WO2011091671A1 - 一种实现自动频率控制的方法和装置 - Google Patents

一种实现自动频率控制的方法和装置 Download PDF

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Publication number
WO2011091671A1
WO2011091671A1 PCT/CN2010/077391 CN2010077391W WO2011091671A1 WO 2011091671 A1 WO2011091671 A1 WO 2011091671A1 CN 2010077391 W CN2010077391 W CN 2010077391W WO 2011091671 A1 WO2011091671 A1 WO 2011091671A1
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Prior art keywords
frequency offset
value
received signal
path
offset adjustment
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PCT/CN2010/077391
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English (en)
French (fr)
Inventor
易立强
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中兴通讯股份有限公司
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Priority to EP10844448.0A priority Critical patent/EP2530894B1/en
Priority to US13/380,614 priority patent/US8699638B2/en
Publication of WO2011091671A1 publication Critical patent/WO2011091671A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
    • H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
    • H04L27/38—Demodulator circuits; Receiver circuits
    • H04L27/3818—Demodulator circuits; Receiver circuits using coherent demodulation, i.e. using one or more nominally phase synchronous carriers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Definitions

  • the present invention relates to the field of wireless communications, and more particularly to a method and apparatus for implementing automatic frequency control.
  • AFC Automatic Frequency Control
  • the present invention provides a method and apparatus for implementing automatic frequency control to improve the accuracy, efficiency, and stability of frequency offset control.
  • the present invention provides a method for implementing automatic frequency control, including: calculating a correlation value and a frequency offset value of a common pilot symbol in each path received signal, and calculating a combination according to a frequency offset value of each path received signal a frequency offset value, and determining a frequency offset adjustment value for the voltage controlled oscillator, a frequency offset adjustment value for the overall received signal, and a frequency offset adjustment value for each of the received signals according to the combined frequency offset value.
  • the calculating the correlation value of the common pilot symbols in the received signals of each path and the frequency offset value may include: performing correlation calculation on the plurality of common pilot symbols received in a time slot for each path received signal, obtaining correlation values, and performing The number of symbols L of the interval between the two symbols of the correlation calculation is an integer greater than or equal to 2, and the frequency offset value corresponding to the correlation value is calculated according to the correlation value and the number of symbols L.
  • the step of calculating the combined frequency offset value according to the frequency offset value of the received signal of each path may include: determining whether the frequency offset value of each path signal is valid according to the signal-to-interference ratio threshold of each path received signal, and performing weighted combining on the effective frequency offset value Then, the combined frequency offset value is obtained, and the weighting parameter of the frequency offset value of each path received signal is determined by the proportion of the common pilot symbol signal to interference ratio corresponding to the frequency offset value in the sum of the common pilot symbol and the signal to interference ratio of each path.
  • the method may further include: filtering the combined frequency offset value with a low pass filter, and adjusting a value of the filter coefficient used by the low pass filter according to the adjustment phase.
  • the frequency offset adjustment value of the voltage controlled oscillator can be adjusted by the following methods by combining the frequency offset values.
  • F, ", A represents the adjustment control parameter
  • 3 ⁇ 4T is the combined frequency offset value in the current frequency offset adjustment process
  • 3 ⁇ 4 ⁇ is the combined frequency offset value in the last frequency offset adjustment process
  • 3 ⁇ 4: is the current frequency offset adjustment
  • f is the frequency offset adjustment value of the voltage controlled oscillator during the last frequency offset adjustment process.
  • the frequency offset adjustment value for the overall received signal can be determined as ⁇ -3 ⁇ 4; the frequency offset adjustment value for each path received signal can be determined as 4; -3 ⁇ 4T, which is the frequency offset value of the path i received signal.
  • the method may further include: performing frequency offset compensation according to the determined phase angle corresponding to the frequency offset adjustment value and the coordinate rotation digital computer algorithm.
  • the present invention also provides an apparatus for implementing automatic frequency control, comprising a connected correlation calculation module and a frequency offset calculation module, wherein the correlation calculation module is configured to calculate a correlation value of a common pilot symbol in each path received signal;
  • the partial calculation module is configured to calculate a frequency offset value of each path received signal;
  • the device further includes a frequency offset adjustment control module connected to the frequency offset calculation module; and the frequency offset adjustment control module is configured to be configured according to each
  • the frequency offset value of the path received signal is calculated to obtain a combined frequency offset value, and the frequency offset adjustment value of the voltage controlled oscillator, the frequency offset adjustment value of the overall received signal, and the received signal for each path are determined according to the combined frequency offset value.
  • Frequency offset adjustment value is calculated to obtain a combined frequency offset value, and the frequency offset adjustment value of the voltage controlled oscillator, the frequency offset adjustment value of the overall received signal, and the received signal for each path are determined according to the combined frequency offset value.
  • the correlation calculation module may be configured to calculate a correlation value of the common pilot symbols in the received signals of the respective paths by: performing, for each of the plurality of common pilot symbols received in one slot for each of the received signals Off, the correlation value is obtained, and the number of symbols L between the two symbols of the correlation calculation is an integer greater than or equal to 2; the frequency offset calculation module may be configured to calculate the frequency offset value of the received signals of each path as follows: The value and the number of symbols L calculate the frequency offset value corresponding to this correlation value.
  • the frequency offset adjustment control module can be configured to calculate the combined frequency offset value by: determining whether the frequency offset value of each path signal is valid according to the signal-to-interference ratio threshold of each path received signal, and weighting and combining the effective frequency offset values to obtain The combined frequency offset value, the weighting parameter of the frequency offset value of each path received signal is determined by the proportion of the common pilot symbol signal to interference ratio corresponding to the frequency offset value in the sum of the common pilot symbol and the signal to interference ratio of each path.
  • the frequency offset adjustment control module may be further configured to filter the combined frequency offset value by using a low pass filter, and adjust the value of the filter coefficient used by the low pass filter according to the adjustment phase.
  • the frequency offset adjustment control module can be set to determine by adjusting the combined frequency offset value in the following manner.
  • A represents the adjustment control parameter
  • 3 ⁇ 4T is the combined frequency offset value in the current frequency offset adjustment process
  • 3 ⁇ 4 ⁇ is the combined frequency offset value in the previous frequency offset adjustment process
  • 3 ⁇ 4 : It is the frequency offset adjustment value of the voltage controlled oscillator during the current frequency offset adjustment process
  • f is the frequency offset adjustment value of the voltage controlled oscillator during the previous frequency offset adjustment process.
  • the frequency offset adjustment control module can be configured to: determine the frequency offset adjustment value of the overall received signal as f - .
  • the frequency offset adjustment value of the received signal for each path is determined as ⁇ - If , which is the frequency offset value of the path i signal.
  • the apparatus may further include a frequency offset compensation module, and the frequency offset compensation module may be configured to perform frequency offset compensation according to a phase angle corresponding to the frequency offset adjustment value determined by the frequency offset adjustment control module and a coordinate rotation digital computer algorithm.
  • a new small-range frequency offset estimation method is selected to make the frequency offset estimation more accurate than the prior art; Coordinate Rotation Digital Computer (CORDIC) algorithm is used.
  • CORDIC Coordinate Rotation Digital Computer
  • the hardware resources are saved, and the calculation accuracy is improved; the frequency offset adjustment control strategy makes the radio frequency adjustment more gradual, and the stability of the system is strengthened.
  • 1 is a structural diagram of an apparatus for realizing automatic frequency control
  • 2A is a diagram 1 of a frequency offset estimation related operation structure
  • 2B is a diagram 2 of a frequency offset estimation related operation structure
  • 2C is a third embodiment of the frequency offset estimation related operation structure
  • FIG 3 is the AFC overall scheme 1 in the Rake receiver
  • Figure 4 is the AFC overall scheme 2 in the Rake receiver
  • Figure 5 is a schematic diagram of the implementation of the CORDIC algorithm
  • Figure 6 is a flow chart of a method for implementing automatic frequency control.
  • the device for realizing automatic frequency control comprises a related calculation module, a frequency offset calculation module, a frequency offset adjustment control module and a frequency offset compensation module which are sequentially connected.
  • a correlation calculation module configured to extract a common pilot symbol (CPICH) in each path received signal, and calculate a correlation value of a common pilot symbol in each path received signal, and specifically, receive the signal in each slot for each path signal. Correlation calculation is performed on a plurality of common pilot symbols to obtain correlation values, and the calculation method is described as follows:
  • CPICH symbol received by the relevant calculation module is Wt
  • some pilot symbols in the common pilot channel (CPICH) received in one slot may be correlated and calculated.
  • the correlation between symbols achieves the purpose of eliminating the influence of the channel, for example, correlation calculation is performed only for the first to eighth pilot symbols.
  • the correlation calculation mode between symbols involves the range and accuracy of the frequency offset estimation results, and is divided into large-range frequency offset estimation and small-range frequency offset estimation.
  • Large-scale frequency offset estimation is not high enough, suitable for frequency offset capture state; small range frequency offset estimation is high precision, suitable for frequency offset tracking state.
  • the frequency offset acquisition state is typically done internally by the initial cell search module.
  • the Rake receiver it mainly focuses on the frequency offset tracking adjustment after the initial frequency offset acquisition and compensation.
  • the calculation of the correlation value C is shown in Figure 2A and the following equation:
  • the number L of symbols between the two symbols for correlation calculation is an integer greater than or equal to 2; the first example is that L is 4, as shown in Figure 2B and below. Show:
  • a frequency offset calculation module configured to calculate a frequency offset value of each path received signal
  • the frequency offset calculation module is further configured to calculate a frequency offset value corresponding to the correlation value according to the correlation value output by the correlation calculation module and the L value used in performing the correlation operation.
  • the calculation range of the frequency offset is determined by J.
  • J the measured frequency offset is ⁇ 7.5KHz, and the frequency offset estimation range is wide, but the estimation accuracy is limited, suitable for initial frequency offset acquisition, and can be applied to the initial cell search module.
  • J the measured frequency offset is ⁇ 1.75KHz, the estimation accuracy is very accurate, and it can meet the Doppler frequency estimation range requirement due to high-speed motion, and is suitable for frequency offset tracking adjustment state.
  • What is involved in the invention is the precise AFC adjustment in Rake after undergoing initial frequency offset adjustment.
  • the WCDMA system can be calculated by selecting appropriate relevant modules to achieve AFC control with different accuracy and range.
  • a frequency offset adjustment control module configured to calculate a combined frequency offset value according to a frequency offset value of each path received signal, and determine a frequency offset adjustment value of the voltage controlled oscillator according to the combined frequency offset value, and the overall receiving The frequency offset adjustment value of the signal (ie, the overall reception I, Q data) and the frequency offset adjustment value of the received signal for each path.
  • the frequency offset adjustment control module determines whether the frequency offset value of each path signal is valid according to the signal-to-interference ratio (SIR) threshold of each path signal, and removes the invalid frequency offset value.
  • SIR signal-to-interference ratio
  • the signal-to-interference ratio (SIR) threshold can be estimated from the received CPICH symbols as shown in Figure 3, or directly from the multipath search module in the system as shown in Figure 4.
  • the weighting parameter of the frequency offset value of each path signal is determined by the proportion of the corresponding common pilot symbol signal to interference ratio in the sum of the common pilot symbol and signal to interference ratios of the respective paths. If 57 represents the SIR of the peak i, then
  • ⁇ J ⁇ and where is the control threshold (M is the effective number of paths exceeding the threshold).
  • the adjustment control module uses a low-pass filter to filter the combined frequency offset value
  • the low-pass filter may be a first-order infinite-length impulse response filter (IIR) low-pass filter, according to different adjustment stages, Adjust its filter coefficient. For example, initially select a larger filter coefficient, such as 1/2, after a few adjustment cycles, select a slightly smaller filter coefficient, such as 1/4; the effect is to make the filter effect follow the current frequency offset faster at the beginning of the adjustment. The estimated value can then be well filtered.
  • IIR infinite-length impulse response filter
  • F is the frequency value set by the system, which is a real number greater than 0 and less than 1, and ⁇ is a real number greater than 0.
  • F is 50 ⁇ , 1/2, ⁇ is
  • 3 ⁇ 4T is the combined frequency offset value in the current frequency offset adjustment process
  • 3 ⁇ 4 ⁇ is the combined frequency offset value in the previous frequency offset adjustment process, ⁇ :. It is the frequency offset adjustment value of the voltage controlled oscillator during the current frequency offset adjustment process
  • 3 ⁇ 4 is the frequency offset adjustment value of the voltage controlled oscillator during the last frequency offset adjustment process.
  • the frequency offset value of the overall received signal is f - vco, and the CORDIC algorithm in the frequency offset compensation module is used to compensate.
  • the offset compensation value is the difference between each radial offset value and the combined frequency offset adjustment value, that is, ⁇ - is the frequency offset value of the path i, i is an integer greater than or equal to 0 and less than or equal to N-1, and N is the number of the finger. It can achieve fast and subtle compensation of the internal residual frequency offset of the finger.
  • a frequency offset compensation module is configured to perform frequency offset compensation according to a phase angle corresponding to the frequency offset adjustment value and a coordinate rotation digital computer algorithm. If the input received signal is represented by x + jy , the frequency offset compensation is obtained:
  • ⁇ is the phase rotation amount of the compensation frequency offset of the received signal sample, and its value is calculated by 1 ⁇ /At, where At is the time interval between the signal samples; / is the calculated frequency offset compensation value, as can be seen from the above, for the total
  • the input signal is the cumulative value of the frequency offset adjustment ⁇ -3 ⁇ 4 after the AFC is started, and the corresponding value of the corresponding path is the cumulative value of the frequency offset adjustment ⁇ - r after the AFC is started.
  • the traditional method uses a look-up table algorithm or a triangulation method, and considers the resource cost, and the implementation precision is limited.
  • the CORDIC Coordinat Rotation Digital Computer, referred to as CORDIC
  • CORDIC Coordinat Rotation Digital Computer
  • the number of iterations is generally determined by the accuracy of the calculation and can be quantized to a certain value.
  • CORDIC can be realized by using the shift-plus-combination pipeline structure, which is efficient and easy to implement.
  • the structure of the pipeline unit realized by CORDIC is shown in Fig. 5. As shown in FIG.
  • the method for implementing automatic frequency control includes: calculating a correlation value and a frequency offset value of a common pilot symbol in each path received signal, and calculating a combined frequency offset value according to a frequency offset value of each path received signal, and according to The combined frequency offset value determines a frequency offset adjustment value for the voltage controlled oscillator, a frequency offset adjustment value for the overall received signal (ie, the overall received I, Q data), and a frequency offset adjustment value for each of the received signals.
  • the implementation order of the above method is the same as the related calculation module, the frequency offset calculation module, the frequency offset adjustment control module and the frequency offset compensation module in the above device description, and the specific implementation method corresponds to the module function, and the details are not described herein. .
  • the invention has the following beneficial effects: the frequency offset estimation is more accurate; the hardware resources are saved, the calculation precision is improved; and the stability of the system is strengthened.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

本发明公开了一种实现自动频率控制的方法和装置，此方法包括：计算各径接收信号中公共导频符号的相关值以及频偏值，根据各径接收信号的频偏值计算得到合并频偏值，并根据所述合并频偏值确定对压控振荡器的频偏调整值、对总体接收信号的频偏调整值以及对各径接收信号的频偏调整值。采用本发明所述方法和装置，与现有技术相比，选择新的小范围频偏估计方法，使频偏估计更加准确；采用CORDIC，节省了硬件资源，且计算精度得到提高；频偏调整控制策略使射频调整更加平缓，使系统的稳定性得到加强。

Description

一种实现自动频率控制的方法和装置
技术领域
本发明涉及无线通信领域， 尤其涉及一种实现自动频率控制的方法和装 置。
背景技术
在宽带码分多址 （ Wideband Code Division Multiple Access , 简称 WCDMA ) 系统中， 通常会由于本地晶振的精确度和稳定性的影响， 以及在 移动终端移动过程中的多普勒效应， 在基站和终端之间存在载波频差也称为 频偏。这种频偏将对终端的解调性能产生较大影响。 自动频率控制（Automatic Frequency Control, 简称 AFC )作为频偏纠正控制有效方法， 在系统中得到 广泛应用。 已有的方法在 WCDMA系统中对自动频率控制较为单一， 对系统 全面考虑甚少， 且频偏补偿算法， 釆用传统的查表或者三角变化法， 硬件消 耗比较大。
发明内容
本发明提供一种实现自动频率控制的方法和装置， 提高频偏控制的准确 度、 效率和稳定性。
为了解决上述问题， 本发明提供了一种实现自动频率控制的方法， 包括： 计算各径接收信号中公共导频符号的相关值以及频偏值， 根据各径接收信号 的频偏值计算得到合并频偏值， 并根据所述合并频偏值确定对压控振荡器的 频偏调整值、 对总体接收信号的频偏调整值以及对各径接收信号的频偏调整 值。
计算各径接收信号中公共导频符号的相关值以及频偏值的步骤可以包 括：针对各径接收信号在一时隙中接收到的多个公共导频符号进行相关计算， 得到相关值， 并且进行相关计算的两符号间间隔的符号个数 L是大于等于 2 的整数， 根据相关值和符号个数 L计算此相关值对应的频偏值。 根据各径接收信号的频偏值计算得到合并频偏值的步骤可包括： 根据各 径接收信号的信干比门限判断各径信号的频偏值是否有效， 对有效的频偏值 进行加权合并后得到合并频偏值， 各径接收信号的频偏值的加权参数由该频 偏值对应的公共导频符号信干比在各径公共导频符号信干比之和中的比重确 定。 该方法还可包括： 釆用低通滤波器对合并频偏值进行滤波处理， 并根据 调整阶段， 调整此低通滤波器使用的滤波系数的值。
对压控振荡器的频偏调整值可以通过对合并频偏值釆用以下方式进行调 整控
≤中/
Figure imgf000004_0001
其中， F, ", A 表示调整控制参数， ¾T是当前频偏调整过程中的合并 频偏值， ¾ β是上一次频偏调整过程中的合并频偏值， ¾ :。是当前频偏调整 过程中对压控振荡器的频偏调整值， f:是上一次频偏调整过程中对压控振 荡器的频偏调整值。
对总体接收信号的频偏调整值可以被确定为^^-¾ ； 对各径接收信 号的频偏调整值可以被确定为 4;-¾T , 是径 i接收信号的频偏值。 该方 法还可以包括： 根据所确定的频偏调整值对应的相角以及坐标旋转数字计算 机算法进行频偏补偿。
本发明还提供了一种实现自动频率控制的装置， 包括相连的相关计算模 块和频偏计算模块， 所述相关计算模块设置成计算各径接收信号中公共导频 符号的相关值； 所述频偏计算模块设置成计算各径接收信号的频偏值； 其特 征在于， 所述装置还包括与所述频偏计算模块相连的频偏调整控制模块； 所 述频偏调整控制模块设置成根据各径接收信号的频偏值计算得到合并频偏 值， 并根据所述合并频偏值确定对压控振荡器的频偏调整值、 对总体接收信 号的频偏调整值以及对各径接收信号的频偏调整值。
相关计算模块可设置成通过如下方式计算各径接收信号中公共导频符号 的相关值： 针对各径接收信号在一时隙中接收到的多个公共导频符号进行相 关计算， 得到相关值， 并且进行相关计算的两符号间间隔的符号个数 L是大 于等于 2的整数； 频偏计算模块可设置成通过如下方式计算各径接收信号的 频偏值： 根据相关值和符号个数 L计算此相关值对应的频偏值。
频偏调整控制模块可设置成通过如下方式计算得到合并频偏值： 根据各 径接收信号的信干比门限判断各径信号的频偏值是否有效， 对有效的频偏值 进行加权合并后得到合并频偏值， 各径接收信号的频偏值的加权参数由该频 偏值对应的公共导频符号信干比在各径公共导频符号信干比之和中的比重确 定。 频偏调整控制模块还可设置成釆用低通滤波器对合并频偏值进行滤波处 理， 并根据调整阶段， 调整此低通滤波器使用的滤波系数的值。
频偏调整控制模块可设置成通过对合并频偏值釆用以下方式进行调整控 制来确定
≤中/
Figure imgf000005_0001
其中， A 表示调整控制参数， ¾T是当前频偏调整过程中的合并 频偏值， ¾ β是上一次频偏调整过程中的合并频偏值， ¾ :。是当前频偏调整 过程中对压控振荡器的频偏调整值， f:是上一次频偏调整过程中对压控振 荡器的频偏调整值。 频偏调整控制模块可设置成： 将对总体接收信号的频偏 调整值确定为 f - 。； 将对各径接收信号的频偏调整值确定为 Δ —If , 是径 i信号的频偏值。
该装置还可包括频偏补偿模块， 该频偏补偿模块可设置成根据频偏调整 控制模块所确定的频偏调整值对应的相角以及坐标旋转数字计算机算法进行 频偏补偿。
釆用本发明所述方法和装置， 与现有技术相比， 选择新的小范围频偏估 计方法，使频偏估计更加准确；釆用坐标旋转数字计算机（Coordinate Rotation Digital Computer, 简称 CORDIC )算法， 节省了硬件资源， 且计算精度得到 提高； 频偏调整控制策略使射频调整更加平緩， 使系统的稳定性得到加强。 附图概述
图 1是实现自动频率控制的装置的结构图；
图 2A是频偏估计相关运算结构图一；
图 2B是频偏估计相关运算结构图二；
图 2C是频偏估计相关运算结构图三；
图 3是 Rake接收机中 AFC总体方案一；
图 4是 Rake接收机中 AFC总体方案二；
图 5是 CORDIC算法的实现流水结构图；
图 6是实现自动频率控制的方法流程图。
本发明的较佳实施方式
如图 1所示， 实现自动频率控制的装置包括依次相连的相关计算模块、 频偏计算模块， 频偏调整控制模块、 频偏补偿模块。
下面分别说明各模块的功能。
( 1 )相关计算模块，用于提取各径接收信号中的公共导频符号（ CPICH ), 计算各径接收信号中公共导频符号的相关值， 具体的， 针对各径信号在一时 隙中接收到的多个公共导频符号进行相关计算， 得到相关值， 计算的方法描 述如下：
假定相关计算模块接收的 CPICH符号为 Wt) , 为了去除空时发送分集 ( STTD )发送图样的影响， 可以对一个时隙接收的公共导频信道（CPICH ) 中部分导频符号进行相关计算，通过符号间的相关达到消除信道影响的目的， 例如只对第 1到第 8导频符号进行相关计算。
符号间的相关计算模式涉及到频偏估计结果的范围和精度， 分为大范围 频偏估计和小范围频偏估计。 大范围频偏估计精准度不高， 适合于频偏捕获 状态； 小范围频偏估计精准度高， 适合于频偏跟踪状态。 频偏捕获状态一般 由初始小区搜索模块内部完成。 Rake接收机中， 主要针对经历初始频偏捕获 及补偿后的频偏跟踪调整 涉及频偏较大范围的估算方法，相关值 C的计算如图 2A以及下式所示:
1 4 » 涉及频偏较小范围估算， 进行相关计算的两符号间间隔的符号个数 L是 大于等于 2的整数； 以 L取值是 4为例的方式一， 如图 2B以及下式所示：
Figure imgf000007_0001
以 L取值是 4为例的方式二 如图 2C以及下式所示:
Figure imgf000007_0002
另外，考虑到对于单个时隙 CPICH符号相关进行频偏估计噪声影响过大 的原因， 还可以通过若干时隙间的相关值累加平均予以减弱。
( 2 )频偏计算模块， 用于计算各径接收信号的频偏值；
频偏计算模块， 还用于根据相关计算模块输出的相关值和进行相关运算 时使用的 L值计算此相关值对应的频偏值。
具体计算方法如下式所示：
Im(C)
Αω =—— arctan
TL Re(C) 其中， J是进行相关计算的两符号间间隔的符号个数。 7为单位符号的持 续时间， 为 1/15000。 进一步， 得到的频偏为
^ Αω 7500 Im(C)
AJ = = ~― arctanl
2π τί Re(C) 由该公式可知， 频偏的计算范围由 J决定。 例如： 当 J为 1时， 测量的频 偏极限为 ± 7.5KHz, 频偏估计范围很广，但是估算的精度有限，适合于初始频 偏捕获， 可应用于初始小区搜索模块中。 当 J选取 4 , 测量的频偏极限为 ± 1.75KHz, 估计精度很精准， 且能满足由于高速运动引起多普勒频移估算范 围要求， 适合于频偏跟踪调整状态。 发明中涉及的是在经历初始频偏调整后 Rake中的精准 AFC调整。 WCDMA系统可通过选取合适的相关模块计算， 可达到不同精度和范围的 AFC控制。 ( 3 )频偏调整控制模块， 用于根据各径接收信号的频偏值计算得到合并 频偏值， 并根据所述合并频偏值确定对压控振荡器的频偏调整值、 对总体接 收信号（即总体接收 I, Q数据）的频偏调整值以及对各径接收信号的频偏调 整值。
频偏调整控制模块根据各径信号的信干比 （SIR ) 门限判断各径信号的 频偏值是否有效， 去除无效的频偏值。 此处， 信干比（SIR ) 门限可以如图 3 所示根据接收到的 CPICH符号进行估算，也可以如图 4所示由系统中的多径 搜索模块直接给出。
频偏调整控制模块对有效的频偏值进行加权合并后得到合并频偏值， 如 下式所示, Af = ^jwi - Δ J； w0 + wl + ... + wN_x = 1 , 指第 i个有效的频偏值。 各 径信号频偏值的加权参数由相应的公共导频符号信干比在各径公共导频符号 信干比之和中的比重确定。 若 57 表示指峰 i的 SIR, 则
^=J^~ 且 其中 为控制门限 (M为超过门限的有效径数)。
下一步， 调整控制模块釆用低通滤波器对合并频偏值进行滤波处理， 此 低通滤波器可以是一阶无限长脉冲响应滤波器（IIR )低通滤波器， 根据不同 的调整阶段， 调整其滤波系数。 例如初始时选取较大的滤波系数， 如 1/2, 数 个调整周期后， 选取稍小的滤波系数， 如 1/4; 作用是在调整开始时使滤波效 果能较快的跟随当前频偏估计值， 跟随后能起到良好的滤波作用。
下一步， 频偏调整控制模块的对频偏值的调整分为三部分：
《1》 ， 对压控振荡器（VCO ) 的频偏补偿
≤中/
Figure imgf000008_0001
为调整控制参数， F为系统设定的频率值， , 为大于 0小于 1的实数， Τ为大于 0的实数。 一般情况下， F取值为 50Ηζ, 为 1/2, β为
1/4, 为 2。 ¾T是当前频偏调整过程中的合并频偏值， ¾ β是上一次频 偏调整过程中的合并频偏值， ^：。是当前频偏调整过程中对压控振荡器的频 偏调整值， ¾ 是上一次频偏调整过程中对压控振荡器的频偏调整值。
《2》对总体接收信号的频偏补偿
由合并频偏值和压控振荡器（VCO )频偏调整值， 得到总体接收信号的 频偏补偿值为 f - vco ,其釆用频偏补偿模块中的 CORDIC算法进行补偿。
《3》对各径接收信号的频偏补偿
釆用 CORDIC算法对各径接收信号进行补偿即对 finger ( finger指 RAKE 接收机中的指峰， RAKE接收机的每个 finger负责每个多径信号的接收与跟 踪）内部频偏进行补偿， 频偏补偿值为各径频偏值与合并频偏调整值的差值， 即 Δ - 是径 i的频偏值， i为大于等于 0小于等于 N-1的整数， N为 finger的个数， 可达到 finger内部残余频偏的快速细微的补偿。
( 4 )频偏补偿模块， 用于根据频偏调整值对应的相角以及坐标旋转数字 计算机算法进行频偏补偿。 若输入的接收信号的表示为 x + jy , 则进行频偏补偿得到：
Zde rot = cos^-_y sin ^ + j(y cos^+ sin ^)
这里 φ为接收信号样点的补偿频偏的相位旋转量， 其值通过 1π /At计算， 其中 At为信号样点间的时间间隔； /为计算的频偏补偿值， 由上面可知， 对 于总的输入信号其值为 AFC启动后频偏调整^^-¾ 的累计值， 相应各径 接收信号其值为 AFC启动后频偏调整 Δ - r的累计值。 对于上式处理， 传 统的方法釆用查表算法或者三角变化法， 考虑资源代价， 实现精度有限。 本 发明中釆用 CORDIC ( Coordinate Rotation Digital Computer, 简称 CORDIC ) 算法实现便能达到实现简单， 且资源代价不大， 精度高等特点。 其具体算法 下
Figure imgf000009_0001
zi+l = z{ - σ{ arctan(2"! )
迭代次数一般是由计算精度确定， 可量化到一个确定值。 其中 x。= x , yQ = y , Ζο = φ , a^ sign^- ^ ] , 为迭代次序， 最终迭代输 出的值即接收信号数据通过频偏补偿得到值。 对于幅值因子
Figure imgf000010_0001
迭代次数6足够的情况下为一常数， 也可转化为常数移位加运算。 CORDIC 在实现过程中， 完全可釆用移位加运算流水线结构实现， 具有高效易行性， CORDIC实现的流水单元结构如图 5所示。 如图 6所示， 实现自动频率控制的方法包括： 计算各径接收信号中公共 导频符号的相关值以及频偏值， 根据各径接收信号的频偏值计算得到合并频 偏值， 并根据所述合并频偏值确定对压控振荡器的频偏调整值、 对总体接收 信号（即总体接收 I, Q数据）的频偏调整值以及对各径接收信号的频偏调整 值。
上述方法的实现顺序与上述装置说明中相关计算模块、 频偏计算模块， 频偏调整控制模块和频偏补偿模块依次执行相应功能的流程相同， 具体实现 方法与模块功能对应， 此处不再赘述。
以上所述仅为本发明的优选实施例而已， 并不用于限制本发明， 对于本 领域的技术人员来说， 本发明可以有各种更改和变化。 凡在本发明的精神和 原则之内， 所作的任何修改、 等同替换、 改进等， 均应包含在本发明的保护 范围之内。
工业实用性
与现有技术相比， 本发明具有以下有益效果： 使频偏估计更加准确； 节 省了硬件资源， 且计算精度得到提高； 并且使系统的稳定性得到加强。

Claims

权 利 要 求 书
1、 一种实现自动频率控制的方法， 包括：
计算各径接收信号中公共导频符号的相关值以及频偏值， 根据各径接收 信号的频偏值计算得到合并频偏值， 并根据所述合并频偏值确定对压控振荡 器的频偏调整值、 对总体接收信号的频偏调整值以及对各径接收信号的频偏 调整值。
2、 如权利要求 1所述的方法， 其中， 计算各径接收信号中公共导频符 号的相关值以及频偏值的步骤包括：
针对各径接收信号在一时隙中接收到的多个公共导频符号进行相关计 算， 得到所述相关值， 其中进行相关计算的两符号间间隔的符号个数 L是大 于等于 2的整数； 以及
根据所述相关值和所述符号个数 L计算此相关值对应的频偏值。
3、 如权利要求 1所述的方法， 其中， 根据各径接收信号的频偏值计算得 到合并频偏值的步骤包括：
根据各径接收信号的信干比门限判断各径接收信号的频偏值是否有效， 对有效的频偏值进行加权合并后得到合并频偏值， 其中各径接收信号的频偏 值的加权参数由该频偏值对应的公共导频符号信干比在各径公共导频符号信 干比之和中的比重确定。
4、 如权利要求 3所述的方法， 还包括： 釆用低通滤波器对合并频偏值进 行滤波处理， 并根据调整阶段， 调整此低通滤波器使用的滤波系数的值。
5、 如权利要求 1、 2、 3或 4所述的方法， 其中， 所述对压控振荡器的频 偏调 来确定：
Figure imgf000011_0001
其中， A 表示调整控制参数， ¾T是当前频偏调整过程中的合并 频偏值， ¾ β是上一次频偏调整过程中的合并频偏值， ¾ :。是当前频偏调整 过程中对压控振荡器的频偏调整值， f:是上一次频偏调整过程中对压控振 荡器的频偏调整值。
6、 如权利要求 5所述的方法， 其中，
对总体接收信号的频偏调整值被确定为 广 - vco；
对各径接收信号的频偏调整值被确定为
Figure imgf000012_0001
A/是径 i接收信号的 频偏值。
7、 如权利要求 6所述的方法， 还包括： 根据所确定的频偏调整值对应的 相角以及坐标旋转数字计算机算法进行频偏补偿。
8、一种实现自动频率控制的装置， 包括相连的相关计算模块和频偏计算 模块，所述相关计算模块设置成计算各径接收信号中公共导频符号的相关值； 所述频偏计算模块设置成计算各径接收信号的频偏值； 其特征在于， 所述装 置还包括与所述频偏计算模块相连的频偏调整控制模块；
所述频偏调整控制模块设置成根据各径接收信号的频偏值计算得到合并 频偏值， 并根据所述合并频偏值确定对压控振荡器的频偏调整值、 对总体接 收信号的频偏调整值以及对各径接收信号的频偏调整值。
9、 如权利要求 8所述的装置， 其中， 所述相关计算模块是设置成通过 如下方式计算各径接收信号中公共导频符号的相关值： 针对各径接收信号在 一时隙中接收到的多个公共导频符号进行相关计算， 得到所述相关值， 其中 进行相关计算的两符号间间隔的符号个数 L是大于等于 2的整数；
所述频偏计算模块是设置成通过如下方式计算各径接收信号的频偏值： 根据所述相关计算模块所计算出的相关值和所述符号个数 L计算此相关值对 应的频偏值。
10、 如权利要求 8所述的装置， 其中， 所述频偏调整控制模块是设置成 通过如下方式计算得到合并频偏值：
根据各径接收信号的信干比门限判断各径接收信号的频偏值是否有效， 对有效的频偏值进行加权合并后得到合并频偏值， 其中各径接收信号的频偏 值的加权参数由该频偏值对应的公共导频符号信干比在各径公共导频符号信 干比之和中的比重确定。
11、 如权利要求 10所述的装置， 其中，
所述频偏调整控制模块还设置成釆用低通滤波器对合并频偏值进行滤波 处理， 并根据调整阶段， 调整此低通滤波器使用的滤波系数的值。
12、 如权利要求 8、 9、 10或 11所述的装置， 其中，
所述频偏调整控制模块是设置成通过对合并频偏值釆用以下方式进行调 整控制来确定对压控振荡器的频偏调整值：
≤中/
Figure imgf000013_0001
其中， F,", A 表示调整控制参数， ¾T是当前频偏调整过程中的合并 频偏值， ¾ β是上一次频偏调整过程中的合并频偏值， ¾ :。是当前频偏调整 过程中对压控振荡器的频偏调整值， f:是上一次频偏调整过程中对压控振 荡器的频偏调整值。
13、 如权利要求 12所述的装置， 其中，
所述频偏调整控制模块是设置成： 将对总体接收信号的频偏调整值确定 为 f - f o； 以及将对各径接收信号的频偏调整值确定为 Δ -~ , 是 径 i接收信号的频偏值。
14、 如权利要求 13所述的装置， 还包括频偏补偿模块， 所述频偏补偿模块设置成根据所述频偏调整控制 模块所确定的频偏调整值所对应的相角以及坐标旋转数字计算机算法进行频 偏补偿。
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