CN103888404A - Full frequency spectrum carrier modulation method based on frequency spectrum shift - Google Patents

Abstract

The invention discloses a full frequency spectrum carrier modulation method based on frequency spectrum shift, and relates to wireless communication. The full frequency spectrum carrier modulation method comprises the steps of transmitting end signal processing and receiving end signal processing. According to the step of transmitting end signal processing, an information source generates data information, and QPSK symbol mapping is conducted on the data information; chirp full frequency spectrum modulation is conducted on the mapped information, and the transmitted information is changed into the chirp signal waveform through the modulation method, and is shifted to N frequency points; chirp modulation signals at the different frequency points are superposed through an adder and then are output; the superposed modulated signals are converted by a D/A converter and processed through signal power amplification, and then are transmitted to a channel. According to the step of receiving end signal processing, the received signals are processed by a filter amplifier and converted in an A/D conversation mode to obtain digital signals suitable for being processed; an uncorrelated demodulation method is adopted in the system, a group of local signals are generated at the receiving end to conduct matched filtering on the received signals, and various paths of symbol information is separated; symbol demapping is conducted on the separated information, and bit information is output.

Description

A kind of entire spectrum carrier modulating method based on frequency spectrum shift

Technical field

The present invention relates to radio communication, particularly relate to a kind of entire spectrum carrier modulating method based on frequency spectrum shift.

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.Afterwards, document (LeBlanc L R, Beaujean P P.Multi-frequency shift key and differential phase shift key for acoustic modem[C] //Autonomous Underwater Vehicle Technology, 1996.AUV'96., Proceedings of the1996Symposium on.IEEE, 1996:160-166), propose the output that superposes of the chirp shift keying modulation signal of multichannel, can save the transmission time, improve transmission rate, but, this modulation system does not utilize full range to bring transmission information fully yet, just utilize some frequency in frequency band, a lot of frequency spectrum resources are wasted.An entire spectrum modulation technique based on frequency spectrum shift, the thought of utilizing orthogonal division multiplexing frequency band to divide, with the waveform transmission information of chirp signal, chirp signal after modulation is moved on different frequencies, the stack of multichannel modulation signal, has saved the transmission time, has improved the availability of frequency spectrum.

Summary of the invention

Transmission band is divided into N sub-frequency bands by providing of the object of the invention is to, produce the chirp signal in N identical frequency sweep interval, its frequency sweep bandwidth is sub-band interval, transmission information is modulated in chirp signal simultaneously, overcome the shortcoming that conventional orthogonal frequency division multiplexing modulation technique midband does not utilize completely, chirp signal after modulation is moved on N sub-frequency, after multiple signals stack, exported, improve a kind of entire spectrum carrier modulating method based on frequency spectrum shift of band efficiency.

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

The processing of described entire spectrum modulation 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) information meeting after mapping is carried out to the modulation of chirp entire spectrum, the information exchange of transmission is crossed to this modulator approach and be transformed into chirp signal waveform, and move on N frequency;

(3) by the output after adder stack of the chirp modulation signal on different frequent points;

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

The processing of described entire spectrum modulation receiving end 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, produces one group of corresponding local signal the signal receiving is carried out to matched filtering at receiving terminal, isolates each road symbolic information;

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

Preferably, in step (2), the concrete steps of described chirp entire spectrum modulation comprise:

1. the frequency band that transmission is used to system, utilizing orthogonal frequency division multiplexi is N sub-frequency bands by channel distribution, meanwhile, produces a chirp swept-frequency signal with sub-band width;

2. the symbol after QPSK mapping is { 1+i, 1-i,-1+i,-1-i}, convert each symbolic information to chirp signal waveform, can produce N chirp signal waveform simultaneously, the signal of generation is moved on step each frequency in 1., obtain the multicarrier modulated signal of chirp, used the frequency band of whole system.

In step (3), described by the chirp modulation signal process adder stack on different frequent points, because its scan width of chirp signal producing is sub-band interval, therefore after stack, the frequency spectrum of signal is not overlapping, realize the transmission means of frequency division multiplexing, improve transmission rate and the availability of frequency spectrum.

Preferably, in step (b), described demodulation can be carried out demodulation according to chirp multi-carrier modulation, specifically comprises the following steps:

1. first the receiving terminal of entire spectrum modulating system does the processing of correlation demodulation to signal, isolates N chirp signal waveform;

2. the local signal producing is a chirp signal in minimum sub-band interval;

3. by step 1. in an isolated N signal and the step local signal in 2. do to mate coherent detection; Described coupling coherent detection can adopt the chirp signal waveform of two bit informations to detect simultaneously, detects performance and improves.

Beneficial effect of the present invention is as follows:

The invention provides a kind of entire spectrum carrier modulating method based on frequency spectrum shift, transmission band is divided into N sub-frequency bands, the frequency sweep interval of N chirp signal is sub-band width, transmission information is modulated in chirp signal simultaneously, overcome the shortcoming that conventional orthogonal frequency division multiplexing modulation technique midband does not utilize completely, by output after multiple signals stack, improve band efficiency.Emulation under multipath and Gaussian white noise channel, as can be seen from Figure 4, the method proposing also can be worked under low signal-to-noise ratio, and signal to noise ratio is in the time of-20dB, and the error rate is 0.0019, and the reliability of system is very high.

Brief description of the drawings

Fig. 1 is the system block diagram of the Whole frequency band modulating system based on frequency spectrum shift provided by the invention;

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

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

Fig. 4 is the entire spectrum modulating system BER performance based on frequency spectrum shift provided by the invention.

Embodiment

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the invention will be further described.

The present invention considers an entire spectrum carrier modulating method based on frequency spectrum shift, 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 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), sub-band width is the scan width of chirp signal, produces the chirp signal of N same frequency range, frequency range is (f ₀, f ₁).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 is the rate of change of frequency, and when 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.

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

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

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 transmitting terminal signal processing, utilize entire spectrum modulation system (by the whole frequency range modulate transmitted information of chirp signal), simultaneously in conjunction with traditional OFDM thought, 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, first chirp modulation signal is carried out moving under frequency spectrum, utilize irrelevant demodulation, concrete demodulating process as shown in Figure 3, by the signal after frequency spectrum shift respectively with the signal multiplication of formula (6), carry out matched filtering processing.

$\left\{\begin{array}{cc}{\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="HDA0000489363220000013.png,HDA0000489363220000021.png"\; state="\{\{state\}\}">c</figure-callout>}}_1=[\mathrm{up}-\mathrm{chirp}& \mathrm{down}-\mathrm{chirp}]\\ c_2=[\mathrm{up}-\mathrm{chirp}& -1*\mathrm{down}-\mathrm{chirp}]\\ c_3=[-1*\mathrm{up}-\mathrm{chirp}& \mathrm{down}-\mathrm{chirp}]\\ c_4=[-1*\mathrm{up}-\mathrm{chirp}& -1*\mathrm{down}-\mathrm{chirp}]\end{array}\right.---\left(6\right)$

Integration produces judgment variables

$u_i=\underset{0}{\overset{T}{\&Integral;}}{c}_i\left(t\right)r\left(t\right)\mathrm{dt}---\left(7\right)$

Wherein c _i(t), i=1,2,3,4 is the signal of formula (6), can output symbol after judgement, then pass through demapping, output bit information.

Entire spectrum modulating system based on chirp frequency spectrum shift has carried out emulation under multipath channel, and as shown in Figure 4, under low signal-to-noise ratio, the BER performance of system is also fine for simulation result, in signal to noise ratio be-when 20dB, the error rate is 10 ^-3the order of magnitude.

Claims (3)

1. the entire spectrum carrier modulating method based on frequency spectrum shift, is characterized in that comprising that entire spectrum modulation transmitting terminal signal is processed and the processing of entire spectrum modulation receiving end signal;

The processing of described entire spectrum modulation 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) information meeting after mapping is carried out to the modulation of chirp entire spectrum, the information exchange of transmission is crossed to this modulator approach and be transformed into chirp signal waveform, and move on N frequency;

(3) by the output after adder stack of the chirp modulation signal on different frequent points;

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

The processing of described entire spectrum modulation receiving end 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, produces one group of corresponding local signal the signal receiving is carried out to matched filtering at receiving terminal, isolates each road symbolic information;

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

2. a kind of entire spectrum carrier modulating method based on frequency spectrum shift as claimed in claim 1, is characterized in that in step (2), and the concrete steps of described chirp entire spectrum modulation comprise:

1. the frequency band that transmission is used to system, utilizing orthogonal frequency division multiplexi is N sub-frequency bands by channel distribution, meanwhile, produces a chirp swept-frequency signal with sub-band width;

2. the symbol after QPSK mapping is { 1+i, 1-i,-1+i,-1-i}, convert each symbolic information to chirp signal waveform, produce N chirp signal waveform simultaneously, the signal of generation is moved on step each frequency in 1., obtain the multicarrier modulated signal of chirp, used the frequency band of whole system.

3. a kind of entire spectrum carrier modulating method based on frequency spectrum shift as claimed in claim 1, is characterized in that described demodulation is carried out demodulation according to chirp multi-carrier modulation, specifically comprises the following steps in step (b):

1. first the receiving terminal of entire spectrum modulating system does the processing of correlation demodulation to signal, isolates N chirp signal waveform;

2. the local signal producing is a chirp signal in minimum sub-band interval;

3. by step 1. in an isolated N signal and the step local signal in 2. do to mate coherent detection; Described coupling coherent detection adopts the chirp signal waveform of two bit informations to detect simultaneously, detects performance and improves.

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