CN204316507U - HFC cable television network system - Google Patents

Abstract

The utility model proposes a kind of HFC cable television network system, it comprises television signal transmission end RFTV, Cable Modem Terminal System CMTS, organize optical receiver more, many groups optical sender and multiple optical node, described each optical node connects one group of optical receiver and one group of optical sender by optical cable, the below of described each optical node is also connected with organizes user side more, described optical receiver of often organizing includes power supply VCC, photodiode PD, resistance R1, signal processing circuit A and radio-frequency (RF) output end OUT, also comprise radio frequency and amplify output control module, splitter C, radio-frequency probe RD and comparator P.When adopting said structure can solve multi-path light receiver conjunction road, the problem of noise superposition.

Description

HFC cable television network system

Technical field

The utility model relates to cable TV network technical field, is specifically a kind of HFC cable television network system.

Background technology

Hybrid fiber coax (HFC) cable TV network generally comprises Cable Modem Terminal System (CMTS), television signal transmission end RFTV, the radiofrequency signal that television signal transmission end is launched is by after signal transacting, be transmitted on optical cable by optical sender OTX, optical node NODE is by the connection and lighting level mobile phone Received signal strength with optical cable and be processed into TV signal and use to user side CM, when user needs back information, by the optical sender on optical node, send signal on optical cable, television signal transmission end is also provided with back transmission optical receiver ORX and receives return path signal, CMTS is given after the signal received with other several roads back transmission optical receiver is polymerized, each like this optical node needs to connect one group of optical sender and one group of optical receiver by optical cable, in tradition optical node, optical sender is all continuous mode, time namely even without user's signal transmission, also be continuous luminous, the noise signal of the optical sender on optical node is just contained in the signal so received due to the back transmission optical receiver ORX of television, and be polymerized due to the signal of CMTS Shi Youji road ORX, so noise will superpose and become large, affect the signal to noise ratio of whole system.

Utility model content

Technical problem to be solved in the utility model is, overcomes the defect of prior art, provides and can solve multi-path light receiver when closing road, a kind of HFC cable television network system with noise elimination function of problem of noise superposition.

For solving the problems of the technologies described above, the utility model proposes a kind of HFC cable television network system, it comprises television signal transmission end RFTV, Cable Modem Terminal System CMTS, organize optical receiver more, many groups optical sender and multiple optical node, described each optical node connects one group of optical receiver and one group of optical sender by optical cable, the below of described each optical node is also connected with organizes user side more, described optical receiver of often organizing includes power supply VCC, photodiode PD, resistance R1, signal processing circuit A and radio-frequency (RF) output end OUT, described power supply VCC connects ground connection after photodiode PD and resistance R1 successively, it also comprises radio frequency and amplifies output control module, splitter C, radio-frequency probe RD and comparator P, the output of described photodiode PD connects the input of splitter C by signal processing circuit A, one of splitter C exports the input that termination radio frequency amplifies output control module, the output that radio frequency amplifies output control module connects radio-frequency (RF) output end OUT, the input of another output termination radio-frequency probe RD of splitter C, an input of the output termination comparator P of radio-frequency probe RD, another input termination threshold voltage input VREF of comparator P, the output termination radio frequency of comparator P amplifies the control end of output control module.

After adopting aforesaid way, the light signal on this road is converted to radiofrequency signal by photodiode and signal processing circuit, when there being radiofrequency signal to enter in back transmission optical receiver, divide a part to radio-frequency probe RD by a splitter C, radiofrequency signal is converted to the signal of telecommunication, compare by inputting VREF with a threshold voltage, judge whether this road has in light signal and whether modulated radiofrequency signal input, if had, just amplify output control module by radio frequency, Shi Gai road normally exports radiofrequency signal, if detect that this road back transmission optical receiver does not have radiofrequency signal, then control radio frequency and amplify output control module, it is zero that radio frequency is exported, owing to being engraved in change when the signal on back transmission optical receiver is, therefore, when the above-mentioned back transmission optical receiver of multichannel connects together work, when closing road, one tunnel only with radiofrequency signal just has radiofrequency signal to export, the output on other road is all zero, so also just avoid other road to the interference on a road having signal, greatly reduce noise, improve the signal to noise ratio of return system.

Improve as one, described radio frequency amplifies output control module and comprises radio frequency amplifier AMP and radio-frequency (RF) switch S, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end of the output termination radio-frequency (RF) switch S of radio-frequency (RF) output end OUT, described comparator P by radio-frequency (RF) switch S.Adopt this structure, need to increase a radio-frequency (RF) switch S on original radio frequency amplifier, control radio-frequency (RF) switch by the output of comparator P, structure is simple, has higher requirement to the response time of comparator and radio-frequency (RF) switch.

Improve as another, it is one with the radio frequency amplifier AMP of control end enable that described radio frequency amplifies output control module, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end enable of the output termination radio frequency amplifier of radio-frequency (RF) output end OUT, described comparator P.Adopt this structure, need original radio frequency amplifier to replace with one with the radio frequency amplifier of control end enable, control radio frequency amplifier by the output of comparator equally, make radio frequency amplifier work or do not work, adopt components and parts less.But there is higher requirement the time response of radio frequency amplifier and comparator.

Accompanying drawing explanation

Fig. 1 is the structural representation of the utility model cable television network system;

Fig. 2 is the circuit diagram of one of the embodiment of a back transmission optical receiver in Fig. 1;

Fig. 3 is the circuit diagram of the embodiment two of a back transmission optical receiver in Fig. 1;

Embodiment

Below in conjunction with the drawings and specific embodiments, the utility model is described in further detail:

Shown in Fig. 1, for a kind of configuration diagram of traditional HFC cable television network system, transmission of television end shown in figure is with 4 road optical sender OTX1, OTX2, OTX3, OTX4 and 4 road back transmission optical receiver ORX1, ORX2, ORX3, the framework of ORX4, also 4 optical node NODE1 are had in this system, NODE2, NODE3, NODE4 (returning optical sender in Node is all the optical sender issued continuously), for NODE1, NODE1 connects OTX1 and ORX1 by optical cable, 256 user sides are also connected to after NODE1, CM1 ~ CM256, during user's back information, signal is sent by the passback optical sender in NODE1, by the ORX1 Received signal strength of transmission of television end, back transmission optical receiver in the application adopts as Fig. 2, structure shown in Fig. 3, when there is no user profile in a road back transmission optical receiver, just close this back transmission optical receiver, because synchronization only has a road to have signal in time-division application, such as have user to send it back breath of delivering a letter in optical node NODE1, so just only have in ORX1 and receive user profile, so the output of ORX2 ~ ORX4 is zero, the signal be so aggregated in CMTS just only has the signal in ORX1, greatly reduce the noise of system.

As shown in Figure 2, for one of embodiment, a kind of back transmission optical receiver, it comprises power supply VCC, photodiode PD, resistance R1, signal processing circuit A and radio-frequency (RF) output end OUT, described power supply VCC connects ground connection after photodiode PD and resistance R1 successively, it also comprises radio frequency and amplifies output control module, splitter C, radio-frequency probe RD and comparator P, the output of described photodiode PD connects the input of splitter C by signal processing circuit A, one of splitter C exports the input that termination radio frequency amplifies output control module, the output that radio frequency amplifies output control module connects radio-frequency (RF) output end OUT, the input of another output termination radio-frequency probe RD of splitter C, an input of the output termination comparator P of radio-frequency probe RD, another input termination threshold voltage input VREF of comparator P, the output termination radio frequency of comparator P amplifies the control end of output control module.Described radio frequency amplifies output control module and comprises radio frequency amplifier AMP and radio-frequency (RF) switch S, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end of the output termination radio-frequency (RF) switch S of radio-frequency (RF) output end OUT, described comparator P by radio-frequency (RF) switch S.

When light signal enters into optical receiver, radiofrequency signal is converted to by photodiode and signal processing circuit, connect splitter C again, a part of radiofrequency signal is sent to radio-frequency probe by splitter C, radio-frequency probe converts radiofrequency signal to the signal of telecommunication, is input to a port of comparator, by comparing with threshold voltage, open radio-frequency (RF) switch S, enable radio frequency amplifier normally export radiofrequency signal.The size of threshold voltage can be adjusted according to the size of the radiofrequency signal of modulating in light signal.If when this road back transmission optical receiver does not have light signal to input or when not having a modulated radio signal, would not have the signal of telecommunication to comparator, so comparator would not have output signal, radio-frequency (RF) switch is just closed radiofrequency signal and is exported, and it is zero that Shi Gai road radiofrequency signal exports.

Fig. 3 is embodiment two, a kind of back transmission optical receiver, it comprises power supply VCC, photodiode PD, resistance R1, signal processing circuit A and radio-frequency (RF) output end OUT, described power supply VCC connects ground connection after photodiode PD and resistance R1 successively, it also comprises radio frequency and amplifies output control module, splitter C, radio-frequency probe RD and comparator P, the output of described photodiode PD connects the input of splitter C by signal processing circuit A, one of splitter C exports the input that termination radio frequency amplifies output control module, the output that radio frequency amplifies output control module connects radio-frequency (RF) output end OUT, the input of another output termination radio-frequency probe RD of splitter C, an input of the output termination comparator P of radio-frequency probe RD, another input termination threshold voltage input VREF of comparator P, the output termination radio frequency of comparator P amplifies the control end of output control module.It is one with the radio frequency amplifier AMP of control end enable that described radio frequency amplifies output control module, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end enable of the output termination radio frequency amplifier of radio-frequency (RF) output end OUT, described comparator P.

When entering into optical receiver with the light signal modulating radiofrequency signal, radiofrequency signal is converted to by photodiode and signal processing circuit, connect splitter C again, a part of radiofrequency signal is sent to radio-frequency probe by splitter C, radio-frequency probe converts radiofrequency signal to the signal of telecommunication, be input to a port of comparator, by comparing with threshold voltage, control radio frequency amplifier works, radio frequency amplifier is normally worked, if when this road back transmission optical receiver does not have light signal to input, voltage would not be had to comparator, so comparator would not have output signal, radio frequency amplifier does not work, it is zero that Shi Gai road radiofrequency signal exports.

Claims (3)

1. a HFC cable television network system, it comprises television signal transmission end RFTV, Cable Modem Terminal System CMTS, organize optical receiver more, many groups optical sender and multiple optical node, described each optical node connects one group of optical receiver and one group of optical sender by optical cable, the below of described each optical node is also connected with organizes user side more, it is characterized in that: described optical receiver of often organizing includes power supply VCC, photodiode PD, resistance R1, signal processing circuit A and radio-frequency (RF) output end OUT, described power supply VCC connects ground connection after photodiode PD and resistance R1 successively, it also comprises radio frequency and amplifies output control module, splitter C, radio-frequency probe RD and comparator P, the output of described photodiode PD connects the input of splitter C by signal processing circuit A, one of splitter C exports the input that termination radio frequency amplifies output control module, the output that radio frequency amplifies output control module connects radio-frequency (RF) output end OUT, the input of another output termination radio-frequency probe RD of splitter C, an input of the output termination comparator P of radio-frequency probe RD, another input termination threshold voltage input VREF of comparator P, the output termination radio frequency of comparator P amplifies the control end of output control module.

2. HFC cable television network system according to claim 1, it is characterized in that: described radio frequency amplifies output control module and comprises radio frequency amplifier AMP and radio-frequency (RF) switch S, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end of the output termination radio-frequency (RF) switch S of radio-frequency (RF) output end OUT, described comparator P by radio-frequency (RF) switch S.

3. HFC cable television network system according to claim 1, it is characterized in that: it is one with the radio frequency amplifier AMP of control end enable that described radio frequency amplifies output control module, an output of described splitter C connects the input of radio frequency amplifier AMP, the output of radio frequency amplifier AMP connects the control end enable of the output termination radio frequency amplifier of radio-frequency (RF) output end OUT, described comparator P.