JPH06276158A - Optical space transmitting device - Google Patents

Abstract

PURPOSE:To permit the respective kinds of balance of voice quality with noise and sensitivity at the time of a stereo voice signal to be satisfactory and to enhance conversion efficiency and reception sensitivity by converting a voice signal into an optical signal in a QPSK-modulated state so as to execute optical space transmission. CONSTITUTION:In a transmission system 31, an intermediate frequency signal adding a video signal and a voice subcarrier signal which is made into QPSK are supplied from a BS tuner 3. Then, the QPSK-modulated voice subcarrier signal from BPF 33 is impressed on the parallel circuit of a proper number of infrared ray LEDs 35 and a resistor. Therefore, the voice signal is converted into the optical signal in the QPSK-modulated state and optical space transmission is executed. In the reception system 32, the QPSK-modulated voice subcarrier from the connection center point of a photodiode 36 and the resistor 37 is supplied to a demodulator (four phase PSK demodulation) 40 with BPF 39 so as to be QPSK-demodulated. Then, a digital stereo voice signal is obtained by a decoder (PCM demodulation).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical space transmission device for transmitting an optical signal of a signal related to a voice signal obtained from a BS tuner.

[0002]

2. Description of the Related Art Conventionally, an audio signal is FM-modulated and the FM
Optical space transmission in which a modulated audio signal is converted into an infrared signal by an infrared light emitting diode and transmitted, the infrared signal is received by a photodiode, and the audio signal obtained by FM demodulating the received signal is supplied to a headphone. A device has been proposed.

[0003]

Since the conventional optical space transmission apparatus converts an FM-modulated audio signal into an optical signal and transmits it, it is said that the sound quality (frequency characteristic and S / N) of reproduced audio is poor. There are drawbacks. Also, when transmitting a stereo audio signal in optical space, since it is transmitted using individual carriers,
The noise balance and sensitivity balance are poor. Further, in order to avoid cross modulation, the conversion characteristic of the light emitting diode is linear, so that the conversion efficiency is low and the reception sensitivity is low.

In view of the above point, the present invention proposes an optical space transmission device having good sound quality, good noise balance and sensitivity balance in the case of stereo audio signals, high conversion efficiency, and high reception sensitivity. Is what you are trying to do.

[0005]

According to a first aspect of the present invention, there is provided an optical space transmission apparatus which receives a video signal and a quadrature phase shift keying (hereinafter abbreviated as QPSK) modulated audio subcarrier signal. The filter 33 is provided with a detection output of a signal to separate the audio subcarrier signal and a light emitting element 35 driven by the audio subcarrier signal from the filter 33.

The optical free space transmission apparatus according to the second aspect of the present invention comprises a light receiving element 36, a demodulating means 40 for QPSK demodulating the output of the light receiving element, and a PCM decoder 41 for PCM demodulating the output of the demodulating means 40. It is a thing.

An optical space transmission apparatus according to a third aspect of the present invention includes a filter 33 for separating a voice subcarrier signal by supplying a detection output of a received signal including a video signal and a QPSK modulated voice subcarrier signal, and the filter 33. A light emitting element 35 driven by an audio subcarrier signal from the filter 33, a light receiving element 36 for receiving an optical signal from the light emitting element 35, a demodulation means 40 for QPSK demodulating the output of the light receiving element 36, and its demodulation. And a PCM decoder 41 for PCM demodulating the output of the means 40.

[0008]

According to the first to third aspects of the present invention, the light emitting element 35 is driven by the QPSK-modulated audio subcarrier signal from the filter 33, and the light signal is transmitted from the light emitting element 35. The light signal from the light emitting element 35 is received by the light receiving element 36, and the QPSK obtained from this is obtained.
The modulated voice subcarrier signal is QPSK demodulating means 4
0 and demodulated output is PCM decoder 41
PCM decoding by.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below. Prior to that, the structure of a general satellite broadcast receiving apparatus will be described with reference to FIG. The antenna 1 such as a parabolic antenna or a plane antenna receives radio waves from a broadcasting satellite, a communication satellite, or the like, and receives the received signal (11.7 to 12.0 G).
Hz) to the BS converter (first frequency conversion circuit) 2
Supply to. This BS converter 2 has 1 for the received signal.
It is a circuit for mixing a local oscillation signal of 0.67 GHz to obtain a first intermediate frequency signal (1.0 to 1.3 GHz).

The first intermediate frequency signal is supplied to the mixer 6 through the high frequency amplifier 5 of the second frequency conversion circuit (including the wave detector 10) via the input terminal T of the BS tuner 3, and is supplied from the local oscillator 7 by the local oscillator 7. The second intermediate frequency signal is obtained by being mixed with the local oscillation signal of (1), is supplied to the detector (detector using PLL) 10 through the intermediate frequency amplifier 9, and is FM detected (demodulated). The local oscillation frequency of the local oscillator 7 is controlled by the PLL 8 according to the selected channel. The PLL 8 is controlled by the microcomputer 11. The second intermediate frequency signal including the video signal, which is the detection output from the detector 10 of the second frequency conversion circuit 4, and the QPSK-modulated audio subcarrier signal is a band for separating the de-emphasis circuit 12 and the audio subcarrier signal. Pass filter (passband center frequency is 5.73
MHz) 17 and the detection output terminal 25.

The video signal from the de-emphasis circuit 12 is supplied to the energy spread signal removal circuit 14 through the low pass filter 13 to remove the energy spread signal, and then the output terminal 16 of the video output through the amplifier 15.
Is supplied to.

The QPSK-modulated voice subcarrier signal separated by the bandpass filter 17 is QP
It is supplied to the SK demodulator 18 for QPSK demodulation, and the demodulated output is supplied to the PCM demodulator (decoder) 19 for P
CM demodulation (decoding) is performed to obtain a digital stereo audio signal. This digital stereo audio signal is D / A
The analog left and right audio signals L and R are supplied to the converter 20 and D / A converted to obtain the left and right audio signals L and R, which are the de-emphasis circuit 21 and the mute circuit 2.
2 to the output terminals 23 and 24. The circuits 17 to 22 are composed of a voice demodulation IC. The mute circuit 22 mutes the left and right audio signals L and R by using the error flag or the frame synchronization detection signal by the parity check.

Next, the embodiment of the present invention will be described in detail with reference to FIG. 1A, but the portions corresponding to those in FIG. 3 will be assigned the same reference numerals and overlapping description will be omitted. First, the transmission system 31 will be described. The transmission system 31 is an adapter used by being connected to the BS tuner. The second intermediate frequency signal including the video signal which is the detection output from the detector 10 of the second frequency conversion circuit 4 of the BS tuner 3 of FIG. 3 and the QPSK-modulated audio subcarrier signal is the detection output terminal 25.
Is supplied to a bandpass filter (passband center frequency is 5.73 MHz) 33 for separating an audio subcarrier signal similar to the bandpass filter 17 of FIG. Then, the QPSK from the bandpass filter 33
The modulated audio subcarrier signal is applied to a series circuit of a suitable number of infrared light emitting diodes 35 and resistors.

Next, the receiving system 32 will be described. As shown in FIGS. 1B and 1C, the receiving system 32 is provided integrally with the headphone 46 or the speaker 47.
A photodiode for receiving an optical signal from the light emitting diode 35 of the transmission system 31 (headphone 46 or speaker 4
A series circuit of 36 and a resistor 37 (provided outside 7) is connected between the power supply + B and ground. A QPSK-modulated audio subcarrier signal from the midpoint of connection between the photodiode 36 and the resistor 37 is passed through the AGC amplifier 38 to remove a signal other than the audio subcarrier signal. .7
3 MHz) 39 to be supplied to the QPSK demodulator 40 for QPSK demodulation. The demodulated output is supplied to the PCM demodulator (decoder) 41 and demodulated (decoded) to obtain a digital stereo audio signal. This digital stereo audio signal is supplied to the D / A converter 42 to obtain analog left and right audio signals L and R. The left and right audio signals L and R are supplied to the headphone 46 of FIG. 1B or the speaker 47 of FIG. 1C through the low pass filter 43 and the output terminals 44 and 45.

Circuits corresponding to the de-emphasis circuit 21 and the mute circuit 22 of FIG. 3 may be sequentially provided between the D / A converter 42 and the low-pass filter 43. Further, the voice demodulation IC circuit including the circuits 17 to 22 in the BS tuner of FIG. 3 may be applied to the reception system 32. In this case, when the optical signal from the light emitting diode 35 of the transmission system 31 is weak, the reception system 32 can avoid the noisy voice reproduction by using the mute circuit. In the optical space transmission device of the embodiment, a data signal may be transmitted together with a voice signal. The optical signal to be transmitted is not limited to an infrared signal, but may be another type of optical signal such as visible light.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the BS tuner 3 is built in the transmission system 31, and other configurations are the same as the configurations of the embodiment of FIG.

[0017]

According to the present invention described above, the audio signal is converted into Q
Since it is converted into an optical signal in the PSK-modulated state and transmitted in the optical space, the sound quality of stereo audio in A mode, B mode, etc. is good, and in the case of a stereo audio signal, the noise balance and sensitivity balance are good, and moreover, An optical space transmission device with high conversion efficiency and high reception sensitivity can be obtained.

Further, most commercially available BS tuners are provided with a detection output terminal from which a detection output of a reception signal including a modulated voice subcarrier signal can be obtained.
There is no need to modify the tuner. Since the optical signal of the digitally modulated audio signal is transmitted, there is no sound quality deterioration due to noise interference. Since the receiving system can use the voice demodulation IC used for the BS tuner, the cost is low.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a satellite broadcast receiving device.

[Explanation of symbols]

 1 Antenna 2 BS Converter 3 BS Tuner 31 Transmission System 32 Reception System 33 Bandpass Filter 35 Infrared Light Emitting Diode 36 Photodiode 39 Bandpass Filter 40 QPSK Demodulator 41 PCM Demodulator (Decoder) 42 D / A Converter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04L 27/22 Z 9297-5K

Claims (3)

[Claims] 1. A filter for receiving a detection output of a reception signal including a video signal and a four-phase phase shift keying modulated audio subcarrier signal to separate the audio subcarrier signal, and the audio from the filter. An optical space transmission device comprising: a light emitting element driven by a subcarrier signal. 2. An optical space transmission device comprising: a light receiving element, a demodulation means for demodulating an output of the light receiving element by four-phase phase shift keying, and a PCM decoder for PCM demodulating an output of the demodulation means. 3. A light-receiving element for receiving an optical signal from the light-emitting element, demodulation means for demodulating the output of the light-receiving element by four-phase phase shift keying, and a PCM decoder for PCM demodulating the output of the demodulation means. The optical space transmission device according to claim 1, wherein