CN101478344A - Light control automatic gain control circuit applied on cable television network optical receiver - Google Patents
Light control automatic gain control circuit applied on cable television network optical receiver Download PDFInfo
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- CN101478344A CN101478344A CNA2008102040046A CN200810204004A CN101478344A CN 101478344 A CN101478344 A CN 101478344A CN A2008102040046 A CNA2008102040046 A CN A2008102040046A CN 200810204004 A CN200810204004 A CN 200810204004A CN 101478344 A CN101478344 A CN 101478344A
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Abstract
The invention relates to an optically-controlled automatic gain control circuit applied to an optical receiver of cable television network, which comprises two offset networks, a photoelectric detector and a variable attenuator. The photoelectric detector is grounded and connected with a power source via the two offset networks. The output terminal of the photoelectric detector is connected with an optical power detecting circuit, a logarithmic circuit, a phase inverting circuit, an exponential circuit, a phase proportion adjusting circuit and an adding circuit in sequence, and then is connected with the variable attenuator, thereby achieving the automatic gain control (AGC). The circuit is implemented by use of the pure analog hardware, and can control the input light power in the range above 10dB, namely, the radio-frequency output level in the range above 20dB.
Description
Technical field
The present invention relates to be applied to the circuit of the optical receiver of cable TV network, more particularly, relate to the light control automatic gain control circuit of optical receiver.
Background technology
No matter be traditional Hybrid Fiber and Coax Network HFC (HFC), the still FTTC (Fiber To The Curb), the FTTB that are progressively advancing of present operator (Fiber-To-The-Building) and FTTH (Fiber to the home) network, the transmission of signal all needs big dynamic range.Usually, for network design, wish to receive stable level at user side, therefore, network design need be carried out level and controlled, and no matter is manually or automatic.
For traditional hfc plant, the reception dynamic range of general optical node just designs lessly when network design, general design receives at-1dBm, and the covering number of users of single optical node is bigger on optical distribution network, therefore the quantity of optical node is compared the FTTX network seldom, for this optical node product, generally be not design automatic gain control (AGC), but there is pluggable fixed attenuator the product the inside, can manually select attenuator to carry out level control, this control is exactly manual gain control (MGC).
Application for radio and television 1550nm optical transmission FTTx, Access Network adopts 1550nm transmitter+EDFA to carry out the luminous power distribution, the optical node coverage is more and more littler, generally about 50 families, therefore need to consume a large amount of luminous powers, at this moment need to use a large amount of EDFA, splitter and connector on the network, because the diversity that user's space distributes and the uncertainty and the changeability of optical link power budget, optical power loss may have bigger difference.At this moment the received optical power that is reflected at optical node and is the different location differs bigger.This moment the receiver One's name is legion on the optical-fiber network, we can simply calculate, for the network at one 100,000 family (scale at a general medium prefecture-level city or county town), if the optical node in 50 families then needs 2000 of optical receivers! If the optical receiver that uses does not have the AGC function, the workload of engineering deployment and maintenance will be huge so.When disposing the FTTX network, be starved of optical receiver with wide optical dynamic range.
As Fig. 1, at present the agc circuit that generally uses is based on the closed-loop control system of RF power detection, and directional coupler is coupled to signal deteching circuit with a part of signal, and the output signal of signal deteching circuit comprises its agc circuit of automatically controlled decay through handling to give.The method of the pure analog circuit of usefulness that the Signal Processing process has, what have realizes with mcu programming.When the signal of level detector detection hanged down than the reference signal of AGC controll block, AGC just reduced attenuation, increases output; On the contrary, when the signal that detects when level detector was higher than the reference signal of AGC controll block, AGC just increased attenuation, reduces output.Like this, AGC controll block is constantly adjusted attenuation, makes the output radio frequency level keep constant in the input excursion of expection.There is more shortcoming in this control mode, at first needs directional coupler, makes output signal produce extra loss, and 1dB is arranged usually.Input generally needs higher driving radio frequency level, adds post amplifier possibly behind coupler, perhaps also useful integrated input chip, all increased cost in a word.Secondly the control range of this control mode is narrower, generally can be controlled preferably in the RF of 10dB scope, and corresponding reference optical power has only 5dB, and seems a bit complicated in the control, and component parameters is chosen improper, can produce stability problem.
Other has a kind of AGC design such as Fig. 2, controls output level by detecting luminous power.Can make luminous power to photo-detector and detect, be output as the direct voltage linear with luminous power, this information is input to single-chip microcomputer, single-chip microcomputer is controlled voltage-controlled attenuator by DA.As everyone knows, at the optical transmitter end, multi-carrier signal carries out intensity modulated to light source with linear mode.At receiver end, during no AGC, the corresponding relation of output level and received optical power is that received optical power changes 1dB, and output level changes 2dB in the same way.So, follow light during design and increase 1dB, the voltage-controlled attenuator decay increases the principle of 2dB, then can obtain perfect AGC control.This shows that this design logic is very clear, key is the algorithm on the signal processing.The shortcoming of this mode is to carry out mould-number, the conversion of number-mould, the crystal oscillator frequency that single-chip microcomputer is used is generally several MHz to tens MHz, and be square wave, has broad harmonic spectrum, from tens MHz to hundreds of MHz, being very easy to produce radiated interference, therefore is an interference source that makes us the ten minutes headache.The AGC of wide control range and high control precision has relatively high expectations to the control precision of A/D, and if digital control generation disturb, will be very difficult to eliminate.
Summary of the invention
The objective of the invention is to defective, a kind of light control automatic gain control circuit that is applied to cable television network optical receiver is provided at the prior art existence.The present invention can reach desirable AGC control to 10dB input optical power excursion, and the output level vary stable that makes optical receiver is within 1dB.
For achieving the above object, the present invention adopts following technical proposals:
A kind of light control automatic gain control circuit that is applied to cable television network optical receiver comprises biasing networks, photoelectric detector, biasing networks and variable attenuator, it is characterized in that:
(1) described photoelectric detector respectively by biasing networks and biasing networks ground connection be connected power supply, and biasing networks output connects;
(2) luminous power testing circuits detect Output optical power, and it exports connection;
(3) logarithmic circuits are done the logarithm computing to the output of luminous power testing circuit 23, and it exports connection;
(4) negative circuits are reversed to the output voltage of logarithmic circuit 24, and it exports connection;
(5) exponent circuit are done the logarithm computing to the output of negative circuit 25, and it exports connection;
(6) in-phase proportions are adjusted circuit, and the output of exponent circuit 26 is adjusted, and it exports connection;
(7) add circuits, an output and a reference voltage signal of in-phase proportion being adjusted circuit 27 carry out add operation, and it exports connection;
(8) described variable attenuator is finished AGC control.
Logarithmic circuit in the above-mentioned control circuit has adopted two operational amplifiers, two triodes to do the logarithm calculus of differences, and used reference voltage signal.Exponent circuit wherein has the structure identical with logarithmic circuit.
What signal processing of the present invention adopted is pure analog hardware circuit, compared with the prior art, has conspicuous outstanding advantage: need not to increase extra CPU and control, control stabilization is reliable, be difficult for producing and disturb, debugging is simple, can control the input optical power of the above scope of 10dB, i.e. the radio frequency output level of the above scope of 20dB.Really, light AGC can't make response to the variation of optical transmitter OMI (optical modulation index), but now the transmitter produced of different manufacturers the OMI difference little, even the difference that the optical transmitter of 1310nm and 1550nm, the difference of its OMI are reflected on the output level of receiver generally is no more than 2dB.For the variation of the amplifier gain that causes owing to variation of temperature, can adapt to open-air operational environment easily to the reference signal design temperature compensation function at the AGC control end.
Description of drawings
Fig. 1 is a kind of radio frequency AGC design circuit schematic diagram of prior art.
Fig. 2 is a kind of smooth AGC design circuit schematic diagram of prior art.
Fig. 3 is the light agc circuit theory diagram of a kind of novelty of adopting of the present invention.
Fig. 4 is the circuit diagram of the voltage-controlled attenuator that adopts of the present invention.
Fig. 5 is the iamge description of AGC control voltage and input optical power functional relation.
Fig. 6 is the logarithmic circuit in the AGC control section.
Fig. 7 is the exponent circuit in the AGC control section.
Embodiment
A preferred embodiment of the present invention accompanying drawings is as follows:
Referring to Fig. 3, should be used for the light control automatic gain control circuit of cable television network optical receiver, comprise biasing networks 20, photoelectric detector 21, biasing networks 22 and variable attenuator 31; (1) described photoelectric detector 21 is respectively by biasing networks 22 and biasing networks 20 ground connection with is connected power supply, and biasing networks 22 is exported connection; (2) luminous power testing circuits 23 detect Output optical power, and it exports connection; (3) logarithmic circuits 24 are done the logarithm computing to the output of luminous power testing circuit 23, and it exports connection; (4) negative circuits 25 are reversed to the output voltage of logarithmic circuit 24, and it exports connection; (5) exponent circuit 26 are done the logarithm computing to the output of negative circuit 25, and it exports connection; (6) in-phase proportions are adjusted circuit 27, and the output of exponent circuit 26 is adjusted, and it exports connection; (7) add circuits 28, an output and a reference voltage signal of in-phase proportion being adjusted circuit 27 carry out add operation, and it exports connection; (8) described variable attenuator 31 is finished AGC control.
The instantiation of above-mentioned variable attenuator 31 is seen Fig. 4, circuit structure for a kind of voltage-controlled attenuator commonly used, its component parameters sees Table 1, used core devices is the PIN diode HSMP-3814 of Agilent company, the characteristic of this diode is equivalent to the resistance of Current Control, promptly change electric current by diode, the high-frequency resistance of diode has bigger variation, when the electric current by this diode during from 10mA to 0.01mA, its high-frequency resistance changes to thousands of ohm from several ohm, and the variation relation of impedance variation and electric current almost is linear.Therefore utilize the peripheral resistance capacitance components and parts of it and some can constitute ∏ type attenuator.V+ is a reference voltage, Vc is control voltage, when Vc changes, voltage on resistance R 102, the R103 also and then changes, electric current by D104, D105, D106, D107 is also changing simultaneously so, the parameter of choose reasonable peripheral components can guarantee the impedance stabilization of attenuator in whole attenuation range, reflect to remain on-below the 18dB.Voltage-the attenuation characteristic of test attenuator can obtain one group of correspondence table of controlling voltage and pad value.The received optical power scope of needs when using according to optical receiver then, the corresponding attenuation range of formulating an attenuator, can determine 1 attenuation points every 1dB, simultaneously corresponding control voltage so just can obtain the correspondence table of the control voltage of luminous power and voltage-controlled attenuator.1 example sees Table 2.
Table 1
Table 2
The corresponding decay of input optical power (dBm) AGC control voltage (V) (dB)
-10 3.7 3
-9 2.96 5
-8 2.56 7
-7 2.32 9
-6 2.14 11
-5 1.96 13
-4 1.79 15
-3 1.67 17
-2 1.58 19
-1 1.52 21
0 1.47 23
The corresponding relation of his-and-hers watches 2 credit of counting is now analysed, and existing its described point is become function curve, sees Fig. 5.Observe curve, find that it and exponential function curve are very alike.Suppose that now it is an exponential function, expression formula is
V＝a＊10
-Po/10+b (0)
Wherein P0 represents with dBm to be the received optical power of unit.Can determine constant a and b with the method for undetermined coefficients, promptly obtain two equations, solve a and b with two points of minimum and maximum input optical power.Can give counterevidence then, find optical power value of input arbitrarily, the AGC departure can remain within the 1dB basically, generally can remain within the 0.5dB, therefore can think that this quantitative relation is very accurately.
We know, are that the luminous power P0 of unit is expressed as 10 with mw with dBm
Po/10, so the luminous power detection signal can be expressed as k*10
Po/10, in Fig. 3, biasing networks (22) can come monitoring optical power with the resistance of m*1000 (span of m be 1～3 more suitable) ohm, and optical power monitoring (23) can be realized with voltage follower, can obtain luminous power detection signal k*10 like this
Po/10Then P0 is parsed, need be by logarithmic circuit, as Fig. 6, be the logarithmic circuit of the great dynamic range that utilizes the triode structure, component parameters sees Table 3
Table 3
| Resistor ohm | Capacitor NF | Other |
| R200 500k R201 500k R202 500k R203 15.7k R204 1k R205 500k R206 2k | C200 1 C201 1 C202 10 | Q200 9013 Q201 9013 U200 LM324 |
The output of logarithmic circuit is the function of the base voltage difference of two triodes,
EOUT＝((R203+R204)/R204)*(VBEQ201-VBEQ200) (1)
Utilize the PN junction equation, can obtain
ΔVBE＝(kT/q)*log
e(IC200-IC201) (2)
Wherein k is a Boltzmann constant, and T is a kelvin degree, and q is an electron charge, and therefore (1) formula can turn to
EOUT＝(-kT/q)*((R203+R204)/R204)*log
e((EIN*R205)/(EREF*R200)) (3)
Therefore notice the function that is output as temperature, if use logarithmic circuit separately, need do temperature-compensating, R204 needs the serviceability temperature coefficient to be+3500ppm/ ℃ thermistor, and variation that can compensation temperature is to the influence of output, and (3) formula can turn at this moment
E
OUT＝-[1g(|E
IN|/R
200)+5]
＝0.7-1g|E
IN|
＝0.7-1g(k＊10
Po/10) (4)
Then, the output result of logarithmic circuit is input in the negative circuit (25) obtains
E1＝-E
OUT＝1g(k＊10
Po/10)-0.7 (5)
Need below E1 is input in the exponent circuit (26), see Fig. 7, its principle is the same with the logarithmic circuit of Fig. 6, and also the same substantially on the structure, its component parameters sees Table 4
Table 4
| Resistor ohm | Capacitor NF | Other | |
| R300 500k R301 500k R302 2k R303 10k R304 15.7k R305 10k | C200 | 1 |
Q300 9013 Q301 9013 U300 LM324 |
This exponent circuit has following quantitative relation
E
2＝(1/10)＊10
-E1 (6)
Logarithmic circuit has identical structure with exponent circuit, symmetry on the circuit is very good, their calculating process just is opposite, output variable is temperature sensitive in the single circuit, but two uses that combine, because the symmetry of circuit, their temperature characterisitic is just opposite, therefore almost it doesn't matter with temperature in whole output, so R204 and R306 do not need to use thermistor, and in fact temperature coefficient is+buying of 3500ppm/ ℃ thermistor inconvenience extremely.
With (5) formula substitution (6) formula, can get
E2＝(1/2k)＊10
-Po/10 (7)
Then E2 is input to in-phase proportion circuit (27), adjusts coefficient 1/2k, be output as E3, can obtain so with potentiometer
E3＝a＊10
-Po/10 (8)
Solved the problem that parameter k can be subjected to the conforming influence of responsiveness of photo-detector so simultaneously.
Then E3 is input to add circuit (28), reference quantity is b, is output as E4, just can obtain the result that target (0) is wanted,
E4＝a＊10
-Po/10+b (9)
B does temperature-compensating to parameter, but the gain temperature characterisitic of pair amplifier compensate, stable control output under wider temperature range is to adapt to open-air condition of work.
E4 is the control signal of AGC, is added to variable attenuator (31), the control of the automatic gain that just can realize ideal.
More than used component parameters just at an example, may revise some parameter by needs according to different designing requirements in the practical application.
Claims (3)
1. a light control automatic gain control circuit that is applied to cable television network optical receiver comprises biasing networks (20), photoelectric detector (21), biasing networks (22) and variable attenuator (31), it is characterized in that:
A. described photoelectric detector (21) is respectively by biasing networks (22) and biasing networks (20) ground connection be connected power supply, and biasing networks (22) is exported connection;
B. a luminous power testing circuit (23) detects Output optical power, and it exports connection;
C. a logarithmic circuit (24) is done the logarithm computing to the output of luminous power testing circuit 23, and it exports connection;
D. a negative circuit (25) is reversed to the output voltage of logarithmic circuit 24, and it exports connection;
E. an exponent circuit (26) is done the logarithm computing to the output of negative circuit 25, and it exports connection;
F. an in-phase proportion is adjusted circuit (27), and the output of exponent circuit 26 is adjusted, and it exports connection;
G. an add circuit (28), an output and a reference voltage signal of in-phase proportion being adjusted circuit 27 carry out add operation, and it exports connection;
H. described variable attenuator (31) is finished AGC control.
2. the optical receiver light control automatic gain control circuit that is applied to cable TV network according to claim 1, it is characterized in that, used logarithmic circuit (26) has adopted two operational amplifiers, two triodes to do the logarithm calculus of differences, and used reference voltage signal.
3. the optical receiver light control automatic gain control circuit that is applied to cable TV network according to claim 1, it is characterized in that, used exponent circuit has and logarithmic circuit symmetrical structure form, same two operational amplifiers, two triodes of using are done the logarithm calculus of differences, and have been used reference voltage signal.
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| CNA2008102040046A CN101478344A (en) | 2008-12-04 | 2008-12-04 | Light control automatic gain control circuit applied on cable television network optical receiver |
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101610403B (en) * | 2009-07-21 | 2011-01-12 | 陈苏南 | Remote monitoring and controlling type optical receiver |
| CN102045551A (en) * | 2010-12-30 | 2011-05-04 | 常熟市高事达光电科技有限公司 | Radio frequency optical fiber transmission optical workstation for two-way network transformation of cable television |
| CN102088318A (en) * | 2010-12-16 | 2011-06-08 | 四川九州电子科技股份有限公司 | Optical AGC control circuit and attenuation value acquisition method thereof |
| CN102130724A (en) * | 2010-12-30 | 2011-07-20 | 常熟市高事达光电科技有限公司 | Light automatic gain control circuit used for cable TV network optical receiver |
| CN102387355A (en) * | 2011-10-26 | 2012-03-21 | 常熟市高事达光电科技有限公司 | Single chip controlled optical automatic gain control circuit of cable TV (television) network optical receiver |
| CN103326704A (en) * | 2013-06-24 | 2013-09-25 | 杭州电子科技大学 | Magnetic control memristor equivalent circuit |
| CN103516321A (en) * | 2012-06-29 | 2014-01-15 | 联想(北京)有限公司 | Power attenuation circuit and closed loop power control circuit |
| CN104506242A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | AGC (automatic gain control) control method for management type household optical receiving machine |
| CN104506244A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | AGC (automatic gain control) control circuit for management type household optical receiving machine |
| CN104506245A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | ATT control method for management type household optical receiving machine |
| CN104730310A (en) * | 2013-12-24 | 2015-06-24 | 苏州普源精电科技有限公司 | Measuring device with variable attenuation unit |
| CN107332536A (en) * | 2017-07-03 | 2017-11-07 | 重庆西南集成电路设计有限责任公司 | It is a kind of precisely to debug the temperature-compensation circuit and method of gain |
| CN113219828A (en) * | 2021-04-22 | 2021-08-06 | 中国电子科技集团公司第二十九研究所 | Control method for gain consistency of multi-channel analog optical module |
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2008
- 2008-12-04 CN CNA2008102040046A patent/CN101478344A/en active Pending
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101610403B (en) * | 2009-07-21 | 2011-01-12 | 陈苏南 | Remote monitoring and controlling type optical receiver |
| CN102088318A (en) * | 2010-12-16 | 2011-06-08 | 四川九州电子科技股份有限公司 | Optical AGC control circuit and attenuation value acquisition method thereof |
| CN102130724B (en) * | 2010-12-30 | 2014-01-15 | 常熟市高事达光电科技有限公司 | Light automatic gain control circuit used for cable TV network optical receiver |
| CN102045551A (en) * | 2010-12-30 | 2011-05-04 | 常熟市高事达光电科技有限公司 | Radio frequency optical fiber transmission optical workstation for two-way network transformation of cable television |
| CN102130724A (en) * | 2010-12-30 | 2011-07-20 | 常熟市高事达光电科技有限公司 | Light automatic gain control circuit used for cable TV network optical receiver |
| CN102045551B (en) * | 2010-12-30 | 2012-07-25 | 常熟市高事达光电科技有限公司 | Radio frequency optical fiber transmission optical workstation for two-way network transformation of cable television |
| CN102387355A (en) * | 2011-10-26 | 2012-03-21 | 常熟市高事达光电科技有限公司 | Single chip controlled optical automatic gain control circuit of cable TV (television) network optical receiver |
| CN103516321A (en) * | 2012-06-29 | 2014-01-15 | 联想(北京)有限公司 | Power attenuation circuit and closed loop power control circuit |
| CN103516321B (en) * | 2012-06-29 | 2016-03-30 | 联想(北京)有限公司 | A kind of power attenuation circuit and close-loop power control circuit |
| CN103326704A (en) * | 2013-06-24 | 2013-09-25 | 杭州电子科技大学 | Magnetic control memristor equivalent circuit |
| CN104730310A (en) * | 2013-12-24 | 2015-06-24 | 苏州普源精电科技有限公司 | Measuring device with variable attenuation unit |
| CN104506242A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | AGC (automatic gain control) control method for management type household optical receiving machine |
| CN104506244A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | AGC (automatic gain control) control circuit for management type household optical receiving machine |
| CN104506245A (en) * | 2014-12-25 | 2015-04-08 | 四川璧虹广播电视新技术有限公司 | ATT control method for management type household optical receiving machine |
| CN104506242B (en) * | 2014-12-25 | 2018-02-06 | 向祖璧 | A kind of AGC control methods of management type family expenses photoreceiver |
| CN107332536A (en) * | 2017-07-03 | 2017-11-07 | 重庆西南集成电路设计有限责任公司 | It is a kind of precisely to debug the temperature-compensation circuit and method of gain |
| CN113219828A (en) * | 2021-04-22 | 2021-08-06 | 中国电子科技集团公司第二十九研究所 | Control method for gain consistency of multi-channel analog optical module |
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