CN1292573C - Modulation demodulation method of anticarrier restoring deviation - Google Patents

Abstract

The present invention relates to a modulation demodulation method of anti-carrier wave recovering deviation, which is characterized in that the modulation method uses a sine wave with different selections and different frequencies of data bits to be transmitted as output to generate signals with stable second-order period characteristics. After the received signals with the characteristics are processed by the carrier wave demodulation method of the present invention, the autocorrelation function value of the signals after the carrier wave demodulation is calculated, the obtained autocorrelation function value is processed by the relevant period spectral treatment, and then, the obtained autocorrelation function value is processed by data demodulation according to a relevant period spectral value. The modulation demodulation method of the present invention has good receptivity when a carrier wave recovery error exists at a receiving end to cause demodulation results can not be influenced by the carrier wave recovery error.

Description

A kind of anti-carrier wave recovers the modulation-demo-demodulation method of deviation

Technical field:

The present invention relates to the modulation-demodulation technique field in the radio communication.

Background technology:

Fig. 4-92 that " digital mobile communication " that the People's Telecon Publishing House publishes is the 211st page points out, if there is carrier frequency offset in carrier wave in recovering, be that the carrier frequency that receiver local carrier frequency and transmitter are sent here has deviation, to cause the error rate of receiver demodulating data to raise, and cause the letter of whole system sharply to descend.

Influencing the accurate principal element of recovering of carrier wave is difference, channel fading and the Doppler frequency shift etc. of transmit leg and recipient's oscillator.6-2-54 formula that " digital communication " that the Electronic Industry Press publishes is the 355th page and 358 pages 6-2-59 formula are pointed out, if follow the tracks of synchronously at the carrier wave that the recipient adopts Phase Lock Technique that transmit leg is sent here, attempt to make local carrier on the frequency with phase place on consistent with it, because interference of noise and some other factor, there is the problem on the precision in this method, can not accomplish in full accordly, deviation is always arranged.

Technology contents:

The present invention proposes a kind of signal modulation/demodulation method that recovers deviation in communication system at anti-carrier wave, so that still have good receptivity when receiving terminal exists carrier wave to recover error.

Anti-carrier wave of the present invention recovers the signal modulation/demodulation method of deviation, and its modulation comprises oscillator, frequency selector, filter and carrier modulator; The output of frequency selector 3 connects the input of filter 4, the input of wave modulator 5 is carried in the output of filter 4, the output of oscillator 1 and oscillator 2 connects the input of frequency selector 3, described frequency selector 3 is selected the output of the output signal of oscillator 1 as frequency selector 3 when data bit waiting for transmission is 0; When data bit waiting for transmission was 1, the output signal of selecting oscillator 2 was as output; With the receiving signal demodulation method of the corresponding anti-carrier wave recovery deviation of above-mentioned signal modulating method, comprise that carrier wave demodulation device 6, filter 7, autocorrelator 8, associated period spectrum processor 9, associated period spectrum processor 10, signal compare and data decision device 11; The output of carrier wave demodulation device 6 connects the input of filter 7, it is characterized in that: the output of filter 7 connects the input of autocorrelator 8, the output of autocorrelator 8 connects the input of associated period spectrum processor 9 and associated period spectrum processor 10 respectively, associated period spectrum processor 9 and 10 pairs of input signals of associated period spectrum processor are made the associated period spectrum and are handled, their output connect signal relatively with the input of data decision device 11,11 pairs of inputs of signal comparison and data decision device data are carried out data demodulates and are handled the back and export restituted signal;

Described autocorrelator 8 is according to formula:

R _s(t，τ)＝s(t)*s ^*(t+τ) (1)

Write the auto-correlation function value R of the signal of function calculation input at τ=0 place _s(t, τ), t is the relevant initial moment in the formula (1), τ is a related interval, the signal that s (t) expression receives, s ^*(t) conjugate function of expression s (t);

Described associated period spectrum processor 9 is according to formula:

$R_s^{\mathrm{\α}}\left(0\right)=\frac{1}{T_0}{\∫}_0^{T_0}{R}_s(t,0)e^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(2\right)$

Write function, find the solution (π * T in α=1/ ₀) going up the associated period spectrum value of input signal, in the formula (2), α is the signal period frequency values, T ₀Be signal correction period of a function, R _s ^α(0) o'clock be the associated period spectrum value at α place for τ=0 at period frequency;

Described associated period spectrum processor 10 is write function according to formula (2), finds the solution (the π * T in α=1/ ₁) go up the associated period spectrum value of input signal, in the formula, T ₁Be the signal correction period of a function:

Described signal relatively with data decision device 11 at the absolute value of the numerical value of associated period spectrum processor 9 inputs during greater than the absolute value of the numerical value of associated period spectrum processor 10 inputs, the demodulating data of output is a bit 0; Otherwise the demodulating data of output is a bit 1.

Demodulation among the present invention at the principle of modulator approach foundation be:

Because it is ω that data bit 0 is mapped as a band frequency ₀Sine wave, it is ω that data bit 1 is mapped as a band frequency ₁Sine wave, the baseband signal s that obtains like this (t) can be represented by following formula:

$s\left(t\right)=\underset{n=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}\cos \left({\mathrm{\ω}}_{a_n}t\right)[u(t-n{T}_d)-u(t-n{T}_d-T_d)]---\left(3\right)$

α _nValue is the data bit before the 0/1 expression modulation, T _dBe cycle data, $T_d>>2\mathrm{\π}/{\mathrm{\ω}}_{a_n},$ U (t) represents step function;

Then as 0≤τ≤T _dThe time s (t) auto-correlation function R _s(t, τ):

$R_s(t,\mathrm{\τ})=1/2[\cos \left({\mathrm{\ω}}_{a_n}\mathrm{\τ}\right)+\cos (2{\mathrm{\ω}}_{a_n}t-{\mathrm{\ω}}_{a_n}\mathrm{\τ})]---\left(4\right)$

Order $T_{a_n}=\mathrm{\π}/{\mathrm{\ω}}_{a_n},$ Then:

$R_s(t+T_{a_n},\mathrm{\τ})=1/2[\cos \left({\mathrm{\ω}}_{a_n}\mathrm{\τ}\right)+\cos (2{\mathrm{\ω}}_{a_n}(t+T_{a_n})-{\mathrm{\ω}}_{a_n}\mathrm{\τ})]$

$=1/2[\cos \left({\mathrm{\ω}}_{a_n}\mathrm{\τ}\right)+\cos (2{\mathrm{\ω}}_{a_n}t-{\mathrm{\ω}}_{a_n}\mathrm{\τ}+2\mathrm{\π})]---\left(5\right)$

$=R_s(t,\mathrm{\τ})$

So s (t) has second order cyclic stationary characteristic.The associated period spectral function that can be got s (t) by formula (5) is:

$R_s^{\mathrm{\α}}\left(\mathrm{\τ}\right)=1/T\underset{-T/2}{\overset{+T/2}{\∫}}1/2[\cos \left({\mathrm{\ω}}_{a_n}\mathrm{\τ}\right)+\cos (2{\mathrm{\ω}}_{a_n}t-{\mathrm{\ω}}_{a_n}\mathrm{\τ})]e^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(6\right)$

If get α=ω _k/ π (k=0 or 1), then (6) formula becomes:

$R_s^{\mathrm{\α}}\left(\mathrm{\τ}\right)=1/T\underset{-T/2}{\overset{+T/2}{\∫}}1/2\cos (2{\mathrm{\ω}}_{a_n}t-{\mathrm{\ω}}_{a_n}\mathrm{\τ})e^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(7\right)$

Only as k=α _nThe time following formula just non-vanishing, so s (t) has two period frequency α _k=ω _k/ π (k=0 or 1).When sending data bit 0, the period frequency of s (t) is α ₀=ω ₀/ π.Otherwise the period frequency of s (t) is α ₁=ω ₁/ π.The signal of modulation generation has the characteristic of second order cyclic stationary like this.

The principle of signal demodulating method foundation of the present invention is:

Because the baseband signal s (t) that transmitter sends is a second order cyclic stationary signal, if receiver exists carrier wave to recover error, error amount is ω _e, do not consider channel disturbance, then the baseband signal s after the reception carrier demodulation _r(t) can be expressed as s (t) e ^{J ω et}, handle through correlator and cyclic spectrum again, can get s _r(t) associated period spectral function is:

$R_{s_r}^{\mathrm{\α}}\left(\mathrm{\τ}\right)=\frac{1}{T}\underset{-T/2}{\overset{T/2}{\∫}}E\left\{s\left(t\right)s^{*}(t-\mathrm{\τ})\right\}{e}^{j{\mathrm{\ω}}_e\mathrm{\τ}}{e}^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(8\right)$

α represents the period frequency of s (t) in the following formula.If get τ=0, then following formula becomes:

$R_{s_r}^{\mathrm{\α}}\left(0\right)=\frac{1}{T}\underset{-T/2}{\overset{T/2}{\∫}}E\left\{s\left(t\right)s^{*}\left(t\right)\right\}{e}^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(9\right)$

So ω _eResult to formula (9) does not produce any influence.If the data bit 0/1 that sends has different period frequency α respectively simultaneously ₀/ α ₁, promptly when sending data bit 0, s (t) has period frequency α ₀Second order cyclic stationary signal; When sending data bit 1, s (t) has period frequency α ₁Second order cyclic stationary signal.Then when transmitter sends data bit 0, if get α=α ₀Calculate (9) formula, (9) formula value non-zero then is if get α=α ₁Calculate (9) formula, then (9) formula value is zero.When should transmitter sending data bit 1, if get α=α ₀Calculate (9) formula, then (9) formula value is zero, if get α=α ₁Calculate (9) formula, then (9) formula value non-zero.So receiver is by calculating respectively at period frequency α ₀/ α ₁The associated period spectral function value of the baseband signal that the place receives, and make relatively judgement accordingly, with regard to the data that demodulate that can be correct.

Compared with prior art and since among the present invention demodulation institute at modulator approach select different frequency according to data bit waiting for transmission sine wave as output, the signal that has second order cyclic stationary characteristic in the transmitting terminal generation; After demodulation method of the present invention was made carrier wave demodulation to the signal with These characteristics that is received, the auto-correlation function value of signal behind the calculating carrier wave demodulation was made the associated period spectrum to the auto-correlation function value that obtains and is handled, and finds the solution auto-correlation function at α ₀=ω ₀/ π and α ₁=ω ₁The associated period spectrum value at/π place is made the data demodulation process according to associated period spectrum value then, by the order of magnitude of two associated period spectrum values relatively obtained demodulating data.This modulation-demo-demodulation method of the present invention is because the judgement foundation of utilizing signal correction cyclic spectrum value to handle as data demodulates, overcome the shortcoming that the prior art demodulation result worsens along with the increase of carrier wave recovery error, when receiving terminal exists carrier wave to recover error, still have good receptivity, make demodulation result not be subjected to carrier wave to recover the influence of error.

Description of drawings:

Fig. 1 is a signal modulating method block diagram of the present invention;

Fig. 2 is a receiving demodulation method block diagram of the present invention;

When Fig. 3 is a signal to noise ratio=16dB, be 0Hz during to 200Hz in the carrier wave error, the ber curve figure of the ber curve of DFM and matched filter;

When Fig. 4 is a signal to noise ratio=16dB, be the ber curve of 200Hz DFM during and the ber curve figure of matched filter to 20000Hz in the carrier wave error.

Embodiment:

Below in conjunction with accompanying drawing the present invention is done further specific descriptions.

Embodiment 1:

Specific embodiments of the invention comprise the signal demodulating method shown in signal modulating method shown in the accompanying drawing 1 and the accompanying drawing 2.

This signal modulating method comprises: the frequency that oscillator 1 is produced is ω ₀=2 π/T ₀Sine wave and the frequency that produces of oscillator 2 be ω ₁=2 π/T ₁Sine wave, simultaneously the incoming frequency selector 3, the gating switch of frequency selector 3 is controlled by data bit to be sent, if data bit to be sent is 0, then to select frequencies be ω to frequency selector 3 ₀Sine wave as output; Otherwise the selection frequency is ω ₁Sine wave as output, the signal of frequency selector 3 output has second order cyclic stationary characteristic like this.The output input filter 4 of frequency selector 3 then, after carrier wave was gone up in output incoming carrier modulator 5 modulation of filter 4, the output of carrier modulator 5 was exactly signal to be sent.

Making oscillator 1 produce frequency in the present embodiment is the sine wave of 320kHz, it is the sine wave of 400kHz that oscillator 2 produces frequency, the speed of the data bit to be sent of the gating switch of control frequency selector 3 is 20kHz, filter 4 is an all-pass filter, and modulated carrier frequency is 2GHz in the carrier modulator 5.

Corresponding signal demodulating method comprises: carrier wave demodulation device 6 is input to filter 7 with the signal that antenna receives through behind the carrier wave demodulation, filter 7 outputs have the auto-correlation function that carrier wave recovers baseband signal input autocorrelator 8 signal calculated of error, the output of autocorrelator 8 is input to associated period spectrum processor 9 and 10 respectively, calculates at α respectively ₀=ω ₀The associated period spectrum value of/π signal and at α ₁=ω ₁The associated period spectrum value of/π signal, associated period spectrum processor 9 and 10 output be input to respectively signal relatively with data decision device 11 in, when the absolute value of the input value of associated period spectrum processor 9 during greater than the absolute value of the input value of associated period spectrum processor 10, then the signal comparison is a bit 0 with the demodulating data of data decision device 11 outputs; If the absolute value of the input value of associated period spectrum processor 9 is during less than the absolute value of the input value of associated period spectrum processor 10, then the signal comparison is a bit 1 with the demodulating data of data decision device 11 outputs.

In the present embodiment, if the carrier wave error is 0-20000Hz, i.e. the local carrier frequency of carrier wave demodulation device 6 uses is in the 2-2.00002GHz scope, and associated period is composed the α in the processor 9 ₀=640000, the α in the associated period spectrum processor 9 ₁=800000.

Accompanying drawing 3 has provided at signal to noise ratio=16dB, when the carrier wave error is 0-200Hz, the demodulation bit error rate computer artificial result of DFM method, reach the error rate calculation machine simulation result of matched filter method of reseptance traditional under the equal conditions, curve b among the figure represents the ber curve of DFM method, and curve a represents the ber curve of matched filter method of reseptance.As shown in Figure 3: when the carrier wave error was 0-3Hz, matched filter method of reseptance performance was better than the DFM method; But when the carrier wave error was 4-200Hz, then DFM method performance obviously was better than the matched filter method of reseptance.

Accompanying drawing 4 is illustrated in signal to noise ratio=16dB, when the carrier wave error is 200-20000Hz, the demodulation bit error rate computer artificial result of DFM method, reach the error rate calculation machine simulation result of matched filter method of reseptance traditional under the equal conditions, curve d among the figure represents the ber curve of DFM method, and curve c represents the ber curve of matched filter method of reseptance.When the carrier wave error was 200-20000Hz, DFM method performance obviously was better than the matched filter method of reseptance.

In summary, the signal that the present invention modulates generation has second order cyclic stationary characteristic, and the carrier wave demodulation error is to not influence of receptivity.

Claims (1)

1, a kind of anti-carrier wave recovers the signal modulation/demodulation method of deviation, and its modulation comprises oscillator, frequency selector, filter and carrier modulator; The output of frequency selector (3) connects the input of filter (4), the input of wave modulator (5) is carried in the output of filter (4), the output of oscillator (1) and oscillator (2) connects the input of frequency selector (3), described frequency selector (3) is selected the output of the output signal of oscillator (1) as frequency selector (3) when data bit waiting for transmission is 0; When data bit waiting for transmission was (1), the output signal of selecting oscillator (2) was as output; Receiving signal demodulation method with the corresponding anti-carrier wave recovery deviation of above-mentioned modulator approach, comprise carrier wave demodulation device (6), filter (7), autocorrelator (8), associated period spectrum processor (9), associated period spectrum processor (10), signal compares and data decision device (11), the output of carrier wave demodulation device (6) connects the input of filter (7), it is characterized in that: the output of filter (7) connects the input of autocorrelator (8), the output of autocorrelator (8) connects the input of associated period spectrum processor (9) and associated period spectrum processor (10) respectively, associated period spectrum processor (9) and associated period spectrum processor (10) are made the associated period spectrum to input signal and are handled, their output connect signal relatively with the input of data decision device (1) 1, signal relatively carries out data demodulates with data decision device (11) to the input data and handles back output restituted signal;

Described autocorrelator 8 is according to formula:

R _s(t，τ)＝s(t)*s ^*(t+τ) (1)

Write the auto-correlation function value R of the signal of function calculation input at τ=0 place _s(t, τ), t is the relevant initial moment in the formula (1), τ is a related interval, the signal that s (t) expression receives, s ^*(t) conjugate function of expression s (t);

Described associated period spectrum processor (9) is according to formula:

$R_s^{\mathrm{\α}}\left(0\right)=\frac{1}{T_0}{\∫}_0^{T_0}{R}_s(t,0)e^{-j2\mathrm{\π\αt}}\mathrm{dt}---\left(2\right)$

Write function, find the solution (π * T in α=1/ ₀) going up the associated period spectrum value of input signal, in the formula (2), α is the signal period frequency values, T ₀Be signal correction period of a function, R _s ^α(0) o'clock be the associated period spectrum value at α place for τ=0 at period frequency;

Described associated period spectrum processor (10) is write function according to formula (2), finds the solution (the π * T in α=1/ ₁) go up the associated period spectrum value of input signal, in the formula, T ₁Be the signal correction period of a function;

Described signal relatively with data decision device (11) when the absolute value of the numerical value of associated period spectrum processor 9 inputs is composed the absolute value of numerical value of processor (10) input greater than associated period, the demodulating data of output is a bit 0; Otherwise the demodulating data of output is a bit 1.

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