JPH03154440A - Optical space digital voice signal transmitter - Google Patents

Abstract

PURPOSE:To avoid a time delay between a digital voice signal sent from a voice signal source and the regeneration of the voice signal by providing an analog waveform interpolation correction circuit correcting a transmission error. CONSTITUTION:When a digital voice signal sent from a CD, a DAT or a BS tuner, etc., being a voice signal source 32 is D/A-converted by a D/A converter 49, a transmission error is corrected without increasing the transmission speed by applying interpolation correction with an interpolation correction circuit 50. That is, the digital voice signal sent from a CD, a DAT or a BS tuner, etc., being the voice signal source 32 is subjected to digital voice modulation without error correction bits. Then the time delay is avoided, an optical element with a low frequency is employed and the optical space digital voice signal transmitter with a low low cost is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to optical space digital technology used for wireless audio transmission of digital audio such as compact discs (CDs), digital audio tapes (DAT), and satellite broadcast (BS) tuners. The present invention relates to an audio signal transmission device.

BACKGROUND OF THE INVENTION FIG. 2 shows the configuration of a conventional optical space digital audio signal transmission device. Conventionally, this type of optical space digital audio signal transmission device is roughly divided into two blocks: a transmitting section 1 and a receiving section 11.
The receiving section 11 is a block that modulates and transmits a digital audio signal such as T, etc., and the receiving section 11 receives the signal sent from the transmitting section 1 at a remote location, and demodulates the digital audio signal. The signal is converted into a digital-to-analog converter (D
The signal is sent to an amplifier with a built-in system converter. The DM converter performs digital-to-analog conversion, further amplifies the sound, and reproduces the sound through a speaker.

In FIG. 2, the audio signal source 2 is a CD or DAT.

It consists of a BS tuner and the like, and its signals are sent to a digital optical link 4 through an optical fiber 3, which is a transmission cable. This digital optical link 4 converts the optical signal into an electrical signal and inputs it to the transmitter 1. Transmitter 1
is a digital interface 7 converted into an electrical signal
A digital audio encoding circuit 5 adds an error correction code to a digital audio signal based on Ohmanoto and converts it into a new format, and modulates the digital audio signal of the new format with FSX etc. at a frequency of about 30 MHz to about csoMan. a digital audio signal modulation circuit 6 that converts the digital audio signal sent from the digital audio signal modulation circuit 6 into a near-infrared optical signal with a wavelength of approximately 9600 Angstroms, and transmits the signal to the receiving section. Optical conversion drive circuit 7
It is equipped with

The receiving section 11 has a PIN which is an optical-to-electrical conversion element that converts the near-infrared signal sent from the transmitting section 1 into an electrical signal.
A diode 12, an amplifier circuit 13 that amplifies the converted electrical signal by about 70 dB, a limiter amplifier 14 that adjusts the level of the amplified signal, and a digital audio signal demodulation circuit 15 that demodulates the signal and its output signal. A digital audio signal decoding circuit 16 that checks for a predetermined error correction, corrects it if it is incorrect, and reconverts it into a digital audio signal in a digital interface format, and a digital optical circuit that converts the digital audio signal from electricity to an optical signal. Consists of links.

The converted optical signal is sent through an optical fiber to an amplifier containing a digital-to-analog converter (commonly called a nine-way converter) 17 that converts the optical to electrical signal and then the digital signal to an analog signal. It looks like this. The zero-person converter 17 converts the electrical signal into an analog signal using a predetermined method. The converted analog signal is amplified and played through a speaker.

With this configuration, digital audio signals such as CD and DAT can be transmitted wirelessly.

Next, the operation of the above embodiment will be explained.

In FIG. 2, the output signal of an audio signal source 2 such as a CD, DAT, or BS tuner is a serially transmitted digital signal based on a digital audio interface format with sampling frequencies of 44.1, 48, and 32, respectively. The output signal is sent to a digital optical link 4 through an optical fiber 3. The digital optical link 4 converts the optical signal into an electrical signal and inputs it to the transmitter 1. The digital audio signal encoding circuit 6 of the transmitter 1 performs encoding for error correction.

For example, convert to another new format that adds a parity check pit. The next digital audio signal modulation circuit 6 converts the input electrical signal from approximately 30 MHz to 50 MHz.
FSK (free queue seed shift key ink) at the frequency of M-an.

The signal is subjected to modulation such as PSK (phase shift keying) and sent to the electro-optical conversion drive circuit 7. The electric-optical conversion drive circuit 7 converts the modulated electrical signal sent from the digital modulation circuit 6 into a near-infrared optical signal with a wavelength of approximately 9500 Angstroms, and sends the near-infrared signal to the receiving unit 11. and send. Of course, in order to extend the reach, it is necessary to send a large amount of current to the infrared LICD of the electro-optical conversion drive circuit 7 to increase the light emitting power of the infrared LID.

To briefly explain the above, the digital audio signal sent from a CD, DAT, etc. is encoded for error correction, converted to a digital audio signal in a format different from the input format, and is converted from approximately 30 MHz. This means that the electrical signal is modulated at a frequency of about 50 MHz, converted into an optical signal, and sent wirelessly to the receiver 11 as a digital audio signal.

Next, the receiving section will be explained. The receiving section 11 converts the received near-infrared signal from the transmitting section 1 into an electrical signal using a pin diode 12, which is an optical-to-electrical conversion element. Next, in the amplifier circuit 13, the converted minute electric signal is amplified by about 70 dB to make it into a signal with a voltage of several volts that is easy to handle. The level of the electrical signal sent from the amplifier circuit 13 is adjusted to a constant voltage by the limiter amplifier 14, and demodulation processing can be performed in the same way whether the signal is sent from a short distance or a signal sent from a long distance. ing. Furthermore, about 3
The digital audio signal modulated with carrier waves from 0M- to 60MH is demodulated, error correction is checked, and the sampling frequencies sent from the audio signal source 2, such as CtD, DAT, and BS tuner, are each 44. IK1,
48kHz.

Converts the digital audio signal into the same electrical signal as the serially transmitted digital signal based on the digital audio interface format of .32Kl (. The output signal is sent to a digital optical link that converts the electrical signal into an optical signal.The electrical signal is converted into an optical signal.The converted optical signal is passed through an optical fiber and the digital signal is converted into an analog signal. The signal is sent to an amplifier with a built-in digital-to-analog converter (usually called a 0-person converter) 17.The digital-to-analog converter 17 converts the signal into an analog signal using a predetermined method. The analog signal is amplified again and the audio is reproduced through the speaker.With this configuration, digital audio signals such as CDs and DATs can be transmitted wirelessly.

Problems to be Solved by the Invention However, in the conventional optical space digital audio signal transmission device described above, error correction encoding is performed on the digital audio signal sent from a CD, IMU, BS tuner, etc.
In order to perform wireless transmission by applying modulation such as FSX or PSK modulation to a new format digital audio signal that has added error correction bits and converting the signal to a transmission medium such as near-infrared rays, the carrier frequency is It was necessary to increase the height by adding the correction bits, and it was necessary to use high-performance infrared light emitting diodes and pin diodes that can be used even at high frequencies.

The addition of error correction bits creates the need for high-speed transmission, and short pulse widths of 1 bit H" and 'L" occur during optical fiber, optical digital optical links, and wireless transmission. As the jitter increases, the pulse widths of tt H++ and 'm' become even shorter, and transmission errors due to jitter are more likely to occur when converting digital audio signals to analog signals. Even if a correction bit is added, the effect of the correction bit is small, and there is a problem in that even if an attempt is made to correct an error, it cannot be corrected.

In addition, as the pulse width becomes shorter, there are 9 types of transmission distances such as optical fiber and digital optical link 2 coaxial cable as signal transmission media, the degree of jitter generation differs depending on the electrical performance, and the transmission error rate differs. However, there was a problem in that it was necessary to use high-performance parts for the parts mentioned above.

The present invention solves these conventional problems,
One type of transmission distance, such as optical fiber, used for transmission between the audio signal source and the transmitter, and transmission errors due to electrical characteristics, etc.
Compared to conventional digital audio transmission equipment, because the digital audio signal can be modulated at a lower frequency, low-cost optical conversion elements can be used, and the digital audio signal sent from the audio signal source and audio reproduction can be It is an object of the present invention to provide an excellent optical spatial digital audio signal transmission device that can eliminate time delays.

Means for Solving the Problems In order to achieve the above object, the present invention provides interpolation correction when performing digital-to-analog conversion of a digital audio signal sent from an audio signal source such as a CD, DAT, or BS tuner. The configuration is such that transmission errors can be corrected without increasing the transmission speed.

Operation Therefore, according to the invention, the audio signal source CjD
In order to perform digital audio modulation on digital audio signals sent from , DAT, BS tuners, etc. without error correction bits, it is possible to create an optical spatial digital audio signal transmission device without time delay, and using conventional optical elements. Compared to the conventional method, it is possible to use a lower frequency optical element, and a low-cost optical spatial digital audio signal transmission device can be provided.

Embodiment FIG. 1 shows the configuration of an optical space digital audio signal transmission apparatus according to an embodiment of the present invention. The optical space digital audio signal transmission device of this embodiment is roughly divided into two blocks: a transmitting section 31 and a receiving section 41. The transmitting section 31 transmits digital audio signals such as CD, DAT, and BS tuners. The receiving section 41 is a block that receives the signal sent from the transmitting section 31 at a remote location and demodulates the digital audio signal, and performs digital-to-analog conversion on the demodulated signal. The signal is then transmitted to the amplifier.

In FIG. 1, the audio signal source 32 is a CD or DAT.

It consists of a BS tuner, etc., and the output digital audio signal is transmitted through an optical fiber 3 transmission cable.
3 to the digital optical link 34. This digital optical link 34 converts the optical signal into an electrical signal and inputs it to the transmitter 31 .

The transmitter 31 connects the digital audio signal modulation circuit 38 that modulates the digital audio signal with FSX, PSK, etc. at a frequency of approximately 20M1-[z to approximately 40MHz, and converts the electrical signal sent from the digital audio signal modulation circuit 38 into approximately 40MHz. 96oO
It is provided with an electro-optical conversion drive circuit 39 that converts into a near-infrared light signal of Ongeström's wavelength and transmits it.

The receiving section 41 is an optical-to-electrical conversion element that converts the near-infrared signal sent from the transmitting section 31 into an electrical signal.
n diode 42 and the converted electrical signal to approximately 70 dB.
an amplifier circuit 43 that amplifies the level of the amplified signal; a limiter amplifier 44 that adjusts the level of the amplified signal; a digital audio signal demodulation circuit 45 that demodulates the signal; It is composed of an interpolation correction circuit 6o that performs interpolation correction.

With this configuration, digital audio signals such as CD and DAT can be wirelessly transmitted without waveform distortion due to transmission errors.

Next, the operation of the above embodiment will be explained.

In FIG. 1, the output signals of an audio signal source 32 such as a CD, a digital player, or a BS tuner have sampling frequencies of 44.1 KHz, 48 KHz, and 32 KHz, respectively.
It is a serially transmitted digital signal based on the I7Q digital audio interface format, and the output digital signal is sent to a digital optical link 34 through an optical fiber 33. Waveform distortion and the like occur depending on the length of the transmission distance of the optical fiber 33, the electrical performance of the digital optical link 34, and the electrical performance of the digital optical link 34, and the magnitude of the waveform distortion also differs. This digital optical link 34 converts the optical signal into a digital audio signal and inputs it to the transmitter 31 .

The input digital audio signal is converted into a waveform-shaped electrical signal by the digital audio signal modulation circuit of the transmitter 31 for about 2 days.
IFSX at frequencies from 0MHz to 4oMHz.

Alternatively, the signal is modulated by PSK or the like and sent to the electro-optical conversion drive circuit 39. The electro-optical conversion drive circuit 39 converts the modulated digital audio signal sent from the digital audio signal modulation circuit 38 into a near-infrared optical signal with a wavelength of approximately 95oO Angstrom, and sends it to the receiving unit 41. Transmits a digital audio signal as a near-infrared signal. of course,
In order to extend the reach, it is necessary to send a large amount of current to the infrared LED of the electro-optical conversion drive circuit 39 to increase the light emitting power of the infrared LED. To briefly explain the above, CD
, DAT, BS tuner, etc., directly from about 20 MHz to about 40 MHz.
This means that the digital audio signal is modulated at the frequency z, the electrical signal is converted into an optical signal, and the digital audio signal is transmitted wirelessly to the receiving unit 41.

Next, the receiving section 41 will be explained. The receiving section 41 receives the near-infrared signal sent from the transmitting section 31 with a pin diode 42, which is an optical-to-electrical conversion element, and converts the optical signal into an electrical signal. Next, in the amplifier circuit 43,
The minute electrical signal converted into an electrical signal is amplified by about 7 odB to make it into a signal with a voltage of several volts that is easy to handle.

The level of the electrical signal sent from the amplifier circuit 43 is adjusted to a constant voltage by the limiter amplifier 44, and demodulation processing of the digital audio signal is performed in the same way whether the signal is sent from a short distance or a long distance. It is now possible to do so. Furthermore, the carrier wave is removed from the digital audio signal modulated with a carrier wave of approximately 20 MHz to approximately 40 MHz through a digital audio signal demodulation circuit 46 that demodulates the electric signal, and the carrier wave is demodulated to the audio signal source 32, such as CD, DAT.
, the sampling frequencies sent from the BS tuner etc. are 44, IK)h, 48 KHz and 32, respectively.
KHzC17"';' Converts the serially transmitted digital signal based on the digital audio interface format into an electrical signal that is the same as the electrical signal. The converted digital audio signal contains jitter generated during transmission.

Here, if the digital audio signal is different from the electrical signal sent from the audio signal source 32, it means that a transmission error has occurred. For digital audio signals, most of the transmission errors are due to jitter caused by waveform distortion or due to light shielding. The converted digital audio signal is sent to a digital optical link that converts the electrical signal into an optical signal, which converts the electrical signal into an optical signal. The digital signal of the converted optical signal is converted into an analog signal through a D-muconmeter 49, transmission errors are corrected by an analog waveform interpolation correction circuit 50, and the signal is sent to an amplifier. With this configuration, it has become possible to wirelessly transmit digital audio signals such as CD, DAT, etc. without time delay, without time timing shift, at low cost, and with little influence from transmission errors.

Effects of the Invention As is clear from the above-mentioned embodiments, the present invention enables spatial transmission of digital audio sent from an audio signal source through an optical fiber or digital optical link by applying modulation such as FSX or PSK. Compared to adding error correction bits, it is possible to reduce the proportion of jitter in one pulse without shortening the pulse width.
Furthermore, it is possible to reduce the proportion of jitter in one pulse due to waveform distortion that occurs while passing through a digital optical link, and it is possible to reduce transmission errors due to increased transmission speed.

Furthermore, on the receiving side, it is desirable to reduce the proportion of jitter in one pulse due to waveform distortion that occurs during wireless transmission when reproducing a demodulated digital audio signal into an analog signal. Furthermore, by sending a digital audio signal with a reduced proportion of jitter in one pulse to the digital-to-analog converter, transmission errors that occur between the receiver and the digital-to-analog converter can be eliminated by the digital-to-analog converter. It is also possible to set the level to a level that can be corrected, and the transmission error υ can be reduced as much as possible.

In addition, by shortening the pulse width, optical fiber, which is a signal transmission medium, and digital optical links.

There are two types of transmission distances such as coaxial cables, and the degree of jitter generation differs depending on the electrical performance, resulting in a difference in transmission error rate.
The above-mentioned parts also have the effect of eliminating the need to use parts with good performance.

In the optical space digital audio signal transmission device of the present invention, a CD,
In order to perform wireless transmission by applying modulation such as FSK or PSK modulation to the digital audio signal sent from a DAT or BS tuner, etc., and converting the signal to a transmission medium such as near-infrared rays, the carrier frequency is changed from the conventional one. Since the value can be set to a slightly lower value than that of other transmission devices, it is no longer necessary to use high-performance infrared light emitting diodes and pin diodes.

In addition, since the number of error correction bits is reduced, the time required to convert from the conventional digital interface format to the new format, or from the new format to the digital interface format, is no longer required, and the signal sent from the audio signal source can be reproduced. The time difference has disappeared. Furthermore, the timing errors that conventionally occur when converting a digital signal can be avoided, and errors due to timing deviations can be made less likely to occur when converting a digital audio signal into an analog signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an optical space digital audio signal transmission device according to the present invention, and FIG. 2 is a block diagram showing a conventional optical space digital audio signal transmission device. 31...Transmission unit, 32...Audio signal source, 33...Optical fiber, 38...Digital audio signal modulation circuit, 41... Receiving section, 4
3...Amplification circuit, 45...Digital audio signal demodulation circuit, 49...0 person converter, 5o...
...Analog waveform interpolation correction circuit.

Claims (1)

[Claims] A transmitting section consisting of a digital signal modulation circuit and an electrical-to-optical conversion circuit, an optical-to-electrical conversion element, an amplifier, a digital signal demodulation circuit, and a digital-to-analog conversion circuit, and an analog waveform that corrects transmission errors at the final stage. An optical spatial digital audio signal transmission device comprising a receiving section having an interpolation correction circuit.