CN1588966A - Method for detecting ADSC line parameter - Google Patents
Method for detecting ADSC line parameter Download PDFInfo
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- CN1588966A CN1588966A CN 200410080905 CN200410080905A CN1588966A CN 1588966 A CN1588966 A CN 1588966A CN 200410080905 CN200410080905 CN 200410080905 CN 200410080905 A CN200410080905 A CN 200410080905A CN 1588966 A CN1588966 A CN 1588966A
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Abstract
A test method for ADSL circuit parameter includes testing equivalent serial resistance of distributed resistance, equivalent capacitance of distributed capacitance of the two lines and the earth and the circuit parameter of equivalent capacitance connected between the two lines characterizing in including: connecting one of the tested lines to the earth, the other is serial to the test circuit and sending the exciting signal to the tested circuit and sampling it and the line access point to test the hybrid parameters of the tested circuit to the earth and between the two lines. Two lines of the tested line are short-circuit to access the test circuit and transfer the exciting signal to the tested circuit and sample the exciting signal and acc point to test the hybrid parameter to the earth of the tested to compute related circuit parameters.
Description
Technical field
The present invention relates to the method for testing of electronic communication circuit parameter, particularly relate to a kind of method of testing of adsl line parameter.
Background technology
Asymmetrical Digital Subscriber Line (ADSL, Asymmetric Digital Subscriber Line) is as the technology of a kind of high speed access Internet, and its application is becoming increasingly extensive.This technology adopts digital coding and modulation-demodulation technique to go up at user's copper twisted pair (ordinary telephone line) of routine and transmits broadband signal.
The main purpose of subscriber line test is to check copper cash to the transmittability of high-frequency signal (only carry out the ADSL business on the subscribers feeder of certain index meeting, could ensure the ADSL quality of service).Another target of subscriber line test is to determine that the ADSL business finally can offer client's service quality, typically refers to the highest up/downstream rate.In addition, test also should be able to cause the bad fault of circuit to qualitatively judge to some, so that get rid of.Subscribers feeder is tested, and mainly is the influence that the influencing factor of tests affect ADSL transfer of data causes.
The topmost factor that influences the ADSL transmission is a signal to noise ratio.ADSL is for the circuit of different quality in addition, and its performance also has bigger difference, transmits data on the copper twisted pair of existing longer distance, and the long more decay to signal of its transmission range is also serious more.The factor that causes signal attenuation is the insertion loss of circuit in the ADSL transmission band.Cause that the correlative factor of inserting loss mainly comprises line length, line inductance and bridge tap.Line length: the ADSL technology utilizes the high frequency characteristics of copper cash to carry out transfer of data, and copper cash is long more, and the decay of HFS is just big more.The longest representative value of circuit that can use the ADSL transmission is 4Km, and accurately the maximum length of transmission is decided according to copper cash specification, line conditions.Line inductance has very big decay to high-frequency signal, therefore should remove loading coil when opening the ADSL business.Bridge tap is to be connected across on the copper cash the not branch road circuit of usefulness, has certain power near the reflected signal on the bridge tap of ADSL Modem annex, may offset the useful signal pulse that transmits from far-end.Therefore, the user is when this type of business of application, and telecommunications company or Internet link service provider (ISP, InternetService Provider) must determine whether this user's copper cable possesses this type of professional ability of opening.Equally, in user's use, if when the not high situation of service disconnection or network connection quality takes place, telecommunications company or ISP also must determine to influence the factor of service operation.
In the prior art, the adsl line method of testing adopts Time Domain Reflectometry TDR or frequency domain reflection FDR technology.The method of Time Domain Reflectometry TDR technical testing is: TDR is being sent the high-frequency impulse test signal to test line by survey line centering, monitor signal is in this line right reflected phase will and intensity simultaneously, test event signal runs into the sudden change of an impedance by cable the time, then part or all of signal can reflect, TDR receives this reflected signal, and calculates the line parameter circuit value of this tested circuit according to time delay, size and the polarity of reflected signal.
The method of frequency domain reflection FDR technical testing is: FDR passes through to send the sweep check signal of special frequency band to tested circuit, this signal is in tested circuit transmission course, can produce at the Conductor Impedance place of not matching stronger with transmit same frequency but the reflected signal of different periods, FDR receives this reflected signal, and analyze this reflected signal, and converse the distance of circuitry obstacle point by the frequency that measures the reflected signal peaks value by the fourier transform mode.
Because TDR and FDR technology all are based on online to tested circuit transmission high frequency (pulse) signal, this signal produces reflected signal at the anti-change point of twisted-pair cable roadlock, by analyzing this reflected signal, calculate the line parameter circuit value of tested circuit, so this technology is applicable to pure line test, but for the good circuit of terminal impedance coupling, reflection just can not produce, TDR and FDR test will can not receive reflected signal, thereby can't test; When terminal is initiatively sent signal (ADSL modem can initiatively send handshake after powering on), the amplitude of signal has been flooded the reflected signal of TDR or FDR, thereby causes test inaccurate.Adopt the limitation of TDR or FDR measuring technology testing ADSL line very big like this.
In addition since TDR and FDR technology all launch the high-frequency impulse pumping signal and test, wherein the broadband noise test is directly to measure noise between the right line of tested twisted-pair feeder, as shown in Figure 1, test access point is gone into multiplexing equipment (DSLAM in distributing frame 210 drawn game terminations, Digital Subscriber Line AccessMultiplexer) between 220 built-in splitter 221, because the built-in low pass filter of separator, only allow signal is transferred to switch below 4300 hertz, so that stop the effect of high-frequency signal transmission to switch, so high-frequency signal can't be delivered on the circuit by the built-in splitter 221 of DSLAM 220 from exchanger side, and broadband noise can not pass to exchanger side by separator between the line of subscriber's line, so existing measuring technology all can only tested with artificial inserted mode or under the DSLAM of tape test bus environment between distributing frame and the local side separator, for the present DSLAM of a large amount of not tape test buses in usefulness, the mode that adopts the testing equipment of TDR or FDR technology all can not utilize existing switch to grab the line function is carried out the adsl line test.In this case, they can only adopt between DSLAM 220 and subscriber's line 230 and add the method for joining the relay line capture module, just can carry out pure broadband test, this mode brings serious problems to be to telecom operators: cost is too high, increase the fault point, increase management difficulty and maintenance difficulties.
To sum up analyzing as can be seen, prior art has the following disadvantages: the terminal of mating good circuit or initiatively signaling for terminal impedance in the prior art, TDR and the FDR measuring technology will can not receive signal reflex or reflected signal is interfered, thus the inaccurate defective of test caused.Moreover, for now in a large number at the DSLAM of the not tape test bus of usefulness, because the influence of DSLAM built-in splitter, the mode that existing ADSL broadband test device all can not utilize existing switch to grab the line function is carried out the adsl line parameter testing, thereby be difficult to carry out full-automatic line test, and then cause telecom operators to face existing adsl equipment situation difficult in maintenance.
Summary of the invention
For addressing the above problem, the invention provides a kind of adsl line method of testing, utilize this method can solve line parameter circuit value test and be not subjected to the interference of terminal type and state, and solved prior art and can not utilize switch to grab line functional test adsl line parameter and cause telecom operators to face having adsl equipment problem difficult in maintenance now.
For addressing the above problem, the invention provides a kind of adsl line parameter test method, be used to test equivalent string connecting resistance R1, the R2 of the distributed resistance that comprises two outside line a, b, article two, outside line a, b and equivalent capacity Cag, the Cbg of distributed capacitance on ground and the adsl line parameter that is connected two equivalent capacity Cab between outside line, this method comprises:
Respectively with wherein outside line ground connection of tested circuit, an other unearthed outside line serial connection test circuit, send pumping signal to tested circuit, described pumping signal and line access point are carried out signal sampling, measure the hybrid parameter over the ground and between line of tested circuit according to sampled result;
With two outside line short circuits of tested circuit, insert test circuit, send pumping signal to tested circuit, described pumping signal and line access point are carried out signal sampling, measure the hybrid parameter over the ground of tested circuit according to sampled result;
Utilize the data computation of above-mentioned parameter to go out corresponding line parameter circuit value.
This method also comprises: with two outside line short circuits, insert test circuit, test test line common mode noise signal over the ground; Common mode noise signal is sampled, calculate the common-mode noise power spectral density according to sampled result.
Wherein, described test circuit comprises signal generating unit and double A/D sampling unit, described signal generating unit produces pumping signal and gives the tested circuit that inserts, and described double A/D sampling unit carries out signal sampling to described pumping signal and line access point respectively simultaneously.
Wherein, described test circuit also comprises the noiselike signal amplifying unit, and described signal amplification unit is used for the signal of sampling is amplified.
Wherein, described pumping signal be frequency between 500 hertz to 3000 hertz, level is at sine below 2 volts or cosine wave.
Wherein, described pumping signal be frequency below 500 hertz, level is at sine below 2 volts or cosine wave.
Wherein, the hybrid parameter over the ground of described tested circuit is: the earth impedance value of real part R1 of tested circuit during outside line a ground connection, the earth impedance value of real part R2 of tested circuit during outside line b ground connection; Hybrid parameter is between the line of described tested circuit: the earth impedance value of real part R3 during tested line short circuit.
Wherein, the hybrid parameter over the ground of described tested circuit is: the direct-to-ground capacitance C1 of tested circuit during outside line a ground connection, the direct-to-ground capacitance C2 of tested circuit during outside line b ground connection; Hybrid parameter is between the line of described tested circuit: the direct-to-ground capacitance C3 during tested line short circuit.
Wherein, the described data computation of utilizing above-mentioned parameter goes out corresponding line parameter circuit value and specifically comprises:
Calculate the actual capacitance value of tested circuit: Cab=(C1+C2-C3)/2, Cag=(C1+C3-C2)/2, Cbg=(C2+C3-C1)/2;
Calculate tested Route Length: L=min (Cag, Cbg) * K, described K is an empirical coefficient;
When R1 ≈ R2, calculate the loop resistance of tested circuit: R1p=N * R3 * (1+Lg (L/M)); Described N, M are empirical coefficient;
Computational scheme inserts loss:
Described F is each sub-carrier frequencies of ADSL, and m, n, k, q are empirical coefficient.
Wherein, described test circuit comprises A/D sampling unit, processing unit DSP, programmable gain broadband amplifying unit, high input impedance broadband amplifying unit and circuit switch unit; Common mode noise signal by sampling unit A/D sampling, is delivered to processing unit DSP and is analyzed, and extracts the common-mode noise maximum, adjusts the amplifier gain value according to this maximum, makes the noise level of delivering to test circuit in suitable scope.
Wherein, the process of described test test line common-mode noise over the ground is specially: the test line of test frequency in 26 KHz to 1104 kilohertz range noise power spectral density data and longitudinal balance value over the ground.
Wherein, described process according to sampled result calculating common-mode noise power spectral density specifically comprises: the noise power spectral density data and the longitudinal balance value of test line are subtracted each other; Get difference.
Wherein, before test, also comprise: circuit is discharged.
Compared with prior art, the present invention has following beneficial effect: by test test line line parameter circuit value over the ground, avoided being connected subscribers feeder to the influence of user terminal; And because be connected on subscribers feeder to the characteristic and only online of the signal that they send of terminal form the loop, not have signal circuit over the ground, test the interference that is not subjected to terminal type and state so the present invention can realize line parameter circuit value.
The frequency of the pumping signal of method of testing of the present invention is below 3000 hertz the time in addition, can be smoothly high-pass and low-pass filter by the local side separator; Utilize the common-mode state of a line, b line short circuit that local side separator two line inductance are gripped altogether, offset the influence of separator inductance to greatest extent; The common-mode noise of subscribers feeder be actually the cable interior lines between crosstalk noise, at common-mode state, the common-mode noise of subscribers feeder can arrive exchanger side by the local side separator smoothly, therefore the present invention can directly measure the broadband common-mode noise of subscriber's line, utilize the relation of it and circuit longitudinal balance parameter to be converted to crosstalk noise between line, avoid broadband noise between direct p-wire, thereby can be implemented in switch grabs under the condition of line, carry out automatic adsl line test, also being supported in simultaneously DSLAM realizes grabbing under the condition of line function, carry out automatic broadband test function, solved and to have utilized switch to grab line functional test adsl line parameter in the prior art and cause telecom operators existing adsl equipment to be faced the problem of maintenance test difficulty.
Description of drawings
Fig. 1 is the transmission network figure of ADSL;
Fig. 2 is a theory diagram of implementing line tester of the present invention;
Fig. 3 is the theory diagram of the line test plate of line tester inside;
Fig. 4 is tested circuit model figure;
Fig. 5 is a concrete operations flow chart of the present invention;
Fig. 6 is the steady-state response test flow chart under the low-frequency ac excitation;
Fig. 7 implements the test circuit schematic diagram that the ac-excited steady-state response down of high and low frequency is tested among the present invention;
Fig. 8 is the steady-state response test flow chart under the high-frequency ac excitation;
Fig. 9 is the common-mode noise test flow chart;
Figure 10 is a test circuit schematic diagram of implementing common-mode noise test among the present invention;
Figure 11 is the basic block diagram of local side DSLAM built-in splitter.
Embodiment
The present invention discloses a kind of adsl line method of testing, this method is applied to comprise the tester of line test plate, as shown in Figure 2, this tester comprises master control borad 110, ATU-R plate 120, ATU-C plate 130, status display panel 140 and line test plate 150, described master control borad 110 is by display interface 111 connection status display panels 140, described ATU-R plate 120 is by hybrid interface 131 interconnection of hybrid interface 121 with ATU-C plate 130, and connect the hybrid interface 113 of master control borad 110 by interconnecting channel, described line test plate 150 connects the HPI interface 112 of master control borad 110 by HPI interface 151, master control borad 110 is tested by 150 pairs of circuits of HPI interface control line drive test test plate (panel), data via line test board 150 after the test is gathered and is handled, result is by the HPI interface 151 of line test plate 150, the HPI interface 112 of master control borad 110, be sent to master control borad 110, and be sent to testing server 160 by RS232 interface 114.
As shown in Figure 3, described line test plate LTB plate is core with DSP, in conjunction with CPLD, 12 broadband A sample circuits of FPGA real time high-speed two-way, accurate DDS, low noise broadband P GA, high common mode input AMP, accurate constant-current source able to programme, relay physical circuit switch unit, finish test and excitation, data acquisition, digital filtering, frequency domain transform and signal analysis function jointly, realize test parameter between tested line-to-ground parameter and line.
The line test plate is divided into three unit from function, i.e. acquisition process unit 330, control unit 320, test cell 310; Described acquisition process unit 330 comprises digital signal processor DSP, amplifier, field programmable gate array (FPGA, Field Programmable Gate Array), memory RAM etc., described control unit 320 comprises switching device shifter (as relay etc.), CPLD (CPLD, Complex Programmable Logic Device) etc., described test cell 310 comprises adjustable constant-flow subelement, phone interface subelement, signal excitation subelement; Described adjustable constant-flow subelement comprises discharge resistance, digital to analog converter, metal-oxide-semiconductor, low pressure amplifier and source of stable pressure; Described phone interface subelement comprises discharge resistance and constant-current source, and wherein constant-current source can be triode and Voltage stabilizing module composition; Described signal excitation subelement comprises discharge resistance, Direct Digital synthesizer etc.
Master control borad loads test command by the HPI interface to the line test plate, the acquisition process unit 330 control CPLD of line test plate drive relay short circuit measurement circuit, deliver to the A/D converter ADS803 of acquisition process unit 330 after the broadband test passage that common-mode noise is formed via low noise amplifier and variable gain amplifier amplifies, the DSP of acquisition process unit 330 arrives RAM to the noise signal data acquisition of circuit by FPGA control ADS803; After collection is finished, DSP controls all test resources and discharges, DSP carries out the frequency domain transform analysis to the The data FFT Fourier transform of gathering, calculate circuit common-mode noise power spectral density and root-mean-square value, then result is sent to master control borad through the HPI interface, delivers to testing server by the RS232 interface at last.
Master control borad loads test command by the HPI interface to the line test plate, and the relay in the DSP control CPLD driving control unit 320 in the acquisition process unit 330 of line test plate inserts test bus with discharge resistance, and restore the discharge back; DSP in collection and the processing unit 330 sends data by the CPLD of control unit to digital to analog converter, it is electric current that low pressure amplifier and metal-oxide-semiconductor and source resistance thereof make this voltage transitions, send constant current by main test bus to tested object, after the tested object response, produce the zero state response curve data, DSP in the acquisition process unit 330 gathers the zero state response curve data of the circuit of tested object by FPGA control ADS803, and send into RAM and handle, after collection is finished, DSP discharges all test resource controls, in the process of handling, the The data self-adaptive smooth filtering of DSP to gathering, the way of piecewise analysis and least-square analysis, eliminate and disturb, calculate the every resistance and the electric capacity of circuit, result is sent to master control borad through the HPI interface, delivers to testing server by state RS232 interface then.
Master control borad loads test command by the HPI interface to the line test plate, relay in the DSP control CPLD driving control unit 320 in the acquisition process unit 330 of line test plate will insert test bus by the constant-current source that triode, Voltage stabilizing module are formed, make measurement circuit be charged to predetermined voltage, relay in the DSP driving control unit 320 in the acquisition process unit 330 inserts discharge resistance then, cut off constant-current source, tested object circuit enters discharge condition; DSP in the acquisition process unit 330 gathers the discharge response curve data of measurement circuit by FPGA control ADS803 simultaneously, sends into RAM and handles; After collection is finished, DSP controls all test resources and discharges, the ways such as The data self-adaptive smooth filtering, piecewise analysis and method of least squares analysis of DSP in the acquisition process unit 330 to gathering, eliminate and disturb, calculate the every resistance and the electric capacity of circuit, result is sent to master control borad through the HPI interface, delivers to testing server by the RS232 interface then.
Master control borad loads test command by the HPI interface to the line test plate, and the relay in the DSP control CPLD driving control unit 320 in the acquisition process unit 330 of line test plate inserts test bus with discharge resistance, and the discharge back cuts off; DSP in the acquisition process unit 330 produces the sine wave of single-frequency by CPLD control Direct Digital synthesizer, carry out power amplification through AD8016, insert test bus by relay, tested object produces response to pumping signal, the steady-state response curve data of 330 pairs of signal source curves in acquisition process unit and measurement circuit is gathered, after collection is finished, DSP in the acquisition process unit 330 discharges all test resource controls, DSP in the acquisition process unit 330 analyzes the The data self-adaptive smooth filtering and the FFT fast fourier transformation algorithm of gathering, the AC impedance parameter imaginary part and the real part of computational scheme, combined circuit distributed constant empirical algorithms, calculate Route Length, loop resistance and insertion loss, result is sent to master control borad through the HPI interface, delivers to testing server by the RS232 interface then.
The tested circuit model that the present invention is directed to as shown in Figure 4, this circuit model comprises that be resistance R 1, the R2 that is serially connected with in the outside line to the equivalence of the distributed resistance of two outside line a, b, and the distributed capacitance equivalence on two outside line a, b and ground is capacitor C ag, Cbg and is connected in two capacitor C ab between outside line.
Below in conjunction with Fig. 5 concrete operations step of the present invention is described.
At first carry out pretest, i.e. execution in step S301 and step S302, wherein step S301 is: carry out the basic ten binomial parameter test of circuit, between the line of measurement circuit and combined-voltage over the ground, insulation resistance and electric capacity; Wherein step S302 is: the basic ten binomial parameter values by circuit judge whether circuit has hard damage, as phenomenons such as: broken string, swinging cross, charged, defective insulations; If there is above-mentioned phenomenon, the fault prompting is returned in test below then stopping; Ten binomial parameter of testing in above-mentioned two steps are the most basic parameters of circuit, have only these parameters in normal range (NR), could guarantee that circuit can carry out basic telephone communication, get rid of the most basic circuit and damage firmly, just can talk about the bearing capacity of circuit on this basis ADSL; And because will be a line of test line, b line and the mutual short circuit of ground difference in the later test, so will test basic ten binomial parameter, can not there be too high voltage in circuit for confirmation, in order to avoid damage testing equipment; Through after the pretest, then execution in step S303 promptly carries out low-frequency ac excitation steady-state response test down, records between the line of circuit and the direct-to-ground capacitance value, utilizes the direct-to-ground capacitance value to calculate line length; Execution in step S304 then promptly carries out high-frequency ac excitation steady-state response test down, records between the line of circuit and the earth impedance value of real part, utilizes the earth impedance value of real part to calculate the circuit loop resistance; Then execution in step S305 promptly utilizes line length and loop resistance calculation of parameter to go out the insertion loss of test line in the ADSL frequency band; Here the empirical equation of utilizing a circuit distribution impedance principle and experience to obtain.State is irrelevant between this result and line; Execution in step S306 subsequently, promptly carry out Longitudinal Balance Test, add sinusoidal simple signal source by standard resistor between over the ground simultaneously at test line a, b line, measure signal level between the line under this frequency, calculate the ratio of this level and signal source level by normalized form, obtain the longitudinal balance parameter of test line; This parameter has been represented the ability of circuit opposing environment crosstalk noise, has also reflected the protective capacities of crosstalking that when opening the ADSL business on this circuit All other routes is caused; Then execution in step S307 promptly carries out the common-mode noise test, obtains the circuit common-mode noise power spectral density in the ADSL frequency band; And then execution in step S308 promptly calculates broadband noise power spectral density between the line of circuit by common-mode noise and longitudinal balance value; Step S308 is the common-mode noise power spectral density of the test line that obtains with step S307, deducts the test line longitudinal balance value that step S306 obtains, and obtains broadband noise between the equivalent line of test line; Last execution in step S309 promptly calculates the highest ADSL up-downgoing speed of carrying of circuit according to broadband power spectrum density between circuit insertion loss and line; Step S309 utilizes broadband noise and step S305 obtain between the equivalent line of the test line that step S308 obtains test line to insert loss to calculate signal to noise ratio in the ADSL frequency band, thereby estimates the ability of test line carrying ADSL.Latter two steps is the last performance evaluation after the test, by last performance evaluation, can determine the final bearing capacity of circuit, being implemented in switch grabs under the condition of line, carry out the test of automatic adsl line, also be supported in simultaneously under the condition that DSLAM grabs line, carry out automatic broadband test function.
When carrying out the steady-state response test test of high and low frequency under ac-excited, the circuit theory of test adopts high-speed low-noise double A/D sample circuit simultaneously signal source and test access point to be sampled as shown in Figure 7.The digital to analog converter of 12 high s/n ratios that the present invention has adopted two models in the A/D sample circuit be ADS803 and TL062 broadband dual operational amplifier are formed the double A/D sample circuit; Signal source has adopted broadband A 9832 able to programme and Direct Digital synthesizer DDS chip, and it not only is used for the method applied in the present invention, also is used for broadband longitudinal balance and broadband frequency sound test; Relay has all been used in all functional circuits that are connected with test line switchings, certainly uses other switching device shifter to switch.
To step S303, promptly how to carry out low-frequency ac excitation steady-state response test down below in conjunction with Fig. 6, record between the line of circuit and the direct-to-ground capacitance value, utilize the direct-to-ground capacitance value to calculate line length and be described in detail.
Execution in step S401 at first, concrete operations are: insert discharge resistance between test line a line and ground, a line and b line, b line and the ground, circuit is discharged, restore after 1 second; Circuit is discharged in advance and can drop to the influence that the rapid test of previous step causes circuit minimum; Execution in step S402 subsequently, promptly by relay b line ground connection, insert the test circuit of Fig. 7 at a line, send the low-frequency ac-excited signal of low level to a line, two-way A/D carries out signal sampling to signal source and a line access point simultaneously, adopt self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculate the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain capacitance C1, this moment, capacitance C1 was Cab and result after Cag is in parallel, circuit restoration then; Follow execution in step S403, promptly by relay a line ground connection, insert the test circuit of Fig. 7 at the b line, send the low-frequency ac-excited signal of low level to the b line, two-way A/D carries out signal sampling to signal source and b line access point simultaneously, adopt self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculate the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain capacitance C2, this moment capacitance C1 be Cab with Cbg in parallel after the result, circuit restoration then; Follow execution in step S404 again, promptly by relay short circuit ab line, and the test circuit of access Fig. 7, send the low-frequency ac-excited signal of low level, two-way A/D carries out signal sampling to signal source and access point simultaneously, adopts self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculate the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain capacitance C3, this moment capacitance C1 be Cag with Cbg in parallel after the result, circuit restoration then; And then execution in step S405 promptly obtains actual capacitance value Cab, Cag and the Cbg of circuit by following formula:
Cab＝(C1+C2-C3)/2
Cag＝(C1+C3-C2)/2
Cbg＝(C2+C3-C1)/2
By following empirical equation computational scheme length L: L=(Cag+Cbg) * k, described k are coefficient.
The major parameter of this step test is the capacitance of circuit, and the selection of test and excitation signal frequency has requirement: the frequency choosing is high, and the influence of the inductance of DSLAM separator, the inductance of circuit and loss can strengthen, and test error can increase; Frequency is selected low, and the stability of unit testing time build-in test can descend; The frequency multiplication influence of 50 hertz of power-frequency voltages to be avoided more exactly, otherwise accuracy of test can be influenced.And the level of test and excitation signal can not be too high, otherwise can puncture the diode circuit of phone set terminal inside, and the parameter of test will be subjected to the influence of terminal phone.The low-frequency excitation signal that the present invention adopts is below 500 hertz, and level is at sine below 2 volts or cosine wave, and the evidence frequency is 240 hertz, and the signal level peak value is 1.5V, can access preferable test result.Test result is final, and what adopt is that the direct-to-ground capacitance value of test line is come computational scheme length, and the state between line is irrelevant.
To step S304, promptly how to carry out high-frequency ac excitation steady-state response test down below in conjunction with Fig. 8, record between the line of circuit and the earth impedance value of real part, utilize the earth impedance value of real part to calculate the circuit loop resistance and be described in detail.
Execution in step S501 at first, concrete operations are: insert discharge resistance between test line a line and ground, a line and b line, b line and the ground, circuit is discharged, restore subsequently; It is necessary that circuit is discharged in advance, can drop to the influence that the rapid test of previous step causes circuit minimum; Execution in step S502 subsequently, promptly by relay b line ground connection, insert the test circuit of Fig. 7 at a line, send the high-frequency ac-excited signal of low level to a line, two-way A/D carries out signal sampling to signal source and a line access point simultaneously, adopts self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculates the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain value of real part R1, then circuit restoration; Follow execution in step S503, promptly by relay a line ground connection, insert the test circuit of Fig. 7 at the b line, send the high-frequency ac-excited signal of low level to the b line, two-way A/D carries out signal sampling to signal source and b line access point simultaneously, adopts self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculates the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain value of real part R2, then circuit restoration; Follow execution in step S504, promptly by relay short circuit ab line, and the test circuit of access Fig. 7, send the high-frequency ac-excited signal of low level, two-way A/D carries out signal sampling to signal source and access point simultaneously, adopts self-adaptive smooth filtering and FFT fast fourier transformation algorithm to carry out frequency domain transform, calculates the AC impedance parameter imaginary part and the real part of the circuit under this state, obtain value of real part R3, then circuit restoration; Then execution in step S505 compares R1 and R2, if R1 ≈ is R2, promptly obtains the loop resistance R1p:R1p=N * Rg (1+1g (L/M)) of circuit by following empirical equation, and wherein said N and M are empirical coefficient; If it is too big that R1 and R2 differ, show that a certain line of circuit occurs unusual; Computational scheme inserts loss (line frequency response):
Described F is each sub-carrier frequencies of ADSL, and m, n, k, q are empirical coefficient.
This step mainly is between the line of test test line and the real part of earth impedance, thereby the loop resistance of computational scheme, the selection of test and excitation signal frequency also has requirement: the frequency choosing is high, the influence of the inductance of DSLAM separator, the inductance of circuit and loss can strengthen, and the sensitivity meeting of test descends; Frequency is selected low, and result's stability of test can descend.The high-frequency excitation signal that this step of the present invention adopts is between 500 hertz to 3000 hertz, level the experiment proved that at sine below 2 volts or cosine wave high-frequency excitation signal is 2000 hertz, when the signal level peak value is 1.5 volts, can access the preferable linearity.Test result is final, and what adopt is that the earth impedance value of real part of test line is come the computational scheme loop resistance, and the state between line is irrelevant.
, promptly how to carry out the common-mode noise test and be described in detail step S307 below in conjunction with Fig. 9.
At first, execution in step S601 is about to insert discharge resistance between test line a line and the b line, and test line is discharged, and restores after 500 milliseconds; Then execution in step S602, i.e. the outside line a and the b of control relay short circuit test line, and insert as shown in figure 10 test circuit, test test line 26 KHz to 1104 KHz common-mode noise over the ground; This moment is owing to the outside line a and the outside line b short circuit of test line, so the noise of line-to-ground is exactly a common-mode noise; Described measurement circuit comprises the sampling unit high-speed a/d, processing unit DSP, high input impedance wide-band amplifier, programmable gain amplifier, switching device shifter are such as relay, a line ground connection at the input of high input impedance wide-band amplifier, another line is succeeded electrical equipment, output serial connection programmable gain broadband amplifier; Described relay is used for the outside line a of circuit switched and b and carries out short circuit or outside line ground connection wherein; Described programmable gain broadband amplifier receives the gain controlling order of processing unit DSP, adjusts the amplifier gain value; Described sampling unit A/D samples to common mode noise signal, and delivers to DSP; Next execution in step S603, promptly test common mode noise signal, and by sampling unit A/D sampling, delivering to processing unit DSP analyzes, extract the common-mode noise maximum, send order to the programmable gain broadband amplifier by processing unit DSP then, promptly adjust the amplifier gain value, make the noise level of delivering to test circuit in suitable scope according to this maximum; Last execution in step S604, promptly test circuit is sampled to common mode noise signal, and the processing unit DSP that delivers to the line test plate of tester carries out the FFT fast fourier transform, obtains the common-mode noise power spectral density.
In this step because outside line a, outside line b short circuit, make wiring PSTN-A, the PSTN-B of local side DSLAM built-in splitter also be in short circuit state (referring to Figure 11), thereby make the inductance 800 of DSLAM built-in splitter form conjugation, inductance is cancelled basically, and the common-mode noise of test line can directly arrive test circuit by the DSLAM built-in splitter basically.The present invention adopts relay short circuit outside line a, outside line b, amplifier has adopted the amplifier of high cmrr, low noise, high difference input impedance and broadband programmable gain amplifier to carry out the adaptive gain adjustment to amplify, and this amplifying circuit also is used for noise testing between broadband line.Common mode noise signal is delivered to digital signal processing unit DSP after amplification and A/D sampling, carry out fast Flourier FFT and be transformed to the interior power spectral density of ADSL frequency band, obtains the common-mode noise power spectral density of test line.
The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in technical scope disclosed by the invention; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claims.
Claims (13)
1, a kind of method of testing of adsl line parameter, be used for the equivalent string connecting resistance (R1, R2) that test comprises the distributed resistance of two outside lines (a, b), article two, the equivalent capacity (Cag, Cbg) of the distributed capacitance on outside line (a, b) and ground and the adsl line parameter that is connected two equivalent capacitys (Cab) between outside line, it is characterized in that, comprising:
Respectively with wherein outside line ground connection of tested circuit, an other unearthed outside line serial connection test circuit, send pumping signal to tested circuit, described pumping signal and line access point are carried out signal sampling, measure the hybrid parameter over the ground and between line of tested circuit according to sampled result;
With two outside line short circuits of tested circuit, insert test circuit, send pumping signal to tested circuit, described pumping signal and line access point are carried out signal sampling, measure the hybrid parameter over the ground of tested circuit according to sampled result;
Utilize the data computation of above-mentioned parameter to go out corresponding line parameter circuit value.
2, according to the method for testing of the described adsl line parameter of claim 1, it is characterized in that, also comprise:
21), with two outside line short circuits, insert test circuit, test test line common mode noise signal over the ground;
22), common mode noise signal is sampled, calculate the common-mode noise power spectral density according to sampled result.
3, according to the method for testing of claim 1 or 2 described adsl line parameters, it is characterized in that, described test circuit comprises signal generating unit and double A/D sampling unit, described signal generating unit produces pumping signal and gives the tested circuit that inserts, and described double A/D sampling unit carries out signal sampling to described pumping signal and line access point respectively simultaneously.
According to the method for testing of the described adsl line parameter of claim 3, it is characterized in that 4, described test circuit also comprises the noiselike signal amplifying unit, described signal amplification unit is used for the signal of sampling is amplified.
5, according to the method for testing of the described adsl line parameter of claim 4, it is characterized in that, described pumping signal be frequency between 500 hertz to 3000 hertz, level is at sine below 2 volts or cosine wave.
6, according to the method for testing of the described adsl line parameter of claim 4, it is characterized in that, described pumping signal be frequency below 500 hertz, level is at sine below 2 volts or cosine wave.
7, according to the method for testing of the described adsl line parameter of claim 5, it is characterized in that, the hybrid parameter over the ground of described tested circuit is: the earth impedance value of real part (R1) of tested circuit during outside line a ground connection, the earth impedance value of real part (R2) of tested circuit during outside line (b) ground connection; Hybrid parameter is between the line of described tested circuit: the earth impedance value of real part (R3) during tested line short circuit.
8, according to the method for testing of the described adsl line parameter of claim 6, it is characterized in that, the hybrid parameter over the ground of described tested circuit is: the direct-to-ground capacitance (C1) of tested circuit during outside line (a) ground connection, the direct-to-ground capacitance (C2) of tested circuit during outside line b ground connection; Hybrid parameter is between the line of described tested circuit: the direct-to-ground capacitance (C3) during tested line short circuit.
According to the method for testing of claim 7 or 8 described adsl line parameters, it is characterized in that 9, the described data computation of utilizing above-mentioned parameter goes out corresponding line parameter circuit value and specifically comprises:
Calculate the actual capacitance value of tested circuit: Cab=(C1+C2-C3)/2, Cag=(C1+C3-C2)/2, Cbg=(C2+C3-C1)/2;
Calculate tested Route Length: L=min (Cag, Cbg) * K, described K is an empirical coefficient;
When R1 ≈ R2, calculate the loop resistance of tested circuit: Rlp=N * R3 * (1+Lg (L/M)); Described N, M are empirical coefficient;
Computational scheme inserts loss:
Described F is each sub-carrier frequencies of ADSL, and m, n, k, q are empirical coefficient.
10, according to the method for testing of the described adsl line parameter of claim 2, it is characterized in that described test circuit comprises A/D sampling unit, processing unit DSP, programmable gain broadband amplifying unit, high input impedance broadband amplifying unit and circuit switch unit; Common mode noise signal by sampling unit A/D sampling, is delivered to processing unit DSP and is analyzed, and extracts the common-mode noise maximum, adjusts the amplifier gain value according to this maximum, makes the noise level of delivering to test circuit in suitable scope.
11, according to the method for testing of the described adsl line parameter of claim 10, it is characterized in that the process of described test test line common-mode noise over the ground is specially: the test line of test frequency in 26 KHz to 1104 kilohertz range noise power spectral density data and longitudinal balance value over the ground.
According to the method for testing of the described adsl line parameter of claim 11, it is characterized in that 12, described process according to sampled result calculating common-mode noise power spectral density specifically comprises: the noise power spectral density data and the longitudinal balance value of test line are subtracted each other; Get difference.
13, according to the method for testing of claim 9 or 12 described adsl line parameters, it is characterized in that, before test, also comprise: circuit is discharged.
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| CN 200410080905 CN1588966A (en) | 2004-09-27 | 2004-09-27 | Method for detecting ADSC line parameter |
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