CN1490962A - Automatic frequency controller and method thereof - Google Patents

Abstract

This invention introduces a automatic frequency control device and its method, applied in base station adopting coherent demodulation and the receiver system of mobile station, includes the matched filter, the multi path searching unit, the multi path separation unit, the channel de-spread unit, the channel estimation and multi path combining unit, the self-adapting automatic frequency control unit, the above statement matched filter at receiving end receives the signal from the antenna, sends it to the above statement multi path searching unit and the above statement multi path separation unit, the outputting information of the above statement separation unit enters into the above statement de-spread unit and self-adopting automation frequency control unit, the outputting information of the above statement de-spread unit and self-adopting frequency control unit enters into the above statement channel estimation and multi path combining unit, this invention can promote the accuracy of frequency discriminating and system performance.

Description

A kind of automatic frequency control apparatus and method thereof

Technical field

The present invention relates to field of wireless communications systems, especially relate to the automatic frequency control technology field of base station and travelling carriage in the code division multiple address communication system.

Technical background

Carrier synchronization is an important practical problem in the communication system.Code division multiple access (Code DivisionMultiple Acess, CDMA) in the communication system, up channel and down channel all adopt the detection mode of coherent demodulation, require receiving terminal the demodulation carrier wave must with the modulated carrier of transmitting terminal with homophase frequently.

Because volume and cost are limit, the long-time stability of the local crystal oscillator of travelling carriage can not be done very highly, and simultaneously because the mobile Doppler frequency shift phenomenon that also exists of travelling carriage, this all makes the frequency difference that has carrier wave between base station and the travelling carriage.Requirement according to broadband CDMA communication system (WCDMA), the crystal oscillator output jitter of travelling carriage must be less than 3ppm, travelling carriage can be operated in the mobile environment of 500km/h simultaneously, can cause the Doppler frequency shift about 1kHz, and initial frequency deviation reaches as high as 7KHz like this.Because the crystal oscillator stability of base station itself is very high, and only may there be a modulated carrier frequencies in base station itself, so generally with the local frequency of base station as benchmark, and in travelling carriage, adopt automatic frequency control technology (AFC) to catch and follow the tracks of the carrier frequency of received signal, to reach reception and to send the consistent of carrier frequency.

According to the protocol requirement of 3GPP, travelling carriage is after adopting AFC, and its carrier wave shake must also be positive and negative 200Hz less than 0.1ppm.As mentioned above, usually need not adopt the AFC technology in base station side, but, should consider that frequency deviation receives the influence that reconciliation tonality the subject of knowledge and the object of knowledge brings to signal of base station, and should on baseband signal, adopt AFC correction technology to reduce the influence of frequency deviation base station (NodeB) demodulation performance based on following reason.

At first, because the cost and the volume of travelling carriage limit, its frequency deviation index may be discontented with football association and discuss requirement; Two, in soft switching process, because travelling carriage might only lock the carrier frequency of a certain base station, but it follows other base station communications with the frequency of locking again simultaneously, even at this moment the AFC performance of travelling carriage satisfies protocol requirement, cause thus the frequency deviation of other base stations be can reach 400Hz-600Hz.Between NodeB the fixed frequency difference of the highest 200Hz add the transmission carrier frequency shake (its model with the AFC algorithm of UE etc. relevant) of the highest positive and negative 200Hz UE, if travelling carriage locking is the mean value of two base station frequencies, the high frequency difference frequency between it and base station also may reach 300Hz so; Three, the Doppler frequency shift that brings of the high-speed mobile of travelling carriage might cause the system frequency deviation up to 1KHz, particularly UE often might have only a direct projection footpath when the high-speed mobile of Plain, and Doppler's influence at this moment just might become a fixing frequency deviation.The quick decline that big frequency deviation causes will inevitably exert an influence to the channel estimating of system.In these cases, can consider to adopt the AFC technology to reduce this influence, thus the performance index of the system that improves.

In cdma system, the correction of frequency deviation can be carried out before or after Multipath searching, if carry out before being corrected in Multipath searching, can eliminate the influence of frequency deviation to a Multipath searching and a despreading, but it is very big at this moment to carry out the correction calculations amount on the data of sampling magnitude, the realization of hardware and the performance of system have directly been limited, therefore in concrete realization.Consideration is corrected frequency deviation at symbol level after Multipath searching.Frequency deviation will influence Multipath searching although it is so, but at this moment low through data rate after the despreading, amount of calculation is little, by emulation testing the influence of system is not influenced performance.

The patent and the document of the AFC aspect in the cdma system are more, respectively from the structure of AFC, and the extraction of frequency offset estimating and frequency difference, aspects such as the design of loop filter are studied.

Fig. 1 is a kind of structure chart than typical A FC algorithm, derives from U.S. Pat 5,640,431.From the received signal of antenna by despread unit 101 and branching unit 102 after, obtain pilot signal 103 and data 104, pilot signal 103 obtains the rough estimate 105 of frequency by frequency acquisition unit 106, and pilot signal 103 and rough estimate 105 are further followed the tracks of frequency through frequency-tracking unit 107.By behind the phase transition unit 108, the frequency of data-signal is revised again.

The shortcoming of this method is:

1 since AFC to catch with following the tracks of be to realize by two different frequency discriminators, and, directly influenced follow-up tracking performance because to catch the frequency discriminator precision in the original system relatively poor;

2 do not have the processing method of consideration to multipath in the fading channel;

3 do not mention for very crucial handoff algorithms between catching and following the tracks of.

Summary of the invention

Purpose of the present invention proposes a kind of automatic frequency control apparatus and method exactly, is applicable in the receiver system of the base station of adopting the coherent demodulation mode and travelling carriage, can improve frequency discrimination accuracy, improve the performance of system.

A kind of automatic frequency control apparatus, comprise the receiving terminal matched filter, the Multipath searching unit, the multipath separative element, the channel despread unit, channel estimating and multipath merge cells, self adaptation automatic frequency control unit, described receiving terminal matched filter receives the signal from antenna, send to described Multipath searching unit and described multipath separative element, the output information of described multipath separative element enters described channel despread unit and described self adaptation automatic frequency control unit, and the information of described channel despread unit and the output of described self adaptation automatic frequency control unit enters described channel estimating and multipath merge cells.

Described self adaptation automatic frequency control unit comprises frequency discriminator, auto-adaptive loop filter, voltage-controlled oscillator (VCO), enter described frequency discriminator from the effective diameter indication information of described multipath separative element output with from the rectification complex signal of described channel estimating and the output of multipath merge cells, the frequency offset signal of described frequency discriminator output is handled by described auto-adaptive loop filter, enter into described voltage-controlled oscillator (VCO), the generated frequency compensating signal.

Described frequency discriminator comprises inhibit signal unit, multiplier, multipath frequency offset signal merge cells, frequency offset calculation unit, from the rectification complex signal of described channel estimating and multipath merge cells output with through self inhibit signal of described inhibit signal cell processing multiplier after the conjugate multiplication, be input to multipath frequency offset signal merge cells with effective diameter indication information from described multipath separative element output, by described frequency offset calculation cell processing, obtain frequency deviation value again.

Described auto-adaptive loop filter comprises first switch controller, switch decision device, transient state loop filter, stable state loop filter, second switch controller, switch decision device output initialize signal or switching signal, between first switch controller, second switch controller selector switch is arranged, can select to be communicated with described transient state loop filter or described stable state loop filter.

Described voltage-controlled oscillator (VCO) comprises integrator, compensate of frequency deviation computing unit, and frequency offset signal is input to integrator and compensate of frequency deviation computing unit, obtains the sine wave of two-way quadrature.

Described first switch controller or described second switch controller comprise first multiplier, second multiplier, first integrator, adder, second integral device, the signal of described first switch controller output is given described first multiplier, described second multiplier and described first integrator respectively, again with the two paths of signals input summer, the gained signal enters described second integral device, obtains the input signal of described second switch controller.

Described switch decision device comprises loop circuit state computing unit, inhibit signal unit, decision unit.

A kind of auto frequency control method may further comprise the steps:

A, will carry out matched filtering from the received signal of antenna after, send to Multipath searching unit and multipath separative element respectively;

B, Multipath searching unit extract current effective multipath information, and isolate each footpath information and effective diameter indication information of serial output through the multipath separative element;

C, the complex signal of effective diameter indication information and rectification is carried out self adaptation automatic frequency control, obtain the frequency compensation signal;

D, each footpath information via channel despread unit separate spreading code, descrambling code operation after, with of the frequency correction of frequency compensation signal, will revise again that the back signal carries out channel estimating and multipath merges processing through multiplier.

Described step c further may further comprise the steps:

The complex signal of c1, effective diameter indication information and rectification at first enters frequency discriminator and estimates frequency offset signal;

C2, frequency offset signal are handled output accurate frequency bias signal by adaptive loop filter;

C3, generate the correspondent frequency compensating signal by voltage-controlled oscillator (VCO) again.

Described step c1 further may further comprise the steps:

The complex signal of c11, rectification and the inhibit signal of self are carried out conjugate multiplication by multiplier;

C12, the signal that obtains and effective diameter indication information carry out the multipath frequency offset signal and merge;

C13, obtain the arc tangent of complex signal by the frequency offset calculation unit then, remove the delay factor of signal again, obtain estimated frequency offset signal.

At k constantly, for i bar footpath, the complex signal of rectification can be expressed as:

$y_i\left(k\right)=(I_i\left(k\right)+j{Q}_i\left(k\right))=d_i\left(k\right)e^{{\mathrm{j\ω}}_i\left(k\right)t_i\left(k\right)+{\mathrm{\θ}}_i\left(k\right)},$

I wherein _i(k), Q _i(k) be respectively that signal is I, the complex signal of Q two-way, d _i(k), w _i(k) t _i(k) be the amplitude and the phase place of signal complex representation, θ _i(k) be the interference that noise is introduced, current data and its top n data conjugate multiplication obtain

$z_i\left(k\right)=y_i\left(k\right)\×y_i^{*}(k-N)=d_i\left(k\right)d_i(k-N)e^{j{\mathrm{\ω}}_{\mathrm{id}}\left(k\right)\mathrm{NT}},$

Z wherein _i(k) be each footpath frequency discrimination output of serial form, w _Id(k) be the frequency deviation output in the i footpath after merging, in multipath frequency offset signal merging process,,, consider the validity in each footpath simultaneously, obtain the estimation of frequency difference to eliminate the influence of multipath fading to the frequency difference equal gain combining in each footpath

$w_d\left(k\right)=\frac{1}{\mathrm{NT}}\arg \{(\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)*z_i\left(k\right))/\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)\},$

Wherein, i represents each footpath, and l represents maximum effective diameter number, a _i(k)={ 0, whether effectively 1} represents k that the effective diameter indication information provided i footpath information constantly, w _d(k) the accurate frequency bias estimated signal that obtains of expression.

Described step c2 basis $h\left(k\right)=\left|\frac{1}{N}\underset{i=(k-1)N}{\overset{\mathrm{kN}-1}{\mathrm{\Σ}}}{u}_i\left(t\right)\right|,$

U wherein _iWhat (k) expression accurate frequency bias signal, N were represented to average counts, the output of the current average of h (k) expression, and when h (k)＜h (k+1), loop is in trapped state; Loop switches to tracking mode when h (k) 〉=h (k+1).

The present invention makes full use of the multipath information in the Rake receiver, to the method that the frequency discrimination output in every footpath takes vector to merge, has effectively utilized the information in each footpath, has improved the accuracy of frequency discrimination, has improved the performance of system.

The realization of algorithm of the present invention does not increase the expense of system substantially, but can obtain the very big improvement of performance.

Description of drawings

Fig. 1 is existing automatic frequency control structure schematic diagram;

Fig. 2 is an automatic frequency control structure schematic diagram of the present invention;

Fig. 3 is a self adaptation automatic frequency control structure schematic diagram;

Fig. 4 is the frequency discriminator structural representation;

Fig. 5 is the auto-adaptive loop filter structural representation;

Fig. 6 is the loop filter structure schematic diagram;

Fig. 7 is a switch decision device structural representation;

Fig. 8 is the voltage-controlled oscillator (VCO) structural representation.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is described.

The present invention belongs to a kind of closed-loop control, its general structure as shown in Figure 2, at first enter the matched filter 200 of receiving terminal from the received signal of antenna, pass through associative operation, extract current effective multipath information by Multipath searching unit 201, and isolate each footpath information and effective diameter indication information 207 of serial output through multipath separation module 202.Wherein each footpath information is separated spreading code by channel despread unit 203, the descrambling code operation, and carry out the frequency correction by multiplier 206 with after treatment compensate of frequency deviation signal 209, then revised signal is delivered to channel estimating and RAKE and merged module 205 and carry out subsequent treatment.Wherein compensate of frequency deviation signal 209 is by comprising I, obtaining after the complex signal 208 of the rectification of Q two-way and effective diameter indication information 207 process self adaptation automatic frequency control units 204 are handled.

As shown in Figure 3, in the self adaptation automatic frequency control unit 204, the complex signal 208 of rectification and effective diameter indication information 207 at first enter frequency discriminator 300 and estimate frequency offset signal 303, carry out respective handling by auto-adaptive loop filter 301 then, the output signal of auto-adaptive loop filter 301 is more accurate frequency offset signal 304, generates correspondent frequency compensating signal 209 by a voltage-controlled oscillator (VCO) 302 again.

As shown in Figure 4, in the frequency discriminator 300, at first the complex signal 208 of rectification and the inhibit signal of self (through inhibit signal unit 401) are by after multiplier 402 conjugate multiplication, enter multipath frequency offset signal merge cells 403 together with effective diameter indication information 207, then by frequency offset calculation unit 404, after asking for the arc tangent of complex signal, remove the delay factor of signal again, obtain estimated frequency offset signal 303.

At k constantly, for i bar footpath, the complex signal 208 of rectification can be expressed as:

$y_i\left(k\right)=(I_i\left(k\right)+j{Q}_i\left(k\right))=d_i\left(k\right)e^{{\mathrm{j\ω}}_i\left(k\right)t_i\left(k\right)+{\mathrm{\θ}}_i\left(k\right)},$

I wherein _i(k), Q _i(k) represent that respectively signal is I, the complex signal of Q two-way, d _i(k), w _i(k) t _i(k) can think the amplitude and the phase place of signal complex representation, θ _i(k) interference of expression noise introducing can be thought gradual here.

Current data and its top n data conjugate multiplication obtain:

$z_i\left(k\right)=y_i\left(k\right)\×y_i^{*}(k-N)=d_i\left(k\right)d_i(k-N)e^{j{\mathrm{\ω}}_{\mathrm{id}}\left(k\right)\mathrm{NT}},$

In order to eliminate the influence of multipath fading, to the frequency difference equal gain combining in each footpath, consider the validity in each footpath simultaneously in the multipath frequency offset signal merge cells 403.Z wherein _i(k) be each footpath frequency discrimination output of serial form, w _Id(k) be the frequency deviation output in the i footpath after merging.Can obtain being estimated as of frequency difference:

$w_d\left(k\right)=\frac{1}{\mathrm{NT}}\arg \{(\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)*z_i\left(k\right))/\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)\},$

Wherein, i represents each footpath, and l represents maximum effective diameter number, a _i(k)={ 0, whether effectively 1} represents k that effective diameter indication information 207 provided i footpath information constantly, w _d(k) the more accurate frequency offset estimating value that obtains of expression.

As shown in Figure 5, in the auto-adaptive loop filter 301, switch decision device 504 provides initialize signal 505 when initial, the output switch 506 of first switch controller 500 is connected with transient state filter 501, the input switch 507 of second switch controller 503 is also connected with transient state filter 501, this moment, system was in trapped state, and switch decision device 504 constantly calculates according to the signal of more accurate frequency offset signal 304.If satisfy switching condition, then provide switching signal 505, this moment, the output switch 506 of first switch controller 500 can be connected with stationary filter 502, and the input switch 507 of second switch controller 503 can be connected with stationary filter 502, and system enters tracking mode.The switching of native system is unidirectional, disposable switching.

Transient state filter 501 and stationary filter 502 are the loop filter of same structure, and difference only is the parameter difference that is provided with.Fig. 6 represents the structure chart of transient state filter 501 and stationary filter 502, is the loop filter of a second order.The output signal 605 of first switch controller 500 is respectively by multiplier 600 and multiplier 601, and integrator 602 then with results added, again by integrator 604, obtains the input signal 606 of second switch controller 503 at last.K _p, K _iThe parameter of difference representative ring path filter.

As shown in Figure 7, be the structure chart of switch decision device 504.701 calculation expression is:

$h\left(k\right)=\left|\frac{1}{N}\underset{i=(k-1)N}{\overset{\mathrm{kN}-1}{\mathrm{\Σ}}}{u}_i\left(t\right)\right|,$

U wherein _i(t) the more accurate frequency offset signal 304 of expression is the output of current loop filter, and what N represented to average counts, the output of the current average of h (k) expression, and in the process that loop is caught, filter response curve is in rising trend.At this time linear the increasing progressively of average h (k) of the curve of output of a period of time loop filter, i.e. h (k)＜h (k+1).After loop is caught, the curve of output of filter can be the amount of decrease fluctuation near steady-state value, the characteristic that at this moment can present h (k) 〉=h (k+1), at this moment we can think that system has entered stable state, and with this switching point as loop, at this moment provide switching signal 505, loop switches to tracking mode from trapped state.

One of subject matter that the switch decision device will be considered is the size of bandwidth varying.Acquisition bandwidth and tracking (after being stable state) bandwidth is as required to different K in transient state filter 501 and the stationary filter 502 _p, K _iSelection of parameter realizes.The size of acquisition bandwidth is wanted to guarantee quick lock in the time that limits, that is to say, guarantee that the transient state time of loop is enough little, the tracking bandwidth value that enters after the stable state is wanted to guarantee that the steady-state error value of loop is enough little, that is to say that chattering frequency is enough little.

Guarantee the performance of loop, except the parameter that will consider two loop filters, another problem is the moment of switching.At first, N can not be oversize, the oversize state variation that then can not in time reflect loop, and can increase hard-wired complexity, too weak point then can not fully be eliminated interference of noise, causes erroneous judgement.

Fig. 8 is the structure chart of voltage-controlled oscillator (VCO) 302.Input signal is more accurate frequency offset signal 304, by integrator 801, exports the sine wave of two-way quadratures again by 802 backs.

The present invention makes full use of the multipath information in the Rake receiver, to the method that the frequency discrimination output in every footpath takes vector to merge, has effectively utilized the information in each footpath, has improved the accuracy of frequency discrimination.

Become the handoff algorithms of loop bandwidth filter, for loop filter, the capture time of system and the steady-state error of system are the factors of a pair of mutual restriction, by corresponding system parameter setting, when the capture time of system more in short-term, be that system can enter stable state by transient state very soon, then the relative steady-state error of system is bigger during stable state.And in order to reduce the steady-state error of system, must be cost with the sacrificial system capture time then.

In order to accelerate system acquisition time and to obtain comparatively ideal steady-state error, the present invention adopts the scheme that becomes the loop bandwidth filter, promptly adopt two loop filters, use the loop filter of big bandwidth at the acquisition phase of system, the capture time of quickening system, and after system enters stable state, adopt the loop filter of less bandwidth.Like this can be fully in conjunction with the advantage of the loop filter of two kinds of different bandwidths, by the parameter of loop filter rationally is set, can be under the prerequisite that guarantees same steady-state error (comparing) with other schemes, nearly order of magnitude descends on the capture time of system.Can reduce the time that system enters stable state greatly on the one hand, on the other hand, under stable state, can keep less steady-state error, thereby effectively improve the demodulation performance of system.

The realization of algorithm of the present invention does not increase the expense of system substantially, but can obtain the very big improvement of performance.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with the people of this technology in the disclosed technical scope of the present invention; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (12)

1, a kind of automatic frequency control apparatus, comprise the receiving terminal matched filter, the Multipath searching unit, the multipath separative element, the channel despread unit, channel estimating and multipath merge cells, it is characterized in that: also comprise self adaptation automatic frequency control unit, described receiving terminal matched filter receives the signal from antenna, send to described Multipath searching unit and described multipath separative element, the output information of described multipath separative element enters described channel despread unit and described self adaptation automatic frequency control unit, and the information of described channel despread unit and the output of described self adaptation automatic frequency control unit enters described channel estimating and multipath merge cells.

2, automatic frequency control apparatus as claimed in claim 1, it is characterized in that: described self adaptation automatic frequency control unit comprises frequency discriminator, auto-adaptive loop filter, voltage-controlled oscillator (VCO), enter described frequency discriminator from the effective diameter indication information of described multipath separative element output with from the rectification complex signal of described channel estimating and the output of multipath merge cells, the frequency offset signal of described frequency discriminator output is handled by described auto-adaptive loop filter, enter into described voltage-controlled oscillator (VCO), the generated frequency compensating signal.

3, automatic frequency control apparatus as claimed in claim 2, it is characterized in that: described frequency discriminator comprises inhibit signal unit, multiplier, multipath frequency offset signal merge cells, frequency offset calculation unit, from the rectification complex signal of described channel estimating and multipath merge cells output with through self inhibit signal of described inhibit signal cell processing multiplier after the conjugate multiplication, be input to multipath frequency offset signal merge cells with effective diameter indication information from described multipath separative element output, by described frequency offset calculation cell processing, obtain frequency deviation value again.

4, automatic frequency control apparatus as claimed in claim 2, it is characterized in that: described auto-adaptive loop filter comprises first switch controller, switch decision device, transient state loop filter, stable state loop filter, second switch controller, switch decision device output initialize signal or switching signal, between first switch controller, second switch controller selector switch is arranged, can select to be communicated with described transient state loop filter or described stable state loop filter.

5, automatic frequency control apparatus as claimed in claim 2 is characterized in that: described voltage-controlled oscillator (VCO) comprises integrator, compensate of frequency deviation computing unit, and frequency offset signal is input to integrator and compensate of frequency deviation computing unit, obtains the sine wave of two-way quadrature.

6, automatic frequency control apparatus as claimed in claim 4, it is characterized in that: described first switch controller or described second switch controller comprise first multiplier, second multiplier, first integrator, adder, second integral device, the signal of described first switch controller output is given described first multiplier, described second multiplier and described first integrator respectively, again with the two paths of signals input summer, the gained signal enters described second integral device, obtains the input signal of described second switch controller.

7, automatic frequency control apparatus as claimed in claim 4 is characterized in that: described switch decision device comprises loop circuit state computing unit, inhibit signal unit, decision unit.

8, a kind of auto frequency control method is applicable in the multipath receiver, it is characterized in that may further comprise the steps:

A, will carry out matched filtering from the received signal of antenna after, send to Multipath searching unit and multipath separative element respectively;

B, Multipath searching unit extract current effective multipath information, and isolate each footpath information and effective diameter indication information of serial output through the multipath separative element;

C, the complex signal of effective diameter indication information and rectification is carried out self adaptation automatic frequency control, obtain the frequency compensation signal;

D, each footpath information via channel despread unit separate spreading code, descrambling code operation after, with of the frequency correction of frequency compensation signal, will revise again that the back signal carries out channel estimating and multipath merges processing through multiplier.

9, auto frequency control method as claimed in claim 8 is characterized in that: described step c further may further comprise the steps:

The complex signal of c1, effective diameter indication information and rectification at first enters frequency discriminator and estimates frequency offset signal;

C2, frequency offset signal are handled output accurate frequency bias signal by adaptive loop filter;

C3, generate the correspondent frequency compensating signal by voltage-controlled oscillator (VCO) again.

10, auto frequency control method as claimed in claim 9 is characterized in that: described step c1 further may further comprise the steps:

The complex signal of c11, rectification and the inhibit signal of self are carried out conjugate multiplication by multiplier;

C12, the signal that obtains and effective diameter indication information carry out the multipath frequency offset signal and merge;

C13, obtain the arc tangent of complex signal by the frequency offset calculation unit then, remove the delay factor of signal again, obtain estimated frequency offset signal.

11, auto frequency control method as claimed in claim 10 is characterized in that:

At k constantly, for i bar footpath, the complex signal of rectification can be expressed as:

$y_i\left(k\right)=(I_i\left(k\right)+j{Q}_i\left(k\right))=d_i\left(k\right)e^{{\mathrm{j\ω}}_i\left(k\right)t_i\left(k\right)+{\mathrm{\θ}}_i\left(k\right)},$

I wherein _i(k), Q _i(k) be respectively that signal is I, the complex signal of Q two-way, d _i(k), w _i(k) t _i(k) be the amplitude and the phase place of signal complex representation, θ _i(k) be the interference that noise is introduced, current data and its top n data conjugate multiplication obtain

$z_i\left(k\right)=y_i\left(k\right)\×y_i^{*}(k-N)=d_i\left(k\right)d_i(k-N)e^{j{\mathrm{\ω}}_{\mathrm{id}}\left(k\right)\mathrm{NT}},$

Z wherein _i(k) be each footpath frequency discrimination output of serial form, w _Id(k) be the frequency deviation output in the i footpath after merging, in multipath frequency offset signal merging process,,, consider the validity in each footpath simultaneously, obtain the estimation of frequency difference to eliminate the influence of multipath fading to the frequency difference equal gain combining in each footpath

$w_d\left(k\right)=\frac{1}{\mathrm{NT}}\arg \{(\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)*z_i\left(k\right))/\underset{i=1}{\overset{l}{\mathrm{\Σ}}}{a}_i\left(k\right)\},$

Wherein, i represents each footpath, and l represents maximum effective diameter number, a _i(k)={ 0, whether effectively 1} represents k that the effective diameter indication information provided i footpath information constantly, w _d(k) the accurate frequency bias estimated signal that obtains of expression.

12, auto frequency control method as claimed in claim 9 is characterized in that: described step c2 basis:

$h\left(k\right)=\left|\frac{1}{N}\underset{i=(k-1)N}{\overset{\mathrm{kN}-1}{\mathrm{\Σ}}}{u}_i\left(t\right)\right|,$

U wherein _iWhat (t) expression accurate frequency bias signal, N were represented to average counts, the output of the current average of h (k) expression, and when h (k)＜h (k+1), loop is in trapped state; Loop switches to tracking mode when h (k) 〉=h (k+1).

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