JPS6131673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device that receives a signal in which a multiplexed information signal is phase-encoded and multiplexed into a television signal and transmitted. It is an object of the present invention to provide a device that can receive information signals satisfactorily.

Hereinafter, the present invention will be described using as an example a still image receiving apparatus that receives a still image signal that has been phase-encoded and multiplexed into a television signal.

First, an example of a signal waveform used for transmitting such a still image will be described with reference to FIG.

In this transmission method, first, each unit image of a still image in which multiple unit images such as characters are arranged horizontally is decomposed into, for example, 16 x 16 picture elements, and these are scanned horizontally to form one line. Obtain image signals for each minute. Next, this image signal for each line is phase-encoded using a predetermined clock to produce an image signal V for multiplexing, and as shown in FIG. It is multiplexed and transmitted during the scanning period, for example, at the 20th H (and at the 283rd H; hereinafter, only the 20th H will be described and the 283rd H will be omitted). The clock frequency for multiplexing is set appropriately, but generally it is 2n/msc (where n and m are positive integers, and sc is the frequency of the color subcarrier) to facilitate synchronization with the color subcarrier. ) selected. Here, it is assumed that the clock frequency is set to 2sc. When a signal is processed by such a phase encoding method, as is well known, the signal after phase encoding has a clock frequency.
1/2 frequency, that is, the sc component and its 1/2, 1/
The frequency components of 3,... will be included.
However, since the signal waveform is a pulse waveform, harmonic components are not considered, and only the fundamental wave component is considered. Therefore, throughout the present invention, the term "highest frequency component of an image signal" refers to the highest frequency component of the fundamental wave components in this phase-encoded signal, that is, the frequency component at 1/2 of the clock frequency. The term "component" refers to a component mainly having this highest frequency.

As shown in Fig. 1, at the leading edge of the multiplexed signal there is a start signal ST indicating their reference phase, a program code signal P indicating a still image program, and an image signal V transmitted in the field that is a still image. A control code signal such as a line number signal L indicating the number of the line from the top is added, and the signals are multiplexed and transmitted. The start signal ST is added at a predetermined position and with a predetermined amplitude, regardless of the contents of other multiplexed signals. H is a horizontal synchronization signal, and Bu is a burst signal. Of course, this television signal transmits a normal television video signal during periods other than this multiplexing period.

Next, FIG. 2 shows a block diagram of an image receiving apparatus that receives a multiplexed signal such as a phase-encoded image signal V transmitted in this manner and reproduces a still image of the multiplexed information. In Figure 2,
1 is the antenna, 2 is the image signal V during the vertical retrace period.
3 is a video detection circuit, 4 is a video amplification circuit, 5 is a cathode ray tube, and 6 is an automatic gain control ( AGC) circuit, 7 is a synchronous separation circuit, 8 is a deflection circuit, 9 is a band amplification circuit, 10 is a color demodulation circuit, 11
1 is an automatic color saturation control (ACC) circuit, and 12 is a color subcarrier oscillation circuit, which are similar to those in a normal color television receiver.

In addition, 13 is an amplifier circuit that amplifies the detected video signal, and 14 is the 20th H (and
The 283rd H, below we will only explain the 20th H.
15 is an extraction pulse generation circuit that generates an extraction pulse to extract the 283rd H (the 283rd H is omitted); 15 is an extraction circuit that uses this extraction pulse to extract the multiplexed signal that is multiplexed at the 20th H; 16 is a waveform shaping circuit that shapes the extracted multiplexed signal into a binary signal by slicing it or the like.

17 is an image signal V of the received multiplexed signal
This is a storage circuit section for reproducing a still image by writing and reading it in a memory in a predetermined manner, and stores one line or one page of a video signal obtained by phase decoding the image signal V. A memory 18 for extracting a required phase-encoded image signal V from the waveform-shaped multiplexed signal and performing phase decoding processing to reconvert it into a video signal suitable for still image display. an AIDS decoder circuit 19; a write processing circuit 20 that temporarily stores the phase-decoded video signal in a buffer memory, performs necessary processing such as speed conversion processing, and writes it to a predetermined storage location in the memory 18; , a read processing circuit 21 that performs necessary processing such as reading and amplifying video signals from the memory 18, and a control circuit 22 that controls these to a predetermined operating state.

23 is for supplying a video signal for displaying a normal television received image and a video signal for displaying a still image read from the storage circuit section 17 to the cathode ray tube 5 by superimposing or alternately switching the same. It is a mixed circuit.

Next, the operation of receiving multiplexed information in such a configuration will be explained. First, the detection output including the multiplexed signal obtained from the video detection circuit 3 is sent to the amplifier circuit 13.
Amplify with. The video signal of a normal television image is added to the cathode ray tube 5 via a mixing circuit 23, and a normal television image is projected and displayed.

On the other hand, the detection output amplified by the amplifier circuit 13 is added to the extraction circuit 15, where the information signal multiplexed at the 20th H is extracted, and then the waveform shaping circuit 16 shapes it into a pulse signal with a correct binary signal waveform. . The control circuit 22 detects the start signal ST from this waveform-shaped multiplexed information signal, and also uses the color subcarrier from the color subcarrier oscillation circuit 12 to
Various clock pulses for receiving multiplexed signals are created, some of which are stored in the memory 18 as a memory clock.
Add to. The other part is added to the phase decoder 19 as a clock pulse for phase decoding, and the image signal V is phase decoded and converted into a video signal. In addition, the control circuit 22 uses this clock pulse to detect the program code signal P of the multiplexed signal being received, compares this with a program instruction signal separately instructed by the operator, and determines the program code signal P specified by the operator. The write processing circuit 20 is operated only when the multiplexed signal is received, and the line number signal L is identified and the video signal is transmitted to the memory 18 and written to a predetermined position for recording and accumulation.

Thereafter, the memory 18 is driven by the memory clock from the control circuit 22, the video signal recorded and accumulated in the memory 18 is read out, and mixed with a normal television video signal in the mixing circuit 23, thereby transmitting the signal to the cathode ray tube 5. Display a still image.

As described above, the multiplexed signal containing the phase-encoded image signal V of a still image can be received, stored in the memory, and read out from the memory to display the still image. When receiving a signal together with a normal television video signal, the frequency characteristics, particularly the bandwidth, of the receiving circuit become a problem. That is, when receiving normal television video signals, the frequency bandwidth of intermediate frequency amplification circuits, etc. is limited in order to avoid being adversely affected by audio carrier waves and audio carrier waves of adjacent channels. The image signal of the multiplexed signal as described above has a clock frequency of 2.
This multiplexed image signal V is received in the same state as a normal television video signal. Then
SC, the signal is attenuated by about 6 dB, causing the inconvenience of not being able to receive a good waveform.

In other words, even if an image signal V with a phase-encoded pulse waveform as shown in FIG. 3A is being sent, it is a waveform whose highest frequency component has been attenuated as shown in FIG. 3B. Even if the waveform shaping circuit 16 slices and shapes the waveform at the level shown by the dashed line in the figure, a shaping error will occur and a predetermined image signal as shown in FIG. 3A cannot be reproduced. It disappears. Lowering the slice level is not desirable in terms of noise countermeasures.
Therefore, this makes accurate reception impossible.

In addition, the magnitude of signals with high frequency components is very easily affected by adjustments in the tuner, and even if the AGC circuit is operating correctly or the VIF circuit has compensated for the high frequency range. However, if the image reception condition changes, the amplitude of the high-frequency component of the image signal V changes greatly, making accurate reception difficult.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a device which can eliminate such inconveniences, accurately receive phase-encoded multiplexed information signals such as still image signals, and which can be implemented with an extremely simple configuration. The purpose is to

For this reason, the present invention includes a receiving circuit that receives a television signal that is multiplexed and transmitted with phase-encoded information signals during the vertical retrace period, a detection circuit, and an amplification circuit that amplifies the detection output. A waveform shaping circuit that shapes the output of the amplifier circuit, and a storage circuit that stores the multiplexed information signal. By controlling the gain by a gain control voltage such as the ACC control voltage extracted from the color reproduction circuit, the high-frequency components of the phase-encoded signal are controlled. It is also characterized in that the signal is received with sufficient amplitude.

An embodiment in which the present invention is implemented in a still image receiving apparatus as described above will be described below with reference to FIGS. 4 and 5.

Note that in FIGS. 4 and 5, the same parts as those in FIG. 2 are given the same reference numerals as in FIG. 2, and the explanation thereof will be omitted.

In this device, in a circuit section for receiving a multiplexed information signal, an amplification circuit 13 for amplifying a video detection signal extracted by an extraction circuit 15 and supplied to a waveform shaping circuit 16 is configured to perform phase-encoded multiplexing. The ACC circuit 1 in the color reproduction circuit section uses a variable gain control type that can control the gain for the high frequency components of the color reproduction circuit.
It is controlled by the ACC control voltage generated from 1. The control characteristics are such that when controlling the ACC circuit 11 to increase the gain of the band amplifier circuit 9, the gain of the high frequency component in the amplifier circuit 13 is also increased at the same time.

A concrete example of such a circuit is shown in FIG. This circuit controls the operation of the amplifier circuit 13 and the extraction circuit 15 in one
Although this is performed using one transistor 23, it goes without saying that separate transistors may be used. transistor 23
The received signal in which the multiplexed signal is multiplexed from the video detection circuit 3 is added to the base of the video detection circuit 3, and the extraction pulse is added from the extraction pulse generation circuit 14, and the multiplexed signal is amplified by operating only in the 20th H. I'm trying to extract it. A bias is applied to the emitter of the transistor 24 through resistors 25 and 26, so that it is cut off except during the extraction pulse period. The multiplexed signal taken out from the collector of this transistor 24 is applied to the waveform shaping circuit 16. Coupling capacitors 27 and 28 are set to have sufficiently low impedance even for low frequency components included in the multiplexed signal. In general, the impedance can be made low up to about the horizontal frequency. 2
9 and 30 are matching resistors.

Furthermore, in order to compensate for high-frequency components, a capacitor 31 and a coil 32 are connected to the emitter of the transistor 24.
and a series resonant circuit consisting of a resistor 33,
Grounded via transistor 34. The resonant frequency of this series resonant circuit is set to the frequency of the high-frequency component of the phase-encoded image signal V in the multiplexed signal. Basically, set it to sc, which is the highest frequency. The ACC control voltage from the ACC circuit 11 is applied to the base of the transistor 34 via a diode 35, and a bias voltage obtained by dividing the power supply voltage is applied by a variable resistor 36 to set the level at which high-frequency compensation is started. put. Note that the value of the collector resistor 37 of the transistor 34 is made sufficiently larger than the impedance value of the series resonant circuit, and the value of the emitter resistor 38 is kept small.

With this configuration, the frequency of the image signal V in the multiplexed signal is usually equal to or higher than the frequency of the carrier color signal as described above, and its amplitude also changes almost in the same way as the carrier color signal. Therefore, by automatically controlling the gain of the high frequency component of the multiplexed signal using the ACC control voltage,
The amplitude can be controlled to be the same as the low frequency component, and a signal with no level difference as shown in Figure 3C can be obtained, and by shaping this signal, an accurate waveform can be obtained at any time. It is possible to receive a signal such as that shown in FIG. 3A in a manner that reproduces it.

In other words, when the multiplexed signal is transmitted in a normal transmission state, the tuning frequency is correctly adjusted in the tuner, and the video intermediate frequency amplification circuit is also correctly adjusted, the high-frequency component also becomes low-frequency component as shown in Figure 3C. By adjusting the variable resistor 36 and setting the internal impedance between the collector and emitter of the transistor 34 so that the components are at the same level, multiplexing can occur due to changes in the transmission state or changes in the tuning state of the tuner. The amplitude of the high-frequency component of the signal fluctuates, for example, as shown in FIG. Since the ACC control voltage is generated, this ACC
By changing the internal impedance of the transistor 34 using the control voltage, the damping resistance value in series with the series resonant circuit is changed, and the gain for the high frequency component in the multiplexed signal is changed so as to prevent the amplitude change of the high frequency component. It is possible to always obtain a multiplexed signal with uniform levels as shown in FIG. 3C.

Note that the amplitude of the low-frequency component in the multiplexed signal does not change much even when adjusting the tuner, etc., and is sufficiently stabilized by the operation of the AGC circuit 6. It is effective to perform gain control on the area components.

In particular, for an image signal that is phase-encoded with a 2sc clock, it is only necessary to perform gain control on the sc frequency, which is the highest frequency, and the components of frequencies below 1/2sc hardly fluctuate, so the gain cannot be adjusted. It doesn't have to be controlled.

In this way, this device can accurately receive multiplexed signals including phase-encoded image signals.

In the above explanation, the clock frequency during full phase encoding is the color subcarrier frequency sc.
We have described the case where the clock frequency is twice as high as 1, but even if the clock frequency is set to something other than this, it is sufficient to perform gain control on the high frequency component, especially the highest frequency component, in exactly the same way. The control voltage may be generated by detecting and sample-holding the amplitude of a reference signal that is added in advance to the multiplexed signal at its highest frequency and with a constant amplitude.

Furthermore, it goes without saying that the present invention can be widely used not only for multiplex transmission of still image signals as described above but also for multiplex transmission of various other signals using the phase encoding method.

As described above, according to the present invention, when an information signal that has been phase-encoded and multiplexed into a television signal is transmitted via a television transmission system, the high-frequency components of the received signal are attenuated. This problem can be solved by detecting the attenuation of the amplitude by detecting a signal with a frequency equivalent to the high frequency component in such a received signal. By controlling the gain for the high-frequency components of the variable gain amplifier circuit at the output, the amplitude of the high-frequency components in the received signal can be made equal to the amplitude of the low-frequency components, enabling accurate reception operation. In addition, the attenuation state of the high frequency component can be easily and automatically detected using only the detection means, and automatic compensation can always be made to maintain a good signal state.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining one mode of transmission of a multiplexed signal, Fig. 2 is a block diagram of a conventional multiplexed signal receiving device, and Figs. 3 A, B, and C are for explaining the operation of the same device. FIG. 4 is a block diagram of a multiplexed signal receiving apparatus according to an embodiment of the present invention, and FIG. 5 is a specific circuit diagram of the main parts of the apparatus. 1... Antenna, 2... Receiving circuit, 3... Video detection circuit, 4... Video amplification circuit, 5... Cathode ray tube, 6... AGC circuit, 9... Bandwidth amplifier circuit, 1
0...Color demodulation circuit, 11...ACC circuit, 14...
...Extraction pulse generation circuit, 15...Extraction circuit, 16
...Waveform shaping circuit, 17...Memory circuit section, 18...
... Memory, 19 ... Phase decoder circuit, 20
...Write processing circuit, 21...Read processing circuit, 22
...Memory control circuit, 23...Mixing circuit, 24...
Transistor, 25, 26... Resistor, 27, 28
... Capacitor, 29, 30 ... Resistor, 31 ...
Capacitor, 32... Coil, 33... Resistor, 3
4...Transistor, 35...Diode, 36
...variable resistor, 37, 38...resistance.

Claims (1)

[Claims] 1. A television signal in which a phase-encoded multiplexed signal is multiplexed is received, detected, amplified, and phase-encoded to reproduce an information signal, The amplifier circuit for amplifying the detected signal is of a variable gain type that can control the gain for the high frequency component of the multiplexed signal, and a signal with a frequency equivalent to the high frequency component of the multiplexed signal is extracted. By detecting the signal, its amplitude is detected and a gain control voltage is generated, and the gain control voltage is used to control the gain of the amplifier circuit for the high frequency component, thereby controlling the amplitude of the high frequency component of the multiplexed signal. A multiplexed signal receiving device characterized in that compensation is performed to equalize the amplitude of a low frequency component. 2. The multiplexed signal receiving device according to claim 1, characterized in that the gain for the highest frequency component of the multiplexed signal is controlled. 3 In the color subtone circuit section as a gain control voltage
3. The multiplexed signal receiving device according to claim 1 or 2, characterized in that the ACC voltage is used.