CN1111333C - Backward channel noise suppressor for optical fibre and coaxial cable mixed network - Google Patents
Backward channel noise suppressor for optical fibre and coaxial cable mixed network Download PDFInfo
- Publication number
- CN1111333C CN1111333C CN 99110746 CN99110746A CN1111333C CN 1111333 C CN1111333 C CN 1111333C CN 99110746 CN99110746 CN 99110746 CN 99110746 A CN99110746 A CN 99110746A CN 1111333 C CN1111333 C CN 1111333C
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- China
- Prior art keywords
- gain amplifier
- backward channel
- blender
- signal
- input end
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Abstract
The present invention relates to a reverse channel noise suppressor for a mixed optical fibre coaxial network, which is composed of two mixers and a controllable gain amplifier, wherein the input end of a first mixer is connected with the input end of a second mixer, the other input end of the first mixer is connected with the input end of a testing circuit, the output end of the testing circuit is connected with the input end of the controllable gain amplifier, and the output end of the controllable gain amplifier is connected with the other input end of the second mixer. The device is in a high-gain state for a reverse channel and is in low-gain state without a reverse signal so as to avoid noise or interference effect on the transmitting end of a forward signal, and thus, a funneling effect of noise and interference is greatly reduced.
Description
The present invention relates to a kind of interchannel noise (comprising interference) restraining device, particularly a kind of backward channel Noise Suppression Device that is used for hybrid fiber coax.
CATV-cable network distributes as the wired broadcasting formula of multichannel television signal originally.Along with the development of cable television network, particularly fiber optic applications behind cable television network, network performance has had qualitative leap, network can develop into bi-directional communication network.Have the cable television network of optical fiber to be called hybrid fiber coax, promptly the HFC net is a kind of of broadband access network.The cable television network of non-fiber is the special case of HFC net.But the cable system of HFC net is a tree, and dividing has forward channel and backward channel.Forward channel be signal from the TV you to user side, claim down channel again; Backward channel be signal from user side to the TV you, deserve to be called capable channel again.The reverse channel signals of each branch road will produce converging action, and noise and interference also produce converging action, are called " funnel " effect.Funneling effect influences the quality of backward channel, reduces the signal to noise ratio of backward channel.
The purpose of this invention is to provide a kind of Noise Suppression Device that guarantees hybrid fiber coax reverse channel quality and signal to noise ratio.
Backward channel noise suppressor for optical fibre and coaxial cable mixed network is realized by following measure: it is to be made of 2 blenders and controllable gain amplifier, an output of first blender is connected with an input of second blender, another output of first blender is connected with the input of controllable gain amplifier, and the output of controllable gain amplifier is connected with another input of second blender.
HFC net backward channel Noise Suppression Device of the present invention is to be connected on each branch of a network or user side, and its effect is equivalent to a controllable gain amplifier to backward channel (attenuator can be considered negative gain amplifier).Reverse signal often is paroxysmal, cut in and out, and noise and interference often exists.When certain branch road or certain user had reverse signal, Noise Suppression Device was high-gain (or low decay) state to backward channel.When certain branch road or certain user do not have reverse signal, be low gain (or high decay) state, thereby stop noise or disturb influence the TV you.So only allow the branch road of signal or the noise and the interference of user side leak, reduce the funneling effect of noise and interference greatly, the influence that makes the signal to noise ratio of backward channel improve and suppress to disturb.
The invention will be further described below in conjunction with accompanying drawing.
Fig. 1 is a line principle block diagram of the present invention;
Fig. 2 is a kind of physical circuit figure of Fig. 1.
With reference to Fig. 1, Fig. 2, hybrid fiber coax is made of blender 1,4, testing circuit 2, controllable gain amplifier 3, and its input, output are at reverse signal.Input, output have downstream signal and upward signal, are to finish the conversion of signals of the input of itself to output through blender 1,4.Common blender has two kinds of filtering type or ferrite device formulas.Filtering type blender 1 is made of high pass filter 1-1 and low pass filter 1-2, and filtering type blender 4 is made of high pass filter 4-1 and low pass filter 4-2.High pass filter 1-1 and high pass filter 4-1 are connected to form the forward radio frequency signal channels, and this passage has only downstream signal to pass through.Low pass filter 1-2, controllable gain amplifier 3 and low pass filter 4-2 connect and compose the reverse radio-frequency signalling channel successively, and this passage has only upward signal to pass through, and suppress the noise in this passage upward signal.The capacitor C 1 of controllable gain amplifier 3, C2 are capacitance, and diode D is the PIN type diode of an automatically controlled decay, when electric current passes through, radio frequency are Low ESR.When no current passes through, be high impedance.Choke L1, L2 are the radio-frequency current choke, allow direct current flow through and radio-frequency current is intimate off-state.Resistance R is a current-limiting resistance.A is a control end.Capacitor C 1 front is a delay line.Delay line, capacitor C 1, diode D, capacitor C 2 are connected in the circuit successively, and choke L1 is connected between the tie point of control end A and capacitor C 1 and diode D, choke L2 be connected between diode D and capacitor C 2 tie points and the ground after resistance R is connected.When control end A added forward voltage, backward channel was low decay, and control end A is making alive or when adding negative voltage, backward channel is high decay not.Delay line is used to adjust the sequential of control signal and reverse signal passage.Above-mentioned backward channel noise suppressor for optical fibre and coaxial cable mixed network by blender 1,4 and controllable gain amplifier 3 connect and compose when user side uses, is provided the control signal of control end A by the user.If when this backward channel Noise Suppression Device is used in the hybrid fiber coax centre, need a testing circuit 2 to be used, the control signal of control end A is provided, when this moment as up channel have radiofrequency signal, be coupled on the radio frequency amplifier K through resistance R 3, R4 dividing potential drop, again after detector diode D1, capacitor C, becoming direct voltage outputs on the comparator B, to be positive voltage be output as high level through comparator B after relatively to voltage after the detection, the electric current that then flows through diode D is greater than 0, diode D is low-resistance, thereby allows uplink channel signals pass through.When up channel did not have radiofrequency signal, comparator B was input as 0, comparator B output low level, and the electric current that then flows through diode D is 0, diode D is high resistant, hinders passing through of noise and interference.Testing circuit 2 has certain delay, there is being radio frequency rate signal due in one time difference τ to be arranged to producing the high level output time, must be equal to or greater than τ the time of delay of delay line, otherwise, when radiofrequency signal arrives diode D, diode D also is not able to do in time open-minded, promptly also is low resistance state, and radiofrequency signal can be intercepted a part.There is the use pattern of testing circuit 2 also to be fit to the user side use.The reference voltage V R of comparator B is greater than 0 volt.
Claims (2)
1. backward channel noise suppressor for optical fibre and coaxial cable mixed network, it is characterized in that: constitute by blender [1,4] and controllable gain amplifier [3], an output of blender [1] is connected with an input of blender [4], another output is connected with the input of controllable gain amplifier [3], and the output of controllable gain amplifier [3] is connected with another input of blender [4].
2. hybrid fiber coax backward channel Noise Suppression Device according to claim 1 is characterized in that: between the input of another output of described blender [1] and controllable gain amplifier [3] testing circuit [2] is set.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99110746 CN1111333C (en) | 1999-07-29 | 1999-07-29 | Backward channel noise suppressor for optical fibre and coaxial cable mixed network |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99110746 CN1111333C (en) | 1999-07-29 | 1999-07-29 | Backward channel noise suppressor for optical fibre and coaxial cable mixed network |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1283041A CN1283041A (en) | 2001-02-07 |
| CN1111333C true CN1111333C (en) | 2003-06-11 |
Family
ID=5274661
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 99110746 Expired - Fee Related CN1111333C (en) | 1999-07-29 | 1999-07-29 | Backward channel noise suppressor for optical fibre and coaxial cable mixed network |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1111333C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101237255B (en) * | 2007-01-30 | 2011-05-04 | 仲琦科技股份有限公司 | Method for reducing the uplink intrusion noise of cable data system |
| CN102035571B (en) * | 2009-10-03 | 2014-01-08 | 瑞昱半导体股份有限公司 | Signal transceiving circuit and noise reduction circuit |
| CN106657860B (en) | 2016-12-23 | 2019-09-17 | 浙江大华技术股份有限公司 | A kind of video extender, its control method and coaxial view control transmitting device |
-
1999
- 1999-07-29 CN CN 99110746 patent/CN1111333C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CN1283041A (en) | 2001-02-07 |
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| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C19 | Lapse of patent right due to non-payment of the annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |