TWI403132B - Demodulation module, signal analyzer and signal analyzing method - Google Patents
Demodulation module, signal analyzer and signal analyzing method Download PDFInfo
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本發明係關於一種載波頻率飄移之估計方法,特別關於一種適用於多重路徑傳輸通道之載波頻率飄移估計方法。The present invention relates to a method for estimating carrier frequency drift, and more particularly to a carrier frequency drift estimation method suitable for multipath transmission channels.
在無線通訊系統中,由於震盪頻率不精確以及都普勒效應(Doppler Effect),因而在傳送端與接收端之間可能產生載波頻率飄移(Carrier Frequency Offset,簡稱CFO)的問題。尤其是在正交分頻多工(Orthogonal frequency division multiplexing,簡稱OFDM)系統中,載波頻率飄移所產生的影響更為嚴重。由於正交分頻多工之傳輸系統為多載波系統,對於載波頻率飄移十分敏感,載波頻率飄移會破壞正交分頻多工系統中子載波間的正交性,因而造成了子載波間互相干擾(Inter-Carrier Interference,簡稱ICI),使得正交分頻多工系統之系統效能變差、並且發生錯誤率增加等問題。因此,如何準確地估計載波頻率飄移以解決載波間互相干擾(ICI)成為正交分頻多工系統極需被解決的重要課題。In wireless communication systems, carrier frequency offset (CFO) may occur between the transmitting end and the receiving end due to inaccurate oscillation frequency and Doppler effect. Especially in the Orthogonal Frequency Division Multiplexing (OFDM) system, the impact of carrier frequency drift is more serious. Since the transmission system of orthogonal frequency division multiplexing is a multi-carrier system, it is very sensitive to carrier frequency drift, and the carrier frequency drift will destroy the orthogonality between subcarriers in the orthogonal frequency division multiplexing system, thus causing mutual carriers. Inter-Carrier Interference (ICI) makes the system performance of the orthogonal frequency division multiplexing system worse, and the error rate increases. Therefore, how to accurately estimate carrier frequency drift to solve inter-carrier interference (ICI) becomes an important issue that needs to be solved in orthogonal frequency division multiplexing systems.
根據本發明之一實施例,一種解調變模組包括類比至數位轉換器、基頻混頻器、時序回復裝置、信號分析裝置以及解碼器。類比至數位轉換器轉換一類比中頻信號,以輸出一數位中頻信號。基頻混頻器接收該數位中頻信號,並且根據一載波頻率降頻該數位中頻信號以產生一基頻信號,其中該基頻混頻器更根據一第一回授控制信號調整該載波頻率,以補償該載波頻率之載波頻率飄移。時序回復裝置根據一第二回授控制信號重新取樣該基頻信號。信號分析裝置接收該基頻信號,分析該基頻信號與一預定虛擬雜訊序列之相關性以得到複數相關性結果,並加強該等相關性結果以產生一相關性序列,並且根據該相關性序列產生該第一回授控制信號及該第二回授信號。解碼器用以解碼該時序回復裝置之一輸出信號,以產生一解碼輸出信號。According to an embodiment of the invention, a demodulation module includes an analog to digital converter, a baseband mixer, a timing recovery device, a signal analysis device, and a decoder. The analog to digital converter converts an analog IF signal to output a digital IF signal. The baseband mixer receives the digital intermediate frequency signal, and down-converts the digital intermediate frequency signal according to a carrier frequency to generate a baseband signal, wherein the baseband mixer further adjusts the carrier according to a first feedback control signal Frequency to compensate for carrier frequency drift of the carrier frequency. The timing recovery device resamples the baseband signal according to a second feedback control signal. The signal analysis device receives the baseband signal, analyzes the correlation between the baseband signal and a predetermined virtual noise sequence to obtain a complex correlation result, and enhances the correlation results to generate a correlation sequence, and according to the correlation The sequence generates the first feedback control signal and the second feedback signal. The decoder is configured to decode an output signal of the timing recovery device to generate a decoded output signal.
根據本發明之另一實施例,一種信號分析裝置包括相關性計算裝置、符元邊際偵測裝置、以及載波頻率飄移估計裝置。相關性計算裝置接收一輸入信號,根據複數不同之延遲量延遲該輸入信號以得到複數延遲信號,並計算該等延遲信號與一預定虛擬雜訊序列之相關性,以得到複數相關性計算結果,以及根據該等相關性計算結果產生一相關性序列。符元邊際偵測裝置根據該相關性序列偵測具有最大相關性之一取樣點,並且根據該取樣點之一相關性數值產生一符元邊際指示信號。載波頻率飄移估計裝置根據該符元邊際指示信號估計一載波頻率飄移量。According to another embodiment of the present invention, a signal analysis apparatus includes a correlation calculation device, a symbol margin detection device, and a carrier frequency drift estimation device. The correlation computing device receives an input signal, delays the input signal according to a plurality of different delay amounts to obtain a complex delayed signal, and calculates a correlation between the delayed signals and a predetermined virtual noise sequence to obtain a complex correlation calculation result, And generating a correlation sequence based on the results of the correlation calculations. The symbol margin detecting means detects one of the sampling points having the largest correlation according to the correlation sequence, and generates a symbol margin indicating signal according to the correlation value of the sampling point. The carrier frequency drift estimating means estimates a carrier frequency drift amount based on the symbol marginal indication signal.
根據本發明之另一實施例,一種信號分析方法包括:接收一輸入信號,其中該輸入信號至少包括一數據資料與一虛擬雜訊序列;根據複數不同之延遲量延遲該輸入信號,以得到複數延遲信號;計算該等延遲信號與一預定虛擬雜訊序列之相關性,以得到複數相關性計算結果;根據該等相關性計算結果產生一相關性序列;以及根據該相關性序列估計該輸入信號之一載波頻率飄移量。According to another embodiment of the present invention, a signal analysis method includes: receiving an input signal, wherein the input signal includes at least one data material and a virtual noise sequence; delaying the input signal according to a plurality of different delay amounts to obtain a complex number Delaying a signal; calculating a correlation between the delayed signals and a predetermined virtual noise sequence to obtain a complex correlation calculation result; generating a correlation sequence based on the correlation calculation results; and estimating the input signal according to the correlation sequence One carrier frequency drift amount.
為使本發明之製造、操作方法、目標和優點能更明顯易懂,下文特舉幾個較佳實施例,並配合所附圖式,作詳細說明如下:In order to make the manufacturing, operating methods, objects and advantages of the present invention more apparent, the following detailed description of the preferred embodiments and the accompanying drawings
數位地面多媒體/電視廣播(Digital terrestrial multimedia/television broadcasting,簡稱DTMB)系統為近年來新發展出來的數位電視廣播系統規格。DTMB的技術包括將已知的虛擬雜訊(Pseudo Noise,簡稱PN)序列填入保護區間內,用以保護資料訊號,並且可進一步用以辨識數據資料的起始位置。第1a-1b圖係顯示DTMB之資料結構。如圖所示,資料100與101為一訊框(frame)之DTMB之資料,其中資料101為將資料100延遲D個取樣點之結果。資料100與101分別包括PN序列(標示為PN code)的部分以及數據資料(標示為Data)的部分,其中PN序列尾端部份會再被重複添加於PN序列之首(標示為Pre PN),並且PN序列的頭部會再被重複添加於PN序列之尾端(標示為Post PN)。例如,DTMB可使用PN420規格,其中數據資料前可一共添加420點之PN序列,包含一筆完整的255點PN序列,並且添加其中82點於PN序列的前半部形成Pre PN部分,以及添加其中83點於PN序列的後半部形成Post PN部分,於是形成長度共420點的序列。The digital terrestrial multimedia/television broadcasting (DTMB) system is a newly developed digital television broadcasting system specification in recent years. The DTMB technology involves filling a known Pseudo Noise (PN) sequence into the guard interval to protect the data signal and further identifying the starting position of the data. Figure 1a-1b shows the data structure of DTMB. As shown, the data 100 and 101 are the data of a DTMB of a frame, wherein the data 101 is the result of delaying the data 100 by D sampling points. The data 100 and 101 respectively include a portion of the PN sequence (labeled as PN code) and a portion of the data data (labeled as Data), wherein the tail portion of the PN sequence is repeatedly added to the beginning of the PN sequence (labeled as Pre PN). And the header of the PN sequence is repeatedly added to the end of the PN sequence (labeled Post PN). For example, the DTMB can use the PN420 specification, in which a 420-point PN sequence can be added before the data, including a complete 255-point PN sequence, and 82 points are added to the first half of the PN sequence to form the Pre PN portion, and 83 of them are added. The Post PN portion is formed at the second half of the PN sequence, thus forming a sequence of 420 points in length.
由於接收端已知傳送端所添入之PN序列的內容,因此藉由將接收機所接收到的DTMB資料(例如第1圖所示之資料100)之共軛複數與DTMB資料延遲D個取樣點之結果(例如第1圖所示之資料101)進行相乘運算後,再將運算結果與接收機本地端所儲存之PN序列執行相關性(correlation)的運算,找出具有最大相關性的取樣點max(Corr D (n )),以達到數據資料同步。其中,具有最大相關性的取樣點代表著本地端所儲存的PN序列在此取樣點與接收到的DTMB資料最為匹配,一旦PN序列之匹配完成,即可得到接收信號中PN序列的起始位置,接著,便可藉由PN序列之位置辨識出數據資料起始位置,達到數據資料同步。計算相關性之範例可進一步參考由Ling-Long Dai等人於2008年11月在電機與電子工程師學會(Institute of Electrical and Electronic Engineers,簡稱IEEE)通訊系統國際會議(International Conference on Communications Systems,簡稱ICCS)所發表之技術文獻,標題為「時域同步正交分頻多工系統中新的頻率同步演算法」(A new frequency synchronization algorithm in the TDS-OFDM systems)。Since the receiving end knows the content of the PN sequence added by the transmitting end, the conjugate complex number of the DTMB data (for example, the data 100 shown in FIG. 1) received by the receiver is delayed by D sampling with the DTMB data. The result of the point (for example, the data 101 shown in FIG. 1) is multiplied, and then the operation result is correlated with the PN sequence stored at the local end of the receiver to find the correlation with the greatest correlation. Sample point max ( Corr D ( n )) to achieve data synchronization. The sampling point with the largest correlation represents that the PN sequence stored at the local end matches the received DTMB data at this sampling point. Once the matching of the PN sequence is completed, the starting position of the PN sequence in the received signal can be obtained. Then, the data data synchronization can be achieved by recognizing the starting position of the data data by the position of the PN sequence. Examples of computational correlations can be further referenced by Ling-Long Dai et al. in November 2008 at the Institute of Electrical and Electronic Engineers (IEEE) International Conference on Communications Systems (ICCS). The published technical literature is entitled "A new frequency synchronization algorithm in the TDS-OFDM systems".
除了達到數據資料之時序同步之外,接收機可進一步利用所得到的最大相關性計算結果max(Corr D (n ))估計出傳輸通道所產生之載波頻率飄移Δf ,其中載波頻率飄移Δf 之估計方法如下:In addition to achieving the timing synchronization of the data, the receiver can further estimate the carrier frequency drift Δ f generated by the transmission channel by using the obtained maximum correlation calculation result max( Corr D ( n )), wherein the carrier frequency drifts Δ f The estimation method is as follows:
其中fs 為一取樣頻率(第4圖,類比至數位轉換器403的取樣頻率)。Where fs is a sampling frequency (Fig. 4, analog to the sampling frequency of the digital converter 403).
然而,在多重路徑(multi-path)之傳輸通道環境中,由於接收端所接收到的訊號可包含來自一個以上傳輸路徑之DTMB資料,因此在進行相關性運算時,除了理論上應具有最大相關性的所求項(Desired term)之外,還會額外產生多個相關性不小之錯誤項(False term),甚至錯誤項的相關性與所求項相當或更大。所求項為理論上PN序列最為匹配的取樣點(具有最大相關性),也就是理論上接收到的DTMB資料之共軛複數與DTMB資料之延遲版本之相乘的結果再與本地端的PN序列進行相關性運算後應具有最大相關性的取樣點,代表著在此取樣點,本地端的PN序列與接收到的DTMB資料中的PN序列達到同步,而其它取樣點則為錯誤項。第2圖係顯示多重路徑傳輸通道環境中接收信號之相關性運算結果,其中橫軸代表取樣點,縱軸代表相關性之計算結果,假設傳輸通道包括2個路徑,因此相關性之計算結果理論上應包括兩個相關性較強的所求項201。然而,一旦錯誤項202的相關性因多重路徑之通道響應所產生的效應因而高於所求項時,會導致在尋找最大相關性之取樣點max(Corr D (n ))時得到錯誤的結果,如此一來,不僅造成錯誤的數據資料同步,並且也導致錯誤的載波頻率飄移估計結果。However, in a multi-path transmission channel environment, since the signal received by the receiving end can contain DTMB data from more than one transmission path, in addition to the theoretical maximum correlation, the correlation operation should be performed. In addition to the Desired term, there are a number of additional False terms, and even the relevance of the error term is equal to or greater than the requested term. The term is the most closely matched sampling point of the PN sequence (with maximum correlation), that is, the result of multiplying the conjugate complex number of the theoretically received DTMB data with the delayed version of the DTMB data and the PN sequence at the local end. The sampling point that should have the greatest correlation after the correlation operation represents that at this sampling point, the PN sequence at the local end is synchronized with the PN sequence in the received DTMB data, and the other sampling points are error items. Figure 2 shows the correlation operation results of the received signals in the multipath transmission channel environment, where the horizontal axis represents the sampling point and the vertical axis represents the calculation result of the correlation. It is assumed that the transmission channel includes two paths, so the calculation result of correlation calculation It should include two more relevant items 201. However, once the correlation of the error term 202 is higher than the expected term due to the channel response of the multipath, it will result in an erroneous result when looking for the maximum correlation sampling point max( Corr D ( n )). In this way, not only the erroneous data data is synchronized, but also the wrong carrier frequency drift estimation result.
第3a-3b圖係顯示在多重路徑傳輸通道環境中載波頻率飄移之估計以及對應補償結果,其中橫軸代表訊框索引(frame index),縱軸代表根據如式(1)所述之方法進行載波頻率飄移估計之結果Δf 。更詳細的說,第3a圖根據所求項估計載波頻率飄移,來進行補償的結果,第3b圖是根據錯誤項估計載波頻率飄移,來進行補償的結果。如第3a圖所示,若可找到正確的所求項,則可準確地估計出的載波頻率飄移Δf ,在此範例中,訊框索引為0時,根據所求項估計的實際的載波頻率飄移為100kHz。接著根據估計出來的載波頻率漂移Δf 來補償載波頻率,經過一段時間補償後,可使得實際的載波頻率飄移收斂於0kHz。然而,若是根據錯誤項進行載波頻率飄移之估計,則無法估計出實際的載波頻率飄移Δf 。也就是說,若根據錯誤項估計的載波頻率飄移Δf 來補償,則實際的載波頻率飄移則無法收歛於0kHz。如第3b圖所示,訊框索引為0時,根據錯誤項估計的載波頻率飄移為200kHz(而非實際的載波頻率飄移100kHz),若根據此載波頻率飄移200kHz來補償,經過一段時間補償後,使得實際的載波頻率飄移為-100kHz,而非收斂於0kHz。有鑑於此,本發明提出一種新的載波頻率飄移估計方法以精確地估計出正確的索求項,此載波頻率飄移估計方法不僅適用於單路徑傳輸通道環境,更適用於多重路徑傳輸通道環境,用以精確地完成數據資料同步,並且精確地估計出載波頻率飄移。The 3a-3b diagram shows the estimation of the carrier frequency drift in the multipath transmission channel environment and the corresponding compensation result, wherein the horizontal axis represents the frame index and the vertical axis represents the method according to the equation (1). The result of carrier frequency drift estimation is Δ f . In more detail, Fig. 3a is a result of estimating the carrier frequency drift based on the estimated term, and Fig. 3b is a result of estimating the carrier frequency drift based on the error term. As shown in Figure 3a, if the correct term can be found, the carrier frequency drift Δ f can be accurately estimated. In this example, when the frame index is 0, the actual carrier estimated based on the found term is obtained. The frequency drift is 100kHz. The carrier is then estimated frequency shift Δ f to compensate for carrier frequency compensation over time, such that the actual carrier frequency may drift converges to 0kHz. However, if the carrier frequency drift estimate of the error term is not possible to estimate the actual carrier frequency drift Δ f. That is, if to compensate for the error term estimated carrier frequency drift Δ f, the actual carrier frequency drift can not converge to 0kHz. As shown in Figure 3b, when the frame index is 0, the carrier frequency estimated according to the error term drifts to 200 kHz (instead of the actual carrier frequency drifting 100 kHz). If the carrier frequency is shifted by 200 kHz to compensate, after a period of compensation. So that the actual carrier frequency drifts to -100 kHz instead of converge to 0 kHz. In view of this, the present invention proposes a new carrier frequency drift estimation method to accurately estimate the correct request. This carrier frequency drift estimation method is not only suitable for a single path transmission channel environment, but also suitable for a multipath transmission channel environment. Used to accurately complete data synchronization and accurately estimate carrier frequency drift.
第4圖係顯示根據本發明之一實施例所述之接收機400。接收機400包括一調諧器(tuner)401與一解調變模組402。調諧器401將由天線所接收之射頻信號SRF 轉換為類比之中頻信號。解調變模組402可整合為一解調變器IC,用以自調諧器401接收類比之中頻信號,並且解調此信號以產生輸出信號SOUT (Transport Stream)。Figure 4 is a diagram showing a receiver 400 in accordance with an embodiment of the present invention. The receiver 400 includes a tuner 401 and a demodulation module 402. The tuner 401 converts the RF signal S RF received by the antenna into an analog intermediate frequency signal. The demodulation module 402 can be integrated into a demodulator IC for receiving an analog intermediate frequency signal from the tuner 401 and demodulating the signal to produce an output signal S OUT (Transport Stream).
根據本發明之一實施例,解調變模組402可包括類比至數位轉換器(Analog to digital converter,簡稱ADC)403、基頻混頻器404、時序回復裝置405、等化器406、解碼器407、以及信號分析裝置408。類比至數位轉換器403用以根據一取樣頻率(式(1),fs )取樣類比之中頻信號,以輸出數位中頻信號。基頻混頻器404根據一載波頻率將數位中頻信號進行降頻轉換,以產生數位基頻信號SB 。信號分析裝置408用以分析數位基頻信號SB 中虛擬雜訊序列的特性,並根據虛擬雜訊序列的特性分別產生回授控制信號SC 與ST 分別至基頻混頻器404與時序回復裝置405,其中基頻混頻器404根據回授控制信號SC 所提供之資訊改變載波之頻率,用以補償載波頻率偏移,並且時序回復裝置405根據回授控制信號ST 所提供之時序同步資訊重新取樣數位基頻信號SB ,用以將信號回復至與傳送端同步之時序。等化器406等化時序回復裝置405之輸出信號,用以補償傳輸通道之頻率響應,以除去傳輸通道所造成的影響。等化器406在此實施例中為非必要元件。解碼器407最後解碼等化過的信號,以輸出信號解碼過的信號SOUT 。According to an embodiment of the present invention, the demodulation module 402 can include an analog to digital converter (ADC) 403, a baseband mixer 404, a timing recovery device 405, an equalizer 406, and decoding. The device 407 and the signal analysis device 408. The analog to digital converter 403 is configured to sample the analog intermediate frequency signal according to a sampling frequency (equations (1), fs ) to output a digital intermediate frequency signal. The baseband mixer 404 downconverts the digital intermediate frequency signal according to a carrier frequency to generate a digital baseband signal S B . The signal analysis device 408 is configured to analyze the characteristics of the virtual noise sequence in the digital baseband signal S B , and generate the feedback control signals S C and S T to the fundamental frequency mixer 404 and the timing respectively according to the characteristics of the virtual noise sequence. The recovery device 405, wherein the baseband mixer 404 changes the frequency of the carrier according to the information provided by the feedback control signal S C to compensate for the carrier frequency offset, and the timing recovery device 405 provides the feedback control signal S T according to The timing synchronization information resamples the digital baseband signal S B to restore the signal to the timing synchronized with the transmitting end. The equalizer 406 equalizes the output signal of the timing recovery device 405 to compensate for the frequency response of the transmission channel to remove the effects of the transmission channel. Equalizer 406 is an optional element in this embodiment. The decoder 407 finally decodes the equalized signal to output the signal decoded signal S OUT .
根據本發明之一實施例,信號分析裝置408可包括一相關性計算裝置411、符元邊際偵測裝置412、時序錯誤估計裝置413、以及載波頻率飄移估計裝置414。相關性計算裝置411用以將自基頻混頻器404得到的數位基頻信號SB 之共軛複數與數位基頻信號SB 之不同延遲之版本進行相乘運算後以得到複數運算結果,再將此複數運算結果與相關性計算裝置411內所儲存之PN序列分別執行相關性(correlation)的運算,以得到複數相關性計算結果,以及根據複數相關性計算結果產生相關性序列Corr(n)。符元邊際偵測裝置412自相關性計算裝置411接收相關性序列,偵測各訊框內具有最大相關性取樣點,並紀錄此取樣點之相關性數值與位置,以產生一符元邊際指示信號SIND 。時序錯誤估計裝置413耦接至符元邊際偵測裝置412,用以根據符元邊際指示信號SIND 所指示之具有最大相關性之取樣點的位置與相關性數值(即,該取樣點之振幅)等資訊產生回授控制信號ST ,使得時序回復裝置405可根據回授控制信號ST 將數位基頻信號SB 重新取樣,用以回復至與傳送端同步之時序。載波頻率飄移估計裝置414同樣耦接至符元邊際偵測裝置412,用以根據符元邊際指示信號SIND 所指示之具有最大相關性之取樣點的相關性數值(即,該取樣點之振幅)透過如式(1)所述之方法估計載波頻率飄移,並且產生回授控制信號SC ,使得基頻混頻器404可根據回授控制信號SC 所提供之載波頻率飄移估計值Δf 補償載波頻率偏移。According to an embodiment of the present invention, the signal analysis device 408 can include a correlation calculation device 411, a symbol margin detection device 412, a timing error estimation device 413, and a carrier frequency drift estimation device 414. Correlation computing means 411 for the conjugated complex digital and digital-yl group obtained from the baseband frequency mixer 404 frequency signal S B of different delayed version of the signal S B for the multiplication result to obtain a complex operation, Further, the complex operation result and the PN sequence stored in the correlation calculating means 411 are respectively subjected to a correlation operation to obtain a complex correlation calculation result, and a correlation sequence Corr(n) is generated based on the complex correlation calculation result. ). The symbol margin detecting device 412 receives the correlation sequence from the correlation computing device 411, detects the most relevant sampling point in each frame, and records the correlation value and position of the sampling point to generate a symbol marginal indication. Signal S IND . The timing error estimating device 413 is coupled to the symbol margin detecting device 412 for determining the position and correlation value of the sampling point having the greatest correlation indicated by the symbol margin indicating signal S IND (ie, the amplitude of the sampling point) The information generates a feedback control signal S T such that the timing recovery means 405 can resample the digital baseband signal S B according to the feedback control signal S T for returning to the timing synchronized with the transmitting end. The carrier frequency drift estimating device 414 is also coupled to the symbol margin detecting device 412 for correlating the correlation value of the sampling point having the greatest correlation indicated by the symbol margin indicating signal S IND (ie, the amplitude of the sampling point) ) through methods such as formula (1) according to the estimated carrier frequency drift, and generate a feedback control signal S C, such baseband mixer 404 can be transported in accordance with the estimated value Δ f feedback control signal S C is provided by the carrier frequency Compensate for carrier frequency offset.
如上述,由於自多重路徑的傳輸通道環境中接收到的信號在計算相關性時會產生具有較大相關性的錯誤項(如第2圖所示),因而導致在尋找最大相關性之取樣點max(Corr D (n ))時得到錯誤的結果,造成錯誤的數據資料同步,以及錯誤的載波頻率飄移估計結果(如第3圖所示)。因此,根據本發明之一實施例,相關性計算裝置411在計算相關性時更進一步加強所求項之相關性,使得在得到的相關性計算結果中所求項可具有最大的相關性數值,於是符元邊際偵測裝置412可準確地找出所求項的位置,進而時序錯誤估計裝置413與載波頻率飄移估計裝置414可正確地得到時序同步資訊與載波頻率飄移的估計值。As mentioned above, since the signals received from the multipathed transmission channel environment produce a correlation item with a large correlation when calculating the correlation (as shown in Fig. 2), the sampling point for finding the maximum correlation is caused. Max( Corr D ( n )) results in erroneous results, resulting in erroneous data synchronization, as well as incorrect carrier frequency drift estimation results (as shown in Figure 3). Therefore, according to an embodiment of the present invention, the correlation computing device 411 further enhances the correlation of the found items when calculating the correlation, so that the items found in the obtained correlation calculation result may have the largest correlation value. Thus, the symbol margin detecting means 412 can accurately find the position of the requested item, and the timing error estimating means 413 and the carrier frequency drift estimating means 414 can correctly obtain the estimated values of the timing synchronization information and the carrier frequency drift.
第5a-5c圖係顯示根據本發明之一實施例所述之於多重路徑傳輸通道環境的相關性計算結果。藉由第5a-5c圖可清楚理解本發明之一實施例所述之加強所求項之概念。第5a圖係顯示根據接收到的DTMB資料之共軛複數與DTMB資料之延遲D1個取樣點(如第1圖所示)之版本進行相乘運算後,再將此運算結果與接收機本地端所儲存之PN序列執行相關性(correlation)的運算所得到的結果。如圖所示,假設取樣點n2與n4為所求項,也就是理論上PN序列最為匹配的取樣點,而位於取樣點n1、n3與n5則為錯誤項。由第5a圖可看出,由於多重路徑之通道響應所產生的效應,使得位於取樣點n1之錯誤項的相關性與位於取樣點n2之所求項的相關性相當接近,甚至大於位於取樣點n4之所求項的相關性,因此若根據如第5a圖所示之相關性計算結果是無法十分準確地找出所求項(於取樣點n2和n4)來進行時序同步與頻率偏移估計,因而發生錯誤。第5b圖係顯示另一個相關性運算結果,此結果係根據接收到的DTMB資料之共軛複數與DTMB資料之延遲D2個取樣點(如第1圖所示)之版本進行相乘運算後,再將此運算結果與接收機本地端所儲存之PN序列執行相關性(correlation)的運算所得到的結果。由第5b圖可看出,由於多重路徑之通道響應所產生的效應,使得位於取樣點n5之錯誤項的相關性大位於取樣點n2之所求項的相關性,並且大於位於取樣點n4之所求項的相關性,因而無法分辨出所求項(於取樣點n2和n4)。因此若根據如第5b圖所示之相關性計算結果進行時序同步與頻率偏移估計,則會發生錯誤。5a-5c are diagrams showing correlation calculation results for a multipath transmission channel environment in accordance with an embodiment of the present invention. The concept of the reinforcement term described in one embodiment of the present invention can be clearly understood from Figures 5a-5c. Figure 5a shows the result of multiplication between the conjugate complex number of the received DTMB data and the version of the D1 sample point (as shown in Figure 1) of the DTMB data, and then the result of the operation and the local end of the receiver. The result of the operation of the correlation performed by the stored PN sequence. As shown in the figure, it is assumed that the sampling points n2 and n4 are the obtained items, that is, the sampling points that are theoretically the most matching of the PN sequence, and the sampling points n1, n3 and n5 are the error items. It can be seen from Fig. 5a that due to the effect of the channel response of the multiple paths, the correlation of the error term at the sampling point n1 is quite close to the correlation of the term at the sampling point n2, and even greater than the sampling point. The correlation of the terms of n4, so if the correlation calculation result as shown in Fig. 5a is not able to find the exact terms (at sampling points n2 and n4) for timing synchronization and frequency offset estimation And thus an error occurred. Figure 5b shows another correlation operation result. This result is based on the multiplication of the conjugate complex number of the received DTMB data with the delay of the D2 data points of the DTMB data (as shown in Figure 1). The result of this operation is calculated by performing a correlation operation with the PN sequence stored at the local end of the receiver. It can be seen from Fig. 5b that due to the effect of the channel response of the multiple paths, the correlation of the error items located at the sampling point n5 is largely at the correlation of the terms of the sampling point n2, and is greater than the sampling point n4. The correlation of the terms is sought, so that the requested term (at sampling points n2 and n4) cannot be distinguished. Therefore, if timing synchronization and frequency offset estimation are performed based on the correlation calculation result as shown in Fig. 5b, an error occurs.
然而,如第5a與5b圖所示,由於錯誤項發生的位置會隨著延遲D的長度變化而改變,而所求項發生的位置並不會隨著延遲D的不同而改變,因此根據本發明之一實施例,藉由累加使用不同延遲所得到的相關性計算結果,加強所求項之相關性,使得所求項在得到的相關性計算結果可與錯誤項產生明顯的區隔,如第5c圖所示,累加後的所求項n2與n4的相關性與錯誤項產生明顯的區隔,如此一來,信號分析裝置408可準確地根據加強過的相關性計算結果找出所求項的正確位置,進而得到準確的時序同步與載波頻率飄移的估計值。However, as shown in Figures 5a and 5b, since the position at which the error term occurs changes with the length of the delay D, and the position at which the term occurs does not change with the delay D, In an embodiment of the invention, the correlation calculation result obtained by accumulating different delays is used to strengthen the correlation of the obtained items, so that the correlation calculation result obtained by the obtained item can be clearly distinguished from the error item, such as As shown in Fig. 5c, the correlation between the accumulated terms n2 and n4 is significantly different from the error term, so that the signal analyzing means 408 can accurately find the desired result based on the enhanced correlation calculation result. The correct position of the term, which in turn leads to an accurate estimate of timing synchronization and carrier frequency drift.
第6圖係顯示根據本發明之一實施例所述之相關性計算裝置。根據本發明之一實施例,相關性計算裝置611可包括兩組或兩組以上之運算模組。為了清楚闡述本發明之概念,第6圖顯示兩組運算模組612與613。值得注意的是本發明也可使用兩組以上之運算模組,並非限定於使用兩組運算模組,任何熟習此項技藝者,在不脫離本發明之精神和範圍內,當可做些許的更動與潤飾,因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。Figure 6 is a diagram showing a correlation computing device in accordance with an embodiment of the present invention. According to an embodiment of the present invention, the correlation computing device 611 may include two or more sets of computing modules. In order to clearly illustrate the concept of the present invention, FIG. 6 shows two sets of computing modules 612 and 613. It should be noted that the present invention can also use more than two sets of computing modules, and is not limited to the use of two sets of computing modules. Anyone skilled in the art can make some changes without departing from the spirit and scope of the present invention. The scope of protection of the present invention is defined by the scope of the appended claims.
根據本發明之實施例,各運算模組可分別包括兩組先進先出(First In First Out,簡稱FIFO)暫存器。第一組先進先出暫存器之長度分別根據不同之延遲需求而設計,例如先進先出暫存器621之長度可設計為D1,用以將輸入之數位基頻信號SB 延遲D1個取樣點,而先進先出暫存器631之長度可設計為D2,用以將輸入之數位基頻信號SB 延遲D2個取樣點。在經過共軛複數單元(conjugator,簡稱為conj)622與632將輸入之數位基頻信號SB 做共軛複數(complex conjugate)轉換後,數位基頻信號SB 之共軛複數會與其延遲D1(或D2)之版本透過乘法器623與633相乘。相乘後的結果會進一步輸入至第二組先進先出暫存器624與634。第二組先進先出暫存器624與634分別位於相關性計算單元625與635中,用以輔助相關性的運算,因此其長度可分別根據所需之相關性長度C1與C2而設計。數位基頻信號SB 之共軛複數與延遲版本相乘後的結果在相關性計算單元625與635中透過第二組先進先出暫存器624與634分別與接收機本地端所儲存之PN序列逐點相乘,並分別累加相乘結果進而得到相關性計算結果Corr_D1(n)與Corr_D2(n)。最後,透過加法器614累加得到的相關性計算結果Corr_D1(n)與Corr_D2(n),用以更進一步加強所求項之相關性,以輸出相關性序列Corr(n)。According to an embodiment of the invention, each computing module can include two sets of First In First Out (FIFO) registers respectively. The lengths of the first set of FIFO registers are respectively designed according to different delay requirements. For example, the length of the FIFO register 621 can be designed as D1 to delay the input digital baseband signal S B by D1 samples. The length of the FIFO register 631 can be designed as D2 to delay the input digital baseband signal S B by D2 sampling points. After the conjugate complex unit (conjugator, simply referred to as conj) 622 and 632 converts the input digital baseband signal S B into a complex conjugate, the conjugate complex number of the digital baseband signal S B is delayed by D1. The version (or D2) is multiplied by 633 by multipliers 623. The multiplied result is further input to the second set of FIFO registers 624 and 634. The second set of FIFO registers 624 and 634 are located in correlation calculation units 625 and 635, respectively, to aid in the operation of the correlation, and thus the lengths can be designed according to the required correlation lengths C1 and C2, respectively. The result of multiplying the conjugate complex number of the digital baseband signal S B by the delayed version is stored in the correlation computing units 625 and 635 through the second set of FIFO registers 624 and 634 and the PN stored at the local end of the receiver, respectively. The sequence is multiplied point by point, and the multiplication results are respectively accumulated to obtain correlation calculation results Corr_D1(n) and Corr_D2(n). Finally, the correlation calculation results Corr_D1(n) and Corr_D2(n) obtained by the adder 614 are accumulated to further enhance the correlation of the found terms to output the correlation sequence Corr(n).
如第5a-5c圖所示,由於錯誤項發生的位置會隨著延遲D的長度變化而改變,而所求項發生的位置並不會隨著延遲D的不同而改變,經過累加使用不同延遲所得到的相關性計算結果,可加強所求項的相關性,使得在所得到的相關性序列中所求項的相關性可與錯誤項產生明顯的區隔。因此符元邊際偵測裝置421可準確地找到之具有最大相關性之取樣點,並且如上所述產生回授控制信號SC 與ST 至基頻混頻器404與時序回復裝置405,以進行載波頻率飄移估計與時序回復。As shown in Figures 5a-5c, the position at which the error term occurs will change with the length of the delay D, and the position at which the term occurs will not change with the delay D, and different delays will be used. The resulting correlation calculation results can enhance the correlation of the items sought, so that the correlation of the items found in the obtained correlation sequence can be clearly distinguished from the error items. Therefore, the symbol margin detecting means 421 can accurately find the sampling point having the greatest correlation, and generate the feedback control signals S C and S T to the fundamental frequency mixer 404 and the timing recovery means 405 as described above for performing Carrier frequency drift estimation and timing recovery.
第7圖係顯示根據本發明之一實施例所述之信號分析方法。首先,接收一輸入信號(步驟S701),其中此輸入信號可以是如第1a圖所示之DTMB信號,包括虛擬雜訊序列(PN Code)與數據資料(Data),並且此輸入信號可以是經過基頻混頻器404執行降頻轉換後的基頻信號。接著,根據複數不同之延遲量延遲該輸入信號(步驟S702),例如,根據兩個或兩個以上不同之延遲量延遲該輸入信號,以分別得到具有不同延遲量之輸入信號。接著,計算具有該等不同之延遲量之該等輸入信號與一虛擬雜訊序列之相關性,以得到複數相關性計算結果(步驟S703)。接著,根據該等相關性計算結果產生一相關性序列(步驟S704)。最後,根據該相關性序列估計一數據資料之起始位置以及一載波頻率飄移量(步驟S705)。參考如第6圖所示之相關性計算裝置結構,其中步驟S702與步驟S703可更包括:將該輸入信號之共軛複數與具有不同之延遲量之該等輸入信號相乘,以得到複數相乘結果;以及計算該虛擬雜訊序列之與該等相乘結果之相關性,以得到該等相關性計算結果,例如第6圖所示之延遲量D1與D2,以及相關性計算結果Corr_D1(n)與Corr_D2(n)。在步驟S704中,藉由累加Corr_D1(n)與Corr_D2(n)以產生相關性序列Corr(n)。Figure 7 is a diagram showing a signal analysis method according to an embodiment of the present invention. First, an input signal is received (step S701), wherein the input signal may be a DTMB signal as shown in FIG. 1a, including a virtual noise sequence (PN Code) and a data data (Data), and the input signal may be The baseband mixer 404 performs the down-converted baseband signal. Then, the input signal is delayed according to a plurality of different delay amounts (step S702), for example, the input signals are delayed according to two or more different delay amounts to respectively obtain input signals having different delay amounts. Next, the correlation between the input signals having the different delay amounts and a virtual noise sequence is calculated to obtain a complex correlation calculation result (step S703). Next, a correlation sequence is generated based on the correlation calculation results (step S704). Finally, a starting position of a data material and a carrier frequency drift amount are estimated based on the correlation sequence (step S705). Referring to the structure of the correlation computing device as shown in FIG. 6, step S702 and step S703 may further include: multiplying the conjugate complex number of the input signal by the input signals having different delay amounts to obtain a complex phase Multiplying the result; and calculating a correlation of the virtual noise sequence with the multiplied result to obtain the correlation calculation results, such as the delay amounts D1 and D2 shown in FIG. 6, and the correlation calculation result Corr_D1 ( n) with Corr_D2(n). In step S704, the correlation sequence Corr(n) is generated by accumulating Corr_D1(n) and Corr_D2(n).
此外,參考如第4圖所示之相關性計算裝置結構,步驟S705可更包括:偵測相關性序列Corr(n)中具有最大相關性之一取樣點;根據具有最大相關性之該取樣點之一位置與一相關性數值產生一符元邊際指示信號SIND ;以及根據該符元邊際指示信號估計該數據資料之起始位置以及一載波頻率飄移量。In addition, referring to the correlation computing device structure as shown in FIG. 4, step S705 may further include: detecting one of the correlation sequences Corr(n) having the largest correlation; according to the sampling point having the largest correlation A position and a correlation value generate a symbol marginal indication signal S IND ; and a starting position of the data data and a carrier frequency drift amount are estimated based on the symbol marginal indication signal.
本發明雖以較佳實施例揭露如上,然其並非用以限定本發明的範圍,任何熟習此項技藝者,在不脫離本發明之精神和範圍內,當可做些許的更動與潤飾,因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。The present invention has been described above with reference to the preferred embodiments thereof, and is not intended to limit the scope of the present invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.
100、101...資料100, 101. . . data
201...所求項201. . . Item requested
202...錯誤項202. . . Error item
400...接收機400. . . Receiver
401...調諧器401. . . tuner
402...解調變模組402. . . Demodulation module
403...類比至數位轉換器403. . . Analog to digital converter
404...基頻混頻器404. . . Base frequency mixer
405...時序回復裝置405. . . Timing recovery device
406...等化器406. . . Equalizer
407...解碼器407. . . decoder
408...信號分析裝置408. . . Signal analysis device
411、611...相關性計算裝置411, 611. . . Correlation computing device
412...符元邊際偵測裝置412. . . Symbol edge detection device
413...時序錯誤估計裝置413. . . Timing error estimation device
414...載波頻率飄移估計裝置414. . . Carrier frequency drift estimation device
612、613...運算模組612, 613. . . Computing module
621、631、624、634、FIFO...先進先出暫存器621, 631, 624, 634, FIFO. . . FIFO register
622、632...共軛複數單元622, 632. . . Conjugate complex unit
623、633...乘法器623, 633. . . Multiplier
625、635...相關性計算單元625, 635. . . Correlation calculation unit
Corr(n)、Corr_D1(n)、Corr_D2(n)...相關性Corr(n), Corr_D1(n), Corr_D2(n). . . Correlation
D...延遲D. . . delay
Data...數據資料Data. . . data
PN、PN code、Pre PN、Post PN...虛擬雜訊序列PN, PN code, Pre PN, Post PN. . . Virtual noise sequence
SB 、SC 、SIND 、SOUT 、SRF 、ST ...信號S B , S C , S IND , S OUT , S RF , S T . . . signal
第1a-1b圖係顯示數位電視廣播資料之資料結構。Figure 1a-1b shows the data structure of digital television broadcast data.
第2圖係顯示多重路徑傳輸通道環境中接收信號之相關性運算結果。Figure 2 shows the results of the correlation operation of the received signals in the multipath transmission channel environment.
第3a-b圖係顯示多重路徑傳輸通道環境中載波頻率飄移之估計以及對應補償結果。Figure 3a-b shows the estimation of carrier frequency drift in the multipath transmission channel environment and the corresponding compensation results.
第4圖係顯示根據本發明之一實施例所述之接收機。Figure 4 is a diagram showing a receiver in accordance with an embodiment of the present invention.
第5a-5c圖係顯示根據本發明之一實施例所述之於多重路徑傳輸通道環境的相關性計算結果。5a-5c are diagrams showing correlation calculation results for a multipath transmission channel environment in accordance with an embodiment of the present invention.
第6圖係顯示根據本發明之一實施例所述之相關性計算裝置。Figure 6 is a diagram showing a correlation computing device in accordance with an embodiment of the present invention.
第7圖係顯示根據本發明之一實施例所述之信號分析方法。Figure 7 is a diagram showing a signal analysis method according to an embodiment of the present invention.
400...接收機400. . . Receiver
401...調諧器401. . . tuner
402...解調變模組402. . . Demodulation module
403...類比至數位轉換器403. . . Analog to digital converter
404...基頻混頻器404. . . Base frequency mixer
405...時序回復裝置405. . . Timing recovery device
406...等化器406. . . Equalizer
407...解碼器407. . . decoder
408...信號分析裝置408. . . Signal analysis device
411...相關性計算裝置411. . . Correlation computing device
412...符元邊際偵測裝置412. . . Symbol edge detection device
413...時序錯誤估計裝置413. . . Timing error estimation device
414...載波頻率飄移估計裝置414. . . Carrier frequency drift estimation device
SB 、SC 、SIND 、SOUT 、SRF 、ST ...信號S B , S C , S IND , S OUT , S RF , S T . . . signal
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