CN1588932A - Information modulation and demodulation method of constant amplitude high frequency band utilizing rate - Google Patents

Abstract

A method for modulating and demodulating information of equivalent amplitude high frequency band usage utilizes binary information symbols to directly change the waveform of a sine carrier wave to minimize the waveform difference between the modulated signal corresponding to logic 'D' go (t) and g1(t) corresponding to logic '1' and the sine signals and only one parameter is used to control the waveform difference and signal bandwidth. Since in the process of zero-cross detection to the information demodulation, only one sample judgment is needed at the middle of the received signal waveform (t=T/2) to finish the demodulation and hard limitation is applied to suppress interference of pulse noise.

Description

The information modulation and demodulation method of the operating factor of highband of constant amplitude

Technical field

The present invention is a kind of information modulation and demodulation method that is used for digital communication, belongs to the technical field of digital information transmission.

Background technology

In the digital communication system, the process of the baseband signal of representing binary data upwards being moved given transmission frequency range is called modulation, and opposite process then is referred to as demodulation.In order to reach high as far as possible band efficiency, promptly in the unit frequency band, transmit higher numeric code rate (is dimension with bps/Hz), we are at patent application " the information modulator approach of operating factor of highband " (application number: 03152978.X), proposed the efficient modulation system of a kind of being called " minimum waveform difference keying " (being abbreviated as VWDK), its invention key is to make the modulated signal g of representative " 0 " ₀(t) and the representative " 1 " modulated signal g ₁(t) all and the different wave shape minimum between the sinusoidal signal, shown in Fig. 1 (a).The implication that Here it is " minimum waveform difference ".Obviously, the transmission code rate of VWDK is the frequency of signal waveform.

But, the amplitude difference of two halves before and after the VWDK waveform of Fig. 1 (a), that is to say, the modulator approach that this patent application is invented has been introduced amplitude modulation(PAM), communication system is for fear of clipping distortion, bigger dynamic range will be arranged,, will influence its demodulation performance in some amplitude occasions with limited.And its power spectrum is not difficult to find out that wherein the amplitude of high order harmonic component (i.e. line spectrum among the figure) is still higher shown in Fig. 2 (a), and this had both wasted the energy of signal, had influenced the further constriction of bandwidth again.In addition, we adopt correlation demodulation by the VWDK modulated output signal to Fig. 1 (a) in " 03152978.X " number patent application, though better performances, requiring has higher sample rate, has increased the weight of hard-wired cost, has influenced the raising of frequency modulating signal.

Summary of the invention

Technical problem: the information modulation and demodulation method that the purpose of this invention is to provide a kind of operating factor of highband of constant amplitude, the band efficiency of this information modulation and demodulation method is higher, realization is simpler fast, be more conducive to real-time processing, the ability of opposing channel distortion is stronger.

Technical scheme: the present invention divides information modulation and demodulation method, and two method is as follows respectively:

1) a kind of improved VWDK modulator approach

This mode directly changes the waveform of sinusoidal carrier with the binary message code element, makes the modulated signal g of counterlogic " 0 " ₀(t) and the modulated signal g of counterlogic " 1 " ₁And only control this different wave shape and signal bandwidth (t) and the different wave shape minimum between the sinusoidal signal, with a parameter; This modulation system can be expressed as:

$g_0\left(t\right)=\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20041006468100121.png,A20041006468100131.png"\; state="\{\{state\}\}">sin</figure-callout>}\frac{2\mathrm{\&pi;t}}{T}-x\left(t\right),$

$g_1\left(t\right)=\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20041006468100121.png,A20041006468100131.png"\; state="\{\{state\}\}">sin</figure-callout>}\frac{2\mathrm{\&pi;t}}{T}+x\left(t\right),$

$0\&le;t\&le;T$

Here T is the cycle of modulation waveform, also is the symbol intervals and the symbol width of information simultaneously; F=1/T then is the frequency of signal waveform, numerically also equals the transmission rate of code element; And x (t) is additional manipulated signal; This modulation system also has following technical characterictic:

1. being the polarity sign that directly changes additional signal x (f) with the binary message code element, is the sinusoidal carrier stack of T with the cycle again, finishes modulated process;

2. Fu Jia manipulated signal x (t) reaches maximum A and about the t=T/2 symmetry at t=T/2;

3. represent the g of " 0 " code element ₀(t) and the representative " 1 " code element g ₁(t)=-g ₀(T-t), the amplitude of its front and rear part or positive-negative half-cycle all equates, and peak value lays respectively at $t=\frac{T}{4}$ With $t=\frac{3T}{4}$ The place does not have parasitic amplitude modulation(PAM);

4. g ₀(t) and g ₁(t) exist $0\&le;t\&le;\frac{T}{4}$ With $\frac{3T}{4}\&le;t\&le;T$ Time period is the sine wave of standard, thereby can suppress the broadening of modulated wave frequency spectrum better.

Requirement reaches maximum A and about the t=T/2 symmetry at t=T/2, and manipulated signal additional in the expression formula of modulation system " 1 " is chosen following raised cosine

Change the amplitude A of additional manipulated signal x (t), the bandwidth and the signal to noise ratio of the output of control modulation signal, this modulation signal can obtain higher band efficiency after filtering.

Wherein A＞0 is unique Waveform Control parameter, can regulate the transmission bandwidth and the received signal to noise ratio of modulation signal.Therefore, improve waveform everywhere continuously, can lead, satisfy g ₁(t)=-g ₀(T-t) and $0\&le;t\&le;\frac{T}{4}$ With $\frac{3T}{4}\&le;t\&le;T$ Time period is exactly the sine wave of standard.Fig. 1 (b) is the time domain waveform of its power normalization.As seen this improvement waveform has kept the constant of modulated signal amplitude, so be not subjected to the influence of system's amplitude limit, also helps the synchronous of signal simultaneously.Fig. 2 (b) has then provided the corresponding power spectrum of this waveform, and it is compared with Fig. 2 (a), and visible high order harmonic component composition is eliminated fully, and spectrum energy is more concentrated, and the overall attenuation trend of spectrum envelope is also faster.Shortcoming then is that the main lobe of frequency spectrum has been widened, and this can suppress with band pass filter.

The realization of 2. improved VWDK modulation

By (1) formula respectively to the g of representative information " 0 " ₀(t) and the g of representative information " 1 " ₁(t) basic modulation waveform sampling, " 0 ", " 1 " digital waveform sample storage of the complete cycle that sampling is obtained (according to bandwidth requirement, also can be stored through the filtered waveform sample of digital band pass) in two memory blocks.Utilize the electronic switch of " alternative ", under the control of information sequence to be sent, in modulation period T, the corresponding waveform sample of gating memory block respectively.And the waveform sample in the memory block, then according to the beat of clock generator, the high frequency analog signals after digital to analog converter (DAC) converts modulation to is exported or emission.The theory diagram that it is complete such as Fig. 3, as seen this scheme is that full digital is realized, accurate, stable, the upper frequency limit that can realize only depends on the speed with DAC basically, be convenient to the making of integrated circuit (IC), also be convenient to utilize digital filtering accurately to control bandwidth and the spectral shape that sends signal.

2) based on the demodulation mode of zero passage detection

In the demodulates information mode based on zero passage detection, only need mid point (t=T/2 constantly) judgement of once sampling at the received signal waveform can finish demodulation, complexity and operand are very low, apply hard-limiting and come the suppressor pulse interference of noise.

By Fig. 1 (b) as can be known, the mid point of code-element period be t=T/2 constantly, g is arranged ₀(T/2)=-A, g ₁(T/2)=A.Thereby if sample to received signal in this moment, can to adjudicate transmission information be " 1 " or " 0 " according to the amplitude of sampling and polarity, used coherent detection (matched filtering in this simple zero passage detection demodulation (Fig. 4) comparable " 03152978.X " number patent application, see Fig. 5) reduce sample rate (can reduce by 20 times at least) greatly, thus greatly improve processing speed.

3) the further raising of band efficiency

Original VWDK waveform to Fig. 1 (a) can certainly adopt same zero passage detection demodulation method, but judgement still is selected in the mid point of code-element period constantly if will take a sample, then compare with (1), (2) formula and the improvement waveform of Fig. 1 (b), it is stronger to expect that the latter resists the ability of wave distortion.This wave distortion also comprises the influence that channel width is limited certainly.Therefore it is contemplated that the improvement modulation waveform of Fig. 1 (b) is expected by the narrower channel of bandwidth, thereby obtain band efficiency more efficiently.

In order to confirm this-deduction, the present invention in an embodiment to Fig. 1 (a) and new and old VWDK modulation waveform (b) respectively by behind the band pass filter all in the judgement of sampling of the mid point of code-element period, and the signal spectrum after keeping under the prerequisite of same bit error rate relatively the two through band pass filter separately, result such as Fig. 6 (a) and Fig. 6 (b).Corresponding bit error rate performance then as shown in Figure 7.As shown in Figure 7, the bit error rate performance of the two is almost completely identical, and the frequency band that takies after the improvement VWDK waveform filtering of Fig. 6 (b) is obviously narrower than Fig. 6 (a), has obviously improved band efficiency.

4) checking of anti-amplitude limit effect

Fig. 7 has also provided the improvement waveform simultaneously through hard-limiting (i.e. " slicing ".Peak amplitude ratio before and after the amplitude limit is ) error performance of back filtering. visible about 30% amplitude limit is to the almost not influence of improved VWDK modulation signal error performance.If further the amplitude of slicing is increased to 80%, then as seen from Fig. 8, the worst 4dB that also is no more than of the deterioration of its performance.

Beneficial effect: compare with the actual effect (Fig. 1 (a)) of the VWDK modulator approach of the operating factor of highband that proposes in " 03152978.X " number patent application, the improved VWDK modulator approach of the present invention (Fig. 4, actual effect is then as Fig. 1 (b)) and demodulation method (Fig. 5) remove the whole advantages kept former invention, control flexibly outside (only needing to change a waveform parameter A), the adaptation face width etc. as total digitalization realization, system, also have following advantage:

1. band efficiency is higher.

The improvement modulation effect of Fig. 1 (b) is than the more approaching sine wave of Fig. 1 (a), and Fig. 6 shows: under the prerequisite of demodulation performance suitable (Fig. 7), do not contain the line spectrum of high order harmonic component in the modulated output signal of improving one's methods, the bandwidth of occupying is narrower, and spectrum energy is also more concentrated.For example, comparison diagram 6 (a) and Fig. 6 (b)-40dB ,-60dB and-the 80dB bandwidth.

2. realization is simpler fast, is more conducive to real-time processing.

Because the g of VWDK modulation signal ₀(t) and g ₁(t) all the spitting image of sine wave, shape differences is very little, thereby " 03152978.X " number patent application adopts the correlation demodulation of Fig. 5,20 points of in a wave period T, will sampling at least to received signal, otherwise be not enough to pick out the two difference.Therefore, synchronously accurately under the prerequisite, to do 20 multiplication and addition (two integrators of Fig. 5 can be realized with parallel multiplication, and can merge) at least and could realize demodulation, but also will store this 20 sampled values 1 information.And the present invention presses Fig. 4 and only needs at T/2 once to signal sampling constantly to need not to take advantage of, add and can adjudicate, and the entire process process is greatly simplified.Therefore be not difficult to find out that the present invention is for Fig. 1 (b) zero passage detection demodulation method that modulation signal adopted, it is information rate that sample rate can be low to moderate signal frequency, and control methods is higher 20 times than signal frequency at least.Even so, even the operand of two kinds of methods is suitable, under identical level of hardware, the signal frequency that the present invention can demodulation can improve 20 times at least.And the advantage of VWDK modulation system operating factor of highband just need embody with higher information rate and use.

The ability of 3. resisting channel distortion is stronger.

Modulation output of the present invention is the VWDK waveform of constant amplitude, it can stand the narrower bandpass filtering of bandwidth, can stand the influence of system's amplitude limit again to a certain extent, this shows that this waveform has all strengthened in the linear distortion (limited as frequency band) of opposing transmission channel and the ability aspect the nonlinear distortion (as amplitude limit).In addition, owing to can carry out amplitude limiting processing to received signal, opposing impulsive noise interference capability has also strengthened greatly.

In a word, the present invention has further promoted the advantage of VWDK modulation system operating factor of highband, has improved some deficiency of original modulator approach, can greatly reduce the cost of hard-wired complexity and application-specific integrated circuit (ASIC).

Description of drawings

Fig. 1 (a) is the output signal of " 03152978.X " number patent application original VWDK modulator approach of inventing, as a comparison; Fig. 1 (b) is the output signal of the improved VWDK modulator approach that proposes of present patent application.

Fig. 2 (a) be original VWDK modulation signal (the logarithmic table diagrammatic sketch of power spectrum amplitude of τ=0.475T), as a comparison; And the logarithmic table diagrammatic sketch of the VWDK modulation signal power spectrum amplitude that Fig. 2 (b) is a present patent application to be proposed.

Fig. 3 is the VWDK modulation signal modulating system block diagram that present patent application proposes.

Fig. 4 is the VWDK demodulating system block diagram that present patent application proposes.

Fig. 5 is the VWDK demodulating system block diagram that the 03152978.X patent application is proposed.

Fig. 6 (a) and (b) be respectively original with improve the through-put power spectrum of VWDK method when keeping demodulation performance identical.

Fig. 7 be two kinds of VWDK modulator approaches and improve one's methods behind 30% amplitude limit the bit error rate performance curve ratio.

Fig. 8 is two kinds of VWDK signal waveforms and improves the bit error rate performance curve ratio of waveform behind 80% amplitude limit.

Embodiment

The information modulation system of the operating factor of highband of constant amplitude of the present invention directly changes the waveform of sinusoidal carrier with the binary message code element, makes the modulated signal g of counterlogic " 0 " ₀(t) and the modulated signal g of counterlogic " 1 " ₁And only control this different wave shape and signal bandwidth (t) and the different wave shape minimum between the sinusoidal signal, with a parameter; This modulation system can be expressed as:

$g_0\left(t\right)=\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20041006468100121.png,A20041006468100131.png"\; state="\{\{state\}\}">sin</figure-callout>}\frac{2\mathrm{\&pi;t}}{T}-x\left(t\right),$

$g_1\left(t\right)=\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20041006468100121.png,A20041006468100131.png"\; state="\{\{state\}\}">sin</figure-callout>}\frac{2\mathrm{\&pi;t}}{T}+x\left(t\right),$

$0\&le;t\&le;T$

Here T is the cycle of modulation waveform, also is the symbol intervals and the symbol width of information simultaneously; F=1/T then is the frequency of signal waveform, numerically also equals the transmission rate of code element; And x (t) is additional manipulated signal; This modulation system also has following technical characterictic:

1. being the polarity sign that directly changes additional signal x (t) with the binary message code element, is the sinusoidal carrier stack of T with the cycle again, finishes modulated process;

2. Fu Jia controlled letter signal x (t) reaches maximum A and about the t=T/2 symmetry at t=T/2;

3. represent the g of " 0 " code element ₀(t) and the representative " 1 " code element g ₁(t)=-g ₀(T-t), the amplitude of its front and rear part or positive-negative half-cycle all equates, and peak value lays respectively at $t=\frac{T}{4}$ With $t=\frac{3T}{4}$ The place does not have parasitic amplitude modulation(PAM);

4. g ₀(t) and g ₁(t) exist $0\&le;t\&le;\frac{T}{4}$ With $\frac{3T}{4}\&le;t\&le;T$ Time period is the sine wave of standard, thereby can suppress the broadening of modulated wave frequency spectrum better.

Manipulated signal additional in the expression formula of modulation system " 1 " is chosen following raised cosine

Change the amplitude A of additional manipulated signal x (t), the bandwidth and the signal to noise ratio of the output of control modulation signal, this modulation signal can obtain higher band efficiency after filtering.

Get A=0.15, T=50 μ S, the logarithm amplitude that obtains VWDK modulator approach output signal power of the present invention spectrum is shown in Fig. 2 (b), and wherein ordinate is that power spectrum range value with carrier frequency 20kHz place is as 0dB.As seen from the figure, discrete portions in the output signal power of the improving one's methods spectrum does not have higher harmonic components, and the amplitude of other spectrum component is at least than the low approximately 50dB of first-harmonic (20kHz) (be equivalent to approximately 100,000 of first-harmonic/), therefore, the output modulation signal of new method more approaches sine wave than the output modulation signal of original method.

The embodiment of VWDK modulator of the present invention such as Fig. 3, being kept in advance in the memory is by the defined g of " 1 " and " 2 " formula ₀(t) and g ₁(t) (promptly the waveform sample of representative " 0 " and " 1 " respectively has 10-20 to the discrete sampling value in the waveform one-period.According to bandwidth requirement, also can store) through the filtered waveform sample of digital band pass.Utilize the electronic switch of " alternative " then, under the control of the defeated information sequence of tendency to develop, select corresponding g according to the sample frequency that clock generator provided ₀(t) waveform sample (if information bit is " 0 ") or g ₁(t) waveform sample (if information bit is " 1 "); The modulation waveform numeral sample of being chosen is directly changed into the VWDK modulated wave output of simulation by DAC.Whole VWDK modulating system is that total digitalization realizes, is easy to be integrated on a slice integrated circuit.

In the demodulates information mode based on zero passage detection, only need mid point (t=T/2 constantly) judgement of once sampling at the received signal waveform can finish demodulation, complexity and operand are very low, apply hard-limiting and come the suppressor pulse interference of noise.

Fig. 4 is the embodiment of VWDK demodulator of the present invention: have VWDK received signal because of Channel Transmission noise and distortion distortion deterioration through bandpass filtering, be divided into two-way: the one tunnel is used for extracting carrier frequency, to form sampling pulse (being digital phase-locked loop): and another road is after the sampling of t=T/2 fixing point, through the zero-crossing detector judgement, finish demodulation to corresponding " 0 ", " 1 " sequence.

For present embodiment, we can realize the transmission code rate of 20kb/s equally in the signal bandwidth of 200-300Hz (even lower), and modulation efficiency reaches 60-100bits/s/Hz (even higher).

Claims (3)

1 ,-and the information modulation system of the operating factor of highband of kind of constant amplitude, it is characterized in that this mode directly changes the waveform of sinusoidal carrier with the binary message code element, make the modulated signal g of counterlogic " 0 " ₀(t) and the modulated signal g of counterlogic " 1 " ₁And only use (t) and the different wave shape minimum between the sinusoidal signal ,-individual parameter controls this different wave shape and signal bandwidth; This modulation system can be expressed as:

$g_0\left(t\right)=\sin \frac{2\mathrm{\&pi;t}}{T}-x\left(t\right),$

O≤t≤T 1

$g_1\left(t\right)=\sin \frac{2\mathrm{\&pi;t}}{T}-x\left(t\right),$

Here T is the cycle of modulation waveform, also is that the symbol intervals and the symbol width of information: f=1/T then is the frequency of signal waveform simultaneously, numerically also equals the transmission rate of code element; And x (t) is additional manipulated signal; This modulation system also has following technical characterictic:

1. being the polarity sign that directly changes additional signal x (t) with the binary message code element, is the sinusoidal carrier stack of T with the cycle again, finishes modulated process;

2. Fu Jia manipulated signal x (t) reaches maximum A and about the t=T/2 symmetry at t=T/2;

3. represent the g of " 0 " code element ₀(t) and the representative " 1 " code element g ₁(t)=-g ₀(T-t), the amplitude of its front and rear part or positive-negative half-cycle all equates, and peak value lays respectively at $t=\frac{T}{4}$ With $t=\frac{3T}{4}$ The place does not have parasitic amplitude modulation(PAM):

4. g ₀(t) and g ₁(t) exist $0\&le;t\&le;\frac{T}{4}$ With $\frac{3T}{4}\&le;t\&le;T$ Time period is the sine wave of standard, but thereby official two suppress the broadening of modulated wave frequency spectrum well.

2, the height of constant amplitude according to claim 1 is quite with the information modulation system of utilance, and additional manipulated signal is chosen following raised cosine in the expression formula " 1 " of the system mode that it is characterized in that withering

Change the amplitude A of additional manipulated signal x (t), the bandwidth and the signal to noise ratio of the output of control modulation signal, this modulation signal can obtain higher band efficiency after filtering.

3, a kind of demodulates information mode of information modulation system of the operating factor of highband that is applicable to the described constant amplitude of claim 1, it is characterized in that in the demodulates information mode based on zero passage detection, only need mid point (t=T/2 constantly) judgement of once sampling to finish demodulation at the received signal waveform, complexity and operand are very low, apply hard-limiting and come the suppressor pulse interference of noise.

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