CN101605115B - Method for realizing passive oriented buoy digital de-multiplexer - Google Patents
Method for realizing passive oriented buoy digital de-multiplexer Download PDFInfo
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Abstract
The invention relates to a method for realizing a passive oriented buoy digital de-multiplexer. The input is passive oriented buoy composite signal undergoing A/D sampling and digital discretization, and the output is omnidirectional signal, east-west signal, north-south signal and locking state signal undergoing the digital discretization. The method comprises the following steps of: firstly, digitally filtering the composite signal to separate the omnidirectional signal, the dipole quadrature modulation signal and the pilot frequency signal, wherein the frequency of the pilot frequency signal is tracked and locked by a pilot frequency phase locked loop so as to further track and lock the phase of the pilot phase signal, provide the sinusoidal and cosine signals with the same frequency and phase, and demodulate the dipole signal undergoing quadrature modulation; further performing the lowpass filtering, outputting the omnidirectional signal, the east-west signal and the north-south signal; and locking the information whether the output value given by a judging module is valid. The method has the advantages of reducing the complexity of a buoy receiver, simplifying the hardware design, eliminating the influence of simulated elements, ensuring the balance of two dipole symmetrical channels and improving reliability and oriented precision.
Description
Affiliated technical field
The invention belongs to the crossing domain of Digital Signal Processing and sonar buoy, mainly is a kind of implementation method of passive oriented buoy digital de-multiplexer.
Background technology
Passive oriented buoy is a kind of marine monitoring instrument, and it not only can monitor the sound in the ocean, can also confirm the direction of sound.It comprises a combination acoustic vector sensors and a compass, and the buoy circuit is combined into one road composite audio signal to actual four road signals and passes to receiver through radio link.To the composite signal demultiplexing, carry out processing such as wave beam formation, time frequency analysis at receiving terminal for acoustic signal processor.The multiplexing orientation that is related to sound source of correct Solution is so demodulation multiplexer is the key link in the buoyage.
The demodulation multiplexer of previous passive oriented buoy receiver is realized complex circuit, poor reliability on the analog-digital hybrid circuit plate.For handling many pieces of buoys, the number of corresponding increase demodulation multiplexer, like this volume of buoy processor become gradually huge.For example, United States Patent (USP) 4,979,694 what introduce is a kind of passive oriented buoy demodulation multiplexer that adopts analog-digital hybrid circuit to realize.Before the buoy signal processor, also will have more a Special Equipment and be used for the demultiplexing processing in other words, this increases the complexity of buoy processor.In fact, adopting Digital Signal Processing is a better choice, for example can significantly reduce the complexity of buoy receiver, improves reliability etc.
The difficult point of demultiplexing is to the demodulation of the dipole signal of quadrature modulation in the composite signal, separates the timing requirement and can accurately lock frequency and the phase place of leading phase signals.Because dipole frequency modulating signal lower limit is very low, be low to moderate 10Hz, on the one hand near zero frequency.Take when leading phase signals, can receive the interference of modulation signal low frequency part.In this case, require the bandwidth of phase-locked loop very narrow; The crystal oscillator frequency of buoy circuit has error and can drift about on the other hand, causes 15kHz CF signal frequency drift.In this case, require the bandwidth of phase-locked loop very wide again.These two requirements are contradiction, adopt common phase-locked loop can't take into account this two aspects.If there is not solution, buoy will adopt the very high crystal oscillator of precision so, just increase the cost of buoy greatly.General buoy is deserted, and design principle is exactly to reduce its cost as far as possible, can use in enormous quantities.The present invention designs a kind of special software pilot tone phase-locked loop and solves above-mentioned contradiction, allows buoy to adopt cheap crystal oscillator, thereby has reduced the cost of raw material of buoy.
Demodulation multiplexer will have use value, and the state information of demodulation multiplexer also will be provided, and promptly whether the phase-locked loop in the demodulation multiplexer has losing lock.If losing lock, the result of back is exactly invalid so.The invention provides one and estimate the whether available method of output information.
United States Patent (USP) 4; 979,694 (Gibert R.Grado.Difar demultiplexer circuit [P] .United States PatentNumber:4,879; 694 Nov.7; 1989) introduced a part, concrete demodulation multiplexer circuit, but can't form a principle of demultiplexing clearly.Though the present invention is with reference to this patent; Therefrom recognize the form of composite signal; But the principle of demultiplexing is independent the derivation; Newly-designed demodulation multiplexer structurally is different from above-identified patent, and implementation method is novel, adopts innovation means such as Digital Signal Processing means, software pilot tone phase-locked loop, locking evaluation.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of prior art, a kind of implementation method of passive oriented buoy digital de-multiplexer is provided, it is used in based in the signal transmission subsystem in the passive oriented buoyage of the master of acoustic vector sensors.
For solving the problems of the technologies described above, the present invention proposes following technical scheme to realize: the implementation method of the demodulation multiplexer of this passive oriented buoy, and this digital signal processing method step is following:
(1), adopt the digital solution multiplexer, comprise pre-filtering module, quadrature demodulation module, digital pilot tone phase-locked loop module, pll lock judge module, five modules of output LPF abstraction module; Input is to sample by the passive oriented buoy composite signal of Digital Discreteization through A/D, and output is that signal is estimated in omnidirectional signal, thing signal, northern southern signal, the locking of Digital Discreteization; It realizes that on digital signal panel its input connects digital devices such as A/D data collecting card or digital radio receiver, and its output connects the buoy signal processor, and perhaps itself is exactly the part of buoy signal processor.
(2), omnidirectional signal, dipole orthogonal demodulation signal, pilot signal are isolated in pre-filtering module filtering from passive oriented buoy composite signal;
(4), the frequency of digital pilot tone phase-locked loop module tracking lock pilot signal, and then tracking lock leads the phase place of phase signals, offers quadrature demodulator with the sine and the cosine signal of homophase frequently;
(5), the quadrature demodulation module is to being carried out demodulation by the dipole signal of quadrature modulation, utilizes digital pilot tone phase-locked loop module to catch to lead phase signals to come demodulation dipole signal, obtains thing signal and northern southern signal;
(6), through exporting the further LPF of LPF abstraction module, output omnidirectional signal, thing signal, northern southern signal;
(7), judge through the pll lock judge module whether the output result is effective.
As preferably, described omnidirectional signal is the signal with omnidirectional's characteristic of taking from all directional hydrophone in the buoy; The thing signal is the signal with east-west direction dipole characteristics of taking from vector sensor and compass azimuth formation; The southern signal in north is to take from the northern southern signal to dipole characteristics of having of vector sensor and compass azimuth formation.
As preferably, said pre-filtering module adopts three unlimited responding digital filters of numeral, and one is low pass filter, is used to leach omnidirectional signal; Other two is band pass filter, and two band pass filter bandwidth frequency bands are different, and the band pass filter of a centre frequency 7.5k is used to leach pilot signal, and the band pass filter of a centre frequency 15k is used to leach modulation dipole signal.
As preferably, the quadrature demodulation module is that its composition comprises the two-way demodulation, and the two-way demodulation contains a multiplier and the simple signal from the pilot tone phase-locked loop respectively, and the simple signal of two-way is a quadrature, i.e. phase phasic difference 90 degree.
As preferably; Described output LPF abstraction module comprises three finite response digital filters; Be low pass filter, omnidirectional's passage, cosine passage, sinusoidal passage all carry out LPF at last and extract, and remove high fdrequency component; Reduce sample rate, export omnidirectional signal, northern southern signal and thing signal respectively.
As preferably, the pll lock judge module comprises the unlimited response filter of numeral and a comparator of two, and input is the two-way output of quadrature demodulation module; Be cosine passage demodulation output and sinusoidal passage demodulation output; The pll lock judge module carries out digital IIR LPF to two-way input earlier, falls sampling then, and relatively two-way is exported order of magnitude at last; This two-way output absolute value still is called output of cosine passage and the output of sinusoidal passage respectively; Judgment criterion is: when cosine passage output greater than sinusoidal passage output, then judge multiplexer result is effective, otherwise be judged as invalid.
As preferably; Numeral pilot tone phase-locked loop module comprises a phase loop and a frequency loop, respectively contains a loop filter, a shared numerically-controlled oscillator; Frequency loop is followed pilot signal; After the pilot signal to be locked, phase loop begins to follow the phase place of leading phase signals, and the phase place of phase signals is led in final locking.
The invention has the advantages that: the present invention proposes a kind of operation principle of passive oriented buoy demodulation multiplexer; A kind of method to the quadrature demodulation of modulation dipole signal digital is proposed; Propose a kind of digital signal processing algorithm of demodulation multiplexer, can on Universal Signal Processor, realize demultiplexing by software.So just reduce the complexity of buoy receiver, simplified hardware designs, eliminated the influence that analog component brings, can guarantee the balance of two-way dipole symmetric channel, improved reliability, orientation accuracy.Propose a kind of design of software pilot tone phase-locked loop, solved the problem of dipole signal demodulating process medium frequency phase place accurate tracking.Make buoy end multiplex circuit can adopt the not high cheap crystal oscillator of precision, thereby reduced the cost of raw material of single piece of buoy.The present invention proposes a kind of method of estimating pilot tone pll lock situation.
Description of drawings
Fig. 1 is the relation that shows between directed buoy self coordinate and the geographical coordinate;
Fig. 2 is that the frequency spectrum of composite signal is formed;
Fig. 3 is the composition frame chart of digital solution multiplexer;
Fig. 4 is digital pilot tone phase-locked loop block diagram;
Fig. 5 is the Z domain model of digital pilot tone phase-locked loop.
Embodiment
Below in conjunction with accompanying drawing and embodiment invention is described further:
The present invention is used for the composite signal of passive oriented buoy output is handled.Before introducing the demodulation multiplexer specific embodiments, need to understand earlier the knowledge of passive oriented buoy and composite signal thereof.The combined vectors transducer that passive directional sonobuoy (DIFAR) comprises is made up of the dipole sound vibration velocity transducer of omnidirectional's pressure hydrophone, two mutually orthogonals.Because the direction of buoy in water be at random, so it also comprises a compass and is used for the direction of perception self.Buoy also can produce rotation in water, need compass that the target bearing of sensor is corrected.Follow the form of directed buoy, see from the top of vector sensor, two dipole transducers are respectively along the X-direction and the Y direction of transducer.The Y axle of buoy is labeled as φ with the angle of magnetic north along clockwise direction, and target direction is labeled as θ with the angle of buoy Y axle along clockwise direction.Compass records the φ angle, and φ+θ is exactly the target orientation of magnetic north pole relatively.The signal that definition Y axle hydrophone receives is cosine channel signal or Y channel signal, and the information that X axle hydrophone receives is sinusoidal channel signal or X passage signal.The information that all directional hydrophone receives is omnidirectional signal, and is as shown in Figure 1.Passive oriented buoy is with four groups of information, and---one road omnidirectional signal, one road X axle dipole signal, one road Y axle dipole signal, one tunnel compass signal---is combined into one tunnel composite signal.The frequency band that composite signal takies is very narrow, on frequency band, belongs to audio signal, its frequency spectrum such as Fig. 2.Composite signal comprises omnidirectional signal, and the two-way dipole signal after the quadrature modulation, one road 15kHz are led phase signals and one road 7.5kHz pilot signal.The composition of composite signal that Here it is.Understand the specific embodiments that begins to introduce demodulation multiplexer after the above knowledge.
The present invention structurally is divided into 5 modules.Be respectively: pre-filtering module, quadrature demodulation module, digital pilot tone phase-locked loop module, pll lock judge module, output LPF abstraction module.
1, pre-filtering module
Buoy receiver at first needs demodulation multiplexer to carry out demultiplexing after obtaining composite signal, and it is exactly dipole signal and the pilot signal of isolating omnidirectional signal, quadrature modulation that demodulation multiplexer head handles one step ahead.The present invention has adopted three digital IIR (unlimited response filter) to accomplish.One is low pass filter, leaches omnidirectional signal; Other two band pass filter bandwidth frequency bands are different, and the band pass filter of a centre frequency 7.5k leaches pilot signal, and the band pass filter of a centre frequency 15k leaches modulation dipole signal.Like Fig. 3.
2, digital quadrature demodulation module
Two-way dipole signal on the carrier wave of 15kHz, is being symmetrically distributed in the leading about phase signals of 15kHz by quadrature modulation on the frequency spectrum.It is proportional with compass angle leading the phase signals phase place, needs digital pilot tone phase-locked loop to catch to lead phase signals to come demodulation two-way dipole, obtains EW (east-west to) signal and NS (North-south to) signal.
The quadrature demodulation process is explained as follows with formula:
If the signal that the Y axial sensor receives is Y=Acos θ, the signal that the X axle sensor receives is X=Asin θ, and the signal of composite signal behind bandpass filtering is:
S＝Ycos(ωt)-Xsin(ωt)+sin(ωt-φ)
------------(1)
Here suppose that initial phase is 0 degree.
The pilot tone pll lock is led phase signals sin (ω t-φ), sees two signals of quadrature off: cosine passage restituted signal cos (ω t-φ) and sinusoidal passage restituted signal-sin (ω t-φ).
Cosine passage demodulating process is following:
------------(2)
Through behind the low pass filter, only remaining
item;
Sinusoidal passage demodulating process is following:
--------------(3)
Through behind the low pass filter, only remaining
item.
In this demodulating process, compass information has been fused in EW and the NS signal.Further signal processing, for example cross-spectrum method or spatial matched filtering method etc. can be obtained θ+φ, obtain the absolute orientation of target in geomagnetic coordinates.
3, digital pilot tone phase-locked loop module
The effect of numeral pilot tone phase-locked loop is to catch the phase place of leading phase signals.Numeral pilot tone phase-locked loop is made up of following parts: software frequency detector, loop filter I, a numerically-controlled oscillator (DCO; Digital Contorl Oscillon), software phase detectors, loop filter II, a frequency multiplier, like Fig. 4.Loop filter I is than wide many of the bandwidth of loop filter II.This phase-locked loop can be regarded as two loops: a phase loop and a frequency loop.The frequency loop effect is the locking pilot signal, and the effect of phase loop is that the phase loop is led in locking.Since the noise bandwidth of frequency loop than phase loop have a lot of social connections many, locking process has fixing order: frequency loop arrives lock-out state prior to phase loop, phase loop pins and leads phase signals subsequently.Z domain model such as Fig. 5 of pilot tone phase-locked loop.
Pilot tone phase-locked loop essence is a feedback control system, pilot signal and the phase place of leading phase signals respectively as two reference signals, the phase signal that produces of DCO synchronously.Divide two stages synchronously: the phase I; The phase change of pilot signal is identical with the variation of DCO output phase signal; The pilot tone loop-locking, second stage is led the phase change of phase signals and the relation that DCO output phase signal keeps twice; This moment is the pilot tone loop-locking not only, leads the phase loop and also reaches locking.When the frequency of pilot signal or the phase place of leading phase signals changed, the aforementioned stable phase relation produced error, all can have feedback mechanism to act on DCO, reduces error as far as possible, keeps locking.Because noise is arranged, phase error exists all the time, and phase-locked loop has the effect of anti-noise.
The pilot tone phase-locked loop is described below leads the concrete realization of phase signals phase place synchronously: give the software frequency detector from the pilot signal of pre-filtering module output, another road input of software frequency detector is that numerically-controlled oscillator output original frequency is the reference signal of 7.5kHz.The actual frequency of pilot signal and 7.5kHz have some deviations.Frequency detector is a multiplier, frequency detector output direct current signal, high frequency time signal and broadband noise.Loop filter I is a low pass filter, and its effect is exactly try one's best filtering high frequency time and signal and partial noise, lets direct current signal pass through.The output of the output of loop filter I and loop filter II is added together, acts on DCO.The output of DCO is phase place and a reference signal.Loop filter I and II and phase value signal controlling DCO output and the frequency of signal.Wherein DCO exports the frequency and the input value u of reference signal
f(n) relation is:
f
ref＝2π[ω
0+K
0u
f(n)]/f
s
F wherein
sBe sample frequency, ω
0Be the centre frequency 7500Hz of DCO, K
0It is the gain of DCO.
It is thus clear that the input of DCO is if on the occasion of surpassing 7.5kHz with regard to the output reference signal frequency of DCO, if negative value then the output reference signal frequency of DCO be lower than 7.5kHz.
If t=n/f
sConstantly, DCO output phase signal does
T=(n+1)/f
sConstantly, the DCO output phase does
DCO output phase and input value u
f(n) relation is:
Is phase transition reference signal output:
Frequency discriminator, loop filter I, DCO constitute a feedback control system.In the starting stage; Pilot signal and reference signal multiply each other at frequency discriminator, positive number or negative as a result, and positive number control DCO output reference signal frequency strengthens; Negative control DCO output reference signal frequency reduces; Therefore the frequency of reference signal becomes big or diminishes, and through the process of a dynamic change, the frequency stabilization of last reference signal is got off.Reach stable after, the frequency of reference signal is consistent with pilot signal, frequency discriminator is exported direct current signal and high frequency time signal and noise, wherein the size of direct current signal is directly proportional with the difference of 7.5kHz with pilot signal.Behind loop filter I low pass filter, this direct current signal makes reference signal follow the variation of pilot signal through the frequency of DCO control reference signal.
After the pilot tone loop stability, lead the phase loop and also get into initial phase.
Cosine passage, loop filter II, DCO formation are led the phase loop in the quadrature demodulation module, are the phase-locked loops of another FEEDBACK CONTROL.Cosine passage restituted signal be restituted signal be again phase reference signal.Demodulation is multiplying, leads the phase signal of phase signals and reference signal and regulates DCO through loop filter II, and the phase place of DCO output is changed, and this phase place forms phase reference signal after being taken advantage of 2 times.Through such feedback regulation, finally making reference signal and the phase difference of leading phase signals is zero, i.e. phase signals is led in locking.
4, pll lock judge module
The input of locking judge module is the two-way output of quadrature demodulation module, i.e. cosine passage demodulation output and sinusoidal passage demodulation output.Like Fig. 3, the locking judge module carries out digital IIR LPF to two-way input earlier, falls sampling then, and relatively two-way is exported order of magnitude at last.This two-way output absolute value still is called output of cosine passage and the output of sinusoidal passage respectively.Judgment criterion is: when cosine passage output greater than sinusoidal passage output, then judge multiplexer result is effective, otherwise be judged as invalid.
5, output LPF abstraction module
Output LPF abstraction module adopts three same digital FIR low pass filters.Omnidirectional's passage, cosine passage, sinusoidal passage all carry out LPF at last and extract, and remove high fdrequency component, reduce sample rate, export omnidirectional signal, northern southern signal and thing signal respectively.
The above description of this invention does not have restricted, if those of ordinary skill in the art is enlightened by it, in the situation of the protection that does not break away from claim of the present invention, makes other malformation of the present invention and execution mode, all belongs to protection scope of the present invention.
Claims (7)
1. the implementation method of the demodulation multiplexer of a passive oriented buoy, it is characterized in that: this method step is following:
(1), adopt the digital solution multiplexer, comprise pre-filtering module, quadrature demodulation module, digital pilot tone phase-locked loop module, pll lock judge module, five modules of output LPF abstraction module; Input is to sample by the passive oriented buoy composite signal of Digital Discreteization through A/D, and output is omnidirectional signal, thing signal and the northern southern signal of Digital Discreteization, and last judged result is that signal is estimated in locking;
(2), omnidirectional signal, dipole orthogonal demodulation signal and pilot signal are isolated in pre-filtering module filtering from passive oriented buoy composite signal;
(3), the frequency of digital pilot tone phase-locked loop module tracking lock pilot signal, and then tracking lock leads the phase place of phase signals, offers the quadrature demodulation module with the sine and the cosine signal of homophase frequently;
(4), the quadrature demodulation module is to being carried out demodulation by the dipole signal of quadrature modulation, utilizes digital pilot tone phase-locked loop module to catch to lead phase signals to come demodulation dipole signal, obtains thing signal and northern southern signal;
(5), through exporting the further LPF of LPF abstraction module, output omnidirectional signal, thing signal and northern southern signal;
(6), judge through the pll lock judge module whether the output result is effective.
2. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1, it is characterized in that: described omnidirectional signal is the signal with omnidirectional's characteristic of taking from all directional hydrophone in the buoy; The thing signal is the signal with east-west direction dipole characteristics of taking from vector sensor and compass azimuth formation; The southern signal in north is to take from the northern southern signal to dipole characteristics of having of vector sensor and compass azimuth formation.
3. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1 is characterized in that: said pre-filtering module adopts three unlimited responding digital filters of numeral, and one is low pass filter, is used to leach omnidirectional signal; Other two is band pass filter, and two band pass filter bandwidth frequency bands are different, and the band pass filter of a centre frequency 7.5k is used to leach pilot signal, and the band pass filter of a centre frequency 15k is used to leach the dipole orthogonal demodulation signal.
4. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1; It is characterized in that: the quadrature demodulation module is that its composition comprises the two-way demodulation; The two-way demodulation contains a multiplier and the simple signal from the pilot tone phase-locked loop respectively; The simple signal of two-way is a quadrature, i.e. phase phasic difference 90 degree.
5. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1; It is characterized in that: described output LPF abstraction module comprises three finite response digital filters; Be low pass filter, omnidirectional's passage, cosine passage, sinusoidal passage all carry out LPF at last and extract, and remove high fdrequency component; Reduce sample rate, export omnidirectional signal, northern southern signal and thing signal respectively.
6. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1; It is characterized in that: the pll lock judge module comprises two unlimited response filters of numeral and a comparator; Input is the two-way output of quadrature demodulation module, i.e. cosine passage demodulation output and sinusoidal passage demodulation output, and the pll lock judge module is earlier to the digital IIR LPF of two-way input carrying out; Sampling is fallen then; Relatively two-way is exported order of magnitude at last, and this two-way output absolute value still is called output of cosine passage and the output of sinusoidal passage respectively, and judgment criterion is: when the output of cosine passage is exported greater than sinusoidal passage; Then judge multiplexer result is effective, otherwise be judged as invalid.
7. the implementation method of the demodulation multiplexer of passive oriented buoy according to claim 1; It is characterized in that: digital pilot tone phase-locked loop module comprises a phase loop and a frequency loop, respectively contains a loop filter, a shared numerically-controlled oscillator; Frequency loop is followed pilot signal; After the pilot signal to be locked, phase loop begins to follow the phase place of leading phase signals, and the phase place of phase signals is led in final locking.
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| EP2057753A2 (en) * | 2006-08-31 | 2009-05-13 | Nxp B.V. | Communication receiver with multiplexing of received signal, for receive space diversity |
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| EP2057753A2 (en) * | 2006-08-31 | 2009-05-13 | Nxp B.V. | Communication receiver with multiplexing of received signal, for receive space diversity |
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