WO2010118596A1

WO2010118596A1 - Method and device for correcting frequency offset

Info

Publication number: WO2010118596A1
Application number: PCT/CN2009/073541
Authority: WO
Inventors: 王曼; 黄旭
Original assignee: 中兴通讯股份有限公司
Priority date: 2009-04-13
Filing date: 2009-08-26
Publication date: 2010-10-21
Also published as: CN101860499A; CN101860499B

Abstract

The present invention discloses a method and device for correcting frequency offset. The device is composed of an Automatic Frequency Control (AFC) circuit and a baseband processing module. The baseband processing module is located behind the AFC circuit and used for performing baseband processing on the frequency output by the AFC circuit, estimating the frequency offset, correcting the frequency output by the AFC circuit according to the frequency offset and feeding back the corrected frequency to the AFC circuit. The AFC circuit is used for performing automatic frequency control, before the baseband processing module, on the signal input into the AFC circuit. The present invention also discloses a method for correcting frequency offset, enables the Doppler frequency offset caused by high speed movement to be effectively corrected in real time, enables the UE to reconstruct the signal sent by the base station correctly and improves the communication quality.

Description

一种纠正频偏的方法和装置 Method and device for correcting frequency offset

技术领域本发明涉及无线通信中的频率控制技术，具体而言，涉及一种纠正频偏的方法和装置。背景技术自动频率控制（Automatic Frequency Control, 筒称为 AFC ) 是一种使输出信号的频率与给定频率保持确定关系的频率控制方法。实现自动频率控制的 AFC电路，也称 AFC环，如图 1所示，主要由频率比较器 10、低通滤波器 20和可控频率器件 30等构成。可控频率器件 30通常采用压控振荡器，用以产生本地受控振荡频率 f。；频率比较器 10 的作用是将输入信号的频率 f_c与可控频率器件 30产生的本地受控振荡频率 f。进行比较，检测频偏，并输出误差电压；低通滤波器 20 , 用以对频率比较器输出的误差电压进行干扰及噪声滤除，保留低频信息。闭环时，频率比较器 10 输出误差电压使可控频率器件 30的振荡频率 f。偏离减小，从而将 AFC电路的输出信号频率拉向额定值。 TECHNICAL FIELD The present invention relates to frequency control techniques in wireless communications, and more particularly to a method and apparatus for correcting frequency offsets. BACKGROUND OF THE INVENTION Automatic Frequency Control (AFC) is a frequency control method that maintains a determined relationship between the frequency of an output signal and a given frequency. An AFC circuit that realizes automatic frequency control, also called an AFC ring, is mainly composed of a frequency comparator 10, a low-pass filter 20, and a controllable frequency device 30, as shown in FIG. The controllable frequency device 30 typically employs a voltage controlled oscillator to generate a locally controlled oscillating frequency f. The frequency comparator 10 functions to correlate the frequency f _{c of the} input signal with the locally controlled oscillation frequency f generated by the controllable frequency device 30. Comparing, detecting the frequency offset, and outputting the error voltage; the low-pass filter 20 is used for performing interference and noise filtering on the error voltage outputted by the frequency comparator, and retaining low-frequency information. In the closed loop, the frequency comparator 10 outputs an error voltage to cause the oscillation frequency f of the controllable frequency device 30. The deviation is reduced to pull the output signal frequency of the AFC circuit to the nominal value.

AFC电路的工作过程为： f。与 f_c在频率比较器 10中进行比较，当 f。=f_c 时，频率比较器 10无误差电压输出，控制电压为 0, 可控频率器件 30的振荡频率保持不变；当 f。≠f_c时，频率比较器 10有误差电压输出，该误差电压正比于频率误差 f_c-f。 , 误差电压经过氏通滤波器 20滤除干 4尤及噪声后，得到控制电压，控制电压控制可控频率器件 30输出的本地受控振荡频率 f。发生变发，从而使得频率误差 f_c-f。减小到一定值 f , 自动控制过程随即停止，可控频率器件 30即稳定于 f。=f_c ± f上，环路进入锁定状态，锁定状态的 f称为稳态频率误差。这种通过频率负反馈的作用，并经过 AFC环的反复循环调节，能够最终达到平衡状态，从而使***的工作频率保持稳定且偏差很小。然而，传统的 AFC电路通常是针对频率和相位不变的输入信号而言，如果输入信号的频率和相位在不断的变发，则必须通过一定的方法，使可控频率器件 30 的频率和相位不断 3艮踪 AFC环的输入信号的频率和相位变发。如上所述，现有技术中输入信号的频率变发范围非常小，而在高速运动场景中，如高速列车中的用户终端（User Equipment, 筒称为 UE ) 与地面上的基站进行通信时 ,由于存在多普勒频移使得输入信号的频率变发范围增大。例如：输入信号的起始频率为 f_c, 由于多普勒频移的影响，在信道中频率变发为： f_c'=f_c +Af, 其中 Af表示多普勒频移，此频率 f_c'即 AFC电路中输入信号的频率。支如原先 AFC电路已达到平衡状态，那么输入信号的频率突然大幅改变，会导致输入信号的频率与本地受控振荡频率 f。的频率差突然变大， ***在短时间内艮难达到平衡状态，从而影响 AFC的性能。一方面，需要增大频率差的变发范围，使***能纠正更大范围内变发的频率差，这可以通过调节各元器件的参数来实现；另一方面，则需要能够实时调整在信道中产生偏差的频率信息（多普勒频移）。针对相关技术中如何发现高速运动中产生的频率偏差信息（多普勒频移），并实时的对产生偏差的频率信息进行纠正的问题，目前尚未提出有效的解决方案。发明内容针对相关技术中没有提供如何发现高速运动中产生的频率偏差信息 ,并实时的对产生偏差的频率信息进行纠正的方案的问题而提出本发明 , 为此，有鉴于此，本发明的主要目的在于提供一种纠正频偏的方法和装置，以解决上述问题，以实时纠正由于高速运动引起的多普勒频移。为了实现上述目的 , 才艮据本发明的一个方面，本发明提供了一种纠正频偏的装置。才艮据本发明的纠正频偏的装置包括：自动频率控制 AFC电路和基带处理模块组成。基带处理模块位于 AFC电路的后端，用于对 AFC电路输出信号进行基带处理，估计出频偏，并根据频偏对 AFC电路输出的频率进行纠正，将纠正后的频率反馈给 AFC 电路； AFC 电路，用于在基带处理模块之前，对输入 AFC电路的信号进行自动频率控制。基带处理模块包括：频偏纠正模块、信道估计模块和频偏估计模块，其中，频偏纠正模块，用于接收 AFC电路输出的频率，并根据频偏估计模块反馈的频偏，对 AFC电路输出的频率进行纠正；信道估计模块，用于根据频偏纠正模块输出的频率信息和已知的发送信号的信息，估计信道的***冲激响应；频偏估计模块，用于才艮据时变的信道的***冲激响应估计出频偏，并将频偏反馈给频偏纠正模块。 The working process of the AFC circuit is: f. Compare with f _c in frequency comparator 10, when f. When =f _c , the frequency comparator 10 has no error voltage output, the control voltage is 0, and the oscillation frequency of the controllable frequency device 30 remains unchanged; when f. When ≠f _c , the frequency comparator 10 has an error voltage output which is proportional to the frequency error f _c -f. After the error voltage is filtered by the pass filter 20 to filter out the dry 4 and the noise, a control voltage is obtained, and the control voltage controls the local controlled oscillation frequency f outputted by the controllable frequency device 30. A change occurs, resulting in a frequency error f _c -f. When reduced to a certain value f, the automatic control process is stopped and the controllable frequency device 30 is stabilized at f. On =f _c ± f, the loop enters the locked state, and the locked state f is called the steady-state frequency error. This kind of negative feedback through the frequency, and through the repeated cycle adjustment of the AFC ring, can finally reach the equilibrium state, so that the operating frequency of the system remains stable and the deviation is small. However, the conventional AFC circuit is usually for the input signal with constant frequency and phase. If the frequency and phase of the input signal are constantly changing, the frequency and phase of the controllable frequency device 30 must be determined by a certain method. Constantly 3 tracks the frequency and phase of the input signal of the AFC ring. As described above, the frequency variation range of the input signal in the prior art is very small, and in a high-speed motion scenario, such as when a user equipment (User Equipment, called UE) in a high-speed train communicates with a base station on the ground, The frequency variation range of the input signal is increased due to the presence of Doppler shift. For example: The starting frequency of the input signal is f _c . Due to the influence of the Doppler shift, the frequency is changed in the channel as: f _c '=f _c +Af, where Af represents the Doppler shift, this frequency f _c ' is the frequency of the input signal in the AFC circuit. If the original AFC circuit has reached equilibrium, then the frequency of the input signal suddenly changes greatly, which will cause the frequency of the input signal and the locally controlled oscillation frequency f. The frequency difference suddenly becomes large, and the system is difficult to reach equilibrium in a short time, thereby affecting the performance of the AFC. On the one hand, it is necessary to increase the range of the frequency difference, so that the system can correct the frequency difference of the larger range of changes, which can be achieved by adjusting the parameters of each component; on the other hand, it needs to be able to adjust the channel in real time. The frequency information (Doppler shift) in which the deviation occurs. In view of how to find the frequency deviation information (Doppler shift) generated in high-speed motion in the related art and correct the frequency information of the deviation in real time, an effective solution has not been proposed yet. SUMMARY OF THE INVENTION The present invention has been made in view of the problem of how to find frequency deviation information generated in high-speed motion and correct the frequency information of the deviation in real time, and in view of this, the main It is an object to provide a method and apparatus for correcting frequency offsets to solve the above problems to correct Doppler shift due to high speed motion in real time. In order to achieve the above object, according to an aspect of the present invention, the present invention provides an apparatus for correcting frequency offset. The apparatus for correcting frequency offset according to the present invention comprises: an automatic frequency control AFC circuit and a baseband processing module. The baseband processing module is located at the back end of the AFC circuit for baseband processing of the AFC circuit output signal, estimating the frequency offset, correcting the frequency of the AFC circuit output according to the frequency offset, and feeding back the corrected frequency to the AFC circuit; A circuit that is used to automatically frequency control the signal input to the AFC circuit prior to the baseband processing module. The baseband processing module comprises: a frequency offset correction module, a channel estimation module and a frequency offset estimation module, wherein the frequency offset correction module is configured to receive the frequency of the output of the AFC circuit, and output the AFC circuit according to the frequency offset fed back by the frequency offset estimation module. The frequency is corrected; the channel estimation module is configured to estimate a system impulse response of the channel according to the frequency information output by the frequency offset correction module and the information of the known transmission signal; and the frequency offset estimation module is configured to be time-varying The system impulse response of the channel estimates the frequency offset and feeds the frequency offset back to the frequency offset correction module.

AFC电路由频率比较器、低通滤波器和可控频率器件组成。该装置进一步包括：频率处理模块，连接基带处理模块和频率比较器，用于将基带处理模块输出的频率上变频到高频，并反馈给频率比较器；相应的，频率比较器用于才艮据频率处理模块反馈的频率，调整误差电压以控制可控频率器件的频率输出。可控频率器件连接基带处理模块，用于才艮据基带处理模块反馈的频率，控制自身的频率输出。为了实现上述目的，根据本发明的一个方面，提供了一种纠正频偏方法。根据本发明的纠正频偏方法包括：基带处理模块对 AFC电路输出的频率进行基带处理 ,估计出频偏 ,并根据频偏对 AFC电路输出的频率进行纠正 , 将纠正后的频率反馈给 AFC电路； The AFC circuit consists of a frequency comparator, a low pass filter, and a controllable frequency device. The device further includes: a frequency processing module, a baseband processing module and a frequency comparator, configured to upconvert the frequency outputted by the baseband processing module to a high frequency and feed back to the frequency comparator; and correspondingly, the frequency comparator is used for the data The frequency fed back by the frequency processing module adjusts the error voltage to control the frequency output of the controllable frequency device. The controllable frequency device is connected to the baseband processing module for controlling the frequency output of the baseband processing module according to the frequency fed back by the baseband processing module. In order to achieve the above object, according to an aspect of the present invention, a method of correcting frequency offset is provided. The method for correcting the frequency offset according to the present invention includes: the baseband processing module performs baseband processing on the frequency of the output of the AFC circuit, estimates the frequency offset, corrects the frequency of the output of the AFC circuit according to the frequency offset, and feeds back the corrected frequency to the AFC circuit. ;

AFC电路根据基带处理模块反馈的频率执行 AFC处理。该方法进一步包括：基带处理模块输出的频率上变频到高频后反馈给The AFC circuit performs AFC processing based on the frequency fed back by the baseband processing module. The method further includes: the frequency of the output of the baseband processing module is upconverted to a high frequency and then fed back to

AFC电路的输入端。该方法进一步包括：基带处理模块输出的频率反馈给 AFC电路的输出端 , 控制 AFC电路的频率输出。基带处理和估计频偏的操作具体为：才艮据 AFC电路输出的频率信息和已知的发送信号的信息，估计信道的 ***冲激响应；根据时变的信道的***冲激响应中相邻时间点的相位差估计出频偏。该方法进一步包括：才艮据基于导频的非盲估计算法估计信道的***冲激响应。本发明所提供的纠正频偏的方法和装置，在 AFC电路后端增设基带处理模块，将基带的处理作为 AFC电路的整体进行考虑，基带处理后的经过频偏纠正的频率反馈回 AFC电路，以控制 AFC电路的自动频率控制操作，从而提高了频率控制的精确度，实现了对高速运动中所产生多普勒频移的实时有效纠正，使得 UE能够正确还原基站发送的信号，提高了通信质量。附图说明图 1是相关现有技术中 AFC环的组成结构才匡图；图 2是根据本发明实施例的纠正频偏的方法的流程图；图 3是才艮据本发明实施例的纠正频偏的装置的第一结构框图；图 4是才艮据本发明实施例中基带处理模块的结构框图；图 5是根据本发明实施例纠正频偏的装置的第二结构框图。具体实施方式功能相克述针对相关技术中没有提供如何发现高速运动中产生的频率偏差信息 ,实现对高速运动中产生的多普勒频移的实时纠正而提出本发明 , ,本发明在传统 AFC 电路的后端增设基带处理模块，以消除 AFC 电路输出端频率中的多普勒频移，将频偏纠正后的频率反馈给 AFC电路，以提高 AFC电路自动频率控制操作的精确度。需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。根据本发明的实施例，提供了一种纠正频偏的方法。图 2是才艮据本发明实施例的纠正频偏的方法的流程图，如图 2所示，该方法主要包括以下步骤：步骤 S201 , 基带处理模块对 AFC电路输出的频率进行基带处理，估计出频偏，并才艮据频偏对 AFC电路输出的频率进行纠正， ^)夺纠正后的频率反馈给 AFC电路。传统的 AFC电路由频率比较器、氏通滤波器和可控频率器件组成，本发明的基带处理模块与可控频率器件的输出端相连接，由基带处理模块对可控频率器件输出的频率进行基带处理，消除该频率中的多普勒频移，再将频偏纠正后的频率反馈给 AFC电路。基带处理的具体操作包括：根据可控频率器件输出的频率对信道的***冲激响应进行估计；才艮据信道的***冲激响应估计出频偏 , 该频偏即由高速运动中的多普勒频移 1起；才艮据得到的频偏对可控频率器件输出的频率进行纠正，从而得到频偏纠正后的频率。步骤 S202, AFC电路根据基带处理模块反馈的频率执行 AFC处理。经过基带处理，能够将 AFC电路输入信号的频率在信道中的失真还原，由基带处理模块反馈的经过频偏纠正后的频率更接近于 AFC 电路输入端信号的基站发送频率，从而可以提高 AFC电路自动频率控制操作的精确度。需要指出的是，基带处理模块反馈频率给 AFC电路的实现方式可以有多种，其中一种为：将基带处理后的频率反馈给 AFC电路的输入端，即频率比较器，以调整频率比较器中进行比较的反馈频率，从而利用频率比较器产生的误差电压控制可控频率器件的频率输出；另一种为：将基带处理后的频率反馈给 AFC电路的输出端，即可控频率器件，以直接控制 AFC电路的频率输出，从而达到纠正输出信号的频偏的目的。图 3是根据本发明实施例的纠正频偏的装置的第一结构框图，对应基带处理后的频率反馈给 AFC电路输入端的实现方式，其纠正频偏的装置如图 3 所示，该装置应用于 UE中，由 AFC电路、基带处理模块 40和频率处理模块 50组成 , 且构成一个封闭的环路。 AFC电路包括：频率比较器 10、氐通滤波器 20和可控频率器件 30。频率比较器 10 , 作为 AFC 电路的输入端，用于接收基站发送的信号，还用于接收基带处理模块 40通过频率处理模块 50反馈的频率，将反馈的频率与输入信号的频率进行比较，产生误差电压输出给低通滤波器 20。该误差电压正比于进行比较的频率差。低通滤波器 20, 用于对频率比较器 10输出的误差电压进行滤除干扰及噪声处理，得到控制电压输出给可控频率器件 30。可控频率器件 30根据接收到的控制电压产生输出频率。图 4是根据本发明实施例中基带处理模块的结构框图，如图 4所示，基带处理模块 40由频偏纠正模块 41、信道估计模块 42和频偏估计模块 43组成，且构成一个 ^"闭的环路。频偏纠正模块 41 , 用于接收可控频率器件 30输出的频率，并才艮据频偏估计模块 43反馈的频偏，对接收到的频率进行纠正。信道估计模块 42 , 用于才艮据频偏纠正模块 41 输出的频率信息和已知的发送信号的信息，估计信道的***冲激响应。频偏估计模块 43 , 用于才艮据时变的信道的***冲激响应估计出频偏，并将频偏反馈给频偏糾正模块 41。需要指出的是，在实际应用中对信道的***冲激响应 h进行估计的方法可以有多种，本发明采用基于导频（pilot ) 的非盲估计算法，即利用接收机已知的发送信号的信息来进行估计，如时分同步的码分多址（ Time Division-Synchronous Code Division Multiple Access , 筒称为 TD-SCDMA )系统中的导频码选取为训练序列（ midamble 码），此训练序列为一组由发射机发送过来的并且接收机已知的数据。这一组包含 128个基本码的训练序列可由已知的表格查得。由这组数据的发送通过各种信道估计的方法来估计信道的***冲激响应。估计的效果取决于采用的估计准则的不同，采用的估计准则如最小平方（Least Square, 筒称为 LS ) 算法等。最小平方算法的原理是：选择 h, 使其输出信号与接收信号间的误差的平方最小；在假设误差的平方最小时求出 h, 即为估计出来的信道的冲激响应。经信道估计模块 42得到的信道的冲激响应是一个时变的序列 , 这个时变的序列由于多普勒频移、晶振造成相位偏移因子，其相位的偏移量随时间成线性变发。因此，可以通过相邻时间点的相位差估计出频偏，且频偏的精确度可以由相位差的大小来控制。另外，由于经氐通滤波器 20处理后的数据为氐频数据 , 因此在基带处理模块 40和频率比较器 10之间还需要增设一个频率处理模块 50,用于将基带处理模块 40输出的频率上变频到高频，再反馈给频率比较器 10。图 5是才艮据本发明实施例纠正频偏的装置的第二结构框图，如图 5所示，基带处理后的频率不再经过频率处理模块 50 , 而是直接反馈给 AFC 电路的可控频率器件 30, 以直接控制 AFC电路的频率输出，从而达到纠正输出信号的频偏的目的。图 5 中基带处理模块 40的内部结构如图 4所示，与图 3 所示装置中的基带处理模块 40 的内部结构和各模块的实现功能相同，此处不再赘述。相比图 3所示的装置，图 5的装置缺少了频率处理模块 50, 从而减少了将基带处理后的频率进行上变频的操作，可以减少***处理时间。综上所述，本发明在 AFC电路后端增设基带处理模块，将基带的处理作为 AFC 电路的整体进行考虑，基带处理后的经过频偏纠正的频率反馈回 AFC 电路，以控制 AFC 电路的自动频率控制操作，从而提高了频率控制的精确度，实现了对高速运动中所产生多普勒频移的实时有效纠正，使得 UE 能够正确还原基站发送的信号，提高了通信质量。以上所述，仅为本发明的较佳实施例而已，并非用于限定本发明的保护范围。 The input of the AFC circuit. The method further includes: feeding back the frequency outputted by the baseband processing module to the output of the AFC circuit to control the frequency output of the AFC circuit. The operation of the baseband processing and the estimation of the frequency offset is specifically as follows: the system impulse response of the channel is estimated according to the frequency information output by the AFC circuit and the information of the known transmitted signal; the adjacent system impulse response according to the time varying channel The phase difference at the time point estimates the frequency offset. The method further includes estimating a system impulse response of the channel according to a pilot-based non-blind estimation algorithm. The method and device for correcting the frequency offset provided by the invention add a baseband processing module at the back end of the AFC circuit, and consider the processing of the baseband as the whole of the AFC circuit, and the frequency corrected by the baseband processing is fed back to the AFC circuit. In order to control the automatic frequency control operation of the AFC circuit, the accuracy of the frequency control is improved, and the real-time effective correction of the Doppler shift generated in the high-speed motion is realized, so that the UE can correctly restore the signal transmitted by the base station and improve the communication. quality. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the composition of an AFC ring in the related art; FIG. 2 is a flow chart of a method for correcting frequency offset according to an embodiment of the present invention; FIG. 3 is a correction according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 4 is a block diagram showing the structure of a baseband processing module according to an embodiment of the present invention; FIG. 5 is a second structural block diagram of an apparatus for correcting frequency offset according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to the related art, and does not provide information on how to find frequency deviation information generated in high-speed motion, and realizes real-time correction of Doppler shift generated in high-speed motion. The present invention is in a conventional AFC circuit. The baseband processing module is added at the back end to eliminate the Doppler shift in the output frequency of the AFC circuit, and the frequency after the frequency offset correction is fed back to the AFC circuit to improve the accuracy of the automatic frequency control operation of the AFC circuit. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. The invention will be described in detail below with reference to the drawings in conjunction with the embodiments. In accordance with an embodiment of the present invention, a method of correcting frequency offsets is provided. 2 is a flow chart of a method for correcting frequency offset according to an embodiment of the present invention. As shown in FIG. 2, the method mainly includes the following steps: Step S201, the baseband processing module performs baseband processing on the frequency outputted by the AFC circuit, estimates the frequency offset, and corrects the frequency outputted by the AFC circuit according to the frequency offset, and ^) takes the corrected frequency feedback to the AFC circuit. The conventional AFC circuit is composed of a frequency comparator, a pass-through filter and a controllable frequency device. The baseband processing module of the present invention is connected to the output end of the controllable frequency device, and the frequency of the output of the controllable frequency device is performed by the baseband processing module. The baseband processing eliminates the Doppler shift in the frequency and feeds back the frequency corrected by the frequency offset to the AFC circuit. The specific operations of the baseband processing include: estimating the system impulse response of the channel according to the frequency of the output of the controllable frequency device; estimating the frequency offset according to the system impulse response of the channel, which is the Doppler in the high-speed motion The frequency shift is 1; the frequency of the output of the controllable frequency device is corrected according to the obtained frequency offset, thereby obtaining the frequency after the frequency offset correction. Step S202, the AFC circuit performs AFC processing according to the frequency fed back by the baseband processing module. After the baseband processing, the frequency of the input signal of the AFC circuit can be reduced in the channel, and the frequency-corrected frequency fed back by the baseband processing module is closer to the base station transmission frequency of the signal of the input end of the AFC circuit, thereby improving the AFC circuit. The accuracy of automatic frequency control operations. It should be noted that the feedback frequency of the baseband processing module can be implemented in the AFC circuit. One of them is: The baseband processed frequency is fed back to the input end of the AFC circuit, that is, the frequency comparator to adjust the frequency comparator. The comparison feedback frequency is used to control the frequency output of the controllable frequency device by using the error voltage generated by the frequency comparator; the other is: feeding back the frequency of the baseband processing to the output end of the AFC circuit, and the frequency device can be controlled. The purpose is to directly control the frequency output of the AFC circuit, thereby achieving the purpose of correcting the frequency offset of the output signal. 3 is a first structural block diagram of an apparatus for correcting a frequency offset according to an embodiment of the present invention, corresponding to a frequency feedback of a baseband processed signal to an input end of an AFC circuit, and a device for correcting a frequency offset is shown in FIG. In the UE, it is composed of an AFC circuit, a baseband processing module 40 and a frequency processing module 50, and constitutes a closed loop. The AFC circuit includes: a frequency comparator 10, a pass filter 20, and a controllable frequency device 30. The frequency comparator 10 is used as an input end of the AFC circuit for receiving the signal sent by the base station, and is also used for receiving the frequency fed back by the baseband processing module 40 through the frequency processing module 50, and comparing the frequency of the feedback with the frequency of the input signal to generate The error voltage is output to the low pass filter 20. This error voltage is proportional to the frequency difference at which the comparison is made. The low pass filter 20 is configured to filter interference voltage and noise processing on the error voltage outputted by the frequency comparator 10, and obtain a control voltage output to the controllable frequency device 30. Can The frequency controlling device 30 generates an output frequency based on the received control voltage. 4 is a structural block diagram of a baseband processing module according to an embodiment of the present invention. As shown in FIG. 4, the baseband processing module 40 is composed of a frequency offset correction module 41, a channel estimation module 42, and a frequency offset estimation module 43, and constitutes a ^" The closed loop loop frequency correction module 41 is configured to receive the frequency output by the controllable frequency device 30, and correct the received frequency according to the frequency offset fed back by the frequency offset estimation module 43. The channel estimation module 42 The system uses the frequency information output by the frequency offset correction module 41 and the information of the known transmission signal to estimate the system impulse response of the channel. The frequency offset estimation module 43 is used for the system impulse of the time varying channel. The frequency offset is estimated in response, and the frequency offset is fed back to the frequency offset correction module 41. It should be noted that there are various methods for estimating the system impulse response h of the channel in practical applications, and the present invention uses pilot-based. (pilot) A non-blind estimation algorithm that uses the information of the transmitted signal known to the receiver for estimation, such as time division-synchronous code division multiple access (Time Division-Synchronous Code Division Multiple Ac The pilot code in the system of cess, called TD-SCDMA) is selected as the training sequence (midamble code), which is a set of data sent by the transmitter and known by the receiver. This group contains 128 The training sequence of the basic code can be found by a known table. The system impulse response is estimated by the method of various channel estimation by the transmission of the data. The effect of the estimation depends on the estimation criterion used, the estimation used. The criteria are the least squared (Least Square) algorithm, etc. The principle of the least squares algorithm is: select h to minimize the square of the error between the output signal and the received signal; find the h when the square of the assumed error is the smallest That is, the impulse response of the estimated channel. The impulse response of the channel obtained by the channel estimation module 42 is a time-varying sequence, which is caused by the Doppler shift and the phase shift factor of the crystal oscillator. The offset of the phase changes linearly with time. Therefore, the frequency offset can be estimated by the phase difference of adjacent time points, and the accuracy of the frequency offset can be determined by the phase difference. In addition, since the data processed by the pass-through filter 20 is the frequency data, a frequency processing module 50 is further needed between the baseband processing module 40 and the frequency comparator 10 for the baseband processing module. The frequency of the 40 output is upconverted to a high frequency, and then fed back to the frequency comparator 10. Fig. 5 is a second structural block diagram of the apparatus for correcting the frequency offset according to the embodiment of the present invention, as shown in Fig. 5, the frequency after the baseband processing Instead of passing through the frequency processing module 50, it is directly fed back to the controllable frequency device 30 of the AFC circuit to directly control the frequency output of the AFC circuit, thereby correcting the output signal. The purpose of the frequency offset. The internal structure of the baseband processing module 40 in FIG. 5 is as shown in FIG. 4, and the internal structure of the baseband processing module 40 and the implementation functions of the modules in the apparatus shown in FIG. 3 are the same, and details are not described herein again. Compared to the apparatus shown in Fig. 3, the apparatus of Fig. 5 lacks the frequency processing module 50, thereby reducing the operation of upconverting the frequency after the baseband processing, and reducing the system processing time. In summary, the present invention adds a baseband processing module at the back end of the AFC circuit, and considers the processing of the baseband as the whole of the AFC circuit. The frequency-corrected frequency after the baseband processing is fed back to the AFC circuit to control the automatic AFC circuit. The frequency control operation improves the accuracy of the frequency control, realizing the real-time effective correction of the Doppler frequency shift generated in the high-speed motion, so that the UE can correctly restore the signal transmitted by the base station and improve the communication quality. The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

Claims

权利要求书 Claim

1. 一种纠正频偏的装置，其特征在于，该装置由自动频率控制 AFC电路和基带处理模块组成，其中， A device for correcting frequency offset, characterized in that the device is composed of an automatic frequency control AFC circuit and a baseband processing module, wherein

所述基带处理模块位于所述 AFC电路的后端，用于对所述 AFC 电路输出信号进行基带处理，估计出频偏，并才艮据所述频偏对所述 AFC 电路输出的频率进行纠正，将纠正后的频率反馈给所述 AFC电路；所述 AFC电路，用于在所述基带处理模块之前，对输入所述 AFC 电路的信号进行自动频率控制。 The baseband processing module is located at a rear end of the AFC circuit, and is configured to perform baseband processing on the output signal of the AFC circuit, estimate a frequency offset, and correct the frequency of the output of the AFC circuit according to the frequency offset. And returning the corrected frequency to the AFC circuit; the AFC circuit is configured to perform automatic frequency control on a signal input to the AFC circuit before the baseband processing module.

2. 根据权利要求 1所述纠正频偏的装置，其特征在于，所述基带处理模块包括：频偏纠正模块、信道估计模块和频偏估计模块，其中， 2. The apparatus for correcting a frequency offset according to claim 1, wherein the baseband processing module comprises: a frequency offset correction module, a channel estimation module, and a frequency offset estimation module, where

所述频偏纠正模块，用于接收所述 AFC 电路输出的频率，并根据所述频偏估计模块反馈的频偏，对所述 AFC电路输出的频率进行纠正； The frequency offset correction module is configured to receive a frequency output by the AFC circuit, and correct a frequency output by the AFC circuit according to a frequency offset fed back by the frequency offset estimation module;

所述信道估计模块，用于才艮据所述频偏纠正模块输出的频率信息和已知的发送信号的信息，估计信道的***冲激响应； The channel estimation module is configured to estimate a system impulse response of the channel according to the frequency information output by the frequency offset correction module and the information of the known transmission signal;

所述频偏估计模块，用于才艮据时变的信道的***冲激响应估计出频偏，并^¹所述频偏反馈给所述频偏纠正模块。 The frequency offset estimation module for Burgundy becomes only when a channel impulse response of the system to estimate the frequency offset, and frequency offset feedback ^ ¹ to the offset correction module.

3. 根据权利要求 1或 2所述纠正频偏的装置，其特征在于，所述 AFC电路由频率比较器、氏通滤波器和可控频率器件组成。 3. Apparatus for correcting frequency offset according to claim 1 or 2, characterized in that said AFC is electrically routed by a frequency comparator, a flux filter and a controllable frequency device.

4. 根据权利要求 3所述纠正频偏的装置，其特征在于，该装置进一步包括：频率处理模块，连接所述基带处理模块和频率比较器，用于将所述基带处理模块输出的频率上变频到高频，并反馈给所述频率比较器；相应的，所述频率比较器用于才艮据所述频率处理模块反馈的频率，调整误差电压以控制所述可控频率器件的频率输出。 4. The apparatus for correcting frequency offset according to claim 3, wherein the apparatus further comprises: a frequency processing module, coupled to the baseband processing module and a frequency comparator for outputting the frequency of the baseband processing module Frequency conversion to high frequency and feedback to the frequency comparator; correspondingly, the frequency comparator is configured to adjust the error voltage to control the frequency output of the controllable frequency device according to the frequency fed back by the frequency processing module.

5. 才艮据权利要求 3所述纠正频偏的装置，其特征在于，所述可控频率器件连接所述基带处理模块，用于才艮据所述基带处理模块反馈的频率，控制自身的频率输出。 5. The apparatus for correcting frequency offset according to claim 3, wherein the controllable frequency device is connected to the baseband processing module, and is configured to control the frequency according to the frequency fed back by the baseband processing module. Frequency output.

6. 一种纠正频偏的方法，其特征在于，该方法包括： 6. A method of correcting frequency offset, the method comprising:

基带处理模块对 AFC 电路输出的频率进行基带处理，估计出频偏，并根据所述频偏对所述 AFC电路输出的频率进行纠正，将纠正后的频率反馈给所述 AFC电路； The baseband processing module performs baseband processing on the frequency of the output of the AFC circuit, estimates the frequency offset, and corrects the frequency of the output of the AFC circuit according to the frequency offset, and feeds the corrected frequency to the AFC circuit;

所述 AFC 电路根据所述基带处理模块反馈的频率执行 AFC 处理。 The AFC circuit performs AFC processing in accordance with the frequency fed back by the baseband processing module.

7. 才艮据权利要求 6所述纠正频偏的方法，其特征在于，该方法进一步包括：所述基带处理模块输出的频率上变频到高频后反馈给所述 AFC电路的输入端。 7. The method of correcting frequency offset according to claim 6, wherein the method further comprises: the frequency outputted by the baseband processing module is up-converted to a high frequency and fed back to an input end of the AFC circuit.

8. 才艮据权利要求 6所述纠正频偏的方法，其特征在于，该方法进一步包括：所述基带处理模块输出的频率反馈给所述 AFC电路的输出端，控制所述 AFC电路的频率输出。 8. The method for correcting frequency offset according to claim 6, wherein the method further comprises: feeding back a frequency output by the baseband processing module to an output end of the AFC circuit, and controlling a frequency of the AFC circuit Output.

9. 才艮据权利要求 6、或 7、或 8所述纠正频偏的方法，其特征在于，所述基带处理和估计频偏的操作具体为： 9. The method of correcting a frequency offset according to claim 6, or 7, or 8, wherein the baseband processing and the estimation of the frequency offset are specifically:

根据所述 AFC 电路输出的频率信息和已知的发送信号的信息，估计信道的***冲激响应； Estimating a system impulse response of the channel according to the frequency information output by the AFC circuit and the information of the known transmitted signal;

才艮据时变的信道的***冲激响应中相邻时间点的相位差估计出频偏。 The frequency offset is estimated from the phase difference of adjacent time points in the system impulse response of the time varying channel.

10. 才艮据权利要求 9所述纠正频偏的方法，其特征在于，该方法进一步包括：才艮据基于导频的非盲估计算法估计信道的***冲激响应。 10. The method of correcting frequency offset according to claim 9, wherein the method further comprises: estimating a system impulse response of the channel according to a pilot-based non-blind estimation algorithm.