TW421928B - Method and apparatus used to overcome multi-route interference in multi-carry-wave digital modulation system - Google Patents

Abstract

This invention is about method and apparatus for overcoming multi-route interference, and is used in multi-carrier digital modulation system, in which the time domain delay in the multi-carrier digital modulation system is converted into the frequency domain and is changed into another adhering carrier signal. The carrier frequency is proportional to the time delay length generated by multi-route interference. Based on this relationship, the time delay length can be accurately obtained and can be quickly detected in real time. The intensity of ghost-shadow signal at time domain can be calculated from the time delay length. Through the time delay length and the intensity of the ghost-shadow signal, a resist signal is made to effectively eliminate the signal fading phenomena caused by multi-route interference.

Description

421 92 b A7 _ B7 V. Description of the invention (via # .Ministry of Foreign Affairs, UJT. Cooperative Private Printing; Field of Invention I This case is a method and device for overcoming multipath interference, especially applied to multicarrier Method and device for overcoming multipath interference in a digital modulation system. BACKGROUND OF THE INVENTION Please refer to the first figure 'It is a schematic diagram of transmitting a signal by a wireless electromagnetic wave' wherein the electromagnetic wave signal emitted by the transmitting antenna li is transmitted to a fixed location The receiving antenna 12 on the user ’s home or on the moving vehicle is used for reception, and because the electromagnetic wave signal is reflected or refracted due to factors such as the topographical environment during the transmission process, and then the so-called multipath interference problem is generated. Multipath interference will cause The phenomenon of signal fading (fading), and the phenomenon shown on the video system is a "ghost image", during which the ghost caused by multipath interference caused by obstacles fixed relative to the receiving antenna is called " "Static ghosts", and when the receiver itself moves (for example: receiving on a moving vehicle) or external factors move (For example: at the airport or near the highway) The length of the ghost and the size of the ghost in the received signal change over time are called "dynamic ghosts." In the current audio and video digital transmission system, In single-carrier modulation systems (such as Quadrature Amplitude Modulation (QAM) or Vestigial Read A and read the notes before reading and then binding), the paper size is suitable for Chinese national standards ((, NS) Λ4 specification (210X297 male thin) A2 \ V. Description of the invention (2 A7 B7 is the seal of the Military Industry Cooperative of the Ministry of Economic Affairs of the Central Ministry of Economic Affairs of the Ministry of Education)

(Sideband (VSB)), for the fading phenomenon caused by multipath interference, an adaptive channel equalizer based on the Least Mean Square algorithm (LMS) is used, and the minimum mean square algorithm uses a board The tap input, tap weights, estimation error, and cost function are used as an iterative algorithm of the matrix to determine the weight vector. With time, the weight vector, step-size parameter, and cost function versus time gradient vector are calculated several times to calculate the optimal weight vector to achieve convergence. However, the convergence speed of the least mean square algorithm (LMS) depends on the following two factors: (a) If a larger step coefficient is selected, the convergence speed will be faster, but it will also cause a larger additional mean square error. (B) If the number of contact weights increases, the convergence speed will slow down. (C) When the eigenvalues of the correlation matrix differ greatly, the convergence speed of the minimum mean square algorithm will be slower. Therefore, the decision feedback equalizer using the minimum mean square algorithm has a good equalization function for multipath interference, but has the following disadvantages: (3) When the wrong decision is fed back, 'due to the memory of the feedback delay, the decision The feedback equalizer will reflect these error cycles 'due to err〇r propagation' and may cause more errors to occur. It will be more serious when the number of contact weights or feedback points is large. (B) When the system handles dynamic fading interference, the eigenvalues of the LMS correlation matrix are very different, and the algorithm convergence speed will become slower. In addition, in the multi-carrier modulation system t, in addition to the use on the receiving end (forbidden to read the precautions on the back before ir ^ this page). Install., -T b Paper size Shizhou China national standard rate ((, NS ) Λ4 specification ('210X 297 mm via the Ministry of Justice, Central Bureau of quasi-government, Zhenggong Consumption, including Zuoshe 54 54 421 928 A7 __ B7 V. Description of the invention (3) The Estimator of the Least Mean Square Algorithm (LMS) In addition to completing the equalization work, 1 mostly uses guard interval technology and the addition of pilot signals to overcome noise caused by multipath interference. For example, the current European regulatory multi-carrier modulation In the Orthogonal Frequency Division Multiplexing (referred to as OFDM) communication system used by the system, the transmission signal is converted into a time domain signal by a fast Fourier inverse transform (IFFT) and a guard interval is added. ) The schematic diagram is shown in the second figure. The protection interval A shown in the figure must be greater than the channel impulse response time h (t), so as to ensure that the transmission signal passes through the channel at the signal code interval at the receiving end. Interference (Intersymbol Interference) falls within the protection interval △, and intra-interference (Intrasymbol Interference) falls within Ts. See also the third figure, which is the modulation in the OFDM communication system caused by multipath interference Schematic diagram of changes in the constellation diagram. In the code, the interference modulation constellation diagram will be reduced or enlarged due to the decline and decay. Rotating a certain angle will cause different changes in different channels. Especially for mobile reception or intra-frequency network signal modulation. The constellation map will produce rapid and huge changes. In addition, 'Pilot Signal' and video equalizers are also used in the voice-over-European digital transmission system to deal with the problem of intra-code interference. Therefore, it performs very well in static ghosting. However, the performance of dynamic ghost processing is not ideal. The above description can refer to (Y. Wu, B. Caron, B. Ledonx and M. Guillet " EVALUATION of COFDM FOR AT V TRANSMISSION OVER 6 Mhz 4 This paper standard is applicable to China Store label Ping ((:?) / \ 4 specifications (2 丨 0 \ 297 public 漦) -------- Γ — equipment-(铕 first read the precautions on the back and then ^^ this page) Order

Printed by the staff of the central government bureau of the Ministry of Economic Affairs of the Ministry of Economic Affairs, Cooperative Cooperative A7 ____B7 V. Description of the Invention (Battle) CHANNELS,; ,, International Broadcasting Convention, 12-16 September 1996 Conference Publication No. 428, © IEE, 1996). In this article, the Communications Research Centre (Ottawa, Canada) revised the 8-MHz Coded Orthogonal Frequency Division Multiplexing (COFDM) of the European HD-DIVINE and SINTEF DELAB to 6 MHz COFDM. In July 1995, the actual engineering test was conducted in Canada with the American Television Television Test Center (Advance Television Test Center), and compared with the US 8-VSB modulation system. From the comparison of the main transmission performance of Table 10 in the paper, it can be seen that the coded orthogonal frequency division multiplexing system (COFDM) performs better than the 8-VSB system in static ghosting and dynamic ghosting below 0.05 Hz, but 0.05 Hz The dynamic ghost processing on 4 is not as good as the 8-VSB system. The current way to correct multipath interference in European Digital TV (DTV) / Digital Audio Broadcasting (DAB) systems is to process in the frequency domain after fast Fourier transform (fft). The two types of pilot signals (P (10 σ gnal)) are divided by the two types of pilot signals at the transmitting end to generate a correction factor, and then the transmission signal of the code signal to be transmitted is divided by the correction factor. Now the European regulatory system processes The method has two disadvantages: < i > requires a large number of divisions and a large amount of calculation. ≪ ii > The size of the pilot signal at the receiving end in the frequency domain is comparable to the transmitted data signal, which is 'susceptible to noise or interference', resulting in biased correction errors Large, ghosting equalization 5. (('NS) Λ4% # (2! 0X297 mm) {谙 first read the precautions on the back and then the winter page) 线 ¾. 2. Printed by Consumption Co., Ltd. Λ :: ”9 ::. A7 _______B7 V. Description of the invention (5) The effect is poor, especially the processing of dynamic ghosting is more obvious. J Therefore, the main purpose of developing this case is to address the above-mentioned technologies Shortcomings to improve, not just for static Path interference is aimed at dynamic fading or mobile reception, and proposes a more rapid and accurate method to overcome multipath interference. Summary of the Invention This case is a method to overcome multipath interference, which is applied to the use of guidance signal technology In a multi-carrier digital modulation-demodulation system, a data to be transmitted is transmitted after the multi-carrier digital modulation procedure. The method for overcoming multipath interference includes the following steps: (a) after receiving the multipath interference effect A jammed signal is formed; (b) the jammed signal is processed into a jammed pilot signal and a jammed data signal to be transmitted through a first operation program; (c) the jammed pilot signal includes A guidance ghost signal caused by multipath interference is used to calculate a ratio between the sine wave frequency of the guidance ghost signal and the carrier frequency of the guidance signal through a second calculation program to obtain a delay time. Length; (d) using the delay time to determine the position of the pilot ghost signal and measuring the amplitude of the pilot ghost signal After dividing by the amplitude intensity of the corresponding pilot signal to obtain a ghost amplitude intensity coefficient; (e) generating an anti-ghost signal based on the delay time length and the ghost amplitude intensity coefficient and mixing into the victim The signal is used to eliminate the ghost signal caused by multi-path interference. This paper is used to obtain the Chinese standard (HMS) Λ4 specification (210X 297 mm) for this paper. S--install-/} '.! I- (锖 Please read the notes on the back before r'isvT page) Order the Central Bureau of Standards of the Ministry of Economic Affairs si-ΐConsumption Included with the Seal of the Society 4⑴20 ^ A7 _______________ B7 V. Description of the Invention Multi-carrier digitally modulated signal with path interference; and (f > demodulating the multi-carrier digitally modulated signal that has overcome multi-channel interference after demodulation) to get back the data to be transmitted. According to the above idea, the multi-carrier digital modulation-demodulation method to which the method of overcoming multipath interference is applied using pilot signal technology is to use the pilot signal and one of the protection period techniques to encode orthogonal frequency division multiplexing modulation_ Demodulation method. According to the above conception, the first operation program in the method for overcoming multipath interference includes the following steps: (bl) removing the interfered signal from its protection period and performing a fast Fourier transform to obtain an interfered symbol Signal; and (b2) separating the interfered symbol signal into the interfered pilot signal and the interfered data signal in a demultiplexed manner. According to the above idea, the second operation program in the method of overcoming multipath interference is: a value obtained by dividing the carrier frequency by the sine wave frequency of the ghost signal as the delay time length of the ghost signal. Another aspect of the present case is a device for overcoming multipath interference, which is applied to a receiving end of a multi-carrier digital modulation-demodulation system using a pilot signal technology, and the receiving end is used to receive the effect of multipath interference An interference signal formed afterwards is processed and separated into an interference guide signal and an interference data signal to be transmitted. The device for overcoming multipath interference includes: a ghost signal delay detector electrically connected to the multicarrier The receiving end of the digital modulation and demodulation system is used to calculate the sine wave frequency of the guide ghost signal and the load of the guide signal contained in the interfered guide signal. ____________ 7 Paper Size Chengzhou China S family arrested ♦ (rNS) Λ4 specification (210X 297 Gongchu) ---------- Γ — Yi Yi-I ,, ... (Read the notes on the back of the poem first and then-^-^ this P.) 4 2 9 A7 B7 Central Bureau of Standards, Ministry of Economic Affairs, only X, printed by Consumer Cooperatives 5. Description of invention (7) A ratio between wave frequencies is used to obtain a delay time length; a ghost signal amplitude Analyzer, electrically connected to this multi-carrier digital modulation The modulation system receiving end and the ghost signal delay detector are used to analyze a ghost amplitude intensity coefficient according to the interfered signal and the delay time length; and an anti-ghost circuit is electrically connected to The ghost signal amplitude analyzer, the ghost signal delay detector, and the receiving end of the multi-carrier digital modulation and demodulation system generate a ghost-like image based on the delay time and the ghost amplitude intensity coefficient. The signal is one of the delay time and amplitude of the shadow signal, and the signal is subtracted from the interfered signal to obtain a multi-carrier digitally modulated signal that has overcome multi-path interference. According to the above concept, the multi-path interference device in the The ghost signal delay detector includes: a filter electrically connected to a receiving end of the multi-carrier digital modulation-demodulation system, which is used to guide the ghost included in the interfered pilot signal Signal extraction; a sine wave number detector, electrically connected to the filter, which is used to measure the number of sine waves constituting the guide ghost signal; and a calculator, which is electrically connected to the The receiving end of the sine wave number detector wave digital modulation-demodulation system is based on the following relationship: the number of sine waves = delay time length x the number of fast Fourier transforms to find the length of the delay time. According to the above It is envisaged that the ghost signal amplitude analyzer in the device for overcoming multipath interference includes: a first signal strength detector electrically connected to the receiving end of the multi-carrier digital modulation-demodulation system, which is Θ to detect Intensity of the plurality of pilot signals in the interfered signal: a first adder, the paper standard Xichuan Chinese National Standard (C: NS) Λ4 specification (2I0X 297 mm) ----- 1-- -Ί —-(Please read the notes on the back first, then this page) -9 _ > f 421 92 8 ^ 4 A7 B7 V. Description of the invention (§) The electric signal is connected to the first signal strength detector, which It is used to accumulate the pilot signal strengths detected by the first signal strength detector to obtain a first accumulated value; a variable delay element is electrically connected to the calculator and the multi-carrier digital The receiving end of the modulation-demodulation system is based on the length of the delay time. Determining the position of the pilot ghost signal in the interfered signal; a second signal strength detector electrically connected to the variable delay element, which is used to measure the position of the pilot ghost signal at the determined position Intensity; a second adder electrically connected to the second signal intensity detector, which is used to accumulate the intensity of the guiding ghost signal detected by the second signal intensity detector; A second accumulated value; and a divider electrically connected to the first adder and the second adder, which are used to divide the second accumulated value and the first accumulated value, thereby obtaining the Ghost amplitude intensity coefficient. According to the above concept, the anti-ghost circuit in the device for overcoming multipath interference includes: an adjustable delay element electrically connected to the calculator and the receiving end of the multi-carrier digital modulation and demodulation system, which is used to The delay time length is used to produce a signal similar to the ghost signal delay time length; an adjustable multiplier electrically connected to the divider and the adjustable delay element is used to delay the ghost signal similar to the delay time length. The signal is then used to produce a signal similar to the ghost signal amplitude according to the ghost amplitude intensity coefficient; and a mixer is electrically connected to the adjustable multiplier and the receiving end of the multi-carrier digital modulation demodulation system , Which is obtained by subtracting the signal from the interfered signal to obtain a multi-carrier digitally modulated signal that has overcome multi-path interference and outputs the signal. The size of this paper is suitable for Chinese national standard (('NS) Λ4 specification (2Ι〇χ 297 mm) ---------- ^-... V-1 / (谙 read the first (iiWK items on this page)

V. Description of the invention (y) Simple diagram description This case can gain a deeper understanding through the following diagrams and detailed descriptions: First picture: It is the first diagram of a schematic diagram of transmitting signals by a wireless electromagnetic wave. It is the current European regulatory multi-Ningbo modulation system; in the Orthogonal Frequency Division Multiplexing (OFDM) communication system used by the system, the transmission signal is converted into the time domain by the inverse fast Fourier transform (IFFT) A schematic diagram of the guard interval (guard interval) is added after the signal. «Second picture: It is a schematic diagram of OFDiv [communication system changing modulation star map caused by multipath interference. Fig. 4 is a functional block diagram of the device of the preferred embodiment of the present invention applied to the coding orthogonal frequency division multiplexing system (COFDM). Fifth figure. It is a schematic diagram showing that the pilot signal is accumulatively transformed by the IFFT transform, and the amplitude of the time domain is increased by dozens of times. Η ° ”Goods of the Central Standards Bureau of the Ministry of Economic Affairs Printed by the Industrial and Consumer Cooperatives ^ ^ —— ^-(Please read the precautions on the back and then this page) Figure 6: It is a block diagram of the internal functions of the ghost signal time delay detector and ghost signal amplitude analyzer Figure 7: It is a schematic diagram of the internal functional block of the anti-ghost circuit. The components included in the diagram of this case are listed as follows: _______10 This paper is of appropriate size; 彳] Chinese solid label 埤 ((, milk) / \ 4 specifications (21 (^ 297 mm) 421 92 B, A7 — '_ B7 V. Description of the invention (e) Encoder 401 Quadrature amplitude modulation mapper 402 Frame appender 403 Orthogonal frequency division multiplexing Modulator 404 adder during protection 405 up-frequency device 406 down-frequency device 407 remover during protection 408 fast Fourier converter 409 demultiplexer 4 1 0 ghost signal delay detector 4Π ghost signal amplitude analysis 412 .Reverse ghost circuit 4 13 Remover during protection 4 1 4 Positive Frequency Division Multiplexing Demodulator 41 5 Frame Signal Splitter 416 Quadrature Amplitude Modulation Limiter 417 Decoder 418 Filter 4 U 1 String Number Detector 4 Π2 Calculator 4 11 3 One Signal Intensity Detector 41 2 1 First Adder 4122 Divider 4123 Variable Delay Element 4124 Second Signal Strength Detector 4125 Second Adder 4126 Adjustable Delay Element 4131 Adjustable Multiplier 4 1 3 2 Mixer 4 1 3 3 Description of the preferred embodiment (read the notes on the back and read this page again) Gutter The invention is basically based on the European multi-carrier digital modulation system (including guard interval, guide (Pilot Signal, channel coding, etc.) to improve the dynamic ghosting processing speed. The main working principle is at the receiving end, when the received signal is down-converted, it enters the fast The Fourier Transform (FFT) undergoes a ghost detection detection process before demodulation. The paper size is suitable for China National Standards (('NS) Λ4 specification (210X297 mm) 421 92 8 A7 B7. V. Invention &Quot; Sequence to remove ghosts caused by multipath interference in the channel and reduce the fading factor. Only the transmission signal and noise enter the fast Fourier transform (FFT) for demodulation and are decoded by the channel ( channel coding) to correct errors caused by noise. Please refer to the fourth figure, which is a functional block diagram of a device for encoding a orthogonal frequency division multiplexing system (COFDM) according to a preferred embodiment of the present case. The audio / video signal to be transmitted is transmitted by an encoder 401 and a quadrature amplitude modulation The QAM Mapper 402 process results in a QAM symbol signal Z [n], and the Z [n] signal is mixed into a pilot signal by a frame adapter 403 to obtain a Zp [n] signal, Zp [n] signal is then subjected to quadrature frequency division multiplexer 404 (OFDM Modulator) to carry out fast Fourier inverse transform (IFFT) to obtain zp [n + Nt] signal, and then The protection period adder 405 obtains a zg [n] signal after adding a guard interval. The zg [n] signal is transmitted after being converted by the up-conversion device 406, and due to multipath interference during transmission (Multipath Channel ) The mixing of effects and general noise results in an rm [n] signal. When the receiving end receives the rm [n] signal, the rm [n] signal is down-converted by the frequency reduction device 407 and the protection period remover 408 is obtained by removing the guard interval in the rm [n] signal. rp [n] signal, then rp [n] is processed by a fast Fourier converter 409 (FFT) to obtain Rp [n + Nt] symbol signal, and then Rp [n + Nt ] The symbol signal is separated into a pilot wave symbol signal P [n] (pilot sym (bol) and a data symbol signal Rd [n] (useful data symbol), where P [n] guides the wave symbol signal (pilot symbol ) After a ghost signal delay price detector 12 paper standard field Sichuan China national standard ((, yang) 6 4 specifications (210 乂 297 mm) read first read the precautions on the back and then #-, island page )-Installed.

'ST βτ Α7 Β7 Consumption cooperation between employees of the Central Bureau of the Ministry of Economic Affairs and the "Ink" 421 32 Β ^ V. Description of the invention (u) 411 (ghost delay detector) operation delay time to each ghost image η, r2, ..., &. In addition, the ghost signal amplitude analyzer 412 (ghost Amplitude Analyzer) calculates the ghost images based on the rm [n] signal output from the frequency reduction device 407 and the ghost signal delay detector 411 (ghost delay detector). The delay time lengths r2, ..., z; to analyze the ghost intensity amplitude coefficients%,%, ..., ', and the anti-ghost circuit 413 (de-ghost processor) measures the delay time length according to the pre-measured delay time 5 , Γ2, ..., and ghost amplitude intensity coefficient%, α2, ..., etc., to produce signals similar to the ghost delay time and amplitude and subtract the rra [n] signal output from the down-converting device 407 ', and further The ghost signal is removed, and the resulting signal is subjected to the guard interval remover 414 to remove the guard interval, and then is subjected to fast Fourier transform by the orthogonal frequency division multiplexing demodulator 415 (OFDM Demodulator). After the FFT, the pilot signal is separated by the frame demultiplexer 416, and then the QAM symbol slicer 417 and the decoder 418 are decoded. ) Is used to obtain A ghost-free signal of the noise. The following describes the mathematical derivation of the method of the preferred embodiment of the present case: Assume that the QAM symbol signal is expressed in the following way: (a) Zn [η] = χ [η] + ϊΥ [η] ZZ [η]: QAM symbol 蟫 signal X [n]: QAM real part code signal Y [n]: QAM imaginary code signal 13 Chinese paper standard (('NS) Λ4 specification (210X297 mm) -9) Note for buying this book again]

421 92 8 .Guang A7 B7 V. Explanation of the invention (/ 3) The solution of the Ministry of Economic Affairs # ΐν- ^ 0ϊ, eliminating the print of the cooperative I (b) After adding the pilot signal, we get Zρ [η] = Χρ [η] + / Υρ [η] η = 16m +1 K / 幺 15 where represents the symbol number /: represents the symbol position (c) After fast inverse Fourier transform (IFFT) conversion, 'Zp [ n + Nt] = ΠΤΤ {ZΡ [η + Nt]} = i Σ ZP [k + Nt] x 〆 where N: FFT conversion length W = e ~ J2plN (d) After adding the guard interval, we get ( Assume guard interval / useful symbol duration = l / 8) ^ g [n] = zp [mN + / -1024] sn = mT + /, 1024 < T 0, n = m + / 5 0 < T < 1024, meZ, T = 9216 (e) After multipath interference (Multipath Channel), zm [n] = zg [n] + a zg [nr] where (X is the ghost amplitude intensity coefficient τ is the ghost delay time After adding the length to a general noise, we get rm [n] = zm [n] + N [n], N [n] =-general noise. 14 The paper standard is applicable to the Chinese National Standard (C'NS) Λ4 specification. (2! 0X297) 漦 (谙 Please read the notes on the back then this page)-Binding 421 92 8 Γ A7 B7 V. Description of the invention (/ thousands) (^ ) The drp [n] signal is obtained after removing the guard interval part at the receiving end, and rp [n] = rm [mT + / + 1024] 0 < / < N (g) rpM After FFT, get R [n + Nt] = Σ rp [k + Nt] Wnk k = 0

In

Where w = e 'teZ (h) after demultiplexing the signal, the symbol signal is separated into a pilot wave symbol signal (pilot symbol) and a data symbol signal (useful data symbol), Rp [n] = P [ nI + Ri > [n] η = 16m + / m eZ / eZ where P [n] is the pilot wave symbol signal RD [n] is the data symbol signal P [n] = Rp [16m + /] |; me Z π = ο RD [n] = Rp [16m + /] m € Z, 1 < / < 15 谙 Read the back item and r Binding on this page Nl, 16mk PN = Rp [16m + /]; = 〇 = 2 Rp [k] xw -k = 0 Nl = Σ [ζπ, Μ + ΝΜ ^ = Σ {zg [kl + «zg [k-r] + N [k]} w v16mk 16mk k-0 = Zp [16m ] + «W16mr x Zp [16m] + N [16k] (Let k '= kr, k = k' + r) Because the form of the guide signal in the preferred embodiment of the present invention is 15 This paper size is applicable to China Xibei ((: NS) Λ4 specification (210X297) 漦 4 2 1 92 ^ 3 J ^ A7 B7 V. Description of the invention (printed by the quasi bureau of the π feM department and printed by Hezhu Society 'Adopting propulsion power Leading signal (boosted power pilot), ie Zp [n] = A + j〇Ak code amplitude absolute value P [n] = Z [16m] + aw16mrZp [16m] + Noise = (A + jO) + ^ (cos32 ^ 117 + ysm3 ^ lr) (A + jO ) + Noise = (A + jO) + oA (cos — + 7'sin--mr) + Noise NNA (l + ctcos ^^^) + jaAsm ^^ mT + Noise NN _ take the imaginary part and use low pass The noise remover can get a ^ τ, J. 4 i32 ^ 2ni ^ sine wave 'oAsm--, and the delay length τ can be easily calculated by converting this sine wave into a square wave. Ghost image is more obvious, and there are few more than two ghost images with strong intensity. If there are two obvious ghost images, the real and imaginary parts can be used to filter out different delay lengths respectively. If there are more than two ghosts, ZnJnpZglnl + c ^ Zgfn- rJ + ^ Zgfn- r2] + a3Zg [n- r3] + a4zg [n- r4] + a5zg [n- r5] where ·, α2, a3 , Cr4, a ;: is the ghost amplitude intensity, and h,, ri, Q is the ghost delay length. 'After the fault end undergoes f FT conversion, it generates 32 ^ 1X1 ^, Ν 32τπηΐ ~? 32 ^ mT ~ 3 32mnr4 32τππτ5 Carriers of different frequencies such as N, N, N, N '. Therefore, band. Pass filter banks in different frequency bands can be applied to detect ghosts in different frequency bands. 16 This paper is a Chinese national standard soap (rNS) Λ4 size (210X297 mm) f. (Please read the precautions on the back of the paper first, then ^ this page)

A7 B7 Q ':: V. Description of the invention (, 0 The preferred embodiment of this case uses a boosted power pilot signal with 1/16 channel capacity or +1/8 channel capacity Therefore, the transmission capacity of the system is further improved. As the boosted power pilot is accumulated by the fast Fourier inverse transform (IFFT), the amplitude of the pilot signal in the time domain increases. Dozens of times as shown in the fifth figure, 'the signal is much larger than the normal signal, so the ghost system caused by multipath in the time domain is particularly obvious. Due to the characteristics of the above phenomenon, the preferred embodiment of the present invention uses ghosts Ghost delay detector 41 l (ghost delay detector) and ghost signal amplitude analyzer 412 (ghost Amplitude Analyzer) to accurately measure the length and size of ghost delay, and provide the above two parameters to counter ghost Circuit 4i3 (de-ghost processor) to overcome the fading phenomenon caused by multipath interference. The principle of multipath interference (ghosting) correction is delayed in the time domain and converted to the frequency domain, which is derived from mathematical analysis. The leading signal wave plus a sine wave signal is expressed by the following formula: where: must = 〆 'N is the FFT conversion length center [«]: the receiving end guiding signal ZJn]: the original guiding signal%, α2, α3: (ghost image) Signal size rpr2, r3: (ghost shadow) signal delay length 17 This paper size applies to Chinese national standard (('NS) Λ4 specifications (2) 0X 297 mm) u---* ut ^ in ·-I-- --I 1-Business (Please read the precautions on the back before this page)

A line '421 92 8 A7 _ B7 V. Description of the invention (\ 7) The ghost signal delay detector 414 uses a sine wave to have a linear relationship with the delay length. See the first table below, which is a computer The relationship between the number of simulated sine waves and the delay length. The following relationship can be obtained from Table 1: Number of sine waves = (delay length) X (number of FFT conversions) Table 1 N = 8I92 (8K / FFT) run 20,000 samples Relationship between delay length and additional carrier frequency \ — / · " -... (read the note on the back before reading t '· this page)' Installation_ The Ministry of Economic Affairs and the Bureau of Standards and Standards Bureau of the Shellfish Consumption Report of the Printing Company f Guide signal number / information ratio 1 8 1 16 FFT Number of conversions 3 3 Protection period = 1 1 1 1 Δ _ Δ 4 (Δ 8 (Δ 4 (Δ 8 (Δ Tv " 8192T -2048T > = 1024T) = 2048T) = 1024T) Z = -25 75 75 75 75 Ghost extension Z = -50 150 150 150 150 Delay length Z = -75 225 225 225 225 (Ghost Z = -100 300 300 300 300 Intensity (XZ = -125 375 375 375 375 375 = 0.5012 (-Z =- 150 450 450 450 450 3dB) Z = -175 525 525 52 5 525 Z = -200 600 600 600 600, n line _ 18 (('Guilty') / \ 4 size (210 > < 297 mm) d21 92 8 .4 A7 ______B7 V. Description of the Invention (/ 5) According to the above formula, we can conveniently calculate the number of sine waves and then push the delay length. Please refer to the figure 6 below, 'It is a ghost signal delay detector. 411. Within the ghost signal amplitude analyzer 412 A functional block diagram, in which the ghost signal delay detector 411 is composed of a filter 4111, a string number detector 4112, and a calculator 4113. Due to the time-delayed ghost signal in the time domain, Conversion to the frequency domain will become another additional carrier signal ', and the frequency of this carrier signal is proportional to the delay time of the ghost signal, so the filter 4111 is used to take out the additional carrier signal caused by the ghost signal, and then use the string The wave number detector 4112 measures the number of sine waves that make up the additional carrier signal, and then calculates it using the calculator 4113 to accurately determine the delay time. In addition, to eliminate the interference of ghosts, in addition to knowing the delay length It is also necessary to know the intensity of the ghost image. The intensity of the ghost image can be determined according to the delay time provided by the ghost signal delay detector 411, and the ghost amplitude intensity coefficient can be measured. Add the ghost size with the same delay length and divide it by the sum of the corresponding guide waves. The following formula shows: Σ ghost size with the same delay length Web strength coefficient = - --- _ [Sigma a corresponding wave guide of size > where i represents the number of pairs of the guide and the ghost wave is calculated. The number of pairs to take depends on the ghosting's character. 'If it is a dynamic ghosting, like action _19 ((' milk) 8 4 specifications (210 乂 297 public 漦) ---------- ^ -/ J. (#Read the precautions on the back before ^ -¾. This page) Order 421 92 8 A7 B7 Printed by the Ministry of Economic Affairs, the Ministry of Work and Labor, Cooperative, Co., Ltd. 5. Description of the invention (/ 7) The receiving time is short and the ghost image is strong. You can choose fewer pairs (that is, i is smaller) to quickly determine the delay and size of the ghost image. Quick correction; if it is the static ghost image of the general TV user, the delay is longer and the ghost image is weak. You can choose more pairs (that is, i is larger) to accurately calculate the ghost size. Please refer to Figure 6 again, where the ghost signal amplitude analyzer 412 uses the above concept to detect and analyze the ghost amplitude intensity coefficient α. 'It consists of a first signal intensity detector 4 1 2 1, a first adder 4122, a divider 4123, a variable delay element 4124, a first k-number intensity detector 4 12 5, and a second adder 4 12 6. Because the pilot signal is accumulated by the fast inverse Fourier transform (IFFT) conversion performed by the orthogonal frequency division multiplexer 404, As shown in the fifth figure, the amplitude of the time domain (time domain) is increased by dozens of times, which is much larger than the normal signal. Therefore, the ghost caused by multipath in the time domain is particularly obvious. Therefore, the first signal strength detection The detector 4121 is used to detect the intensity of a plurality of pilot signals in the rm [η] signal output from the down-converting device 407 and accumulate with the first adder 4122 to obtain a first accumulation. And the variable delay element 4124 determines the ghost position according to the delay time of the ghost signal caused by the pilot signal provided by the ghost signal delay detector 411, and then controls the The second signal intensity detector 4125 measures the intensity of the ghost image, and then uses the second adder 4126 to accumulate the intensity of the corresponding ghost signals with the same delay length to obtain a second accumulated value. The divider 4123 is used. Divide the second accumulated value and the first accumulated value to obtain a ghost amplitude intensity coefficient α to provide a basis for correcting the ghost circuit 413 (de- ghost processor). 20 State China House mark net. (C'NS) Λ4 specification (2) 〇297297 (Please read the precautions on the back first and then this page) Binding. Ordering: V. Description of invention (A7 B7 Ghost delay time length and ghost amplitude intensity \ coefficient ^ information, using adjustable delay elements and multipliers and other anti-ghost circuit 4 1 3 completed by the element to produce ghost delay time length and amplitude similar to the following Signal: aAe ^ + (oA) 2e -2τΤ r: ghost delay length α: ghost size ifi, ministry standard consumer cooperative

Then the mixer device is subtracted from the original signal A + ααβ · τΤ to obtain a signal A-(oA) 2e-2TT which removes ghost images. This can complete the effect of removing ghost images. Please refer to the seventh figure for more details. It is a detailed functional block diagram of the anti-ghost circuit 4 13. It is completed by an adjustable delay element 4131, an adjustable multiplier 4132, and a mixer 4133. The delay element 4131 is based on the detected delay time length, r2, ..., · Γη, and the adjustable multiplier 4132 uses the calculated ghost amplitude intensity coefficients%,, ...,% and other information to use mixed waves The generator 4133 produces a signal similar to each ghost delay time length and amplitude and subtracts the rm [n] signal output from the frequency reduction device 407, thereby removing the ghost phenomenon. Therefore, the COFDM system using the preferred embodiment of the present case is connected to a faulty end. After the frequency of the received signal is down-converted and noise is filtered, the ghost detection countermeasure circuit in the preferred embodiment of the present case is first removed to remove ghosts that are not heard by the receiving end And then remove the guard interval by the protection period remover 414, and then the orthogonal frequency division multiplexing demodulator 415 (OFDM 21 This paper scale is suitable for China ’s national standard ((, NS ) 8 4 specifications (2! 〇χ297 公 t) (阅读 Read the precautions on the back before > this page).

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• Marry, J A7 B7 V. Description of the invention (^ /

Demodulator) to perform a fast Fourier transform (FFT) to convert to a frequency domain signal. '4 The pilot signal (pilot signa 丨) is separated by the frame signal demultiplexer 416 (Frame demultiplexer), and then the orthogonal amplitude modulation symbol is applied. The limiter 417 (QAM symbol slicer) obtains the real transmitted digital symbol code number k, and then after decoding the channel of the decoder 418 (decoder), a ghost-removed sound and general noise can be obtained. / Video signal. To sum up, in this case, the down-frequency signal is first subjected to the ghost removal processing step ', and the ghost delay length is the same as the ghost length in the channel, and the size is also the same. After this processing, only the real signal and generally random white noise remain. Due to orthogonal multi-carrier conversion and spread-spectrum effect, the errors of noise interference can be dispersed, and then channel coding (for example: conv〇lu (i0I1 code, TCM code, RS code) with interleaving) Technology, you can correct the error code 'greatly improves the communication quality of the transmission D. Therefore, the present invention can improve the shortcomings of the conventional technology, and update the channel state correction after each fast Fourier transform (FFT). Generate false transmissions and propose fast and accurate equalization techniques for dynamic ghosting and action reception. Quickly and accurately determine and eliminate ghosting locations, and thoroughly improve the lack of the asymptotic convergence method of the known least mean square algorithm (LMS). This case can still be applied to the current Digital Audio Broadcasting (DAB) system, or the European Digital Video Broadcasting (DVB-T) system or the twisted-pair multi-carrier ADSL / XDSL Multi- In the Tone transmission system and other systems, the 22 standard and paper size are applicable to Chinese storehouse standard (('NS) Λ4 specifications (2) 0 × 297 feet) (Please read the back first Note the re-entry path Page ^) - mounted - 42 ί 92 8 Α7 Β7 V. invention is described in (W) is made of the case of any person familiar with the art of the present application to all sorts of modifications and Carpenter thinking,

I, of course, are not inferior to those who want to protect the scope of patent application. ------ ^ --------- II ------ ^ (谙 Please read the notes on the back before filling in this page) Consumer cooperation. It-printed paper size applicable to the Chinese National Standard (CNS) Λ4 specification (2) 0297 mm

Claims (1)

Printed by the Consumer Cooperative of the Central Bureau of the Ministry of Economic Affairs, Consumer Cooperative Scope of Patent Application 1. A method to overcome multipath interference, which is applied to a multi-carrier digital modulation-demodulation system using one of the pilot signal technologies. The transmitted data is transmitted after the multi-carrier digital modulation procedure. The method for overcoming multipath interference includes the following steps: (a) receiving an interference signal formed by the effect of multipath interference; (b) receiving the interference The signal is processed and separated into a disturbed guide signal and a transmitted signal to be transmitted by the interfered station through a first operation program. (C) The disturbed guide signal includes a guide ghost signal caused by multipath interference. The second operation program is used to calculate a ratio between the sine wave frequency of the pilot ghost signal and the carrier frequency of the pilot signal to obtain a delay time length; (d) using the delay time length to determine the?丨 After measuring the amplitude of the guiding ghost signal after the position of the guiding ghost signal, divide it by the amplitude of the corresponding guiding signal to obtain a ghost amplitude intensity coefficient; (e) According to the length of the delay time and the An anti-ghost signal is generated after the ghost amplitude intensity coefficient is mixed into the interfered signal to eliminate the ghost signal caused by multi-path interference, so as to obtain a multi-carrier lift that has overcome multi-path interference. Signal; and • r-(f) demodulate the multi-carrier digitally modulated signal that has overcome the multi-path interference, to get back the material to be transmitted. 2. As described in item 1 of the scope of the patent application, the method for overcoming multi-path interference, 24 paper standard universal China National Winter Ladder Standard (CNS) A4 specification (21〇297297): ™-(please first (Notes on the back of this article are read again on this page) Thread: € 21 VI. Patent application scope A8 B8 C8 D8 The Central Standards Bureau of the Ministry of Economic Affairs and Consumer Cooperatives printed the multi-carrier digital modulation that it uses for pilot signal technology The _demodulation method is an encoding orthogonal frequency division multiplexing modulation using one of a pilot signal and a guard period technique. 3. The method for overcoming multipath interference as described in item 2 of the scope of the patent application, wherein the first operation procedure includes the following steps: (b 1) After removing the interference signal from its protection period, a fast Fourier transform is performed. Conversion for obtaining an interfered symbol signal, and (b2) demultiplexing the interfered symbol signal into the interfered pilot signal and the interfered data signal in a demultiplexed manner. 4. The method for overcoming multipath interference as described in item 3 of the scope of patent application, wherein the second operation program is: a value obtained by dividing a carrier frequency by a sine wave frequency of the ghost signal as the ghost image The delay time of the signal. 5. —A device for overcoming multipath interference, which is applied to the receiving end of a multi-carrier digital modulation-demodulation system using one of the pilot signal technologies. The receiving end is used to receive the multipath interference A disturbed signal and its processing are separated into a disturbed pilot signal; and—the disturbed multipath interference device includes: a ghost signal delay detector electrically connected to the multi-carrier digital modulation -The receiving end of the demodulation system, which is used to calculate a ratio between the sine wave frequency of a pilot ghost signal and the carrier frequency of the pilot signal contained in the interfered pilot signal to obtain a delay Length of time; a ghost signal amplitude analyzer, electrically connected to the multi-carrier digital tone 25 1 paper size applicable to Yin Huo national standard (0 Yang) into 4 specifications (210 parent 297 mm) (Please read the note on the back first $ 项 再 t ^ '页) Equipment · -Order βτ Dance · D8 D8 The Ministry of Economic Affairs Central Standardization Bureau employee consumer cooperative printed 7T, applied for patent consumption change-demodulation curve. The system receiver and the ghost signal delayed detection A device for analyzing a ghost image amplitude intensity coefficient according to the perturbed signal and the delay time length; and a ghost image counter circuit electrically connected to the bird image signal amplitude analyzer, the ghost The shadow signal delay detector and the multi-carrier digital modulation resolution system discriminate the receiving end. Based on the delay time length and the ghost amplitude intensity coefficient, a ghost signal delay time length and amplitude is created. Signal, and subtracting the signal from the interfered signal to obtain a multi-carrier digitally modulated signal that has overcome multi-path interference. 6. The device for overcoming multipath interference as described in item 5 of the scope of patent application, wherein the ghost signal delay detector comprises: a filter 'electrically connected to the reception of the multi-carrier digital modulation-demodulation system Terminal, which is used to take out the guide ghost signal included in the interfered guide signal; a string number detector 'is electrically connected to the filter, which is used to extract the components of the guide ghost signal. Measure the number of sine waves; and-calculator, electrically connected to the sine wave number detector wave digital modulation _ the receiving end of the demodulation system 'It is based on the following relationship ... · number of sine waves = delay time length X The number of fast Fourier transforms to find the delay time. — 7, The device for overcoming multipath interference as described in item 6 of the scope of patent application, wherein the ghost signal amplitude analyzer includes: _26 This paper size is applicable to China National Broadcasting Standard (CNS) Α4 specification (210 × 29? Mm) ( Please read the precautions on the reverse side before ^ f this page). Binding. 4242 彳 92 8 A8 B8 C8 D8 VI. Application for Patent Scope The Central Consumers Bureau of the Ministry of Economic Affairs has printed a first signal strength detector. Connection, the receiving end of the multi-carrier digital modulation-demodulation system is used to extract and measure the strength of the plurality of pilot signals in the interfered signal; a first adder is electrically connected to the first- Signal strength detector, which is used to accumulate the strengths of the pilot signals detected by the first signal strength detector to obtain a first accumulated value; u a variable delay element, electrically connected At the receiving end of the calculator and the multi-carrier digital modulation-demodulation system, it is used to determine the location of the interfered signal t and the pilot ghost signal according to the delay time; a second signal strength detection Tester's electrical connection At the variable delay element, it is used to measure the intensity of the guiding ghost signal at the determined position; a second adder is electrically connected to the second signal intensity detector, which is used to Accumulating the guided ghost signal strength measured by the second signal strength detector to obtain a second accumulated value; and a divider 'electrically connected to the first adder and the second adder, It is used to divide the second accumulated value and the first accumulated value to obtain the ghost amplitude intensity coefficient. 8. The device for overcoming multipath interference as described in item 7 of the scope of patent application, wherein the anti-ghost circuit comprises:. An adjustable delay element electrically connected to the calculator and the multi-carrier digital modulation solution. · Tuning and changing system connection ... It is used to adjust the length of this paper to 27. This paper size applies the Chinese National Standard (CNS) A4 specification (210X29 * 7mm) (Please read the precautions on the back before reading) (t page)-Installation ·-Threading A8 B8 C8 D8 42 · 1 92 8 h 6. The scope of the patent application produces a signal similar to the delay time of a ghost signal; an adjustable multiplier electrically connected to the divider And the adjustable delay element, which is used to delay the signal similar to the ghost signal for a length of time, and then produces a ghost-like signal amplitude $ the signal according to the ghost vibration amplitude factor; and a mixer 'Zero' is connected to the adjustable multiplier and the receiving end of the multi-carrier digital modulation and demodulation system, which subtracts the signal from the interfered signal to obtain a multi-carrier digital tone that has overcome multi-path interference. Output after changing signal. ---------- ；-Install I. (Please read the note on the back of the page before t page, tT Printed by the Central Ministry of Economic Affairs and the Consumers ’Cooperatives 28 Private paper standards are applicable to China Kneading standard (CNS) A4 size (210X297 mm)