JPH02305034A - Optical space digital signal transmission device - Google Patents

Abstract

PURPOSE:To eliminate the jitter caused by a waveform distortion by providing a digital waveform shaping circuit for extracting a fundamental clock from a digital sound signal sent from a sound signal source, and bringing the digital sound signal sent by its fundamental clock to waveform shaping again. CONSTITUTION:One of a transmission part 31 or a receiving part 41, or both of them are provided with a waveform shaping circuit 37 of a digital signal for extracting a fundamental clock component from the digital signal, and also, multiplying it and making a clock of a frequency of two folds of the fundamental clock, bringing the digital sound signal to waveform shaping and making it again by its extracted clock. That is, the waveform shaping is executed by a clock portion extracted from the digital sound signal and multiplied by the waveform shaping circuit 37. In such a way, the jitter can be decreased, and a transmission error can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to compact disc players (hereinafter referred to as CDs), digital audio tape recorders (hereinafter referred to as CDs), and digital audio tape recorders (hereinafter referred to as CDs).
The present invention relates to an optical space digital signal transmission device used for wireless transmission of digital audio signals such as DAT.

2. Description of the Related Art The prior art will be explained with reference to a block diagram of an optical spatial digital signal transmission device shown in FIG. According to FIG. 4, this type of spatial optical digital signal transmission device is composed of two blocks, a transmitting section 1 and a receiving section 11.
The receiver 11 receives the signal sent from the transmitter 1 at a remote location, demodulates the digital audio signal, and transmits the demodulated signal. is sent to an amplifier 18 having a built-in digital-to-analog converter. In that amplifier 18, the digital
Analog conversion is performed, the audio is further amplified, and the audio is reproduced by the speaker 19.

To explain the specific configuration of this conventional optical space digital signal transmission device, 2 is an audio signal source, and this audio signal source 2 is composed of a CD, DAT, BS tuner, etc., and the audio signal is output as an optical digital signal. The signal is 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 audio signal modulation circuit 5 that performs modulation such as frequency position modulation (hereinafter referred to as FSK) at a frequency of approximately 20 Mtlz to approximately 40 MHz, and an electrical signal sent from the digital audio signal modulation circuit 5 at approximately 9500 angstroms. It is equipped with an electric-optical conversion drive circuit 6 that converts into a near-infrared light signal having a wavelength of , and transmits the signal. The receiving section 11 is the transmitting section 1
The optical-to-electrical conversion element 12 consisting of a pin diode that converts the near-infrared light signal sent from the source into a digital signal, and the amplifier circuit 13 that amplifies the converted digital signal by about 70 dB, match the level of the amplified signal. It is composed of a limiter amplifier 14 and a digital audio signal demodulation circuit 15 which is an FSK demodulation circuit that demodulates the signal. 16 is a digital optical link that converts this demodulated signal into an optical signal, and the converted optical signal is passed through an optical fiber 17 to a digital-to-analog converter that converts the optical signal to an electrical signal, and furthermore, converts the digital signal to an analog signal. Amplifier 18 with a built-in (usually called a DAC)
The amplifier 18 converts the electric signal into an analog signal using a predetermined method, and the converted analog signal is amplified and reproduced through the speaker 19. With this configuration, digital audio signals such as CDs and DATs can be wirelessly transmitted.

Problems to be Solved by the Invention However, in the conventional optical space digital signal transmission device described above, the digital audio signal sent from a CD, DAT, etc. is directly modulated by FSK or frequency phase (PKK) modulation, etc. In order to perform wireless transmission by converting the near-infrared signal into a transmission medium such as near-infrared rays, the receiving side converts the near-infrared signal into an electrical signal, amplifies it, and demodulates it into a digital audio signal. Waveform distortion occurs, resulting in a distorted received waveform, which becomes a rectangular wave when shaped, but the width of the rectangular wave varies, causing jitter in the demodulated digital audio signal, and as a result, converting the digital audio signal into an analog signal. There is a problem in that a transmission error occurs during conversion into a signal, resulting in a different sound from the digital audio signal sent from the transmitter.

Furthermore, there is a problem in that the degree of occurrence of jitter varies depending on the transmission distance and electrical performance of the signal transmission medium, such as optical fiber, digital optical link, or pongee cable, resulting in a difference in transmission error rate.

The present invention solves these conventional problems,
The purpose is to provide an excellent optical spatial digital signal transmission device that minimizes errors in signal transmission due to one type of transmission distance such as optical fiber used for transmission between the audio signal source and the transmitter, electrical performance, etc. It is something to do.

Means for Solving the Problems In order to solve the above problems, the present invention extracts a basic clock component from a digital signal in either the transmitting section or the receiving section, or the other side, and then multiplies it to twice the basic clock component. A digital signal waveform shaping circuit is provided which generates a clock having a frequency of , and uses the extracted clock to waveform shape and recreate the digital audio signal.

Therefore, according to the present invention, jitter can be reduced by shaping the waveform of a clock component extracted from a digital audio signal and multiplied, thereby reducing transmission errors.

Embodiment An embodiment of the present invention will be explained with reference to FIGS. 1 and 2. FIG. 1 is a block diagram of an optical space digital signal transmission device, and FIG. 2 (a), (bl, (C), (dll; i
2 is a diagram illustrating waveforms in the circuit block of FIG. 1. FIG. According to FIGS. 1 and 2, two of the transmitter 31 and receiver 41
The transmission unit 31 is composed of a CD, DA block, and
The receiver 41 receives the signal sent from the transmitter 31 at a remote location, demodulates the digital audio signal, and transmits the demodulated signal. is transmitted to an amplifier 51 having a built-in digital-to-analog converter. The amplifier 51 performs digital-to-analog conversion, further amplifies it, and outputs it to the speaker 5.
2 to play audio.

To explain the specific configuration of this optical space digital signal transmission device which is an embodiment of the present invention, 32 is an audio signal source, and the audio signal source 32 is composed of a CD, a DAT, etc., and its output is A digital audio signal is sent to a digital optical link 34 through an optical fiber 33, which is a transmission cable. This digital optical link 34 converts the optical signal into a digital audio signal, which is an electrical signal, and inputs it to the transmitter 31 . The digital audio signal at this time is shown in Figure 2 (A
) contains jitter a', like signal a of ). The transmitter 31 converts the digital audio signal into a basic clock (for example, in the case of a CD, the sampling frequency is 44.1 KHz,
Data is 64 bits, basic clock is 2.822
41h) and further multiplies to obtain twice the frequency (
For example, in the case of a CD, the frequency is 5.6448 KHz), and the multiplication clock extraction circuit 35 generates the signal shown in FIG. 2(B) by shaping the waveform. (Delay circuit 36 that creates signal C of C1,
A digital waveform shaping circuit 37 that reshapes the waveform of the digital signal sent from the digital optical link 34 at the rising timing of the multiplied clock delayed by the delay circuit 36 and generates the digital signal d in FIG. 2(D) and its digital waveform. The digital audio signal output from the shaping circuit 37 is approximately 2Q)I
A digital audio signal modulation circuit 38 performs modulation of FSX, PSK, etc. at a frequency of about 40M1lz from Hz, and an electric signal sent from the digital audio signal modulation circuit 38 is
It is equipped with an electric-optical conversion drive circuit 39 that converts into a near-infrared light signal with a wavelength of 500 Angstroms and transmits it.

The receiving section 41 includes an optical-to-electrical conversion element 42 consisting of a pin diode that converts the near-infrared light signal sent from the transmitting section 31 into an electrical signal, and an optical-to-electrical conversion element 42 that converts the near-infrared light signal sent from the transmitting section 31 into an electrical signal, and converts the converted electrical signal into a
An amplifier circuit 43 that amplifies the amplified signal by about dB, a limiter amplifier 44 that adjusts the level of the amplified signal, a digital audio signal demodulation circuit 45 that demodulates the signal, and the output signal of the digital audio signal (FIG. 2 ta). (contains jitter like signal a) to the basic clock (for example, C
In the case of D, the sampling frequency is 44.1KHz, the data is 64 bits, and the basic clock is 2,8224K.
Hz) and further multiply it to obtain the double value in Figure 2 (b
2 (C) Signal C a delay circuit 47 that generates a signal such as;
A digital waveform in which the digital audio signal sent from the digital audio signal demodulation circuit 45 is reshaped into a digital signal as shown in d in FIG. 2(D) at the rising edge of the multiplied clock signal delayed by the delay circuit 47 It is composed of a shaping circuit 48. 49 is this digital waveform shaping circuit 48
This is a digital optical link that converts the digital audio signal coming out of the (
The electrical signal is sent to an amplifier 51 containing a built-in DAC (usually called a DAC), and the amplifier 51 converts the electrical signal into an analog signal using a predetermined method.The converted analog signal is amplified and sent to a speaker 52. will be played. With this configuration, digital audio signals such as CDs and DATs can be wirelessly transmitted. In the above embodiment, the waveform shaping circuits 37 and 48 are provided in each of the transmitter 31 and the receiver 41, but they may be provided in either one.

Further, FIG. 3 is a block diagram of an optical space digital signal transmission device, which is another embodiment, and the same parts as in the embodiment of FIG. 1 are given the same numbers, and the explanation will be omitted.
Reference numeral 53 denotes a bypass filter inserted and connected between the digital audio signal modulation circuit 38 and the electro-optical conversion drive circuit, and this bypass filter 53 prevents the internal noise of the transmitter 31 from being transmitted to the receiver 41. This system transmits only necessary digital audio signals without errors. Further, 54 is an amplifier circuit 43 of the receiving section 41 and a limiter amplifier 44.
This bypass filter 54 is inserted and connected in between, and this bypass filter 54 selects only the necessary band and passes it, thereby preventing the noise mixed in the received digital audio signal from being mixed into the subsequent circuit. It reproduces only the necessary digital audio signals.

In the embodiment shown in FIG. 3, a bypass filter is added to the embodiment shown in FIG. The filter may be inserted only in either the transmitting section or the receiving section.

Effects of the Invention As is clear from the above embodiments, the present invention extracts a basic clock from a digital audio signal sent from an audio signal source through an optical fiber or a digital optical link, and uses the basic clock to convert the sent digital audio signal. By providing a digital waveform shaping circuit that reshapes the waveform, it is possible to eliminate jitter due to waveform distortion that occurs while passing through optical fibers and digital optical links.In addition, on the receiving side, the clock is further reshaped from the demodulated digital audio signal. A digital waveform shaping circuit is installed that extracts the component and reshapes the demodulated digital audio signal using the extracted basic clock.By reshaping the waveform, jitter due to waveform distortion that occurs during wireless transmission is eliminated. This has the effect of eliminating transmission errors and reducing transmission errors as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the optical space digital signal transmission device of the present invention, FIG. 2 is a diagram explaining waveforms in each circuit of the device, and FIG. FIG. 4 is a block diagram of an optical space digital signal transmission device according to an embodiment, and FIG. 4 is a block diagram of a conventional optical space digital signal transmission device. 31...Transmission section, 34.49...Digital optical link, 37...Digital waveform shaping circuit, 38...Digital audio signal modulation circuit, 39.
...Electric-optical conversion drive circuit, 41... Receiving section, 42... Optical-electrical conversion element, 43...
...Amplification circuit, 45...Digital audio demodulation circuit, 48...Digital waveform shaping circuit, 51...
····Amplifier. Name of agent: Patent attorney Shigetaka Awano Haka12 Figure 2

Claims (6)

[Claims] (1) A waveform shaping circuit that receives a digital signal from a signal source through at least a digital optical link and shapes the waveform of the digital signal; a digital signal modulation circuit that modulates the waveform-shaped digital signal; a transmitter comprising an electric-to-optical conversion drive circuit that converts a modulated signal into an optical signal and transmits the same; an optical-to-electrical conversion element that converts at least the received optical signal into an electric signal; and amplifies the electric signal. An optical space digital signal transmission device comprising an amplifier circuit that demodulates the amplified electrical signal into a digital signal and inputs the digital signal demodulation circuit to an amplifier via a digital link. (2) Transmission consisting of at least a digital signal modulation circuit that inputs and modulates a digital signal from a signal source through a digital optical link, and an electro-optical conversion drive circuit that converts the modulated digital signal into an optical signal and transmits it. and a light source for converting at least the received optical signal into an electrical signal.
an electrical conversion element, an amplifier circuit that amplifies the electrical signal,
An optical receiver consisting of a digital signal modulation circuit that demodulates this amplified electrical signal into a digital signal, and a waveform shaping circuit that shapes the waveform of this digital signal and inputs it to an amplifier via a digital optical link. Spatial digital signal transmission equipment. (3) The optical space digital signal transmission device according to claim 1 or 2, further comprising a transmitter in which a bandpass filter is inserted at least before the electro-optical conversion drive circuit. (4) The optical space digital signal transmission device according to claim 1 or 2, further comprising a receiving section in which a bandpass filter is inserted at least after the optical-to-electrical conversion element. (5) at least a digital modulation circuit that receives a digital signal from a signal source through a digital optical link and modulates the digital signal; a bandpass filter that blocks noise mixed in the modulated signal; a transmitting section comprising an electric-to-optical conversion drive circuit that converts the signal that has passed through the pass filter into an optical signal and transmits the same; an optical-to-electrical conversion element that converts at least the received optical signal into an electric signal; and the electric signal. An optical spatial digital signal transmission device comprising an amplifier circuit that amplifies the electrical signal, and a receiving section that includes a digital signal demodulation circuit that demodulates the amplified electrical signal into a digital signal and inputs it to an amplifier via a digital optical link. (6) At least a digital modulation circuit that receives an electrical signal from a signal source through a digital optical link and modulates this digital signal, and an electrical-optical conversion drive circuit that converts this modulated signal into an optical signal and transmits it. a transmitting section,
an optical-to-electrical conversion element that converts at least the received optical signal into an electrical signal; a bandpass filter inserted after the optical-to-electrical conversion element to block noise mixed in the electrical signal; An optical spatial digital signal transmission device configured as a receiving section consisting of a digital signal demodulation circuit that demodulates an electrical signal into a digital signal and inputs it to an amplifier via a digital optical link.