CN102801673A - 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

A kind of Fast carrier method for synchronous that is used for fsk signal coherent demodulation

Technical field

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

Background technology

In existing near radio networked physics layer transmission technology, it is unit that the transmitting-receiving of information is often adopted with the 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 of appointing in advance (targeting sequencing/homing sequence) to give receiver, representes the beginning of data division in the frame.Receiver uses the appearance of specific this frame head of electric circuit inspection, and the data beginning in completion and the frame is synchronous.Average frame length is merely about 20 bytes in wireless FSK communication; Because frame head only is used for the detection that frame synchronization and signal have or not; Therefore usually use noncoherent demodulation mode that data are carried out demodulation, the method for well-known non-coherent demodulation has the loss of 3dB approximately than the method performance of coherent demodulation, but since its need not carrier phase is recovered; Therefore make comparatively simply, in industry obtained using widely.Although use noncoherent demodulation mode insensitive to the carrier phase mismatch; But carrier wave frequency deviation still can cause the decreased performance of non-coherent demodulation; This still needs extra circuit to compensate, to guarantee that frequency deviation is at certain scope inner receiver property retention substantially constant.More than can be summarized as: contain the information of carrier wave frequency deviation and phase place in the frame head, but prior art extraction and application has in addition well not caused and can only use the method for reseptance of this performance of non-coherent demodulation than the coherent demodulation difference.If use the method receiver of coherent demodulation on antinoise, anti-multipath, transmission range and receiving sensitivity, all will be significantly improved.

Summary of the invention

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

The present invention proposes when receiver detects frame head arrival; Use the local frame head waveform of storage in advance that the frame head waveform that receives is gone modulation operations; Use the filter filter away high frequency noise; Obtain a simple signal that phase place is continuous, the frequency of this simple signal and phase place are current carrier wave frequency deviation and phase error.Through using the various possible simple signal frequencies and the method for phase estimation, estimate the frequency and the phase place of this section simple signal, draw the carrier wave frequency deviation and the phase error of present frame.Simultaneously; Because the frame length of burst transfer is all very short each time; Carrier wave frequency deviation and phase place can be thought in the same frame does not have to change, and carrier wave frequency deviation and the phase error of therefore using above estimation to come out are applied to current received frame, can think and accomplish carrier synchronization; And then can carry out coherent demodulation, to reach better receptivity.

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

1) in the physical layer transmission process; When receiver arrives at the targeting sequencing that detects sampled signal; Use with the local targeting sequencing waveform that produces or store in advance the targeting sequencing waveform that receives is gone modulation operations, obtain a simple signal that phase place is continuous;

2) estimate the frequency and the phase place of this section simple signal through method to simple signal frequency and phase estimation;

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

Use coherent demodulation method is carried out demodulation to the reception signal of carrier synchronization.

Also comprise the step that the simple signal that obtains after going to modulate is carried out filtering in the step 1).

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

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

The targeting sequencing detection/synchronization module is detecting the synchronous indicating signal that in time provides leading symbol when sampled data meets the characteristic of targeting sequencing; Carrier wave (frequency deviation/phase place) estimation and correction module receive 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.

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

The sampled signal that receives is separated follow-up targeting sequencing by the demux module after the targeting sequencing detector detects targeting sequencing, and is designated as z _n, under the control of targeting sequencing synchronizing signal, local targeting sequencing generator produces and z _nThe conjugate p of the corresponding local targeting sequencing sampled signal of sequence _n ^*More than the product sequence input simple signal frequency plot estimation module of two sequences; Obtain the estimated value of frequency offset estimating value and phase place, these two estimated value additions, and generate the data division of the sampled signal that the correction vector of carrier wave is applied to receive with the cos/sin look-up table.

Reception signal after the correction is delivered to the chip synchronization module and is carried out carrying out coherent demodulation after the chip synchronization.

The beneficial effect that the present invention reached:

In the physical layer transmission process; After receiving targeting sequencing; Adopt method of the present invention, fully extract carrier wave frequency deviation and the phase information that comprises in the targeting sequencing that receives, and this frequency deviation and phase place are used for the carrier wave frequency deviation of all reception data of present frame and the compensation of phase place; Make and in this receiver, use coherent demodulation to become possibility, and then improve the whole receptivity of receiver.

Description of drawings

Fig. 1 representes a block diagram that meets the receiver of IEEE 802.15.4-20062.4G physical layer standard;

Fig. 2 representes that carrier wave (frequency deviation/phase place) is estimated and correction inside modules structure, is used to estimate and eliminate carrier wave frequency deviation and the phase deviation that receives signal.

Embodiment

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

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

Fig. 1 representes a block diagram that meets the receiver of IEEE 802.15.4-20062.4G physical layer standard.

In Fig. 1, behind the process receiving filter, sent into targeting sequencing detection/synchronization module, carrier wave (frequency deviation/phase place) estimation simultaneously and corrected module through the reception signal of radio frequency and analog-digital converter ADC sampling.The targeting sequencing detection/synchronization module is detecting the symbol that in time provides targeting sequencing when sampled data meets the characteristic of targeting sequencing (targeting sequencing have repeat on the several same symbol time to constitute) synchronous indicating signal; Carrier wave (frequency deviation/phase place) estimation and correction module receive 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.

Fig. 2 representes that carrier wave (frequency deviation/phase place) is estimated and correction inside modules structure, is used to estimate and eliminate carrier wave frequency deviation and the phase deviation that receives signal.

In Fig. 2, the sampled signal that receives is separated follow-up targeting sequencing by the demux module after the targeting sequencing detector detects targeting sequencing, 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 corresponding local targeting sequencing sampled signal of sequence _n ^*, c _nBe the product sequence of above two sequences, this product sequence input simple signal frequency plot estimation module obtains the frequency offset estimating value

With the estimated values theta of phase place ',

Through behind the accumulator and θ ' addition, the data division of the sampled signal that it is applied to receive with the correction vector of value through cos/sin look-up table generation carrier wave.Reception signal after the correction is delivered to the chip synchronization module and is carried out carrying out coherent demodulation after the chip synchronization.The simple signal frequency plot estimation module of using in the present embodiment obtains the estimated values theta of frequency offset estimating value and phase place ' by following formulate:

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 formulate θ ' of θ ' is drawn by the average phase of last N1 the sampled point of Cn.Ns, S and Lc are design parameter.

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

R (m) is S independently R _s(m) result add with;

W _mBe the weight sequence, Δ (m) is the nonlinear transformation of R (m).

In realization, the sampling clock frequency is 4 times of spreading rate, so parameter is chosen as Ns=32, Lc=32, S=4.Targeting sequencing has 256 chips, has 1024 targeting sequencing sampled points after the sampling, and current parameter is selected only to have used 128 sampled points wherein, remaining 896 sampled points to can be used for automatic gain and controlled the adjustment of AGC and the detection of targeting sequencing.

The above only is a preferred implementation of the present invention; Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from know-why of the present invention; Can also make some improvement and distortion, these improvement and distortion also should be regarded as protection scope of the present invention.

Claims (5)

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

1) in the physical layer transmission process; When receiver arrives at the targeting sequencing that detects sampled signal; Use with the local targeting sequencing waveform that produces or store in advance the targeting sequencing waveform that receives is gone modulation operations, obtain a simple signal that phase place is continuous;

2) estimate the frequency and the phase place of this section simple signal through method to simple signal frequency and phase estimation;

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

2. a kind of Fast carrier method for synchronous that is used for fsk signal coherent demodulation according to claim 1 is characterized in that, also comprises the step that the simple signal that obtains after going to modulate is carried out filtering in the step 1).

3. a kind of Fast carrier method for synchronous that is used for fsk signal coherent demodulation according to claim 2 is characterized in that, to the estimation of simple signal frequency and phase place with eliminate the carrier wave frequency deviation that receives signal and the process of phase deviation is:

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

The targeting sequencing detection/synchronization module is detecting the synchronous indicating signal that in time provides leading symbol when sampled data meets the characteristic of targeting sequencing; Carrier estimation and correction module receive 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.

4. a kind of Fast carrier method for synchronous that is used for fsk signal coherent demodulation according to claim 3 is characterized in that, carrier estimation with the job step of correcting module is:

The sampled signal that receives is separated follow-up targeting sequencing by the demux module after the targeting sequencing detector detects targeting sequencing, and is designated as z _n, under the control of targeting sequencing synchronizing signal, local targeting sequencing generator produces and z _nThe conjugate p of the corresponding local targeting sequencing sampled signal of sequence _n ^*More than the product sequence input simple signal frequency plot estimation module of two sequences; Obtain the estimated value of frequency offset estimating value and phase place, these two estimated value additions, and generate the data division of the sampled signal that the correction vector of carrier wave is applied to receive with the cos/sin look-up table.

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

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