41results about How to "Obvious peak" patented technology

A physical frame preamble symbol receiving and processing method comprises the steps as follows: processing a received digital signal to obtain a baseband signal; judging whether there is a preamble symbol expecting to receive in the baseband signal, wherein the preamble symbol expecting to receive is a time-domain structure with a time-domain OFDM symbol as the main body and with a cyclic prefix in the front part and a modulation signal in the back part; and determining the position of the preamble symbol in a physical frame and parsing out signaling information carried in the preamble signal if there is a preamble symbol expecting to receive in the baseband signal. According to the technical scheme, the problem that a preamble symbol may fail to be detected by a low-complexity receiving algorithm under a complex frequency-selective fading channel under the condition of the current DVB_T2 standard or other standards is solved.

The invention discloses a generating method of a preamble symbol in a physical frame, comprising the following steps: carrying out discrete Fourier inverse transform on a frequency-domain OFDM symbol of a predetermined length to obtain a time-domain OFDM symbol; intercepting a time-domain OFDM symbol of the cyclic prefix length from the time-domain OFDM symbol as a cyclic prefix; generating a modulation signal based on the intercepted time-domain OFDM symbol of the cyclic prefix length; and generating a preamble symbol based on the cyclic prefix, the time-domain OFDM symbol and the modulation signal. By adopting the technical scheme, the problem in the current DVB_T2 standard and other standards that a DVB_T2 time-domain structure has no cyclic prefix and is not applicable to coherent detection and detection of a preamble symbol by using a low-complexity receiving algorithm under a complex frequency-selective fading channel may fail is solved.

The invention discloses a generation method for preamble symbols in a physical frame. The generation method comprises the steps of: carrying out inverse discrete Fourier transform on a frequency domain OFDM symbol with a preset length to obtain a time domain OFDM symbol; determining a cyclic prefix length; intercepting a time domain OFDM symbol with the cyclic prefix length from the time domain OFDM symbol to serve as a cyclic prefix; generating a modulation signal based on the intercepted time domain OFDM symbol with the cyclic prefix length; and generating a preamble symbol based on the cyclic prefix, the time domain OFDM symbol and the modulation signal. The technical scheme provided by the invention solves the problems of the current DVB_T2 standard and other standards that a DVB_T2 time domain structure has no cyclic prefix and is not suitable for coherent detection, and the failure probability of the preamble symbol detected by adopting a low complexity receiving algorithm in a complex frequency selectivity fading channel is high.

The invention discloses a generation method of frequency-domain OFDM symbols and a generation method of preamble symbols in physical frames. The generation method of the frequency-domain OFDM symbols includes the following steps that: the average power ratio of a fixed sequence and a signaling sequence is determined; fixed sequences and a signaling sequence set are respectively generated in the frequency domain according to the average power ratio R; one signaling sequence is selected from the signaling sequence set, and the fixed sequences and the signaling sequences fill effective sub carriers, odd-even staggered arrangement exists between the fixed sequences and the signaling sequences; two sides of the effective sub carriers are filled with zero-sequence sub carriers respectively to form a frequency domain OFDM symbol with a preset length; and the serial number of the selected signaling sequence in the set is the signaling information carried by OFDM symbols. With the generation methods provided by the technical scheme of the invention adopted, the problem of failure probability in low-complexity receiving algorithm detection on preamble symbols in a frequency selective fading channel in the current DVB_T2 standard and other standards can be solved.

The invention discloses a method for generating a precursor symbol in a physical frame. The method comprises the following steps of: performing discrete Fourier inversion of a frequency-domain OFDM symbol with a preset length to obtain a time-domain OFDM symbol; determining a circulation prefix length; intercepting a partial time-domain OFDM symbol with the circulation prefix length from the rear part of the time-domain OFDM symbol, and taking the partial the time-domain OFDM symbol as a circulation prefix; generating a modulating signal according to the partial time-domain OFDM symbol; and generating the precursor symbol based on the circulation prefix, the time-domain OFDM symbol, and the modulating signal. According to the technical scheme of the invention, the problem of decrease of frequency-domain channel estimated performance is solved, and the modulating signal is generated by utilizing the partial time-domain OFDM symbol, so that the generated precursor symbol has small frequency offset and excellent timing synchronism. Furthermore, processing of a received signal by a receiving terminal is guaranteed, with carrier frequency deviation being in a range from -500 kHz to 500 kHz.

The invention discloses a frequency domain OFDM (orthogonal frequency division multiplexing) symbol generation method and a preamble symbol generation method. The frequency domain OFDM symbol generation method comprises the steps of generating a fixed sequence and a signalling sequence in the frequency domain, wherein the fixed sequence and the signalling sequence are constant modulus sequences, and complex numbers in the fixed sequence and the signalling sequence are equal in modulus; filling the fixed sequence and the signalling sequence to an effective sub-carrier, wherein the fixed sequence and the signalling sequence are in odd-even alternative arrangement; and filling zero-sequence sub-carriers at two sides of the effective sub-carrier respectively so as to form a frequency domain OFDM symbol with predetermined length. The technical scheme disclosed by the invention avoids a characteristic that the generated signalling sequence has cyclic shift or cyclic shaft and phase shift in the time domain, and solves a problem of frequency domain channel estimation performance reduction. Furthermore, a receiving terminal is ensured to still be able to process received signals with the carrier frequency deviation being in a range of -500kHz and 500kHz.

The invention discloses a method for generating a preamble symbol and a method for generating a frequency domain OFDM symbol. The method for generating the frequency domain OFDM symbol comprises the following steps: respectively generating a fixed sequence and a signaling sequence on a frequency domain; filling an effective subcarrier with the fixed sequence and the signaling sequence, wherein the fixed sequence and the signaling sequence are in odd-even staggered arrangement; and respectively filling the two sides of the effective subcarrier with a zero sequence subcarrier so as to form the frequency domain OFDM symbol with a predetermined length. According to the technical scheme provided by the invention, the problem of failure probability of the preamble symbol in low-complexity receiving algorithm detection in case of a frequency selective fading channel in a conventional DVB_T2 standard or other standards is solved.

The invention discloses a frequency domain OFDM symbol generation method and a preamble symbol generation method. The frequency domain OFDM symbol generation method comprises the steps of: generating fixed sequences and signaling sequences in a frequency domain respectively; filling the fixed sequences and the signaling sequences which are arranged in an odd even interleaving manner to an effective subcarrier; and filling zero-sequence subcarriers on both sides of the effective subcarrier to form a frequency domain OFDM symbol with a preset length. According to the technical scheme provided by the invention, the frequency domain OFDM symbol generation method and preamble symbol generation method prevent the generated signaling sequences from having a property of circular shift or circular shift plus phase shift in a time domain, solves the degradation problem of channel estimation performance of the frequency domain, and further ensures that a receiving end can process and receive signals when carrier frequency deviation ranges from -500kHz to 500kHz.

The invention relates to an OFDM (Orthogonal Frequency Division Multiplexing) time synchronization algorithm based on a conjugate symmetric sequence. The OFDM time synchronization algorithm comprises the steps of constructing a sequence with conjugate symmetry; carrying out symmetric related calculation at a receiving end by using the conjugate symmetry of the sequence so as to obtain a related peak value of a timing measurement function; and determining a beginning position of an OFDM signal by using the position of the related peak value so as to finish time synchronization. By using the invention, the adverse effect on the time synchronization, caused by a cyclic prefix and the conjugate symmetry of the sequence, is overcome, and higher timing accuracy is obtained; and the OFDM time synchronization algorithm based on the conjugate symmetric sequence, provided by the invention, can be effectively used for the time synchronization of the OFDM system under a multipath channel.

The invention provides a new method for OFDM time synchronization, which is based on a training sequence structure and a corresponding synchronization algorithm. A method of superimposing the OFDM synchronization training sequence to cyclic prefixes of transmission data is used for saving extra transmission cost; relevant peak value is more prominent by combing the training sequence structure and utilizing positive and negative alternating characteristic of the training sequence. Both the synchronization accuracy and the operating speed of the algorithm are increased by combining the corresponding synchronization algorithm.

The invention relates to a method for preparing a Cu-based two-dimensional sheet MOFs material. The method comprises the following steps: adding Cu(NO3)2.3H2O to DMF, performing stirring to dissolve the Cu(NO3)2.3H2O, adding 2-aminoterephthalic acid, and standing the obtained solution at 110-130 DEG C for 22-26 h; cooling and centrifuging the obtained solution, adding the DMF to the obtained precipitate, and washing the obtained precipitate; and carrying out solvent replacement, immersing the obtained precipitate in ethanol, performing centrifuging, and drying the obtained precipitate to obtain the Cu-based two-dimensional sheet MOFs material. The preparation method has the advantages of simplicity, short production cycle, no influences brought by a surfactant, and no influences on the specific surface area of the sheet MOFs material, and the Cu-based two-dimensional sheet MOFs material has an increased contact area with a reactant, and has great potential in the field of catalysis.

A calibration system for RDSS (Radio Determination Satellite Service) channel zero value comprises a spread spectrum signal source, a microwave signal source, a frequency converter, a power divider, a double-channel digital oscilloscope, a first attenuator, a second attenuator, a control and processing computer and a vector network analysis instrument, wherein the spread spectrum signal source generates simulated RDSS spread spectrum signals; spread spectrum signal source outcoming signals are subjected to frequency conversion by the microwave signal source and the frequency converter so as to generate frequency points suitable for RDSS service channel input; a high-sampling rate digital oscilloscope is used for synchronously sampling the input / output signals of the RDSS service channel; and the control and processing computer is used for completing initialization of the oscilloscope, acquisition and loading of the oscilloscope channel data, orthogonalization of the channel data, carrier rotation, circulating autocorrelation, peak value searching, and zero value calculation and processing, so as to eventually obtain the absolute time delay of the RDSS service channel. According to the system provided by the invention, the signals consistent with the RDSS service system are adopted to serve as the reference, the calibration zero value can reflect the real conditions and the calibration precision is high.

An autofocus method for multi-object digital holographic measurement relates to the technical field of digital holographic measurement and solves the problem in the prior art that a focus curve obtained by a criterion function has a low peak value and is difficult to distinguish due to the influence of system and environmental noise. The method includes a first step of acquiring a hologram; a second step of separating the hologram; a third step of setting an automatic focus search range and reconstructing an image; a step four of obtaining an autofocus curve; a step five of drawing the Ci curves obtained by all holographic subgraphs in a unified coordinate system by using the set autofocus search range as a abscissa and using the Ci values as an ordinate; and a step 6 of reconstructing theoriginal hologram based on the specific reproduction distance of multiple objects obtained in the step 5, and putting all reconstructed images in a unified spatial coordinate system to obtain a spatial distribution state of the multiple objects. The method obtains an obvious peak at the focus by subjecting the autofocus criterion function to exponential transformation, and reduces the peak discrimination difficulty.

The invention discloses a preamble symbol generation method in a physical frame and a frequency domain OFDM symbol generation method. The preamble symbol generation method in the physical frame comprises steps: fixed sequences and signaling sequences are generated respectively in the frequency domain; the fixed sequences and the signaling sequences fill effective sub carriers, and odd-even staggered arrangement exists between the fixed sequences and the signaling sequences; two sides of the effective sub carriers are filled with zero-sequence sub carriers respectively to form a frequency domain OFDM symbol with a preset length; discrete Fourier inverse transform is carried out on the frequency domain OFDM symbol to obtain a time domain OFDM symbol; a modulation signal of the time domain OFDM symbol is generated, and on the basis of the time domain OFDM symbol and the modulation signal, a preamble symbol is generated. The technical scheme of the invention solves the problem that in the current DVB_T2 standard and other standards, failure probability happens in the case of low-complexity receiving algorithm detection on the preamble symbol in a frequency selective fading channel.

The invention discloses a generation method of a preamble symbol and a generation method of a frequency-domain OFDM symbol. The generation method of the preamble symbol in a physical frame comprises that a fixed sequence and a signaling sequence are generated in the frequency domain; the fixed sequence and the signaling sequence are filled to an effective subcarrier, and the fixed sequence and the signaling sequence are in odd / even or even / odd staggered arrangement; zero-sequence subcarriers are filled to the two sides of the effective subcarrier to form a frequency-domain OFDM symbol in a predetermined length; inverse discrete Fourier transform is carried out on the frequency-domain OFDM symbol to obtain a time-frequency OFDM symbol; a modulation signal of the time-frequency OFDM symbol is generated; and the preamble symbol is generated on the basis of the time-frequency OFDM symbol and the modulation signal. According to technical schemes of the invention, the problem that the preamble symbol may cause detection failure via a low-complexity reception algorithm in a frequency selective attenuation channel in present DVB_2 and other standards is solved.

The invention belongs to the technical field of wireless digital communication, and particularly relates to a coarse synchronization method for restraining the multipath time delay and the Doppler effect in the LTE-FDD system. Coarse synchronization detection is carried out by utilizing a cyclic prefix of an OFDM symbol in a time slot, and the method comprises the steps of signal storage, correlation energy calculation, signal energy calculation, threshold value judgment, starting point judgment, decimal-times carrier frequency offset judgment and the like. A computer conducts simulation display, and the method has the excellent synchronization performance and is suitable for a high-speed mobile wireless communication system. Compared with a traditional correlation detection method, the method has the advantages that the accuracy of decimal-times carrier frequency offset detection can be improved by 10%, and the accuracy of frame starting point detection can be improved by 80%.

The invention discloses a generation method for a preamble symbol in a physical frame. The generation method comprises that a time-domain OFDM symbol is obtained; the length of a cyclic prefix is determined; a time-domain OFDM symbol in the cyclic-prefix length is cut from the time-domain OFDM symbol and serves as the cyclic prefix; a modulation signal is generated according to the cut time-domain OFDM symbol in the cyclic-prefix length; and the preamble symbol is generated on the basis of the cyclic prefix, the time-domain OFDM symbol and the modulation signal. On the premise that the length of the modulation signal is determined, different initial positions are selected from the part, used for cutting the cyclic prefix, of the time-domain OFDM symbol to transmit signaling information on the basis of the length of the modulation signal. The generation method of the invention can be used to solve the problems that a DVB_T2 time-domain structure in DVB_T2 and other standards at present cannot adapt to coherent detection due to lack of a cyclic prefix, and that detection via a low-complexity reception algorithm may cause failure when the preamble symbol is in a complex frequency selective fading channel.

The invention discloses a generation method for a preamble in a physical frame. The method comprises the following steps: inverse discrete Fourier transform of a frequency-domain OFDM symbol with a preset length is carried out to obtain a time-domain OFDM symbol; different combinations of a cyclic prefix length and a modulation signal length are selected, so that a finally generated preamble can transmit signaling information through the different combinations; a time-domain OFDM symbol with the cyclic prefix length is intercepted from the time-domain OFDM symbol to be used as a cyclic prefix; a modulation signal is generated based on the intercepted time-domain OFDM symbol with the cyclic prefix length; and the preamble is generated based on the cyclic prefix, the time-domain OFDM symbol, and the modulation signal. Through the method, the problems in the conventional DVB_T2 and other standards that a time-domain structure is not applicable for coherent detection because of the absence of the cyclic prefix and that the preamble has a failure probability for detecting a low-complexity reception algorithm under a complex frequency-selective fading channel are solved.

The invention discloses a method for generating a frequency domain OFDM symbol. The method is characterized by further comprising the following steps before discrete Fourier transform is performed on the frequency domain OFDM symbol with a predetermined length to obtain a time domain OFDM symbol: determining an average power ratio of a fixed sequence to a signaling sequence; separately generating the fixed sequence and the signaling sequence on the frequency domain according to the average power ratio; filling the fixed sequence and the signaling sequence on an effective subcarrier, wherein the fixed sequence and the signaling sequence are arranged in an odd-even stagger manner; and respectively filling zero sequence subcarriers on both sides of the effective subcarrier to form the frequency domain OFDM symbol with the predetermined length. The problem that a failure probability is detected by a low- complexity receiving algorithm of a pilot symbol in a frequency selective fading channel in the existing DVB_T2 standard is solved.

A method for synchronizing OFDM symbols, comprising: generating local frequency domain data, the local frequency domain data includes a plurality of pilot data, and the positions of the selected plurality of pilot data in the frequency domain are non-equal intervals; Perform inverse Fourier transform on the local frequency domain data to obtain local time domain data; add a cyclic prefix to the local time domain data to form time domain reference data, wherein the length of the cyclic prefix is ​​the OFDM symbol generated by the sending end Determine the length of the cyclic prefix; intercept multiple data sequences from the received OFDM time domain data, and perform correlation operations with the time domain reference data respectively to obtain multiple correlation calculation values; based on multiple correlation calculation values The maximum value is used to determine the timing point of the OFDM symbol. The technical solution solves the problem that in the prior art, there are many interference peaks, which cause offset and jitter in the theoretical optimal peak point, resulting in inaccurate timing of OFDM symbols.

The invention discloses a production method of frequency domain OFDM symbols. The production method comprises the following steps: separately generating fixed sequences and signaling sequences in frequency domain, filling the fixed sequences and the signaling sequences into a valid subcarrier, wherein the fixed sequences and the signaling sequences are arranged in an even-odd alternate array; and filling zero sequence subcarriers on both sides of the valid subcarrier to form the frequency domain OFDM symbol of a predetermined length. wherein according to the length and the number of the signaling sequences, root values in a CAZAC sequence generation formula are determined, different q values are selected to generate CAZAC sequences, the CAZAC sequences are subjected to cyclic shift, the signaling sequences are selected from all the CAZAC sequences based on the determined number of the signaling sequences. According to the method, the problem that the generated signaling sequences have the characteristics of cyclic shift or cyclic shift and phase shift in time domain is avoided, and also the problem of descending performance of the frequency domain channel estimation is solved, which further ensures that a receiving end still can receive and process the signal under the condition of carrier frequency deviation in the range of -500 kHz to 500 kHz.

The invention provides a generating method and a receiving method for a preamble symbol. The generating method is characterized by comprising the steps of: generating a time domain symbol having an arbitrarily three-segment structure based on an obtained time-domain main body signal; and generating a preamble symbol based on one or two time domain symbols. The generating method and the receiving method solve the problems that a DVB_T2 time domain structure in the existing DVB_T2 standard and other standards cannot be applied to coherent detection and the failure probability of the preamble symbol occurs in low-complexity receiving algorithm detection under a complex frequency selective fading channel.

The invention discloses a generation method for a frequency domain orthogonal frequency division multiplexing (OFDM) symbol. The generation method for the frequency domain OFDM symbol comprises the steps of respectively generating a fixed sequence and a signaling sequence in a frequency region, wherein the fixed sequence and the signaling sequence are constant-modulus sequences, and complex numbers in the fixed sequence and the signaling sequence are equal in modulus; filling the fixed sequence and the signaling sequence into an effective sub-carrier, wherein the fixed sequence and the signaling sequence are arranged in an odd-even staggered manner; and respectively filling zero-sequence sub-carriers on two sides of the effective sub-carrier to form the frequency domain OFDM symbol with predetermined length, wherein in the constant-modulus sequence generation step of the fixed sequence and the signaling sequence, a same sequence generation formula is acquired by endowing a CAZAC sequence with a same root value. According to the technical scheme of the method provided by the invention, a characteristic that the generated signaling sequence has cyclic shift or cyclic shaft and phase shift in the time domain is avoided, and the problem of reduction of frequency domain channel estimation performance is solved.

The invention discloses a frequency domain OFDM symbol generation method. The frequency domain OFDM symbol generation method includes the steps: respectively generating a fixed sequence and a signaling sequence on a frequency domain; filling an effective subcarrier with the fixed sequence and the signaling sequence, wherein the fixed sequence and the signaling sequence are arranged in a parity-alternative way; and respectively filling two sides of the effective subcarrier with zero sequence subcarriers to form a frequency domain OFDM symbol with a preset length. The technical scheme of the frequency domain OFDM symbol generation method solves the problem of the failure probability, for a lead symbol, for low complexity reception algorithm detection under a frequency selective fading channel, in the present DVB_T2 standard and other standards.

The invention discloses a generation method for a frequency domain OFDM symbol. The generation method for the frequency domain OFDM symbol comprises the following steps of determining an average power ratio of fixed sequences to signaling sequences; respectively generating the fixed sequences and a signaling sequence set on the frequency domain according to the average power ratio R; selecting one signaling sequence from the signaling sequence set and filling an effective subcarrier with the fixed sequences and the signaling sequences, wherein the fixed sequences and the signaling sequences are arranged in an odd-even interleaving manner; and respectively filling zero-sequence subcarriers at two sides of the effective subcarrier to form a frequency domain OFDM symbol with a preset length, wherein a sequence number of the selected signaling sequence in the set is signaling information carried by the OFDM symbol. According to the technical scheme, the problem of detection failure probability of a precursor symbol in a frequency selective fading channel by using a low-complexity receiving algorithm in the current DVB_T2 standard and other standards is solved.

The invention discloses a method for generating a preamble in a physical frame. The method comprises the following steps: obtaining a time domain OFDM symbol; determining the length of a cyclic prefix; intercepting a part of the time domain OFDM symbol with the length of the cyclic prefix from the rear of the time domain OFDM symbol to serve as the cyclic prefix; generating a modulation signal according to the part of the time domain OFDM symbol; and generating the preamble based on the cyclic prefix, the time domain OFDM symbol and the modulation signal. The technical scheme solves the problem of reduced frequency domain channel estimation performance, and generates the modulation signal by using the part of the time domain OFDM symbol, so that the generated preamble has good small frequency offset and timing synchronization performance. Further, it is guaranteed that received signals can stilled be processed within a carrier frequency deviation of-500kHz to 500kHz.

The invention discloses an OFDM symbol timing deviation estimation method. The OFDM symbol timing deviation estimation method comprises: receiving a transmitting signal sent by a transmitting end, thetransmitting signal comprising an IEEE1901.1 protocol preamble sequence signal, and transmitting the transmitting signal to a receiving end through a low-voltage power line physical channel; processing the received transmitting signal by using a sliding window to obtain a symbol timing metric function of the received transmitting signal; and obtaining the symbol timing deviation of the OFDM system according to the symbol timing metric function. The purposes that the algorithm has higher accuracy in a low-voltage power line transmission environment and the overall performance of the system isimproved are achieved.

A method for synchronizing code element timing includes calculating correlation of sampling sequence and delay sampling sequence of sampling sequence delay length N for generating correlation sequence, generating cross correlation sequence by taking a moving average on correlation sequence, carrying out differential operation on cross correlation sequence to generate differential post sequence, generating a moving average post sequence by taking a moving average on differential sequence, detecting peak value position of moving average post sequence for obtaining correct code element timing.

The invention provides an image registration method combined with edge regions and cross-correlation. The image registration method can be used for effectively selecting the edge regions of images, and selecting and improving similarity measure functions and optimization algorithms, and aims to improve robustness and real-time performance of image registration on the premise of meeting image registration accuracy. The image registration method includes the first step of extracting the edges of reference images and images to be registered; the second step of obtaining edge region images of the reference images and the images to be registered through edge images of the two images; the third step of calculating cross-correlation coefficients of the two edge region images obtained at the second step, and using a squared value of the cross-correlation coefficients as a similarity measure function; the fourth step of searching for registration result parameters enabling the similarity measure function obtained at the third step to reach the maximum by means of a particle swarm optimization algorithm.

A calibration system for RDSS (Radio Determination Satellite Service) channel zero value comprises a spread spectrum signal source, a microwave signal source, a frequency converter, a power divider, a double-channel digital oscilloscope, a first attenuator, a second attenuator, a control and processing computer and a vector network analysis instrument, wherein the spread spectrum signal source generates simulated RDSS spread spectrum signals; spread spectrum signal source outcoming signals are subjected to frequency conversion by the microwave signal source and the frequency converter so as to generate frequency points suitable for RDSS service channel input; a high-sampling rate digital oscilloscope is used for synchronously sampling the input / output signals of the RDSS service channel; and the control and processing computer is used for completing initialization of the oscilloscope, acquisition and loading of the oscilloscope channel data, orthogonalization of the channel data, carrier rotation, circulating autocorrelation, peak value searching, and zero value calculation and processing, so as to eventually obtain the absolute time delay of the RDSS service channel. According to the system provided by the invention, the signals consistent with the RDSS service system are adopted to serve as the reference, the calibration zero value can reflect the real conditions and the calibration precision is high.