Early stage cable TV network is the coax network that broadcast television signal efficiently is sent to subscriber household, and this cable TV network can be efficiently to user's transportation simulator TV signal.Traditional in recent years cable TV network extensively begins to adopt Hybrid Fiber Coaxial (HFC) transmission structure, and optical cable backbone and coaxial cable distribution net are by light station be combined into.General fiber optic backbone adopts star topology, and coaxial cable distribution net then adopts star-like or tree, and this structure has been widely used in the distribution of broadcast television signal.Generally adopt the network topology structure that is adapted to broadcast mode, i.e. TV signal → front end → optical cable → sub-district node → coaxial cable → user's check configuration among the HFC.This structure makes the HFC transmitted in both directions become possibility.
Be accompanied by the rush of demand of multiple business such as data communication, have been found that in coaxial cable enterprising line width band data service and CATV TV signal, to insert to have tangible technical advantage.Thus, in recent years, the development of cable TV network wideband data access technology was very fast, and wherein (Cable Modem, CM) technology is that China's employing at present also is at most a kind of of maturation to cable modem.
The CM technology is a kind of technology that the enterprising line width band of catv network coaxial cable data insert that is used for, can not have influence on simultaneously the TV signal transmission and watch effect, that this technology is followed is interface specification (the Data Over Cable Service InterfaceSpecification of cable transmission data business, DOCSIS) agreement, this agreement are the interface specification of a cover about communication and the operation of CM on HFC.DOCSIS has covered the whole operations to end user's Data transmission service, and the providing of service, safety, data-interface and radio frequency interface (RFI) are provided.Radio frequency interface is the key that realizes the cable television appliances interoperability.
But the CM technology need take the band resource of more different frequency range, its equipment complexity, and application cost is higher.The RFI framework of DOCSIS is made up of 3 bulks: the head end that is installed in cable television operators is front end CM terminating systems (CMTS), the hfc plant infrastructure in the main equipment and is installed in CM in the user house.Communicating by letter between CMTS and the CM is a little to multiple spot, full duplex, and data communication need be transmitted by CMTS, and up frequency is below 65MHz, and descending frequency is more than 550MHz.For HFC, system generally adopts the transmission means of uplink and downlink nonsymmetric channel, mark off a 8MHz frequency range channel in the television channel between the effective frequency range 110～1000MHz of hfc plant, the downlink data that is used for the forms of broadcasting sends, when signal adopts 256QAM (quadrature amplitude modulation) modulation system, flank speed can reach 40Mbps, and upstream data then returns by the FDMA/TDMA of one section 2MHz frequency range channel between 5～65MHz with shared model.
Although CM is the ripe broadband access technology of current a kind of technology, but it is to propose and formulate agreement by the U.S. the earliest, though this agreement is applicable to cable TV network structure that it is local and the user characteristic distributions of living, but be not suitable for the national conditions of China, so many problems have appearred in the CM technology in the promotion and application of China at present, the CM in many places is professional even stagnation occurred, has limited carrying out of cable TV network data access service greatly.Its subject matter is as follows:
(1) return noise problem
The maximum at present difficult point of CM technology is how to overcome upstream noise.The CM technology can be applied in user's distribution network of tree network, and this is its advantage, but also brings the problem of influx noise simultaneously.Its noise source is at user side, user's noise mainly comes from the signal input port of television set in the user family, disturb all kinds of household electrical appliance of root in terminal, bad or the variation of performance is shielded in covering of network element device cable, the frequency range of being disturbed between 5～40MHz of data feedback channel for the strongest, when the intensity of interference signal surpassed the user level, upward signal can't normal transmission.The user is many more, and various noise collection effects just form funneling effect behind front end, has limited user's access number greatly, and this is the main cause that data feedback channel produces noise.Secondly also there is the invasion noise, as narrow sideband shortwave interference, impulse disturbances.The impulse disturbances frequency is very low, and between 60Hz～2MHz, the harmonic components that it produces is very big, and the noise jamming that causes is especially severe also.The equipment of amateur radio station, cable TV, various device interface become flexible in addition, loose contact etc. also can form the invasion noise.Return noise brings the factors of instability for the broadband access of whole network, brings many difficulties for the CM scheme implementation, has increased the complexity of engineering.
(2) application cost height
Operator and terminal use's cost of investment height.The CM business will be invested CMTS equipment at front end, will invest CM at user side, so that this business is carried out is many more, the investment of CMTS and CM is just big more.Especially the restriction of the access quantity brought of return noise has also increased the input cost of each user's incoming end of operator.
(3) CM is not suitable for China's national situation
The technology of CM is not suitable for the structure of China's cable TV network and the resident characteristic distributions of living.China resident's living environment is concentrated relatively, is example with building, a residential quarter, and several at most one hundred houses are tens families at least, and the optical node of present most of cable TV networks has generally all been received the building, how to determine that the CM number of users of optical node becomes a difficulty.For example international patent application No.:PCT/SE2004/000177 discloses method and the modulator-demodulator that carries out data communication in a kind of cable television network, it adopts the power line communications access way based on modulation technique, but this power line communications access way obviously is not suitable for the national conditions of China.Have only the topological requirement that could adapt to CM of the existing cable TV network of corresponding change, and in a single day the catv network structure of building up can not changed easily.This situation has also limited the development of CM greatly.Along with going deep into of the star-like retrofit work of China cable TV subscriber distribution network, CM technology advantage in this respect is also more and more littler.
In order to solve the problem of above-mentioned existence, to be operator insert part the user to way in the past just lays an Ethernet local area network (LAN) of being made up of category-5 cable, thereby reach the purpose of the shared CM of a plurality of users, do one like this and can significantly reduce up noise; Its two, be under identical user, reduce the investment of CMTS and CM widely; Its three, at technological layer, CM and LAN be in conjunction with can controlling flow at an easy rate, thereby prevent " connecing steathily " phenomenon effectively.Shortcoming is that operator need drop into bigger fund and sets up the Ethernet local area network (LAN).Secondly, the user of the Ethernet local area network (LAN) network security problem when surfing the Net that also can occur coexisting.In normal circumstances, few user's LAN comes connection device by hub (HUB), hub is that the signal of multiport amplifies distributing equipment, signal is not done the broadcasting share equipment of handling that stores, all users in the local area network (LAN) share a bandwidth, do not possess the VLAN partition functionality, the user in each corridor is the network neighbor, has the subscriber computer safety issue.All to take whole transmission channel during at last owing to each telex network, so there is the factor of broadcast storm.
Summary of the invention
In view of above-mentioned deficiency of the prior art, the present invention is proposed.Therefore, the present invention aims to provide a kind of switching technology that the enterprising line width band data service of cable TV network coaxial cable and cable TV signal insert simultaneously that is used for, it can realize simultaneously by cable TV network broadband access network and see the function of TV, and it is high and be not suitable for the defective of the structure of China's cable TV network to overcome return noise, the application cost of CM technology.
According to a scheme of the present invention, a kind of Coaxle cable exchanging system is provided, be used for by coaxial cable while access network data-signal and cable TV signal, this Coaxle cable exchanging system comprises the bastion host assembly and passes through the connected user terminal assembly of coaxial cable, wherein, this Coaxle cable exchanging system comprises the network allocation amplifying device that is used to realize the mutual conversion between the network data signals of balance and the unbalance network data-signal on the coaxial cable, this network allocation amplifying device comprises the push-pull power amplifier circuit and offsets isolating transformer that this push-pull power amplifier circuit is used for the network data signals of the balance of input is amplified; This offsets isolating transformer and is connected to this push-pull power amplifier circuit, be used to receive amplifying signal from this push-pull power amplifier circuit, export unbalanced signal at an output to coaxial cable, and receive from the unbalance network data-signal on the coaxial cable, be converted into balance network data signals and in another output output.
In the above-mentioned Coaxle cable exchanging system, this push-pull power amplifier circuit is recommended power amplifier for the AB class.
In the above-mentioned Coaxle cable exchanging system, this offsets isolating transformer is YZ-10 type isolating transformer.
In the above-mentioned Coaxle cable exchanging system, this elementary winding centre cap that offsets isolating transformer connects power supply, first secondary winding also receives from the unbalance network data-signal on the coaxial cable to coaxial cable output unbalanced signal, second subprime winding centre cap ground connection, and the unbalanced signal of described first secondary winding is converted to the network data signals output of balance.
In the above-mentioned Coaxle cable exchanging system, the network data signals in this Coaxle cable exchanging system is a baseband signal.
In the above-mentioned Coaxle cable exchanging system, this bastion host assembly comprises: data exchange module, cable TV subscriber's administration module, data/cable TV signal mixing and control module and described network allocation amplifying device, the upper port access network data-signal of data exchange module wherein, in the lower port except one the tunnel with this cable TV subscriber's administration module is two-way be connected, the two-way connection of a described network allocation amplifying device of each Lu Douyu; These data/cable TV signal mixes and is connected with coaxial cable is two-way with this cable TV subscriber's administration module, described network allocation amplifying device respectively with control module, it receives cable TV signal and network data signals, and this cable TV signal and network data signals are mixed and control.
In the above-mentioned Coaxle cable exchanging system, this data exchange module is the Ethernet exchcange core, and it supports to divide based on the VLAN of port.
In the above-mentioned Coaxle cable exchanging system, the described upper port of this data exchange module is operated in 100Mbps full duplex state, and all the other port workings are at 10Mbps half-duplex state.
In the above-mentioned Coaxle cable exchanging system, the ethernet node of this cable TV subscriber's administration module for constituting by microprocessor and ethernet controller, this microprocessor is connected to this data/cable TV signal mixing and control module and this ethernet controller are connected to this data exchange module by network interface a lower port, this ethernet node is used for controlling the break-make of cable TV signal subscriber channel to these data/cable TV signal mixing and control module output control signal, and is used to handle the current state of the subscriber channel that returns from this data/cable TV signal.
In the above-mentioned Coaxle cable exchanging system, this microprocessor is the 80C52 single-chip microcomputer.
In the above-mentioned Coaxle cable exchanging system, this ethernet controller is RTL8019AS.
In the above-mentioned Coaxle cable exchanging system, these data/cable TV signal mixes with control module and is made up of the high frequency relay and the filter circuit that are subjected to this cable TV subscriber's administration module control.
In the above-mentioned Coaxle cable exchanging system, this filter circuit comprises high pass filter and low pass filter, cable TV signal is imported the input of this high pass filter, be input to the input of this low pass filter from the network data signals of this network allocation amplifying device, be connected with another input of this low pass filter from the cable TV signal of this high pass filter output, this low pass filter will be imported this user terminal assembly through filtered signal, and be input to described network allocation amplifying device from the network data signals of this user terminal assembly via this low pass filter.
In the above-mentioned Coaxle cable exchanging system, this user terminal assembly comprises described network allocation amplifying device, be that terminal network distributes amplifying device, described terminal network distributes network data signals and the cable TV signal of amplifying device reception from coaxial cable, cable TV signal is input to the cable TV interface, and the described isolating transformer that offsets is input to Terminal Network Interface with the network data signals that unbalanced downlink network data-signal is converted to balance; And the uplink network data-signal from Terminal Network Interface amplifies through described push-pull power amplifier circuit, is converted into unbalanced network data signals and is transported to this bastion host assembly by coaxial cable by the described isolating transformer that offsets.
In the above-mentioned Coaxle cable exchanging system, described terminal network distributes amplifying device to adopt constant-current source circuit.
In the above-mentioned Coaxle cable exchanging system, this user terminal assembly comprises adapter, and it is connected between bastion host assembly and the user terminal assembly, is used to separate multichannel wired TV signal.
According to another scheme of the present invention, a kind of coaxial cable switching method that is applicable to Coaxle cable exchanging system is provided, be used for by coaxial cable while access network data-signal and cable TV signal, the bastion host side of this Coaxle cable exchanging system comprises data exchange module, it is characterized in that this method comprises the steps:
From the bastion host side to subscriber terminal side:
Network data signals inserts this data exchange module and carries out exchanges data;
Amplify via the push-pull power amplifier circuit from the network data signals of this data exchange module output, and the network data signals of balance is converted to unbalanced network data signals through offseting isolating transformer;
To mix with cable TV signal from the unbalanced network data signals that offsets isolating transformer output, and mixed signal is sent to subscriber terminal side through coaxial cable; And
At the cable TV interface of subscriber terminal side output cable TV signal, and through offset isolating transformer with unbalanced network data signals be converted to balance network data signals and Terminal Network Interface output and
From subscriber terminal side to the bastion host side:
Amplify through the push-pull power amplifier circuit from the network data signals of Terminal Network Interface, and the network data signals of balance is converted to unbalanced network data signals through offseting isolating transformer;
Be transported to the bastion host side from the unbalanced network data signals that offsets isolating transformer through coaxial cable;
The above-mentioned unbalanced network data signals of carrying through coaxial cable mixes with cable TV signal, and unbalanced network data signals is through offseting the network data signals that isolating transformer is converted to balance in the mixed signal; And
Network data signals access data exchange module from the balance that offsets isolating transformer carries out exchanges data.
In the above-mentioned coaxial cable switching method, before described up blend step, also comprise the steps: to make cable TV signal pass through high frequency relay, in order to the break-make of control cable TV signal passage.
In the above-mentioned coaxial cable switching method, described up blend step comprises the steps: that cable TV signal is input to high pass filter, is input to low pass filter with the network data signals from the balance that offsets isolating transformer behind the filtering interference signals and mixes.
In the above-mentioned coaxial cable switching method, the baseband transmission mode is adopted in the transmission of network data signals wherein.
Technical scheme by the invention described above, doing the access in broadband by catv network when, realization can watch high-quality TV programme, provide the 10Mbps half-duplex to stablize bandwidth, can manage the same while supervising the network of Ethernet and CATV user by image tube, fail safe is good, simple in structure, cost is low.The problem that does not have influx noise and return noise.Simultaneously, the present invention has the function by computer network management CATV user.
Describe the preferred embodiments of the present invention in detail below in conjunction with accompanying drawing.
Fig. 1 is the Organization Chart of Coaxle cable exchanging system according to the preferred embodiment of the invention.As shown in Figure 1, multichannel (for example six tunnel, Shi Erlu, ten six tunnel etc.) distributor is equally divided into multichannel with the cable TV signal of input, and (another kind of form is directly to import from the multichannel wired TV signal of user's distribution network, do not need to distribute, at this moment, no cable TV multichannel distribution module), through multi-channel rf switch and data exchange module output, mix back output through the network downgoing baseband signal after the amplification of network allocation amplifying device in signal mixing module, the mixed signal after the output is transferred to the user terminal box through coaxial cable.The user terminal box is separated into cable TV signal and network downstream signal with mixed signal, cable TV signal user after the TV signal output interface inserts TV can watch cable television program, uplink baseband signal from the network interface of user terminal amplifies after coaxial cable (coaxial cable of CATV user's distribution network) uploads to the network allocation amplifying device, enter in the data exchange module after being converted into the network signal of balance, exchange in order to network signal with the base station.Embedded computer is connected between multi-channel video switch and the data exchange module, is used to control the break-make of user's cable TV passage.
Fig. 2 illustrates each concrete function assembly of Coaxle cable exchanging system according to the preferred embodiment of the invention.This Coaxle cable exchanging system comprises host component and passes through the connected user terminal assembly of coaxial cable.This host component comprises data exchange module, CATV user management module, network allocation amplifying device and mixing of DATA/TV signal and control module etc.This user terminal assembly comprises that terminal network distributes amplifying device etc.
Data exchange module is the Ethernet exchcange core, its realization be the function that can manage layer 2 ethernet switch, it uses high performance Ethernet data exchange chip product, also be many mouthfuls of LAN layer 2 ethernet switches of a standard on circuit design, concrete parameter constantly changes along with the upgrading of exchanger chip.It consists of integrated exchanges data chip, serial storage, isolating transformer, display circuit and the power supply etc. of height function.The lower port of this data exchange module connects the CATV user management module except that one the tunnel, each road all is connected with a network allocation amplifying device circuit, distributes the amplifying device circuit to link to each other by coaxial cable through the mixing of DATA/TV signal with control module and terminal network again.Network data transmission is used the baseband transmission mode, and in transmission over coaxial cable, data is two-way with TV signal, and TV signal is unidirectional, and data transfer bandwidth is stable 10M half-duplex.
It is the module of major part with the single-chip computer control system that the CATV user management module is one, finish and data exchange module between network data transmission, obtain instruction from computer network, generate control signal and be sent to mixing of DATA/TV signal and control module, control the break-make of CATV signal subscriber channel, and can handle the current state of the CATV signal subscriber channel that returns.
For example, this CATV user management module has structurally made things convenient for the function that realizes the transmission of computer network management CATV user CATV signal for by a microprocessor and the ethernet node that ethernet controller constitutes.Microprocessor can be selected the 80C52 single-chip microcomputer for use, ethernet controller can be selected RTL8019AS for use, it is a kind of isa bus ethernet control chip of NE2000 compatibility, meet the IEEE802.310Base-T standard, support automatic parity checking and error correction, support the RJ45 interface, support the full and half duplex pattern.Ethernet control chip is connected with a lower port of data exchange module by the RJ45 interface.Single-chip microcomputer mixes with the DATA/TV signal and is connected with control module, for providing condition by computer network control CATV subscriber channel.Particularly, this single-chip microcomputer is responsible for the RTL8019AS initialization and is realized procotol by RTL8019AS, finishes communication tasks such as the reception of network data and transmission.The I/O mouth of single-chip microcomputer is by the high frequency relay of latch drive controlling on mixing of DATA/TV signal and control module.
The network allocation amplifying device circuit that the lower port of data exchange module connects comprises that the AB class of being made up of discrete component recommends power amplifier and offset isolating transformer.As the work characteristics of AB class push-pull power amplifier, it is little to satisfy load, the circuit requirement that operating current is big.This offsets isolating transformer can realize mutual conversion and transmitted in both directions and impedance conversion between the unbalance network data-signal on the network data signals-coaxial cable of balance, and realize the offseting of interference signal finally realized the correct distribution of signalling channel.The AB class is recommended power amplifier the network signal from data exchange module is amplified, and guarantees that switching system has certain connection distance (100 meters).
Mixing of DATA/TV signal and control module are by formed by monolithic processor controlled high frequency relay of CATV user management and filter circuit.The CATV signal all will pass through a high frequency relay before each passage mixes, the control command control break-make that this relay is sent by the CATV user management module, if relay is in off-state, just disconnected the TV signal of this passage, terminal network distributes amplifying device output just not have TV signal.The current state information of each relay will regularly be detected by the single-chip microcomputer in the CATV user management module.Filter circuit comprises high pass filter and low pass filter, and the CATV signal of input is connected with the input of high pass filter.Network data signals from network allocation amplifying device circuit is connected with the input of low pass filter.Be connected with another input of low pass filter from the TV signal of high pass filter output, this DATA/TV signal mixing and control module are finished multichannel CATV signal and mixing from the unbalance network signal of network allocation amplifying device thus.Mixed signal is sent to terminal network by the CATV coaxial cable and distributes amplifying device, receives the unbalanced network uplink data of distributing amplifying device from terminal network simultaneously.
For example, in mixing of DATA/TV signal and control module, TV RF signals is at first passed through high pass filter, the operating frequency of this high pass filter is preferably 50MHz, can allow the above radiofrequency signal of about 50MHz pass through, filtering 50MHz prevents simultaneously that with interior interference signal network data signals from sealing in the CATV system.From the control signal that single-chip microcomputer is sent here, control the state of high frequency relay by triode, thereby control the switching of TV RF signals.The actual switching state of relay can have, not have by the ohmically voltage that is provided with between single-chip microcomputer IO mouth and high frequency relay contact circuit, and single-chip microcomputer judges that to high-low level this voltage is given single-chip microcomputer and carried out state-detection.Network data signals mixes with TV RF signals by low pass filter, and the operating frequency of this low pass filter is preferably 30MHz, gives user terminal by coaxial cable then.Simultaneously, the data-signal of bringing from user terminal is delivered to the output of network allocation amplifying device again by low pass filter.Low pass filter can also prevent that TV RF signals from sealing in data channel.
Terminal network distributes the structure of amplifying device similar to the network allocation amplifying device, used equally in the circuit to offset isolating transformer and the AB class is recommended power amplifier, but signal sequence is opposite.After receiving the uneven transmission signals of coaxial cable, at first by low pass, high pass filter, TV signal and network signal are separated, next finishes the conversion of unbalanced network signal to the balancing network signal, last TV signal is sent to the TV signal output interface, network signal sending network interface is the RJ45 reticulum for example, the network uplink signal that the computer that connects on the reticulum returns by coaxial cable sends to DATA/TV signal mixing and control module by offseting after isolating transformer is converted to unbalanced signal through the amplification of power amplifier.Realize thus data isolation, offset and distribute, finish correct exchange with the subscriber computer network signal.
Switching system inside provides power supply by coaxial cable to terminal box, because use is constant-current source circuit, has the function of short-circuit protection.Particularly, when heart yearn is powered, under the normal condition, the current value that its supply current sets less than constant-current circuit, the triode in the constant-current circuit is in the saturation conduction state, the about 12V of output voltage, when heart yearn occurring and bump the situation of ground short circuit, constant-current circuit is in constant current state, and its output current is constant, its inner triode is in magnifying state, can not cause the 12V power supply short circuit because of the heart yearn short circuit.
Particularly, Coaxle cable exchanging system of the present invention is when catv network is done access, what use is star-like user's distribution network structure, and at this moment CATV signal and 100Mbps FDX Ethernet circuit (the above or optical fiber of non-shielding category-5 cable) have been received this system, as shown in Figure 2.The network standard that the present invention is suitable for is IEEE802.310Base-T Ethernet and IEEE802.3u 100Base-TX Fast Ethernet etc.Ethernet line at first enters the upper port of the ethernet switch circuitry of data exchange module, sets up with each lower port of Ethernet switch to connect and exchanges data.What lower port received and sent is the network differential signal of standard.The network data signals of importing this data exchange module is a baseband signal, its with TV signal in transmission over coaxial cable, this baseband signal transmission means is compared with the modulation demodulation system that the CM technology adopts, owing to directly use the primitive network signal, avoid using the modulation and demodulation circuit, simplified circuit structure, reduced cost, the frequency of network baseband signal is low simultaneously, below 15Mbps, the problem that does not have the Electro Magnetic Compatibility difference that high-frequency circuit brings is compared the CATV band resource that the CM technology takies and wanted much less, and is little to the interference of TV signal.Owing to adopted the mode of baseband transmission, can directly use the ethernet switch circuitry and the multi-channel network signal of support IEEE802.3 and IEEE802.3U protocol specification directly to link at system front end, the network exchanging chip of selecting for use has the function and the supported vlans of network management and divides agreement, transfer of data is not the broadcast type towards whole network, but set up manyly to the connection from the source port to the destination interface at synchronization, not only solved because all users share the too slow problem of the speed of a bandwidth but also avoided broadcast storm.From at first amplifying behind data exchange module lower port riches all the way feed signals the enters network allocation amplifying device circuit through AB class push-pull power amplifier circuit, through offseting isolating transformer balanced signal is converted to unbalanced signal again, delivering to the DATA/TV signal mixes and control module, mix with TV RF signals by low pass filter, give user terminal by coaxial cable again.The CATV signal is assigned with and enters mixing of DATA/TV signal and control module after device is divided into multichannel TV signal, at first, through the high pass filter filtering for example 50MHz mix with network signal after with interfering signal, this high pass filter prevents that network data signals from sealing in the CATV system simultaneously.The mixed signal of incoming terminal is at first separated it by low pass, high pass filter, the radio frequency TV signal that for example will be higher than 50MHz is given the TV signaling interface that terminal network distributes amplifying device, and the data-signal that is lower than 30MHz is given the network data interface of terminal distribution amplifying device.Enter the data-signal that terminal network distributes amplifying device, through offseting the conversion of isolating transformer, the network signal that changes unbalanced network signal into balance is given the receiving terminal of computer network interface card, and wherein the lower port of data exchange module and computer network interface card all are operated in 10M half-duplex state.The same process earlier of the data-signal that the transmitting terminal of computer network interface card sends AB class is recommended power amplifier and is amplified, through offseting isolating transformer balanced signal is converted to one road unbalanced signal again, deliver to by coaxial cable that the DATA/TV signal mixes and control module, the unbalanced data signal that this road is brought from user terminal is again by delivering to network allocation amplifying device module after the above interference signal of low pass filter filters out 30M.Become the network signal of balance again through the conversion that offsets isolating transformer in the network allocation amplifying device circuit, deliver to data exchange module at last, the lower port of Ethernet switch receives this network signal, thereby finishes the process of whole communication and transmission.
In above-mentioned whole process, offseting isolating transformer removes beyond the mutual conversion of finishing between balanced signal and the unbalanced signal, also to finish isolation, offset effect, when offseting function realization transmission network transmission signal, the signal of receive path is approximately zero, vice versa, thereby realize the correct distribution of data.
Fig. 3 is an exemplary exchange chip port connection layout of realizing the data exchange module function in the Coaxle cable exchanging system of the present invention.The exchange chip RTL8309SB that selects for use only is an example of data exchange module exchange chip of the present invention, but in fact selectable high performance network exchange chip kind is a lot, and it is in the state of regenerating of bringing in constant renewal in.In Fig. 3, one of them port is operated in 100Mbps full duplex state as upper port, and all the other are operated in 10Mbps half-duplex state.
Fig. 4 illustrates the network allocation amplifying device in the Coaxle cable exchanging system according to the preferred embodiment of the invention and offsets the exemplary circuit figure of isolating transformer.Wherein network signal is differential signal (balanced signal), and unbalanced signal is a two-way signaling, by the coaxial cable transmission signals between main frame and the user terminal box.The signal that data exchange module sends couples a signal to the base stage of T1 and T2 pipe by input transformer.In Fig. 4, the secondary of input transformer has centre cap, because centre cap exchanges ground connection, the base stage of T1, T2 obtains the anti-phase signal of a pair of equivalence during work.T1, T2 are a pair of pipe of recommending, and are operated in AB class state, finish the amplification of the positive and negative half cycle of signal respectively.Signal after the amplification is given coaxial cable by output transformer.The output transformer model is the isolating transformer that offsets of YZ 1.The output differential signal of RJ45 network interface enters a winding that offsets isolating transformer through T1, T2, and the winding centre cap connects power supply, and for example giving impedance at secondary winding output unbalanced signal is 75 ohm transmission cable.The uplink network signal (unbalanced signal) that returns from the D end can obtain corresponding signal at another secondary winding that offsets isolating transformer, its centre cap ground connection.This winding produces equivalent anti-phase signal, and its magnetic flux is cancelled out each other.Because this that offsets isolating transformer offsets effect, export in 3,6 end no signals, be that data exchange module is when sending signal, can be with the counter signal receiving end of delivering to data exchange module of signal that sends, and be sent to the signal receiving end that the signal that offsets isolating transformer can be exported to data exchange module from 3,6 ends from transmission cable.Because the unidirectional control action of T1, T2, signal can be by the anti-input that offsets isolated amplifier of sending back to of T1, T2 yet.This offsets isolation, impedance conversion, channel allocation and matching problem that isolating transformer can well solve receive path and sendaisle thus; Solved the mutual transfer problem between the unbalanced signal of balanced signal and transmission over coaxial cable simultaneously.
Fig. 5 is that Coaxle cable exchanging system is linked into the schematic diagram of a plurality of user terminals according to the preferred embodiment of the invention.This switching system can be linked into the user with cable TV signal and the Internet broadband by existing C ATV user distribution network.As the switching system of supporting the multi-user, that a platform switching system can be supported is a plurality of (native system is designed to 6, can expand to 12,14,16 etc.), and the user surfs the Net simultaneously and sees TV, is not affected each other.
Fig. 6 is a Coaxle cable exchanging system net connection topological diagram according to the preferred embodiment of the invention.As shown in FIG., Coaxle cable exchanging system according to the present invention is in the head position, building of star-like cable TV subscriber's distribution network, switching system be input as cable TV signal and network signal, be output as the mixed signal of cable TV and data.The cable TV signal of input may be from one of following situation:
The one-channel signal (coaxial cable) of optical receiver output; And
The multiple signals that hub is distributed (coaxial cable) (this moment, switching system interface was the multiple-input and multiple-output type).
Network signal might be from one of following situation:
Optical fiber interface (switching system is input as the network fiber module, and optical fiber connects);
Ethernet interface (more than the non-shielding category-5 cable); And
The network interface of CM (more than the non-shielding category-5 cable).
The multichannel mixed signal of switching system output enters in each user family by coaxial cable.The slotting formula terminal box of installing at home of wall is separated into cable TV signal and network signal with mixed signal.Network interface is RJ45, and data bandwidth is the 10M half-duplex.Cable TV signal is output as common cable TV Building F.When if a plurality of rooms of user need a plurality of cable TV interface, (adapter among the figure in the black surround and two distributes the equipment that has been integrated into now to need connection adaptor, the common name adapter), use adapter TV signal can be divided into multichannel, as required, adapter can be two distribution, three distribution etc.
Such typical case uses, and can realize the needs of consumer wideband online and the needs that multiple TV set televiews, and both can not influence mutually.
If the demand that has many computers to surf the Net simultaneously in single user family then needs to use the terminal box of multi-user data interface, can guarantee that a tame user shares 10M half-duplex bandwidth at full capacity.
Simultaneously, network management system that this Coaxle cable exchanging system is integrated can be carried out telemanagement respectively to network signal and TV signal, also has functions such as remote system is restarted, port monitoring in addition.
Under aforesaid situation, that is, signal then can use adapter to separate multichannel wired TV signal more than a CATV terminal if customer requirements is registered one's residence.Its functional equivalent distributes in two of cable television system, and the structure of this adapter as shown in Figure 7.Mixed signal from main frame enters adapter, high-pass filtering and low-pass filter circuit through signal separation module are separated into TV signal and network signal, TV signal enters common cable TV two distribution module and on average is separated into two-way, one the tunnel exports TV signal terminal to, and another road exports user terminal to network signal after mixing module mixes.
By foregoing description, can learn that network allocation amplifying device of the present invention, Coaxle cable exchanging system and switching method have following characteristics and advantage:
1. comprise in the network allocation amplifying device and offset the isolating transformer circuit, this offsets isolation, impedance conversion, channel allocation and matching problem that the isolating transformer circuit can well solve receive path and sendaisle; Solved the mutual transfer problem between the unbalanced signal of balanced signal and transmission over coaxial cable simultaneously.
2. what transfer of data adopted is the baseband transmission mode, this baseband transmission mode is compared with the modulation demodulation system that the CM technology adopts, owing to directly use the primitive network signal, avoid using the modulation and demodulation circuit, simplified circuit structure, reduced cost, simultaneously the frequency of network baseband signal is low, below 15Mbps, does not have the problem of the Electro Magnetic Compatibility difference that high-frequency circuit brings, compare the CATV band resource that the CM technology takies and want much less, little to the interference of TV signal.
3. switching system and method adopt single coaxial cable to register one's residence, and not only meet former catv network standard but also support broadband data service, need not existing cable TV network is transformed or rebuild, and have shortened the work period of inserting, and have saved funds.
4. the 100Mbps of various ways such as switching system and direct Ethernet of method support and optical fiber inserts, and under the situation of community network resource bandwidth, reduces investment greatly, has effectively reduced operation cost, has also reduced daily network operation amount accordingly.
5. switching system and method adopt the form of network management that CATV user is carried out integrated management, and promptly the network management software by switching system can carry out data management and also can carry out the CATV user management, and control inserts the break-make of the CATV signal of user side.
6. TV signal/data-signal separate terminal possesses cable TV interface and 10Base-T interface, and provides extending space for upgrading to IP phone, smart card multi-functional user terminal such as check meter.
7. owing to the shared network insertion end of a plurality of users, can effectively suppress the return noise of cable tv coax data feedback channel, avoid the appearance of funneling effect.
8. switching system and method have the function of VLAN, guarantee VLAN of a user, can guarantee the surf the Net safety of computer-chronograph data of user.
9. inner integrated data exchange module of this switching system, transfer of data is not the broadcast type towards whole network, but sets up many to the connection from the source port to the destination interface at synchronization.Not only solved but also avoided broadcast storm owing to the too slow problem of the speed of the shared bandwidth of all users.Because this data exchange module adopts the data storing pass-through mode, has improved safety of data transmission.
Thus, switching system of the present invention and method integrate the network management and the TV signal user management of data service, under the situation that the online of 10M broadband high-speed is provided for the user, the access way of switching system is versatile and flexible, communication speed is fast, fail safe is good, application cost is low, powerful, track remodelling is simple, construction period is short, the multiple demand for development of activating business that meets CATV broad band Integrated service net is very beneficial for the HFC of broadcasting and TV system and carries out data service.