CN105425218A - Radar-communication integrated realizing method - Google Patents

Abstract

The invention provides a radar-communication integrated realizing method. According to the radar-communication integrated realizing method, based on analysis on the characteristics of the ambiguity function of transmitted signals of a communication system, communication signals are directly transmitted when the number of transmitted code elements in one transmission period satisfies requirement; the communication code elements pass through a pulse type shaping filter; obtained signals are transmitted out through using a transmitter and by means of an antenna; a receiving end carries out radar detection processing on the signals directly using the communication signals; the receiving end carries out demodulation on the signals through a receiver, so that baseband signals can be obtained; the baseband signals pass through a matched filter, so that an output signal to noise ratio is maximum; if a function which is to be realized by the system is a communication function, sampling judgment is performed on the demodulated baseband signals, so that the communication function can be realized through communication code element information; and if a function which is to be realized by the system is a radar function, a certain code element accumulation is performed on the signals, so that high radar resolution can be obtained, and time delay and Doppler frequency are extracted through using related technologies, and a radar detection function can be finally realized.

Description

A kind of radar-communicating integral implementation method

Technical field

The invention belongs to electronic communication.

Background technology

From the history of electronics development, military requirement and technical progress promote the development of electronics jointly.Along with infotech is in the extensive utilization of military field, a new round based on infotech, with obtaining information advantage be core, military change based on advanced technology weapon starts, future war turns to the land, sea, air of feature, the incorporated combat in sky with information, and therefore electronics are also to the trend development of integration.

For a long time, field of radar and the communications field are strictly distinguished due to the difference by respective research object, and result causes current research major part radar system and communication system to be separated and studies.In fact, radar with communicate as acquisition of information, process, transmission and the typical way exchanged, although have obvious difference on hardware device and software architecture, but from their principle of work, system architecture, the aspects such as working frequency range, both have again a lot of similarity, so implement integrated design to radar with communicating, not only condition possesses, and hardware resource sharing is also feasible, radar system and communication system are organically combined and resource sharing, be not only the main development direction of the comprehensive integrated system of future war platform clectronic, and radar is realized multifunctional all design with communicating, greatly can improve the fight capability of system, and it is slow to overcome traditional information transmission speed, the deficiency of the aspects such as confidentiality difference and rate of false alarm height.

The research realized for communication and radar detection framework for intergration at present mainly contains following three kinds of modes:

1. timesharing system: radar system and communication system share radar antenna, the two time-sharing work.This radar advantage does not need the new radar signal waveform of research and communication signal waveforms, technology maturation, realizes simple; Shortcoming underaction, may cause radar detection " blind area ".

2. point wave beam system: the front of phased-array radar is divided into different regions, is respectively used to radar detection, communication and recognition function.The advantage of wave beam system is divided to be the function that simultaneously can realize communication and radar.But front large for phased array is divided into zones of different, and when gross energy is certain, also there is radar in radar detection power reduction, the problem that communication is disturbed mutually.

3. simultaneously system: radar detection signal is carried out modulation generation integration signal as carrier wave as baseband signal by signal of communication.Carry out radar detection in communication, can carry out radar detection while that simultaneously the advantage of system being communication, radar all can use all system capacities with communicating simultaneously, and shortcoming is that the direction communicated by radar beam limits, and affects dirigibility.

Summary of the invention

Technical matters to be solved by this invention is, based on while system propose a kind of by radar beam direction restriction new radar-communicating integral implementation method.

The present invention is that a kind of radar-communicating integral implementation method, comprises the following steps for solving the problems of the technologies described above adopted technical scheme:

Radar-communicating integral signal generation step: launch in the cycle for one and process N number of communication code element input pulse formed filter, Pulse shaped filter is for eliminating the intersymbol interference of communication code element, the communication code element input transmitter again Pulse shaped filter exported, the filtered communication code element of transmitter to input is transmitted after modulating, and will be transmitted by emitting antenna and be transmitted into wireless channel; In the transmitting cycle, the communication code element number N of process need meet: the ambiguity function figure of the waveform that transmits only has single spike;

Realize the receiving step of communication: demodulation is carried out to the signal of receiving antenna output and obtains baseband signal, then by baseband signal Input matching wave filter, sampling judgement is carried out to the baseband signal after matched filtering and obtains the code element that communicates;

Realize the receiving step of radar detection: demodulation is carried out to the signal of receiving antenna output and obtains baseband signal, then by baseband signal Input matching wave filter, coherent accumulation is carried out to the baseband signal after matched filtering and exports radar detected module to.

The present invention is different from and existingly generates radar-communication integration signal by signal of communication and radar detection signal are carried out modulation, by the characteristic of its ambiguity function transmitted of analyzing communication system, when the he number launched within a transmitting cycle meets the demands, direct transmitting signal of communication, communication code element passes through Pulse shaped filter, then to utilizing transmitter to be launched by signal by antenna; Receiving end directly utilizes signal of communication to carry out radar detection process: receiving end carries out demodulation by receiver, obtain baseband signal, baseband signal makes output signal-to-noise ratio maximum by matched filter, if what system realized is communication function, then sampling judgement is carried out to the baseband signal of demodulation, thus show that communications codes metamessage is to realize communication function.If system realization is radar function, needs to carry out certain code element accumulation to signal, there is good radar resolution like this, carry out parameter extraction by correlation technique and go out time delay and Doppler's frequency, finally reach the function of radar detection.

The invention has the beneficial effects as follows, radar and communications shares a kind of signal, does not affect again function each other simultaneously, has reached and realized radar-communicating integral, relative to the integrated implementation method of system while of existing, the present invention does not limit by radar beam direction.

Accompanying drawing explanation

Fig. 1 radar-communication integration protocol procedures figure

Fig. 2 raised cosine filter time-domain diagram

Fig. 3 adds the time-domain diagram of 21 code element information

Fig. 4 adds the ambiguity function of 21 symbol signals

Fig. 5 adds the time-domain diagram of 41 code element information

Fig. 6 adds the ambiguity function of 41 code element letter signals

The ambiguity function of Fig. 7 signal

Embodiment

As shown in Figure 1, the present invention mainly comprises three parts: signal produces, communication check and detections of radar.

Concrete implementation step is as follows:

Step 1: communication code element { a _nbe the incoming symbol sequence of pulse-shaping, in scale-of-two situation, its value is a _n=0,1 or a _n=-1 ,+1.Therefore the baseband signal d (t) that sequence pair is answered is expressed as:

$d\left(t\right)=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{a}_n\mathrm{\δ}\left(t-{\mathrm{nT}}_s\right)$

Wherein, T _sfor symbol period, δ (t) is impulse string, and t is time variable, and n represents the n-th code element.After communication code element produces, namely it is produced baseband signal by Pulse shaped filter, here by G _tw () is set to the transition function of Pulse shaped filter.

Step 2: after modulated signal being launched after the baseband signal of above-mentioned generation being modulated by transmitter, is utilized receiver carry out receiving and carry out demodulation to it, can introduce noise n in transmitting procedure _r(t).Here represent the transport property of channel with C (w), channel is generally bandwidth efficient channel, then carries out matched filtering, here by G to obtaining baseband signal after demodulation _rw transport property that () is matched filter, utilize matched filter to ensure output maximum signal to noise ratio, therefore the overall transfer characteristic H (w) of baseband transmission system is:

H(w)＝G _T(w)C(w)G _R(w)

The unit impulse response of its correspondence is

$h\left(t\right)=\frac{1}{2\mathrm{\π}}{\∫}_{-\mathrm{\∞}}^{+\mathrm{\∞}}H\left(w\right)e^{jwt}dw$

H (t) is under single impulse δ (t) effect, the output waveform that H (w) is formed, therefore under impulse sequence d (t) effect, w is angular frequency, and matched filter output signal r (t) can be expressed as:

$r\left(t\right)=d\left(t\right)*h\left(t\right)=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{a}_n\mathrm{\δ}(t-{\mathrm{nT}}_s)*h\left(t\right)+n_R\left(t\right)=\underset{n=-\mathrm{\∞}}{\overset{\mathrm{\∞}}{\Σ}}{a}_{n}h(t-{\mathrm{nT}}_s)+n_R\left(t\right)$

Step 3: communication module signal transacting.

R (t) is the Received signal strength after matched filtering, carries out the extraction of signal of communication code element, therefore samples to r (t), and sampling instant is t=kT _s+ t ₀, t ₀for signal is delayed the time by channel and receiving filter, k represents a kth sampled point.

Signal after sampling is expressed as:

$\begin{array}{c}r\left({\mathrm{kT}}_s+t_0\right)=\underset{n}{\mathrm{\Σ}}{a}_{n}h\left({\mathrm{kT}}_s+t_0-{\mathrm{nT}}_s\right)+n_R\left({\mathrm{kT}}_s+t_0\right)\\ =a_{k}h\left(t_0\right)+\underset{n\≠k}{\mathrm{\Σ}}{a}_{n}h\left(\left(k-n\right)T_s+t_0\right)+n_R\left({\mathrm{kT}}_s+t_0\right)\end{array}$

Wherein for intersymbol interference, n _r(kT _s+ t ₀) be noise random disturbance, a _kh (t ₀) for transmitting code element information.

But, for communication system, communication system is optimized general from following three angles: 1. system transfers is the most effective, and 2. system transfers is the most reliable, and 3. system transfers is the safest.

Therefore when designing communication system, in order to ensure the reliability transmitted, the intersymbol interference in necessary erasure signal transmitting procedure.

In above-mentioned design, eliminate intersymbol interference and then must meet:

$\underset{n\≠k}{\Σ}{a}_{n}h\left(\right(k-n)T_s+t_0)=0$

From Nyquist criteria, its demand fulfillment:

$\begin{array}{cc}\underset{i}{\Σ}H(w+\frac{2i\mathrm{\π}}{T_s})=T_s& \left|w\right|\≤\frac{\mathrm{\π}}{T_s}\end{array}$

Corresponding time domain satisfy condition into:

$h\left({k\mathrm{}T}_s\right)=\left\{\begin{array}{cc}1& k=0\\ 0& k\≠0\end{array}\right.$

Have a specific frequency spectrum can meet the condition transmitted without intersymbol interference, it is exactly the raised cosine spectrum of widespread use.

The transport function of this raised cosine filter is expressed as:

$H\left(f\right)=G_T\left(w\right)G_R\left(w\right)=\left\{\begin{array}{cc}T& \left|f\right|\≤\frac{1-r}{2T}\\ \frac{T}{2}\{1+cos\[\frac{\mathrm{\π}T}{r}*\left(\right|f|-\frac{1-r}{2T})\]\}& \frac{1-r}{2T}\≤\left|f\right|\≤\frac{1+r}{2T}\\ 0& \left|f\right|\≥\frac{1+r}{2T}\end{array}\right.$

Wherein, r is rolloff-factor (being ideal low-pass filter during r=0), the T incoming symbol cycle,

Time domain impulse response is:

$h\left(t\right)=\frac{sin(\mathrm{\π}t/T)}{\mathrm{\π}t/T}*\frac{cos(\mathrm{\π}rt/T)}{1-{\left(\frac{2rt}{T}\right)}^2}$

It is to be noted, the strict limit characteristic frequently of raised cosine filter, that physics is not attainable, but due to the flatness of 0 < r≤1 raised cosine filter frequency characteristic, make likely to realize this frequency characteristic with physically realizable filter is approximate, so extensively adopt the raised cosine filter of 0 < r≤1 in the limit of reality is with digital traffic system.The time-domain diagram of raised cosine filter as shown in Figure 2.

When after elimination intersymbol interference, then disturb only remaining noise, just greatly reduce the bit error rate.Therefore as r (kT _s+ t ₀) when being added to decision circuit, when binary digit communicates, a _kpossible value be 0 or 1, if the decision threshold of decision circuit is V _d, then such decision rule is:

As r (kT _s+ t ₀) > V _dtime, sentence a _kbe 1; As r (kT _s+ t ₀) < V _dtime, sentence a _kbe 0.

Final then can accurately extract the code element information transmitted in signal of communication.

Step 4: radar signal detection.

Radar signal design selects appropriate signals according to the targeted environment condition that operational requirements is given, and setting radar signal type and correlation parameter, to meet the every tactical qualities of radar, realize radar various functions.Generalized case, radar signal waveform should meet following requirement simultaneously:

L () has enough energy, to ensure to find target and Measurement accuracy target component;

(2) there is the wide and bandwidth of a timing, with satisfied range finding, rate accuracy;

(3) there is enough target discriminations;

(4) for unwanted clutter, good rejection ability is had;

(5) there is low intercepting and capturing characteristic, improve anti-reconnaissance capability, thus improve antielectron antagonism.

In radar, normally used filter for receiver is called matched filter.This wave filter signal to noise ratio (S/N ratio) when noise is white Gauss noise (such as the receiver noise) of additivity is maximum, thus provides maximum target detection capabilities.General employing ambiguity function describes radar signal.Ambiguity function describes the characteristic such as resolution characteristic, measuring accuracy of radar signal.Generally, if do not have theoretical restriction, desirable ambiguity function will be that the single spike that unlimited thin and other places are zero forms by initial point place, be exactly an impulse function, not have Distance geometry Doppler frequency (radial velocity) fuzzy.Time delay and/or frequency can be determined initial point unlimited thin (or very little) simultaneously and reach precision high arbitrarily, it also can differentiate the very near extraterrestrial target of two distances, and suppresses all clutters except initial point is sentenced.Do not have fuzzy corresponding yet.But, this fuzzy graph of wishing very much is unallowed in theory, also can not obtain.Needing when designing radar signal to get compromise between the two in resolution and measuring accuracy, reaching best effects.

Therefore in order to realize radar-communication integration, we analyze the ambiguity function of above-mentioned signal of communication thus determine whether it meets the semaphore request of radar detection, if its ambiguity function meets the demands, can carry out parameter extraction (i.e. time delay and Doppler) with the radar detection method of routine.General time-frequency two-dimensional correlation extracts correlation parameter.

The mathematical definition expression formula of general ambiguity function is:

$\mathrm{\&chi;}(\mathrm{\&tau;},f_d)={\&Integral;}_{-\mathrm{\&infin;}}^{\mathrm{\&infin;}}u\left(t\right)u^{*}(t-\mathrm{\&tau;})e^{j2{\mathrm{\&pi;f}}_{d}t}dt$

Wherein: u (t) is transmitted waveform, τ is time delay, f _dfor Doppler's frequency, * represents conjugation;

Generally ambiguity function is described and also has two kinds of forms below:

ψ(τ,f _d)＝χ(τ,f _d)χ ^*(τ,f _d)

Wherein, $\mathrm{\&chi;}(\mathrm{\&tau;},f_d)={\&Integral;}_{-\mathrm{\&infin;}}^{\mathrm{\&infin;}}u(f-f_d)u^{*}\left(f\right)e^{-j2\mathrm{\&pi;}f\mathrm{\&tau;}}df$

In the following embodiments by the ambiguity function of the above-mentioned transmitting signal of communication of concrete analysis, thus analysis judges whether it can it can be used as radar signal to carry out the detection of a target.

In embodiment, by the random code element of analysis and utilization as signal of communication, then analyze the ambiguity function transmitted, thus prove the feasibility of the program.This emulation platform operating system is WIN7, adopts MATLAB to compile.The scheme of the radar-communication integration of the program is verified by the figure of its ambiguity function of observation and analysis.

Simulation related parameter will be provided below.

Signal	Code element { a n}	Number of symbols	Mark space	Sampling interval	Rolloff-factor r
						Parameter	+ 1 and-1	21	1(s)	0.001(s)	0

After emulation, add the time-domain diagram of symbol signal as shown in Figure 3, as shown in Figure 4, having two spikes can not be used as radar detection for the ambiguity function figure of its correspondence.

Adjustment correlation parameter:

Signal	Code element { a n}	Number of symbols	Mark space	Sampling interval	Rolloff-factor r
						Parameter	+ 1 and-1	41	1(s)	0.001(s)	0

After emulation, add the time-domain diagram of symbol signal as shown in Figure 5, the ambiguity function figure of its correspondence as shown in Figure 6, has single spike, can be used for radar detection.

Find through emulation experiment, when he number is greater than 31, the ambiguity function figure of its correspondence has single spike, can be used for radar detection.

Analysis of conclusion: can be drawn by above-mentioned emulation, radar-communicating integral signal that we propose meets the condition of communication system without intersymbol interference, and simultaneously along with the increase of code element number, the resolving effect of its ambiguity function is better, then its radar detection better effects if.

Signal	Code element { a n}	Number of symbols	Mark space	Sampling interval	Rolloff-factor r
						Parameter	+ 1 and-1	41	0.0001(s)	10e-6(s)	0

After emulation, the ambiguity function of its correspondence as shown in Figure 7.

Analysis of conclusion: from emulation, reduces ambiguity function corresponding to symbol interval and stretches on Doppler frequently direction, but can not affect the detection performance of radar.

Claims (3)

1. radar-communicating integral implementation method, is characterized in that, comprise the following steps:

Radar-communicating integral signal generation step: launch in the cycle for one and process N number of communication code element input pulse formed filter, Pulse shaped filter is for eliminating the intersymbol interference of communication code element, the communication code element input transmitter again Pulse shaped filter exported, the filtered communication code element of transmitter to input is transmitted after modulating, and will be transmitted by emitting antenna and be transmitted into wireless channel; In the transmitting cycle, the communication code element number N of process need meet: the ambiguity function figure of the waveform that transmits only has single spike;

Realize the receiving step of communication: demodulation is carried out to the signal of receiving antenna output and obtains baseband signal, then by baseband signal Input matching wave filter, sampling judgement is carried out to the baseband signal after matched filtering and obtains the code element that communicates;

Realize the receiving step of radar detection: demodulation is carried out to the signal of receiving antenna output and obtains baseband signal, then by baseband signal Input matching wave filter, coherent accumulation is carried out to the baseband signal after matched filtering and exports radar detected module to.

2. a kind of radar-communicating integral implementation method as claimed in claim 1, is characterized in that, the transition function G of Pulse shaped filter _tthe transition function G of (w) and matched filter _rw () meets:

$G_T\left(W\right)G_R\left(W\right)=\left\{\begin{array}{cc}T& \left|f\right|\&le;\frac{1-r}{2T}\\ \frac{T}{2}\{1+cos\&lsqb;\frac{\mathrm{\&pi;}T}{r}*\left(\right|f|-\frac{1-r}{2T})\&rsqb;\}& \frac{1-r}{2T}\&le;\left|f\right|\&le;\frac{1+r}{2T}\\ 0& \left|f\right|\&GreaterEqual;\frac{1+r}{2T}\end{array}\right.$

Wherein, r is rolloff-factor, 0 < r≤1, and T is the incoming symbol cycle, | f| is frequency.

3. a kind of radar-communicating integral implementation method as claimed in claim 1, is characterized in that, in the transmitting cycle, the communication code element number N of process is more than or equal to 31.