CN101651653A - Peak clipping method for multi-carrier frequency hopping communication system - Google Patents

Abstract

The invention discloses a peak clipping method for a multi-carrier frequency hopping communication system, which is characterized by comprising the following real-time steps: (1) judging whether the signal bandwidth in the present moment is changed or not relative to the previous moment, if so, executing the step (3), otherwise, executing the step (2); (2) calculating a frequency difference of thepresent system signal and a center frequency point in the previous adjacent moment, carrying out frequency shift on a filter by the frequency difference so that the center frequency point is consistent with the present system signal and skipping to execute the step (4); (3) reconstructing the filter demanded by the digital bandwidth, the center frequency point and a spectrum template meeting thepresent system signal and executing the step (4); (4) constructing a peak clipping pulse, aligning to a peak value of the system signal by a peak value in response to a filter pulse and subtracting the peak clipping pulse by the system signal. The peak clipping method for the multi-carrier frequency hopping communication system can self-adaptively adjust the filter coefficient for constructing thepeak clipping pulse according to the carrier frequency point change of the system, thereby ensuring that the peak clipping effect is better than a traditional process.

Description

Peak clipping method for multi-carrier frequency hopping communication system

Technical field

The present invention relates to be applied in a kind of peak clipping method for multi-carrier frequency hopping communication system in the frequency-hopping communication system of GSM and EDGE and so on.

Background technology

In existing main flow mobile communication system, GSM and EDGE are typical case's representatives of multi-carrier frequency hopping communication system.

Multicarrier system is than single-carrier system, because the stack of a plurality of carrier signals on time domain, it has higher peak-to-average power ratio (PAPR).Signal for undistorted these high peak-to-average power ratios of transmission, linearity to some parts (as power amplifier) requires very high, if the excursion of signal exceeds the range of linearity of device, then can produce tangible inband distortion and out-of-band radiation, thereby cause the rising of the error rate.So the size of signal peak-to-average power power ratio has direct influence to the multicarrier system performance.Therefore, the peak-to-average power ratio that reduces system effectively just seems very necessary, and this will be directly connected to the performance of whole system and realize cost.

Frequency hopping is exactly to change the channel frequency that a carrier signal is occupied randomly by frequency hop sequences, promptly changes the technology of the center frequency point of carrier wave.Each frequency hop sequences should be a quadrature in a channel-group, and each channel can not collide in the frequency hopping transmission course.Frequency hopping can reduce the influence of multipath Rayleigh decline to signal, improves error performance, receives the effect of frequency diversity.Another effect of frequency hopping is an interference diversity.Co-channel interference in the cellular cell because incoherent frequency hopping has been separated the strong jamming from many sub-districts, has alleviated the near-far interference influence effectively.In addition, frequency hopping makes the more randomization of air interface message transmission, has improved the mobile radio system fail safe.

In sum, the multicarrier frequency-hopping system has following characteristics:

1) higher peak-to-average power ratio (PAPR);

2) center frequency point of each carrier wave is along with the time changes by frequency hop sequences;

3) system bandwidth and system centre frequency corresponding change along with the variation of each carrier wave center frequency point.

Therefore, when the despicking method of design multi-carrier frequency hopping communication system, need consider the characteristics of this system, could more effectively reduce the peak-to-average power ratio (PAPR) of multi-carrier frequency hopping communication system.

Existing a kind of PC peak clipping algorithm can effectively reduce the peak-to-average power ratio of system, its cardinal principle generates the peak clipping pulse for utilizing the filter impulse responses that has with input signal same frequency spectrum template (Spectrum Mask), and the point that surpasses the amplitude threshold value in the input signal is carried out peak clipping.Principle as depicted in figs. 1 and 2.

Last figure among Fig. 1 is the time-domain signal amplitude curve, and Ath is the amplitude thresholding, and A is detected peak amplitude; Figure below among Fig. 1 is the good peak clipping pulse of structure.

Detect the input signal peak value earlier, filter impulse responses is shifted, make its peak value and detected signal peak position alignment, if the filter impulse responses that have with input signal same frequency spectrum template (Spectrum Mask) this moment is H (n), 1≤n≤L, n and L are integer, and L represents the exponent number of filter impulse responses, utilize formula (1) to construct the peak clipping pulse:

CP_val(n)＝(A-Ath)*e ^jθ*H(n)，1≤n≤L (1)

Wherein e is the truth of a matter of natural logrithm, and j is the imaginary part of symbol, $j=\sqrt{-1},$ θ is the phase place of signal peak, e ^{J θ}=cos θ+jsin θ.Deduct the peak clipping pulse with primary signal, the visible Fig. 2 of result after having constructed the peak clipping pulse.

As seen from Figure 2, the peak value that surpasses amplitude threshold value Ath is cut below the threshold value, and the peak value under cutting is slick and sly, and this is because the spike of filter impulse responses is slick and sly, so this algorithm has spectral performance preferably than other peak clipping algorithm.

PC peak clipping algorithm advantage is:

1) can reduce the peak-to-average power ratio of input signal effectively;

2) owing to use the filter impulse responses that has with input signal same frequency spectrum template (Spectrum Mask) to carry out peak clipping, therefore the out-of-band noise of introducing is very little;

3) compare with other despicking method, this algorithm is little to EVM (error vector magnitude) performance impact of signal.

Because this algorithm adopts the filter pulse to come peak clipping, just need be before carrying out the peak clipping processing that filter coefficient setting is good, this is constant in the carrier wave center frequency point, fairly simple when realizing in the constant communication system (for example WiMAX system) of bandwidth, only need to have directly to configure and get final product with the corresponding filter coefficient of input signal spectrum template.

But, frequency-hopping communication system for GSM and EDGE and so on, its carrier wave center frequency point and system bandwidth are times to time change, the spectral characteristic of filter also should change with the change of signal spectral characteristic in this case, therefore, filter coefficient should not be well-determined, and should be variable.

This need propose the solution that suitable self adaptation is regulated filter system at multi-carrier frequency hopping communication system in the industry with regard to inevitable requirement, so that filter can construct the peak clipping operation that peak clipping pulse preferably is used to finish signal.

Summary of the invention

The objective of the invention is at the deficiencies in the prior art, a kind of peak clipping method for multi-carrier frequency hopping communication system is provided, by the coefficient of the filter of self adaptation adjusting in time in frequency-hopping communication system peak clipping process, handle input signal is carried out effective peak clipping so that accurately make up the peak clipping pulse.

For realizing this purpose, the present invention takes following technical scheme:

Peak clipping method for multi-carrier frequency hopping communication system of the present invention by the coefficient of the filter of self adaptation adjusting in time in frequency-hopping communication system peak clipping process, accurately makes up the peak clipping pulse input signal is carried out effective peak clipping processing, comprises following real-time step:

1) utilize the Serial No. of the system signal of current input to judge whether the signal bandwidth of current time changes with respect to last adjacent moment, if change then redirect execution in step 3), otherwise execution in step 2);

2) frequency difference of the center frequency point of current system signal of calculating and last adjacent moment is utilized this frequency difference that filter is carried out the shift frequency processing center frequency point of its center frequency point and current system signal is consistent, redirect execution in step 4);

3) re-construct the filter that the digital bandwidth, center frequency point and the spectrum mask that satisfy current system signal requires, execution in step 4);

4) construct the peak clipping pulse after, the peak value with the peak value alignment system signal of filter impulse responses deducts the peak clipping pulse with system signal.

More specifically, using following formula step 2) utilizes frequency difference to carry out shift frequency:

$H^{t_{k+1}}\left(n\right)=H^{t_k}\left(n\right)*e^{j*\mathrm{\Δ\ω}*n},1\≤n\≤L_{t_{k+1}},L_{t_{k+1}}=L_{t_k},$

Wherein, k is an integer, t _kWith t _K+1Represent former and later two adjacent moment respectively, Δ ω is the frequency difference of former and later two center frequency point,

Filter impulse responses Serial No. before and after the expression shift frequency, n is an integer, the sequence number of expression filter impulse responses Serial No., L represents filter order.

Step 2) in, when described frequency difference is zero, need not carry out shift frequency, filter impulse responses remains unchanged, redirect execution in step 4).

According to one embodiment of present invention, the filter that re-constructs in the step 3) is a band pass filter, and its digital bandwidth, center frequency point and spectrum mask all satisfy the requirement of current system signal.

Disclose according to preferred embodiment of the present invention, construct digital bandwidth and spectrum mask in the step 3) in advance and satisfy the low pass filter of current system signal requirement, and then handle the center frequency point of this low pass filter moved to the center frequency point with current system signal from zero-frequency by shift frequency and be consistent, low pass filter is transformed to band pass filter.

This preferable being implemented in the described step 3), the concrete steps of structure low pass filter are as follows:

3.1, determine to approach desirable frequency response function H with following formula _d(e ^{J ω}):

$H_d\left(e^{\mathrm{j\&omega;}}\right)=\left\{\begin{array}{cc}{e}^{-\mathrm{j\&omega;a}},& 0\&le;\left|\mathrm{\&omega;}\right|\&le;{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="A2009101924080017H2.png"\; state="\{\{state\}\}">c</figure-callout>}}\\ 0,& {\mathrm{\&omega;}}_c<\left|\mathrm{\&omega;}\right|\end{array}\right.,$

Wherein, ω is normalized numerical frequency, ω _cBeing the digital bandwidth of system signal, also is the normalization bandwidth of filter spectrum characteristic, and d is the identifier of the low pass filter that rebuilds;

3.2, L is the exponent number of low pass filter, establishes α=(L-1)/2, obtain with following formula and approach perfect low pass impulse response H _d(n):

$H_d\left(n\right)=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-\mathrm{\&pi;}}^{\mathrm{\&pi;}}{H}_d\left(e^{\mathrm{j\&omega;}}\right)e^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}$

$=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-{\mathrm{\&omega;}}_c}^{{\mathrm{\&omega;}}_c}{e}^{-\mathrm{j\&omega;\&alpha;}}{e}^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})},0\&le;n\&le;L-1,$

N is an integer, the sequence number of expression low pass filter impulse response Serial No.;

3.3, determine a window function type, estimation window function length is filter order L, calculates window function coefficient win (n), 0≤n≤L-1 according to the window function expression formula;

3.4, calculate the filter impulse responses of current time by following formula

$H_d^{t_{k+1}}\left(n\right)=H_d\left(n\right)*\mathrm{win}\left(n\right)=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})}*\mathrm{win}\left(n\right),0\&le;n\&le;L-1,$

t _K+1Identifier for current time;

After finishing above-mentioned steps, form and satisfy the digital bandwidth of current system signal and the low pass filter that spectrum mask requires.

Described window function can in rectangular window, triangular window, Hanning window, hamming window, Blackman window and the kaiser window any one, but be not limited to described severally, all known window functions can be adopted by the present invention.

In addition, in the described step 3), adopt following formula to carry out shift frequency and handle:

$H^{t_{k+1}}\left(n\right)={H_d}^{t_{k+1}}\left(n\right)*e^{j*{\mathrm{\&omega;}}_{\mathrm{center}}\left(t_{k+1}\right)*n},1\&le;n\&le;L_{t_{k+1}},$

Wherein, ω _Center(t _K+1) be current time system signal center frequency point,

Be the filter impulse responses Serial No. before and after the shift frequency.

In the described step 4), adopt following formula construction peak clipping pulse:

$\mathrm{CP}\_\mathrm{val}\left(n\right)=(A-\mathrm{Ath})*e^{\mathrm{j\&theta;}}*H^{t_{k+1}}\left(n\right),1\&le;n\&le;L_{t_{k+1}}$

Wherein, A is detected peak amplitude, and Ath is the amplitude thresholding of peak value, and e is the truth of a matter of natural logrithm, and j is the imaginary part of symbol, $j=\sqrt{-1},$ θ is the phase place of signal peak, e ^{J θ}=cos θ+jsin θ, n are integer, $1\&le;n\&le;L_{t_{k+1}}.$

Compared with prior art, the present invention has following advantage:

1, carries out signal processing with the thinking of digitized processing, be suitable for programming realization in the digit chip such as FPGA, DSP;

2, by the relatively digital bandwidth of former and later two adjacent moment and the variation of centre frequency, make response in real time, immediately carry out the frequency translation operation under the situation constant in bandwidth, that center frequency point changes, when changing, bandwidth then makes it to adapt to current system signal by rebuilding filter, in other words, the coefficient that guarantees filter can be realized the self adaptation adjustment, handle with the continuity that guarantees system signal, thereby make filter can construct the peak clipping pulse exactly, guarantee system signal is carried out premium properties after the peak clipping;

3, utilize the characteristic of frequency difference between band pass filter and the low pass filter, both allowed to reach the purpose of upgrading filter coefficient by direct structure band pass filter, also allow to be converted to band pass filter and reach identical purpose, further guaranteed the peak clipping effect of multicarrier frequency-hopping system and handled flexibility by the capable again shift frequency of elder generation's structure low pass filter.

Description of drawings

Fig. 1 is that the signal peak of traditional despicking method detects the waveform schematic diagram with the peak clipping pulse;

Fig. 2 is the signal power curve synoptic diagram of despicking method before and after peak clipping of Fig. 1;

Fig. 3 is the spectrum diagram of multi-carrier communications systems.

Embodiment

Followingly describe in conjunction with the accompanying drawings and embodiments:

Peak clipping method for multi-carrier frequency hopping communication system of the present invention is fit to be integrated in FPGA (Field Programmable Gate Array with the form of program; field programmable gate array); DSP (Digital SignalProcessor; digital signal processor) in and so on the digit chip; this chip is widely used in the mobile communication system; thereby have representative widely; be used to auxiliary the elaboration in the present embodiment; but; known other of those skilled in the art has the digit chip of programmability, and is developed out the new digital chip with equal capability in the future and should be excluded outside protection scope of the present invention.

For multi-carrier frequency hopping communication system, the center frequency point of its each carrier wave is along with the time changes by frequency hop sequences, and system bandwidth and system centre frequency be corresponding the change along with the variation of each carrier wave center frequency point.Therefore, the filter impulse responses that is used to generate the peak clipping pulse should have the function that self adaptation is regulated.Peak clipping method for multi-carrier frequency hopping communication system of the present invention just is being based on this and is proposing.

For the convenience of follow-up statement, at first introduce the related system parameters of multi-carrier frequency hopping communication system.This paper is that example is set forth content of the present invention with N carrier jumping frequency communication system, and N is the integer greater than 1.In the time period that each carrier frequency does not change, a N carrier jumping frequency communication system is a common N carrier communication system, and its spectrum diagram as shown in Figure 3.The ordinate of Fig. 3 is power spectral density P _ω, abscissa is normalized numerical frequency ω:

$\mathrm{\&omega;}=\frac{f}{f_s}\&CenterDot;2\mathrm{\&pi;}$

Wherein, f represents analog frequency, f _sThe sample rate of expression system.The carrier wave digital bandwidth of every carrier wave all is B among Fig. 3, and the digital center frequency of each carrier wave is followed successively by ω from left to right ₁, ω ₂... ω _NThe system digits bandwidth of multi-carrier communications systems illustrated in Figure 3 is B _W, B _W=ω _N-ω ₁+ B, the digital center frequency of system is ω _Center, ω _Center=(ω ₁+ ω _N)/2.It needs to be noted when B＜＜B _WThe time, B _W≈ ω _N-ω ₁

For N carrier jumping frequency communication system, the center frequency point of each above-mentioned carrier wave is along with the time changes by frequency hop sequences, and system digits bandwidth and system digits center frequency point be corresponding the change along with the variation of each carrier wave center frequency point, promptly all is the function of time t: ω ₁(t), ω ₂(t) ... ω _N(t), B _W(t)=ω _N(t)-ω ₁(t)+and B, ω _Center(t)=[ω ₁(t)+ω _N(t)]/2.

Suppose t _k, t _K+1Be adjacent two moment (k is an integer, only plays sign effect constantly, as k=0, down together) of carrier frequency point saltus step, its corresponding system parameters is respectively:

1) t _kConstantly:

Carrier frequency point: ω ₁(t _k), ω ₂(t _k) ... ω _N(t _k),

System digits bandwidth: B _W(t _k)=ω _N(t _k)-ω ₁(t _k)+B,

System digits center frequency point: ω _Center(t _k)=[ω ₁(t _k)+ω _N(t _k)]/2.

2) t _K+1Constantly:

Carrier frequency point: ω ₁(t _K+1), ω ₂(t _K+1) ... ω _N(t _K+1),

System digits bandwidth: B _W(t _K+1)=ω _N(t _K+1)-ω ₁(t _K+1)+B,

System digits center frequency point: ω _Center(t _K+1)=[ω ₁(t _K+1)+ω _N(t _K+1)]/2.

System initial state can be regarded t as _kFor negative infinite, t _K+1Be the special circumstances in 0 moment.

Suppose at t _kConstantly, according to the system digits bandwidth B _W(t _k), system digits center frequency point ω _Center(t _k) and filter impulse responses that require to set of system spectrum template be

$1\&le;n\&le;L_{t_k},$ N and

Be integer,

The exponent number of expression filter this moment.

From t _kThe time be carved into t _K+1Constantly, variation has taken place in the carrier frequency point of system, the filter impulse responses of this moment

Also need to make corresponding change, $1\&le;n\&le;L_{t_{k+1}},$ N and

Be integer,

The exponent number of expression filter this moment.

The method that filter impulse responses changes is as follows:

1) judges at first whether the system digits bandwidth changes, i.e. B _W(t _K+1) whether equal B _W(t _k), if equate then execution in step 2), otherwise redirect execution in step 3);

2) the system digits bandwidth did not both change, and calculated two frequency difference Δ ω=ω of system digits center frequency point constantly at once _Center(t _K+1)-ω _Center(t _k).

If Δ ω ≠ 0, then the system digits center frequency point changes, utilizes following formula to carry out shift frequency, and the center frequency point that the center frequency point of filter impulse responses is moved to current system signal is consistent:

$H^{t_{k+1}}\left(n\right)=H^{t_k}\left(n\right)*e^{j*\mathrm{\&Delta;\&omega;}*n},1\&le;n\&le;L_{t_{k+1}},L_{t_{k+1}}=L_{t_k},$

Otherwise if Δ ω=0, then system digits bandwidth and system digits center frequency point all do not change, and still adopt original filter impulse responses, that is:

$H^{t_{k+1}}\left(n\right)=H^{t_k}\left(n\right),1\&le;n\&le;L_{t_{k+1}};$

After above-mentioned two kinds of situations are processed, finish shift frequency work, just can jump to step 4) and carry out concrete peak clipping operation;

3) when system bandwidth changes, satisfy the system digits bandwidth B according to multiple low pass filter design method design known in the field _W(t _K+1) and the low pass filter impulse response that requires of system spectrum template, obtain ${H_d}^{t_{k+1}}\left(n\right),1\&le;n\&le;L_{t_{k+1}},$ Because the filter of design is a low pass filter, its digital center frequency is a zero-frequency, it need be removed frequently the extremely system digits center frequency point ω of the system signal of this moment _Center(t _K+1), form the band pass filter that is fit to the present invention's use, promptly carry out following formula:

$H^{t_{k+1}}\left(n\right)={H_d}^{t_{k+1}}\left(n\right)*e^{j*{\mathrm{\&omega;}}_{\mathrm{center}}\left(t_{k+1}\right)*n},1\&le;n\&le;L_{t_{k+1}}.$

Like this, guarantee that just the system digits center frequency point of the filter re-construct is consistent with the digital center frequency of current system signal, can further carry out the peak clipping of step 4) and operate.

4) present embodiment is because of being optimized based on traditional despicking method, in step 2) or 3) in be met the filter impulse responses of current system bandwidth and spectrum requirement

Afterwards, the mode of structure peak clipping pulse and peak clipping is identical with the mode in traditional despicking method, promptly detects the input signal peak value, and filter impulse responses is shifted, make its peak value and detected signal peak position alignment, construct the peak clipping pulse then and carry out peak clipping.

Thereby, its cardinal principle remains utilizes the impulse response (also being filter coefficient) of the filter identical with spectrum mask (Spectrum Mask) with the system digits bandwidth of input signal to generate the peak clipping pulse, and the point that surpasses default amplitude threshold value in the original system signal is carried out peak clipping.So can consult the method for the known structure peak clipping pulse that Fig. 1 and Fig. 2 disclose, the equation of structure peak clipping pulse is same as the formula that background technology is quoted:

$\mathrm{CP}\_\mathrm{val}\left(n\right)=(A-\mathrm{Ath})*e^{\mathrm{j\&theta;}}*H^{t_{k+1}}\left(n\right),1\&le;n\&le;L_{t_{k+1}}$

Wherein, A is detected peak amplitude, and Ath is the amplitude thresholding of peak value, and e is the truth of a matter of natural logrithm, and j is the imaginary part of symbol, $j=\sqrt{-1},$ θ is the phase place of signal peak, e ^{J θ}=cos θ+jsin θ, n are integer, $1\&le;n\&le;L_{t_{k+1}},$ t _K+1Only play the sign effect, be used to represent current time.

For making elaboration of the present invention more readable, now further disclose the substep more specifically of step 3):

3.1, at first determine to approach perfect low pass frequency response function H by following formula _d(e ^{J ω}):

$H_d\left(e^{\mathrm{j\&omega;}}\right)=\left\{\begin{array}{cc}{e}^{-\mathrm{j\&omega;a}},& 0\&le;\left|\mathrm{\&omega;}\right|\&le;{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="A2009101924080017H2.png"\; state="\{\{state\}\}">c</figure-callout>}}\\ 0,& {\mathrm{\&omega;}}_c<\left|\mathrm{\&omega;}\right|\end{array}\right.,$

ω wherein _cBe the digital bandwidth of signal, i.e. the normalization bandwidth of filter spectrum characteristic, d is the identifier of the low pass filter that rebuilds;

3.2, because of filter order is L, establish α=(L-1)/2, then obtain and approach perfect low pass impulse response H by following formula _d(n):

$H_d\left(n\right)=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-\mathrm{\&pi;}}^{\mathrm{\&pi;}}{H}_d\left(e^{\mathrm{j\&omega;}}\right)e^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}$

$=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-{\mathrm{\&omega;}}_c}^{{\mathrm{\&omega;}}_c}{e}^{-\mathrm{j\&omega;\&alpha;}}{e}^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})},0\&le;n\&le;L-1;$

3.3, select the window function type then, several window functions commonly used have: rectangular window, triangular window, peaceful (Hanning) window of the Chinese, hamming (Hamming) window, Blacknam (Blackman) window, kayser (Kaiser) window, the expression formula of these window functions is well known in the art, so not all right giving unnecessary details;

3.4, window function length is filter order L, obtains window function coefficient win (n) according to the window function expression formula, 0≤n≤L-1, calculate wave digital lowpass filter impulse response (being filter coefficient) by following formula:

$H_d^{t_{k+1}}\left(n\right)=H_d\left(n\right)*\mathrm{win}\left(n\right)=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})}*\mathrm{win}\left(n\right),0\&le;n\&le;L-1.$

Need further be pointed out that, it below only is preferred embodiment of the present invention, it adopts and makes up low pass filter in advance and then its shift frequency is realized that the method for band pass filter realizes, but abovementioned steps 3), also can satisfy the band pass filter realization of system signal digital bandwidth, digital center frequency and spectrum mask requirement by direct structure.In addition, the method for structure low pass filter is not subjected to above-mentioned listed restriction yet.Those skilled in the art should draw inferences about other cases from one instance after reading over the present invention, and by the mode of multiple equivalence replacement, and the present invention is for for purpose of brevity, to respectively knowing not all right the giving unnecessary details of known equivalent replacement step.

In sum, peak clipping method for multi-carrier frequency hopping communication system of the present invention can change and the self adaptation adjustment is used to construct the filter coefficient of peak clipping pulse according to the system carrier frequency, thereby guarantee that the peak clipping effect is better than conventional art.

Claims (9)

1, a kind of peak clipping method for multi-carrier frequency hopping communication system, coefficient by the filter of self adaptation adjusting in time in frequency-hopping communication system peak clipping process, accurately make up the peak clipping pulse input signal carried out effective peak clipping processing, it is characterized in that, comprise following real-time step:

1) utilize the Serial No. of the system signal of current input to judge whether the signal bandwidth of current time changes with respect to last adjacent moment, if change then redirect execution in step 3), otherwise execution in step 2);

2) frequency difference of the center frequency point of current system signal of calculating and last adjacent moment is utilized this frequency difference that filter is carried out the shift frequency processing center frequency point of its center frequency point and current system signal is consistent, redirect execution in step 4);

3) re-construct the filter that the digital bandwidth, center frequency point and the spectrum mask that satisfy current system signal requires, execution in step 4);

4) construct the peak clipping pulse after, the peak value with the peak value alignment system signal of filter impulse responses deducts the peak clipping pulse with system signal.

2, peak clipping method for multi-carrier frequency hopping communication system according to claim 1 is characterized in that step 2) in use following formula and utilize frequency difference to carry out shift frequency:

$H^{t_{k+1}}\left(n\right)=H^{t_k}\left(n\right)*e^{j*\mathrm{\&Delta;\&omega;}*n},1\&le;n\&le;L_{t_{k+1}},L_{t_{k+1}}=L_{t_k},$

Wherein, k is an integer, t _kWith t _K+1Represent former and later two adjacent moment respectively, Δ ω is the frequency difference of former and later two center frequency point,

Filter impulse responses Serial No. before and after the expression shift frequency, n is an integer, the sequence number of expression filter impulse responses Serial No., L represents filter order.

3, peak clipping method for multi-carrier frequency hopping communication system according to claim 1 is characterized in that: step 2) in, when described frequency difference is zero, need not carry out shift frequency, filter impulse responses remains unchanged, redirect execution in step 4).

4, according to any described peak clipping method for multi-carrier frequency hopping communication system in the claim 1 to 3, it is characterized in that: the filter that re-constructs in the step 3) is a band pass filter, and its digital bandwidth, center frequency point and spectrum mask all satisfy the requirement of current system signal.

5, according to any described peak clipping method for multi-carrier frequency hopping communication system in the claim 1 to 3, it is characterized in that: construct the low pass filter that digital bandwidth and spectrum mask satisfy current system signal requirement in the step 3) in advance, and then handle the center frequency point of this low pass filter moved to the center frequency point with current system signal from zero-frequency by shift frequency and be consistent, low pass filter is transformed to band pass filter.

6, peak clipping method for multi-carrier frequency hopping communication system according to claim 5 is characterized in that, in the described step 3), the concrete steps of structure low pass filter are as follows:

3.1, determine to approach desirable frequency response function H with following formula _d(e ^{J ω}):

$H_d\left(e^{\mathrm{j\&omega;}}\right)=\left\{\begin{array}{cc}{e}^{-\mathrm{j\&omega;a}},& 0\&le;\left|\mathrm{\&omega;}\right|\&le;{\mathrm{\&omega;}}_c\\ 0,& {\mathrm{\&omega;}}_c<\left|\mathrm{\&omega;}\right|\end{array}\right.,$

Wherein, ω is normalized numerical frequency, ω _cBeing the digital bandwidth of system signal, also is the normalization bandwidth of filter spectrum characteristic;

3.2, L is the exponent number of low pass filter, establishes α=(L-1)/2, obtain with following formula and approach perfect low pass impulse response H _d(n):

$H_d\left(n\right)=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-\mathrm{\&pi;}}^{\mathrm{\&pi;}}{H}_d\left(e^{\mathrm{j\&omega;}}\right)e^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}$

$=\frac{1}{2\mathrm{\&pi;}}{\&Integral;}_{-{\mathrm{\&omega;}}_c}^{{\mathrm{\&omega;}}_c}{e}^{-\mathrm{j\&omega;\&alpha;}}{e}^{\mathrm{j\&omega;n}}\mathrm{d\&omega;}=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})}0\&le;n\&le;L-1,$

N is an integer, the sequence number of expression low pass filter impulse response Serial No., and d is the identifier of the low pass filter that rebuilds;

3.3, determine a window function type, estimation window function length is filter order L, calculates window function coefficient win (n), 0≤n≤L-1 according to the window function expression formula;

3.4, calculate the filter impulse responses of current time by following formula

$H_d^{t_{k+1}}\left(n\right)=H_d\left(n\right)*\mathrm{win}\left(n\right)=\frac{\sin \left[{\mathrm{\&omega;}}_c(n-\mathrm{\&alpha;})\right]}{\mathrm{\&pi;}(n-\mathrm{\&alpha;})}*\mathrm{win}\left(n\right),0\&le;n\&le;L-1,$

t _K+1Identifier for current time;

After finishing above-mentioned steps, form and satisfy the digital bandwidth of current system signal and the low pass filter that spectrum mask requires.

7, peak clipping method for multi-carrier frequency hopping communication system according to claim 6 is characterized in that: described window function be in rectangular window, triangular window, Hanning window, hamming window, Blackman window and the kaiser window any one.

8, peak clipping method for multi-carrier frequency hopping communication system according to claim 1 is characterized in that, in the described step 3), adopts following formula to carry out shift frequency and handles:

$H^{t_{k+1}}\left(n\right)={H_d}^{t_{k+1}}\left(n\right)*e^{j*{\mathrm{\&omega;}}_{\mathrm{center}}\left(t_{k+1}\right)*n},1\&le;n\&le;L_{t_{k+1}},$

Wherein, ω _Center(t _K+1) be current time system signal center frequency point,

Be the filter impulse responses Serial No. before and after the shift frequency.

9, window type peak clipping method according to claim 1 is characterized in that, in the described step 4), adopts following formula construction peak clipping pulse:

$\mathrm{CP}\_\mathrm{val}\left(n\right)=(A-\mathrm{Ath})*e^{\mathrm{j\&theta;}}*H^{t_{k+1}}\left(n\right),1\&le;n\&le;L_{t_{k+1}}$

Wherein, A is detected peak amplitude, and Ath is the amplitude thresholding of peak value, and e is the truth of a matter of natural logrithm, and j is the imaginary part of symbol,

θ is the phase place of signal peak, e ^{J θ}=cos θ+jsin θ, n are integer,

Images