CN102801673B - Quick carrier synchronizing method for FSK signal coherent demodulation - Google Patents

Abstract

The invention discloses a quick carrier synchronizing method for FSK (Frequency Shift Key) signal coherent demodulation, which comprises the steps: 1) carrying out a demodulating operation for a received lead sequence by using a lead sequence waveform generated locally or pre-stored when a receiver detects that the lead sequence arrives in a transmission process of a physical layer to obtain a single-frequency signal with continuous phase; 2) estimating the frequency and phase of the section of the single-frequency signal through estimation of the frequency and phase of the single-frequency signal; and 3) eliminating the frequency deviation and phase of a received frame to obtain a received signal with synchronized carrier according to the estimated value. In the transmission process of the physical layer, after the lead sequence is received, the frequency deviation and phase information comprised in the received lead sequence is adequately extracted and the frequency deviation and phase are applied to compensation of the frequency deviation and phase of all received data by current frame so that coherent demodulation can be possibly applied to the receiver, thereby, the overall receiving performance of the receiver is further improved.

Description

For a kind of Fast carrier synchronous method of fsk signal coherent demodulation

Technical field

The present invention relates to a kind of a kind of Fast carrier synchronous method for fsk signal coherent demodulation, belong to wireless communication transmission technique field.

Background technology

In existing near radio networked physics layer transmission technology, the transmitting-receiving of information often adopts in units of physical layer frame, and uses the mode of burst transfer to communicate.In the frame structure of physical layer, the beginning of frame all uses the frame head (targeting sequencing/homing sequence) appointed in advance to receiver, represents the beginning of data division in a frame.Receiver uses the appearance of specific this frame head of electric circuit inspection, and it is synchronous to complete with the data beginning in frame.In wireless FSK communication, average frame length is only about 20 bytes, because frame head only detects with presence or absence of frame synchronization and signal, therefore noncoherent demodulation mode is usually used to carry out demodulation to data, the method of well-known non-coherent demodulation about has the loss of 3dB than the method performance of coherent demodulation, but because it is without the need to recovering carrier phase, make comparatively simple, be therefore in industry widely used.Although use noncoherent demodulation mode insensitive to carrier phase mismatch, but carrier wave frequency deviation still can cause the hydraulic performance decline of non-coherent demodulation, this still needs extra circuit to compensate, to ensure that frequency deviation is at certain scope inner receiver property retention substantially constant.More than can be summarized as: the information containing carrier wave frequency deviation and phase place in frame head, but prior art not in addition extraction and application well, cause the method for reseptance that this performance of non-coherent demodulation can only be used poor compared with coherent demodulation.If use the method receiver of coherent demodulation all will will be significantly improved in antinoise, anti-multipath, transmission range and receiving sensitivity.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of Fast carrier synchronous method for fsk signal coherent demodulation.

The present invention proposes when receiver detects that frame head arrives, the frame head waveform using this locality to prestore goes modulation operations to the frame head waveform received, use filter filter away high frequency noise, obtain the simple signal of a Phase Continuation, the frequency of this simple signal and phase place are current carrier wave frequency deviation and phase error.By using the method for various possible simple signal frequency and phase estimation, estimating frequency and the phase place of this section of simple signal, drawing carrier wave frequency deviation and the phase error of present frame.Simultaneously, because the frame length of burst transfer is each time all very short, in same frame, carrier wave frequency deviation and phase place can be thought does not have to change, therefore the carrier wave frequency deviation estimated more than using and phase error are applied to current received frame, can think and accomplish carrier synchronization, and then can coherent demodulation be carried out, to reach better receptivity.

For solving the problems of the technologies described above, the invention provides a kind of a kind of Fast carrier synchronous method for fsk signal coherent demodulation, it is characterized in that, comprise following steps:

1) in physical layer transmission process, receiver is when detecting that the targeting sequencing of sampled signal arrives, use, with the local targeting sequencing waveform produced or prestore, modulation operations is gone to the targeting sequencing waveform received, obtain the simple signal of a Phase Continuation;

2) by estimating frequency and the phase place of this section of simple signal to the method for simple signal frequency and phase estimation;

3) eliminate frequency deviation and the phase place of received frame according to this estimated value, obtain the Received signal strength of carrier synchronization.

Coherent demodulation method is used to carry out demodulation to the Received signal strength of carrier synchronization.

The step of the simple signal that obtains after going to modulate being carried out to filtering is also comprised in step 1).

To the estimation of simple signal frequency and phase place with eliminate the carrier wave frequency deviation of Received signal strength and the process of phase deviation is:

Filtered simple signal is sent into targeting sequencing detection/synchronization module simultaneously, carrier wave (frequency deviation/phase place) is estimated and correct module;

Targeting sequencing detection/synchronization module provides the synchronous indicating signal of leading symbol in time when detecting that sampled data meets the characteristic of targeting sequencing, carrier wave (frequency deviation/phase place) is estimated and is corrected the control of module by this synchronous indicating signal, from the residue symbol of targeting sequencing, extract frequency deviation and phase information, and data division to received signal carries out the correction of frequency deviation and phase place.

Carrier wave (frequency deviation/phase place) is estimated and the job step of correction module is:

Follow-up targeting sequencing, after targeting sequencing detector detects targeting sequencing, is separated by demux module, and is designated as z by the sampled signal received _n, under the control of targeting sequencing synchronizing signal, local targeting sequencing generator produces and z _nthe conjugate p of the local targeting sequencing sampled signal that sequence is corresponding _n ^*the product sequence input simple signal frequency plot estimation module of above two sequences, obtain the estimated value of frequency deviation estimated value and phase place, these two estimated values are added, and and the vectorial data division being applied to the sampled signal received of correction of cos/sin look-up table generation carrier wave.

Received signal strength after correction is delivered to after chip synchronization module carries out chip synchronization and is carried out coherent demodulation.

The beneficial effect that the present invention reaches:

In physical layer transmission process, after receiving targeting sequencing, adopt method of the present invention, the carrier wave frequency deviation comprised in the targeting sequencing that abundant extraction receives and phase information, and this frequency deviation and phase place are used for all carrier wave frequency deviations of reception data of present frame and the compensation of phase place, make to use coherent demodulation to become possibility in this receiver, and then improve the overall receptivity of receiver.

Accompanying drawing explanation

Fig. 1 represents a block diagram meeting the receiver of IEEE 802.15.4-20062.4G physical layer standard;

Fig. 2 represents that carrier wave (frequency deviation/phase place) is estimated and corrects inside modules structure, for estimating and eliminate carrier wave frequency deviation and the phase deviation of Received signal strength.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

The implementation method of this innovation is described with the design example of the receiver meeting IEEE 802.15.4-20062.4G physical layer standard.

Fig. 1 represents a block diagram meeting the receiver of IEEE 802.15.4-20062.4G physical layer standard.

In FIG, the Received signal strength of sampling through radio frequency and analog-digital converter ADC is being sent into targeting sequencing detection/synchronization module, carrier wave (frequency deviation/phase place) estimation simultaneously and is being corrected module after receiving filter.Targeting sequencing detection/synchronization module provides symbol (symbol time that targeting sequencing has several identical the repeating form) synchronous indicating signal of targeting sequencing in time when detecting that sampled data meets the characteristic of targeting sequencing, carrier wave (frequency deviation/phase place) is estimated and is corrected the control of module by this synchronous indicating signal, from the residue symbol of targeting sequencing, extract frequency deviation and phase information, and data division to received signal carries out the correction of frequency deviation and phase place.

Fig. 2 represents that carrier wave (frequency deviation/phase place) is estimated and corrects inside modules structure, for estimating and eliminate carrier wave frequency deviation and the phase deviation of Received signal strength.

In fig. 2, follow-up targeting sequencing, after targeting sequencing detector detects targeting sequencing, is separated by demux module by the sampled signal received, here called after z _n, under the control of targeting sequencing synchronous indicating signal, local targeting sequencing generator produces and z _nthe conjugate p of the local targeting sequencing sampled signal that sequence is corresponding _n ^*, c _nfor the product sequence of above two sequences, this product sequence input simple signal frequency plot estimation module, obtains frequency deviation estimated value with the estimated values theta of phase place ', by after accumulator and θ ' addition, itself and value generate the vectorial data division being applied to the sampled signal received of correction of carrier wave by cos/sin look-up table.Received signal strength after correction is delivered to after chip synchronization module carries out chip synchronization and is carried out coherent demodulation.The simple signal frequency plot estimation module used in the present embodiment obtains frequency deviation estimated value with the estimated values theta of phase place ' represented by following formula:

c _n＝z _n·p _n ^*

$R_s\left(m\right)=\underset{k=0}{\overset{\mathrm{Ns}-1-m}{\mathrm{\Σ}}}{c}_{k+m}\·{c_k}^{*}$ m＝0,2,...Ns-1

$R\left(m\right)=\underset{s}{\mathrm{\Σ}}{R}_s\left(m\right)$

$w_m=\frac{3({({2L}_c+1)}^2-{(2m+1)}^2)}{({({2L}_c+1)}^2-1)({2L}_c+1)},$ m＝0,...L _c-1

$\mathrm{\Δ}\left(m\right)=\left\{\begin{array}{c}\arg \left[R\left(1\right)\right]..........................................................m=0\\ \mathrm{mod}[\arg \left(R(m+1)\right)-\arg \left(R\left(m\right)\right),2\mathrm{\π}].......m=1,...L_c-1\end{array}\right.$

$\mathrm{\Δ}\hat{f}=\frac{1}{2\mathrm{\π}{T}_s}\underset{m=0}{\overset{L_c-1}{\mathrm{\Σ}}}{w}_m\mathrm{\Δ}\left(m\right)$

${\mathrm{\θ}}^{\′}=\arg \left[\frac{1}{N1}\underset{n=\mathrm{lastN}1\mathrm{samples}}{\mathrm{\Σ}}{c}_n\right]$

Wherein, the estimated value formula of θ ' represents that θ ' is drawn by the average phase of last N1 the sampled point of Cn.Ns, S and Lc are design parameter.

Wherein, R _sm () is the autocorrelation sequence of S segment data, Ns is maximum auto-correlation distance;

R (m) is the individual independently R of S _s(m) result add and;

W _mfor weight sequence, the nonlinear transformation that Δ (m) is R (m).

In the implementation, sample clock frequency is 4 times of spreading rate, and therefore Selecting parameter is Ns=32, Lc=32, S=4.Targeting sequencing has 256 chips, has 1024 targeting sequencing sampled points after sampling, and current Selecting parameter only only used 128 sampled points wherein, and remaining 896 sampled points can be used for the adjustment of automatic growth control AGC and the detection of targeting sequencing.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (2)

1., for an a kind of Fast carrier synchronous method for fsk signal coherent demodulation, it is characterized in that, comprise following steps:

1) in physical layer transmission process, receiver is when detecting that the targeting sequencing of sampled signal arrives, use, with the local targeting sequencing waveform produced or prestore, modulation operations is gone to the targeting sequencing waveform received, obtain the simple signal of a Phase Continuation;

2) by estimating frequency and the phase place of this simple signal to the method for simple signal frequency and phase estimation;

3) eliminate frequency deviation and the phase place of received frame according to this estimated value, obtain the Received signal strength of carrier synchronization;

The step of the simple signal that obtains after going to modulate being carried out to filtering is also comprised in step 1);

To the estimation of simple signal frequency and phase place with eliminate the carrier wave frequency deviation of Received signal strength and the process of phase deviation is:

Filtered simple signal is sent into targeting sequencing detection/synchronization module, carrier estimation and correction module simultaneously;

Targeting sequencing detection/synchronization module provides the synchronous indicating signal of leading symbol in time when detecting that sampled data meets the characteristic of targeting sequencing, carrier estimation and correction module are subject to the control of this synchronous indicating signal, from the residue symbol of targeting sequencing, extract frequency deviation and phase information, and data division to received signal carries out the correction of frequency deviation and phase place;

The job step of carrier estimation and correction module is:

Follow-up targeting sequencing, after targeting sequencing detector detects targeting sequencing, is separated by demux module, and is designated as z by the sampled signal received _n, under the control of targeting sequencing synchronizing signal, local targeting sequencing generator produces and z _nthe conjugate p of the local targeting sequencing sampled signal that sequence is corresponding _n ^*the product sequence input simple signal frequency plot estimation module of above two sequences, obtain the estimated value of frequency deviation estimated value and phase place, these two estimated values are added, and and the vectorial data division being applied to the sampled signal received of correction of cos/sin look-up table generation carrier wave.

2. a kind of Fast carrier synchronous method for fsk signal coherent demodulation according to claim 1, is characterized in that, the Received signal strength after correction is delivered to after chip synchronization module carries out chip synchronization and carried out coherent demodulation.