CN101552664A - Synchronization method for transmitting reference Chirp ultra- wideband system group based on multiphase filtering code domain - Google Patents

Abstract

The present invention relates to a synchronization method for transmitting reference Chirp ultra- wideband system group based on multiphase filtering code domain which can solve problem of timing synchronization right modulation for receiving signal in remote distance ultra- wideband communication. The method includes steps as follows: modulating, filtering, multi-signal time-delay accumulating by Chirp-UWB signal and local Chirp-UWB signal, transmitting data to threshold, processing data comparing with the time-delay accumulating data, the data over self-adapt threshold processing multi-path identification, comparing the data obtained by threshold comparative with the multi-path data processed factual for making the signal in enabling state, and keeping follow enabling signal in a close state, adjusting operation clock and local oscillation operation clock, confirming clock adjustment sizes and direction according with equivalent signal radial time delay T value size and completing synchronous tracking. The method solves problem of serious multi-path interference in remote distance ultra- wideband communication process, accordingly, increases system property. The method has strong signal disguise, high emission efficiency, high resolving capability and high range accuracy.

Description

Send the reference Chirp ultra-wideband system group method for synchronous based on multiphase filtering code domain

One, technical field

The present invention relates to the communications field, particularly a kind ofly send with reference to Chi rp radio ultra wide band system group synchronization method based on multiphase filtering code domain.

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.

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.

In communication system, receiver performance is subjected to the influence of net synchronization capability to a great extent, system be the prerequisite that receiving terminal correctly recovers digital information synchronously.The reduction of net synchronization capability will cause the decline of communication system performance, even the system that makes can't operate as normal.Equally, in the Chirp-COTR-UWB system,, require synchronously accurate because the influence of factors such as frequency difference between the transmitting-receiving local oscillator and propagation delay time will realize the correct demodulation of signal.

In the system design of receiving terminal, if adopt the simulation process method, its main defective is to handle dumb, and receptivity is difficult to satisfy the demand of system design.If adopt digital signal processing method, suppose that the bandwidth of Chirp-UWB signal is 500MHZ, want to recover preferably relevant information, according to nyquist sampling theorem, the sample rate (more than the 1GHz) that inevitable requirement is higher.This just makes the processing pressure of system digits part increase, thereby makes the complexity and the difficulty that realize strengthen.

For the synchronizing process of system,, can obtain accurate relatively timing accuracy in theory if under the condition of permission of chip device level and suitable treatments algorithm.But, on the one hand in existing logical device, owing to be subjected to the restriction (the mainstream chip operating frequency is in 100,000,000 magnitudes at present) of its operating frequency, seek out the accurate delay of ns level and be not easy.On the other hand, on specific implementation,,, need expend a large amount of logical blocks if adopt the structure of matched filtering because the symbol sampler point that high sampling causes reaches thousands of points; If adopt slip relevant treatment algorithm, because a plurality of cycle fine searchings cause lock in time long.

Three, summary of the invention

At above-mentioned situation, for overcoming the prior art deficiency, the present invention's purpose just provides a kind of based on multiphase filtering code domain transmission reference Chirp ultra-wideband system group method for synchronous, can effectively solve the regularly synchronous correctly problem of demodulation of received signal in the medium and long distance ultra-wideband communications, the technical scheme of its solution is:

1, produce linear frequency modulation Chirp signal under initial condition, this signal is:

s(t)＝a(t)cos(2πf ₀t+πμt 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 ₀Be the centre frequency of Chirp signal, B=| μ | 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;

Produce local linear frequency modulation Chirp-UWB signal again by the Chirp signal;

2, the Chirp-UWB signal that receives of reception antenna and the local Chirp-UWB signal that produces are finished the line of separating of signal and are transferred process by multiplying each other, must separate the signal after line is transferred;

3, the signal of separating after line is transferred is carried out filtering;

4, near filtering is mixed to narrow band signal zero-frequency, and finish frequency-domain analysis to data;

5, after the frequency-domain analysis, carry out many symbols delay accumulation;

6, data are sent into thresholding, according to the energy of input signal, determine the adaptive threshold value, the computational methods of adaptive threshold value are:

σ＝N(E ₁+E ₂+Λ+E _M)/2M

E wherein ₁, E ₂, Λ, E _MBe to send into the M way band data value that thresholding produces submodule, N is the adaptive threshold weights, is defined as N ≈ 3 according to simulation result;

7, adaptive threshold value σ and delay accumulation data are carried out numeric ratio, and the data that surpass adaptive threshold value σ are carried out the multipath identification, finish the initial option of multipath;

8, the data that relatively obtain of thresholding and the multipath numerical value of actual treatment compare;

The renewal of 9, stepping time delay when multipath data sum during greater than the multipath data sum of buffer area, is upgraded the N footpath data of this generation and corresponding time-delay designation data of this time sliding, otherwise is not upgraded;

10, make signal be in enabled state, keep following the tracks of enable signal and be in cut-off state;

11, produce corresponding clock according to the multipath data and adjust index signal, method is:

If the corresponding data value in N footpath is respectively E ₁, E ₂, Λ, E _N, corresponding frequency deviation value is respectively F ₁, F ₂, Λ, F _N, corresponding time delay value is respectively T ₁, T ₂, Λ, T _NAnd to establish the single footpath of equivalence data value be E, and the single footpath of equivalence frequency deviation is F, and the single footpath of equivalence time delay is T, and signal bandwidth is W, and character rate is T _s, need to prove frequency deviation value F ₁, F ₂, Λ, F _NCan obtain by the corresponding channel number in each footpath, and span be (B/2, B/2),

Then there is following relation:

E＝(E ₁+E ₂+Λ+E _N)/N

F＝(F ₁+F ₂+Λ+F _N)/N

T＝FT _s/W

12, adjust designation data according to clock and adjust work clock and local oscillator work clock, size according to the single footpath of equivalence time delay T value is determined the size that clock is adjusted, determine the direction that clock is adjusted according to the size of equivalence single footpath time delay value (T value), thereby finish this subsynchronous tracing process.

The inventive method section emulates the advanced, uniqueness, both kept sending the intrinsic technical advantage of reference pulse ultra broadband, design the cycle and the bandwidth of linear frequency sweep again according to the transmission line distance,, can solve the serious multipath interference problem of medium and long distance ultra-wideband communications process preferably in the gathering of receiving terminal realization to signal energy, and then improved the performance of system, signal is disguised strong, emission effciency height, resolution height, the range accuracy height is that one in the communication is created greatly.

Four, description of drawings

Fig. 1 is an ASC-Chirp-COTR-UWB transmitter model of the present invention.

Fig. 2 is an ASC-Chirp-COTR-UWB receiver module of the present invention.

Fig. 3 is synchronization acquistion of the present invention and tracking module illustrative view of functional configuration.

Five, embodiment

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

By shown in Figure 3, the present invention is realized by following steps in concrete enforcement:

1, local Chirp-UWB signal generator (4) produces linear FM signal under a certain initial condition, and this signal is:

s(t)＝a(t)cos(2πf ₀t+πμt 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 ₀Be the centre frequency of Chirp signal, B=| μ | 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;

Produce local linear frequency modulation Chirp-UWB signal again by the Chirp signal, the ASC-Chirp-COTR-UWB system configuration of this signal is: the code-element period of definition ASC-Chirp-COTR-UWB system is T _s, b _l{ 1 ,+1} is l to ∈ ^ThInformation transmitted bit in the individual code-element period, m (t) treats base band signal modulated, signal energy is E in the code-element period _s, promptly $E_s={\∫}_0^{T_S}{m}^2\left(t\right)\mathrm{dt},$ C _{L, I}∈ 1 ,+1} and C _{L, Q}{ 1 ,+1} is respectively l to ∈ ^ThThe orthogonal code of data branch road and reference arm in the individual code-element period, the chip width is T _c, and T is arranged _s=NT _c, N is an orthogonal code length, cos (2 π f ₀T+ π μ t ²) be the expression formula of linear FM signal, f ₀Be the centre frequency of linear FM signal, | t|≤T/2, μ=± B/T, wherein B is the bandwidth of linear FM signal, T is the frequency sweep cycle of linear FM signal, T=MT _s=B/| μ |, M is the symbol period ratio of linear FM signal frequency sweep cycle and signal, the bandwidth of low pass filter is W, and W=1/T _c, H (f) is the frequency response (seeing Fig. 1, shown in Figure 2) of low pass filter;

In the ASC-Chirp-COTR-UWB system, l ^ThThe transmission signals of code element can be expressed as:

x(t)＝(b _lC _l，I+C _l，Q)m(t)cos(2πf ₀t+πμt ²)

The principle Analysis of ASC-Chirp-COTR-UWB system is as follows, under desirable synchronous situation, ignores The noise, then has:

y(t)＝x(t)

Under the condition of system's ideal synchronisation, through receiver separate that line is transferred and ideal low-pass filter after, output signal r (t) can be expressed as:

r(t)＝(b _lC _l，I+C _l，Q)m(t)/2

Analysis receiver is exported first information bit b ₀Situation, make integrator be output as r ₀, then have:

$r_0={\∫}_0^{T_S}{r}^2\left(t\right)C_{l,I}{C}_{l,Q}\mathrm{dt}$

$=\frac{1}{4}{\∫}_0^{T_S}{(b_0{C}_{l,I}+C_{l,Q})}^2{C}_{l,I}{C}_{l,Q}{m}^2\left(t\right)\mathrm{dt}$

$=\frac{1}{2}{\∫}_0^{T_S}(C_{l,I}{C}_{l,Q}+b_0)m^2\left(t\right)\mathrm{dt}$

$=\frac{b_0{\mathrm{<figure-callout\; id="2"\; label="E\; s"\; filenames="A20091006500400171.png,A20091006500400181.png"\; state="\{\{state\}\}">E</figure-callout>}}_s}{2}$

According to the ASC-Chirp-COTR-UWB system configuration as can be known, ASC-Chirp-COTR-UWB and basic identical based on the standard C OTR-UWB system principle of pulse, under the additive white Gaussian noise condition, the l of this system ^ThThe received signal y of code element (t) can be expressed as:

y(t)＝(b _lC _l，I+C _l，Q)m(t)cos[2πf ₀t+πμt ²]+n(t)

Wherein n (t) is that average is zero, bilateral power spectral density is N ₀/ 2 additive white Gaussian noise,

After the quadrature of process receiver was separated linear frequency modulation and low-pass filtering, output signal r (t) can be expressed as:

$r\left(t\right)=\frac{1}{2}(b_l{C}_{l,I}+C_{l,Q})m\left(t\right)+n^{\&prime;}\left(t\right)$

Wherein n ' (t) can be similar to and regards that average is zero, bilateral power spectral density is as | H (f) | ²N ₀/ 2 band limited white noise is for first information bit b ₀, the output r of receiver integrator ₀Can be expressed as:

$r_0={\&Integral;}_0^{T_S}{r}^2\left(t\right)C_{l,I}{C}_{l,Q}\mathrm{dt}$

$=\frac{b_0{\mathrm{<figure-callout\; id="2"\; label="E\; s"\; filenames="A20091006500400171.png,A20091006500400181.png"\; state="\{\{state\}\}">E</figure-callout>}}_s}{2}+n_0$

Wherein the noise item of integrator output can be regarded a stochastic variable n as ₀, this stochastic variable proves an approximate Gaussian noise easily, and its average and variance are respectively:

E{n ₀}＝0

E{n ₀ ²}＝ME _sN ₀+M ²T _sN ₀ ²W

According to the characteristic of ASC-Chirp-COTR-UWB system as can be known, its BER formulas under the additive white Gaussian noise condition can be expressed as:

$P_{\mathrm{ASC}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=\frac{1}{2}\exp (-\frac{E_s}{{2\mathrm{MN}}_0})$

The error rate of known standard COTR-UWB system is:

$P_{\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=Q\left(\frac{E_s}{\sqrt{{2E}_s{N}_0+T_s{N_0}^{2}W}}\right)$

Wherein the Q function is:

$Q\left(x\right)=\frac{1}{\sqrt{2\mathrm{\&pi;}}}{\&Integral;}_x^{\&infin;}\exp (-\frac{{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="A20091006500400171.png,A20091006500400181.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}{2})\mathrm{dy}$

Compare as can be known with the error rate expression formula of standard C OTR-UWB system, because the bandwidth W of standard C OTR-UWB system low pass filter is the bandwidth of narrow pulse signal, therefore influenced by the product term of noise and noise bigger for standard C OTR-UWB error rate of system performance, therefore, under general condition ASC-Chirp-COTR-UWB error rate of system performance obviously is better than standard C OTR-UWB system, is more suitable for the requirement of medium and long distance ultra-wideband communications;

2, the Chirp-UWB signal that local Chirp signal generator (4) produces in the Chirp-UWB signal that receives of reception antenna and the step 1 is finished the line accent process of separating of signal by multiplier (1);

3, because the asynchronous regime of the received signal of local signal, promptly has the regular hour deviation between two signals, because the particularity of Chirp-UWB signal, the deviation of time has caused the frequency departure of signal, the signal that feasible process is separated after line is transferred has certain bandwidth, this signal enters FPGA (be microcontroller, can adopt the EPZS90F780 chip) by simulation low-pass filter (2);

4, the signal process multiphase filter group (3) that receives is mixed to narrow band signal near the zero-frequency, wherein the number of filter of multinomial bank of filters is M, when system is in the synchronization acquistion state, the M way band data that the multiphase filtering module is sent into are sent into the delivery integration submodule (6) in synchronization acquistion and the tracking module, finish the frequency-domain analysis process to M way band data;

In fact synchronization acquistion problem based on the Chirp-COTR-UWB system of ASC structure has comprised sign synchronization and two aspects of chip synchronization, according to the signal structure that sends as can be known, finish at receiving terminal sign synchronization has been realized the chip synchronization process in fact simultaneously, therefore, synchronization acquistion at the Chirp-COTR-UWB system only need be considered the sign synchronization problem, mainly, realize catching following function with the group at the group of multipath signal by analyzing the spectrum analysis result in the system handles bandwidth that the multiphase filtering module sends into;

When system is in the synchronization acquistion state, the M way band data that the multiphase filtering module is sent into are sent into the delivery integration submodule in synchronization acquistion and the tracking module, finish frequency-domain analysis process to M way band data, because the existence of random noise, for guaranteeing certainty to frequency-domain analysis, and the signal to noise ratio of raising spectrum analysis, the data of delivery integration submodule need be carried out many symbols delay accumulation, the M way band data that obtain this moment can seen the frequency-domain analysis in whole system is handled bandwidth B, and the precision of frequency-domain analysis is B/M;

M way band data are sent into thresholding produce submodule, determine the adaptive threshold value according to the energy of input signal, the computational methods of adaptive threshold value σ are as follows:

σ＝N(E ₁+E ₂+Λ+E _M)/2M

E wherein ₁, E ₂, Λ, E _MBe to send into the M way band data value that thresholding produces submodule, N is the adaptive threshold weights, is defined as N ≈ 3 according to simulation result;

The M way band data that adaptive threshold σ that thresholding generation submodule produces and delay accumulation submodule are sent into are carried out numeric ratio in the thresholding comparison sub-module, M ' footpath the data that surpass adaptive threshold value σ are sent into multipath identification submodule, finish the initial option of multipath;

M ' footpath data are sent into multipath identification submodule, and the multipath of system's actual treatment is counted N to multipath identification submodule and M ' compares, and when M '≤N, multipath identification submodule is handled the back with M ' footpath data by zero padding and formed N footpath data; When M '＞N, multipath identification submodule is selected and is chosen N footpath data greatly, in the N footpath data that multipath identification submodule forms and the multipath metadata cache submodule the N of buffer memory directly data compare, when this N footpath data sum during greater than the N footpath data sum of buffer area, the N footpath data of this generation and the corresponding time-delay of this time sliding are indicated the data of upgrading in the cache sub-module, otherwise do not upgrade, multipath identification submodule keeps catching enable signal and is in enabled state, keep following the tracks of enable signal and be in cut-off state, catch enable signal when being in enabled state when what multipath identification submodule was sent into, stepping adjustment indication submodule forms stepping according to the step value of setting and adjusts index signal and send into the Chirp signal generator module, simultaneously multipath identification submodule is sent in the time delay indication of this slip, thereby enter the trapped state of next time sliding, simultaneously, multipath metadata cache submodule is sent N footpath data in the buffer area and corresponding time delay indication into time delay estimator module, finish calculating, and corresponding stored is at multipath metadata cache submodule to the N footpath time delay value of this N footpath data correspondence;

After whole slip acquisition procedure is finished, the enable signal of catching that multipath identification submodule will be sent into stepping adjustment indication submodule is changed to cut-off state, thereby stop whole slip acquisition procedure, at this moment, multipath identification submodule will be followed the tracks of enable signal and be changed to enabled state, and system enters synchronous tracking mode;

5, because the existence of random noise is the certainty of assurance to frequency-domain analysis, and improve the signal to noise ratio of spectrum analysis, the data process delay accumulation modules (7) of delivery integration submodule need be carried out many symbols delay accumulation;

6, M way band data are sent into thresholding and produced submodule (10), determine the adaptive threshold value according to the energy of input signal, the computational methods of adaptive threshold value σ are as follows:

σ＝N(E ₁+E ₂+Λ+E _M)/2M

E wherein ₁, E ₂, Λ, E _MBe to send into the M way band data value that thresholding produces submodule, N is the adaptive threshold weights, is defined as N ≈ 3 according to simulation result;

7, thresholding produces the M way band data that adaptive threshold σ that submodule produces and delay accumulation submodule send into and carries out numeric ratio in thresholding comparison sub-module (11), M ' footpath the data that surpass adaptive threshold value σ are sent into multipath identification submodule, finish the initial option of multipath;

8, the M ' footpath data that relatively obtain of thresholding are sent into multipath identification submodule (12), the multipath of system's actual treatment is counted N to multipath identification submodule and M ' compares, when M '≤N, multipath identification submodule is handled the back with M ' footpath data by zero padding and is formed N footpath data; When M '＞N, multipath identification submodule is selected and is chosen N footpath data greatly, in the N footpath data that multipath identification submodule forms and the multipath metadata cache submodule the N of buffer memory directly data compare;

The renewal of 9, stepping time delay, the N footpath data sum during previous step is rapid be during greater than the N footpath data sum of buffer area, data in cache sub-module (14) upgraded in the N footpath data of this generation and the corresponding time-delay of this time sliding indication, otherwise do not upgraded;

10, multipath identification submodule keeps catching enable signal and is in enabled state, keep following the tracks of enable signal and be in cut-off state, catch enable signal when being in enabled state when what multipath identification submodule was sent into, stepping adjustment indication submodule forms stepping according to the step value of setting and adjusts index signal and send into Chirp signal generator module (4), simultaneously multipath identification submodule is sent in the time delay indication of this slip, thereby enter the trapped state of next time sliding, simultaneously, multipath metadata cache submodule is sent N footpath data in the buffer area and corresponding time delay indication into time delay estimator module, finish calculating, and corresponding stored is at multipath metadata cache submodule (15) to the N footpath time delay value of this N footpath data correspondence;

11, after whole slip acquisition procedure is finished, the enable signal of catching that multipath identification submodule will be sent into stepping adjustment indication submodule (8) is changed to cut-off state, thereby stop whole slip acquisition procedure, at this moment, multipath identification submodule will be followed the tracks of enable signal and be changed to enabled state, and system enters synchronous tracking mode;

12, when system is in synchronous tracking mode, multipath comparison sub-module in synchronization acquistion and the tracking module reads the multipath data in the multipath data buffer area, and with the adjusted multipath data of the preceding subsynchronous tracking of multipath comparison sub-module buffer memory relatively, if twice multipath data value sum changes, then this time tracing process is not adjusted the position that clock is adjusted index signal, thereby enters synchronous next time tracking mode; If twice not change of multipath data value sum then produces corresponding clock according to N footpath data and adjust index signal, the production process of clock adjustment index signal is as follows:

If the corresponding data value in N footpath is respectively E ₁, E ₂, Λ, E _N, corresponding frequency deviation value is respectively F ₁, F ₂, Λ, F _N, corresponding time delay value is respectively T ₁, T ₂, Λ, T _NAnd to establish the single footpath of equivalence data value be E, and the single footpath of equivalence frequency deviation is F, and the single footpath of equivalence time delay is T, and signal bandwidth is W, and character rate is T _s, need to prove frequency deviation value F ₁, F ₂, Λ, F _NCan obtain by the corresponding channel number in each footpath, and span be (B/2, B/2),

Then there is following relation:

E＝(E ₁+E ₂+Λ+E _N)/N

F＝(F ₁+F ₂+Λ+F _N)/N

T＝FT _s/W

13, according to the work clock in clock adjustment indication (9) adjustment work clock and the local oscillator generation module (5), size according to the single footpath of the rapid middle equivalence of previous step time delay T value is determined the size that clock is adjusted, the direction of adjusting according to the positive and negative definite clock of T value, thus this subsynchronous tracing process finished.

By above-mentioned situation 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 the cycle and the bandwidth 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 frequency range and bandwidth of operation flexibly according to actual application environment, thereby avoid main interference source, avoid interference simultaneously to other communication system.In addition, 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 (3)

1, a kind ofly send the reference Chirp ultra-wideband system group method for synchronous, it is characterized in that, realize by following steps based on multiphase filtering code domain:

(1), under initial condition, produce linear frequency modulation Chirp signal, this signal is:

s(t)＝a(t)cos(2πf ₀t+πμt ²)-T/2＜t＜T/2

In the formula, a (t) is the envelope of Chi rp 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=| μ | 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;

Produce local linear frequency modulation Chirp-UWB signal again by the Chirp signal;

(2), the Chirp-UWB signal that receives of reception antenna and the local Chirp-UWB signal that produces, finish the line of separating of signal by multiplying each other and transfer, must separate the signal after line is transferred;

(3), the signal of separating after line is transferred is carried out filtering;

(4), near filtering is mixed to narrow band signal zero-frequency, and finish frequency-domain analysis to data;

(5), after the frequency-domain analysis, carry out many symbols delay accumulation;

(6), data are sent into thresholding, according to the energy of input signal, determine the adaptive threshold value, the computational methods of adaptive threshold value are:

σ＝N(E ₁+E ₂+Λ+E _M)/2M

E wherein ₁, E ₂, Λ, E _MBe to send into the M way band data value that thresholding produces submodule, N is the adaptive threshold weights;

(7), adaptive threshold value σ and delay accumulation data carry out numeric ratio, the data that surpass adaptive threshold value σ are carried out the multipath identification, finish the initial option of multipath;

(8), the data that relatively obtain of thresholding and the multipath numerical value of actual treatment compare;

(9), the renewal of stepping time delay, when multipath data sum during, the N footpath data of this generation and corresponding time-delay designation data of this time sliding are upgraded, otherwise are not upgraded greater than the multipath data sum of buffer area;

(10), make signal be in enabled state, keep to follow the tracks of enable signal and be in cut-off state;

(11), produce corresponding clock according to the multipath data and adjust index signal, method is:

If the corresponding data value in N footpath is respectively E ₁, E ₂, Λ, E _N, corresponding frequency deviation value is respectively F ₁, F ₂, Λ, F _N, corresponding time delay value is respectively T ₁, T ₂, Λ, T _NAnd to establish the single footpath of equivalence data value be E, and the single footpath of equivalence frequency deviation is F, and the single footpath of equivalence time delay is T, and signal bandwidth is W, and character rate is T _s, need to prove frequency deviation value F ₁, F ₂, Λ, F _NCan obtain by the corresponding channel number in each footpath, and span be (B/2, B/2),

Then there is following relation:

E＝(E ₁+E ₂+Λ+E _N)/N

F＝(F ₁+F ₂+Λ+F _N)/N

T＝FT _s/W

(12), adjust designation data according to clock and adjust work clock and local oscillator work clock, size according to the single footpath of equivalence time delay T value is determined the size that clock is adjusted, size according to the single footpath of equivalence time delay value is determined the direction that clock is adjusted, thereby finishes this subsynchronous tracing process.

2, according to claim 1ly send the reference Chirp ultra-wideband system group method for synchronous, it is characterized in that, realize by following steps based on multiphase filtering code domain:

(1), local Chirp-UWB signal generator (4) produces linear FM signal under initial condition, this signal is:

s(t)＝a(t)cos(2πf ₀t+πμt ²)-T/2＜t＜T/2

In the formula, a (t) is the envelope of Chi rp 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=| μ | T is the bandwidth of Chirp signal, and μ is chirped slope, and μ＞0 is called the forward chirp, and its instantaneous frequency constantly increases; μ＜0 is called the counter chirped pulse, and its instantaneous frequency constantly reduces;

Produce local linear frequency modulation Chirp-UWB signal again by the Chirp signal;

(2), the Chirp-UWB signal that produces of the Chirp-UWB signal that receives of reception antenna and local Chirp signal generator (4) is finished the line accent process of separating of signal by multiplier (1);

(3), the signal after separating line and transferring is carried out filtering, promptly this signal enters microcontroller (FPGA) by simulation low-pass filter (2);

(4), near filtering is mixed to narrow band signal zero-frequency, and finish frequency-domain analysis to data, the signal process multiphase filter group (3) that promptly receives is mixed to narrow band signal near the zero-frequency, wherein the number of filter of multinomial bank of filters is M, when system is in the synchronization acquistion state, the M way band data that the multiphase filtering module is sent into are sent into the delivery integration submodule (6) in synchronization acquistion and the tracking module, finish the frequency-domain analysis process to M way band data;

(5), after the frequency-domain analysis, carry out many symbols delay accumulation, because the existence of random noise, for guaranteeing certainty to frequency-domain analysis, and improve the signal to noise ratio of spectrum analysis, the data of delivery integration submodule are carried out many symbols delay accumulation through delay accumulation module (7);

(6), M way band data sent into thresholding produce submodule (10), determine the adaptive threshold value according to the energy of input signal, the computational methods of adaptive threshold value σ are:

σ＝N(E ₁+E ₂+Λ+E _M)/2M

E wherein ₁, E ₂, Λ, E _MBe to send into the M way band data value that thresholding produces submodule, N is the adaptive threshold weights, is defined as N ≈ 3 according to simulation result;

(7), thresholding produces the M way band data that adaptive threshold σ that submodule produces and delay accumulation submodule send into and carries out numeric ratio in thresholding comparison sub-module (11), M ' footpath the data that surpass adaptive threshold value σ are sent into multipath identification submodule, finish the initial option of multipath;

(8), the data that relatively obtain of thresholding and the multipath numerical value of actual treatment compare, M ' footpath the data that thresholding relatively obtains are sent into multipath identification submodule (12), the multipath of system's actual treatment is counted N to multipath identification submodule and M ' compares, when M '≤N, multipath identification submodule is handled the back with M ' footpath data by zero padding and is formed N footpath data; When M '＞N, multipath identification submodule is selected and is chosen N footpath data greatly, in the N footpath data that multipath identification submodule forms and the multipath metadata cache submodule the N of buffer memory directly data compare;

(9), the renewal of stepping time delay, the N footpath data sum during previous step is rapid is during greater than the N footpath data sum of buffer area, data in cache sub-module (14) upgraded in the N footpath data of this generation and the corresponding time-delay of this time sliding indication, otherwise do not upgraded;

(10), multipath identification submodule keeps catching enable signal and is in enabled state, keep following the tracks of enable signal and be in cut-off state, catch enable signal when being in enabled state when what multipath identification submodule was sent into, stepping adjustment indication submodule forms stepping according to the step value of setting and adjusts index signal and send into Chirp signal generator module (4), simultaneously multipath identification submodule is sent in the time delay indication of this slip, thereby enter the trapped state of next time sliding, simultaneously, multipath metadata cache submodule is sent N footpath data in the buffer area and corresponding time delay indication into time delay estimator module, finish calculating to the N footpath time delay value of this N footpath data correspondence, and corresponding stored is at multipath metadata cache submodule (15), after whole slip acquisition procedure is finished, the enable signal of catching that multipath identification submodule will be sent into stepping adjustment indication submodule (8) is changed to cut-off state, thereby stop whole slip acquisition procedure, at this moment, multipath identification submodule will be followed the tracks of enable signal and be changed to enabled state, and system enters synchronous tracking mode;

(11), produce corresponding clock according to the multipath data and adjust index signal, when system is in synchronous tracking mode, multipath comparison sub-module in synchronization acquistion and the tracking module reads the multipath data in the multipath data buffer area, and with the adjusted multipath data of the preceding subsynchronous tracking of multipath comparison sub-module buffer memory relatively, if twice multipath data value sum changes, then this time tracing process is not adjusted the position that clock is adjusted index signal, thereby enters synchronous next time tracking mode; If twice multipath data value sum do not change, then produce corresponding clock and adjust index signal according to N footpath data, the production method that clock is adjusted index signal is:

If the corresponding data value in N footpath is respectively E ₁, E ₂, Λ, E _N, corresponding frequency deviation value is respectively F ₁, F ₂, Λ, F _N, corresponding time delay value is respectively T ₁, T ₂, Λ, T _NAnd to establish the single footpath of equivalence data value be E, and the single footpath of equivalence frequency deviation is F, and the single footpath of equivalence time delay is T, and signal bandwidth is W, and character rate is T _s, need to prove frequency deviation value F ₁, F ₂, Λ, F _NCan obtain by the corresponding channel number in each footpath, and span be (B/2, B/2),

Then there is following relation:

E＝(E ₁+E ₂+Λ+E _N)/N

F＝(F ₁+F ₂+Λ+F _N)/N

T＝FT _s/W

(12), according to the work clock in clock adjustment indication (9) adjustment work clock and the local oscillator generation module (5), size according to the single footpath of the rapid middle equivalence of previous step time delay T value is determined the size that clock is adjusted, the direction of adjusting according to the positive and negative definite clock of T value, thus this subsynchronous tracing process finished.

3, according to claim 1 and 2 based on multiphase filtering code domain transmission reference Chirp ultra-wideband system group method for synchronous, it is characterized in that, said Chirp-UWB signal, its ASC-Chirp-COTR-UWB system basic structure is: the code-element period of definition ASC-Chirp-COTR-UWB system is T _s, b _l{ 1 ,+1} is l to ∈ ^ThInformation transmitted bit in the individual code-element period, m (t) treats base band signal modulated, signal energy is E in the code-element period _s, promptly $E_s={\&Integral;}_0^{T_S}{m}^2\left(t\right)\mathrm{dt},$ C _{L, I}∈ 1 ,+1} and C _{L, Q}{ 1 ,+1} is respectively l to ∈ ^ThThe orthogonal code of data branch road and reference arm in the individual code-element period, the chip width is T _c, and T is arranged _s=NT _c, N is an orthogonal code length, cos (2 π f ₀T+ π μ t ²) be the expression formula of linear FM signal, f ₀Be the centre frequency of linear FM signal, | t|≤T/2, μ=± B/T, wherein B is the bandwidth of linear FM signal, T is the frequency sweep cycle of linear FM signal, T=MT _s=B/| μ |, M is the symbol period ratio of linear FM signal frequency sweep cycle and signal, the bandwidth of low pass filter is W, and W=1/T _c, H (f) is the frequency response (seeing Fig. 1, shown in Figure 2) of low pass filter;

In the ASC-Chirp-COTR-UWB system, l ^ThThe transmission signals of code element can be expressed as:

x(t)＝(b _lC _l，I+C _l，Q)m(t)cos(2πf ₀t+πμt ²)

The principle Analysis of ASC-Chirp-COTR-UWB system is as follows, under desirable synchronous situation, ignores The noise, then has:

y(t)＝x(t)

Under the condition of system's ideal synchronisation, through receiver separate that line is transferred and ideal low-pass filter after, output signal r (t) can be expressed as:

r(t)＝(b _lC _l，I+C _l，Q)m(t)/2

Analysis receiver is exported first information bit b ₀Situation, make integrator be output as r ₀, then have:

$r_0={\&Integral;}_0^{T_S}{r}^2\left(t\right)C_{l,I}{C}_{l,Q}\mathrm{dt}$

$=\frac{1}{4}{\&Integral;}_0^{T_S}{(b_0{C}_{l,I}+C_{l,Q})}^2{C}_{l,I}{C}_{l,Q}{m}^2\left(t\right)\mathrm{dt}$

$=\frac{1}{2}{\&Integral;}_0^{T_S}(C_{l,I}{C}_{l,Q}+b_0)m^2\left(t\right)\mathrm{dt}$

$=\frac{b_0{E}_s}{2}$

According to the ASC-Chirp-COTR-UWB system configuration as can be known, ASC-Chirp-COTR-UWB and basic identical based on the standard C OTR-UWB system principle of pulse, under the additive white Gaussian noise condition, the l of this system ^ThThe received signal y of code element (t) can be expressed as:

y(t)＝(b _lC _l，I+C _l，Q)m(t)cos[2πf ₀t+πμt ²]+n(t)

Wherein n (t) is that average is zero, bilateral power spectral density is N ₀/ 2 additive white Gaussian noise,

After the quadrature of process receiver was separated linear frequency modulation and low-pass filtering, output signal r (t) can be expressed as:

$r\left(t\right)=\frac{1}{2}(b_l{C}_{l,I}+C_{l,Q})m\left(t\right)+n^{\&prime;}\left(t\right)$

Wherein n ' (t) can be similar to and regards that average is zero, bilateral power spectral density is as | H (f) | ²N ₀/ 2 band limited white noise is for first information bit b ₀, the output r of receiver integrator ₀Can be expressed as:

$r_0={\&Integral;}_0^{T_S}{r}^2\left(t\right)C_{l,I}{C}_{l,Q}\mathrm{dt}$

$=\frac{b_0{E}_s}{2}+n_0$

Wherein the noise item of integrator output can be regarded a stochastic variable n as ₀, this stochastic variable proves an approximate Gaussian noise easily, and its average and variance are respectively:

E{n ₀}＝0

E{n ₀ ²}＝ME _sN ₀+M ²T _sN ₀ ²W

According to the characteristic of ASC-Chirp-COTR-UWB system as can be known, its BER formulas under the additive white Gaussian noise condition can be expressed as:

$P_{\mathrm{ASC}-\mathrm{Chirp}-\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=\frac{1}{2}\exp (-\frac{E_s}{2{\mathrm{MN}}_0})$

The error rate of known standard COTR-UWB system is:

$P_{\mathrm{COTR}-\mathrm{UWB},\mathrm{AWGN}}=Q\left(\frac{E_s}{\sqrt{{2E}_s{N}_0+T_s{N_0}^{2}W}}\right)$

Wherein the Q function is:

$Q\left(x\right)=\frac{1}{\sqrt{2\mathrm{\&pi;}}}{\&Integral;}_x^{\&infin;}\exp (-\frac{y^2}{2})\mathrm{dy}.$

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