CN1614963A - Timing locking test method for QAM and PSK signal - Google Patents
Timing locking test method for QAM and PSK signal Download PDFInfo
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Abstract
The invention uses difference of mean radius between integral symbol point and half symbol point as locking sign quantity for decision. The mean radius difference is compared with threshold at threshold comparator. According to rule of comparison the locking indicating signals are outputted. If the mean radius difference or its absolute value is greater than one positive threshold, then the timing recovery is decided as locking.
Description
Technical field
The invention belongs to digital signal transmission field, particularly a kind of QAM of being used for (quadrature amplitude modulation) and PSK (phase shift keying) signal timely lock detection method.
Background technology
In digital receiver, the data for correct recovery is sent need symbol timing recovery accurately.Subsequent module (as equalizer, decision device etc.) generally must regularly could start after the recovery locking, so need to judge timely that correctly regularly recovery locks.It is with the average power difference of integral symbol point and the half symbolic point sign amount as lock-in detection that a kind of traditional QAM (quadrature amplitude modulation) or PSK (phase shift keying) signal receiver timely lock detection method, thinks when this average power difference or its absolute value are set thresholding greater than certain and regularly recovers to lock.The technology of this respect can be referring to people's such as G.Karam paper " LOCK DETECTOR FOR TIMINGRECOVERY " (IEEE1996).
Fig. 1 realizes that this tradition timely locks the structural representation of detection.Integral symbol point data 101 (I (n), Q (n)) obtains integral symbol point power P (n)=I (n) through adder and multiplier 103
2+ Q (n)
2Half symbolic point data 102 (I (n-1/2), Q (n-1/2)) obtain half symbolic point power P (n-1/2)=I (n-1/2) through adder and multiplier 104
2+ Q (n-1/2)
2Integral symbol point power P (n) and half symbolic point power P (n-1/2) obtain current power difference e (n)=P (n)-P (n-1/2) through subtracter 105; Current power difference e (n) obtains average power difference E (m) through averager 106; Average power difference E (m) in threshold compataror 107 with thresholding relatively, the result outputs to lock indicator 108, if average power difference E (m) is greater than thresholding then be judged to be and regularly recover to lock the output lock indication signal.
This lock detecting method performance when signal quality is poor obviously descends, and it is too high to be embodied in the misjudgement and the probability of failing to judge, thereby causes the receiver system instability.Such as, when the white Gaussian noise interference ratio in the signal was serious, the statistical property of average power difference E (m) changed not obvious before and after locking, causes and can't select suitable lock-in threshold.This problem can't solve by adjusting on average counting of averager, because if it is very few on average to count, average power difference E (m) has serious shake, also can often surpass thresholding when should not being judged to locking; On the contrary, if on average count too much, then when should being judged to locking, average power difference E (m) remains a smaller value, does not also have obvious variation relatively with before the locking.
Summary of the invention
The purpose of this invention is to provide and a kind ofly new be used for QAM and psk signal timely locks detection method, make it under the poor situation of signal quality, before and after locking, obvious variation is arranged still in order to the sign quantitative statistics characteristic of judging locking, thereby judge accurately and regularly recover whether to lock.
This method with the mean radius difference of integral symbol point and half symbolic point as the sign amount of judging locking, this mean radius difference in threshold compataror with thresholding relatively, obtain comparative result and export to control state machine according to comparison rule.
Described integral symbol point with the extracting method of the mean radius difference of half symbolic point is: integral symbol point I/Q data (I (n), Q (n)) obtain integral symbol point power P (n)=I (n) through multiply-add operation
2+ Q (n)
2Half symbolic point I/Q data (I (n-1/2), Q (n-1/2)) obtain half symbolic point power P (n-1/2)=I (n-1/2) through multiply-add operation
2+ Q (n-1/2)
2Integral symbol point power P (n) obtains integral symbol point radius R (n)=P (n) through the extraction of square root computing
1/2, half symbolic point power P (n-1/2) obtains half symbolic point radius R (n-1/2)=P (n-1/2) through the extraction of square root computing
1/2Integral symbol point radius R (n) obtains current semidiameter e (n)=R (n)-R (n-1/2) with half symbolic point radius R (n-1/2) through subtraction; Current semidiameter e (n) obtains mean radius difference E (m) through average calculating operation.
Described comparison rule be if mean radius difference or its absolute value greater than a positive threshold value then then comparative result for effectively, otherwise be invalid.
The detection method key that timely locks of the present invention is that mean radius difference with integral symbol point and half symbolic point is as the sign amount of judging locking, make away from the symbolic point of initial point identical with the weight of the symbolic point of close initial point, even the white noise interference ratio is more serious, the statistical property of difference still has obvious variation between integral symbol point radius and the half symbolic point radius before and after locking, make it under the poor situation of signal quality, before and after locking, obvious variation is arranged still in order to the sign quantitative statistics characteristic of judging locking, thereby judge accurately and regularly recover whether to lock.
Method of the present invention is applicable to various quadrature amplitude modulation and various phase-shift keying modulating signal, includes but not limited to BPSk, QPSK, 8PSK, 16PSK, 16QAM, 32QAM, 64QAM, 128QAM, 256QAM etc.
Description of drawings
Fig. 1 is the structural representation that tradition timely locks detection method;
Fig. 2 is the vector space distribution schematic diagram of hour QPSK signal timing recovery locking front and back of white Gaussian noise;
Fig. 3 is white Gaussian noise vector space distribution schematic diagram before and after the locking of QPSK signal timing recovery when big;
Fig. 4 is a kind of specific implementation method of the present invention;
Fig. 5 is another specific implementation method of the present invention.
Embodiment
Be example at first below, operation principle of the present invention and validity are described with QPSK (4 phase shift keying) signal.
As shown in Figure 2, before timely locking, integral symbol point and half symbolic point are all incited somebody to action being distributed in the whole vector space (radius is the border circular areas of R3) at random, and the statistical property of integral symbol point and half symbolic point is consistent.Therefore, regularly recover the average power difference o'clock between half symbolic point of integral symbol before the locking and be tending towards 0.
After timely locking, in the absence of carrier wave and phase error, integral symbol point mainly is distributed in border circular areas A1, A2, A3 and the A4; Half symbolic point mainly is distributed in border circular areas B1, B2, B3, B4 and the B5, also has a spot of half symbolic point to be distributed in border circular areas A1, A2, A3 and the A4.After timely locking, exist under the situation of carrier wave or phase error, the A1 at integral symbol point place, A2, A3 and A4 zone will be that the circle rotation of R1 is distributed in the endless belt that mean radius is R1 along radius; The B1 at half symbolic point place, B2, B3, B4 and B5 zone will be that the circle rotation of R2 is distributed in the endless belt and B5 zone that mean radius is R2 along radius, and a spot of in addition half symbolic point that is distributed in border circular areas A1, A2, A3 and the A4 will be that the circle rotation of R1 is distributed in the endless belt that mean radius is R1 along radius.Because white Gaussian noise is more much smaller than the power of useful signal, thus A1, A2, A3, A4, B1, B2, B3, B4, the radius ratio R1 of B5, R2 is much smaller.Therefore, after regularly recovering to lock, the average power difference between integral symbol point and half symbolic point is a bigger positive number, so use traditional lock detecting method and lock detecting method provided by the invention can distinguish the statistical property of locking front and back easily.
As shown in Figure 3,, cause A1 because white Gaussian noise strengthens, A2, A3, A4, B1, B2, B3, B4, the radius of B5 increases near R1, the degree of R2.Therefore, can easily not distinguish, cause the validity of traditional lock detecting method obviously to descend to such an extent as to the statistical property of timing recovery locking back integral symbol point power and half symbolic point power is close.
Distribution situation among analysis chart 2 and Fig. 3 can be found: under the less and bigger two kinds of conditions of white Gaussian noise, the mathematic expectaion of integral symbol point radius all levels off to R1 after the locking, and the mathematic expectaion of half symbolic point radius all levels off to R1/4+R2/2+Rb/2.Traditional lock detecting method shown in Figure 1 basic reason that letter can descend when white Gaussian noise is big is to calculate in the process of integral symbol point power and half symbolic point power, be equivalent to increase the weight away from the distributed areas of initial point, it is little to cause statistical property to change before and after locking.Lock detecting method of the present invention has then solved this problem of traditional lock detecting method, make away from the distributed points of initial point identical with the weight of the distributed points of close initial point, even the white noise interference ratio is more serious, the statistical property of difference still has obvious variation between integral symbol point radius and the half symbolic point radius before and after locking.
As shown in Figure 4, a kind of checkout gear that timely locks of realizing according to the present invention comprises two groups of input traffics: integral symbol point I/Q data 401, half symbolic point I/Q data 402; Two adder and multipliers: adder and multiplier 403, adder and multiplier 404; Two extraction of square root devices: extraction of square root device 405, extraction of square root device 406; Subtracter 407, averager 408, threshold compataror 409, lock indicator 410.
Two groups of input traffics: integral symbol point I/Q data 401 and half symbolic point I/Q data 402, respectively with serial mode pairing input, i.e. corresponding one and half symbolic point I/Q data 402 of one group of integral symbol point I/Q data 401 (I (n), Q (n)) (I (n-1/2), Q (n-1/2)).The timing recovery circuit that integral symbol point I/Q data 401 and half symbolic point I/Q data 402 come from the receiver.The signal that receives is a qam signal.
Two adder and multipliers: adder and multiplier 403 and adder and multiplier 404 carry out the quadratic sum computing with the beat identical with half symbolic point I/Q data 402 with integral symbol point I/Q data 401.One group of integral symbol point I/Q of every input data 401, adder and multiplier 403 output integral symbol point power P (n)=I (n)
2+ Q (n)
2, every input one and half symbolic point I/Q data 402, adder and multiplier 404 output half symbolic point power P (n-1/2)=I (n-1/2)
2+ Q (n-1/2)
2Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource adder and multiplier 403 and adder and multiplier 404 carry out the quadratic sum computing in order to save, and corresponding output differs a constant multiple.
Two extraction of square root devices: extraction of square root device 405 and extraction of square root device 406 calculate the arithmetic square root of input value.An integral symbol point power P of every input (n), the operation of once extracting square root of extraction of square root device 405 obtains integral symbol point radius R (n)=P (n)
1/2Every input one and half symbolic point power P (n-1/2), the operation of once extracting square root of extraction of square root device 406 obtains half symbolic point radius R (n-1/2)=P (n-1/2)
1/2During actual the realization, extraction of square root device 405 and extraction of square root device 406 can use lut circuits to realize, the method for extraction of square root curve realizes also can to use sectional broken line to force into, also can use other special arithmetic units to carry out.Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource extraction of square root device 405 and extraction of square root device 406 extract square root computing in order to save, and corresponding output differs a constant multiple.
Subtracter 407: the difference of calculating two input signals.Every input one group of integral symbol point radius R (n) and half symbolic point radius R (n-1/2), subtracter 407 calculates their difference, obtains current semidiameter e (n)=R (n)-R (n-1/2).Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource subtracter 407 carries out subtraction in order to save, and corresponding output differs a constant multiple.
Averager 408: input signal is carried out statistical average.Can use accumulator to realize, also can use various low pass filters to realize.408 couples of current semidiameter e of averager (n) carry out smothing filtering, obtain mean radius difference E (m).Those skilled in the art should understand, can adjust the mean radius difference E (m) of output and the degree of approximation of the mathematic expectaion of current semidiameter e (n) by the parameter of revising averager 408, when on average counting of averager 408 abundant (bandwidth of low pass filter is enough narrow in other words), can think that the mathematic expectaion that the mean radius difference E (m) of averager 408 outputs is approximately equal to current semidiameter e (n) multiply by certain constant multiple.
Threshold compataror 409: mean radius difference E (m) is set thresholding with certain compare, when mean radius difference E (m) produces an index signal during greater than a positive threshold value.Those skilled in the art should understand, can be by adjusting this threshold value to adapt to different modulation systems and signal quality.
Lock indicator 410: be one and be used for exporting the state machine that locks with the losing lock signal according to the comparative result of threshold compataror 409 and current state.This state machine should comprise two states at least: locking and non-locking.At least should comprise an input signal: the mean radius difference of comparator output and the big or small comparison of thresholding.At least should comprise an output signal, be used for representing regularly recover at present whether to lock.Those skilled in the art should understand that according to different decision rules, lock indicator 410 can be a state machine that only comprises locking and two state exchanges of losing lock, also can be a state machine that comprises more other state exchanges.
As shown in Figure 5, the another kind of realizing according to the present invention timely locks checkout gear and comprises one group of input traffic: integral symbol point and half symbolic point alternate data 501, adder and multiplier 502, extraction of square root device 503, register 504, subtracter 505, averager 506, threshold compataror 507, lock indicator 508.
One group of input traffic: with half symbols cycle beat input integral symbol point and half symbolic point alternate data 501, this data flow is characterised in that, integral symbol is put I/Q data and half symbolic point I/Q data with alternately input of serial mode pairing, promptly import the combination (I (n) of one group of integral symbol point I/Q data earlier, Q (n)), and then import the combination (I (n-1/2), Q (n-1/2)) of one and half symbolic point I/Q data, circulate with this.Integral symbol point and half symbolic point alternate data 501 generally come from the timing recovery circuit in the receiver.The signal that receives can be a psk modulation signal.
Adder and multiplier 502: the quadratic sum of alternately calculating integral symbol point and half symbolic point alternate data 501 with half symbols cycle beat.The combination of one group of integral symbol point I/Q of every input data (I (n), Q (n)), adder and multiplier 502 output integral symbol point power P (n)=I (n)
2+ Q (n)
2, and then import the combination (I (n-1/2), Q (n-1/2)) of one and half symbolic point I/Q data, adder and multiplier 502 output half symbolic point power P (n-1/2)=I (n-1/2)
2+ Q (n-1/2)
2The output of adder and multiplier 502 is alternate data stream of integral symbol point power P (n) and half symbolic point power P (n-1/2).Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource adder and multiplier 502 carries out the quadratic sum computing in order to save, and corresponding output differs a constant multiple.
Extraction of square root device 503: alternately calculate integral symbol point radius and half symbolic point radius with half symbols cycle beat.An integral symbol point power P of every input (n), the operation of once extracting square root of extraction of square root device 503 obtains integral symbol point radius R (n)=P (n)
1/2And then import one and half symbolic point power P (n-1/2), the operation of once extracting square root again of extraction of square root device 503 obtains half symbolic point radius R (n-1/2)=P (n-1/2)
1/2The output of extraction of square root device 503 is alternate data stream of integral symbol point radius R (n) and half symbolic point power radius R (n-1/2).During actual the realization, extraction of square root device 503 can use lut circuits to realize, the method for extraction of square root curve realizes also can to use sectional broken line to force into, also can use other special arithmetic units to carry out.Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource extraction of square root device 503 extracts square root computing in order to save, and corresponding output differs a constant multiple.
Register 504: the integral symbol point radius R (n) that splits the output of squarer 503 with half symbols cycle beat carries out the delay in half symbols cycle with the alternate data stream of half symbolic point radius R (n-1/2).When register 504 be input as half symbolic point radius R (n-1/2) time, the output of register 504 just in time is integral symbol point radius R (n).
Subtracter 505: the difference of calculating integral symbol point radius R (n) and half symbolic point radius R (n-1/2) with the symbol period beat.As previously mentioned, when register 504 be input as half symbolic point radius R (n-1/2) time, the output of register 504 just in time is integral symbol point radius R (n), at this moment subtracter 505 carries out subtraction one time, obtain current semidiameter e (n)=R (n)-R (n-1/2), and export this difference with the symbol period beat.Those skilled in the art should understand, can adjust flexibly operational precision when hardware resource subtracter 505 carries out subtraction in order to save, and corresponding output differs a constant multiple.
Averager 506: input signal is carried out statistical average with the symbol period beat.Can use accumulator to realize, also can use various low pass filters to realize.506 couples of current semidiameter e of averager (n) carry out smothing filtering, obtain mean radius difference E (m).Those skilled in the art should understand, can adjust the mean radius difference E (m) of output and the degree of approximation of the mathematic expectaion of current semidiameter e (n) by the parameter of revising averager 506, when on average counting of averager 506 abundant (bandwidth of low pass filter is enough narrow in other words), can think that the mathematic expectaion that the mean radius difference E (m) of averager 506 outputs is approximately equal to current semidiameter e (n) multiply by certain constant multiple.
Threshold compataror 507: mean radius difference E (m) is set thresholding with certain compare, when the absolute value of mean radius difference E (m) produces an index signal during greater than a positive threshold value.Those skilled in the art should understand, can be by adjusting this threshold value to adapt to different modulation systems and signal quality.
Lock indicator 508: be one and be used for exporting the state machine that locks with the losing lock signal according to the comparative result of threshold compataror 507 and current state.This state machine should comprise two states at least: locking and non-locking.At least should comprise an input signal: the mean radius difference of comparator output and the big or small comparison of thresholding.At least should comprise an output signal, be used for representing regularly recover at present whether to lock.Those skilled in the art should understand that according to different decision rules, lock indicator 508 can be a state machine that only comprises locking and two state exchanges of losing lock, also can be a state machine that comprises more other state exchanges.
Use integral symbol point provided by the invention timely locks the detection method that timely locks that detects the sign amount with the mean radius difference conduct of half symbolic point, can be implemented under the relatively poor condition of signal quality with the resource of saving and work reliably.
Although the present invention is next specifically described with reference to its preferred embodiment, it should be appreciated by those skilled in the art, under the situation that does not break away from the spirit and scope of the present invention that the claims qualification is arranged, can carry out the various modifications of form and details to it.
Claims (4)
1. detection method that timely locks that is used for QAM and psk signal, it is characterized in that this method with the mean radius difference of integral symbol point and half symbolic point as the sign amount of judging locking, this mean radius difference is compared with thresholding in threshold compataror, obtain comparative result and export to control state machine according to comparison rule.
2. a kind of QAM of being used for as claimed in claim 1 and psk signal timely lock detection method, it is characterized in that the described integral symbol point and the extracting method of the mean radius difference of half symbolic point are: integral symbol point I/Q data (I (n), Q (n)) obtain integral symbol point power P (n)=I (n) through multiply-add operation
2+ Q (n)
2Half symbolic point I/Q data (I (n-1/2), Q (n-1/2)) obtain half symbolic point power P (n-1/2)=I (n-1/2) through multiply-add operation
2+ Q (n-1/2)
2Integral symbol point power P (n) obtains integral symbol point radius R (n)=P (n) through the extraction of square root computing
1/2, half symbolic point power P (n-1/2) obtains half symbolic point radius R (n-1/2)=P (n-1/2) through the extraction of square root computing
1/2Integral symbol point radius R (n) obtains current semidiameter e (n)=R (n)-R (n-1/2) with half symbolic point radius R (n-1/2) through subtraction; Current semidiameter e (n) obtains mean radius difference E (m) through average calculating operation.
3. a kind of QAM of being used for as claimed in claim 1 and psk signal timely lock detection method, if it is characterized in that described comparison rule for the mean radius difference greater than a positive threshold value comparative result for effectively, otherwise be invalid.
4. a kind of QAM of being used for as claimed in claim 1 and psk signal timely lock detection method, if it is characterized in that described comparison rule for the absolute value of mean radius difference greater than a positive threshold value comparative result for effectively, otherwise be invalid.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100542783A CN100379234C (en) | 2004-09-03 | 2004-09-03 | Timing locking test method for QAM and PSK signal |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2004100542783A CN100379234C (en) | 2004-09-03 | 2004-09-03 | Timing locking test method for QAM and PSK signal |
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| CN100379234C CN100379234C (en) | 2008-04-02 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102164002A (en) * | 2011-04-15 | 2011-08-24 | 南京理工大学 | Lock detection method for bit synchronization of all-digital receiver |
| CN110611543A (en) * | 2018-06-14 | 2019-12-24 | 扬智科技股份有限公司 | Timing lock identification method for timing recovery and signal receiving circuit |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6185259B1 (en) * | 1996-06-12 | 2001-02-06 | Ericsson Inc. | Transmitter/receiver for GMSK and offset-QAM |
| GB0009302D0 (en) * | 2000-04-15 | 2000-05-31 | Mitel Semiconductor Ltd | Quadrature amplitude modulation demodulation and receiver |
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2004
- 2004-09-03 CN CNB2004100542783A patent/CN100379234C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102164002A (en) * | 2011-04-15 | 2011-08-24 | 南京理工大学 | Lock detection method for bit synchronization of all-digital receiver |
| CN102164002B (en) * | 2011-04-15 | 2013-10-30 | 南京理工大学 | Lock detection method for bit synchronization of all-digital receiver |
| CN110611543A (en) * | 2018-06-14 | 2019-12-24 | 扬智科技股份有限公司 | Timing lock identification method for timing recovery and signal receiving circuit |
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