CN100463383C - Method and apparatus for detecting phase reversal of digital signal tone - Google Patents

Abstract

The invention discloses a digital signal phase reversal detection process and apparatus. Instead of using direct phase calculation, the invention realizes the phase detection by using the special relation between the phase gap of 2100Hz digital signal sampling points and by the reasonable evaluation. The sampling for each point only requires two multiply operations and one additive operation, and only three memory units, two multipliers, one accumulator and one arbiter are needed to realize the sampling, overcoming the flaws of technical complexity, poor adaptation and low dependability. The aim of the invention can be realized not only by the DSP general purpose, but also by FPGA. The invention can be applied in the combination communication system of voice and low speed data.

Description

A kind of phase reversal detecting method of digital signal sound and equipment

Technical field

The present invention relates to a kind of method and apparatus of realizing that in voice and low speed data mixing communication system the phasing back to the 2100Hz digital signal sound detects, belong to the signal tone detection technique in the communication field.

Background technology

In voice and low speed data mixing communication system, for distinguishing communication state or handling communication and set up flow process, often by means of some single-frequency or multi-frequency signal sound, for example, just stipulated in the agreement that the 2100Hz simple signal sound that contains the periodic inversion phase place forbids sound (echo canceller tone disabler) as answering tone or echo canceller G.168, G.165, V.25 with V.8 waiting.

G.168 with the agreement that G.165 is International Telecommunication Association (ITU-T) proposition about Echo Cancellation.Wherein stipulate, meet in the echo canceller of this agreement and should equip tone Detector, this tone Detector should be when detecting the signal of the 2100Hz signal tone that contains the periodic inversion phase place, can close echo canceller, and any other inband signaling, as the 2100Hz signal of voice and no phasing back, all cannot close echo canceller.For example when both call sides carried out data communication in modes such as MODEM before, both sides' terminal all can send the 2100Hz signal tone of periodic inversion phase place, need close echo canceller.

G.168, G.165, V.25 with V.8 wait in the agreement and stipulate, echo canceller forbids that sound transmission standard is: frequency range 2100Hz ± 15Hz, 2.6 seconds～4.0 seconds duration, every a phasing back of 450 milliseconds ± 25 milliseconds generations, phase change reaches 180 ° ± 10 ° in 1 millisecond.Examination criteria is: frequency range 2100Hz ± 21Hz, level range-31dBm0～-6dBm0, when when taking place phasing backs and phase change at 180 ° ± 25 ° for 450 milliseconds ± 25 milliseconds, detecting, if phase change between 0 °～± 110 °, need to guarantee detect less than, operate time 1 second with interior (to guarantee to detect the 2100Hz sound and to produce 2 phasing back at least), error rate should reach in per 100 hours and be no more than 10 times.

Tone Detector mainly comprises two parts, the one, and the detection of 2100Hz frequency, the 2nd, the detection of the phasing back of per 450 milliseconds of generations.The solution of first is very ripe, comprehensive at present, and easier, reliable, and that the solution of second portion is seen is very few.Phase reversal detecting method as far as is known is mainly conventional methods such as cutting method, correlation method, integration method, zero passage detection method anyway, though can deal with problems, often too complexity or reliability are not high.For example, United States Patent (USP) 6259750 is an integration method, and 5528632 is two correlation methods, all comparatively complicated.Because this input need be carried out in communication process always, if algorithm is too complicated, must waste a large amount of processor resources, and, the producing method of phasing back is a lot, and agreement there is no hard and fast rule, for example can adopt frequency discontinuity, the continuous mode of phase place to reach phasing back within a certain period of time, also can adopt modes such as frequency is constant, phase taper to reach phasing back, these conventional sense methods can't the various phasing back modes of good conformity.

Summary of the invention

The technical problem that the present invention solves provides a kind ofly can carry out detection method and equipment at the phasing back of above-mentioned digital signal sound, only need to use three mnemons, two multipliers, an adder and a decision device, can detect phasing back exactly, and detect the requirement that G.168 index meets and G.165 wait agreement fully.

The invention provides a kind of phasing back checkout equipment of digital signal sound, be used for realizing that adjacent 2 phase differences of digital signal sound are that 90 phasing backs when spending detect, comprising: mnemon A, B, C, multiplier D, E, adder F and decision device G;

Mnemon A, B, C connect successively, are respectively applied for the input quantification digital signal of delaying time and depositing three sampled points of setting;

The input of multiplier D links to each other with sampling input x (k) with the output of mnemon B;

The input of multiplier E links to each other with the output of mnemon A and the output of mnemon C;

The input of adder F links to each other with the output of multiplier D and the output of multiplier E;

The input of decision device G links to each other with the output of adder F, with the output valve of adder F and the limit value contrast of decision device G, judges whether phasing back takes place.

The phasing back that causes for SPA sudden phase anomalies detects, and three mnemon A, B, C preserve digital signal x (k-1), x (k-2), the x (k-3) that obtains quantizing, the current sampling point on the described k express time axle respectively; The span of decision device G limit value is :-sin205.4 ° of A ₀ ²～-sin300.4 ° A ₀ ², A ₀Amplitude for sampled input signal.

The phasing back that phasing back that causes for frequency discontinuity or unknown mode cause detects, and three mnemon A, B, C preserve digital signal x (k-1), x (k-19), the x (k-20) that obtains quantizing, the current sampling point on the described k express time axle respectively; The span of decision device G limit value is: A ₀ ²Sin218 °～A ₀ ²Sin313 °, A ₀Amplitude for sampled input signal.

In the span of described decision device G limit value, set one group of upper limit value and lower limit value, can be judged as phase place for the situation between upper lower limit value and may take place to reverse or may reverse.

The phase reversal detecting method of digital signal sound of the present invention is used for realizing that adjacent 2 phase differences of digital signal sound are that 90 phasing backs when spending detect, and the specific implementation step is:

The first step is the sequence x (i) that 8kHz carries out digital signal samples with the sample frequency, i=0, and 1,2,3... is input to three mnemon A, B, C and postpones;

Second step was connected to multiplier D with the output of sample sequence x (i) and mnemon B as input signal, and the output of mnemon A and C is connected to multiplier E as input signal, again the output of multiplier D and E is connected to adder F as input signal;

The 3rd goes on foot, and the output result among the adder F is delivered among the decision device G judge, reverses if the result of adder F, then judges phase place greater than the limit value of decision device G; If the result of adder F, then judges phase place less than the limit value of decision device G and reverses.

The phasing back that causes for SPA sudden phase anomalies detects, and three mnemon A, B, C preserve digital signal x (i-1), x (i-2), the x (i-3) that obtains quantizing respectively; The span of decision device G limit value is :-A ₀ ²Sin205.4 °～-A ₀ ²Sin300.4 °, A ₀Amplitude for sampled input signal.

The phasing back that phasing back that causes for frequency discontinuity or unknown mode cause detects, and three mnemon A, B, C preserve digital signal x (i-1), x (i-19), the x (i-20) that obtains quantizing respectively; The span of decision device G limit value is: A ₀ ²Sin218 °～A ₀ ²Sin313 °, A ₀Amplitude for sampled input signal.

In the span of described decision device G limit value, set one group of upper limit value and lower limit value, can be judged as phase place for the situation between upper lower limit value and may take place to reverse or may reverse; If greater than higher limit, judge that then phase place reverses, if less than lower limit, judge that then phase place reverses.

The characteristics that phase reversal detecting method of the present invention makes full use of phase difference between each sampled point of 2100Hz digital mono signal that 8kHz sampling obtains have realized the detection to the phasing back of 2100Hz signal tone dexterously, simple, effectively, operand is extremely low.Because the estimation of signal amplitude A0 must be finished in the frequency detecting process, thereby use this method only need do a secondary multiplication and an add operation to each sampled point, only need three mnemons, two multipliers, an adder and an arbiter to get final product, thereby weak points such as prior art complexity, bad adaptability, reliability be low have been overcome, both can use DSP, general processor to realize, and also can use FPGA to realize easily.Accuracy of detection meets the requirement of International Telecommunication Association's related protocol fully, can be conveniently used in voice and the low speed data mixing communication system.The inventive method reliability height, a large amount of experiment statisticses show that under various common user's communication environment, equivalent false drop rate has reached per 100 hours and has been no more than 2 times.

Description of drawings

Fig. 1 is a digital signal sound phasing back judgement schematic diagram of the present invention;

Fig. 2 phasing back assay device structures of the present invention schematic diagram;

Fig. 3 adopts the preferred embodiment schematic flow diagram of the inventive method;

Embodiment

With reference to digital signal sound phasing back judgement schematic diagram shown in Figure 1.Transverse axis is represented SPA sudden phase anomalies point and the phase difference θ+θ between any before it among Fig. 1 _d, the longitudinal axis is represented its sine value.This phasing back of mark " * " some expression allows to detect; Mark "." the no phasing back of this point of some expression, do not allow to detect.

In digital phone switching network, voice and low speed data all are that the sampling point quantized value with 8kHz is that unit transmits.If x (k) is the 2100Hz signal tone of 8kHz sampling, then

x(k)＝A ₀·cos(2πf ₀kT _s+α ₀)k＝0，1，2，3，…..................(1)

In the formula (1), A ₀Be amplitude, α ₀Be first phase, f ₀=2100Hz ± 21Hz, T _s=1/8000s is the sampling period, and k is a sampling sequence number.The phase place of adjacent 2 x of this signal tone (k), x (k+1) is respectively θ (k), θ (k+1), and the phase difference between them represents with Δ θ, then

Δθ＝θ(k+1)-θ(k)＝360°·f ₀·T _s.................................(2)

It is 93.6 °≤Δ θ≤95.4 ° that computing formula (2) obtains its value.Therefore not only irrelevant at the phase difference of adjacent two sampled points of no phasing back place with the first phase of signal, and be approximately 90 °, promptly

θ(k+1)≈θ(k)+90°.....................................................(3)

And in phasing back place, phase difference no longer has the relation of formula (3).If phasing back realizes that by SPA sudden phase anomalies variable quantity is θ _d, SPA sudden phase anomalies post-sampling point k then _dAnd the phase difference between its last sampled point should be Δ θ+θ _d

During phase-detection, it is very complicated directly to calculate its phase place by the sampled value of input signal, and to the required precision of DSP also than higher.The direct phase calculation of the ingenious avoidance of the present invention, the special relationship that makes full use of phase difference between the 2100Hz digital signal samples point realizes phase-detection.Its core is, before phasing back a bit, no matter whether be phase reversal point, all can be with the sine value of adjacent 2 phase differences of following formula approximate evaluation

$\sin (\mathrm{\θ}\left(k\right)-\mathrm{\θ}(k-1))$

$=\sin \left(\mathrm{\θ}\left(k\right)\right)\·\cos \left(\mathrm{\θ}(k-1)\right)-\cos \left(\mathrm{\θ}\left(k\right)\right)\·\sin \left(\mathrm{\θ}(k-1)\right)$

$\≈-\cos \left(\mathrm{\θ}(k+1)\right)\·\cos \left(\mathrm{\θ}(k-1)\right)-\cos \left(\mathrm{\θ}\left(k\right)\right)\·\cos \left(\mathrm{\θ}(k-2)\right)$

$=\frac{1}{A_0^2}[-x(k+1)\·x(k-1)-x\left(k\right)\·x(k-2)].....................\left(4\right)$

This differs sine value near-1 during phasing back, and then near 1, concrete value condition illustrates all the other situations in the back.And for before the phasing back a bit, adopt the account form on formula (4) the right, the result is indefinite between-1～1, so can detect phasing back in advance.

According to protocol requirement G.168, work as θ _dWhen being 180 ° ± 25 °, think qualified 2100Hz signal tone; Work as θ _dWhen being 0 ° ± 110 °, think underproof 2100Hz signal tone.For qualified 2100Hz signal tone, the span of Δ θ is 93.6 °≤Δ θ≤95.4 °.Because SPA sudden phase anomalies point is Δ θ+θ with its preceding phase difference between a bit _dSo, the Δ θ+θ of qualified and defective 2100Hz signal _dSpan is respectively (248.6 °, 300.4 °) and (16.4 °, 205.4 °), Δ θ+θ _dAnd the relation between its sinusoidal quantity as shown in Figure 1.As can be seen from Figure 1 allow to detect and do not allow to detect two zones and can divide:

Sine value then detects less than sin300.4 ° and is phasing back, and sine value then detects greater than sin205.4 ° and do not reverse for phase place.Sine value can detect also and can not detect between sin205.4 °～sin300.4 °, and this leaves enough adjustment leeway to detection.

So can be by phasing back checkout equipment as shown in Figure 2, mnemon A, B, C be buffer memory sampled signal x (k-1) respectively, x (k-2), x (k-3) can detect whether x (k-1) point is phase reversal point (being that phasing back occurs between k-1 and the k-2).For x (k-1) point, x (k) x (k-2)+x (k-1) x (k-3) on formula (4) the right can adopt multiplier D, E and the adder F among Fig. 2 to realize, limit value can be set in decision device-sin205.4 ° A ₀ ²～-sin300.4 ° A ₀ ²Get final product.Can also be at-sin205.4 ° A ₀ ²～-sin300.4 ° A ₀ ²In set one group of upper lower limit value, when the output of adder is between upper lower limit value, judge that phasing back may take place phase place, phasing back may not take place yet.

In addition, the 2100Hz signal tone that actual MODEM sends may not realized phasing back by SPA sudden phase anomalies, but by short time variable signal frequency, several sampling periods of process reach phasing back, as long as this process is finished in 1 millisecond, perhaps the unknown is what mode when causing phasing back, still can adopt the inventive method under these situations, only needs to estimate the sine value of the phase difference of multiple spot at interval.Because just approximate 90 ° of neighbouring sample point phase differences, as for 2100Hz ± 15Hz signal, the phase difference of neighbouring sample point is 93.6 °≤Δ θ≤95.4 °, and its central point is 94.5 °, think and avoid introducing accumulated error (4.5 ° multiples), adopt following formula to estimate

$\sin (\mathrm{\θ}\left(k\right)-\mathrm{\θ}(k-20))$

$=\sin \left(\mathrm{\θ}\left(k\right)\right)\·\cos \left(\mathrm{\θ}(k-20)\right)-\cos \left(\mathrm{\θ}\left(k\right)\right)\·\sin \left(\mathrm{\θ}(k-20)\right)$

$\≈\cos \left(\mathrm{\θ}(k-1)\right)\·\cos \left(\mathrm{\θ}(k-20)\right)+\cos \left(\mathrm{\θ}\left(k\right)\right)\·\cos \left(\mathrm{\θ}(k-19)\right)$

$=\frac{1}{A_0^2}[x(k-1)\·x(k-20)+x\left(k\right)\·x(k-19)].....................\left(5\right)$

In when, phasing back not taking place when, the scope that differs in the formula (5) between 20 sampled points is (93.6 °～95.4 °) * 20=72 °～108 °, if phasing back occurs between k and the k-20, the phase difference of then qualified and defective 2100Hz signal is respectively (227 °～313 °) and (38 °～218 °), be phasing back so sine value then detects less than sin313 °, sine value then detects greater than sin218 ° and does not reverse for phase place.Sine value can detect also and can not detect between sin218 °～sin313 °, and this leaves enough adjustment leeway to detection.

It should be noted that the situation for promptly finish phasing back in 20 sampling periods in less than will detect phasing back in continuous several sampling periods, at this moment should think a phasing back.

3 preferred embodiments that describe the inventive method in detail in conjunction with the accompanying drawings.Fig. 3 is the schematic flow diagram of the echo canceller switching control section in the echo canceller parts.The input signal of echo canceller is the digital signal of 8kHz sampling, methods such as the use DFT of program elder generation detect whether contain qualified 2100Hz signal in the input signal, also calculated the level value of 2100Hz frequency component at the same time, if do not have, then the Echo Cancellation function stays open, and continues to detect in the follow-up input signal whether contain the 2100Hz signal.If have, then use method of the present invention (as shown in Figure 2) to differentiate the 2100Hz signal and whether contain phasing back, if do not have, then the Echo Cancellation function stays open, and continues to detect in the follow-up input signal whether contain the 2100Hz signal; If phasing back is arranged, then the echo canceller function is closed, after this system will cut the data communication pattern.Experiment showed, that employing method and apparatus of the present invention is very effective, operand is extremely low, has significantly reduced the processor expense, and reliability is very high, and equivalent false drop rate has reached per 100 hours and has been no more than 2 times.

More than describe the concrete application of the inventive method in echo canceller in detail, but this should not be considered to be limitation of the scope of the invention.The inventive method also detects applicable to other phasing back that has the signal of similar characteristics therewith simultaneously.

Claims (8)

1. the phasing back checkout equipment of a digital signal sound is used for realizing that adjacent 2 phase differences of digital signal sound are that 90 phasing backs when spending detect, and it is characterized in that, comprising: mnemon A, B, C, multiplier D, E, adder F and decision device G;

Mnemon A, B, C connect successively, are respectively applied for the input quantification digital signal of delaying time and depositing three sampled points of setting;

The input of multiplier D links to each other with sampling input x (k) with the output of mnemon B;

The input of multiplier E links to each other with the output of mnemon A and the output of mnemon C;

The input of adder F links to each other with the output of multiplier D and the output of multiplier E;

The input of decision device G links to each other with the output of adder F, with the output valve of adder F and the limit value contrast of decision device G, judges whether phasing back takes place.

2. the phasing back checkout equipment of digital signal sound according to claim 1, it is characterized in that, the phasing back that causes for SPA sudden phase anomalies detects, three mnemon A, B, C preserve digital signal x (k-1), x (k-2), the x (k-3) that obtains quantizing, the current sampling point on the described k express time axle respectively; The span of decision device G limit value is :-A ₀ ²205.4 ° of sin～-A ₀ ²300.4 ° of sin, A ₀Amplitude for sampled input signal.

3. the phasing back checkout equipment of digital signal sound according to claim 1, it is characterized in that, the phasing back that phasing back that causes for frequency discontinuity or unknown mode cause detects, three mnemon A, B, C preserve digital signal x (k-1), x (k-19), the x (k-20) that obtains quantizing, the current sampling point on the described k express time axle respectively; The span of decision device G limit value is: A ₀ ²218 °～A of sin ₀ ²313 ° of sin, A ₀Amplitude for sampled input signal.

4. according to the phasing back checkout equipment of claim 2 or 3 described digital signal sounds, it is characterized in that, in the span of described decision device G limit value, set one group of upper limit value and lower limit value, can be judged as phase place for the situation between upper lower limit value and may take place to reverse or may reverse.

5. the phase reversal detecting method of a digital signal sound is used for realizing that adjacent 2 phase differences of digital signal sound are that 90 phasing backs when spending detect, and it is characterized in that performing step is:

The first step is the sequence x (i) that 8kHz carries out digital signal samples with the sample frequency, i=0, and 1,2,3... is input to three mnemon A, B, C and postpones;

Second step was connected to multiplier D with the output of sample sequence x (i) and mnemon B as input signal, and the output of mnemon A and C is connected to multiplier E as input signal, again the output of multiplier D and E is connected to adder F as input signal;

The 3rd goes on foot, and the output result among the adder F is delivered among the decision device G judge, reverses if the result of adder F, then judges phase place greater than the limit value of decision device G; If the result of adder F, then judges phase place less than the limit value of decision device G and reverses.

6. the phase reversal detecting method of digital signal sound according to claim 5, it is characterized in that, the phasing back that causes for SPA sudden phase anomalies detects, and three mnemon A, B, C preserve digital signal x (i-1), x (i-2), the x (i-3) that obtains quantizing respectively; The span of decision device G limit value is :-A ₀ ²205.4 ° of sin～-A ₀ ²300.4 ° of sin, A ₀Amplitude for sampled input signal.

7. the phase reversal detecting method of digital signal sound according to claim 5, it is characterized in that, the phasing back that phasing back that causes for frequency discontinuity or unknown mode cause detects, and three mnemon A, B, C preserve digital signal x (i-1), x (i-19), the x (i-20) that obtains quantizing respectively; The span of decision device G limit value is: A ₀ ²218 °～A of sin ₀ ²313 ° of sin, A ₀Amplitude for sampled input signal.

8. according to the phase reversal detecting method of claim 6 or 7 described digital signal sounds, it is characterized in that, in the span of described decision device G limit value, set one group of upper limit value and lower limit value, can be judged as phase place for the situation between upper lower limit value and may take place to reverse or may reverse; If greater than higher limit, judge that then phase place reverses, if less than lower limit, judge that then phase place reverses.

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