CN101431496A - Modulation-demodulation method for fraction Fourier transform domain with unequal power spectral density - Google Patents
Modulation-demodulation method for fraction Fourier transform domain with unequal power spectral density Download PDFInfo
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- CN101431496A CN101431496A CNA2008102096342A CN200810209634A CN101431496A CN 101431496 A CN101431496 A CN 101431496A CN A2008102096342 A CNA2008102096342 A CN A2008102096342A CN 200810209634 A CN200810209634 A CN 200810209634A CN 101431496 A CN101431496 A CN 101431496A
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Abstract
A modulation and demodulation method for FRFT domain of unequal power spectrum density relates to synchronously transmitting multipath same signals of different spectral density or center frequency so as to solve problem that spectrum resources multiplexing is limited by number of pseudorandom code. N path signals and n path cutting signal are modulated for acquiring n path modulated signal; n path modulated signal are summed together and launched; the received sum signal are separately demodulated for acquiring n path demodulated signal; fraction order corresponding to every path demodulated signal and fraction domain peak value position are acquired according to central frequency and modulated frequency, and narrow band cutting wave form of peak value position serves as receiving matching template; every path demodulated signal is subjected to FRFT and narrow band matching correlation at corresponding peak value position and n path demodulated information are acquired, and high speed demodulation information are acquired by parallel-serial conversion.
Description
Technical field
The present invention relates to a kind of spectrum reuse technique, belong to the band resource multiplex technique field in the radio communication based on the fractional Fourier transform domain processing signals.
Background technology
In traditional communication system and since bandwidth limit the data that each path channels can only transmit given pace, when the data rate that will transmit during, this road signal can only be divided into the multiple signals transmission greater than maximum data rate.In cdma communication system, because spreading code has pseudo-orthogonality, therefore transmitting multiplex information simultaneously in a path channels, promptly different information utilizes different spreading codes to transmit signal separately in same channel.But the multiplexing restriction that is subjected to pseudo noise code quantity of the frequency spectrum resource of traditional CDMA technology in system can not realize the multiplexing of channel resource.
Summary of the invention
The present invention proposes a kind of modulation-demodulation method for fraction Fourier transform domain of unequal power spectral density for solving traditional multiplexing problem that is subjected to the restriction of pseudo noise code quantity of the frequency spectrum resource of CDMA technology in system.The present invention includes following steps:
Emission process:
Step 1, with binary digital information b (t) by string and be converted to n road signal b
n(t), wherein n represents natural number, b
n(t) expression b
1(t), b
2(t) ...;
Step 3, the n road signal b that step 1 is obtained
n(t) cut the general signal of carrier wave with the n road of step 2 acquisition and modulate, obtain n road modulation signal s
n(t), s wherein
n(t) expression s
1(t), s
2(t) ...;
Receiving course:
Step 5, the sum signal s (t) that receives is obtained n road restituted signal r by demodulation respectively
n(t), r wherein
n(t) expression r
1(t), r
2(t) ...;
Step 7, to every road restituted signal r
n(t) be p respectively
nRank and 2-p
nThe Fourier Transform of Fractional Order on rank, and at the corresponding peak value position place to do the arrowband coupling relevant with receiving matching template, obtain n road demodulating information b
n(t), at last by and string conversion obtain two-forty demodulating information b ' (t).
Beneficial effect: the present invention cuts the frequency modulation rate k value of general signal and realizes multiplexing to frequency spectrum resource by changing carrier wave, because basic thought of the present invention is to utilize the general signal of cutting of different frequency modulation rates that the character of best energy accumulating is arranged on corresponding different rank score field, therefore and other road signal does not have energy accumulating on this road demodulation exponent number, does narrow-band filtering at peak and can effectively avoid interference between multiplex (MUX); In addition and since the carrier signal cosine function of CDMA in the Fourier Transform of Fractional Order territory (territory beyond the frequency domain) can produce power not assemble, can realize realizing the multiplexing of channel resource by method of the present invention with the stack of CDMA signal.
Description of drawings
Fig. 1 is for realizing the transmitter architecture schematic diagram of the inventive method; Fig. 2 is for realizing the receiver structure schematic diagram of the inventive method; Fig. 3 and Fig. 4 arrange the spectrogram of multiple signals for adopting method of the present invention, and the abscissa of Fig. 3 is represented the frequency domain sample point, and ordinate is represented amplitude, and the abscissa of Fig. 4 is represented the score field sampled point, and ordinate is represented amplitude.
Embodiment
Embodiment one: referring to Fig. 1 to Fig. 4, present embodiment is made up of following steps:
Emission process:
Step 1, be that the binary digital information b (t) of nRbit/s obtains n road signal b by string and conversion with bit rate
n(t), the bit rate of every road signal is reduced to Rbit/s, and wherein n and R represent natural number, b
n(t) expression b
1(t), b
2(t) ...;
Step 3, the n road signal b that step 1 is obtained
n(t) modulate with the n letter Lu Qiepu signal of step 2 acquisition, obtain n road modulation signal s
n(t)=b
n(t) cos (2 π f
cT+k
nπ t
2), s wherein
n(t) expression s
1(t), s
2(t) ...;
Receiving course:
Step 5, the mixed signal s (t) that receives is obtained n road restituted signal r by demodulation respectively
n(t), r wherein
n(t) expression r
1(t), r
2(t) ...;
Step 7, to every road restituted signal r
n(t) be p respectively
nRank and 2-p
nThe Fourier Transform of Fractional Order on rank, and do the interference of relevant other signal of filtering of arrowband coupling with receiving matching template at the corresponding peak value position place, obtain n road demodulating information b
n(t), at last by and string conversion obtain two-forty demodulating information b ' (t).
Present embodiment is used and is cut the traditional cosine carrier signal of general signal substituting, utilize general signal has optimum energy capture on corresponding different fractional orders territory the characteristic of cutting of different frequency modulation rate k, by producing the multiple signals that centre frequency is identical, bandwidth is different is carrier wave, utilize the general signal of cutting of different bandwidth the different fractional order produce powers characteristic of assembling, reduce the phase mutual interference between each road signal.Be specially 1 tunnel two-forty signal is divided into the signal that multi-path low speed rate channel can transmit, the centre frequency of getting available frequency band is f
c, every road signal center frequency all is made as f
cBut use the carrier transmission of different bandwidth, the frequency modulation rate that different bandwidth is corresponding different, because the general signal of cutting of different frequency modulation rates has energy accumulating in different Fourier Transform of Fractional Order territories, and other road carrier signals are comparatively smooth at the waveform of this rank score field, therefore, separate the fractional fourier transform that timing is done different corresponding exponent numbers to received signal respectively, and it is relevant to make the arrowband near the peak value of correspondence, can effectively reduce the interference of other road signals to this road signal.
The cosine form cut general signal at the p rank of correspondence score field waveform, the peak value of energy accumulating appears at preceding half section of score field, the second half section is a flat portions comparatively; And in 2-p rank score field, peak value appears at the second half section of score field, and preceding half section is flat portions comparatively.Reason is the general signal exp[i of cutting of two conjugation (2 π f
0T+ π kt
2)] and exp[-i (2 π f
0T+ π kt
2)] transform to preceding half section and the second half section that are respectively waveform after the score field, both assemble on p rank and 2-p rank score field produce power respectively, therefore we are separating timing, utilize the energy accumulating characteristic of cutting general signal fractional Fourier territory, after will doing p rank and 2-p rank fractional fourier transform to signal, it is relevant to do coupling respectively near preceding half section peak with the second half section.
For example, at transmitting terminal, the transmission of one line information source is 001 signal, is respectively 0,0,1 signal by becoming 3 the tunnel after string and the conversion, and three tunnel signal rates are identical, are Rbit/s.Get the centre frequency f of usable spectrum
cBe the centre frequency of this three road signal, design 3 tunnel different signal bandwidths and be respectively B
1, B
2, B
3, determine the frequency modulation rate k of each road signal according to bit rate and bandwidth
1=B
1R, k
2=B
2R, k
3=B
3R determines that thus the carrier wave of three road signals is respectively cos (2 π f
cT+k
1π t
2), cos (2 π f
cT+k
2π t
2), cos (2 π f
cT+k
3π t
2).Modulating three the tunnel with three-channel carrier is 0,0,1 information source, obtains three road signals to be respectively-cos (2 π f
cT+k
1π t
2) ,-cos (2 π f
cT+k
2π t
2), cos (2 π f
cT+k
3π t
2), this three road signal is mixed the back launch by antenna.At receiving terminal, according to the parameter centre frequency f of three-channel carrier
c, frequency modulation rate k
nCan determine the fractional order p that this energy produce power of cutting general signal correspondence is assembled with bit rate R
n, 2-p
nReach peak in this two rank score field.According to three tunnel different parameter demodulation, the first via is p respectively with the signal that receives
1Rank and 2-p
1The rank fractional fourier transform obtains f
P1(u), f
2-p1(u), get cos (2 π f
cT+k
1π t
2) at p
1Rank and 2-p
1Near the peak value of rank waveform
Be template, with template and f
P1(u), f
2-p1(u) do coupling correlation intergal judgement after, obtain the demodulating information of the first via, other two paths of signals is demodulation in such a manner also.Because the general signal of cutting of different frequency modulation rates is assembled in different score field produce powers, so this demodulation method can effectively reduce the influence of other road signal to this road signal.
Claims (1)
1, a kind of modulation-demodulation method for fraction Fourier transform domain of unequal power spectral density is characterized in that it may further comprise the steps:
Emission process:
Step 1, with binary digital information b (t) by string and be converted to n road signal b
n(t), wherein n represents natural number, b
n(t) expression b
1(t), b
2(t) ...;
Step 2, produce n road centre frequency f at transmitting terminal
cIdentical and bandwidth is different cuts general carrier signal, every road signal bandwidth is B
n, frequency modulation rate k
n=B
n/ T=B
nR;
Step 3, the n road signal b that step 1 is obtained
n(t) cut the general signal of carrier wave with the n road of step 2 acquisition and modulate, obtain n road modulation signal s
n(t), s wherein
n(t) expression s
1(t), s
2(t) ...;
Step 4, the n road modulation signal s that step 3 is obtained
n(t) addition, and with sum signal s (t) emission that obtains;
Receiving course:
Step 5, the sum signal s (t) that receives is obtained n road restituted signal r by demodulation respectively
n(t), r wherein
n(t) expression r
1(t), r
2(t) ...;
Step 6, according to every road restituted signal r
n(t) centre frequency f
cWith frequency modulation rate k
n, obtain the fractional order p of every road restituted signal correspondence
nAnd 2-p
nAnd at the score field peak on reciprocal fraction rank, and the arrowband of peak blocked waveform
With
As receiving matching template;
Step 7, to every road restituted signal r
n(t) be p respectively
nRank and 2-p
nThe Fourier Transform of Fractional Order on rank, and at the corresponding peak value position place to do the arrowband coupling relevant with receiving matching template, obtain n road demodulating information b
n(t), at last by and string conversion obtain two-forty demodulating information b ' (t).
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|---|---|---|---|
| CNA2008102096342A CN101431496A (en) | 2008-12-08 | 2008-12-08 | Modulation-demodulation method for fraction Fourier transform domain with unequal power spectral density |
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|---|---|---|---|
| CNA2008102096342A CN101431496A (en) | 2008-12-08 | 2008-12-08 | Modulation-demodulation method for fraction Fourier transform domain with unequal power spectral density |
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Family
ID=40646664
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101827060A (en) * | 2010-03-30 | 2010-09-08 | 北京理工大学 | Adaptive modulation-demodulation method base on fractional order Fourier transform |
| CN101667911B (en) * | 2009-09-25 | 2012-05-23 | 北京理工大学 | Secret communication method based on fraction order Fourier transform order-multiplexing |
-
2008
- 2008-12-08 CN CNA2008102096342A patent/CN101431496A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101667911B (en) * | 2009-09-25 | 2012-05-23 | 北京理工大学 | Secret communication method based on fraction order Fourier transform order-multiplexing |
| CN101827060A (en) * | 2010-03-30 | 2010-09-08 | 北京理工大学 | Adaptive modulation-demodulation method base on fractional order Fourier transform |
| CN101827060B (en) * | 2010-03-30 | 2012-07-04 | 北京理工大学 | Adaptive modulation-demodulation method base on fractional order Fourier transform |
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Open date: 20090513 |