CN101635694A - Adaptive equalizer and method for adaptive equalization - Google Patents
Adaptive equalizer and method for adaptive equalization Download PDFInfo
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- CN101635694A CN101635694A CN200810116931A CN200810116931A CN101635694A CN 101635694 A CN101635694 A CN 101635694A CN 200810116931 A CN200810116931 A CN 200810116931A CN 200810116931 A CN200810116931 A CN 200810116931A CN 101635694 A CN101635694 A CN 101635694A
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Abstract
The invention provides an adaptive equalizer and a method for adaptive equalization. The adaptive equalizer comprises an amplitude detection circuit, an auto gain control circuit, a digital control circuit and a gain improvement circuit, wherein the amplitude detection circuit is used for detecting the amplitude attenuation state of an input signal and obtaining a detection result, wherein the input signal is the initial input signal or gained signal; the auto gain control circuit is used for providing the gain processing for the initial input signal according to the detection result to obtain a gained signal; the digital control circuit is used for computing the transmission distance of the initial input signal according to the gain finally provided by the auto gain control circuit when the detection result shows that the input signal meets the requirements; and the gain improvement circuit is used for providing the corresponding gain for a main frequency component and a direct current component of the initial input signal according to the transmission distance to obtain and output the equalization signal. The adaptive equalizer can adaptively adjust the compensation of the signal amplitude according to the transmission distance of the signal.
Description
Technical field
The present invention relates to the signal processing field, relate in particular to a kind of adaptive equalizer and adaptive equilibrium method.
Background technology
In SDH (Syschronous Digital Hierachy, SDH (Synchronous Digital Hierarchy)) transmission system, signal can produce decay after the transmission of long distance, cause system receiving terminal to receive the signal of distortion.
The SDH transmission system comprises multiple digital transmission standard, as T1 and E1 etc., wherein, T1 is a kind of digital transmission standard commonly used, be illustrated in figure 1 as the waveform attenuating schematic diagram after the different transmission ranges of T1 signal pulse process in the prior art, by transmission range is long more as can be seen among Fig. 1, the decay of T1 signal amplitude is big more, and pulse duration is also wide more.
At this moment, system receiving terminal need use equalizer to carry out amplitude and frequency compensation to the received signal, thereby obtains the less signal of distortion, carries out follow-up signal processing then.Be illustrated in figure 2 as SDH transmission system schematic diagram in the prior art, as shown in Figure 2, at system's transmitting terminal, information source is through coding and pulse-shaping and circuit driving back generation primary signal, arrive system receiving terminal behind the primary signal transmission certain distance, system receiving terminal at first utilizes the equalizer that is positioned at front end that the input signal that receives is carried out equilibrium treatment, obtains the less signal of distortion, and then carries out yard type recovery and operations such as data clock recovery and decoding.
Yet equalizer equalizes scope of the prior art is all more limited, and can not adjust balanced scope neatly according to the length of transmission line, and when transmission range was long or too short, equilibrium and balanced excessively situation may appear owing in signal.
Summary of the invention
The embodiment of the invention has proposed a kind of adaptive equalizer and adaptive equilibrium method, can adjust compensation to signal amplitude according to the length self adaptation of transmission line.
In order to achieve the above object, the embodiment of the invention provides a kind of adaptive equalizer, comprising:
Amplitude detection circuit is used to detect the amplitude fading state of input signal, obtains a testing result, and described input signal is initial input signal or gain back signal;
Automatic gain control circuit is used for according to described testing result, for described initial input signal provides gain process, obtains described gain back signal;
Digital control circuit is used for when described testing result shows that described input signal meets the demands, and according to the gain that described automatic gain control circuit finally provides, calculates the transmission range of described initial input signal;
Gain improvement circuit is used for according to described transmission range, for the dominant frequency component and the DC component of described initial transmission signal provides corresponding gain, obtains equalizing signal and output.
Described adaptive equalizer also comprises:
First switch is used to receive described initial input signal, comprises first passage, second channel, third channel and four-way;
Second switch comprises five-way road and the 6th passage, and described five-way road is connected with described second channel;
Described amplitude detection circuit is connected with described first passage;
Described automatic gain control circuit is connected with described amplitude detection circuit with described third channel;
Described gain improvement circuit is connected with described the 6th passage with described four-way;
Described digital control circuit, be used for when described testing result shows that described initial input signal meets the demands, control the described second channel of described first switch conduction, control the described five-way of described second switch conducting road, when signal does not meet the demands after described testing result shows described initial input signal or described gain, control the described third channel of described first switch conduction, and outputing gain control signal, and when described testing result shows that described gain back signal meets the demands, according to the gain that finally provides for described initial input signal, calculate the transmission range of described initial input signal, and control the described four-way of described first switch conduction, control described the 6th passage of described second switch conducting.
Described gain improvement circuit is connected with described the 6th passage by the post-filtering circuit;
Described post-filtering circuit is used for described equalizing signal is carried out exporting after noise is eliminated in filtering.
Described adaptive equalizer also comprises:
Signal deteching circuit is connected with described first switch with described digital control circuit, whether is used to detect the amplitude of described initial input signal greater than second predetermined threshold value;
Described digital control circuit is further used for during greater than described second predetermined threshold value, controlling the described first passage of described first switch conduction in the amplitude of described initial input signal.
Described automatic gain control circuit also is connected with described amplitude detection circuit by the fixed gain circuit;
Described fixed gain circuit, be used for reaching maximum in the gain that described automatic gain control circuit provides for described initial input signal, and when described gain back signal does not still meet the demands, provide the gain of fixed amplitude to the output signal of described automatic gain control circuit, and with the gained signal as new gain after signal output to described amplitude detection circuit.
In order to achieve the above object, the embodiment of the invention also provides a kind of adaptive equilibrium method, may further comprise the steps:
Detect the amplitude fading state of gain back signal, obtain a testing result;
According to described testing result, for the initial input signal provides gain process, obtain described gain back signal, show that until described testing result described gain back signal meets the demands;
When described gain back signal meets the demands,, calculate the transmission range of described initial input signal according to the gain that finally provides for described initial input signal;
According to described transmission range,, obtain equalizing signal and output for the dominant frequency component and the DC component of described initial transmission signal provides corresponding gain.
Described adaptive approach also comprises:
Detect the amplitude fading state of described initial input signal, when described initial input signal meets the demands, directly control the step of described initial input signal output.
Described adaptive approach also comprises:
Described equalizing signal carried out the step exported behind the filtering and eliminating noise.
Also comprise before the amplitude fading state of described detection gain back signal:
Whether the amplitude that detects described initial input signal is greater than the step of second predetermined threshold value;
During greater than described second predetermined threshold value, detect the step of the amplitude fading state of described initial input signal in the amplitude of described initial input signal.
Reach maximum in the gain that provides for described initial input signal, and described gain back signal is not when meeting the demands still, for described gain afterwards signal the gain of fixed amplitude is provided, and with the gained signal as new gain after signal.
The embodiment of the invention has following beneficial effect:
By obtaining the transmission range of initial input signal, provide the amplitude compensation according to transmission range for the initial input signal, can adjust the gain range of equalizer neatly adaptively according to the length of transmission range, correctly restoring signal reaches portfolio effect preferably.
Description of drawings
Fig. 1 is the waveform attenuating schematic diagram after the different transmission ranges of T1 signal pulse process in the prior art;
Fig. 2 is a SDH transmission system schematic diagram in the prior art;
Fig. 3 is the equalizer structure schematic diagram of the embodiment of the invention;
Fig. 4 is the automatic gain control circuit structural representation of the embodiment of the invention;
Fig. 5 is another equalizer structure schematic diagram of the embodiment of the invention;
Fig. 6 is the adaptive equilibrium method schematic flow sheet of the embodiment of the invention;
Fig. 7 is that the adaptive equalization implement body of the embodiment of the invention is implemented the scene schematic diagram;
Fig. 8 is the gain range schematic diagram that provide of gain improvement circuit under different control signals of the embodiment of the invention;
Fig. 9 is the gain characteristic of the adaptive equalizer of the embodiment of the invention, the attenuation characteristic of T1 transmission line and the superimposed characteristics schematic diagram of the two.
Embodiment
The embodiment of the invention provides a kind of adaptive equalizer and adaptive equilibrium method, by the amplitude detection of carrying out to the initial input signal, for the initial input signal provides gain, and to gain the back signal carry out amplitude detection, progressively adjust the gain range of equalizer, until the input signal that is met requirement, and according to the distance of the gain calculating transmission line that finally provides, distance according to transmission line provides the amplitude compensation for the initial input signal, the embodiment of the invention can be adjusted the gain range of equalizer neatly adaptively according to the length of transmission range, correctly restoring signal reaches portfolio effect preferably.
Be illustrated in figure 3 as the equalizer structure schematic diagram of the embodiment of the invention, this equalizer comprises:
First switch is used to receive the initial input signal, and described first switch comprises first passage, second channel, third channel and four-way, the signal that the primary signal that this initial input signal sends for system's transmitting terminal decays after the specific range transmission.
Second switch comprises five-way road and the 6th passage, and described five-way road is connected with described second channel.
Amplitude detection circuit, be connected with described first passage, be used to detect the amplitude fading state of initial input signal or gain back signal, obtain a testing result, described testing result comprises two kinds of situations: the one, and the input signal of amplitude detection circuit does not meet the demands, promptly there is certain decay in this input signal, the 2nd, the input signal of amplitude detection circuit meets the demands, promptly there is not decay in this input signal, certainly not have decay be not to be that the input signal of amplitude detection circuit is definitely consistent with the amplitude of primary signal to signal described herein, but approaching a value.
Digital control circuit, be used for when described testing result shows that described initial input signal meets the demands, control the first switch conduction second channel, control second switch conducting five-way road, when described testing result shows that described initial input signal or gain back signal do not meet the demands, control the first switch conduction third channel, and outputing gain control signal, and when described testing result shows that described gain back signal meets the demands, according to the gain that finally provides for the initial input signal, calculate the transmission range of initial input signal, and control the first switch conduction four-way, control second switch conducting the 6th passage.
Automatic gain control circuit, be connected with amplitude detection circuit with described third channel, be used under the control of gain control signal, input signal being carried out gain process, obtain described gain back signal, and described gain back signal is outputed to described amplitude detection circuit; Automatic gain control circuit can be the initial input signal provides default gain range scope interior gain, should preset of the digital transmission standard decision of gain range scope by the SDH transmission system, when the digital transmission standard of system was T1, this default gain range scope can be set to :-14dB to 7dB.
Gain improvement circuit, be connected with the 6th passage with four-way respectively, being used for according to described transmission range is that the dominant frequency component and the DC component (other low frequency components) of initial input signal provides corresponding gain, promptly the initial input signal is carried out shaping and recovers, and obtains equalizing signal.Gain improvement circuit is specially the method that input signal carries out the shaping recovery: the dominant frequency component to input signal gains, and DC component is decayed, and obtains the equalizing signal similar to original signal waveform.
Because system also must carry out follow-up signal processing to the output signal of equalizer, generally, wish that the output signal obtain is not the signal identical with original signal amplitude, but than the signal of primary signal decay specific amplitude.
Suppose that the output signal that need obtain is: amplitude is than the decay signal of first predetermined threshold of primary signal, above-mentioned amplitude detection circuit is specially the method that the amplitude fading state of its input signal (initial input signal or gain back signal) detects: the attenuation amplitude and the default threshold level of input signal are compared, obtain the amplitude fading scope of input signal, should preset threshold level can be for one or more, three threshold levels are set in the present embodiment, first threshold level, second threshold level and the 3rd threshold level, three threshold levels increase successively, and the 3rd threshold level equals first predetermined threshold.
When the attenuation amplitude of input signal during less than first threshold level, the expression attenuated input signal is too small, and digital control circuit control automatic gain control circuit provides negative gain (i.e. decay) for input signal; When the attenuation amplitude of input signal between first threshold level and second threshold level, or between second threshold level and the 3rd threshold level the time, show that there is certain decay in input signal, but decay does not still meet the demands, and digital control circuit control automatic gain control circuit provides negative gain (i.e. decay) for input signal; When the attenuation amplitude of input signal during greater than the 3rd threshold level, show that attenuated input signal is excessive, digital control circuit control automatic gain control circuit provides postiive gain for input signal; When the attenuation amplitude of initial input signal equals or during near the 3rd threshold level, digital control circuit control initial input signal is directly exported, and does not carry out gain process; When the attenuation amplitude of gain back signal equals or during near the 3rd threshold level, the digital control circuit ride gain promotes circuit the initial input signal is carried out gain compensation.
Above-mentioned automatic gain control circuit can adopt operational amplifier and resistor network to realize, be illustrated in figure 4 as the automatic gain control circuit structural representation of the embodiment of the invention, it comprises four resistor networks and an operational amplifier, its change in gain realizes by the resistor network of gain control signal control, and gain signal is amplified output by operational amplifier, wherein vinp and vinn represent the input signal of automatic gain control circuit, and voutn and voutp are the output signal after gaining.
In addition, may there be certain noise in the signal of being exported by automatic gain control circuit, and therefore, as shown in Figure 5, the sef-adapting filter of the embodiment of the invention also comprises:
The pre-filtering circuit, be used for the signal of automatic gain control circuit output is carried out filtering and eliminating noise, and with filtered signal as new gain after signal output to amplitude detection circuit, prefilter can adopt second-order low-pass filter to realize, is made up of resistance and high gain operational amplifier.
At this moment, automatic gain control circuit is connected with amplitude detection circuit by the pre-filtering circuit.
Above-mentioned gain improvement circuit can adopt switching capacity filter to realize, the switch in the gain improvement circuit may be introduced noise at this moment, and therefore, as shown in Figure 5, filter also comprises:
The post-filtering circuit is used for the equalizing signal of gain improvement circuit output is carried out filtering and eliminating noise, and the post-filtering circuit can adopt low-pass first order filter to realize.
At this moment, gain improvement circuit is connected with the 6th passage by the post-filtering circuit.
Above-mentioned equalizer carries out before the amplitude detection to input signal, can also at first carry out input to input signal, input signal greater than default amplitude is carried out amplitude detection, the input signal too small to amplitude do not carry out amplitude detection, therefore, as shown in Figure 5, the adaptive equalizer of the embodiment of the invention also comprises:
Signal deteching circuit, whether be used to detect the amplitude of initial input signal greater than second predetermined threshold value, and with testing result number of notifications word control circuit, this second predetermined threshold value is the minimum threshold of the amplitude of the treatable signal of equalizer, can independently set according to different demands.
When digital control circuit then was further used for amplitude at the initial input signal greater than second predetermined threshold value, the conducting of control first passage made the initial input signal enter amplitude detection circuit; During less than second predetermined threshold value, the control signal testing circuit is in the input state always in the amplitude of initial input signal, until the amplitude of the current input signal of signal deteching circuit greater than second predetermined threshold value.
Realize for convenience, the default gain range scope of above-mentioned automatic gain control circuit should not be provided with excessive, still, is provided with and too smallly then the initial input signal of decaying excessive is not provided enough gains, therefore, the sef-adapting filter of the embodiment of the invention can also comprise:
The fixed gain circuit, be used for reaching maximum in the gain that automatic gain control circuit provides for the initial input signal, and when the attenuation amplitude of signal does not still meet the demands after the gain that obtains, for signal after the gain of automatic gain control circuit output provides the gain of fixed amplitude, and with the signal that obtains as new gain after signal output to amplitude detection circuit, the fixed gain circuit can adopt operational amplifier and resistor network to realize.
Digital control circuit is further used for controlling the automatic gain control circuit adjusting range, makes to meet the demands through signal after the gain behind automatic gain control circuit and the fixed gain circuit gain.
By using the adaptive equalizer of the foregoing description, can adjust the gain range of equalizer neatly adaptively according to the length of transmission range, with correct restoring signal.
The adaptive equilibrium method of the embodiment of the invention as shown in Figure 6, concrete steps are as follows:
Step 61, the amplitude fading state of detection input signal, this input signal are initial input signal or gain back signal.
Step 64 is according to the amplitude fading state of input signal, outputing gain control signal.
Above-mentioned method also comprises:
Back signal and equalizing signal carry out the step that noise is eliminated in filtering to gaining; And,
Before the initial input signal was carried out amplitude detection, whether the amplitude that detects the initial input signal greater than second predetermined threshold value, if then detect the amplitude fading state of initial input signal; Otherwise, proceed input, greater than second predetermined threshold value, this second predetermined threshold value is the minimum threshold of the amplitude of the treatable signal of equalizer, can independently set according to different demands until the amplitude of current initial input signal.
In addition, reach maximum, and gain back signal is when still existing decay in the gain that provides for the initial input signal, for the back signal that gains provides the gain of fixed amplitude, and with the signal that obtains as new gain after signal.
From above-mentioned steps as can be seen, the course of work of the equalizer of the embodiment of the invention is divided into three phases: the phase I is a phase detected signal, and whether the amplitude that detects the initial input signal is greater than the treatable minimum threshold of equalizer; Second stage is the amplitude detection stage, determines the transmission range of initial input signal; Phase III is the signal compensation stage, provides corresponding amplitude and frequency compensation according to the transmission range of initial input signal for the initial input signal, finishes the equilibrium to the initial input signal, is met the equalizing signal that subsequent treatment requires.
Parameter during the work of above-mentioned equalizer is by the digital transmission standard decision of signal, below is example with the T1 transmission standard, and the course of work of above-mentioned equalizer is elaborated.
The adaptive equalization implement body that is illustrated in figure 7 as the embodiment of the invention is implemented the scene schematic diagram, wherein the digital transmission standard of signal is T1, the longest balanced distance of equalizer is 2000m, can balanced maximum attenuation amplitude the signal that is 35dB, automatic gain control circuit 101 can provide-and 14dB is to the gain of 7dB amplitude, fixed gain circuit 105 can provide the fixed gain of 14dB, three comparative levels are set in the amplitude detection circuit 111, respectively than the low 6dB of primary signal, 10dB and 14dB, finally the output signal that need obtain is the signal than primary signal decay 14dB, and the first promptly above-mentioned predetermined threshold value is 14dB.
Below be elaborated according to the course of work of above-mentioned three phases to equalizer:
(1) phase I: phase detected signal
In the embodiment of the invention, equalizer at first utilizes 101 pairs of initial input signals of automatic gain control circuit to carry out the gain of 7dB, obtain first signal, detect by 107 pairs first signals of signal deteching circuit, if the amplitude of first signal is during greater than second predetermined threshold value, enter second stage, if the amplitude of first signal is not more than second predetermined threshold value, then in conjunction with automatic gain control circuit 101 and fixed gain circuit 105, the gain of 21dB is provided for the initial input signal, if the amplitude of the signal behind the gain 21dB still is not more than second predetermined threshold value, then equalizer is in the input state always, and the specific implementation process is:
At first equalizer is carried out the circuit initialization: digital control circuit 108 outputing gain control signal gainagc＜3:0 〉, control automatic gain control circuit 101 is adjusted to 7dB with amplitude, and the switch in the output switch control signal gaincon control circuit, make line conduction between pre-filtering circuit 102 and the signal deteching circuit 107;
101 pairs of input signals of automatic gain control circuit carry out the gain of 7dB, obtain first signal;
102 pairs first signals of pre-filtering circuit carry out filtering and eliminating noise, and send filtered signal to signal deteching circuit 107 as the first new signal;
Whether signal deteching circuit 107 detects the amplitude of first signal greater than second predetermined threshold value, obtain signal detection information alos_b, and send digital control circuit 108 to, signal detection information alos_b comprises two kinds of situations: one be the amplitude of first signal greater than second predetermined threshold value, two is that the amplitude of first signal is not more than second predetermined threshold value;
If the amplitude of first signal greater than second predetermined threshold value, then enters second stage; If the amplitude of first signal is not more than second predetermined threshold value, digital control circuit 108 output switch control signal gaincon control switchs make line conduction between fixed gain circuit 105 and the signal deteching circuit 107;
105 pairs first signals of fixed gain circuit carry out the gain of 14dB, and the signal after will gaining sends signal deteching circuit 107 to, the signal of this signal this moment after for gain 21dB;
Whether the signal behind the signal deteching circuit 107 judgement gain 21dB is greater than second predetermined threshold value, if this signal still is not more than second predetermined threshold value, then equalizer is in the input state always, greater than second predetermined threshold value, enter second stage until the current input signal of signal deteching circuit 107 then.
(2) second stage: amplitude detection stage
In this stage, detect the amplitude fading state of input signal by amplitude detection circuit 111, digital control circuit 108 is according to the amplitude fading state of input signal, control automatic gain control circuit 101 and fixed gain circuit 105 provide corresponding gain for input signal, and according to the transmission range of the gain calculating initial input signal that finally provides, the specific implementation process is:
When the input signal of signal deteching circuit 107 during greater than second predetermined threshold value, digital control circuit 108 outputing gain control signal gainagc＜3:0 〉, control automatic gain control circuit 101 is adjusted to 0dB with gain range, while output switch control signal gaincon control switch, make direct-connected line conduction between pre-filtering circuit 102 and the post-filtering circuit 110, control initial input signal enters amplitude detection circuit 111;
When the attenuation amplitude of initial input signal during less than 6dB, illustrate that signal attenuation is very little, signal transmission distance is short, need carry out certain decay to the initial input signal;
When the attenuation amplitude of initial input signal between 6dB and the 10dB or between 10dB and 14dB the time, illustrate that there is certain decay in the initial input signal, but decay is big inadequately, need carry out certain decay to the initial input signal;
When the attenuation amplitude of initial input signal during greater than 14dB, illustrate that initial input signal attenuation is excessive, need carry out certain gain to the initial input signal;
When the attenuation amplitude of initial input signal equals or near 14dB, need not the initial input signal is carried out any processing, digital control circuit 108 control initial input signals are directly exported;
At first provide gain for the output input signal by automatic gain control circuit 101, the back signal obtains gaining, whether the attenuation amplitude by amplitude detection circuit 111 detection gain back signals meets the demands then, when the gain range of automatic gain control circuit 101 has reached 7dB, when but the attenuation amplitude of signal is still greater than 14dB after the gain, then by the line conduction between digital control circuit 108 control fixed gain circuit 105 and the amplitude detection circuit 111, carry out the fixed gain of 14dB by signal after 105 pairs of gains of fixed gain circuit, and with the signal that obtains as new gain after signal output to amplitude detection circuit;
When the attenuation amplitude of gain back signal equals or during near 14dB, the gain that digital control circuit 108 finally provides for the initial input signal according to automatic gain control circuit 101 and fixed gain circuit 105, calculate the input signals distance, enter the phase III;
The step-length of automatic gain control circuit 101 each amplitude adjustment is 1.4dB in the embodiment of the invention, and the corresponding relation between the gain range of the control signal of digital control circuit 108 outputs, the transmission range of initial input signal and automatic gain control circuit 101 and fixed gain circuit 105 is as shown in table 1:
Table 1
As can be seen from Table 1, by inquiry control signal gainagc＜3:0〉and gaincon can obtain the transmission range of initial input signal, enter the phase III then.
(3) phase III: signal compensation stage
In this stage, transmission range according to the initial input signal, provide gain in conjunction with fixed gain circuit 101 for the dominant frequency component and the DC component of initial input signal by gain improvement circuit 104, obtain the equalizing signal that attenuation amplitude is 14dB, the specific implementation process is:
The main spectrum component of T1 signal concentrates on the 772KHz place, and DC component (being other low frequency component) seldom, therefore, the method that the equalizer of the embodiment of the invention carries out signal shaping is specially: provide maximum gain range at the main frequency component 772KHz place of initial input signal, simultaneously the amplitude of attenuating dc component.
The lifting control signal gaingb＜2:0 of digital control circuit 108 outputs〉as shown in table 2 with the corresponding relation of the low frequency component (being DC component) of 104 pairs of input signals of gain improvement circuit and the gain that high fdrequency component (spectrum component at 772KHz place) provides:
Table 2
| Gain improvement circuit control signal gaingb＜2:0 〉 | Gain improvement circuit low-frequency gain (dB) | Gain improvement circuit high-frequency gain (dB) |
| ??000 | ??-12 | ??-6.1 |
| ??001 | ??-8.77 | ??2.30 |
| ??010 | ??-8.73 | ??10.2 |
| ??011 | ??-6.28 | ??12.0 |
| ??100 | ??-10.3 | ??14.7 |
| ??101 | ??7.42 | ??15.5 |
| ??110 | ??-7.40 | ??17.9 |
| ??111 | ??-5.25 | ??18.3 |
The gain range schematic diagram that provide of gain improvement circuit under different control signals of the embodiment of the invention is provided.
As shown in table 3ly be the corresponding relation between the gain range that provides of the control signal that provides at signal compensation stage initial input signal transmission distance, digital control circuit 108 and automatic gain control circuit 101 and gain improvement circuit 104.
Table 3
| Initial input signal attenuation | Corresponding transmission range | The automatic gain control circuit control signal | The gain improvement circuit control signal | ??eqona_b | ???gaincon |
| ??0～1.4 | ??0-80 | ??0000 | Do not enable | ?1 | ??0 |
| ??1.4～2.8 | ??80-160 | ??0001 | Do not enable | ?1 | ??0 |
| ??2.8～4.2 | ??160-240 | ??0010 | Do not enable | ?1 | ??0 |
| ??4.2～5.6 | ??240-320 | ??0011 | Do not enable | ?1 | ??0 |
| ??5.6～7 | ??320-400 | ??0100 | Do not enable | ?1 | ??0 |
| ??7～8.4 | ??400-480 | ??0101 | Do not enable | ?1 | ??0 |
| ??8.4～9.8 | ??480-560 | ??1011 | ??000 | ?0 | ??0 |
| ??9.8～11.2 | ??560-640 | ??0111 | ??001 | ?0 | ??0 |
| ??11.2～12.6 | ??640-720 | ??1000 | ??001 | ?0 | ??0 |
| ??12.6～14 | ??720-800 | ??0100 | ??010 | ?0 | ??0 |
| ??14～15.4 | ??800-880 | ??0101 | ??010 | ?0 | ??0 |
| ??15.4～16.8 | ??880-960 | ??0101 | ??011 | ?0 | ??0 |
| ??16.8～18.2 | ??960-1040 | ??0110 | ??011 | ?0 | ??0 |
| ??18.2～19.6 | ??1040-1120 | ??0111 | ??011 | ?0 | ??0 |
| ??19.6～21 | ??1120-1200 | ??0110 | ??100 | ?0 | ??0 |
| ??21～22.4 | ??1200-1280 | ??0111 | ??100 | ?0 | ??0 |
| ??22.4～23.8 | ??1280-1360 | ??0111 | ??100 | ?0 | ??0 |
| ??23.8～25.2 | ??1360-1440 | ??0111 | ??101 | ??0 | ??0 |
| ??25.2～26.6 | ??1440-1520 | ??1000 | ??101 | ??0 | ??0 |
| ??26.6～28 | ??1520-1600 | ??1001 | ??101 | ??0 | ??0 |
| ??28～29.4 | ??1600-1680 | ??1010 | ??110 | ??0 | ??0 |
| ??29.4～30.8 | ??1680-1760 | ??1011 | ??110 | ??0 | ??0 |
| ??30.8～32.2 | ??1760-1840 | ??1100 | ??110 | ??0 | ??0 |
| ??32.2～33.6 | ??1840-1920 | ??1101 | ??111 | ??0 | ??0 |
| ??33.6～35 | ??1920-2000 | ??1110 | ??111 | ??0 | ??0 |
| ??35～ | ??2000- | ??1111 | ??111 | ??0 | ??0 |
The switch controlling signal eqona_b of above-mentioned digital control circuit 108 outputs and the corresponding relation of gaincon and signal transmission line, as shown in table 4:
Table 4
As can be seen from Table 4, at phase detected signal, signal can transmit by the direct-connected circuit between pre-filtering circuit 102 and the signal deteching circuit 107, or transmits by the circuit at fixed gain circuit 105 places; In the amplitude detection stage, signal can transmit by the direct-connected circuit between pre-filtering circuit 102 and the post-filtering circuit 110, or transmits by the circuit at fixed gain circuit 105 places; In the signal compensation stage, signal can transmit by the direct-connected circuit between pre-filtering circuit 102 and the post-filtering circuit 110, or transmits by the circuit at gain improvement circuit 104 places.
Be illustrated in figure 9 as the gain characteristic of the adaptive equalizer of the embodiment of the invention, the attenuation characteristic of T1 transmission line and the superimposed characteristics schematic diagram of the two, wherein, the curve of the top is the gain characteristic of the adaptive equalizer of the embodiment of the invention, the curve of below is the attenuation characteristic of T1 transmission line, middle curve is the characteristic of both stacks, and the gain summit of equalizer is arranged on the 772KHz.
The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also do some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (10)
1. an adaptive equalizer is characterized in that, comprising:
Amplitude detection circuit is used to detect the amplitude fading state of input signal, obtains a testing result, and described input signal is initial input signal or gain back signal;
Automatic gain control circuit is used for according to described testing result, for described initial input signal provides gain process, obtains described gain back signal;
Digital control circuit is used for when described testing result shows that described input signal meets the demands, and according to the gain that described automatic gain control circuit finally provides, calculates the transmission range of described initial input signal;
Gain improvement circuit is used for according to described transmission range, for the dominant frequency component and the DC component of described initial transmission signal provides corresponding gain, obtains equalizing signal and output.
2. adaptive equalizer according to claim 1 is characterized in that, also comprises:
First switch is used to receive described initial input signal, comprises first passage, second channel, third channel and four-way;
Second switch comprises five-way road and the 6th passage, and described five-way road is connected with described second channel;
Described amplitude detection circuit is connected with described first passage;
Described automatic gain control circuit is connected with described amplitude detection circuit with described third channel;
Described gain improvement circuit is connected with described the 6th passage with described four-way;
Described digital control circuit, be used for when described testing result shows that described initial input signal meets the demands, control the described second channel of described first switch conduction, control the described five-way of described second switch conducting road, when signal does not meet the demands after described testing result shows described initial input signal or described gain, control the described third channel of described first switch conduction, and outputing gain control signal, and when described testing result shows that described gain back signal meets the demands, according to the gain that finally provides for described initial input signal, calculate the transmission range of described initial input signal, and control the described four-way of described first switch conduction, control described the 6th passage of described second switch conducting.
3. according to the adaptive equalizer shown in the claim 2, it is characterized in that:
Described gain improvement circuit is connected with described the 6th passage by the post-filtering circuit;
Described post-filtering circuit is used for described equalizing signal is carried out exporting behind the filtering and eliminating noise.
4. according to the adaptive equalizer shown in the claim 2, it is characterized in that, also comprise:
Signal deteching circuit is connected with described first switch with described digital control circuit, whether is used to detect the amplitude of described initial input signal greater than second predetermined threshold value;
Described digital control circuit is further used for during greater than described second predetermined threshold value, controlling the described first passage of described first switch conduction in the amplitude of described initial input signal.
5. according to the adaptive equalizer shown in the claim 2, it is characterized in that:
Described automatic gain control circuit also is connected with described amplitude detection circuit by the fixed gain circuit;
Described fixed gain circuit, be used for reaching maximum in the gain that described automatic gain control circuit provides for described initial input signal, and when described gain back signal does not still meet the demands, provide the gain of fixed amplitude to the output signal of described automatic gain control circuit, and with the gained signal as new gain after signal output to described amplitude detection circuit.
6. an adaptive equilibrium method is characterized in that, may further comprise the steps:
Detect the amplitude fading state of gain back signal, obtain a testing result;
According to described testing result, for the initial input signal provides gain process, obtain described gain back signal, show that until described testing result described gain back signal meets the demands;
When described gain back signal meets the demands,, calculate the transmission range of described initial input signal according to the gain that finally provides for described initial input signal;
According to described transmission range,, obtain equalizing signal and output for the dominant frequency component and the DC component of described initial transmission signal provides corresponding gain.
7. according to the adaptive equilibrium method shown in the claim 6, it is characterized in that, also comprise:
Detect the amplitude fading state of described initial input signal, when described initial input signal meets the demands, directly control the step of described initial input signal output.
8. according to the adaptive equilibrium method shown in the claim 6, it is characterized in that, also comprise:
Described equalizing signal is carried out filtering eliminate the step of exporting behind the noise.
9. according to the adaptive equilibrium method shown in the claim 6, it is characterized in that, also comprise before the amplitude fading state of described detection gain back signal:
Whether the amplitude that detects described initial input signal is greater than the step of second predetermined threshold value;
During greater than described second predetermined threshold value, detect the step of the amplitude fading state of described initial input signal in the amplitude of described initial input signal.
10. according to the adaptive equilibrium method shown in the claim 6, it is characterized in that:
Reach maximum in the gain that provides for described initial input signal, and described gain back signal is not when meeting the demands still, for described gain afterwards signal the gain of fixed amplitude is provided, and with the gained signal as new gain after signal.
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