CN103944845A - Related detection method for full-frequency-spectrum carrier modulation - Google Patents

Abstract

The invention discloses a related detection method for full-frequency-spectrum carrier modulation, and relates to wireless communication. The method includes the sending end signal processing step and the receiving end signal processing step. In the sending end signal processing step, an information source generates data information, and QPSK symbol mapping is conducted on the data information; mapped symbol information is modulated into a chirp waveform so that the full-frequency-spectrum modulation mode can be achieved, and multiple paths of modulated chirp signals are superposed through an adder and then outputted; the superposed modulation signals pass through a D/A converter and a signal power amplifier and are finally sent to a channel. In the receiving end signal processing step, the received signals pass through a filter amplifier and an A/D converter so that moderately-processed digital signals can be obtained; an uncorrelated demodulation method is adopted for the system, imaginary parts are introduced to the received signals and local signals so as to assist in related detection processing, various types of specific related calculation exist, and all paths of symbol information can be separated through the related calculation; symbol demapping is conducted on the separated symbol information, and then bit information is outputted.

Description

The related detecting method of entire spectrum carrier modulation

Technical field

The present invention relates to radio communication, particularly relate to a kind of related detecting method of entire spectrum carrier modulation.

Background technology

In wireless communication technology evolution, along with people's communication requirement improves and communication environment complicated, high message transmission rate can cause serious multipath interference problem.Multi-carrier modulation technology is a kind of data transmission technology of high speed, orthogonal frequency division multiplexi is as a kind of multi-carrier modulation method wherein, it meets at a high speed simultaneously and overcomes the requirement of disturbing two aspects, whole transmission band is divided into N orthogonal sub-channels, by parallel being modulated on these subcarriers of high speed serialization code of band transmission, this modulation system can effectively improve transmission rate and band efficiency (Han Xiaoyan, OFDM interference mitigation technology research [D], Harbin Engineering University, 2012).

Linear FM signal is a kind of pulse compression signal, and its frequency is in time by linear change within the pulse duration.Linear FM signal itself has certain anti-Doppler frequency shift property, and its ambiguity function has sharp-pointed peak value, is easy to detect judgement (Lv Yanyan, the reliable Study of UWA Communication Technology of chirp FSK [D], Harbin Engineering University, 2010).Chirp signal is usually used in shift keying modulation technology in early days, utilize chirp signal as carrier signal, the data sequence of transmission is modulated in such carrier signal, there is good reliability and anti-fluctuation characteristic, but, its availability of frequency spectrum of this modulation system and traffic rate are all lower, have limited its application and development.

The important topic of signal detection and estimation to the detection of linear FM signal with estimating.Ripe detection technique is included in matched filtering theory and the correlation reception technology (Wang Xudong under maximum signal to noise ratio, studied, Liu Yu. multi-channel self-correlation signal detection algorithm and FPGA thereof realize [J]. Chinese journal of scientific instrument, 2007,28 (5): 875-881; Yao Shanfeng, Yan Hang, Zeng Anjun, etc. the coherent detection performance evaluation [J] of linear FM signal. computer engineering, 2012,38 (1)).The detection that utilizes relevant treatment to realize linear FM signal has been widely used in Active Radar, in Sonar system (Blackman S S.Multiple-target tracking with radar applications[J] .Dedham, MA, Artech House, Inc., 1986,463p., 1986,1).

Correlation detection principle is at system receiving terminal, to the input signal cumulative detection algorithm of being correlated with, less than frequency domain method amount of calculation, do not need to do to received signal piecemeal processing, real-time is better, and relevant cumulative algorithm can accumulating signal energy, to eliminated noise, improve and process signal to noise ratio, cumulative length has determined signal to noise ratio.

Summary of the invention

The object of the present invention is to provide a kind of related detecting method of entire spectrum carrier modulation, entire spectrum carrier modulation technology is that information is modulated in chirp waveform.This modulation signal has stronger anti-Doppler frequency shift property, and its ambiguity function has sharp-pointed peak value, is easy to detect judgement.Separate the relevant cumulative detection algorithm of timing utilization.

The present invention includes entire spectrum carrier modulation system transmitting terminal signal processes and the processing of entire spectrum carrier modulation system receiving terminal signal;

The processing of described entire spectrum carrier modulation system transmitting terminal signal comprises the following steps:

(1) information source produces data message, and this data message is carried out to QPSK sign map;

(2) symbolic information after mapping is modulated in chirp waveform, realizes a kind of modulation system of entire spectrum, by the output after adder stack of the multichannel chirp signal after modulation;

(3) modulation signal after stack is amplified by D/A converter and signal power, finally send in channel;

The processing of described entire spectrum carrier modulation system receiving terminal signal comprises the following steps:

(a) to the signal receiving, amplifier and A/D are converted to and are applicable to the digital signal processed after filtering;

(b) system adopts uncorrelated demodulation method, carrys out additional related Check processing by introducing imaginary part with local signal to received signal, and concrete correlation computations has multiple, and this being correlated with can be isolated each road symbolic information;

(c) isolated each road symbolic information is carried out to symbol de-maps, output bit information.

Preferably, in step (2), the described concrete steps that symbolic information after mapping is modulated in chirp waveform comprise:

1. the frequency band that transmission is used to system, utilizing orthogonal frequency division multiplexi is N sub-frequency bands by channel distribution, the corresponding linear FM signal of every sub-frequency bands, because chirp signal itself has certain frequency sweep broadband, therefore the scan width of chirp signal is set to the interval of sub-band;

2. the symbol after QPSK mapping is { 1+i, 1-i ,-1+i,-1-i}, i is imaginary part, and each symbolic information is modulated in chirp signal waveform, can modulate N road chirp signal waveform simultaneously, obtain the multichannel modulation signal of chirp, the frequency band of whole system uses fully;

In step (2), described by the multichannel chirp signal process adder stack after modulation, be because its scan width of chirp signal producing is sub-band interval, therefore after stack, the frequency spectrum of signal is not overlapping, realizes the transmission means of frequency division multiplexing, improves transmission rate and the availability of frequency spectrum.

Preferably, in step (b), the concrete steps of described demodulation method are as follows:

1. the local signal that receiving terminal produces is the chirp signal in N different frequency interval;

2. by the signal receiving, the chirp signal in 1. does relevantly to step respectively, obtains N correlation, carry out peak value detection, selects energy maximum, can isolate the signal sending on different frequency bands.

Step 2. in, the concrete grammar that described peak value detects can be: by adopting different relevant treatment algorithms, detect two bit informations in two bit informations and the distinct symbols in single symbol simultaneously, in computation complexity allowed band, even can detect the bit information in multiple symbols;

Described different relevant treatment algorithm comprises:

The first is each 2 bit informations that detect in single symbol;

The second is the dibit information at every turn detecting in adjacent two symbols;

The third is each multiple bit informations that detect in multiple symbols.

Beneficial effect of the present invention is as follows:

The invention provides several related detecting methods of entire spectrum carrier modulation, coherent detection based on this chirp signal is that the copy signal of signal of interest and pending signal are done to auto-correlation or cross-correlation, obtain the correlation function of these two groups of signals, in the time there is interested signal in pending signal, in correlation function peak, will have the appearance of relevant peaks, can realize the detection of signal of interest by detecting relevant peaks.At receiving terminal, carry out additional related Check processing by introducing imaginary part with local signal to received signal, different relevant treatment algorithms, can detect two bit informations in two bit informations and the distinct symbols in single symbol simultaneously, in certain computation complexity, even can detect the bit information in multiple symbols.Related detecting method based on entire spectrum carrier modulation proposed by the invention, has algorithm simple, precision advantages of higher.

Brief description of the drawings

Fig. 1 is the system block diagram of several coherent detections of entire spectrum modulating system provided by the invention;

Fig. 2 is the schematic diagram of Whole frequency band modulation provided by the invention;

Fig. 3 is the schematic diagram of Whole frequency band demodulation provided by the invention;

Fig. 4 is correlation detection principle flow chart provided by the invention.

Embodiment

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with concrete enforcement, and with reference to accompanying drawing, the present invention is described in more detail.

The present invention is the related detecting method of considering in entire spectrum carrier modulation, system block diagram as shown in Figure 1, first information source produces data message, after sign map and string conversion, carry out the modulation of chirp entire spectrum, as shown in Figure 2, the thought of simultaneously utilizing orthogonal division multiplexing frequency band to divide, becomes N sub-frequency bands [f by the frequency band division of system to modulated process ₀, f ₁..., f _n-1] f _i(i=0 ..., N-1) and be frequency, sub-band width is the scan width of chirp signal, produces the chirp signal of N different frequency scope, frequency range is [(f ₀, f ₁), (f ₁, f ₂) ..., (f _n-1, f _n)].In a lasting cycle T, the expression formula of chirp signal is:

s(t)＝a(t)cos(2πf ₀t+πkt ²) (1)

The envelope that wherein a (t) is signal, a (t)=0, , f ₀for original frequency; K=B/T is the rate of change of frequency, and B is the bandwidth of chirp signal, and T is pulse duration.The frequency of linear FM signal is linear change f in time _i=f ₀+ kt, the instantaneous frequency of linear FM signal was directly proportional to the time.When frequency k > 0, frequency linearity increases, and is up-chirp signal, k < 0, and frequency linearity reduces, and is down-chirp signal.

Chirp signal has good autocorrelation, its auto-correlation function is formula (2), utilize the characteristic of auto-correlation function and the cross-correlation function of chirp signal, up-chirp signal and the positive negative indication of down-chirp signal combination can be used for representing different symbolic information.

Can find out, in the time of t=0, envelope obtain amplitude peak value much larger than cross correlation value now; In the time of t ≈ ± 1/B, envelope value be zero, and along with the increase of chirp signal bandwidth B, sidelobe level reduces.

Transmitting terminal is by data bit stream process QPSK sign map to be sent, x _i∈ 1+i, and 1-i ,-1+i ,-1-i}, represents respectively real part and the imaginary part information of symbol with up-chirp and down-chirp, in the time that real part is 1, select up-chirp signal; Real part is-1 o'clock, selects negative up-chirp signal; In the time that imaginary part is 1, down-chirp signal; In the time that imaginary part is-1, select negative down-chirp signal, can represent like this symbolic information of mapping with chirp signal:

$\left\{\begin{array}{cc}1+i\&RightArrow;[\mathrm{up}-\mathrm{chirp}& \mathrm{down}-\mathrm{chirp}\\ 1-i\&RightArrow;[\mathrm{up}-\mathrm{chirp}& -1*\mathrm{down}-\mathrm{chirp}\\ -1+i\&RightArrow;[-1*\mathrm{up}-\mathrm{chirp}& \mathrm{down}-\mathrm{chirp}\\ -1-i\&RightArrow;[-1*u[-\mathrm{chirp}& -1\mathrm{down}-\mathrm{chirp}\end{array}\right.---\left(3\right)$

The chirp signal waveform of N way frequency band is superposeed by adder, realized the modulation of frequency division multiplexing, finally the waveform after stack is sent in wireless channel, the signal indication of system transmission is:

$S_{\mathrm{chirp}}=\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\cos \left(2\mathrm{\&pi;}(f_{i}t+\frac{k}{2}{t}^2)\right)g_T\left(t\right)---\left(4\right)$

In the signal processing of transmitting terminal, utilize entire spectrum modulation system (by the whole frequency range modulate transmitted information of chirp signal), simultaneously in conjunction with traditional OFDM thought, by output after the stack of multichannel modulation signal, can improve the transmission rate of system, also overcome the shortcoming that conventional orthogonal frequency division multiplexing midband does not make full use of.

At receiving terminal, signal amplifies after filtering, after analog-to-digital conversion, carry out irrelevant demodulation, the detailed process of demodulation as shown in Figure 3, is carried out matched filtering by the signal receiving and N road chirp local signal, because linear FM signal is a kind of signal with sharp-pointed energy peak, through coherent detection, can realize the separation of information, reduce error probability.Coherent detection is a kind of detection method of time-domain information, is mainly signal and noise are done to the different statistical properties that correlation analysis utilizes signal and noise to have, and by auto-correlation and computing cross-correlation, reaches the object that suppresses noise, detection signal.Cross-correlation function has been described the dependence between two groups of signals, is expressed as:

Work as s ₁(t)=s (t)+n (t) is the signal after being polluted by Gaussian noise, s ₂(t) be local signal, ask s ₁and s (t) ₂(t) cross-correlation function, because s (t) is incoherent mutually with n (t), , therefore can be by judging whether to occur that the s (t) that relevant peaks realizes signal detects.This detection algorithm has utilized the feature of signal correlation and noise randomness, realizes and suppresses noise, the object of detection signal.

The signals step of utilizing this uncorrelated demodulation process to receive:

The first step: produce local replica signal as the formula (7):

c ₁＝[up-chirp down-chirp]

c ₂＝[up-chirp -1*down-chirp] (7)

c ₃＝[-1*up-chirp down-chirp]

c ₄＝[-1*up-chirp -1*down-chirp]

Second step: modulation signal is after the first step is processed, and receiving terminal can detect two bit informations in two bit informations and the distinct symbols in single symbol simultaneously, in certain computation complexity, even can detect the bit information in multiple symbols:

1,, in the time of 2 bit information in the single symbol of each detection, the local signal of generation as the formula (7), then does integral processing by reception signal and local signal and produces judgment variables, as the formula (8);

2, in the time of 2 bit information in each detection adjacent-symbol, processing method is by the processing that carries out related calculation of the real part modulation chirp signal of the real part modulation chirp signal of previous symbol and a rear symbol simultaneously, produce judgment variables, as the formula (8), the modulation signal demodulation of imaginary part is also to do similar processing, this processing mode can reduce the impact that multipath disturbs, and reduces bit error rate performance;

3, in the time of bit information in the multiple symbols of each detection, increase the length of related operation, auto-correlation and the cross correlation value of signal are widely different, are easy to peak value and detect.

The local signal integration of the signal receiving and generation is produced to judgment variables

$u_i=\underset{0}{\overset{T}{\&Integral;}}{c}_i\left(t\right)r\left(t\right)\mathrm{dt}---\left(8\right)$

Wherein c _i(t), i=1,2,3,4 is the signal of formula (7), after judgement, selects peak value maximum, demodulates symbolic information, then passes through demapping, output bit information.

Fig. 4 is the flow chart of system coherent detection, after system initialization, utilize matched filtering method to separate the chirp signal of different frequency range, wherein the generation of local signal is as shown in table 1, be respectively: detect the dibit information in single symbol simultaneously, detect the dibit information in adjacent-symbol simultaneously and detect the multiple bit informations in multiple symbols simultaneously.Then, each chirp signal is carried out to coherent detection, obtain integration variable, through judgement, obtain the estimation of transmitted signal.

The local signal of the different detection algorithms of table 1 produces

In the present invention, by produce the copy signal of linear FM signal at receiving terminal, in the time of relevant adding up, we have proposed several processing methods, and the first is each 2 bit informations that detect in single symbol; The second is the dibit information at every turn detecting in adjacent two symbols, and the third is each multiple bit informations that detect in multiple symbols, by increasing relevant length when cumulative, strengthens correlation peak, improves and detects performance.

The entire spectrum carrier modulation technology that the present invention uses, the thought of utilizing orthogonal division multiplexing frequency band to divide, with the waveform transmission information of chirp signal, overcome the shortcoming that traditional orthogonal FDM communication system intermediate frequency spectrum does not make full use of, improve the reliability of system, by output after the multichannel modulation signal stack of transmitting terminal, save the transmission time, improve the availability of frequency spectrum.

The above; only for preferably embodiment of the present invention, but protection scope of the present invention is not limited to this, is anyly familiar with in technical scope that those skilled in the art disclose in the present invention; the variation that can expect easily or replacement, within all should being encompassed in protection scope of the present invention.

Claims (5)

1. the related detecting method of entire spectrum carrier modulation, is characterized in that comprising the processing of entire spectrum carrier modulation system transmitting terminal signal and the processing of entire spectrum carrier modulation system receiving terminal signal;

The processing of described entire spectrum carrier modulation system transmitting terminal signal comprises the following steps:

(1) information source produces data message, and this data message is carried out to QPSK sign map;

(2) symbolic information after mapping is modulated in chirp waveform, realizes a kind of modulation system of entire spectrum, by the output after adder stack of the multichannel chirp signal after modulation;

(3) modulation signal after stack is amplified by D/A converter and signal power, finally send in channel;

The processing of described entire spectrum carrier modulation system receiving terminal signal comprises the following steps:

(a) to the signal receiving, amplifier and A/D are converted to and are applicable to the digital signal processed after filtering;

(b) system adopts uncorrelated demodulation method, carrys out additional related Check processing by introducing imaginary part with local signal to received signal, and concrete correlation computations has multiple, and this being correlated with can be isolated each road symbolic information;

(c) isolated each road symbolic information is carried out to symbol de-maps, output bit information.

2. the related detecting method of entire spectrum carrier modulation as claimed in claim 1, is characterized in that in step (2), and the described concrete steps that symbolic information after mapping is modulated in chirp waveform comprise:

1. the frequency band that transmission is used to system, utilizing orthogonal frequency division multiplexi is N sub-frequency bands by channel distribution, the corresponding linear FM signal of every sub-frequency bands, because chirp signal itself has certain frequency sweep broadband, therefore the scan width of chirp signal is set to the interval of sub-band;

2. the symbol after QPSK mapping is { 1+i, 1-i ,-1+i,-1-i}, i is imaginary part, and each symbolic information is modulated in chirp signal waveform, can modulate N road chirp signal waveform simultaneously, obtain the multichannel modulation signal of chirp, the frequency band of whole system uses fully.

3. the related detecting method of entire spectrum carrier modulation as claimed in claim 1, is characterized in that the concrete steps of described demodulation method are as follows in step (b):

1. the local signal that receiving terminal produces is the chirp signal in N different frequency interval;

2. by the signal receiving, the chirp signal in 1. does relevantly to step respectively, obtains N correlation, carry out peak value detection, selects energy maximum, can isolate the signal sending on different frequency bands.

4. the related detecting method of entire spectrum carrier modulation as claimed in claim 3, it is characterized in that step 2. in, the concrete grammar that described peak value detects is: by adopting different relevant treatment algorithms, detect two bit informations in two bit informations and the distinct symbols in single symbol simultaneously, in computation complexity allowed band, even can detect the bit information in multiple symbols.

5. the related detecting method of entire spectrum carrier modulation as claimed in claim 4, is characterized in that described different relevant treatment algorithm comprises:

The first is each 2 bit informations that detect in single symbol;

The second is the dibit information at every turn detecting in adjacent two symbols;

The third is each multiple bit informations that detect in multiple symbols.