288results about How to "Clock jitter is small" patented technology

The present invention discloses a method for modulating digital television ground broadcasting transmitter based on insertion training sequence and LDPC code, wherein the method comprises the following steps: 1) forming an FFT coded data block with the input bit flow through LDPC coding; 2) switching the FFT coded data block to a time domain discrete coded data sample block through IFFT; 3) forming a complex training sequence discrete sample block with a mode that a training sequence is used as a real part sequence and an operational indicator sequence is used as an imaginary part sequence; 4) continuously repeating the complex training sequence for four times to form a time domain insertion training sequence discrete sample block; 5) directly overlapping the time domain discrete coded data sample block with the time domain insertion training sequence discrete sample block for forming a time domain insertion training sequence coded data block; 6) inserting a circulating prefix into the time domain insertion training sequence coded data block for forming a signal frame; 7) forming a signal frame pulse with a square-root raised cosine roll-off filter; and 8) upconverting the baseband signal to the carrier.

The invention provides a multichannel high-speed parallel alternate ADC (Analog to Digital Converter) sampling circuit, which comprises an analog differential signal input module, a clock generating and phase-splitting module, a parallel ADC module and a data transmission module, wherein each data output end of the analog differential signal input module is connected with each corresponding data input end in the parallel ADC module; each clock output end of the clock generating and phase-splitting module is connected with each corresponding clock input end in the parallel ADC module, and each data output end of the parallel ADC module is connected with the data transmission module; and a phase splitting unit consists of passive power divider, wherein each passive power divider is used for equally dividing an input clock phase and then outputting the input clock phase. The multichannel high-speed parallel alternate ADC sampling circuit finishes the phase splitting on a clock signal by using the passive power dividers, is little interfered because no power supply is needed for supplying power, and has high phase-splitting precision on the clock signal and small clock jitter.

The invention discloses a method for transmitting an anti-noise wireless multi-media broadcast signal in a single frequency network. In the method, the wireless multi-media broadcast signal is transmitted to an air wireless channel by a wireless multi-media broadcast transmitter in the single frequency network through the following steps: the multimedia data streams are processed by a central data manager; a network data manager carries out LDPC (Low Density Parity Check) coding, code element modulating and constellation rotation on bit streams; space-frequency coding modulation is carried out; discrete data sample value blocks in the time domain and embedded discrete sample value blocks of training sequences in the time domain are superposed to form frames; pulse shaping is carried out; up-conversion is carried out on a baseband signal to a carrier wave to form a radio-frequency signal to be transmitted to the air wireless channel; and a receiver terminal receives and processes the signal transmitted by the wireless multi-media broadcast transmitter in the single frequency network. The method has the advantages of short synchronous receipt time, environmental background noise resistance, large-range controllable multiple services in the single frequency network, etc.

The invention discloses a space frequency modulation method for digital TV terrestrial broadcasting transmitter based on embedding training sequence and LDPC coding comprising: 1) coding input bit stream by LDPC and forming coding data block on frequency domain; 2) then demodulating by space-frequency coder and regulating time for synchronization; 3) converting data block after space-frequency modulation to time domain discrete data sample value block via IFFT; 4) training sequence serving as real part, service index sequence serving as imaginary part sequence, constituting discrete sample value block of plural training sequence; 5) repeating continuously the plural training sequence four times to form discrete sample value block of time domain embedded training sequence; 6) superposing the space-frequency modulated time domain discrete data sample value block and time domain embedding training sequence discrete sample value block to form space-frequency modulated time domain embedded training sequence data block; 7) inserting cyclic prefix as protective interval and forming signal frame; 8) pulse shaping to signal frame using square root raised consine roll-off filter; 9) up-converting base band to carrier.

The invention discloses a multimedia broadcast wireless signal single-frequency network anti-noise transmission method. In the multimedia broadcast wireless signal single-frequency network anti-noise transmission method of the invention, after processing of multimedia data stream by a central data manager on a single-frequency network multimedia broadcast wireless transmitter, network data manager bit stream LDPC coding, code element modulation, constellation rotation, empty frequency code modulation, frame body formation, time domain training sequence insertion framing, pulse shaping, and up-conversion to carrier waves, multimedia broadcast wireless signals form radio-frequency signals which are transmitted to an air wireless channel and received by a receiver terminal for processing signals transmitted by each multimedia broadcast wireless transmitter in a single-frequency network. The multimedia broadcast wireless signal single-frequency network anti-noise transmission method has the advantages of short receiving synchronization time, high transmission efficiency, controllable multiple services and the like.

The invention discloses a method for transmitting a digital mobile broadcast signal, which is a transmission proposal of time domain and frequency domain mixing. The method for transmitting a digital mobile broadcast signal disclosed by the invention has the advantages of low peak-to-average power ratio, short synchronization time, fading noise influence resistance, controllable multi-service etc.

The invention discloses a clock and data recovery circuit and a clock and data recovery method. The clock and data recovery circuit comprises a clock generation module, a clock selection module, a phase discriminator and a digital correlation processing module, wherein the clock generation module is used for receiving input clock signals, generating multi-channel clock signals identical in frequency and different in phase and sending the multi-channel clock signals to the clock selection module; the clock selection module is used for selecting continuous multi-channel clock signals from the multi-channel clock signals identical in frequency and different in phase to the phase discriminator and selecting one-channel clock signal serving as a data lock to the digital correlation processing module; the phase discriminator is used for receiving input data, oversampling the input data according to multi-channel oversampling clocks and sending the oversampled data to the digital correlation processing module; the digital correlation processing module is used for processing the oversampled data, recovering the data and feeding back one clock selection signal to the clock selection module; according to the feedback clock selection signal, the clock selection module selects and outputs the clock signals as same as the recovered data in phase. The clock and data recovery circuit has he advantages of simple structure, short locking time, small recovered clock jitter and the like.

The invention discloses a modulation method for digital TV terrestrial broadcasting transmitter based on time domain training sequence and LDPC coding comprising: 1) coding input bit stream by LDPC and forming FFT coding data block on frequency domain; 2) converting FFT coding data block to time domain discrete coding data sample value block via IFFT; 3) inserting cyclic prefix as protective interval to time domain discrete coding data sample block and forming time domain cyclic prefix discrete coding data sample block; 4) continuous four time domain cyclic prefix discrete coding data sample value blocks constituting a frame body; 5) training sequence serving as real part of plural training sequence, service index sequence serving as imaginary part sequence to constitute discrete sample value block of plural training sequence; 6) inserting the discrete sample value block (frame head) of plural training sequence in signal frame for forming frame body;7) pulse shaping to signal frame using square root raised consine roll-off filter; 8) up-converting base band to carrier.

The invention discloses a multiuser OFDM modulation method based on embedded training sequence and LDPC coding, which includes the following steps: 1) each user inserting zero even in its own training sequence to form discrete FFT training sequence block; 2) each user performing LDPC coding to its own input data bit stream to further form an FFT coding data block; 3) directly superimposing the discrete FFT training sequence block and the FFT coding data block to form an FFT embedded training sequence coding data block; 4) adopting IFFT to switch the FFT embedded training sequence coding data block into a time-domain discrete sample block; 5) taking circulating prefix as guard interval to insert into the time-domain discrete sample block to from a signal frame; 6) using a Raised Cosine Roll-off Filter to perform pulse shaping to the signal frame; 7) upconverting the baseband signal to carrier. The method has advantages of short synchronization time, channel dwindle resistance and multiuser disturbance resistance and the like.

The invention discloses a multimedia broadcast mobile signal robust framing modulation method, and belongs to a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcast mobile signal robust framing modulation method has the advantages of low peak-to-average power ratio, short synchronous time, robustness, controllable multi-service and the like.

The invention discloses an anti-fading digital mobile broadcast signal transmission method which is a time domain frequency domain mixed transmission scheme. The anti-fading digital mobile broadcast signal transmission method of the present invention has the advantages of low peak-to-average power ratio, short synchronization time, fading resistance, control of multiple services and the like.

The invention discloses a transmission method of anti-noise digital wireless broadcasting signals. The transmission method is a framing modulation scheme with time domains and frequency domains being mixed. By means of the cascading interleaving coded modulation, the training sequence optimization design, the signal generating models and a signal selection method of the transmission method of the anti-noise digital wireless broadcasting signals, original signals of OFDM signals can be easily processed at a receiver end through processing and restoring, and the transmission method has the advantages of being low in PAPR, short in synchronous time, channel fading resistant, capable of controlling multiple services, and the like.

The invention discloses an anti-noise digital broadcast wireless signal transmitting method, and relates to a time domain / frequency domain mixed scheme. The anti-noise digital broadcast wireless signal transmitting method has the advantages of low peak-to-average power ratio, short synchronization time, resistance to channel noise, controllable multiple services and the like.

The present invention discloses an optical path delay rapid measurement apparatus based on a frequency domain standing wave method. The apparatus modulates the repeat frequency of an optical frequencycomb signal, and the optical frequency comb signal passes through an optical path to be measured and a reference optical path so as to pass through an optical combining path, and the apparatus realizes high-precision and fast detection of an optical path delay by using the frequency domain standing wave method. The present invention adopts a repetitive-frequency rapid tunable optical frequency comb signal generator, which transmits an optical frequency comb signal with low phase noise and extremely low clock jitter, so that measurement accuracy is improved, and rapid measurement is implemented. At the same time, the present invention adopts the optical frequency comb signal as a carrier signal that occupies a certain spectral width in the optical domain. When an optical path difference between the reference optical path and the optical path to be measured satisfies a certain minimum value, two optical signals are non-coherent in the optical domain after being synthesized by a 3dB coupler. Therefore, the strength of the signal synthesized by the coupler is not affected by two random phase shifts, and a system anti-interference ability is strong.

A digital-analog conversion method which can decrease jitter phenomenon when operation is carried on with two clock messages in different preriod includes the following steps: monitoring phase relation between two clock messages: starting transmission of multiset of wave form sampling stored in advance corresponding to each rising wave range of the first clock message and there will be a phase difference existing between any two sets of wave form sampling; exporting wave form sampling for each set corresponding to rising wave range of the second clock message and convertnig one set selected out from multiset of wave form sampling stored in advance according to phase relation into analog message. A digital-analog converter is composed of phase monitor, multiple wave form sampling mater, multiplexer and a digital-analog conversion circuit.

The invention discloses a method for framing and modulating wireless multimedia broadcast signals, which is a framing and modulating scheme mixing a time domain with a frequency domain. The method for framing and modulating wireless multimedia broadcast signals has a signal generation mode and a signal selection method which are easy to process and recover an original signal obtaining an OFDM (Orthogonal Frequency Division Multiplexing) signal at a receiver end, and has the advantages of being low in peak average power ratio, short in synchronization time, resistant to channel fading, capableof controlling various businesses, etc.

The invention discloses a method for framing and modulating anti-fading wireless multimedia broadcast signals, which is a framing and modulating scheme that time domains and frequency domains are mixed. The method for framing and modulating the anti-fading wireless multimedia broadcast signals disclosed by the invention has the advantages of low peak-to-average power ratio, short synchronization time, anti-fading property, controllable multi-service and the like.

The invention provides a method for improving distance measurement precision of a responder and aims to provide a simple and reliable method for improving downlink frame synchronization trailing edge pulse precision. According to the method, in a noncoherent mode, after an uplink signal is received by the responder, the uplink frame synchronization information is extracted after de-spreading, demodulation frame synchronization processing, an uplink frame synchronization signal is sampled by utilizing the downlink frame synchronization trailing edge pulse, the sampling value after re-framing is sent to a ground station through a downlink, and distance measurement is carried out by the ground station through calculating time delay between sending frame synchronization and receiving frame synchronization. The method for improving distance measurement precision of the responder is advantaged in that the compensation function is realized through programming in an FPGA chip of a responder hardware platform, a system clock of the responder is used as a modulation clock of the downlink, a 32-bit frequency control word accumulator DDS is utilized to generate a code sending clock, and the code sending clock is utilized to generate the downlink frame synchronization trailing edge pulse.

The invention discloses a noise-resistance framing modulation method for mobile multi-media broadcast signals of a single frequency network, which is a time domain, frequency domain and space domain hybrid framing modulation scheme. The method has the advantages of low peak-to-average power ratio, short synchronous time, robustness, controllability in multiple services and the like.

The invention discloses an anti-interference wireless multimedia mobile broadcast signal framing modulation method, which is a time domain / frequency domain combined framing modulation scheme. The anti-interference wireless multimedia mobile broadcast signal framing modulation method has the advantages of low peak-to-average power ratio, short synchronization time, resistance to the influence of noises, multi-service controllability and the like.

The invention discloses a sudden clock recovery method for the dynamic optimal regulation at a receiver in a passive optical network when multistage amplitude modulation is used. The method is as follows: a received optical signal in an optical receiver positioned in an optical line terminal is converted into an electric signal by an optical detector and a transimpedance amplifier; and the electric signal is the inputs of subsequent 3 circuit links, wherein 2 circuit links generate a clock signal through an injection locked oscillator, and the injection intensity of the two circuit links are regulated automatically and dynamically. Compared with other clock recovery schemes under a condition of adopting non-return-to-zero-codes for multistage amplitude modulation, the scheme with a simplestructure has the advantages of low power consumption and small occupation of chip area. The distinctive dynamic regulation function of the method can achieve short locking time and light after-locking clock vibration at the same time.

The invention discloses a multimedia broadcasting wireless signal anti-interference framing modulation method which is a time domain and frequency domain mixed framing modulation scheme. The multimedia broadcasting wireless signal anti-interference framing modulation method provided by the invention has the advantages of low peak average power ratio, short synchronizing time, anti-interference, capability of controlling multiple services, and the like.

The invention discloses an anti-interference wireless signal transmission method for a digital broadcast, and relates to a mixed framing modulation scheme of the time domain and the frequency domain. According to the training sequence optimization design, the signal generating scheme and the signal selecting method of the anti-interference wireless signal transmission method for the digital broadcast, OFDM signals can be processed and recovered at a receiver end easily to obtain original signals of the OFDM signals. The anti-interference wireless signal transmission method for the digital broadcast has the advantages of being low in peak-to-average power ratio, short in synchronization time, resistant to channel fading, multiple in controllable service and the like.

The invention discloses an anti-interference radio signal framing modulation method for a multimedia broadcast single-frequency network. The method is a time domain / frequency domain / space domain hybrid framing modulation scheme. The anti-interference radio signal framing modulation method for the multimedia broadcast single-frequency network has the advantages of low peak to average power ratio, short synchronization time, anti-interference performance, multi-service controllability and the like.

The invention discloses a single-frequency-network anti-noise mobile digital broadcast signal transmission method which is a transmission scheme mixing a time domain, a frequency domain and a spatial domain. By using the single-frequency-network anti-noise mobile digital broadcast signal transmission method of the invention, PAPR is low, synchronization time is short, noise can be resisted, and aplurality of services can be controlled and so on.

The invention discloses an anti-interference wireless multimedia broadcast signal framing modulation method, which is a time domain / frequency domain combined framing modulation scheme. The anti-interference wireless multimedia broadcast signal framing modulation method has the advantages of low peak-to-average power ratio, short synchronization time, anti-interference performance, multi-service controllability and the like.

The invention discloses a robust mobile signal framing modulation method for a multimedia broadcast single frequency network, and relates to a mixed framing modulation scheme of the space domain, the time domain and the frequency domain. According to the training sequence optimization design, the signal generating scheme and the signal selecting method of the robust mobile signal framing modulation method for the multimedia broadcast single frequency network, OFDM signals can be processed and recovered at a receiver end easily to obtain original signals of the OFDM signals. The robust mobile signal framing modulation method for the multimedia broadcast single frequency network has the advantages of being low in peak-to-average power ratio, short in synchronization time, resistant to channel fading, multiple in controllable service and the like.

The invention discloses a method for framing and modulating anti-interference wireless multimedia broadcast signals in a single frequency network. The method provides a framing and modulating scheme mixing a space domain, a time domain and a frequency domain. According to a training sequence optimal design, a signal generation pattern and a signal selection method of the method for framing and modulating the anti-interference wireless multimedia broadcast signals in the single frequency network, an original signal of an OFDM signal can be easily obtained through processing and recovery on a receiver terminal. The method for framing and modulating the anti-interference wireless multimedia broadcast signals in the single frequency network has the advantages that the peak-to-average power ratio is low, synchronization time is short, channel fading is prevented, and multiple services can be controlled.

The invention discloses a robust transmission method of digital broadcast mobile signals, which is a mixed transmission scheme of time domain and frequency domain. The method has the advantages of low PAPR (peak-to-average power ratio), short synchronous time, robustness, multiple controllable services and the like.

The invention discloses an anti-noise digital mobile broadcast signal transmitting method, which relates to a time domain-frequency domain hybrid transmitting scheme. The anti-noise digital mobile broadcast signal transmitting method has the advantages of low peak-to-average power ratio, short synchronization time, noise resistance, multi-service controllability, and the like.