40results 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 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 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%.