CN102347742B - 1kFtADSL (1kFt Asymmetrical Digital Subscriber Loop) signal attenuation circuit - Google Patents

1kFtADSL (1kFt Asymmetrical Digital Subscriber Loop) signal attenuation circuit Download PDF

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CN102347742B
CN102347742B CN201110158692.9A CN201110158692A CN102347742B CN 102347742 B CN102347742 B CN 102347742B CN 201110158692 A CN201110158692 A CN 201110158692A CN 102347742 B CN102347742 B CN 102347742B
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inductance
resistance
adsl
1kft
node
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CN102347742A (en
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刘德银
江惠秋
王志波
汪澜
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Shenzhen Gongjin Electronics Co Ltd
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Shenzhen Gongjin Electronics Co Ltd
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Abstract

The invention provides a 1kFtADSL (1kFt Asymmetrical Digital Subscriber Loop) signal attenuation circuit composed of ten order difference signal filtering circuits connected in series, wherein each order difference signal filtering circuit comprises a first inductor, a first resister, a second resister and a second inductor connected in parallel and a node A which are connected in series, and a third inductor, a third resister, a fourth resister and a fourth inductor connected in parallel and a node B which are connected in series; a capacitor is connected in series between the node A and the node B; the first/third inductor of the first-order difference signal filtering circuit is also connected with the positive pole/negative pole of an ADSL signal input terminal; the first/third inductors of the second- to the tenth-order difference signal filtering circuits are also connected with the nodes A/B of the previous order difference signal filtering circuit; and the node A/B of the tenth-order difference signal filtering circuit is connected with the positive pole/negative pole of the ADSL signal output terminal. The invention is equivalent to realize the purpose of ADSL signal attenuation by a 1kFt telephone line, thus saving the production cost and being easy to realize.

Description

A kind of 1kFt ADSL signal attenuation circuit
Technical field
The present invention relates to the rate test technical field of ADSL product, more particularly, to a kind of 1kFt being applied to rate test ADSL signal attenuation circuit.
Background technology
At present, DSL (Digital Subscriber Line), i.e. digital subscriber line, is to be situated between with copper telephone wire for transmission The point-to-point transmission technology of matter.DSL technology is supported symmetrical and asymmetric on the local loop of traditional telephone network (POTS) Transmission mode, solves and frequently occurs in the transmission bottleneck of " last one kilometer " between Internet service provider and end user and ask Topic.Because telephone subscriber loop is laid in a large number, how to make full use of existing copper cable resource, real by copper twisted pair Existing high-peed connection just becomes the research emphasis of industry, and therefore DSL technology is paid attention to soon, and obtains in some countries and regions To extensive application.
The test of ADSL product is frequently necessary to test the connection speed under actual range, common measuring distance has 1kFt, 2kFt, 3kFt～19kFt, this kind of test main analog actual user can reach how many transmission speed under different distance Rate.The realization simulating different distance at present in ADSL product test has two kinds of implementation methods：1) buy the telephone wire of standard, point Become 1kFt, 2kFt, 3kFt～19kFt, then tested under different distance.2) to simulate difference by using special equipment Distance is being tested.However, above two implementation method respectively has pluses and minuses：The method tested using actual telephone wire Measurement result is accurate, but line length is it is not easy to switch over test under different distance；Advantage using special equipment is mainly side Just and automatization is high, but cost is particularly expensive, the equipment of a simple analog different length telephone wire needs RMB up to a million. Thus, it is necessory to propose a kind of new implementation method.
Content of the invention
It is an object of the invention to provide a kind of 1kFt ADSL signal attenuation circuit is equivalent realizes 1kFt length telephone wire Decay to ADSL signal, user can realize ADSL product under different distance by combining and cascading this elementary cell The test of connection speed, is easy to switch over test under different distance；
It is a further object of the present invention to provide a kind of 1kFt ADSL signal attenuation circuit, using basic inductance, resistance, The basic electronic devices and components such as electric capacity design, and substantially reduce production cost.
The purpose of the present invention is achieved through the following technical solutions.
A kind of 1kFt ADSL signal attenuation circuit, this circuit is composed in series by ten first-order difference signal filter circuits；
Described first-order difference signal filter circuit includes：First inductance, the second inductance, the 3rd inductance, the 4th inductance, first Resistance, second resistance, 3rd resistor, the 4th resistance and the first electric capacity；Wherein, described first inductance, first resistor, parallel connection after Second resistance and the second inductance, node A be sequentially connected in series；3rd inductance, 3rd resistor, parallel connection after the 4th resistance and the 4th electricity Sense, node B are sequentially connected in series；Also it is in series with the first electric capacity between described node A and node B；
For the first order difference signal filter circuit, the other end of its first inductance and ADSL signal input part positive pole phase Even, the other end of the 3rd inductance is connected with ADSL signal input part negative pole；For the second to the tenth order difference signal filter circuit, The other end of its first inductance is connected with the node A of front first-order difference signal filter circuit, the other end of the 3rd inductance with previous The node B of order difference signal filter circuit is connected；For the tenth order difference signal filter circuit, its node A connects to ADSL letter Number output head anode, node B connect to ADSL signal output part negative pole；
Also it is in series with high-frequency signal filter element, described ADSL signal between described ADSL signal input part positive pole and negative pole Also it is in series with impedance matching element between output head anode and negative pole.
Preferably, described high-frequency signal filter element is made up of two the second capacitances in series, described first electric capacity and second It is 1.5nF that electric capacity adopts capacitance, precision is ± 1pF, pressure voltage is 50V, material is the ceramic condenser of NP0.
Preferably, described impedance matching element adopts resistance is 100 Europe, precision is ± 1% the 5th resistance.
Preferably, described first inductance and the 3rd inductance adopt inductance value is 5.6uH, precision is that ± 2%, equivalent resistance is The wire-wound inductor in 1.95 Europe.
Preferably, the resistance of described first resistor and 3rd resistor be 1.87 Europe, precision be ± 1%.
Preferably, the resistance of described second resistance and the 4th resistance be 4.02 Europe, precision be ± 1%.
Preferably, described second inductance and the 4th inductance adopt inductance value is 1.2uH, precision is that ± 2%, equivalent resistance is The wire-wound inductor in 1.2 Europe.
Compared with prior art, the embodiment of the present invention has the advantages that：
By the present invention in that achieve equivalent 1kFt length telephone wire with basic electronic devices and components declining to ADSL signal Subtract, can achieve the ADSL signal under different distance in application by way of simple combination cascades attenuator circuit of the present invention Decay, can the quick and convenient switch test realizing the connection speed to ADSL product exactly, solve application actual phone The loaded down with trivial details problem of wiring brought when line is tested, and saved production cost, improve production efficiency.
Brief description
Fig. 1 is the performance plot that attenuation amplitude and phase place are with respect to frequency；
Fig. 2 is the Cauer type electronic circuit graph model of k rank Butterworth filter；
Fig. 3 is first-order difference signal attenuation circuit figure in the embodiment of the present invention；
Fig. 4 is 1kFt ADSL signal attenuation circuit figure in the embodiment of the present invention；
Fig. 5 be can achieve 1～19kFt different distance under ADSL signal attenuation realize schematic diagram.
Specific embodiment
In order that the objects, technical solutions and advantages of the present invention become more apparent, below in conjunction with drawings and Examples, right The present invention is further elaborated.It should be appreciated that specific embodiment described herein is only in order to explain the present invention, and It is not used in the restriction present invention.
Not only there is due to bandwidth filter the function that the signal outside to certain limit bandwidth is isolated, also have to one Determine the function that the signal in bandwidth range is decayed, thus using the attenuation to specific bandwidth range signal, from conjunction Suitable filter model can be designed and be equivalent to the attenuator circuit that 1kFt length telephone wire acts on to ADSL signal attenuation.
The core concept of the present invention is：Different frequency signals can be decayed using the algorithm device that LRC is set up Principle, is designed using the basic electronic devices and components such as basic inductance, resistance, electric capacity, switch and realizes ADSL signal attenuation electricity Road elementary cell, this unit is equivalent to realize the decay to ADSL signal of the telephone wire of 1kFt length.Then, by the group of the present invention Close the decay that cascade ADSL signal attenuation circuit elementary cell can achieve different distance under 1～19kFt.
The scope of the operating frequency of ADSL signal is 25.875kHz～1.04MHz, according to the universal standard of ADSL TR0671kFt need to select rational filter model in the attenuation requirement of each frequency, the present invention, using simulation software to model or Circuit parameter is calculated, then design side circuit and with frequency device enter test comparison can reach emulation and standard will Ask.
The design process of 1kFt ADSL signal attenuation circuit in the embodiment of the present invention will be described according to the following step below.
1) attenuation requirement according to TR067 standard chooses rational Filtering Model.
Knowable to following table one is analyzed, the attenuation requirement of ADSL signal be as frequency requirement make linear change it is impossible to Occur rising and falling.And only have Butterworth filter in Chebyshev filter, Butterworth filter, elliptic filter model Frequency response curve in passband is flat to greatest extent, does not rise and fall, and being then gradually reduced in suppressed frequency band is zero.Such as scheming On the Bode diagram of logarithm diagonal frequencies of the amplitude shown in 1, from the beginning of the angular frequency of a certain border, amplitude is with the increase of angular frequency And gradually reduce, the feature tending to minus infinity meets the requirements, as Chebyshev filter occurs bad phenomenon of fluctuating Do not comply with requirement.Therefore the present invention chooses Butterworth filter model.
Table one
2) exponent number of selecting filter
The attenuation rate of single order Butterworth filter is 6 decibels of every frequency multiplication, 20 decibels of every ten frequency multiplication；Second order Butterworth is filtered The attenuation rate of ripple device is 12 decibels of every frequency multiplication；The attenuation rate of three rank Butterworth filters is 18 decibels of every frequency multiplication, and so on. The amplitude diagonal frequencies monotonic decreasing of Butterworth filter, and be also that uniquely no matter exponent number is how many, amplitude is to angular frequency Rate curve all maintains like the wave filter of shape.Only filter order is higher, faster in the suppressed frequency band amplitude rate of decay.Its His amplitude diagonal frequencies figure of wave filter high-order and the amplitude diagonal frequencies of harmonic series have different shapes.To determine how below Exponent number of the presently claimed invention is realized in selection.
Its transmission function：
Wherein, the exponent number of n=wave filter, wc=cut-off frequency=amplitude drops to frequency when -3 decibels, wp=passband Marginal frequency, 1/ (1+ ε2)=| H (w) |2Numerical value in passband belt edge.
| H (w) | on two-dimentional complex plane2=H (s) H* (s)=H (s) H (- s) is in numerical value=| the H (w) | of s=jw point2, because This passes through analytical continuation：
It is w that the limit of above-mentioned function is distributed at radiuscCircle on
- s 2 w c 2 = ( - 1 ) 1 n = e j ( 2 k + 1 ) π n , k = 0 , 1 , 2 , ..... , n - 1
Therefore,
The amplitude of n rank Butterworth LPF and frequency relation can be represented with formula below：
G n ( w ) = | H n ( j w ) | = 1 1 + ( w / w c ) 2 n
Wherein, G represents the amplification of wave filter, and H represents transfer function, and j is imaginary unit, and n represents the series of wave filter, W is the angular frequency (in units of radian per second) of signal, wcIt is the cut-off frequency that amplitude declines when 3 decibels；
Make cut-off frequency wc1, above-listed formula normalization is become：
G n ( w ) = | H n ( j w ) | = 1 1 + w 2 n
Seek the exponent number of wave filter according to the dough softening
Make 1/A=Gn(w)
When choosing w=2, Gn(w)=0.004
A=200, n=9.6, take bigger integer, the therefore exponent number of the present embodiment median filter is 10.
3) calculating of circuit parameter and selection
The Cauer type electronic circuit graph model of k rank Butterworth filter as shown in Fig. 2
Through composition Cauer type algorithm circuit, it is output as Vout to signal Vin, and its transmission function is：
K ( S ) = K 0 w 0 2 S 2 + αw 0 S + w 0 2
Wherein R1 and L2 parallel connection is to form the attenuation quotient of RC algorithm device to increase its impedance and C2, because typically electric Sense its internal resistance of L2 only has tens bold and unconstrained Ou Wufa to meet decay.
Parameter calculates：
When R11=1.87 Europe,
R1=2.15R11=2.15*1.87 Europe=4.0205 Europe, the resistance taking probability is R1=4.02 Europe；
(exponent number of wave filter selected by k=), calculates C2=3.0nF；
Calculate L1=5.6uH, L11=L1/ 4.7=1.2uH.
4) conversion of ADSL differential signal attenuator circuit and parameter confirm
Because circuit shown in Fig. 2 is for general analogue signal is to design, and used during ADSL signal transmission be mould The differential signal intended.So this step is converted into difference channel.General analogue signal is as a reference point with GND, and The positive and negative of differential signal may be referred to central point or equivalent coming respectively respectively as reference point.The equivalent single order ADSL obtaining is poor Sub-signal wave filter is as shown in figure 3, the C2 after wherein equivalent should subtract because capacitances in series is equivalent to capacitance in the half of original C2 Half.
5) 1kFt ADSL signal attenuation circuit
As it was previously stated, the present invention needs ten rank ADSL differential signal filter circuits to realize, obtain due in upper step Single order ADSL differential signal filter circuit, then only need to connect ten single order ADSL differential signal filter circuits in this step Come, along with impedance matching and high-frequency signal filtering electronic components and parts, you can obtain final 1kFt ADSL signal attenuation electricity Road, as shown in Figure 4.When applying this circuit, the positive and negative first-order filtering electricity being formed by figure 3 above respectively of ADSL analog difference signal Reach bis- nodes of A, B after the decay of road, enter back into the same filter circuit of lower single order, so pass sequentially through ten such single orders Filter circuit.
Wherein R=100 Europe is used for being used as the coupling of ADSL analog difference signal, and precision is 1%；
C1, C5 are used for the filtering more than 1.2MHz signal；
C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12 be capacitance 1.5nF, the positive and negative 1pF of precision,
Pressure voltage is 50V, material is the ceramic condenser of NP0；
L1, L3, L5, L7, L9, L11, L13, L16, L18, L20, L23, L25, L27, L29, L31, L33, L35, L37 are Inductance value 5.6uH, precision ± 2%, equivalent resistance are the wire-wound inductor in 1.95 Europe；
L2, L4, L6, L8, L10, L12, L14, L15, L17, L19, L21, L22, L24, L26, L28, L30, L32, L34, The wire-wound inductor that L36, L38 are inductance value 1.2uH, precision ± 2%, equivalent resistance are 1.2 Europe；
R1, R2, R3, R10, R11, R12, R13, R14, R15, R16, R25, R26, R27, R28, R29, R30, R31, R39, The resistance of R40, R41 is 4.02 Europe, precision is ± 1%；
R4, R5, R6, R7, R8, R9, R17, R18, R19, R20, R21, R22, R23, R24, R32, R33, R34, R36, R37, R38 resistance is 1.87 Europe, precision is ± 1%；
The resistance of R35 is 100 Europe, precision is ± 1%.
6) PCB design of 1kFt ADSL signal attenuation circuit
Circuit theory diagrams according to Fig. 4, have chosen the parameter of electronic devices and components and have carried out device encapsulation, set with PCB The meter final printed circuit board of tool design, then produces the PCB Gerber file of standard；PCB factory may finally be dealt into Family is made.
7) checking of side circuit, test and conclusion
PCB is gone out according to actual design, then model is carried out with S21 parameter testing and the ADSL product of actual telephone wire connects Rate test.Carried out with audiofrequency spectrometer after S21 parameter testing, the requirement of contrast table one sees if there is larger difference, test result It is shown in Table two；Then carry out in the actual environment ADSL product under 1kFt telephone wire and attenuating plate connection speed test right Test result is shown in Table three to ratio.Can show that from table two the 1kFt attenuating plate of the present embodiment design is more slightly larger than standard, but symbol Close and require.Actual ADSL product is the same with the effect of 1kFt attenuating plate in 1kFt telephone wire respectively as can be seen from Table III. Conclusion：1kFt ADSL signal attenuation circuit of the present invention is fully equivalent to be acted in actual telephone wire.
Table two
Table three
To sum up, the connection speed test of ADSL product can adopt the 1kFt ADSL signal attenuation circuit of the present invention to come in fact Existing, addressed below its realizes process：Realize 2kFt, 4kFt, 8kFt decay mode with 1kFt ADSL signal attenuation circuit respectively Block, then passes through switch combination and superposition just can realize 1～19kFt different distance, and it realizes structured flowchart as shown in Figure 5, ADSL attenuator can be done according to this theory structure block diagram, such product can be used for the production with adsl feature product in batches In test.
The foregoing is only presently preferred embodiments of the present invention, not in order to limit the present invention, all essences in the present invention Any modification, equivalent and improvement made within god and principle etc., should be included within the scope of the present invention.

Claims (7)

1. a kind of 1kFt ADSL signal attenuation circuit is it is characterised in that this circuit is by ten first-order difference signal filter circuit strings Joint group becomes；
Described first-order difference signal filter circuit includes：First inductance, the second inductance, the 3rd inductance, the 4th inductance, the first electricity Resistance, second resistance, 3rd resistor, the 4th resistance and the first electric capacity；Wherein, described first inductance, first resistor, parallel connection after Second resistance and the second inductance, node A are sequentially connected in series；3rd inductance, 3rd resistor, parallel connection after the 4th resistance and the 4th electricity Sense, node B are sequentially connected in series；Also it is in series with the first electric capacity between described node A and node B；
For the first order difference signal filter circuit, the other end of its first inductance is connected with ADSL signal input part positive pole, The other end of three inductance is connected with ADSL signal input part negative pole；For the second to the tenth order difference signal filter circuit, it The other end of one inductance is connected with the node A of front first-order difference signal filter circuit, the other end of the 3rd inductance and previous jump The node B of sub-signal filter circuit is connected；For the tenth order difference signal filter circuit, its node A connects defeated to ADSL signal Go out proper pole, node B connects to ADSL signal output part negative pole；
Also it is in series with high-frequency signal filter element, described ADSL signal output between described ADSL signal input part positive pole and negative pole Also it is in series with impedance matching element between proper pole and negative pole.
2. 1kFt ADSL signal attenuation circuit as claimed in claim 1 is it is characterised in that described high-frequency signal filter element It is made up of two the second capacitances in series, it is 1.5nF that described first electric capacity and the second electric capacity adopt capacitance, precision is ± 1pF, pressure Being worth for 50V, material is the ceramic condenser of NP0.
3. 1kFt ADSL signal attenuation circuit as claimed in claim 1 is it is characterised in that described impedance matching element adopts Resistance is 100 Europe, precision is ± 1% the 5th resistance.
4. 1kFt ADSL signal attenuation circuit as claimed in claim 1 it is characterised in that described first inductance and the 3rd electricity It is 5.6uH that sense adopts inductance value, precision is the wire-wound inductor that ± 2%, equivalent resistance is 1.95 Europe.
5. 1kFt ADSL signal attenuation circuit as claimed in claim 1 it is characterised in that described first resistor and the 3rd electricity The resistance of resistance is 1.87 Europe, precision is ± 1%.
6. 1kFt ADSL signal attenuation circuit as claimed in claim 1 it is characterised in that described second resistance and the 4th electricity The resistance of resistance is 4.02 Europe, precision is ± 1%.
7. 1kFt ADSL signal attenuation circuit as claimed in claim 1 it is characterised in that described second inductance and the 4th electricity It is 1.2uH that sense adopts inductance value, precision is the wire-wound inductor that ± 2%, equivalent resistance is 1.2 Europe.
CN201110158692.9A 2011-06-14 2011-06-14 1kFtADSL (1kFt Asymmetrical Digital Subscriber Loop) signal attenuation circuit Expired - Fee Related CN102347742B (en)

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