CN101252364B - New civil aviation ground and air communication twin channel constant module interference suppressing method and system - Google Patents

Abstract

Disclosed are a novel double-channel constant modulus interference suppression method and a system in the civil aviation ground-air communication, including that two VHF signals received by two antenna arrays are converted into two intermediate frequency digital signals which are respectively processed with filtering extraction and orthogonal transformation; two multiplex signals after the orthogonal transformation are transmitted into a monitor module for the judgments whether the interference signal enters a demodulator or not; the interference signal which enters the demodulator is processed with interference suppression; the interfered signals are transmitted into a carrier frequency estimation group and are respectively processed with carrier frequency estimation after the orthogonal transformation; then the signals are processed with wave trap; the carriers in the AM signals are trapped; the signals whose AM carriers are eliminated are transmitted into a self-adaptive constant modulus interference suppression module for the extraction of the constant modulus interference signal; the extracted interference signals are processed with self-adaptive cancellation; the output signals after the self-adaptive cancellation are processed with demodulation for filtering the high frequency noise, and then are transmitted into a D/A converter to output audio signals. The double-channel constant modulus interference suppression method and the system can overcome the situation of wrong acquisition of the constant modulus array; thereby, the stability of the self-adaptive interference suppression system is improved effectively.

Description

A kind of new civil aviation ground and air communication twin channel constant module interference suppressing method and system

Technical field

Present invention relates in general to a kind of self-adapting interference suppression method and system that is used for civil aviation air-ground communication.Specifically, a kind ofly can overcome the constant mode array error capture and improve the civil aviation air-ground communication quality more effectively, ensure a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method and the system of flight safety thereby relate to.

Background technology

Very high frequency(VHF) (VHF) communication is most important means in the present civil aviation air-ground communication, and its stability and reliability directly affect flight safety.

The VHF ground-to-plane radio adopts the working method of band carrier wave double-sideband amplitude modulation (DSB-AM), half-duplex operation, operating frequency range is 118.0MHz to 136.975MHz, channel spacing is 25KHz, and 760 communication channels can be provided, and these channels can be multiplexing in wide region.Because it is not outstanding that external radio control system and strictness thereof, blank pipe radio are done with regard to problem, the VHF ground-air communication equipment that they produce is not all considered anti-interference problem.But along with the fast development of enterprise of China civil aviaton and telecommunications industry in recent years, electromagnetic environment is increasingly sophisticated at home, and the degree that civil aviaton's radio-specific frequency is disturbed is serious day by day.With regard to interference source, mainly contain paging centers's transmitter, high-power cordless telephone, rural f-m broadcast station, vehicle radio station etc., these interference sources have permanent envelope trait.At present, the general passive non-technological means such as changing frequency, monitoring and examination that adopts of civil aviaton can not tackle the problem at its root, and radio interference becomes influences one of safety of civil aviation ground major hazard source.

Proposed among the patent application 200410075232.X to be used for the method and apparatus that the AM receiver suppressor pulse disturbs, relative pulse disturbs comparatively complicated situation in the civil aviation air-ground communication but be not suitable for.BJ University of Aeronautics ﹠ Astronautics develops the Technology Park based on the automatic dependent surveillance of very high frequency(VHF) data chainning (ADS) system, this system can carry out the interference prediction assessment of the interference analysis of VHF ground-to-plane radio and pre-newly-built VHF ground-to-plane radio, pre-assigned frequency, thus provide a series of for assignment, rational usable frequencies.The speech optimization technique that telephone system adopts in the civil aviaton be a kind of based on one main with different location VHF voice signal frequently, two be equipped with, the voice process technologies of three emergent configurations, each road is handled in real time with the different location of frequency signal, thereby acquisition voice quality parameters, the mass parameter that obtains is compared, select Optimal Signals and output to controller's panel.But they all can not be from removing the interference the civil aviation air-ground communication in essence.

In the prospectus of patent application 200710057268.9, a kind of civil aviation ground-air communication self-adaptive disturbance restraining method and system based on constant mode array proposed, it is to utilize constant mode array to extract constant modulus signals, again with its reference signal as the adaptive cancellation device, carry out adaptive cancellation, thereby obtain the earth-space communication signal.Constant mode array is a kind of blind adaptive Beam-former, and its weight coefficient can utilize constant modulus algorithm to upgrade, and has fast convergence rate, calculates simple performance, and the performance that signal recovers is insensitive to the structure of array.Therefore patent application 200710057268.9 from the angle of signal processing proposed a kind of can be from eliminating the method for common permanent mould interference signal the civil aviation air-ground communication in essence.

Yet proved already, if the kurtosis of non-constant modulus signals less than 2, constant mode array also can be caught non-constant modulus signals.The signal that is adopted in earth-space communication is band carrier wave double-sideband amplitude modulation signal, and its kurtosis is less than 2, so constant mode array might converge to band carrier wave double-sideband amplitude modulation signal rather than constant modulus signals, thereby produces error capture.The performance of constant mode array lock-on signal is relevant with the relative power of initial weight vector and array output end signal.Be 2 situation for source signal and array number, constant mode array might be caught has more powerful information source.

Summary of the invention

Technical problem to be solved by this invention is, provide a kind of and can improve the civil aviation air-ground communication quality, ensure flight safety, also can be used in other communication system, improve a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method and system that receptivity overcomes the signal error capture.

The technical solution adopted in the present invention is: a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method and system, and wherein method includes following steps:

(1) the two-way very high frequency(VHF) signal that two antenna array is received is separately converted to intermediate-freuqncy signal;

(2) the two-way intermediate-freuqncy signal that down-conversion is obtained is carried out analog-to-digital conversion respectively;

(3) the two-way digital intermediate frequency signal after the analog-to-digital conversion is carried out filtering extraction respectively;

(4) signal behind the filtering extraction is carried out orthogonal transform, real signal is become complex signal;

(5) the two-way complex signal after the orthogonal transform is sent into monitor module, judge whether signal is interfered, if the noiseless step (9) that changes over to changes step (6) over to if having to disturb;

(6) on the known basis of amplitude-modulated signal carrier frequency frequency range, the signal after the orthogonal transform is carried out carrier frequency estimate;

(7) with the carrier frequency frequency estimation as the reference signal, carry out trap, the carrier wave in the amplitude-modulated signal is fallen into;

(8) signal that will remove modulated subcarrier technique is sent into the self-adaption constant mould and is disturbed and suppress module and carry out the extraction of permanent mould interference signal, and the interference signal of having extracted is carried out adaptive cancellation;

(9) to step (5) or step (8) both one of the state no interference signal exported carry out demodulation, again through low pass filter filters out high frequency clutter, carry out digital-to-analogue conversion at last and export audio signal clearly.

(1) step was converted into intermediate-freuqncy signal with the very high frequency(VHF) signal and finishes by low noise high-frequency amplifier, three grades of frequency mixers and automatic gain control circuit.

(4) described orthogonal transform of step is in complex field the linear convolution mixed model to be converted to be convenient to the linear instantaneous mixed model that constant modulus signals extracts.

(5) step was sent the complex signal after the orthogonal transform into monitor module and judges and utilize the coefficient correlation of two paths of signals to judge, comprised the steps: to calculate the coefficient correlation ρ of two paths of data; Judge whether greater than threshold value th; Show that greater than threshold value th usefully empty signal of communication is not interfered, get wherein one road signal and send into demodulator; Otherwise be subjected to interference signal to send into carrier frequency estimation group and trapper group two-way.

(6) step is described carries out carrier frequency to the signal after the orthogonal transform and estimates, is to utilize the Ge Ceer algorithm to carry out carrier frequency to estimate.

(7) step fell into the carrier wave in the signal and is based on constant mode array and captures kurtosis sometimes and carry out less than this phenomenon of non-constant modulus signals of 2, and the signal kurtosis avoids constant mode array the error capture phenomenon to occur greater than 2 thereby carrier wave falls into the back.

The extraction of described interference signal of (8) step is the blind extraction that the permanent envelope trait that utilizes common interference to have is carried out permanent mould interference signal; And utilize the adaptive cancellation technology that the permanent mould interference signal of having extracted is offseted, as desired signal, the one tunnel is subjected to interference signal as input signal after orthogonal transform with the constant modulus signals of constant mode array output.

It is to adopt envelope-demodulation method that (9) step was carried out demodulation to state no interference signal, after the signal demodulation again through low pass filter filters out high frequency clutter.

A kind of new civil aviation ground and air communication twin channel constant module Interference Suppression System includes the two antenna array of received signal; The signal that two antenna array received is carried out signal processing and continuous successively radio frequency processing group, mould/number conversion group and Digital Down Convert group; The orthogonal transform group that links to each other and the digital signal of its output is carried out orthogonal transform with the Digital Down Convert group; The monitor module that orthogonal transform group output signal is judged; The interference signal that has to monitor module output is carried out the carrier frequency estimation group that carrier frequency is estimated; As the reference signal, signal is carried out the trapper group of carrier suppressed with the carrier frequency frequency estimation; The interference signal that has to the output of trapper group disturbs the self-adaption constant mould of inhibition to disturb the inhibition module; The demodulator that the interference suppression signal that the state no interference signal and the self-adaption constant mould interference inhibition module of monitor module output are exported carries out demodulation; The D/A that links to each other with the output of demodulator is exported with the audio frequency that links to each other with D/A; Wherein, described two antenna array by the antenna of two-way parameter unanimity form, the radio frequency processing group is made up of RF processing unit, mould/number conversion group is made up of A/D converter, the Digital Down Convert group is made up of the Digital Down Convert unit; Described orthogonal transform group is made up of the orthogonal transform unit of two-way parameter unanimity, carrier frequency estimation group by the carrier frequency estimation unit form, the trapper group is made up of trapper.

Described radio frequency processing group includes two groups and links to each other successively: low noise amplifier, the first bandpass filtering amplifying circuit, one-level mixting circuit, the second bandpass filtering amplifying circuit, secondary mixting circuit, the 3rd bandpass filtering amplifying circuit, voltage-controlled attenuator, intermediate level circuit, three grades of mixting circuits, four-tape pass filter amplifying circuit, the output of intermediate level circuit also connects detecting circuit, detecting circuit also links to each other with voltage-controlled attenuator by comparator, and three grades of mixting circuits also connect three local oscillation circuits; Wherein: three grades of mixting circuits between two groups link to each other by three local oscillation circuits, and the one-level mixting circuit between two groups links to each other by the first frequency synthesizer, and the secondary mixting circuit between two groups links to each other by the second frequency synthesizer; Low noise amplifier in two groups connects first antenna and second antenna respectively, and the first frequency synthesizer also is connected crystal oscillating circuit respectively with the second frequency synthesizer.

A kind of new civil aviation ground and air communication twin channel constant module interference suppressing method of the present invention and system, in characteristics that taken into full account civil aviation air-ground communication and civil aviation air-ground communication under the prerequisite of common interference source characteristic, carry out the disturbance restraining method that constant modulus signals extracts after the first carrier suppressed that proposes, avoid the constant mode array error capture to amplitude-modulated signal dexterously, improved the jamproof stability of civil aviation air-ground communication system.The present invention considers that civil aviation air-ground communication can not be subjected to two or more interference in most cases, and noise power can ignore far below disturbing and the power of useful signal, thereby the employing two antenna array; Secondly, the present invention utilizes permanent mould blind signal processing technology and adaptive interference cancellation technology, need not to use any reference signal, can eliminate the outside permanent mould that has a strong impact on VHF radio station receptivity and disturb, and improves signal interference ratio; In addition, utilize the arrowband characteristics of signal in the civil aviation air-ground communication that the linear convolution mixed model is converted to the linear instantaneous mixed model, simplified the complexity of Blind Source signal processing effectively.Method of the present invention is practical, cost is low, and can be used in other AM receiver.The present invention not only can solve interference problem present in the civil aviation air-ground communication well, and can carry out the upgrading and the maintenance of system according to following actual conditions at any time.

Description of drawings

Fig. 1 is the employed a kind of new civil aviation ground and air communication twin channel constant module Interference Suppression System block diagram of the inventive method;

Fig. 2 is that the radio frequency processing group constitutes block diagram;

Fig. 3 is the orthogonal transform unit structural representation;

Fig. 4 is the monitor module workflow diagram;

Fig. 5 is a Goertzel algorithm recursion flow chart;

Fig. 6 is the trapper structural representation;

Fig. 7 is the constant mode array composition frame chart;

Fig. 8 is the adaptive interference canceller composition frame chart;

Constant mode array output signal determined property result did not add up design sketch when Fig. 9 added trap;

Figure 10 a is former voice signal waveform effect figure;

The voice signal waveform effect figure of the direct demodulation of Figure 10 b mixed signal;

Figure 10 c is the voice signal waveform effect figure of demodulation after adaptive disturbance suppresses.

Embodiment

Below in conjunction with the drawings and specific embodiments describing in detail to a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method of the present invention and system.

A kind of new civil aviation ground and air communication twin channel constant module interference suppressing method of the present invention, fully taking into account beechnut, to be subjected to the situation of two or more interference simultaneously few, noise power is far below the power of interference and useful signal in addition, can ignore, thereby adopt the binary channels receiving system.From the common interference signal is constant modulus signals and useful signal is the angle of non-constant modulus signals, handles by the signal that the two-way receive path is received, and realizes the Adaptive Suppression of disturbing.Specifically be to adopt first trap as shown in Figure 1 to carry out the civil aviation ground-air communication self-adaptive Interference Suppression System that constant modulus signals extracts again, come the interference in the Adaptive Suppression earth-space communication, improve communication quality, may further comprise the steps:

The first step will be separately converted to intermediate-freuqncy signal by the two-way very high frequency(VHF) signal that two antenna array receives.It is the circuit that adopts as shown in Figure 2, the radio frequency processing of the signal that array antenna 1 and 2 is received by forming by low-noise high-frequency amplifier, three grades of frequency mixers and automatic gain control circuit (empty frame part among Fig. 2), radio signal is converted into the 1.25MHz intermediate-freuqncy signal after by radio frequency processing, so that follow-up signal is handled.In the present embodiment, circuit such as described low-noise high-frequency amplifier, three grades of frequency mixers and automatic gain control circuit are realized by existing circuit or principle.Three grades of intermediate frequencies that obtain after three grades of mixing are respectively 465MHz, 70MHz, 1.25MHz.

In second step, the two-way intermediate-freuqncy signal that down-conversion obtains is carried out analog-to-digital conversion respectively.

Respectively the two-way analog if signal of radio frequency processed group output is implemented analog-to-digital conversion by the A/D conversion group, thereby reduce follow-up Design of Digital Filter requirement, adopted the scheme of over-sampling in the present embodiment, the actual sample rate of using is 5MHz, sampling resolution 12bit.

In the 3rd step, the two-way digital intermediate frequency signal after the analog-to-digital conversion is carried out the Digital Down Convert filtering extraction respectively.

Respectively the two ways of digital signals of analog-to-digital conversion output is carried out filtering extraction by described Digital Down Convert group, data transfer rate is dropped to suitable degree from 5MSps, purpose is to improve real-time and reduce the operand that follow-up signal is handled.In the present embodiment, used the two-stage bandpass filtering to extract, extracted 5 times at every turn, last sample rate drops to 200KSps.

The 4th step, the signal behind the filtering extraction is carried out orthogonal transform, real signal is become complex signal.The two-way digital medium-frequency signal is carried out orthogonal transform, after the orthogonal transform real signal is become complex signal, in complex field the linear convolution mixed model is converted to and is convenient to the linear instantaneous mixed model that constant modulus signals extracts.

The signal that array antenna 1 and 2 receives among Fig. 1 is that the linear hybrid of source signal different delay is the convolution mixing of source signal, but because in the VHF beechnut, it is 25KHz that amplitude-modulated signal is propagated bandwidth, carrier frequency (118.00MHz～136.975MHz) very little with respect to signal, and the spacing of reception antenna is set to half-wavelength, the time delay of two antennas of signal arrival this moment does not cause the variation of two antenna receiving signal envelopes, the time delay of signal between different antennae can be reduced to phase shift so, so Blind Signal Extraction linear convolution mixed model can be reduced to the linear instantaneous mixed model.Because it is closer that array element is separated by, and the flying height of aircraft is higher, and aircraft is with respect to the angle approximately equal of two array-element antenna so, so signal is the same to the Doppler frequency shift of two antennas.Known again aircraft all flies at a constant speed in the flight period in major part, so establish the constant f of the Doppler frequency of signal _d(t)=f _dBecause civil aviaton's VHF communication system has high s/n ratio, therefore in Interference Suppression System, do not consider The noise simultaneously.Suppose that array element 1 is the zero time delay reference array element, array element 1,2 plural form that receives signal is respectively so:

x(t)＝As(t) (1)

In the formula

Be the observation signal vector,

With

Be respectively useful and dried baseband signal with regard to signal, f _oBe carrier frequency,

Be hybrid matrix, a ₁: a ₂Represent the amplitude mixed proportion of two source signals, τ ₁And τ ₂Be the time delay of array element 2 with respect to two information sources.Find out thus, we complex field with civil aviation air-ground communication in the model equivalence of received signal be the linear instantaneous mixed model.

Described orthogonal transform is in that (x represents two paths of signals x as shown in Figure 3 ₁, x ₂In a road; x _hExpression and the corresponding two-way complex signal of x x _H1, x _H2In a road) orthogonal transform unit in carry out, to the two paths of signals x behind the filtering extraction ₁, x ₂Carry out orthogonal transform, real signal is transformed into complex signal x _H1, x _H2, the complex signal that obtains is sent into monitor module.

FIRQ among Fig. 3 is a Hilbert filter, and its coefficient satisfies:

$h_q\left(n\right)=\frac{1}{\mathrm{\π}(n-M/2)}[1-{(-1)}^{n-M/2}]w\left(n\right)$ (1≤n≤M+1) (2)

In the formula (2), M is a filter order, and w (n) is the Blackman window, satisfies following formula:

W(n)＝0.42-0.5cos(2πn/(M+2))+0.08cos(4πn/(M+2))(1≤n≤M+1) (3)

FIRI among Fig. 3 is a delayer, M/2 the unit of delaying time, and M gets 88 in the present embodiment.

The two paths of signals x of Digital Down Convert group output ₁, x ₂Respectively by forming in-phase component x separately behind FIRI and the FIRQ _1I, x _2IWith quadrature component x _1Q, x _2Q, merge formation two-way complex signal x at last _H1, x _H2:

x _h1＝x _1I+j*x _1Q

x _h2＝x _2I+j*x _2Q (4)

The 5th step, the complex signal after the orthogonal transform is sent into monitor module judge, judge whether signal is interfered, if the noiseless step 9 that changes over to changes step 6 over to if having to disturb.

Its workflow of described monitor module comprises the steps: to import two paths of data x as shown in Figure 4 _H1And x _H2Calculate the coefficient correlation ρ of two paths of data; Judge whether greater than threshold value th; Then carry out demodulation greater than threshold value th; Otherwise enter carrier frequency estimation group and trapper group.

Its computing formula of coefficient correlation of calculating two paths of data in the described monitor module is as follows:

$\mathrm{\&rho;}=\left|\frac{E\{x_{h1}\left(n\right)\&CenterDot;{{\mathrm{<figure-callout\; id="2"\; label="x\; h"\; filenames="S2008100520852E00031.png"\; state="\{\{state\}\}">x</figure-callout>}}_h}^{*}\left(n\right)\}}{\sqrt{E\left\{{\left|x_{h1}\left(n\right)\right|}^2\right\}\&CenterDot;E\left\{{\left|x_{h2}\left(n\right)\right|}^2\right\}}}\right|---\left(5\right)$

Wherein () ^*The expression conjugate operation, statistical expection is asked in E () expression.

If coefficient correlation ρ just can determine that less than preset threshold th received signal is interfered, two paths of signals is sent into carrier frequency estimation group and trapper group; Otherwise judge that signal is not interfered, wherein one road signal is directly sent into demodulator and is carried out demodulation.Threshold value th can be made as one and approach 1 numerical value, is made as 0.9901 in the present embodiment.

In the 6th step, on the known basis of amplitude-modulated signal carrier frequency frequency range, the signal behind the filtering extraction is carried out carrier frequency estimate.It is to orthogonal transform group output signal x in carrier frequency estimation group that described carrier frequency is estimated _H1, x _H2, utilize Ge Ceer

(Goertzel) algorithm carries out the carrier frequency estimation, and purpose is to provide frequency initial value f for two trappers in the trapper group _Kmax1, f _Kmax2, to improve the convergence rate of trapper.

Wherein the Goertzel algorithm of carrier frequency estimation unit employing is to utilize twiddle factor

Periodicity

DFT (discrete Fourier transform) operation table is shown as the linear filtering computing, and the form of calculus of differences makes that its recursion is better.Fig. 5 provides Goertzel algorithm recursion flow chart (f _KmaxExpression f _Kmax1, f _Kmax2In one), its recursive expression is:

$v_k\left(n\right)=2\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="S2008100520852E00031.png"\; state="\{\{state\}\}">cos</figure-callout>}\frac{2\mathrm{\&pi;k}}{N}{v}_k(n-1)-v_k(n-2)+x_h\left(n\right)---\left(6\right)$

$f_k\left(n\right)=v_k\left(n\right)-V_N^k{v}_k(n-1)---\left(7\right)$

In the present embodiment, the N in formula (6), the formula (7) gets 200K, and k is for needing the Frequency point in search rate interval, and the initial condition of formula (6) is made as v _k(1)=v _k(2)=0, n=0,1 ..., N ₁, N ₁Get N/10 (being 20K), x _h(n) the two-way complex signal x that exports for monitor module _H1, x _H2In road signal, output f _k(n) be the frequency spectrum of this road signal respective frequencies point k.Present embodiment adopts the idiographic flow of estimating based on Goertzel algorithm carrier frequency to be:

(1) at each Frequency point k, to n=0,1 .., N ₁Iterative computation formula (6) is then at n=N ₁Calculating formula (7), thus the frequency spectrum (in the present embodiment, Frequency point k is in estimating that with carrier frequency initial value is that 50KHz is that L gets 101 in the frequency separation of center ± 500Hz, i.e. 10Hz at interval between the Frequency point) of L Frequency point obtained;

(2) ask L Frequency point frequency spectrum f _k(N1) the maximum corresponding Frequency point f of amplitude in _Kmax(promptly to L f that puts _k(N ₁) delivery, ask the maximum in these mould values), and with this carrier frequency estimated value f _KmaxFor renewal frequency interval in center is [f _Kmax-10Hz, f _Kmax+ 10Hz];

(3) frequency spectrum that uses new sampled data to restart L Frequency point to the frequency separation that upgrades calculates, and reaches N once more at sampled point ₁The time ask the maximum corresponding Frequency point f of amplitude in L the Frequency point frequency spectrum _Kmax, with the f that obtains this moment _KmaxFrequency initial value for adaptive notch filter.

In the 7th step, as the reference signal, carry out adaptive notch with the carrier frequency frequency estimation, carrier wave in the amplitude-modulated signal is fallen into, remove am signals kurtosis behind the carrier wave greater than 2, constant mode array can not converge to kurtosis greater than 2 signal, thereby has avoided constant mode array error capture to occur.

Described trapper group is formed the (expression of x ' (n) two paths of signals x ' by two-way adaptive notch filter as shown in Figure 6 ₁(n), x ' ₂(n) road in), first via adaptive notch filter input signal has: the signal terms x of monitor module output _H1Estimate output valve f with carrier frequency _Kmax1, the second road adaptive notch filter input signal has: the signal terms x of monitor module output _H2Estimate output valve f with carrier frequency _Kmax2, signal x ' behind the output two-way trap ₁(n) and x ' ₂(n) send into the self-adaption constant mould and disturb the inhibition module, be used for the extraction of constant modulus signals.

The groundwork process of Fig. 6 trapper is the signal x of monitor module output _hBy iir filter, the error signal x ' that carrier wave is removed in output (n):

x(n)＝x _h(n)+a(n)x _h(n-1)+x _h(n-2)-ra(n)x(n-1)+r ²x(n-2) (8)

Wherein a (n) is the trap parameter that needs adjustment, and it finally converges to-2cos ω ₀, be positioned at frequencies omega to fall into to remove ₀Modulated subcarrier technique, r is the polar radius of trapper, should be slightly less than 1, gets 0.99995 in the present embodiment.

For the update algorithm of a (n), shilling

Be that formula (8) is asked local derviation to a (n):

g(n)＝x(n-1)-rx′(n-1)-ra(n)g(n-1)+r ²g(n-2) (9)

Use the LMS algorithm, get the more new formula of a (n):

a(n+1)＝a(n)-2μx(n)g(n) (10)

In the formula (10), 0≤μ≤1 is a step-length, and a (0) is the carrier estimation value.

By above derivation, present embodiment adopts the adaptive notch algorithm steps as follows:

(1) initialization: g (0)=g (1)=0, x ' (0)=x ' (1)=0, r=0.99995, μ=0.0001, a (0) is obtained by the output valve of carrier frequency estimation unit, promptly-2cos (2 π f _Kmax);

(2) calculating formula (8) and formula (9), the error signal x ' that obtains removing carrier wave is (n);

(3) repeating step 2.

In the 8th step, the signal that is interfered is sent into the self-adaption constant mould disturb the inhibition module to carry out the extraction of interference signal, and the permanent mould interference signal of having extracted is carried out adaptive cancellation.

Comprise the steps: to judge the back if the earth-space communication signal is interfered, then signal behind the trap of trapper group output is sent into constant mode array as shown in Figure 7, carry out permanent mould and disturb blind extraction through surveillance; As desired signal, one tunnel complex signal of monitor module output is sent into as shown in Figure 8 adaptive interference canceller as input signal, carries out adaptive interference cancellation with the permanent mould interference signal extracted.

Signal is through front-end processing, and the discrete signal that arrives constant mode array is designated as x ' (n), through weight vector w (n) weighted sum of adaptive updates, obtains permanent mould interference and is output as:

Y _cma(n)＝w ^H(n)x′(n) (11)

In the formula x ' (n)=[x ' ₁(n), x ' ₂(n)] ^TBe the two-way complex signal of trapper output, w (n)=[W ₁(n), W ₂(n)] ^TBe adaptive weight vector, adopt constant modulus algorithm that weight vector is upgraded.Adopt 1-2 type steepest descent constant modulus algorithm in the present embodiment, weight vector more new formula is:

w(n+1)＝w(n)+μx′(n)e ^* _cma(n) (12)

In the formula

μ is a step factor, generally gets a smaller number, elects 0.002 in the present embodiment as.

The adaptive cancellation device adopts the constant mode array output y of formula (11) gained _Cma(n), obtain the required useful signal of civil aviation air-ground communication, be designated as thereby be subjected to interference signal to carry out permanent mould interference cancellation in conjunction with a road of monitor module output as the reference input:

e(n)＝x _h1′(n)-u ^*(n)y _cma(n) (13)

U in the formula (n) is the self adaptation weight coefficient of canceller, adopts plural recursive least-squares (CRLS) algorithm to finish right value update.

The cost function of CRLS is:

$J\left(u\right)=\underset{k=0}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&lambda;}}^{n-k}{|{{\mathrm{<figure-callout\; id="1"\; label="x\; h"\; filenames="S2008100520852E00031.png"\; state="\{\{state\}\}">x</figure-callout>}}_h}^{\&prime;}\left(k\right)-u\left(k\right)y_{\mathrm{cma}}\left(k\right)|}^2---\left(14\right)$

In the formula: 0＜λ＜1 is called forgetting factor, is taken as 0.9999 in the present embodiment.

At this,, traditional CRLS is improved to simplify computing at the characteristics of constant modulus signals.Be specially and earlier constant modulus signals made normalized:

$\frac{y_{\mathrm{cma}}\left(n\right)}{\left|y_{\mathrm{cma}}\left(n\right)\right|}=e^{-\mathrm{j\&beta;}\left(n\right)}---\left(15\right)$

β in the formula (l) represents the complex phase position of constant modulus signals.The right value update that obtains the adaptive cancellation device is:

$u\left(n\right)=\frac{\mathrm{\&lambda;r}(n-1)+{{\mathrm{<figure-callout\; id="1"\; label="x\; h"\; filenames="S2008100520852E00031.png"\; state="\{\{state\}\}">x</figure-callout>}}_h}^{\&prime;}\left(n\right)e^{\mathrm{j\&beta;}\left(n\right)}}{1+\mathrm{\&lambda;R}(n-1)}---\left(16\right)$

R in the formula (n)=λ R (n-1)+e ^{-j β (n)}e ^{J β (n)}=λ R (n-1)+1; R (n)=λ r (n-1)+x _H1' (n) e ^{J β (n)}

The 9th step, to step 5 or step 8 both one of the state no interference signal exported carry out demodulation, again through low pass filter filters out high frequency clutter, carry out the D/A conversion at last and export audio signal clearly.

Disturb digital medium-frequency signal that suppresses module output or the digital medium-frequency signal of directly exporting from monitor module to carry out demodulation to the self-adaption constant mould, adopt envelope-demodulation method, and utilize D/A (D/A) converting unit to carry out digital-to-analogue conversion, with regard to exportable audio signal clearly.

Fig. 9 has provided when not adding trap constant mode array output signal determined property statistical chart as a result under the mixing situation of different AM useful signals and FM interfering signal power ratio.When FM power is big, can converge to constant modulus signals accurately as can be seen, but increase along with the AM signal power, constant mode array converges to the probability of non-permanent mould AM signal also along with increase, thereby the error capture phenomenon occurred, causes the instability of Interference Suppression System.With the similarity condition of experiment shown in Figure 9 under, the elimination error capture phenomenon that the method that constant modulus signals extracts behind the first trap of the present invention can 100%.

In the present embodiment AM useful signal disturbed when identical with FM interference signal transmitting power and suppress experiment, w=[-0.6+0.7j in the experiment ,-0.4+0.5j] ^T, μ=0.002, Figure 10 a is former voice signal oscillogram, Figure 10 b is the voice signal oscillogram of the direct demodulation of mixed signal, and Figure 10 c is the voice signal oscillogram of demodulation after adaptive disturbance suppresses.The method applied in the present invention has suppressed the permanent mould interference signal in the earth-space communication effectively as can be seen, has improved voice call quality.

As shown in Figure 1, a kind of new civil aviation ground and air communication twin channel constant module Interference Suppression System of the present invention includes the two antenna array 1,2 of received signal; Two antenna array 1,2 signals that received are carried out signal processing and continuous successively radio frequency processing group 3, mould/number conversion group 4 and Digital Down Convert group 5; The orthogonal transform group 6 that links to each other and the digital signal of its output is carried out orthogonal transform with Digital Down Convert group 5; The monitor module 7 that links to each other with the orthogonal transform group and its output signal is differentiated; The interference signal that has to monitor module 7 outputs is carried out the carrier frequency estimation group 8 that carrier frequency is estimated; Signal is carried out the trapper group 9 of trap; The interference signal that has to 9 outputs of trapper group disturbs the self-adaption constant mould of inhibition to disturb inhibition module 10; The demodulator 11 that the interference suppression signal that the state no interference signal and the self-adaption constant mould interference inhibition module 10 of monitor module 7 outputs are exported carries out demodulation; D/A 12 that links to each other with the output of demodulator 11 and the audio frequency that links to each other with D/A 12 output 13.

Above-mentioned two antenna array 1,2, radio frequency processing group 3, mould/number conversion group 4, Digital Down Convert group 5 are made up of antenna, RF processing unit, A/D converter, the Digital Down Convert unit of two-way parameter unanimity respectively.

Above-mentioned orthogonal transform group, carrier frequency estimation group, trapper group are made up of orthogonal transform unit, carrier frequency estimation unit, the trapper of two-way parameter unanimity respectively.

As shown in Figure 2, wherein said radio frequency processing group 3 includes two groups and links to each other successively: LNA (low noise amplifier) 14, BPF (bandpass filtering) amplifying circuit 15, one-level mixting circuit 16, BPF amplifying circuit 17, secondary mixting circuit 18, BPF amplifying circuit 19, voltage-controlled attenuator 20, intermediate level circuit 21, three grades of mixting circuits 22, BPF amplifying circuit 23, the output of intermediate level circuit 21 also connects detecting circuit 25, detecting circuit 25 and also links to each other with voltage-controlled attenuator 20 by comparator 24, and three grades of mixting circuits 22 also connect three local oscillation circuits 26; Wherein between two groups: three grades of mixting circuits 22 link to each other by three local oscillation circuits 26, and one-level mixting circuit 16 links to each other by first frequency synthesizer 27, and secondary mixting circuit 18 links to each other by second frequency synthesizer 29; LNA in two groups (low noise amplifier) 14 connects antenna 1 and antenna 2 respectively, and first frequency synthesizer 27 also is connected crystal oscillating circuit 28 respectively with second frequency synthesizer 29.

Claims (10)

1. a new civil aviation ground and air communication twin channel constant module interference suppressing method is characterized in that, includes following steps:

(1) the two-way very high frequency(VHF) signal that two antenna array is received is separately converted to intermediate-freuqncy signal;

(2) the two-way intermediate-freuqncy signal that down-conversion is obtained is carried out analog-to-digital conversion respectively;

(3) the two-way digital intermediate frequency signal after the analog-to-digital conversion is carried out filtering extraction respectively;

(4) signal behind the filtering extraction is carried out orthogonal transform, real signal is become complex signal;

(5) the two-way complex signal after the orthogonal transform is sent into monitor module, judge whether signal is interfered, if the noiseless step (9) that changes over to changes step (6) over to if having to disturb;

(6) on the known basis of amplitude-modulated signal carrier frequency frequency range, the signal after the orthogonal transform is carried out carrier frequency estimate;

(7) with the carrier frequency frequency estimation as the reference signal, carry out trap, the carrier wave in the amplitude-modulated signal is fallen into;

(8) signal that will remove modulated subcarrier technique is sent into the self-adaption constant mould and is disturbed and suppress module and carry out the extraction of permanent mould interference signal, and the interference signal of having extracted is carried out adaptive cancellation;

(9) to step (5) or step (8) both one of the state no interference signal exported carry out demodulation, again through low pass filter filters out high frequency clutter, carry out digital-to-analogue conversion at last and export audio signal clearly.

2. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1, it is characterized in that (1) step was converted into intermediate-freuqncy signal with the very high frequency(VHF) signal and finishes by low noise high-frequency amplifier, three grades of frequency mixers and automatic gain control circuit.

3. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1, it is characterized in that (4) described orthogonal transform of step is in complex field the linear convolution mixed model to be converted to be convenient to the linear instantaneous mixed model that constant modulus signals extracts.

4. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1, it is characterized in that, (5) step was sent the complex signal after the orthogonal transform into monitor module and judges and utilize the coefficient correlation of two paths of signals to judge, comprised the steps: to calculate the coefficient correlation ρ of two paths of data; Judge whether greater than threshold value th; Show that greater than threshold value th usefully empty signal of communication is not interfered, get wherein one road signal and send into demodulator; Otherwise be subjected to interference signal to send into carrier frequency estimation group and trapper group two-way.

5. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1 is characterized in that, (6) step is described carries out carrier frequency to the signal after the orthogonal transform and estimate, is to utilize the Ge Ceer algorithm to carry out carrier frequency to estimate.

6. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1, it is characterized in that, (7) step fell into the carrier wave in the signal and is based on constant mode array and captures kurtosis sometimes and carry out less than this phenomenon of non-constant modulus signals of 2, and the signal kurtosis avoids constant mode array the error capture phenomenon to occur greater than 2 thereby carrier wave falls into the back.

7. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1 is characterized in that, the extraction of described interference signal of (8) step is the blind extraction that the permanent envelope trait that utilizes common interference to have is carried out permanent mould interference signal; And utilize the adaptive cancellation technology that the permanent mould interference signal of having extracted is offseted, as desired signal, the one tunnel is subjected to interference signal as input signal after orthogonal transform with the constant modulus signals of constant mode array output.

8. a kind of new civil aviation ground and air communication twin channel constant module interference suppressing method according to claim 1, it is characterized in that, it is to adopt envelope-demodulation method that (9) step was carried out demodulation to state no interference signal, after the signal demodulation again through low pass filter filters out high frequency clutter.

9. a new civil aviation ground and air communication twin channel constant module Interference Suppression System is characterized in that, includes the two antenna array (1,2) of received signal; Radio frequency processing group (3), mould/number conversion group (4) and Digital Down Convert group (5) that the signal that two antenna array (1,2) is received carries out signal processing and links to each other successively; The orthogonal transform group (6) that links to each other and the digital signal of its output is carried out orthogonal transform with Digital Down Convert group (5); The monitor module (7) that orthogonal transform group (6) output signal is judged; The interference signal that has to monitor module (7) output is carried out the carrier frequency estimation group (8) that carrier frequency is estimated; As the reference signal, signal is carried out the trapper group (9) of carrier suppressed with the carrier frequency frequency estimation; The interference signal that has to trapper group (9) output disturbs the self-adaption constant mould of inhibition to disturb inhibition module (10); The demodulator (11) that the interference suppression signal that the state no interference signal and the self-adaption constant mould interference inhibition module (10) of monitor module (7) output are exported carries out demodulation; D/A (12) that links to each other with the output of demodulator (11) and the audio frequency that links to each other with D/A (12) output (13); Wherein, described two antenna array (1,2) by the antenna of two-way parameter unanimity form, radio frequency processing group (3) is made up of RF processing unit, mould/number conversion group (4) is made up of A/D converter, and Digital Down Convert group (5) is made up of the Digital Down Convert unit; Described orthogonal transform group (6) is made up of the orthogonal transform unit of two-way parameter unanimity, carrier frequency estimation group (8) by the carrier frequency estimation unit form, trapper group (9) is made up of trapper.

10. a kind of new civil aviation ground and air communication twin channel constant module Interference Suppression System according to claim 9, it is characterized in that, described radio frequency processing group (3) includes two groups and links to each other successively: low noise amplifier (14), the first bandpass filtering amplifying circuit (15), one-level mixting circuit (16), the second bandpass filtering amplifying circuit (17), secondary mixting circuit (18), the 3rd bandpass filtering amplifying circuit (19), voltage-controlled attenuator (20), intermediate level circuit (21), three grades of mixting circuits (22), four-tape pass filter amplifying circuit (23), the output of intermediate level circuit (21) also connects detecting circuit (25), detecting circuit (25) also links to each other with voltage-controlled attenuator (20) by comparator (24), and three grades of mixting circuits (22) also connect three local oscillation circuits (26); Wherein: the three grades of mixting circuits (22) between two groups link to each other by three local oscillation circuits (26), one-level mixting circuit (16) between two groups links to each other by first frequency synthesizer (27), and the secondary mixting circuit (18) between two groups links to each other by second frequency synthesizer (29); Low noise amplifier in two groups (14) connects first antenna (1) and second antenna (2) respectively, and first frequency synthesizer (27) also is connected crystal oscillating circuit (28) respectively with second frequency synthesizer (29).

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