JPS6126388A - Addressable method - Google Patents

Abstract

PURPOSE:To execute a stable addressing by overlapping a carrier wave having the frequency and the phase same as a chrominance subcarrier wave with a signal subjected to the phase modulation by a data signal in a vertical blanking interval of a video signal. CONSTITUTION:A center device 90 is constituted of a program transmitting VTR, modulator, etc. An address data 105 transmitted to a terminal device 200 from a data generator circuit 104 is made one input to a phase modulator circuit 107 through an LPF, while a chrominance aubcarrier signal 108 is added to the other input. Frequency and phase of a signal 18 is synchronized with those of a color burst signal. This carrier is phase-modulated by the phase modulator circuit 107 with the aid of the address data, thereby obtaining the signal 108. When said signal 108 is multiplexed to the decided portion in a vertical feedback period of a composite video signal 102, it turns out to be a multiplex video signal 110. It is mixed with other television signals in a mixer circuit 113 through a modulation circuit 111, and transmitted to a trunk cable 114.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an address pull method in a CATV system or the like.

Conventional Structure and Problems In the conventional CA TV system and direct satellite broadcasting, fees are collected according to the program viewing status of the subscriber.

There are various fee structures, but generally a fixed viewing fee is collected as a monthly fee. In such a case, if a subscriber does not pay the fee, the terminal device owned by the subscriber, that is, the C
A terminal control method is used to stop the operation of an ATV converter or a satellite broadcast converter so that subscribers cannot view the broadcast.

As one of these terminal control methods, a unique number (address number) is assigned to each converter owned by each subscriber, and the sending side specifies the above address number in some way, allowing the specified terminal device to function. An addressable system is used to control multiple terminals when sending data such as stopping or starting functions.

In the above system, as a method for transmitting data such as address numbers from the sending side to the center device, a digital signal is superimposed on the vertical blanking interval (VBI interval) of the television signal using a means similar to teletext broadcasting. Broadly speaking, two methods are generally used: division multiplexing and frequency division multiplexing, in which a carrier wave for data transmission is provided in a frequency band other than the television signal or in a frequency band occupied by the standard television signal, for example, above the audio carrier frequency. It is.

In the above-mentioned frequency division multiplexing method, the method of superimposing data in digital signal format on the vertical retrace interval cannot use the vertical retrace interval used in teletext multiplex broadcasting and facsimile multiplex broadcasting, and moreover, In lines where many main line amplifiers are inserted, waveform distortion occurs due to deterioration of group delay characteristics caused by variations in the input and output impedance of these devices, making it difficult to reproduce stably. In order to reduce the number of bits, the bit width must be widened, that is, the transmission speed must be slowed down. The same is true in weak electric field regions and ghost generation regions, which has the drawback that stable extraction and reproduction requires a fairly large extraction and regeneration circuit, resulting in extremely high costs. There is.

In the conventional frequency division multiplexing method, a separate carrier wave for data transmission is provided, which requires a dedicated modem and the usable occupied bandwidth is often limited. It has drawbacks such as the possibility that beat interference may occur due to video signals and audio signals.

Purpose of the Invention The present invention uses a carrier wave having exactly the same frequency and phase as a color subcarrier within the vertical retrace interval of a video signal in a CATV system or a direct satellite broadcasting system, and performs phase modulation on this carrier wave with a data signal. The purpose of the present invention is to provide an addressable method that eliminates the drawbacks of conventional time division multiplexing systems and frequency division multiplexing systems and can perform addressing stably at low cost by superimposing multiplexed signals. .

Focusing on the fact that there is no effect on conventional transmission equipment even if a phase modulation signal using a carrier wave having the constituent phases of the invention is superimposed, the above color sub-modules can be By superimposing a phase modulated carrier wave on a carrier wave, the data necessary for addressing can be sent using a time division multiplexing method.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. Figure 1 is CAT
2 is a block diagram of an addressable system using a time division multiplexing system in the V system, and FIG. FIG. 2 is a diagram showing main waveforms of FIG.

In a CATV/stem, a large number of terminals are connected to one center device, and these terminals are connected by coaxial cables. The center device 9o is also called a head end, and is composed of a VTR (not shown) for transmitting programs, a modulator, and the like. Address data 105 for addressing is generated and sent out in data generation circuit 104 by a microcomputer or the like in synchronization with start pulse 100. The start pulse 100 indicates the starting position to be superimposed on the video signal, that is, the beginning of the address data multiplexing period 300 in FIG. It is generated using them.

FIG. 2 b3o generated in the data generation circuit 104
Address data 10 to be sent to the terminal device 200 shown in 1
5 is usually a TTL level digital signal, and LPF
(low-pass filter) 106.

These signals are input to the phase modulation circuit 107 after unnecessary spectrum signals outside the required band are removed by the LPF 106 . On the other hand, a color subcarrier signal 108 as shown in FIG. 2 b3o2 is applied to the phase modulation circuit 107 as the other input signal.

The color subcarrier signal 108 is generated from the composite video signal 102 including the synchronization signal and the color burst signal in the color subcarrier reproducing circuit 103 as a signal having one frequency and one phase synchronization with the color burst signal. Normally, the above signal can be easily generated by a PLL (phase locked loop) circuit using a 3.58 MHz crystal resonator similar to that built in a TV receiver. The color subcarrier 108 obtained as described above is used as a carrier wave for address data transmission, and the phase modulation circuit 107 performs phase modulation on this carrier wave using the address data to obtain a phase modulated signal 108.

This waveform is shown in FIG. 2 b303. The figure shows a waveform of two-phase phase modulation. A phase modulation signal 108 that has been phase-modulated by a phase modulation circuit 107 using a color subcarrier is converted into a composite video signal 10 containing a synchronization signal and a color burst signal by a synthesis circuit 109 after removing a DC component.
A multiplexed video signal 11o is obtained by multiplexing the phase modulation signal into a predetermined portion of two vertical blanking periods. Since the phase modulated color subcarrier signal does not contain a DC component,
The waveform of the synthesized multiplexed video signal 110 is shown in Fig. 2 b30.
4, and if we consider this as the vertical retrace period, the second
The waveform is shown in Figure a. A multiplexed video signal 110 on which address data 105 has been multiplexed is applied to a modulation circuit 111, subjected to normal modulation, mixed with a TV signal 112 of another channel in a mixing circuit 113, and sent out to a trunk cable 114. . The signal is sent out to the trunk cable 114, passes through the RF doubler signal splitter 115 and the lead-in a116, and is led to the terminal device 200. Terminal device 200I'
1 In the CATV converter; IA), the tuner 201 selects the frequency on which the address data is multiplexed, and the detection circuit 202 generates the multiplexed video signal 203.
is demodulated. The multiplexed video signal 203 is sent to the center device 1.
It has the same waveform as the multiplexed video signal 110 in 01. This multiplexed video signal 203 is transmitted to the color subcarrier recovery circuit 20
4, and also to a BPF 205 for extracting color subcarrier components, a color subcarrier trap 206, and a color subcarrier removal circuit 208. The color subcarrier reproducing circuit 204 is exactly the same as that used in general television receivers, and uses PLL technology to obtain a reproduced color subcarrier 209 phase-synchronized with the color burst signal in the multiplexed video signal. The reproduced color subcarrier 209 has the same frequency as the color subcarrier 108 in FIG. 1, and is phase-synchronized. On the other hand, from the multiplexed video signal 203, the color subcarrier extraction BPF 205 simultaneously extracts the phase modulation signal multiplexed during the vertical blanking period along with the color signal in the video signal in the multiplexed video signal. The signal containing the phase modulated signal extracted in this way is supplied to demodulation circuit 210. The phase modulation signal has the same waveform as the phase modulation signal 108 of the center device 90. In the demodulation circuit 210, the reproduced color subcarrier 209 is used to convert the BP
The output signal of F206 and the multiplication are combined. On the other hand, the color subcarrier trap 206 removes the color subcarrier component from the multiplexed video signal 203, leaving only the synchronization signal and the luminance signal in the video signal, and these signals are sent to the gate signal generation circuit 2.
07. A gate signal generation circuit 207 separates the synchronization signal, and based on these signals, a gate pulse 211 is output for extracting the multiplexed address signal from the vertical retrace period. The signal is supplied to a removal circuit 208 .

Address data 214 is extracted from the signal demodulated by the demodulation circuit 210 using the gate pulse 211 . Note that 213 is a waveform shaping circuit for address data. Note that the gate pulse 211 is a pulse having a width of the address data multiplexing period 300 in FIG. 2a. Further, the multiplexed video signal 203 is input to the color subcarrier removal circuit 20.
8, the superimposed address data portion is removed from the vertical retrace period to obtain the original composite video signal 212. The specific configuration of the color subcarrier removal circuit 208 is explained in the third section.
As shown in the figure. The multiplexed video signal 203 applied to the color subcarrier removal circuit 208 in FIG. 1, that is, the multiplexed video signal 400 in FIG. By switching, it is switched to the color subcarrier trap 404 side during the address data multiplexing period 30Q in FIG. 2a, and to the opposite side in other cases. The multiplexed video signal 400 that passed through the color subcarrier Trump 404 side during the address data multiplexing period has the color subcarrier component, that is, the phase modulated address data removed, and when the above period ends, the changeover switches A and B are switched and input. multiplexed video signal 400
is output as the 11 composite video signal 405. The multiplexed video signal 203 that has passed through the color subcarrier removal circuit 208 as described above can be obtained as a signal similar to the composite video signal 102 from the center device 900. Further, the address data signal output from the demodulation circuit 2IO is shaped into a square wave signal by a waveform shaping circuit 213, and address data 214 at TTL level is obtained. Using the address data 214 obtained in this way, the terminal device 200
The address is determined in the desk simple circuit (
(not shown), etc.

As described above, in the present invention, addressing can be easily performed by using a color subcarrier having the same frequency and phase as the color burst during the vertical retrace period, performing phase modulation with address data, and multiplexing it during the vertical retrace period. Become.

Effects of the Invention According to the present invention, there is no influence on conventional transmission equipment, there is little influence from group delay distortion, etc., and there is no restriction or influence on scrambling methods such as video random inversion. Furthermore, there is no need for complex lock extraction circuits for data reproduction required for demodulating phase modulation signals, and color subcarriers can be used, making it possible to transmit highly stable and highly reliable high-speed data signals. In addition, it can be constructed using parts used in portable TV receivers, and can be realized at a very low cost, resulting in excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the AtresoSapple method using the time division multiplexing method in a CATV system, and FIG. 1 is a diagram showing waveforms of each part in FIG. 1, and FIG. 3 is a specific configuration diagram of a color subcarrier removal circuit in a terminal device. 90... Center device, 101... Synchronization separation circuit, 103... Color subcarrier regeneration circuit, 107...
... Phase modulation circuit, 109 ... Synthesis circuit, 11
1...Modulation circuit, 201...Tuner,
2゛02...Detection circuit, 204...Color subcarrier regeneration circuit, 210...Demodulation circuit.

Claims (3)

[Claims] (1) Data transmission by time division multiplexing, in which a multiplexed signal obtained by performing phase modulation with a data signal on a carrier having the same frequency and phase as the color subcarrier during the vertical retrace period is superimposed with the DC component removed. An addressable method that allows (2) Claim 1 characterized in that the multiplexed signal is superimposed on the pedestal level of the vertical blanking period.
Addressable method as described in Section. (3) The addressable method according to claim 1, characterized in that the transmission rate of the data signal is set to be an integral fraction of the color subcarrier frequency.