting as an antenna, and the mixed transmission is performed by the amplification means acting as a detection circuit. A noise removing unit that detects an envelope signal of a burst component and removes noise generated when the envelope signal has an audible frequency component from the voice signal; A synchronization signal synchronized with the output of the burst is output to the noise removal unit, and the noise removal unit is synchronized with the synchronization signal received from the wireless communication unit, and the envelope signal Generates a cancellation signal of the phase, the radio communication apparatus characterized by removing the noise by adding said phase-killing signal to the audio signal output from said amplifying means.

  According to the present invention, the present invention reduces audible noise without stopping wireless communication without using a dedicated built-in antenna or bandpass filter.

The block diagram of the electronic camera provided with the radio | wireless communication function in embodiment. The detailed block diagram of a radio | wireless communication part and a noise removal part. (A) is the envelope signal of the transmission burst in IEEE802.11g, (B) is a figure which shows the spectrum of the transmission burst of (A). (A) is the cancellation signal for the envelope signal of FIG. 3 (A), and (B) is the envelope signal after adding the envelope signal of FIG. 3 (A) and the cancellation signal of FIG. 4 (A). Figure. The timing chart of each signal in a radio | wireless communication part and a noise removal part. (A) is the envelope signal after calculation produced by the time difference with a cancellation signal, (B) is a figure which shows the spectrum of the envelope signal after calculation. (A) is the envelope signal after the calculation when the amplitude is different in addition to the time difference from the cancellation signal, and (B) is a diagram showing the spectrum of the envelope signal after the calculation. The detailed block diagram of a radio | wireless communication part and a noise removal part. The timing chart of each signal in a radio | wireless communication part and a noise removal part.

  FIG. 1 is a block diagram of an electronic camera including a wireless communication apparatus according to an embodiment of the present invention. This is, for example, an electronic camera having a wireless communication function using a wireless LAN. The electronic camera body 10 includes an antenna 11 and a wireless communication unit 12.

  The audio input unit 19 includes a built-in microphone and a microphone input terminal connected to an external microphone. The audio processing unit 20 includes at least an amplifier 201 that inputs and amplifies an analog audio signal captured as an electrical signal by the audio input unit 19 through a path 191 and an AD converter 202 that converts the analog audio signal into a digital audio signal. The control unit 13 controls the operation of the entire electronic camera including the lens 14, the image processing unit 15, the operation unit 16, the display unit 17, the storage unit 18, and the like. For example, when a recording operation is performed via the operation unit 16, the control unit 13 associates the image data from the image processing unit 15 and the audio data from the audio processing unit 20 obtained by shooting as a file. Store in the storage unit 18. When a file transfer operation is performed via the operation unit 16, the control unit 13 uses the wireless communication function such as a wireless LAN to transfer the file stored in the storage unit 18 to the wireless communication unit 12 and the antenna 11. Can be transferred to an external device.

  By the way, if, for example, the recording / recording function is operated simultaneously during the transfer of such a file, there is a problem that burst noise is superimposed on the recorded voice. The process of generating this problem noise can be explained as follows. First, the path 191 between the microphone of the audio input unit 19 and the amplifier 201 of the audio processing unit 20 acts as an antenna for the transmission burst of the wireless LAN, so that at least a part of the transmission burst is electronic. Captured inside the camera. Next, when the captured transmission burst component passes through the amplifier 201, a transistor, a diode, or the like (not shown) that constitutes the amplifier 201 acts as a pseudo-detection circuit on the transmission burst component. The envelope signal of the burst component is detected. The envelope signal has an audible frequency component, and noise perceived by humans is generated. In particular, when an external microphone is used instead of a microphone built in the electronic camera, the length of the path 191 becomes long, and thus noise tends to appear prominently.

  As described below, the present embodiment provides a configuration that effectively removes or reduces such noise.

  The radio communication unit 12 and the noise removal unit 21 are shown in a detailed block diagram in FIG. The wireless communication unit 12 includes a wireless output unit 30 and a signal amplification unit 31. The radio output unit 30 outputs an RF radio signal, that is, a transmission burst, in accordance with a control signal from the control unit 13. The signal amplification unit 31 amplifies the transmission burst output from the wireless output unit 30 and supplies the amplified transmission burst to the antenna 11. Further, the radio output unit 30 outputs an enable signal that permits the operation of the signal amplifying unit 31 for each transmission burst. The signal amplifying unit 31 amplifies the radio signal (transmission burst) while the enable signal from the radio output unit 30 indicates, for example, HIGH.

  The noise removal unit 21 includes a signal generation unit 32 and a calculation unit 33. The signal generation unit 32 synchronizes with the signal amplification unit 31 using the enable signal of the signal amplification unit 31 as a synchronization signal. The computing unit 33 receives the output signal from the audio processing unit 20 and the output signal from the signal generating unit 32, and outputs a computation result.

  When the voice processing unit 20 operates during wireless communication, the signal generation unit 32 generates a cancellation signal having a phase opposite to the envelope signal of the transmission burst in synchronization with the signal amplification unit 31. The calculation unit 33 adds the cancellation signal generated by the signal generation unit 32 to the digital audio signal output from the audio processing unit 20, thereby reducing audible noise included in the spectrum of the envelope signal.

  In general, when a transmission burst of wireless communication is detected by envelope detection, the detection signal has a rectangular waveform. The rectangular wave of the detection signal has the same period as the burst period, and the pulse width is the same as the burst length.

  The human audible frequency ranges from about 20 Hz to about 20 kHz, and signals outside that range are not recognized as speech. Further, even if there is a frequency component in the audible range, if the amplitude is sufficiently small, it is not recognized as speech.

  Here, the noise component detected by the envelope processing by the voice processing unit 20 will be described using IEEE 802.11g, which is a wireless LAN standard, as an example. FIG. 3A is a diagram illustrating an example of an envelope signal of a transmission burst. For example, the burst length is 250 μs and the burst interval is 100 μs. FIG. 3B is a diagram showing an example of a spectrum on the frequency axis obtained by Fourier analysis of the envelope waveform shown in FIG.

  As can be seen from FIG. 3B, it can be seen that the detection signal has a number of large spectra in a wide band, starting from around 2857 Hz corresponding to the reciprocal of 350 μs. Since these frequency components fall in the audible range, they are perceived as audible noise when mixed in the audio signal.

  At this time, the cancellation signal generated by the signal generation unit 32 in synchronization with the signal amplification unit 31 is as shown in FIG. FIG. 4B shows a waveform obtained as a result of the arithmetic unit 33 adding the envelope signal of FIG. 3A and the canceling signal of FIG. As shown in FIG. 4B, the amplitude on the time axis is 0, and the spectrum on the frequency axis is naturally 0. Therefore, if the signal generation unit 32 is accurately synchronized with the signal amplification unit 31 and the amplitude of the cancellation signal is optimally controlled, audible noise can be reduced.

  As an example, FIG. 5 shows a timing chart of each signal having the configuration of FIG. In FIG. 5, (1) is an enable signal of the signal amplifying unit 31, (2) is an envelope signal of a transmission burst, (3) is an offset signal output from the signal generating unit 32, and (4) and (5) are arithmetic operations. The output signals of the unit 33 are respectively shown.

  The enable signal of the signal amplification unit 31 output from the wireless output unit 30 disappears before the wireless output unit 30 outputs the wireless signal so that the signal amplification unit 31 can amplify the transmission burst of the wireless signal without omission. In the meantime, allow time for enable time. The time margin of the enable signal at this time is often about 1 μs from the viewpoint of power consumption.

  Therefore, the enable signal is longer than the burst length of the radio signal by about 1 μs at the start and end of the operation of the signal amplifying unit 31. Similarly, the cancellation signal generated in synchronization with the enable signal is also increased by about 1 μs. That is, as a result of the addition by the calculation unit 33, burst signals may be generated at two locations in a section of about 1 μs where no radio signal exists as in (4).

  When the cancellation signal for the transmission burst shown in FIG. 3 becomes longer by 1 μs, the envelope signal after the calculation is shown in FIG. 6A, and the spectrum after the Fourier transform by the control unit 13 is shown in FIG. 6B. . In the audible range, it is reduced to about 1/50 in the vicinity of 2840 Hz where the maximum value is observed, and it is possible to reduce the audible range noise so that it cannot be recognized with a deviation of about 1 μs.

  Further, when the amplitude of the cancellation signal generated by the signal generation unit 32 is different from the amplitude of the noise component, it has a certain amplitude as shown in FIG. A burst signal remains. As an example, FIG. 7A shows the envelope signal after calculation and FIG. 7B shows the spectrum after Fourier transform when the cancellation signal is about one fifth smaller than the amplitude of the noise component. Also in this case, since the spectrum is about 1/5, audible noise can be reduced.

  In the present embodiment, in order to optimize the reduction of audible noise mixed through the audio processing unit 20, an audible noise detection unit 13a for detecting audible noise is provided in the control unit 13, as shown in FIG. . The audible noise detection unit 13a detects audible noise by performing Fourier analysis or the like on the audio signal received from the noise removal unit 21. By reflecting this detection result in the amplitude limit range in the signal generation unit 32, it is possible to optimize the reduction of audible noise.

  At this time, since the influence of the delay time until the wireless signal radiated from the antenna 11 enters the microphone is so small that it can be ignored, the phase shift of the signal at the time of calculation can also be ignored.

  FIG. 8 shows a modification of FIG. In FIG. 8, the same components as those in FIG. 2 are denoted by the same reference numerals. The difference from FIG. 2 is that a signal detection unit 34 is provided between the signal amplification unit 31 and the antenna 11. The signal detection unit 34 is configured to output a detection signal to the signal generation unit 32 of the noise removal unit 21 when a transmission burst of a radio signal is detected.

  When the voice processing unit 20 operates during wireless communication, the signal generation unit 32 uses the detection signal received from the signal detection unit 34 of the wireless communication unit 12 as a synchronization signal, and has a phase opposite to the transmission burst of the wireless signal. Generate an offset signal.

  As an example, FIG. 9 shows a timing chart of each signal having the configuration shown in FIG. 9, (1) is an envelope signal of a transmission burst, (2) is a detection signal output from the signal detection unit 34, (3) is an offset signal output from the signal generation unit 32, and (4) is a calculation unit 33. The output signals are respectively represented.

  The detection signal is synchronized with the transmission burst. Similarly, the cancellation signal generated in synchronization with the detection signal is also synchronized with the transmission burst. That is, audible noise can be reduced as a result of the addition by the calculation unit 33.

  Although the embodiment of the present invention has been described above, the above-described reduction of audible noise may be realized by digital calculation or analog calculation by an OP amplifier or the like.

  Further, the same effect can be obtained even when the output signal of the signal generation unit 32 is in phase with the output signal of the sound processing unit 20 and the calculation unit 33 performs subtraction.

  According to the embodiment described above, it is not necessary to use a dedicated built-in antenna or band filter required in the prior art. Further, according to the present embodiment, it is not necessary to stop wireless communication such as file transfer for recording and recording.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. In this case, the program and the storage medium storing the program constitute the present invention.

Claims (4)

Wireless communication means for transmitting a transmission burst via an antenna;
A voice input means for inputting a voice signal;
Amplifying means for amplifying the input audio signal;
The path between the voice input means and the amplification means acts as an antenna, so that the components of the transmission burst are mixed into the voice signal via the path, and the amplification means acts as a detection circuit. A noise removing unit that detects an envelope signal of the mixed component of the transmission burst and removes noise generated by the envelope signal having an audible frequency component from the voice signal;
Have
The wireless communication means outputs a synchronization signal synchronized with the output of the transmission burst to the noise removing means,
The noise removing unit generates a cancellation signal having a phase opposite to that of the envelope signal in synchronization with the synchronization signal received from the wireless communication unit, and adds the cancellation signal to the audio signal output from the amplification unit. The wireless communication apparatus is characterized by removing the noise. The wireless communication means includes a wireless output unit that outputs the transmission burst, and a signal amplification unit that amplifies the transmission burst output from the wireless output unit,
The wireless output unit is configured to output an enable signal that permits the operation of the signal amplification unit to the signal amplification unit and the noise removing unit,
The wireless communication apparatus according to claim 1, wherein the noise removing unit uses the enable signal received from the wireless output unit as the synchronization signal. The wireless communication means detects a transmission signal output from the wireless output unit, a signal amplification unit that amplifies the transmission burst output from the wireless output unit, and a transmission burst output from the signal amplification unit. And a signal detector that outputs to the noise removing means,
The wireless communication apparatus according to claim 1, wherein the noise removing unit uses the detection signal received from the signal detection unit as the synchronization signal.   An electronic camera comprising the wireless communication device according to claim 1.

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