CN101729471B - Composite transmission communication method of analogue signal and digital signal of broadcast communication system - Google Patents

Abstract

The invention discloses a composite transmission communication method of the analogue signal and the digital signal of a broadcast communication system, which comprises two parts of the composite sending of the analogue signal and the digital signal, and the reception and demodulation of composite information, wherein the composite sending of the analogue signal and the digital signal comprises the steps of source coding, channel coding, carrier wave formation and base band modulation; the carrier wave formation comprises: directly changing the wave form of the carrier wave by using binary information code element. The modulated wave form f1 (t) generated when the information bit is 1 and the modulated wave form f0 (t) generated when the information bit is 0 have adjustable small difference compared with standard sine waves. The reception and demodulation of the composite information comprises the steps of demodulation of analogue speech signals, demodulation of digital signals, channel decoding and source decoding. The composite sending of the analogue speed signals and the high-speed digital information can be realized only by slightly changing the prior broadcast system.

Description

The compound transmission and communication method of the analog signal of broadcast communication system and digital signal

Technical field

The present invention is a kind of analog signal and compound transmission and communication method of digital signal based on constant amplitude isoperimetric period modulated carrier wave, can apply in the broadcast communication system that need modulate the amplitude of carrier wave.

Background technology

Existing broadcast system all is to adopt the method that is modulated to the voice signal of low frequency on the higher frequency band to come convenient transmission.Simulation amplitude modulation double side band (DSB-AM) to keep carrier wave is an example, and carrier wave itself does not carry useful information, but has but consumed significant amount of energy.With the AM broadcasting is example; Carrier wave only plays the effect of delivery vehicle therein, has but occupied 2/3rds of total emission power, if can fully utilize this part carrier wave; Also transmit one road useful information rather than waste, just can improve the efficient of existing communication system greatly.

Summary of the invention

The objective of the invention is in order to overcome the defective that prior art exists; A kind of analog signal and compound transmission and communication method of digital signal that is used for broadcast communication system is provided, and this method can also be transmitted one road high-speed multimedia information based on constant amplitude isoperimetric period modulated carrier wave technology through carrier wave in transmission of speech signals; Thereby enlarge the application surface of broadcast system; Realize multiple expanded function,, see picture and see TV etc. such as on broadcast receiver, seeing electronic newspaper.

Realize the foregoing invention purpose; Need seek a kind of carrier waveform that can effectively characterize digital information; This waveform should have following characteristics: at first, the length of each code-element period of carrier wave should be the same, and this has also just determined no matter be to characterize which kind of information; The cycle of carrier wave is fixed, and frequency is also just constant.Secondly, if need modulate the amplitude of carrier wave with low frequency signal, the amplitude that just requires carrier wave must be constant, and the amplitude of carrier wave can not take place along with the change of the digital information " 0 " that characterizes and " 1 " to jump or distortion.The 3rd, the difference of two kinds of basic waveforms in the carrier wave should be controlled, to adapt to the environment of different signal to noise ratios, also can have influence on bandwidth and modulation efficiency when changing the waveform separation degree, and two above-mentioned basic characteristics can not change to some extent in this process simultaneously.

The analog voice signal of low frequency is sent into the audio input port of AM broadcast transmitter, carrier wave is carried out sending after the amplitude modulation; At receiving terminal, the primary speech signal that can adopt the method for coherent demodulation or non-coherent demodulation to obtain sending.

The compound transmission and communication method of the analog signal of broadcast communication system of the present invention and digital signal comprises the compound transmission of analog signal and digital signal and reception two parts of composite information; Wherein

The compound transmission of analog signal and digital signal may further comprise the steps:

1, source encoding

Multi-medium data (like captions, picture, figure, video, sound etc.) is carried out respective coding and compression, export one tunnel source coded data stream subsequently;

2, chnnel coding

In order to strengthen the reliability that data are transmitted in channel, the source coded data stream of top output is carried out error correction coding and interweaved;

3, carrier wave is shaped

With carrier signal being modulated, make each code-element period of carrier wave can characterize one-bit digital information through the source encoding number after above-mentioned 1,2 steps;

4, baseband modulation

With analog voice signal the carrier signal of a last generating step is carried out amplitude modulation(PAM), then through sending from transmitting antenna behind band pass filter and the power amplifier.

The result of above-mentioned first three step is that output has added high speed digital information high frequency carrier on it, and last step is to modulate above-mentioned high frequency carrier with the audio signal of simulation.

Said carrier wave is shaped, and is to utilize the binary message code element directly to change the waveform of carrier wave, the modulation waveform f of generation when information bit be " 1 " ₁(t) the modulation waveform f that produces and when information bit is " 0 " ₀(t) compare with standard sine wave and have adjustable fine difference; This modulation system can be expressed as:

$f(t,\mathrm{\&tau;})=\left\{\begin{array}{cc}\sin \mathrm{<figure-callout\; id="0"\; label="t"\; filenames="H2008101548569E00021.png,H2008101548569E00031.png"\; state="\{\{state\}\}">t</figure-callout>}& 0\&le;t\&le;\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\\ \sin (\frac{t-\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}}{\mathrm{\&tau;}-\frac{T}{4}}\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}+\frac{T}{4})& \frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\&le;t\&le;\mathrm{\&tau;}\\ \sin (\frac{t-\mathrm{\&tau;}}{\frac{3T}{4}-\mathrm{\&tau;}}\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}+\frac{T}{2})& \mathrm{\&tau;}\&le;t\&le;\frac{3\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\\ \sin t& \frac{3\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\&le;t\&le;T\end{array}\right.---\left(1\right)$

Wherein: T is the cycle of modulation waveform, also is the symbol intervals of code-element period and information simultaneously; F=1/T is the frequency of carrier wave, numerically also equals the transmission rate of code element; When information bit was " 1 ", waveform generator produced $\mathrm{\&tau;}=(1+\mathrm{\&alpha;})\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}$ The time f (t) (remember into f ₁(t)); When information bit was " 0 ", waveform generator produced $\mathrm{\&tau;}=(3-\mathrm{\&alpha;})\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}$ The time f (t) (remember into f ₀(t)), α (0 wherein<α<1) is waveform regulation and control parameters.

This modulation system has following technical characterictic:

The difference of a, two kinds of basic waveforms reaches maximum at t=T/2.

B, two kinds of basic waveform amplitude A are invariable, and peak value lays respectively at t=T/4 and t=3T/4 place, and can any change not take place along with the increase of basic waveform difference.

C, waveform satisfy f ₁(t)=-f ₀(T-t), f ₀(t) and f ₁(t) be the sine wave of standard in the time period in [0, T/4] and [3T/4, T], its frequency spectrum has obtained better compression.

The frequency of d, this modulation waveform is invariable all the time and is numerically equal to bit rate.

E, can control the difference size of two kinds of basic waveforms through the selection of waveform regulation and control parameter alpha (0 < α < 1); When being in the discrimination that can weaken different wave under the big signal to noise ratio environment through increase α, can be under the little signal to noise ratio environment when being in through reducing the discrimination that α strengthens different wave.

In addition, in each code-element period, no matter be to select any waveform, transmitting power is almost constant.

The receiving demodulation of composite information

1, the demodulation of analog voice signal

High frequency radio wave is divided into two-way after antenna receives; The influence that one tunnel noise jamming and channel distortion in band pass filter filtering channel caused; Because the envelope of high frequency carrier reflected accurately the voice signal that will transmit, so can demodulate the simulated audio signal of transmitting terminal through the envelope detection link on traditional receiver;

2, the demodulation of digital signal

Demodulate the digital information that is hidden in wherein the high frequency carrier of the radio wave that receives from another route antenna; Two kinds of demodulation methods are arranged: method one, carry out small phase difference detection at half place of each code-element period of carrier wave, or the zero crossing detection, to recover bit information; Method two, utilize carrier signal and transmitting terminal two kinds of basic waveforms coherence's difference and select coherent demodulation for use;

3, channel decoding

From the data code flow that step 2 demodulates, remove chnnel codings such as error correcting code;

4, source decoding

The inverse process of source encoding finally recovers the literal that transmitting terminal sends, picture, multimedia messagess such as video.

The inventive method has following beneficial effect with respect to prior art:

1, make full use of existing broadcast system equipment, only need do less change to transmitter, simulated audio signal directly inserts from audio port, still can keep existing AM broadcasting system, and equipment cost is low, brings notable results.

2, from radio wave, receive analog voice signal as usual without the common reception function of transforming, and the high-end broadcast receiver of the band display screen that process is transformed can also receive the high speed digital information that is attached on the carrier wave, convenient realization is backward compatible.

3, the carrier wave of this smoothing has good narrow-band characteristic in frequency domain, and spectrum energy is also comparatively concentrated.Through can changing the discrimination of basic waveform to waveform regulation and control parameter control, adapting to the occasion of different signal to noise ratios, thereby between bandwidth efficiency and demodulation performance, seek a balance point.

4, transmit effective information through carrier wave, the frequency of carrier wave numerically just equals the transfer rate of digital information, and this has promoted the efficient of communication system to a great extent.

The frequency of this novel carrier waveform of 5, selecting for use is invariable, can extract synchronizing signal comparatively easily separating timing.

When the information bit that 6, no matter will characterize was " 1 " or " 0 ", the amplitude constant of two kinds of basic waveforms that waveform generator produces was constant, and waveform can not distort along with the variation of regulation and control parameter value, and antijamming capability has obtained enhancing.

7, consider from the fail safe of communication; It is also not obvious in the wave form varies of high frequency carrier in each bit period wherein to have contained a large amount of high speed digital informations; If on transmission channel, be superimposed with noise again; Almost be difficult to tell on directly perceived on itself and the traditional approach and utilize the difference of single sine wave as the carrier waveform of high frequency carrier; This has also just strengthened the confidentiality of communication system greatly, through with the combining of other decoding methods and self-defining communication protocol, can be so that security of communication system be further strengthened.

Description of drawings

Fig. 1, be the theory diagram of the broadcast communication system (transmitting terminal) of embodiment of the present invention method.

Fig. 2, be the theory diagram of the broadcast communication system (receiving terminal) of embodiment of the present invention method.

Fig. 3 (a) is the output signal (regulation and control parameter alpha=0.9) of " 03152978.X " number patent application original VWDK modulator approach of inventing; Fig. 3 (b) is the output signal (regulation and control parameter A=0.2) of " 200410064681.4 " number improved VWDK modulator approach that patent application proposed; Fig. 3 (c) is the output signal (regulation and control parameter alpha=0.9) of the modulator approach in cycle such as the employed novel constant amplitude of this patent.

Fig. 4 (a) is the output signal (value of α is from 0.2～0.9) of " 03152978.X " number patent application original VWDK modulator approach of inventing; Fig. 4 b) is the output signal (value of A is from 0.2～0.9) of " 200410064681.4 " number improved VWDK modulator approach that patent application proposed.Fig. 4 (c) is the output signal (value of α is from 0.2～0.9) of the inventive method.

Fig. 5, be in the inventive method digital signal to the system block diagram of cycle carrier modulation such as novel constant amplitude.

Fig. 6, be the system block diagram that from cycle carrier waves such as constant amplitude, demodulates digital signal (method one) in the inventive method.

Fig. 7, be the system block diagram that from cycle carrier waves such as constant amplitude, demodulates digital signal (method two) in the inventive method.

Fig. 8, be the analog voice signal of transmitting terminal.

Fig. 9, be that frequency is the cycle carrier waveforms such as constant amplitude of 1kHz.

Figure 10, be voice signal to the oscillogram after constant amplitude isoperimetric phase carrier wave f (t) modulation.

Figure 11, be voice signal to the oscillogram after carrier wave g (t) modulation that does not have constant constant amplitude characteristic in " 03152978.X " number patent and " 200410064681.4 " number patent.

Figure 12, be the comparison diagram (to f (t)) of the speech waveform of speech waveform and transmission after the demodulation.

Figure 13, be the comparison diagram (to g (t)) of the speech waveform of speech waveform and transmission after the demodulation.

Embodiment

Below in conjunction with accompanying drawing, the present invention is done further explain.

Fig. 1,2 is the AM broadcast transmission system of embodiment of the present invention method.Among the figure in the frame of broken lines content be new part of adding, be existing AM broadcast system outside the frame of broken lines.The transmitting terminal of native system is compared difference and just at carrier wave the place is provided with traditional transmitting station, conventional method is to adopt the sine wave of single-frequency as high frequency carrier, and employing here is the carrier signal of having added high speed digital information.At first, simulated audio signal a (t) and DC level M addition, the high frequency carrier that the carrier wave formation system in the frame of broken lines is provided carries out the DSB-AM modulation, behind band pass filter and power amplifier, gets into channel again.Receiving terminal divides two-way; One the tunnel still as traditional receiving terminal; High frequency radio wave demodulates the simulated audio signal of transmission through band pass filter and envelope detection link, and small phase difference detection then will be carried out or zero crossing detects to recover the digital information that is hidden in the carrier wave to each code element of the high frequency carrier that recovers in another road, finally restores the multi-medium data that is additional to wherein; Here can be literal, picture and even be video file.

It is with a vast territory that the advantage of this scheme is to have made full use of China's physical features; The characteristics that the broadcasting station is numerous; Less to existing broadcasting system change, the routine that this technology can't have influence on common receiver receives, and from radio wave, receives analog voice signal as usual without the radio reception function of transforming; And the high-end broadcast receiver of the band display screen that process is transformed can also receive the high speed digital information that is attached on the carrier wave, realizes backward compatible easily.On the carrier wave link, selected the digital signal modulation and the demodulation method in cycles such as a kind of constant amplitude for use, can control the difference of two kinds of basic waveforms through a waveform is regulated and control parameter control, thereby in bandwidth efficiency and demodulation performance, seek a balance point.

One, transmitting terminal

Transmitting terminal comprises the source encoding to multi-medium data, chnnel coding, several big links such as carrier wave shaping and baseband modulation.Wherein the result of first three step is that output has added high speed digital information high frequency carrier on it, and last step is to modulate above-mentioned high frequency carrier with the audio signal of simulation.

1, source encoding

Multi-medium data (like captions, picture, figure, video, sound etc.) is carried out respective coding and compression, export one tunnel source coded data stream subsequently;

2, chnnel coding

In order to strengthen the reliability that data are transmitted in channel, the data flow of the source encoding of top output is carried out error correction coding and interweaved.

3, carrier wave is shaped

With carrier signal being modulated, make each code-element period of carrier wave can characterize one-bit digital information through the data after above-mentioned two links output.

This method utilizes the binary message code element directly to change the waveform of carrier wave, the modulation waveform f that when information bit is " 1 ", produces ₁(t) the modulation waveform f that produces and when information bit is " 0 " ₀(t) compare with standard sine wave and have adjustable fine difference.This modulation system can be expressed as:

$f(t,\mathrm{\&tau;})=\left\{\begin{array}{cc}\mathrm{<figure-callout\; id="0"\; label="sin\; t"\; filenames="H2008101548569E00021.png,H2008101548569E00031.png"\; state="\{\{state\}\}">sin</figure-callout>}t& 0\&le;t\&le;\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\\ \sin (\frac{t-\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}}{\mathrm{\&tau;}-\frac{T}{4}}\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}+\frac{T}{4})& \frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\&le;t\&le;\mathrm{\&tau;}\\ \sin (\frac{t-\mathrm{\&tau;}}{\frac{3T}{4}-\mathrm{\&tau;}}\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}+\frac{T}{2})& \mathrm{\&tau;}\&le;t\&le;\frac{3\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\\ \sin t& \frac{3\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}\&le;t\&le;T\end{array}\right.---\left(1\right)$

Wherein: T is the cycle of modulation waveform, also is the symbol intervals of code-element period and information simultaneously; F=1/T is the frequency of carrier wave, numerically also equals the transmission rate of code element; When information bit was " 1 ", waveform generator produced $\mathrm{\&tau;}=(1+\mathrm{\&alpha;})\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}$ The time f (t) (remember into f ₁(t)); When information bit was " 0 ", waveform generator produced $\mathrm{\&tau;}=(3-\mathrm{\&alpha;})\frac{\mathrm{<figure-callout\; id="4"\; label="T"\; filenames="H2008101548569E00031.png,H2008101548569E00072.png"\; state="\{\{state\}\}">T</figure-callout>}}{4}$ The time f (t) (remember into f ₀(t)), α (0 wherein<α<1) is waveform regulation and control parameters.

This modulation system has following technical characterictic:

The difference of a, two kinds of basic waveforms reaches maximum at t=T/2.

B, two kinds of basic waveform amplitude A are invariable, and peak value lays respectively at t=T/4 and t=3T/4 place, and can any change not take place along with the increase of basic waveform difference.

C, waveform satisfy f ₁(t)=-f ₀(T-t), f ₀(t) and f ₁(t) be the sine wave of standard in the time period in [0, T/4] and [3T/4, T], its frequency spectrum has obtained better compression.

The frequency of d, this modulation waveform is invariable all the time and is numerically equal to bit rate.

E, can control the difference size of two kinds of basic waveforms through the selection of waveform regulation and control parameter alpha (0 < α < 1); When being in the discrimination that can weaken different wave under the big signal to noise ratio environment through increase α, can be under the little signal to noise ratio environment when being in through reducing the discrimination that α strengthens different wave.

In addition, in each code-element period, no matter be to select any waveform, transmitting power is almost constant.

Two sections function g (t) (shown in Fig. 3 (a)) that itself and prior art Chinese patent (patent No. 03152978.X) are invented compare; In a code-element period; Two kinds of basic code unit waveforms of the characterization logic " 0 " of g (t) and logical one almost do not overlap part; Amplitude is disunity also, and the bigger discrepancy in two kinds of waveform time domains causes the performance in the frequency domain also to be difficult to promote.The patent No. 200410064681.4 Chinese patents; Though waveform has been carried out some amplitude limiting processing; But if under the low signal-to-noise ratio condition in order further to strengthen the discrimination of two kinds of basic waveforms, guarantee that the accuracy of message transmission just need strengthen the otherness of two kinds of basic waveforms through the increase parameter A, along with the further increase of parameter A; The amplitude of two kinds of basic waveforms begins to occur disunity gradually; Particularly increase to 0.5 when above as A, the saltus step of two kinds of wave-shape amplitude is quite obvious, can't satisfy amplitude unified demand (Fig. 3 (b)).

In sum; The waveform (Fig. 3 (c)) that has only (1) formula to propose satisfies the three big requirements that in the background technology carrier wave proposed; Compare with the waveform in other two patents and to have greater advantage, so select this waveform as carrier waveform, the analogous diagram of back has also fully proved this point.The forming circuit of carrier waveform is as shown in Figure 5.

4, baseband modulation

Carry out amplitude modulation(PAM) with the carrier signal to a last generating step after analog voice signal and the DC level addition, then through sending from transmitting antenna behind band pass filter and the power amplifier.

To Fig. 1,2, suppose that wherein a (t) is an analog voice signal, M is the required DC level of double-sideband modulation, b (t) be by the binary data of the multimedia messages decision that will transmit, f (t) is a carrier wave, that decide transmission by the value of b (t) is f ₁(t) still be f ₀(t), no matter select to send any waveform, the cycle T c of carrier wave fixes, and this just means carrier frequency f _c=1/T _cAlso fix, the f here (t) has replaced the high frequency sinusoidal carrier Asin (ω in the traditional broadcast communication mode _cT+ θ), suppose that through the noise effect behind the additive white Gaussian noise channel be n (t), then the signal of transmitter transmission does

s(t)＝(a(t)+M)f(t)+n(t). (1)

In emulation; The employing frequency is 0.1kHz; The cosine wave that amplitude is is as analog voice signal, and is as shown in Figure 8.Choosing M is 2, and the frequency of carrier wave f (t) is got 1kHz, and is as shown in Figure 9.The signal that then sends should be

$s\left(t\right)=\sqrt{2}(\cos (2\mathrm{\&pi;}\&times;100t)+2)f\left(t\right).---\left(4\right)$

Oscillogram after sinusoidal wave analog voice signal a (t) modulates carrier wave f (t) is shown in figure 10; Here also used simultaneously carrier wave g (t) emulation that does not have constant constant amplitude characteristic in " 03152978.X " number patent and " 200410064681.4 " number patent once, the result is shown in figure 11.

Contrast two width of cloth figure; Can clearly find out gap; Figure 10 is much smaller than the error of Figure 11, trace it to its cause just to be that this novel carrier wave f (t) amplitude in each code-element period width is constant all the time, and the carrier wave g (t) in other two patents does not have this characteristic; This will inevitably cause the envelope of high frequency carrier can not well embody the variation of voice signal, thereby causes bigger distortion.

Two, receiving terminal

Receiving terminal and transmitting terminal reversed in order are also divided four processes.

1, the demodulation of analog voice signal

High frequency radio wave is divided into two-way after antenna receives; The influence that one tunnel noise jamming and channel distortion in band pass filter filtering channel caused; Because the envelope of high frequency carrier reflected accurately the voice signal that will transmit, so can demodulate the simulated audio signal of transmitting terminal through the envelope detection link on traditional receiver;

At demodulating end, contrast two kinds of different carrier wave f (t) and g (t) and carry out corresponding demodulation, demodulation result such as Figure 12 respectively; Shown in 13, as can be seen from the figure, do high frequency carrier with f (t); Voice signal can well recover the analog voice signal of original transmission after envelope detection; Contrast the method for making high frequency carrier of g (t), the distortion after the demodulation is very big, and visible carrier wave f (t) is more suitable for being used on the broadcast communication system.

2, the demodulation of digital signal

Demodulate the digital information that is hidden in wherein the high frequency carrier of the radio wave that receives from another route antenna; Two kinds of demodulation methods are arranged: method one, carry out small phase difference detection at half place of each code-element period of carrier wave, to recover bit information, be characterized in that operand is low, equipment is simple, and processing speed is fast; Method two carries out zero crossing and detects, to recover bit information at half place of each code-element period of carrier wave;

Small phase difference demodulation method in this example need be to locate two/one-period once to sample to adjudicate just can accomplish demodulation at the mid point that receives signal waveform only.Fig. 6 is the instance of demodulator of the present invention, and modulated signal is divided into two-way through behind the bandpass filtering, and the carrier frequency of leading up to extracts synchronizing signal, forms sampling pulse; Another road is in half place's sampling of code-element period, and waveform phase information and standard sine wave phase that sampling is obtained compare, if waveform phase is more leading than standard sine wave phase, the binary message that can judge transmission is " 1 ", otherwise is " 0 ".The zero crossing detection method need be to locate two/one-period once to sample to adjudicate just can accomplish demodulation at the mid point that receives signal waveform equally only.Can know that by Fig. 3 (c) midpoint at code-element period has f ₀() > T/2; 0, f ₁(T/2)<0.So through sampling to received signal, can be " 1 " or " 0 " according to the binary element that the polarity of sampled value is adjudicated transmission in this moment.As shown in Figure 7, the modulated signal of reception is removed through band pass filter earlier and is disturbed, and gets into sampler then; Form sampling pulse and send into sampler by system clock; Sampler is sent signal sampling value into zero-crossing detector at half place of code-element period, if sampled value is a positive number, the binary message that can judge transmission is " 0 "; Otherwise be " 1 ", thereby restore the digital information of original transmitting terminal.

3, channel decoding

From the data code flow that step 2 demodulates, remove chnnel codings such as error correcting code;

4, source decoding

The inverse process of source encoding finally recovers the literal that transmitting terminal sends, picture, multimedia messagess such as video.

Claims (1)

1. the compound transmission and communication method of the analog signal of a broadcast communication system and digital signal comprises the compound transmission of analog signal and digital signal and composite information receiving demodulation two parts; Wherein

The compound transmission of analog signal and digital signal may further comprise the steps:

Step 1, source encoding

Multi-medium data is carried out respective coding and compression, export one tunnel source coded data stream subsequently;

Step 2, chnnel coding

In order to strengthen the reliability that data are transmitted in channel, the source coded data stream of top output is carried out error correction coding and interweaved;

Step 3, carrier wave are shaped

With carrier signal being modulated, make each code-element period of carrier wave can characterize one-bit digital information through the coded data after the above-mentioned steps 1,2;

Said carrier wave is shaped, and is to utilize the binary message code element directly to change the waveform of carrier wave, the modulation waveform f of generation when information bit be " 1 " ₁(t) the modulation waveform f that produces and when information bit is " 0 " ₀(t) compare with standard sine wave and have adjustable fine difference; This modulation system is expressed as:

$f(t,\mathrm{\&tau;})=\left(\begin{array}{cc}\sin t& 0\&le;t\&le;\frac{T}{4}\\ \sin (\frac{t-\frac{T}{4}}{\mathrm{\&tau;}-\frac{T}{4}}\frac{T}{4}+\frac{T}{4})& \frac{T}{4}\&le;t\&le;\mathrm{\&tau;}\\ \sin (\frac{t-\mathrm{\&tau;}}{\frac{3T}{4}-\mathrm{\&tau;}}\frac{T}{4}+\frac{T}{2})& \mathrm{\&tau;}\&le;t\&le;\frac{3T}{4}\\ \sin t& \frac{3T}{4}\&le;t\&le;T\end{array}\right)---\left(1\right)$

Wherein: T is the cycle of modulation waveform, also is the symbol intervals of code-element period and information simultaneously; F=1/T is the frequency of carrier wave, numerically also equals the transmission rate of code element; When information bit was " 1 ", waveform generator produced

The time f (t) (remember into f ₁(t)); When information bit was " 0 ", waveform generator produced

The time f (t) (remember into f ₀(t)), wherein α (0＜α＜1) is waveform regulation and control parameters;

This modulation system has following technical characterictic:

The difference of a, two kinds of basic waveforms reaches maximum at t=T/2;

B, two kinds of basic waveform amplitude A are invariable, and peak value lays respectively at t=T/4 and t=3T/4 place, and can any change not take place along with the increase of basic waveform difference;

C, waveform satisfy f ₁(t)=-f ₀(T-t), f ₀(t) and f ₁(t) be the sine wave of standard in the time period in [0, T/4] and [3T/4, T], its frequency spectrum has obtained better compression;

The frequency of d, this modulation waveform is invariable all the time and is numerically equal to bit rate;

E, can control the difference size of two kinds of basic waveforms through the selection of waveform regulation and control parameter alpha (0＜α＜1); When being in the discrimination that can weaken different wave under the big signal to noise ratio environment through increase α, can be under the little signal to noise ratio environment when being in through reducing the discrimination that α strengthens different wave;

Step 4, baseband modulation

With analog voice signal the carrier signal of a last generating step is carried out amplitude modulation(PAM), then through sending from transmitting antenna behind band pass filter and the power amplifier;

The composite information receiving demodulation, its step is following:

The demodulation of steps A, voice signal

High frequency radio wave is divided into two-way after antenna receives; The influence that one tunnel noise jamming and channel distortion in band pass filter filtering channel caused; Because the envelope of high frequency carrier reflected accurately the voice signal that will transmit, so partly can demodulate the simulated audio signal of transmitting terminal through the envelope detection on traditional receiver;

Step B, carrier wave recover

The high frequency radio wave that another road is received from antenna recovers carrier signal earlier and demodulates the digital information that is hidden in the high frequency carrier; Two kinds of demodulation methods are arranged: method one, to half place of each code-element period of carrier wave carrying out small phase difference detection, or waveforms amplitude detects, to recover bit information; Method two, the carrier waveform generator that utilizes carrier signal and transmitting terminal according to coherence's difference of two kinds of basic waveforms selecting of the different digital signal that will transmit use coherent demodulation;

Step C, channel decoding

From the data code flow that step B demodulates, remove chnnel codings such as error correcting code;

Step D, source decoding

The inverse process of source encoding finally recovers the multimedia messages that transmitting terminal sends.

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