CN1246767A - Method for implementing bidirectional carrier channel in cable TV system - Google Patents
Method for implementing bidirectional carrier channel in cable TV system Download PDFInfo
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- CN1246767A CN1246767A CN 99106820 CN99106820A CN1246767A CN 1246767 A CN1246767 A CN 1246767A CN 99106820 CN99106820 CN 99106820 CN 99106820 A CN99106820 A CN 99106820A CN 1246767 A CN1246767 A CN 1246767A
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- low
- cable
- pass filter
- low frequency
- frequency
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Abstract
A method for implementing bidirectional carrier channel in cable TV system features that low-frequency structural filter member is connected to the interface of up-line down-line RF device in cable TV. Said low-frequency structured filter member is formed by filter whose cut-off frequency is lower than the lowest frequency of up-line RF signal, so creating an additional bidirectional interactive carrier channel for the bidirectional transmission of network management and control signals. Its advantages are simple structure, easy implementation, high reliability and low cost.
Description
The present invention relates to a kind of coax network system, particularly relate to a kind of in cable television system the method for implementing bidirectional carrier channel.
Cable television system has caused people's extensive concern because of the carrier that its extremely wide frequency band is expected to become information superhighway, but the problems such as control and management that cause the funneling effect of return noise and be difficult to realize network because of the branch type structure of its network, thereby make its two-way interactive function be difficult to realize.Because the distribution region of cable TV is wide, scale is also in rapid expanding constantly, the mode that various places often take classification to power on the spot again, it is bigger with difference variation to add the coaxial cable transmission characteristic, make the failure rate of existing network continue higher, and the existing systems function only limits to unidirectional down line mode, therefore causes the have no way of operating state of each several part in the understanding system of cable TV network, more can't monitor automatically.This problem is just seriously perplexing each cable TV station's net.If realize the two-way mutual business with existing technology, just must in last/downstream signal, respectively mark one section management control command of transmitting channel specially, and the interference of up channel return noise can't solve all the time, has therefore just fundamentally restricted the Application and Development of two-way mutual business in existing coax network.
The objective of the invention is to utilize the coax network of cable television system, provide a kind of on the cable television system/build a two-way carrier channel again outside the downlink radio frequency, realize the method for transmitted in both directions network management control signaling.
The object of the present invention is achieved like this, this carrier channel be in cable television system, construct one than on the cable TV/low frequency carrier signal passage that the downlink radio-frequency signal frequency band is low, this low frequency carrier signal passage be by on cable TV/interface of downlink radio frequency device inserts the low frequency filtering member and realizes.Described low frequency filtering member is made of filter, and the cut-off frequency of its filter should be lower than the low-limit frequency of the up radiofrequency signal of cable TV.
Because the passback interference noise majority of network system all is the millivolt level, this moment, low frequency carrier signal can adopt significantly signal, thereby made the interference noise of millivolt level very little to its influence.Can take segmented mode when concrete the application, making needs the distance of low frequency carrier signal transmission to shorten, and makes the low frequency carrier signal in each section can be without intermediate links such as amplification, thereby has guaranteed the reliability that signal transmits.Have simple in structure, implement convenience, reliable operation, advantage such as with low cost.
Fig. 1 is the basic composition block diagram of low frequency filtering member of the present invention;
The embodiment block diagram that Fig. 2 uses in cable television system for the present invention;
Fig. 3 is the basic circuit schematic diagram of low frequency filtering member of the present invention in concrete the application.
Be described in detail the specific embodiment of the present invention below in conjunction with accompanying drawing:
The transmission signals frequency band of the coaxial cable that the current cable system adopts is more than 0～1000MHz, and the attainable bandwidth of cable TV radio-frequency devices is about 5～1000MHz.We just utilize the 0～5MHz frequency range that does not adopt as yet to construct a low frequency carrier signal passage.Can be divided into downlink radio-frequency signal frequency band, up radiofrequency signal frequency band and AC/DC supply access from the existing system structure of cable TV.Its supply access is a low pass filter (some is a choking-winding) of crossing flow pattern.We by on cable TV/interface of downlink radio frequency device (3) inserts a low frequency filtering member (10), just can hew out one section low frequency carrier signal signal band again when assurance is by current capacity.Described low frequency filtering member (10) is made of filter, this member is because of the practical application position difference in television network system, its concrete structure is also different, and when only needing the low frequency carrier signal passage as not needing supply access, this member is only used a low pass filter f
1(4) connect a high pass filter f again
2(6), should satisfy simultaneously: the low-limit frequency＞f of up radiofrequency signal
1＞f
2When not only needing current circuit but also needing the low frequency carrier signal passage, can be at above-mentioned low pass filter f
1(4) with high pass filter f
2(6) the power supply low pass filter f in parallel again of the tie point between
3(5), satisfy simultaneously: the low-limit frequency＞f of up radiofrequency signal
1＞f
2＞f
3Above-mentioned low pass filter f
1(4) be to extract low frequency carrier signal and supply current in order to isolate radiofrequency signal, high pass filter f
2(6) be in order from low frequency carrier signal and supply current, to extract low frequency carrier signal, power supply low channel filter f
3(5) be in order to isolate low frequency carrier signal and to connect the power supply branch road.When connecing this low frequency carrier signal passage, can on the basis of said structure principle, rationally expand for two above interfaces of needs.
Fig. 2 is that a cable TV device that adds the low frequency carrier signal passage connects block diagram.The cable TV device here can be an active device, also can be passive device.Be effectively to isolate supply current and low frequency carrier signal, can on the cable TV/add a high pass filter (2) on the interface of downlink radio frequency device (3).Narrate/go the workflow of radiofrequency signal, supply current and low frequency carrier signal below in conjunction with Fig. 2 is concise and to the point:
1, on/and the workflow of downlink radio-frequency signal: enter on the cable TV/amplify in the downlink radio frequency device (3) or after distribution etc. handles, import next stage network configuration (12) into through last/downlink radio-frequency signal high pass filter (11) again through last/downlink radio-frequency signal high pass filter (2) from the radiofrequency signal of upper level network configuration (1).
2, the workflow of supply current: as connector J
1During connection, supply current is directly through low pass filter f
1(4), connector J
1, low pass filter f
1(4) be next stage network configuration (12) power supply, supply current also can be through power supply low pass filter f simultaneously
3(5), change over switch K is a means of power at the corresponding levels.When supply unit was charger, supply current can be through change over switch K, power supply low pass filter f
3(5) be system's power supply.As connector J
1When not being communicated with, supply current is through low pass filter f
1(4), power supply low pass filter f
3(5), change over switch K is to means of power.If this moment connector J
2Be communicated with, then again through power supply low pass filter f
3(5) through low pass filter f
1(4) sending is that the next stage network configuration is powered.If connector J2 is disconnected, then power supply is only till the corresponding levels.If supply unit is a charger, as connector J
2When not being communicated with, then can be by change over switch K decision to arbitrary branch road direction power supply; As connector J
2Be communicated with, then power simultaneously to two branch road directions.Here the route walked of supply current is for the low frequency carrier signal Signal Spacing between higher level's network configuration (1) and the undernet structure (12) is opened, so that divide the low frequency carrier signal section during practical application neatly in network.3, the flow process of low frequency carrier signal signal: (a), as connector J
1When not connecting, from the low frequency carrier signal signal of upper level network configuration through low pass filter f
1(4), high pass filter f
2(6), entering modulator-demodulator (7) again carries out after the demodulation data being sent in the processor (8).Processor (8) recognition data is if give the then storage of controlling oneself, if not then ignoring; Need processor (8) to continue to transmit to next stage if having plenty of in giving the data of controlling oneself, then processor (8) sends in the modulator-demodulator (9) after the modulation these data again through high pass filter f
2(6), low pass filter f
1(4) pass toward subordinate's network configuration (12).Processor (8) is then sent into these data modulator-demodulator (7) modulation after high pass filter f if there are data back to transmit
2(6), low pass filter f
1(4) pass back to the upper level network configuration.This situation is applicable to two sections transfer of data between the low frequency carrier signal passage.(b), as connector J
1During connection, the low frequency carrier signal that upper level network configuration (1) transmits is through low pass filter f
1(4), the one tunnel directly through connector J
1, low pass filter f
1(4) enter next stage network configuration (12); Another road is through high pass filter f
2(6), by entering processor (8) (process is the same) after the demodulation.Can remove a high pass filter f this moment
2, modulator-demodulator branch road (this situation is applicable in the low frequency carrier signal signal segment other device except that this section and being connected of other section some devices).Because low pass filter f
1(4) be low frequency carrier signal and the supply current that extracts in order to isolate radiofrequency signal, so its structure should adopt LC or LCR type low pass filter, utilize its inductance support arm to pass through electric current; The line footpath of inductance coil should be decided by the size of supply current.Power supply low pass filter f
3(5) be to give supply unit in order to isolate low frequency carrier signal by supply current, the line footpath of its inductance support arm also should be determined by supply current.
During concrete enforcement, on/cut-off frequency of downlink radio-frequency signal high pass filter (2), (11) should be chosen to be 5MHz usually by the determined upward signal low-limit frequency decision of national standard.Low pass filter f
1(4), high pass filter f
2(6) and power supply low pass filter f
3(5) the concrete numerical value of cut-off frequency can determine according to the level that each filter can reach, will make the minimum that influences between each frequency simultaneously.In the selection of concrete component parameters, except that the factor that will consider supply current, also to consider withstand voltage parameter.Below we provide one group of concrete parameter: f
1=1MHz; f
2=40KHz; f
3=10KHz;
A physical circuit principle of low frequency filtering member of the present invention is provided by Fig. 3.A, b two ends join with upper and lower level network configuration respectively among the figure, are connected to the TV RF device between c, the d.Numerous because of kind, the model of cable TV radio-frequency devices, concrete device does not here draw.E and f should connect modulator-demodulator and processor system, can select different model for use and off-the-shelf is arranged because of these two kinds of devices, also do not provide its concrete form here.9 connect supply unit.Change over switch can be single-pole double-throw switch (SPDT).C among the figure
1, C
2, L
1And C
3, C
4, L
2The T type high pass filter of forming two 5MHz, C
1=C
2=C
3=C
4≈ 430PF, L
1=L
2≈ 2.4uH; L
3, C
5And L
4, C
6The inverted L shape overcurrent low pass filter of forming two 1MHz, L
3=L
4≈ 12uH, C
5=C
6≈ 2.1nF, C
7, L
5And C
8, L
6The 40KHz high pass filter of forming two inverted L shapes, C
7=C
8≈ 54nF, L
5=L
6≈ 300uH; L
7, C
9And L
8, C
10The inverted L shape overcurrent low pass filter of forming two 10KHz, L
7=L
8≈ 1.2mH, C
9=C
10≈ 210nF.
Existing cable TV network all is for the unidirectional or bi-directional RF signal more than the 5MHz designs from structure, as introducing the low frequency carrier signal passage technology, then needs network configuration is carried out suitable adjustment and improvement.(we get 40KHz～1MHz), be far from being enough for cable television system this point bandwidth in side circuit though the low frequency carrier signal passage technology has been opened a low-frequency band.In addition, because problems such as distance, middle route have determined that also the transmission range of low frequency wave passage can not be excessive.Therefore we take from front to back the low frequency carrier signal passage, and segmented structure all is an independently low frequency carrier signal passage in each section, and isolates for low frequency carrier signal between section and the section step by step.Each section can make full use of whole low frequency carrier signal frequency bands like this.Transfer of data between the low frequency carrier signal passage of two adjacent segment can be carried out relay by the processor that is connected between them in the point.Low frequency carrier signal in so both can the section of making is unblocked, also can the section of making and section between closely connect, thereby make whole net connection become an organic whole.
By accompanying drawing as can be known, all be provided with processor in each device basically, and in fact the low frequency carrier signal passage is exactly the passage of communicating by letter between each processor.Consider the characteristics of cable television system control, in a low frequency carrier signal channel section, should select master/slave working method for use between each processor, promptly the processor with the linking point that is connected with the preceding paragraph is a primary processor, the processor of other device in the section is from processor, from processor be and primary processor between carry out exchanges data.Communication mode can be selected single worker or duplex mode for use.For whole network, the computer of front end will be passed to first section to the Network Management instruction, and then from front to back, one section one section ground relay is till this instruction arrives the destination.If when certain device wanted forward end to beam back certain answer or request in the same network, signaling also can arrive front end through inverse process.
From situation about introducing previously, it is proper that the low frequency carrier signal passage technology is applied in the small-sized cable television system.Because if be applied in the large scale system, then need many middle low frequency carrier signal sections to carry out relay, both increased the difficulty of networking, reduced efficient and reliability again widely.And in hfc plant, because the scope that each optical node covers is more and more littler, the level below 500 families of optical node being located at that has, low frequency carrier signal section in each optical node scope only need be laid two to three grades and can be met the demands like this, thereby the efficient of transfer of data and reliability are improved greatly.Constantly perfect along with hfc plant technology in recent years provide a very vast potential for future development will inevitably for the development and use of low frequency carrier signal passage technology.
The low frequency carrier signal passage be actually on the cable TV/the 3rd frequency band offering outside the downstream bands, each device all is equivalent to be connected in parallel on the low frequency carrier signal passage, so it does not have the restriction on the direction, this is for design and use and bring great convenience.Here our the low frequency carrier signal bandwidth of setting is 40KHz～1MHz, can apply in a flexible way at different situations when practical application.The higher time-frequency band of speed that needs can be set widelyer, and the speed that needs can be narrower when low.Certainly whether this must be other signal to be brought under the situation of influence taking into full account.Also can become several portions to the low frequency carrier signal frequency band division, take a part during a certain function, take a part when developing another kind of function again in exploitation, or the like.Simultaneously simple because of low frequency carrier signal passage technology principle, frequency is low, can adopt advantage such as common components and parts, and makes it be expected to become a kind of inexpensive technology.
The low frequency carrier signal passage technology makes us can set up the wired TV network management system with comparalive ease.We can the one-level one-level, one section one section ground is from main line, to service main, arrives user's distribution network again, arrives user side at last.Had after the low frequency carrier signal passage, be equipped with suitable soft, hardware again, we just can set up network management system, realize the real-time monitoring of network, the adjustment of each device operational factor, thereby reduce the failure rate of network widely, improve reliability.If the low frequency carrier signal passage has reached user's splitter one-level, the method that radio-frequency (RF) switch then can be set by the branch outlet at user's splitter reaches the purpose whether the signal service is provided for the user.Along with the low frequency carrier signal passage extends to user side, telephone number when putting telephone lines into operation after we can reach user watched situation, video request program with it or the like information is transmitted out, can pass the answer of front end back user side again.If customer requirements video-on-demand service, we can want the concrete program of program request according to the user from the low frequency carrier signal passage, after front end is examined its qualification, utilize certain idle frequency to play this program, tell frequency that this user's receiver need use, decoding process, secret key etc. by the low frequency carrier signal passage simultaneously.For both-way communication services such as phones, front end is after knowing destination number that the user will dial, data type etc., concrete parameter such as transmitting-receiving frequency that just can the designated communication both sides, code encoding/decoding mode, carrier level, the exchange of communication system and control and management just are not difficult to have realized like this.
Claims (4)
1, a kind of in cable television system the method for implementing bidirectional carrier channel, it is characterized in that: described two-way carrier channel be one than on the cable TV/low frequency carrier signal passage that the downlink radio-frequency signal frequency band is low, this low frequency carrier signal passage construct be by on cable TV/interface of downlink radio frequency device inserts low frequency filtering member (10) and realizes.
2, according to claim 1 a kind of in cable television system the method for implementing bidirectional carrier channel, it is characterized in that: described low frequency filtering member (10) is made of filter, and the cut-off frequency of its filter should be lower than the low-limit frequency of the up radiofrequency signal of cable TV.
3, according to claim 1 and 2 a kind of in cable television system the method for implementing bidirectional carrier channel, it is characterized in that described low frequency filtering member (10) is by low pass filter f
1(4) with high pass filter f
2(6) link, and satisfy: the low-limit frequency＞f of up radiofrequency signal
1＞f
2Constitute.
4, according to claim 1 and 2 a kind of in cable television system the method for implementing bidirectional carrier channel, it is characterized in that described low frequency filtering member (10) is at low pass filter f
1(4) with high pass filter f
2(6) the power supply low pass filter f in parallel again of the junction between
3(5), and satisfy: the low-limit frequency＞f of up radiofrequency signal
1＞f
2＞f
3Constitute.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99106820 CN1246767A (en) | 1999-05-25 | 1999-05-25 | Method for implementing bidirectional carrier channel in cable TV system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99106820 CN1246767A (en) | 1999-05-25 | 1999-05-25 | Method for implementing bidirectional carrier channel in cable TV system |
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| Publication Number | Publication Date |
|---|---|
| CN1246767A true CN1246767A (en) | 2000-03-08 |
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|---|---|---|---|
| CN 99106820 Pending CN1246767A (en) | 1999-05-25 | 1999-05-25 | Method for implementing bidirectional carrier channel in cable TV system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110012248A (en) * | 2019-04-17 | 2019-07-12 | 深圳沃顿科技有限公司 | A kind of LED based on TOPCOB technology actively shines low bright high ash TV platform |
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1999
- 1999-05-25 CN CN 99106820 patent/CN1246767A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110012248A (en) * | 2019-04-17 | 2019-07-12 | 深圳沃顿科技有限公司 | A kind of LED based on TOPCOB technology actively shines low bright high ash TV platform |
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