CN101552761A - SAW-based code domain reference Chirp ultra-wideband system modulation and demodulation method - Google Patents

Abstract

The invention relates to a modulation and demodulation method of a code domain reference Chirp ultra-wideband system based on SAW, which effectively solves the problems of serious multipath interference, difficult miniaturization, poor coexistence and low transmission efficiency of the ultra-wideband system, and is characterized in that a linear frequency modulation analog signal to be modulated, an information bit and an orthogonal code waveform are generated, a linear frequency modulation signal modulated by information and an orthogonal code and an original unmodulated linear frequency modulation signal are added and transmitted, a received signal is subjected to pulse compression and squaring, multiplied by a local orthogonal code, integral processing is carried out on the multiplied operation result, signal energy is accumulated in an integral period, and the integral processing result is judged to obtain the information bit; compared with a frequency domain transmission reference system, the frequency domain transmission reference system has the advantages of excellent performance, simplified structure, no deterioration of the performance along with the increase of multipath time delay or transmission rate, and improved transmission rate or transmission distance.

Description

Sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW

One, technical field

The present invention relates to communication field, particularly a kind of sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW.

Two, background technology

Ultra broadband (UWB, Ultra Wide Band) technology is as a kind of unconventional, novel Radio Transmission Technology, adopt usually ultra-narrow pulse (pulsewidth nanosecond to hundreds of picosecond magnitudes) or extremely wide frequency spectrum (relative bandwidth greater than 20% or absolute bandwidth greater than 500MHz) come transmission information.The sixties in 20th century, the super wideband wireless transmission technology of Modern Significance appears in the research in tactical communication of U.S. army field.2002, along with FCC (FCC, Federal CommunicationsCommission) determines UWB radiation template, indicate that US military formally lifts a ban it, allow the UWB commercial signal communication system to come into operation.

Existing super-broadband tech system can be divided into pulse modulation and carrier modulation two big classes from the angle of signal modulation, and wherein pulse modulation mode is called as IR-UWB, and the carrier modulation mode then comprises MB-OFDM, DS-CDMA, Chirp-UWB etc.; From the angle of input can be divided into transmission with reference to mode and non-transmission with reference to mode two big classes, the essence that wherein sends with reference to mode is from coherent detection, non-transmission then comprises relevant and incoherent detection with reference to mode.

Because the restriction of high-speed AD converter spare (ADC), often directly adopt the method for analog to realize based on the UWB receiver of pulse system.But adopt the IR-UWB receiver of simulation coherence detection high to regularly requiring, the structure relative complex, and need complicated channel estimating; Can avoid simulating the difficulty that is faced of coherent detection, its poor-performing to a certain extent though adopt simulation incoherent detection method.Therefore, external correlative study unit has proposed based on sending with reference to (TR, IR-UWB technical system Transmitted-Reference) from the thinking from coherent detection.

2002, the Ralph Hoctor of the U.S. and Harold Tomlinson proposed standard and have sent reference pulse ultra broadband system (TR-UWB, Transmitted-Reference Ultra-Wideband), and the essence of this system is that time domain sends with reference to system ^[1]Simultaneously, this research group has provided the practicability scheme based on the transmission reference type impulse radio ultra wide band system (DHTR, Delay-HoppedTransmitted-Reference Ultra-Wideband) of jumping time-delay ^[2]This time domain sends reference pulse super-broadband tech system to be had and regularly requires lower, simple in structure and do not need advantage such as channel estimating, but owing to adopted the simulation time delay device, therefore exists the difficulty of integrated and further miniaturization.Subsequently, the foreign study personnel have proposed a series of improved structures at time domain transmission reference technique system in succession, and the lifting of its performance often is based upon on the basis of adopting more simulation time delay device, makes that this problem is more outstanding.

2006, at the deficiency of time domain transmission with reference to system, the Dennis Goeckel of the U.S. and Qu Zhang have proposed the transmission reference pulse ultra broadband (FSR-UWB based on frequency deviation, Slightly Frequency-Shifted ReferenceUltra-Wideband) system, the essence of this system are that frequency domain sends with reference to system ^[10-13]Simultaneously, this research group has provided the physics realization scheme, and this scheme does not need to adopt the simulation time delay device, thereby helps integrated design.But because its performance and multipath expansion time delay is relevant, thus along with the raising of transmission range or transmission rate, its performance rapid deterioration, so its transmission rate can't further promote.

Existing super wideband wireless transmission technology mainly towards closely, the application of two-forty, but, need further to improve the distance of super wideband wireless transmission in many applications.And existing super-broadband tech system is primarily aimed at closely application proposition, and therefore directly applying to the medium and long distance field of wireless transmission will be faced with many difficulties.Specifically, along with the expansion of communication distance, the super wideband wireless transmission will mainly face following outstanding difficulty: multipath disturbs more serious; More outstanding between the performance index requirement of system and low-power consumption, the miniaturization Design; With the compossibility problem of other system will be more outstanding; The interference of other signal will be more serious in the band; The problem that existing radio ultra wide band system emission effciency is low is more outstanding; Existing device level becomes the main bottleneck of restriction super-broadband tech practicability level, and along with the further raising of communication distance, this problem will be more outstanding.

Three, summary of the invention

At above-mentioned situation, for overcoming the defective of prior art, the present invention's purpose just provides a kind of sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW, can effectively solve the multipath serious interference, the miniaturization difficulty, poor with the compossibility of other system, and the low problem of radio ultra wide band system emission effciency, said conciliation comprises modulation and demodulation (be called for short and reconcile), therefore, the title of this invention also can be written as the sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW (Surface Acoustic Wave) device, the technical scheme of its solution is, send in the sign indicating number territory on the basis of reference pulse ultra broadband (COTR-UWB) system configuration, send with reference to ultra broadband structure (Chirp-COTR-UWB) in conjunction with the sign indicating number territory by a kind of Chirp, narrow pulse signal is replaced with the Chirp signal, and (typical representative is linear frequency modulation or nonlinear frequency modulation signal, and guarantee that FM signal satisfies the FCC definition), receiving terminal adopts time domain compression or frequency domain compress technique to realize the conversion of Chirp signal to narrow pulse signal, thereby realize whole wireless transmission process, implementation step is:

1, modulation linearity frequency modulation analog signal is treated in generation, and the expression formula of this signal is: s (t)=a (t) cos (2 π f ₀T+ π μ t ²)-T/2＜t＜T/2;

In the formula, a (t) is the envelope of Chirp signal, rectangular pulse commonly used, and when | t|＜T/2, a (t)=1; Other a (t)=0, T are pulse duration, f ₀It is the centre frequency of Chirp signal.B=|u|T is the bandwidth of Chirp signal, and μ is chirped slope, and μ＞0 is called forward (UP) chirp, and its instantaneous frequency constantly increases; μ＜0 is called oppositely (DOWN) chirp, and its instantaneous frequency constantly reduces;

2, information source and orthogonal code produce information bit b to be modulated respectively _lWith orthogonal code waveform d (t), wherein, b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈, and d (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

3, information bit b _lCarry out the modulation of linear FM signal respectively with orthogonal code waveform d (t);

4, linear FM signal after process information and the orthogonal code modulation and former unmodulated linear FM signal are gone out by antenna transmission through addition;

5, sending signal x (t) is obtained by receiving unit $\tilde{r}\left(t\right)=x\left(t\right)+n\left(t\right);$

6, the signal that receives

Carry out pulse compression, the main energy of signal is compressed in the extremely narrow time domain scope, and the signal after the compression can be regarded the narrow pulse signal r (t) of ultra broadband as;

Wherein the principle of pulse compression is mainly according to having accurate orthogonality between UP-Chirp signal and the DOWN-Chirp signal, and two class signals have good autocorrelation, and its auto-correlation function is Singh's functional form, specifically is expressed as:

${\mathrm{\&psi;}}_{\mathrm{ss}}\left(t\right)=\sqrt{\mathrm{BT}}\left\{\sin \right[\mathrm{\&pi;Bt}(1-|t|/T)/\mathrm{\&pi;Bt}\left]\right\}\cos \left(2\mathrm{\&pi;}{f}_{0}t\right),-T/2<t<T/2---\left(2\right)$

By expression formula as can be known, ψ _Ss(t) get envelope and get the amplitude peak value

Value much larger than cross-correlation function at this moment; When ≈ ± 1/B, ψ _Ss(t) envelope value is zero.And along with the increase of Chirp signal bandwidth B, sidelobe level reduces; B is the bandwidth of Chrip signal, and T is a pulse duration, and f0 is the centre frequency of Chrip signal;

7, through the r (t) after the pulse compression through the signal r after square obtaining handling ²(t);

8, produce local orthogonal code d (t), be used for the despreading of received signal;

9, local orthogonal code d (t) and signal r after treatment ²(t) multiply each other, finish the orthogonal process of separating of signal, eliminate the influence of orthogonal code;

10, the operation result after multiplying each other is carried out integral processing and obtain signal energy r in the integrating range _l, at an integration period T _s, the energy of cumulative signal;

11, to integral processing r as a result _lAdjudicate, decision rule is: $r_l>0,{\hat{b}}_l=1,$ $r_l<0,{\hat{b}}_l=0,$ Thereby obtain information bit

The inventive method uniqueness, advanced person compare with reference to system with the time domain transmission, and this system does not need to simulate time delay device, realizes simple; Send with frequency domain and to compare with reference to system, this system not only performance is dominant, and structure is further simplified, and performance can obviously not worsen along with the increase of multidiameter delay or transmission rate, so suitable transmission rate or transmission range are improved.The COTR-UWB system has possessed the advantage that sends the reference technique system, and implementation structure further simplifies, thereby helps miniaturization and the integrated design of system more.

Four, description of drawings

Fig. 1 is a UP-Chirp signal time-domain-simulation curve chart of the present invention.

Fig. 2 is a DOWN-Chirp signal time-domain-simulation curve chart of the present invention.

Fig. 3 is the auto-correlation function simulation curve figure of UP-Chirp signal of the present invention and DOWN-Chirp signal.

Fig. 4 is the cross-correlation function simulation curve figure of UP-Chirp signal of the present invention and DOWN-Chirp signal.

Fig. 5 is SAW-Chirp-COTR-UWB error rate of system P under the additive white Gaussian noise environment of the present invention _bWith SNR performance simulation curve chart.

Fig. 6 is a present device SAW-Chirp-COTR-UWB transmitter principle structural representation.

Fig. 7 is SAW-Chirp-COTR-UWB transmitter architecture figure of the present invention.

Fig. 8 is SAW-Chirp-COTR-UWB receiver structure figure of the present invention.

Five, embodiment

Below in conjunction with concrete condition and accompanying drawing the specific embodiment of the present invention is elaborated.

By shown in Figure 6, the present invention is realized by following said step when implementing:

1, treat modulation linearity frequency modulation analog signal by cutting general signal generator spare (101) generation, the expression formula of this signal is: s (t)=a (t) cos (2 π f ₀T+ π μ t ²)-T/2＜t＜T/2;

In the formula, a (t) is the envelope of Chirp signal, rectangular pulse commonly used, and when | t|＜T/2, a (t)=1; Other a (t)=0.T is a pulse duration, f ₀It is the centre frequency of Chirp signal.B=|u|T is the bandwidth of Chirp signal, and μ is chirped slope, and μ＞0 is called forward (UP) chirp, and its instantaneous frequency constantly increases; μ＜0 is called oppositely (DOWN) chirp, and its instantaneous frequency constantly reduces, as shown in Figure 1 and Figure 2;

2, information source (104) and orthogonal code latch (105) produce information bit b to be modulated respectively _lWith orthogonal code waveform d (t), wherein, b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈, and d (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

3, information bit b _lCarry out the modulation of linear FM signal by multiplier (102), (103) respectively with orthogonal code waveform d (t);

4, pass through adder (106) addition through linear FM signal after information and the orthogonal code modulation and former unmodulated linear FM signal warp, sent by transmitter antenna, transmitter architecture is seen shown in Figure 7;

5, send signal x (t) through transmission channel (200), under the AWGN environmental condition, obtain by receiver $\tilde{r}\left(t\right)=x\left(t\right)+n\left(t\right);$

6, the signal that receives

Carry out pulse compression by SAW analog filter (201), the main energy of signal is compressed in the extremely narrow time domain scope, and the signal after the compression can be regarded the narrow pulse signal r (t) of ultra broadband as;

Wherein the principle of pulse compression is mainly according to having accurate orthogonality between UP-Chirp signal and the DOWN-Chirp signal, and two class signals have good autocorrelation, and its auto-correlation function is Singh's functional form, specifically is expressed as:

${\mathrm{\&psi;}}_{\mathrm{ss}}\left(t\right)=\sqrt{\mathrm{BT}}\left\{\sin \right[\mathrm{\&pi;Bt}(1-|t|/T)/\mathrm{\&pi;Bt}\left]\right\}\cos \left(2\mathrm{\&pi;}{f}_{0}t\right),-T/2<t<T/2---\left(2\right)$

By expression formula as can be known, ψ _Ss(t) get envelope and get the amplitude peak value

Value much larger than cross-correlation function at this moment; When ≈ ± 1/B, ψ _Ss(t) envelope value is zero.And along with the increase of Chirp signal bandwidth B, sidelobe level reduces;

7, through square processing of the process of the r (t) after pulse compression squarer (202), the signal r after obtaining handling ²(t);

8, produce local orthogonal code d (t) by local orthogonal code memory (204), be used for the despreading of received signal;

9, local orthogonal code d (t) and signal r after treatment ²(t) multiply each other through multiplier (203), finish the orthogonal process of separating of signal, eliminate the influence of orthogonal code;

10, the operation result after multiplier (203) is multiplied each other carries out integral processing and obtains r _l, at an integration period T _s, the energy of cumulative signal;

11, to integral processing r as a result _lAdjudicate, decision rule is: $r_l>0,{\hat{b}}_l=1,$ $r_l<0,{\hat{b}}_l=0,$ Thereby obtain information bit

Said, to have accurate orthogonality between forward in the step 1 (UP) chirp (UP-Chirp) and reverse (DOWN) chirp (DOWN-Chirp), and two class signals have good autocorrelation, and its auto-correlation function is Singh's functional form, specifically is expressed as:

${\mathrm{\&psi;}}_{\mathrm{ss}}\left(t\right)=\sqrt{\mathrm{BT}}\left\{\sin \right[\mathrm{\&pi;Bt}(1-|t|/T)/\mathrm{\&pi;Bt}\left]\right\}\cos \left(2\mathrm{\&pi;}{f}_{0}t\right),-T/2<t<T/2---\left(2\right)$

By expression formula as can be known, ψ _Ss(t) get envelope and get the amplitude peak value

Value much larger than cross-correlation function at this moment; When ≈ ± 1/B, ψ _Ss(t) envelope value is zero.And along with the increase of Chirp signal bandwidth B, sidelobe level reduces.Fig. 3, Fig. 4 have provided the auto-correlation function and the cross-correlation function of UP-Chirp signal and DOWN-Chirp signal.

From simulation curve figure as can be seen, the time domain specification that the auto-correlation function of UP-Chirp signal and DOWN-Chirp signal has burst pulse, the main energy of signal is compressed in the extremely narrow time domain scope.In the receiver design of reality, can adopt analog matched filter to realize the process of this pulse compression, the signal after the compression can be regarded the narrow pulse signal of ultra broadband as.

Said Chirp signal, its SAW-Chirp-COTR-UWB system signal characteristics are that the code-element period of establishing the SAW-Chirp-COTR-UWB system is T _s, the frame period is T _f, comprise a Chirp signal in per frame period, and T arranged _s=N _fT _f, N _fIt is the frame number in each symbol.E _sIt is signal energy in the code-element period.b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈.F (t) is corresponding UP-Chirp or DOWN-Chirp signal, and p () is the UWB time domain narrow pulse signal that forms after this Chirp signal process time domain pulse compression, and its energy is 1/N _f, bandwidth is W, the duration be [0, T _f].L is the code element number in the signal that once transmits.D (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

Define one by N _fThe signal u (t) that individual unmodulated Chirp signal is formed is as follows:

$u\left(t\right)=\underset{n=0}{\overset{N_f-1}{\mathrm{\&Sigma;}}}f(t-{\mathrm{nT}}_f)---\left(3\right)$

Then at the time interval [lT _s, (l+1) T _s] in (that is: code-element period), signal s (t) can be expressed as:

s(t)＝g _l(t-lT _s)u(t-lT _s) (4)

Wherein:

$g_l\left(t\right)=\sqrt{\frac{E_s}{2}}+\sqrt{\frac{E_s}{2}}{b}_{l}d\left(t\right)---\left(5\right)$

So, in the SAW-Chirp-COTR-UWB system, the representation of transmission signals is:

$x\left(t\right)=\underset{l=0}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=0}{\overset{N_f-1}{\mathrm{\&Sigma;}}}(\sqrt{\frac{E_s}{2}}f(t-{\mathrm{lT}}_s-{\mathrm{kT}}_f)+b_l\sqrt{\frac{E_s}{2}}f(t-{\mathrm{lT}}_s-{\mathrm{kT}}_f)d\left(t\right))---\left(6\right)$

The SAW-Chirp-COTR-UWB system performance analysis.

The error rate of SAW-Chirp-COTR-UWB system under additive white Gaussian noise (AWGN) and multipath fading (MP) condition is respectively:

$P_{\mathrm{SAW}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=Q\left(\frac{E_S}{\sqrt{{2\mathrm{<figure-callout\; id="0"\; label="E\; S\; N"\; filenames="A20091006500300141.png,A20091006500300142.png"\; state="\{\{state\}\}">E</figure-callout>}}_S{N}_{}{}_0+{\mathrm{<figure-callout\; id="0"\; label="T\; S\; N"\; filenames="A20091006500300141.png,A20091006500300142.png"\; state="\{\{state\}\}">T</figure-callout>}}_S{N_{}}^{}{{}_0}^{2}W}}\right)---\left(7\right)$

$P_{\mathrm{SAW}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{MP}}=E_{\underset{\&OverBar;}{h}}\left\{Q\left(\frac{E_S\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="A20091006500300171.png"\; state="\{\{state\}\}">l</figure-callout>}}}^2}{\sqrt{2{\mathrm{<figure-callout\; id="0"\; label="E\; S\; N"\; filenames="A20091006500300141.png,A20091006500300142.png"\; state="\{\{state\}\}">E</figure-callout>}}_S{N}_{}{}_0\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="2"\; label="l"\; filenames="A20091006500300171.png"\; state="\{\{state\}\}">l</figure-callout>}}}^2+{\mathrm{<figure-callout\; id="0"\; label="T\; S\; N"\; filenames="A20091006500300141.png,A20091006500300142.png"\; state="\{\{state\}\}">T</figure-callout>}}_S{N_{}}^{}{{}_0}^{2}W}}\right)\right\}---\left(8\right)$

Utilize communication simulation software (MATLAB 7.0), we have provided SAW-Chirp-COTR-UWB error rate of system P under the additive white Gaussian noise environment _bWith SNR performance simulation curve as shown in Figure 5.Wherein B is chirped bandwidth, B=500MHz, and integrating range is chosen as T _Mds=2/B=5ns, data rate R=500Kbit/s, centre frequency f ₀=1.55GHz, E _sBe signal energy in the code-element period, N ₀Be the power spectral density of white Gaussian noise, α _lBe the footpath decay of multipath channel, W is a bandwidth.

Its structure of said transmitter and receiver is provided by Fig. 7, Fig. 8 respectively, transmitter is by microcontroller (IC1) 1, as PIC18F1320, through output termination ultra broadband Chirp signal generator 6, join with ultra broadband power amplifier 8 through isolated DC electric capacity (C) 7, be connected to ultra broadband transmitting antenna 9 on the ultra broadband power amplifier 8, microcontroller 1 is to constitute (above-mentioned each parts are the commercially available prod) by being connected to code conversion module 2, orthogonal code generator module 4, adder Module 5 on the multiplication module 3 respectively; Said receiver is to connect ultra-wideband low-noise amplifier 11 inputs by ultra broadband reception antenna 10, ultra-wideband low-noise amplifier 11 output termination SAW analog filters 12 inputs, SAW analog filter 12 inputs connect the input of power divider 14 through isolated DC electric capacity (C) 13, the input of 14 liang of output of power divider termination the one or four phase multiplier 15, the one or four phase multiplier the 15, the 24 phase multiplier 16 through series connection connects each minute device input of 17, and integrator 17 same microcontrollers (IC2) 22 link to each other and constitute; Said microcontroller (IC2) the 22nd is made up of orthogonal code generator module 18, integration window control module 19, sampling module 20, judging module 21, wherein orthogonal code generator module 18 connects the two or four phase multiplier 16, integration window control module 19 connects integrator 17 inputs, the output of the input termination integrator 17 of sampling module 20, the input of the output termination judging module 21 of sampling module 20, the output termination demodulating data output (above-mentioned each parts are the commercially available prod) of judging module 21.

During its work, the IC1 of said receiver delivers to code conversion module 2 with data after receiving data by IC1-pin10, and data are carried out repeated encoding and reversal, and the data of output are delivered to multiplication module 3;

It is identical and deliver to multiplication module 3 with complete " 1 " yard mutually orthogonal orthogonal code that orthogonal code generator module 4 produces the length of a code length and repeated encoding;

Data and orthogonal code that multiplication module 3 is sent into code conversion module 2 multiply each other, and the data of output are delivered to adder Module 5, finish add operation with " 1 " data that IC1 produces;

The data that 5 pairs of multiplication module 3 of adder Module are brought trigger sequence by IC1-pin18 output after adding " 1 " computing, produce ultra broadband Chirp signal in order to trigger ultra broadband Chirp signal generator 6;

The ultra broadband Chirp signal that ultra broadband Chirp signal generator 6 produces enters ultra broadband power amplifier 8 through partiting dc capacitor C7;

Ultra broadband power amplifier 8 carries out ultra broadband Chirp signal to deliver to ultra-wideband antenna 9 after the power amplification, is launched by ultra-wideband antenna 9.

Fig. 8 is the Chirp-COTR-UWB receiver structure figure based on the SAW device.

After ultra-wideband antenna 10 receives radiofrequency signal, deliver to ultra-wideband low-noise amplifier 11 and carry out exporting after ultra-broadband signal amplifies.

Ultra-wideband low-noise amplifier 11 is sent into SAW analog filter 12 and is carried out exporting after the pulse compression.

Be sent to power divider 14 through the ultra wideband narrow-pulse signal after 12 pulse compressions of SAW analog filter through partiting dc capacitor C 13.Also be sent to four phase multipliers 15 simultaneously carries out multiplying to power divider 14 output two same signals;

The orthogonal code waveform generation module 18 of IC2 inside produces the orthogonal code waveform signals, output in the four phase multipliers 16 through IC2-pin17, and with four mutually the output signal of multiplier 15 multiply each other.The pairing orthogonal code of orthogonal code waveform signal that orthogonal code waveform generation module 18 produces and the orthogonal code of transmitting terminal are synchronous;

The signal that 17 pairs four phase multipliers 15 of integrator are sent here carries out integration.Simultaneously, the integration window control module 19 of IC2 inside is by the integration window of IC2-pin16 control integrator 17;

The output signal of integrator 17 is sent to the sampling module 20 of IC2 inside by IC2-pin10.Behind 20 pairs of signal samplings of sampling module, sampled value is delivered to judging module 21;

21 pairs of sampled values of judging module are adjudicated the back by the IC2-pin18 demodulated output data.

By said structure as can be seen, the present invention replaces with the Chirp signal with narrow pulse signal (typical representative is linear frequency modulation or nonlinear frequency modulation signal, and guarantee that FM signal satisfies the FCC definition), receiving terminal adopts time domain compression or frequency domain compress technique to realize the conversion of Chirp signal to narrow pulse signal, thereby realizes whole wireless transmission process.This solution can solve the efficient communication problem of medium and long distance radio ultra wide band system, and its main advantage is embodied in the following aspects:

(1) kept sending the intrinsic technical advantage of reference pulse ultra broadband;

(2) design cycle of linear frequency sweep according to transmission range, realize can solving gathering to signal energy the serious multipath interference problem of medium and long distance ultra-wideband communications process preferably, and then improve the performance of system at receiving terminal;

(3) when system design, can select working band and bandwidth of operation flexibly according to actual application environment, thereby avoid main interference source, avoid interference simultaneously to other communication system.Simultaneously, receiver has stronger inhibitory action to all kinds of external interference signals;

(4) signal all has good disguise on frequency domain and time domain;

(5) receiving terminal can utilize the gain that linear frequency modulation brings, thereby has improved systematic function effectively;

(6), thereby effectively improved the signal emission effciency owing to employing constant envelope signal structure;

(7) keep the high time resolution characteristic of pulse, possessed the ability of precision distance measurement.

Claims (4)

1, a kind of based on SAW the sign indicating number territory with reference to Chi rp radio ultra wide band system modulation-demo-demodulation method, it is characterized in that, realize by following steps:

(1), produce and to treat modulation linearity frequency modulation analog signal, the expression formula of this signal is: s (t)=a (t) cos (2 π f ₀T+ π μ t ²)-T/2＜t＜T/2;

Wherein, a (t) is the envelope of Chirp signal, rectangular pulse commonly used, and when | t|＜T/2, a (t)=1; Other a (t)=0, T are pulse duration, f ₀Be the centre frequency of Chirp signal, B=|u|T is the bandwidth of Chirp signal, and μ is chirped slope, and μ＞0 is called forward (UP) chirp, and its instantaneous frequency constantly increases; μ＜0 is called oppositely (DOWN) chirp, and its instantaneous frequency constantly reduces;

(2), information source and orthogonal code produce information bit b to be modulated respectively _lWith orthogonal code waveform d (t), wherein, b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈, and d (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

(3), information bit b _lCarry out the modulation of linear FM signal respectively with orthogonal code waveform d (t);

(4), through the linear FM signal after information and the orthogonal code modulation and former unmodulated linear FM signal through addition, go out by antenna transmission;

(5), sending signal x (t) is obtained by receiving unit $\tilde{r}\left(t\right)=x\left(t\right)+n\left(t\right);$

(6), the signal that receives

Carry out pulse compression, the main energy of signal is compressed in the extremely narrow time domain scope, and the signal after the compression can be regarded the narrow pulse signal r (t) of ultra broadband as;

Wherein have accurate orthogonality between the UP-Chirp signal of pulse compression and the DOWN-Chirp signal, and two class signals have good autocorrelation, its auto-correlation function is Singh's functional form:

${\mathrm{\&psi;}}_{\mathrm{ss}}\left(t\right)=\sqrt{\mathrm{BT}}\left\{\sin \right[\mathrm{\&pi;Bt}(1-|t|/T)/\mathrm{\&pi;Bt}\left]\right\}\cos \left(2\mathrm{\&pi;}{f}_{0}t\right)-T/2<t<T/2,$

Wherein, B is the bandwidth of Chrip signal, and T is a pulse duration, and f0 is the centre frequency of Chrip signal;

(7), through the r (t) after the pulse compression through the signal r after square obtaining handling ²(t);

(8), produce local orthogonal code d (t), be used for the despreading of received signal;

(9), local orthogonal code d (t) and signal r after treatment ²(t) multiply each other, finish the orthogonal process of separating of signal, eliminate the influence of orthogonal code;

(10), the operation result after multiplying each other is carried out integral processing and obtain r _l, at an integration period T _s, the energy of cumulative signal;

(11), to integral processing r as a result _lAdjudicate, decision rule is: $r_l>0,{\hat{b}}_l=1,$ $r_l<0,{\hat{b}}_l=0,$ Thereby obtain information bit

2, the sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW according to claim 1 is characterized in that, is realized by following steps:

(1), produce and to treat modulation linearity frequency modulation analog signal, the expression formula of this signal is: s (t)=a (t) cos (2 π f by cutting general signal generator spare (101) ₀T+ π μ t ²)-T/2＜t＜T/2;

Wherein, a (t) is the envelope of Chirp signal, rectangular pulse commonly used, and when | t|＜T/2, a (t)=1; Other a (t)=0, T are pulse duration, f ₀Be the centre frequency of Chirp signal, B=|u|T is the bandwidth of Chirp signal, and μ is chirped slope, and μ＞0 is called forward (UP) chirp, and its instantaneous frequency constantly increases; μ＜0 is called oppositely (DOWN) chirp, and its instantaneous frequency constantly reduces;

(2), information source (104) and orthogonal code latch (105) produce information bit b to be modulated respectively _lWith orthogonal code waveform d (t), wherein, b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈, and d (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

(3), information bit b _lCarry out the modulation of linear FM signal by multiplier (102), (103) respectively with orthogonal code waveform d (t);

(4), through the linear FM signal after information and the orthogonal code modulation and former unmodulated linear FM signal through by adder (106) addition, send by transmitter antenna, transmitter architecture is seen shown in Figure 7;

(5), send signal x (t) through transmission channel (200), under the AWGN environmental condition, obtain by receiver

$\tilde{r}\left(t\right)=x\left(t\right)+n\left(t\right);$

(6), the signal that receives

Carry out pulse compression by SAW analog filter (201), the main energy of signal is compressed in the extremely narrow time domain scope, and the signal after the compression can be regarded the narrow pulse signal r (t) of ultra broadband as;

Wherein the principle of pulse compression is mainly according to having accurate orthogonality between UP-Chirp signal and the DOWN-Chirp signal, and two class signals have good autocorrelation, and its auto-correlation function is Singh's functional form, specifically is expressed as:

${\mathrm{\&psi;}}_{\mathrm{ss}}\left(t\right)=\sqrt{\mathrm{BT}}\left\{\sin \right[\mathrm{\&pi;Bt}(1-|t|/T)/\mathrm{\&pi;Bt}\left]\right\}\cos \left(2\mathrm{\&pi;}{f}_{0}t\right)-T/2<t<T/2,$

Wherein, B is the bandwidth of Chrip signal, and T is a pulse duration, and f0 is the centre frequency of Chrip signal;

(7), through square processing of the process of the r (t) after pulse compression squarer (202), the signal r after obtaining handling ²(t);

(8), produce local orthogonal code d (t), be used for the despreading of received signal by local orthogonal code memory (204);

(9), local orthogonal code d (t) and signal r after treatment ²(t) multiply each other through multiplier (203), finish the orthogonal process of separating of signal, eliminate the influence of orthogonal code;

(10), the operation result after multiplier (203) is multiplied each other carries out integral processing and obtains r _l, at an integration period T _s, the energy of cumulative signal;

(11), to integral processing r as a result _lAdjudicate, decision rule is: $r_l>0,{\hat{b}}_l=1,$ $r_l<0,{\hat{b}}_l=0,$ Thereby obtain information bit

3, the sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW according to claim 1 and 2, it is characterized in that its SAW-Chirp-COTR-UWB system signal characteristics of said Chirp signal is that the code-element period of establishing the SAW-Chirp-COTR-UWB system is T _s, the frame period is T _f, comprise a Chirp signal in per frame period, and T arranged _s=N _fT _f, N _fBe the frame number in each symbol, E _sBe signal energy in the code-element period, b _l{ 1 ,+1} is an information transmitted bit in l the code-element period to ∈, and f (t) is corresponding UP-Chirp or DOWN-Chirp signal, and p () is the UWB time domain narrow pulse signal that forms after this Chirp signal process time domain pulse compression, and its energy is 1/N _f, bandwidth is W, the duration be [0, T _f], L is the code element number in the signal that once transmits, and d (t) is the orthogonal code waveform that the data branch road is adopted, and the cycle is T _s

Define one by N _fThe signal u (t) that individual unmodulated Chirp signal is formed is:

$u\left(t\right)=\underset{n=0}{\overset{N_f-1}{\mathrm{\&Sigma;}}}f(t-n{T}_f),$

Then at the time interval [lT _s, (l+1) T _s] in, signal s (t) is:

s(t)＝g _l(t-lT _s)u(t-lT _s)，

Wherein:

$g_l\left(t\right)=\sqrt{\frac{E_s}{2}}+\sqrt{\frac{E_s}{2}}{b}_{l}d\left(t\right),$

In the SAW-Chirp-COTR-UWB system, the representation of transmission signals is:

$x\left(t\right)=\underset{l=0}{\overset{L}{\mathrm{\&Sigma;}}}\underset{k=0}{\overset{N_f-1}{\mathrm{\&Sigma;}}}(\sqrt{\frac{E_s}{2}}f(t-l{T}_s-k{T}_f)+b_l\sqrt{\frac{E_s}{2}}f(t-l{T}_s-k{T}_f)d\left(t\right)).$

4, the sign indicating number territory method for modulating/demodulating reference Chirp ultra-wideband system based on SAW according to claim 3 is characterized in that the error rate of said SAW-Chirp-COTR-UWB system under additive white Gaussian noise and multipath fading condition is respectively:

$P_{\mathrm{SAW}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=Q\left(\frac{E_S}{\sqrt{2E_S{N}_0+T_S{N_0}^{2}W}}\right),$

$P_{\mathrm{SAW}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{MP}=E_{\underset{\&OverBar;}{h}}}\left\{Q\left(\frac{E_S\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{{\mathrm{\&alpha;}}_l}^2}{\sqrt{2E_S{N}_0\underset{l=0}{\overset{L-1}{\mathrm{\&Sigma;}}}{{\mathrm{\&alpha;}}_l}^2+T_S{N_0}^{2}W}}\right)\right\},$

Wherein B is chirped bandwidth, B=500MHz, and integrating range is chosen as T _Mds=2/B=5ns, data rate R=500Kbit/s, centre frequency f ₀=1.55GHz, E _sBe signal energy in the code-element period, N ₀Be the power spectral density of white Gaussian noise, α _lBe the footpath decay of multipath channel, W is a bandwidth.

Images