JPH08223119A - Transmission equipment - Google Patents

Abstract

PURPOSE: To resolve the problem that it is difficult to detect the carrier on the reception side with respect to data of regularity like silence data by subjecting the digital transmission data, which is scrambled by random codes, to phase shift modulation to transmit this data in the optical space transmission system using infrared rays. CONSTITUTION: A digital audio signal S1 from a digital audio (AV) apparatus 2 is transmitted and received by an audio signal transmission equipment 1 provided with a transmission system consisting of a transmitter 3 and an infrared emitter 4 and a reception system having the similar constitution. The transmission equipment 1 scrambles the signal S1 by required random codes and subjects it to phase shift modulation and transmits it. By this constitution where scrambled data is modulated as prescribed, even data of regularity like silence data is made artificially irregular to resolve the problem that it is difficult to detect the carrier on the reception side.

Description

Detailed Description of the Invention

[0001]

[Table of Contents] The present invention will be described in the following order. Field of Industrial Application Conventional Technology Problems to be Solved by the Invention Means for Solving the Problems (FIGS. 1 to 8) Action Example (1) Overall Configuration of Audio Signal Transmission Device (FIGS. 1 and 2) ( 2) Configuration of transmitter (Fig. 3) (3) Modulation circuit (Fig. 4) (4) Configuration of receiver (Fig. 5) (5) Demodulation circuit (Fig. 6) (6) Frequency check circuit (Fig. 7) ( 7) Data clock reproducing circuit (FIG. 8) (8) Operation and effect of the embodiment (9) Other embodiment Effect of the invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission device, and is suitable for application to a voice signal transmission device for transmitting a voice signal by an optical space transmission method using infrared rays.

[0003]

2. Description of the Related Art Conventionally, in this type of audio signal transmission device, the audio signal is frequency-modulated on the transmitting side, and a light emitting device which is an infrared light emitter is driven based on the resulting modulated signal. Then, an optical transmission signal composed of infrared rays is generated. This optical transmission signal is radiated toward the receiving side, propagates in space, and reaches the receiving side. On the receiving side, this optical transmission signal is received by an infrared receiver, where the optical transmission signal is converted into an electrical signal, and then demodulated to the original audio signal by a predetermined demodulating means. As a result, this kind of audio signal transmission device can collectively transmit desired audio signals to a large number of audio devices without requiring a transmission line, and is suitable for use in, for example, a wireless headphone or a speaker device.

[0004]

However, in the conventional voice signal transmission device, the voice signal is analog-modulated and transmitted, and there is a problem that the sound quality is easily deteriorated. As a method of solving this problem, by driving an infrared optical emitter with a digitally modulated audio signal,
A method of transmitting an audio signal by a digital method has been proposed.

However, in this type of audio signal transmission device,
Phase shift keying is used for digital modulation, and when regular data such as silence data is transmitted,
There is a problem that it becomes difficult for the receiving side to detect the carrier wave. In addition, in this type of audio signal transmission device, the optical transmission signal may be transmitted as if the transmission side had an input even though there was no input of the audio signal. May be demodulated.

Further, in this type of audio signal transmitting apparatus, the receiving side reproduces the transmission channel clock based on the optical transmission signal and outputs the reproduced audio signal on the basis of the transmission channel clock. Is designed to generate. In this case, the data clock is generated by a phase locked loop circuit (hereinafter referred to as a PLL circuit), but the lock phase of the PLL circuit changes at power-on or system initialization. The data clock may be disturbed and the system operation may be disturbed.
Further, in this type of audio signal transmission device, the receiving side performs error correction to restore the audio signal, but the restored audio signal may be output even when the error correction is impossible. For example, a speaker device or the like. When used for, there is a problem that an unpleasant sound is output and the listener feels uncomfortable.

The present invention has been made in view of the above points, and an object thereof is to propose a transmission apparatus capable of solving all the problems of the conventional art.

[0008]

In order to solve the above problems, according to the present invention, a modulation means for phase-shift-modulating a predetermined carrier wave based on input digital transmission data, and a modulation signal output from the modulation means. Driven by the infrared light emitting means for generating an optical transmission signal composed of infrared rays based on the modulation signal, infrared receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal Then, in the transmission device comprising the demodulation means for reproducing and outputting the digital transmission data, the modulation means scrambles the digital transmission data with a predetermined random code and phase-shift-modulates the scrambled digital transmission data. did.

Further, according to the present invention, the modulation means for phase-shift-modulating a predetermined carrier wave based on the input digital transmission data, and the modulation signal output from the modulation means are driven, and based on the modulation signal. Infrared light emitting means for generating an optical transmission signal composed of infrared rays, infrared light receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce and output digital transmission data. In the transmission device including the demodulation means, the demodulation means checks the frequency of the transmission clock at the time of the reproduced transmission or the frequency of the data clock at the time of outputting the reproduced digital transmission data based on the transmission clock.

Further, according to the present invention, the modulation means for phase-shift-modulating a predetermined carrier wave based on the input digital transmission data, and the modulation signal output from the modulation means are driven and are based on the modulation signal. Infrared light emitting means for generating an optical transmission signal composed of infrared rays, infrared light receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce and output digital transmission data. In the transmission device including the demodulation means, the modulation means operates with the transmission clock generated based on the data clock of the digital transmission data, and also initializes the phase locked loop circuit that generates the transmission clock to control the lock phase. Then, the demodulating means outputs the digital transmission data with the data clock reproduced based on the transmission clock at the time of transmission. In, and the Hue over Zuro poke loop circuit for reproducing data black poke to control the lock phase is initialized.

Further, according to the present invention, the modulation means for phase-shift-modulating a predetermined carrier wave based on the input digital transmission data, and the modulation signal output from the modulation means are driven, and based on the modulation signal. Infrared light emitting means for generating an optical transmission signal composed of infrared rays, infrared light receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce and output digital transmission data. In the transmission device including the demodulation means, the demodulation means corrects the error and reproduces the digital transmission data, and when the error cannot be corrected, the output operation of the reproduced digital transmission data is stopped.

[0012]

The digital transmission data is scrambled with a predetermined random code, and the scrambled digital transmission data is phase-shift-modulated, so that the regularity of the digital transmission data disappears in a pseudo manner. The carrier wave can be detected. In addition, by checking the frequency of the data clock when outputting the reproduced clock or the reproduced digital transmission data based on the transmitted clock during the reproduced transmission, the received optical transmission signal is It is possible to determine whether it is a thing.

Further, by initializing the phase locked loop circuit for generating the transmission clock to control the lock phase, and by initializing the phase locked loop circuit for reproducing the data clock to control the phase lock. It is possible to prevent the transmission clock and the data clock from scratching. Further, by stopping the output operation of the reproduced digital transmission data when the error cannot be corrected, the output of noisy digital transmission data can be avoided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

(1) Overall Structure of Audio Signal Transmission Device In FIG. 1, reference numeral 1 indicates an audio signal transmission device for transmitting a digital audio signal as a whole by optical space using infrared rays,
The digital audio signal S1 output from the digital audio device 2 is input to the transmitter 3 via a coaxial cable or an optical fiber cable. The transmitter 3 applies error correction parity, re-formatting, scrambling, phase shift keying, etc. to the digital audio signal S1, and obtains the resulting electric RF (Radio Frequency).
) Output the signal S2 to the infrared light emitter 4. The infrared light emitter 4 is a light emitter configured by an amplifier circuit, a light emitting diode (or laser diode), a lens, an optical filter, and the like, and becomes infrared by being driven by the electric RF signal S2. The optical transmission signal S3 is generated.

The optical transmission signal S3 is radiated into the free space, propagates in the free space, and reaches the receiving side. Then, this optical transmission signal S3 is received by an infrared detector (that is, a photodetector) 5 constituted by an optical filter, a lens, a photodiode (or a phototransistor), etc., and after being converted into an electric RF signal S4 here. , Receiver 6
Is output to The receiver 6 performs a process reverse to the process performed by the transmitter 3, demodulates the electric RF signal S4 to obtain a digital audio signal, and further performs a descrambling / reformatting inverse process on the digital audio signal. Error correction or the like is performed to restore the digital audio signal S5 having the same data structure as the digital audio signal S1. The digital audio signal S5 is output to the digital audio equipment 7 via a coaxial cable or an optical fiber cable.
Thus, the digital audio signal S1 output from the digital audio device 2 is transmitted to the digital audio device 7 via the audio signal transmission device 1.

In the case of this embodiment, in the audio signal transmission device 1, the optical transmission signal S3 is converted into EI as shown in FIG.
Of the frequency bands of the infrared transmission system assigned by AJ (Japan Electronic Machinery Manufacturers Association) CP-1205, 3 to 6 of the frequency bands assigned for high-quality audio transmission.
Send using [MHz].

(2) Structure of Transmitter The transmitter 3 has a structure as shown in FIG. 3, and the input circuit 8 receives the digital audio signal S1. The input circuit 8 outputs the clock signal S6 of the digital audio signal S1 including the audio data and the clock signal to the transmission channel clock generation circuit 9 and outputs the audio data S7 of the digital audio signal S1 to the parity adding circuit 1
Output to 0. The transmission channel clock generation circuit 9 is PL
An L circuit, a frequency dividing circuit, a frequency multiplying circuit, etc. are used to generate a transmission channel clock S8 to be used for transmission based on this clock signal S6, and the transmission channel clock S8 is transmitted to a transmission format generating circuit 11 and a modulation circuit. Circuit 1
Supply to 2.

The parity adding circuit 10 adds error correction parity to the voice data S7 and outputs the resulting voice data S9 to the transmission format generating circuit 11. The transmission format generating circuit 11 adds predetermined additional data and synchronization data to the audio data S9, rearranges the data into a structure suitable for infrared transmission, and re-formats the resulting transmission data S10.
Is output to the modulation circuit 12.

The modulation circuit 12 scrambles the transmission data S10 obtained from the transmission format generating circuit 11 and, based on the scrambled transmission data, phase-shift-modulates a carrier wave of a predetermined frequency (for example, 4-phase phase). QPSK (Quadrature Phase Shift Key)
ing) modulation), and the resulting electric RF signal S2 is output to the infrared optical emitter 4 (FIG. 1). Incidentally, the transmission format generating circuit 11 and the modulation circuit 12 operate based on the transmission channel clock S8 to perform the above-mentioned processing. Therefore, the data rate of the data handled by the transmission format generation circuit 11 and the modulation circuit 12 is based on the transmission channel clock S8.

(3) Modulation Circuit Here, the modulation circuit 12 has a structure as shown in FIG.
The transmission data S10 is input to the serial / parallel conversion circuit 13. The serial / parallel conversion circuit 13 parallel-converts the transmission data S10 into I data S11 and Q data S12, and outputs the I data S11 and Q data S12 to the exclusive OR circuit 14, respectively. The exclusive OR circuit 14 receives the random codes S13 and I supplied from the random sequence generation circuit 15.
By obtaining the exclusive OR with the data S11 and the Q data S12 respectively, the I data S11,
The Q data S12 is scrambled, and the resulting I data S14 and Q data S15 are respectively multiplied by the multiplication circuits 16 and 1.
Output to 7.

The multiplication circuit 16 multiplies the carrier wave f _C generated by the carrier wave generation circuit 18 by the I data S14, and outputs the resulting modulated signal S16 to the addition circuit 19. on the other hand,
The multiplication circuit 17 multiplies the carrier wave f _C whose π / 2 phase is shifted by the phase shifter 20 and the Q data S15, and outputs the resulting modulated signal S17 to the addition circuit 19. Thus, by adding the modulated signals S16 and S17 by the adder circuit 19, an electric RF signal S2 obtained by QPSK modulating the carrier wave f _C with the transmission data S10 is obtained.

In this case, the random sequence generating circuit 15 is composed of a shift register or the like, and the M sequence (Maximu) having the same bit rate as the I data S11 and the Q data S12.
A random code S13 of m length linear shift resister sequence code is generated. The synchronization signal S18 is input to the random sequence generation circuit 15, and the random sequence generation circuit 15 is initialized by the synchronization signal S18 and generates the random code S13 from a predetermined timing. By the way, on the receiving side, by similarly generating a random code and descrambling,
The transmission data S10 can be restored.

In this way, the modulation circuit 12 scrambles the transmission data S10 by multiplying the transmission data S10 by the random code S13 generated by the random sequence generation circuit 15, thereby pseudo-regulating the regularity of the transmission data S10. It is designed to reduce the bias of information points.

(4) Configuration of Receiver On the other hand, the receiver 6 has a configuration as shown in FIG. 5, and is adapted to input the electric RF signal S4 to the demodulation circuit 21. The demodulation circuit 21 is composed of a Costas loop circuit or the like, demodulates the QPSK-modulated electric RF signal S4, restores the scrambled signal on the transmitting side to obtain the reproduction data S19, and transmits the reproduction data S19. Output to the format regeneration circuit 22.

The transmission format reproducing circuit 22 performs the reverse of the processing performed by the transmission format generating circuit 11 on the transmitting side, and rearranges the synchronization data, additional data, voice data and error correction parity in the reproduction data S19. The audio data and the error correction parity of the data are returned to the error correction circuit 24 as reproduction data S20. Further, the transmission format reproducing circuit 22 generates a reset signal RST1 for each predetermined block of the reproduced data S19 based on the synchronous data and the like, and the reset signal RST1 is generated.
Is output to control the lock phase of the data clock reproduction circuit 26 described later.

The error correction circuit 24 corrects the error of the audio data in the reproduction data S20 (that is, the error occurred at the time of transmission) using the error correction parity, and outputs the resulting audio data S21 to the output circuit 25. . In this case, the error correction circuit 24 checks whether the error can be corrected,
If the error cannot be corrected, the output control signal S22 is output to stop the output operation of the output circuit 25. Incidentally, in the case of this embodiment, the Reed-Solomon code is used for the error correction parity, and in order to enable error detection, the correctable range r with respect to the distance d of the correction code is given by

[Equation 1] Set as shown in, and correct the error within this range.

The output circuit 25 is the data clock reproducing circuit 2
The audio data S21 is output as a digital audio signal S5 by using the data clock S23 reproduced in 6. In this case, the output circuit 25 includes the error correction circuit 2 as described above.
The output control signal S22 output from the signal No. 4 is input, and the output circuit 25 stops the output operation of the digital audio signal S5 in response to the output control signal S22. The output control signal S24 output from the frequency check circuit 27 is input to the output circuit 25, and the output circuit 25 also receives the digital audio signal S24 in response to the output control signal S24.
The output operation of 5 is stopped.

Here, the transmission channel clock reproducing circuit 23
Reproduces the transmission channel clock S25 based on the signal output from the demodulation circuit 21, and supplies the transmission channel clock S25 to the demodulation circuit 21 and the transmission format reproduction circuit 22 described above. That is, the demodulation circuit 21 and the transmission format reproduction circuit 22 described above operate on the basis of the transmission channel clock S25 and perform the above-described processing. Therefore, the data rate of the data handled by the demodulation circuit 21 and the transmission format reproduction circuit 22 is based on this transmission channel clock S25. By the way, since the transmission data S10 is scrambled on the transmission side as described above, the signal output from the demodulation circuit 21 is reduced in edge deficiency, which causes the transmission channel clock reproduction circuit 23 to fail in clock reproduction. It can be avoided.

The transmission channel clock reproducing circuit 23 also supplies the transmission channel clock S25 to the data clock reproducing circuit 26 and the frequency check circuit 27. The data clock reproducing circuit 26 is composed of a PLL circuit, a frequency dividing circuit, a frequency multiplying circuit, etc., and the transmission channel clock S
Based on 25, a data clock S23 used when outputting the digital audio signal S5 is generated. Further, the data clock reproducing circuit 26 includes a transmission format reproducing circuit 2
2, the reset signal RST1 output from the data clock reproduction circuit 26 is input to the data clock reproducing circuit 26.
Initialized by ST1, the lock phase is controlled.

The frequency check circuit 27 checks whether or not the frequency of the transmission channel clock S25 is a normal frequency. If the frequency is not a normal frequency, the output control signal S24 is output.
Is output to stop the output operation of the output circuit 25.

(5) Demodulation Circuit Here, the demodulation circuit 21 has a structure as shown in FIG.
The electric RF signal S4 is input to the demodulation unit 28. The demodulation unit 28 is composed of a carrier wave detection circuit or the like. The carrier wave detection circuit detects a carrier wave and demodulates the QPSK-modulated electric RF signal S4, resulting I data S26.
And Q data S27 are output to the exclusive OR circuit 29, respectively. In this case, since the regularity of the transmission data S10 is eliminated by scrambling the transmission data S10 on the transmitting side as described above, the carrier detection circuit can detect the carrier wave without causing pseudo lock or the like. it can.

The exclusive OR circuit 29 restores the scrambled data on the transmitting side by obtaining the exclusive OR of the random code S28 and the I data S26, Q data S27 supplied from the random sequence generation circuit 30, The resulting I data S29 and Q data S30 are output to the parallel / serial conversion circuit 31, respectively. The parallel / serial conversion circuit 31 serially converts the I data S29 and the Q data S30 to generate reproduction data S19.

In this case, the random sequence generation circuit 30 is composed of a shift register or the like, and has the same M as the random code S13 generated by the random sequence generation circuit 15 on the transmission side.
A sequence random code S28 is generated. Further, the synchronization signal S31 is input to the random sequence generation circuit 30,
The random sequence generation circuit 30 is initialized by this synchronization signal S31, and the random code S2 is started from a predetermined timing.
It is designed to generate 8. That is, the synchronization signal S
By initializing the random sequence generation circuit 30 with 31, the random code S28 is synchronized with the scrambled I data S26 and Q data S27, and the scrambled I data S26 and Q data S27 are thereby obtained. Put it back.

In this way, the demodulation circuit 21 multiplies the random code S28 generated by the random sequence generation circuit 30 to restore the scrambled data on the transmission side (that is, descramble) to the reproduced data S19. Is designed to get you.

(6) Frequency Check Circuit Here, the frequency check circuit 27 has a configuration as shown in FIG. 7, and the transmission channel clock S25 is counted by the counter 32.
It is designed to be entered into. The counter 32 counts the number of pulses of the transmission channel clock S25 and outputs the number of pulses to the comparison circuit 33. The clock signal S32 for reference is input to the counter 34,
The counter 34 counts the number of pulses of the clock signal S32 and outputs the number of pulses to the comparison circuit 33. Further, the counter 34 outputs the reset signal RST2 to the counter 32.
By outputting to the counter, it operates in synchronization with the counter 32.

The comparison circuit 33 counts the number of pulses of the transmission channel clock S25 obtained by the counter 32 and the counter 34.
The number of pulses of the transmission clock C25 is compared with the number of pulses of the transmission clock C25, and as a result, if the number of pulses of the transmission channel S25 is outside a predetermined error range with respect to the number of pulses of the clock signal S25, the transmission channel S25 Is not normal (that is, it is determined that the received optical transmission signal S3 is not a normal signal from the transmission side), the output control signal S24 is output, and the output operation of the output circuit 25 (FIG. 5) is performed. To stop.

In this way, the frequency check circuit 27
By comparing the pulse numbers of the reference clock signal S32 and the transmission channel clock S25,
It is determined whether the frequency of the transmission channel S25 is normal. When the frequency of the transmission channel clock S25 is not normal, the frequency check circuit 27 determines that the received optical transmission signal S3 is not a regular signal from the transmission side and outputs the signal from the output circuit 25 (FIG. 5). Stop the output operation.

(7) Data Clock Reproducing Circuit Here, the data clock reproducing circuit 26 is provided with a PLL circuit 35 as shown in FIG. 8, and the transmission channel clock S25 is connected to the counter 36 of the PLL circuit 35. It is designed to be entered into. The counter 36 is composed of a counter, a prescaler, etc., counts the number of pulses of the input transmission channel clock S25, divides the transmission channel clock S25 by a predetermined ratio, and outputs the resulting clock signal S33. Is output to the phase detector 37. The clock signal S34 output from the counter 38 is input to the phase detector 37, and the phase detector 37 compares the phase of this clock signal S34 with the phase of the clock signal S33 described above and determines the phase difference. The output voltage S35 is output to the loop filter 39.

The loop filter 39 removes the harmonic component of the output voltage S35 and outputs the resulting output voltage S36 to the voltage controlled oscillator circuit (VCO) 40. The voltage controlled oscillator circuit 40 operates on the basis of the output voltage S36 to generate a data clock S23 having a frequency such that the frequencies of the clock signals S33 and S34 are equal to each other, and the data clock S23 is output to the output circuit 25. (FIG. 5) and the counter 38. Like the counter 36, the counter 38 is configured by a counter, a prescaler, or the like, counts the number of pulses of the data clock S23, divides the data clock S23 by a predetermined ratio, and outputs the resulting clock signal S34. Is output to the phase detector 37 described above. In this way P
The LL circuit 35 receives the input transmission channel clock S25.
A data clock S23 having a predetermined frequency is generated based on the above.

In the case of this embodiment, the reset signal RST1 output from the transmission format reproducing circuit 22 is input to the counter 36, and the counter 36 is initialized by the reset signal RST1. This makes PL
The lock phase of the L circuit 35 is controlled, and the data clock S
It is possible to prevent the black rubbing of No. 23.

Here, it usually takes time for the PLL circuit to lock. This time is determined by the circuit characteristics of the PLL circuit. When this time is short, a jitter component (rubbing on the time axis) is generated in the clock generated by the PLL circuit.
When this jitter component increases, the sound quality deteriorates in the case of a digital audio signal, for example. On the contrary, when this time is long, the lock of the PLL circuit does not recover for a long time, and the optical transmission signal can be received again when the optical transmission signal is lost due to the interruption of the transmission path. Even if it happens, it takes time for the operation of the receiver to recover, and the sound cannot be reproduced during that time.

Therefore, in the case of this embodiment, the time constant of the loop filter 39 is controlled so that the lock time of the PLL circuit 35 is 1 ms or more and 500 ms or less. It has been experimentally confirmed that by setting the lock time to such a value, the sense of discomfort can be eliminated and the sound quality can be maintained in a good state.

(8) Operation and effects of the embodiment With the above-mentioned configuration, the transmitter side uses the transmitter 3 to add error correction parity, re-formatting, phase shift keying, etc. to the digital voice signal S1. Then, the infrared optical emitter 4 is driven by the electric RF signal S2 obtained as a result, and the optical transmission signal S3 corresponding to the digital audio signal S1 is obtained.
Is sent. On the receiving side, the infrared detector 5 receives the optical transmission signal S3 to reproduce the electric RF signal S4, and the receiver 6 performs a process reverse to that of the transmitter 3 so that the digital sound is converted from the electric RF signal S4. The signal S5 is demodulated.

In the case of this embodiment, the transmitter 3 scrambles the transmission data S10 based on the digital audio signal S1 to thereby obtain the transmission data S1.
The optical transmission signal S3 is obtained by phase-shift-modulating the carrier wave f _C with the scrambled transmission data by eliminating the regularity of 10.
Generate Normally, in the case of phase shift keying, when the data has regularity, the information points are biased, which makes it impossible for the receiving side to detect the carrier wave f _C and reproduces the transmission channel clock S25 used for transmission. become unable. However, in the case of this embodiment, since the transmission data S10 is scrambled on the transmission side to eliminate the regularity of the transmission data S10 as described above, the carrier wave f _C can be easily obtained on the reception side without a pseudo lock. In addition to being detected, the transmission channel clock S25 can be reproduced. That is, in the audio signal transmission device 1, even when the digital audio signal S1 having regularity such as silence data is input, the carrier wave f _C can be easily detected on the receiving side and the transmission channel clock S25 can be easily reproduced. .

Further, in the case of this embodiment, the frequency check circuit 27 is provided in the receiver 6, and the frequency check circuit 27 is provided.
Since the frequency of the transmission channel clock S25 is checked by, the digital voice signal S is transmitted on the transmission side.
When there is no input of 1 or when the signal is not actually transmitted, it is possible to easily determine whether or not the received signal is a regular signal. By stopping the output operation of the output circuit 25 when the received optical transmission signal S3 is not a regular signal, it is possible to avoid the erroneous output of the digital audio signal S5.

Further, in the case of this embodiment, the error correction circuit 24 provided on the receiving side performs error correction to reproduce the digital audio signal S5. At that time, the error correction circuit 24
When error correction becomes impossible due to data loss or noise, the output control signal S22 is output and the output operation of the output circuit 25 is stopped. Even if the error cannot be corrected by this,
The output of the noisy digital audio signal S5 can be avoided, and the listener can be prevented from feeling uncomfortable.

Further, in the case of this embodiment, the data clock reproducing circuit 26 is provided on the receiving side, and the data clock S23 used when outputting the digital audio signal S5 is reproduced by the data clock reproducing circuit 26. At this time, the reset signal RST1 is output from the transmission format reproducing circuit 22 at a predetermined timing to initialize the data clock reproducing circuit 26, so that the lock phase of the data clock reproducing circuit 26 can be controlled. It can prevent black scratches. This can prevent the system operation from being disturbed.

According to the above configuration, since the transmission data S10 is scrambled on the transmission side, the carrier wave f _C can be easily detected on the reception side even in the case of phase shift keying. In addition, the transmission channel S
The frequency check circuit 27 for checking the frequency of 25 is provided, and when the frequency check circuit 27 detects that the frequency of the transmission channel clock S25 is not normal, the output operation of the digital audio signal S5 is stopped. Therefore, the output of the incorrect digital audio signal S5 can be avoided.

Further, when the error cannot be corrected, the output circuit 25
By providing the error correction circuit 24 for stopping the output operation of the above, it is possible to avoid the output of the noisy digital audio signal S5 when the error correction is impossible. Also, a data clock reproducing circuit 26 for reproducing the data clock S23.
Is reset by the reset signal RST1, it is possible to prevent the clock rub of the data clock S23 from being disturbed, thereby avoiding the disturbance of the system operation.

(9) Other Embodiments In the above embodiments, the case where QPSK modulation, which is four-phase phase modulation, is used as the phase shift keying has been described, but the present invention is not limited to this, and the phase shift keying is not limited thereto. BPSK (Binary Phase Shift Keying), which is a two-phase phase modulation
) QAM (Quadrature) that is modulation or amplitude phase shift keying
Amplitude Modulation) modulation may be used.

In the above embodiment, the case where the scrambling is performed by the modulation circuit 12 and the descrambling is performed by the demodulation circuit 21 has been described, but the present invention is not limited to this, and the scrambling is generated by the transmission format. The same effect as in the above case can be obtained by performing the descrambling in the transmission format reproducing circuit 22 as well as the circuit 11.

Furthermore, in the above-mentioned embodiment, the case where the frequency of the transmission channel clock S25 is checked by the frequency check circuit 27 has been described, but the present invention is not limited to this, and the data check clock is used by the frequency check circuit. Even if the frequency of S23 is checked, the same effect as the above case can be obtained. This is because the data clock S23 is reproduced based on the transmission channel clock S25, and if the received signal is not a regular signal, the frequency of the data clock S23 will not be normal.

In the above embodiment, the case where the PLL circuit 35 of the data clock reproduction circuit 26 is initialized to control the lock phase has been described, but the present invention is not limited to this, and the transmission channel clock generation circuit. The PLL circuit of No. 9 may be initialized to control the lock phase.
As a result, the clock signal S6 of the digital audio signal S1
It is possible to prevent a clock rub when the transmission channel clock S8 is generated from.

Further, in the above-described embodiment, the lock time of the PLL circuit 35 of the data clock reproducing circuit 26 is set to 1.
Although the case where the time is set to [ms] or more and 500 [ms] or less has been described, the present invention is not limited to this, and the lock time of the PLL circuit of the transmission channel clock generation circuit 9 is also 1 [ms] or more,
It may be 500 [ms] or less.

In the above-described embodiment, the case where the transmission channel clock S8 is supplied to the transmission format generating circuit 11 and the modulation circuit 12 has been described, but the present invention is not limited to this, and the transmission channel clock S8 is parity. The parity adding circuit 10 may be supplied to the additional circuit 10 to operate based on the transmission channel clock S8.

Further, in the above-described embodiment, the case where the transmission channel clock S25 is supplied to the demodulation circuit 21 and the transmission format regeneration circuit 22 has been described, but the present invention is not limited to this, and the transmission channel clock S25 is erroneous. The error correction circuit 24 may be supplied to the correction circuit 24 and the error correction circuit 24 may be operated based on the transmission channel clock S25.

In the above embodiment, the transmitter 3 and the infrared light emitter 4 are separately provided, and the infrared detector 5 and the receiver 6 are separately provided.
The present invention is not limited to this, and the transmitter 3 is not limited to the infrared light emitter 4.
In addition to the above, the receiver 6 may be included in the infrared detector 5.

Further, in the above-mentioned embodiment, the case where the optical transmission signal S3 is transmitted in the frequency band of 3 to 6 [MHz] is described, but the present invention is not limited to this, and it may be transmitted in other frequency bands. You can

Further, in the above-mentioned embodiment, the case where the present invention is applied to the audio signal transmission device 1 for transmitting the digital audio signal S1 has been described, but the present invention is not limited to this, and is applied to a video signal transmission device for transmitting a video signal. The present invention can also be applied, and in short, it can be widely applied to a transmission device that transmits a predetermined signal by an infrared transmission method.

[0061]

As described above, according to the present invention, digital transmission data is scrambled with a predetermined random code,
By performing the phase shift modulation on the scrambled digital transmission data, the regularity of the digital transmission data disappears in a pseudo manner, whereby the carrier wave can be detected by the demodulation means. In addition, by checking the frequency of the data clock when outputting the reproduced clock or the reproduced digital transmission data based on the transmitted clock during the reproduced transmission, the received optical transmission signal is It is possible to determine whether it is a thing.

Further, the phase locked loop circuit for generating the transmission clock is initialized to control the lock phase, and the phase locked loop circuit for reproducing the data clock is initialized to control the lock phase. It is possible to prevent the transmission clock and the data clock from scratching. Further, by stopping the output operation of the reproduced digital transmission data when the error cannot be corrected, the output of noisy digital transmission data can be avoided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio signal transmission device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a frequency band of an optical transmission signal output from the audio signal transmission device according to the embodiment.

FIG. 3 is a block diagram showing a configuration of a transmitter.

FIG. 4 is a block diagram showing a configuration of a modulation circuit.

FIG. 5 is a block diagram showing a configuration of a receiver.

FIG. 6 is a block diagram showing a configuration of a demodulation circuit.

FIG. 7 is a block diagram showing a configuration of a frequency check circuit.

FIG. 8 is a block diagram showing a configuration of a PLL circuit of the data clock reproduction circuit.

[Explanation of symbols]

1 ... Audio signal transmission device, 2, 7 ... Digital audio equipment, 3 ... Transmitter, 4 ... Infrared optical emitter, 5
...... Infrared detector, 6 ... Receiver, 9 ... Transmission channel clock generation circuit, 10 ... Parity addition circuit, 1
1 ... Transmission format generating circuit, 12 ... Modulation circuit,
14, 29 ... Exclusive OR circuit, 15, 30
...... Random sequence generation circuit, 21 ・ ・ ・ Demodulation circuit, 22 ・ ・ ・
... transmission format reproduction circuit, 23 ... transmission channel clock reproduction circuit, 24 ... error correction circuit, 25 ... output circuit, 26 ... data clock reproduction circuit, 27 ... frequency check circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04B 10/04 10/06

Claims (23)

[Claims] Claim: What is claimed is: 1. Modulation means for phase-shift-modulating a predetermined carrier wave based on input digital transmission data, and infrared rays driven by the modulation signal output from the modulation means, based on the modulation signal. Infrared emitting means for generating an optical transmission signal, infrared receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce the digital transmission data. A transmission device comprising a demodulation means for outputting, wherein the modulation means scrambles the digital transmission data with a predetermined random code and phase-shift-modulates the scrambled digital transmission data. 2. The transmission device according to claim 1, wherein the digital transmission data is a digital audio signal or a digital video signal. 3. The modulating means operates with a transmission clock generated based on a data clock of the digital transmission data, and initializes a phase locked loop circuit for generating the transmission clock to control a lock phase. The transmission device according to claim 1 or 2, characterized in that. 4. The demodulating means outputs the digital transmission data with a data clock reproduced based on the transmission clock at the time of transmission, and initializes a phase locked loop circuit for reproducing the data clock. The transmission device according to claim 1, wherein the phase is controlled. 5. The demodulation means inspects the frequency of the transmission clock at the time of reproduction transmission or the frequency of the data clock at the time of outputting the digital transmission data reproduced based on the transmission clock. The transmission device according to claim 1 or claim 2. 6. The demodulating means reproduces the digital transmission data by performing error correction, and stops the output operation of the reproduced digital transmission data when the error correction cannot be performed. Alternatively, the transmission device according to claim 2. 7. Modulation means for phase-shift-modulating a predetermined carrier wave on the basis of input digital transmission data, and infrared rays driven by the modulation signal output from the modulation means, based on the modulation signal. Infrared emitting means for generating an optical transmission signal, infrared receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce the digital transmission data. In the transmission device comprising an output demodulation means, the demodulation means checks the frequency of the transmission clock during reproduction transmission or the frequency of the data clock when outputting the digital transmission data reproduced based on the transmission clock. A transmission device characterized by. 8. The transmission device according to claim 7, wherein the digital transmission data is a digital audio signal or a digital video signal. 9. The modulation means scrambles the digital transmission data by using a predetermined random code, and phase-shift-modulates the scrambled digital transmission data. The transmission device according to. 10. The modulating means operates with a transmission clock generated based on a data clock of the digital transmission data, and initializes a phase locked loop circuit for generating the transmission clock to control a lock phase. The transmission device according to claim 7 or 8, characterized in that. 11. The demodulating means outputs the digital transmission data with a data clock reproduced based on the transmission clock at the time of transmission, and initializes a phase locked loop circuit for reproducing the data clock. The transmission device according to claim 7 or 8, wherein the phase is controlled. 12. The demodulation means reproduces the digital transmission data by performing error correction, and stops the output operation of the reproduced digital transmission data when the error correction cannot be performed. Alternatively, the transmission device according to claim 8. 13. Modulation means for phase-shift-modulating a predetermined carrier wave based on input digital transmission data, and infrared rays driven by the modulation signal output from the modulation means, based on the modulation signal. Infrared emitting means for generating an optical transmission signal, infrared receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce the digital transmission data. In the transmission device comprising output demodulation means, the modulation means operates with the transmission clock generated based on the data clock of the digital transmission data, and initializes the phase locked loop circuit that generates the transmission clock. Control the lock phase, and the demodulation means uses the data clock reproduced based on the transmission clock at the time of transmission for the daisy A transmission device for controlling a lock phase by outputting a digital transmission data and initializing a phase locked loop circuit for reproducing the data clock. 14. The transmission device according to claim 13, wherein the digital transmission data is a digital audio signal or a digital video signal. 15. The modulation means scrambles the digital transmission data with a predetermined random code, and phase-shift-modulates the scrambled digital transmission data.
Alternatively, the transmission device according to claim 14. 16. The transmission device according to claim 13 or 14, wherein said demodulation means inspects the frequency of said reproduced transmission clock or said data clock. 17. The demodulating means reproduces the digital transmission data by error correction, and stops the output operation of the reproduced digital transmission data when the error correction is impossible. Alternatively, the transmission device according to claim 14. 18. A modulation means for phase-shift-modulating a predetermined carrier wave on the basis of input digital transmission data, and an infrared ray based on the modulation signal driven by the modulation signal output from the modulation means. Infrared emitting means for generating an optical transmission signal, infrared receiving means for receiving the optical transmission signal to obtain a reception signal corresponding to the modulation signal, and demodulating the reception signal to reproduce the digital transmission data. In the transmission device including the demodulation means for outputting, the demodulation means reproduces the digital transmission data by error correction, and when the error correction is impossible, stops the output operation of the reproduced digital transmission data. Characteristic transmission device. 19. The transmission device according to claim 18, wherein the digital transmission data is a digital audio signal or a digital video signal. 20. The modulation means scrambles the digital transmission data with a predetermined random code, and phase-shift-modulates the scrambled digital transmission data.
Alternatively, the transmission device according to claim 19. 21. The modulating means operates with a transmission clock generated based on a data clock of the digital transmission data, and initializes a phase locked loop circuit for generating the transmission clock to control a lock phase. The transmission device according to claim 18 or 19, characterized in that. 22. The demodulating means outputs the digital transmission data with a data clock reproduced based on the transmission clock at the time of transmission, and initializes a phase locked loop circuit for reproducing the data clock to lock the data. The transmission device according to claim 18 or 19, which controls a phase. 23. The demodulation means inspects the frequency of the transmission clock at the time of reproduction transmission or the frequency of the data clock at the time of outputting the digital transmission data reproduced based on the transmission clock. The transmission device according to claim 18 or claim 19.