621 results about "Carrier synchronization" patented technology

A method and apparatus for use with a power conversion configuration including a pulse width modulated (PWM) converter, a PWM inverter and master and slave carrier signal generators wherein the master and slave carrier signal generators receive master and slave PWM frequency signals and generate master and slave carrier signals as a function thereof, PWM signals for controlling the converter and the inverter derived by comparing converter and inverter modulating waveforms to converter and inverter carrier signals, respectively, the method comprising the steps of identifying a phase difference between the master and slave carrier signals, using the phase difference to modify subsequent slave carrier signals to substantially conform the slave carrier signal frequency and phase to the master carrier signal frequency and phase and using the master carrier signal and the modified slave carrier signal to generate control signals for the converter and the inverter.

A system for spread spectrum power line communications employs a harmonic modulation (HM) transmitter coupled to the power line for transmitting message bits to an HM receiver. The spread spectrum accommodates a plurality of HM transmitters simultaneously occupying the same bandwidth. The spectrum of HM, in a frequency range above 60 Hz but below the maximum frequency that will carry through a distribution transformer, is ideal in combating carrier synchronous noise since it can be interleaved with the noise harmonics and therefore be effectively spectrally disjoint with the synchronous noise process spectrum.

The invention relates to a method for conducting LOFDM system timing and carrier synchronization by utilizing training sequence. The method comprises the following steps: adding training symbols before data symbols for the detection and the synchronization of initial signals; and completing synchronous signal capture through assessing and compensating carrier deviation and timing deviation of signals in system transmission course, and achieving ideal synchronous capture effect. The invention designs the frame format and the training sequence of the LOFDM system and proposes the time and the frequency synchronous method synchronous capture method of the LOFDM system: initial signal detection, rough timing and synchronization and rough decimal multiple frequency offset estimation, accurate timing and synchronization and integral multiple frequency offset estimation, and accurate decimal multiple frequency offset estimation; and accurate time and frequency offset estimation can be obtained under the conditions of low noise-signal ratio and big frequency offset, and when the noise-signal ratio is higher than 2 dB, 100% signal detection can be realized, so as to realize the ideal effect of synchronous capture.

The present invention relates to a signal generator and signal processor for single carrier wireless communication systems with frequency domain equalizer, which are operable to use pseudorandom-noise sequences as part of a preamble and possibly as cyclic prefix. The different arrangements and examples of said pseudorandom-noise sequences could be used for coarse timing synchronization, channel estimation, carrier synchronization, signal-noise-ratio estimation and channel equalization.

The invention relates to a device for realizing multi-mode mobile communication terminal frequency switch and automatic control, and a relative method, wherein each mode sending/receiving module of multi-mode mobile terminal shares one crystal vibrator to save cost and energy consumption, to allow the terminal to use automatic frequency lock ring at each mode, to effectively keep the carrier wave synchronous of communication chain. And the invention comprises: a multi-mode automatic frequency control word refresher, a voltage-control crystal vibrator and a digit/analogue converter; the refresher is used to select and calculate the frequency control word of target mode; the digit/analogue converter based on said control word generates control voltage via digit signal; said vibrator based on the control voltage generates reference frequency signal; and the invention also provides a multi-mode automatic frequency control word refreshing module to replace the multi-mode automatic frequency control word refreshing device.

The invention provides a frequency offset estimation method for high-dynamic large-frequency-offset burst signals. The estimation method comprises burst frame capturing, estimation and correction of Doppler changing rate, basic frequency offset estimation, and Doppler frequency offset estimation, a burst signal frame is formed by a pilot frequency segment and a data segment, and a receiver employs the pilot frequency segment to realize frequency offset estimation. Firstly, the burst frame capturing is realized via a threshold comparison method; then the segmentation of pilot frequency data is realized, a DFT-assistant hierarchical iteration method is employed to estimate the Doppler changing rate, and the estimation value of the Doppler changing rate is used for dynamic compensation of the pilot frequency segment; later, DFT-assistant basic frequency offset estimation of signals after dynamic correction is realized; and finally, the estimation value of the Doppler changing rate and the basic frequency offset estimation value are combined to estimate the frequency offset of each symbol in the burst signal frame. According to the frequency offset estimation method, the data segment is compensated by the adoption of the frequency offset estimation result so that the data segment has small frequency changing rate and residual frequency offset, and bit synchronization, frame synchronization, and carrier synchronization can be realized.

A rectangular-to-polar-converter receives a complex input signal (having X₀ and Y₀ components) and determines an angle φ that represents the position of the complex signal in the complex plane. The rectangular-to polar-converter determines a coarse angle φ₁ and a fine angle φ₂, where φ=φ₁+φ₂. The coarse angle φ₁ is obtained using a small arctangent table and a reciprocal table. These tables provide just enough precision such that the remaining fine angle φ₂ is small enough to approximately equal its tangent value. Therefore the fine angle φ₂ can be obtained without a look-up table, and the fine angle computations are consolidated into a few small multipliers, given a precision requirement. Applications of the rectangular-to-polar converter include symbol and carrier synchronization, including symbol synchronization for bursty transmissions of packet data systems. Other applications include any application requiring the rectangular-to-polar conversion of a complex input signal.

The invention discloses a multi-carrier synchronizing system and a multi-carrier synchronizing method which are applied to an OFDM multi-carrier system. The multi-carrier synchronizing system comprises a symbol synchronizing module and a frame synchronizing module, wherein the symbol synchronizing module carries out related calculation on a received sequence and a local sequence and determines the symbol synchronizing position by detecting the related peak value of a continuous symbol window, the frame synchronizing module calculates the cumulative sum of the differentials between a phase of a current symbol and an average phase of former symbols, compares the cumulative sum with a preset judgment threshold and finds out the frame synchronizing position after judgment. The multi-carrier synchronizing method comprises the steps of carrying out related calculation on received signals and the local sequence after average filtering is carried out on the received signals, determining the symbol synchronizing position by detecting the related peak value of the continuous window, and judging whether frames are synchronized by calculating the phase differential of two continuous symbols according to the symbol synchronizing position. Compared with the existing synchronizing technology, the multi-carrier synchronizing system and the multi-carrier synchronizing method have the advantages of being low in complexity, high in accuracy and capable of being achieved easily through hardware.

The invention discloses an inverter parallel system based on a CAN (controller area network) bus and a carrier synchronization method of the inverter parallel system. The system is characterized by comprising a central monitor, a host and N slaves, wherein the central monitor is used for monitoring working states of the host and the N slaves and can assign a new host when the system has a single-point failure or a multi-point failure; the host is used for sending carrier synchronization signals and monitoring working states of the N slaves; the N slaves are used for receiving the carrier synchronization signals and realizing carrier synchronization and can determine a new host independently when the parallel system has the single-point failure or the multi-point failure. The problem of failure of carrier synchronization when the parallel system has the single-point failure or the multi-point failure can be solved at the system level, and the reliability and the accuracy of carrier synchronization of the parallel system can be improved, so that free switching of modules and high-capacity modular parallel connection can be realized on the premise of carrier synchronization.

The invention discloses an SOQPSK (shaping offset quadrature phase shift keying) carrier synchronization method based on pilot frequency and soft information combined assistance, mainly solves the problem in the existing short frame burst communication system carrier synchronization technique that the complexity is high and the carrier deviation estimation range is small. The implementation steps are as follows: firstly, according to pilot frequency assistant maximum likelihood carrier synchronization method, the rough estimation values of carrier frequency deviation and phase deviation are obtained, and the phase rough estimation value is used to revise the receiving signals; then, the frequency deviation one dimensional fine estimation interval, and phase deviation one dimensional fine estimation interval are respectively determined; and in the frequency deviation and phase deviation fine estimation intervals, according to the rule of maximizing the mean square value obtained during demodulation of soft information by SOQPSK, one dimensional search is performed to obtain the precise estimation value of carrier frequency deviation and phase deviation. A small amount of pilot frequency overhead is utilized, large carrier deviation with comparatively low operation complexity is revised, effective carrier synchronization is realized, nearly ideal bit-error performance of coherent demodulation is obtaind, and the method is suitable for the short frame burst communication system.

The invention provides a method for realizing accurate synchronous playing of a Bluetooth headset. The method comprises the following steps: sending an audio signal to a left Bluetooth headset througha market device, wherein the left Bluetooth headset sends the audio signal to a right Bluetooth headset at the starting time of some slot, and the lasting time of each slot is fixed; converting the received audio signal through the right Bluetooth headset to obtain a timing synchronization signal, timing synchronization error and carrier synchronization error; synchronizing the starting time of the timing synchronization signal and the slot starting time that the left Bluetooth headset sends the audio signal to the right Bluetooth headset; synchronously triggering related DMA controllers through the left Bluetooth headset and the right Bluetooth headset in some time; synchronously accessing the audio signal through the DMA controller of the left Bluetooth headset and the right Bluetooth headset; and sending the audio signal to related playing devices. According to the method, the left Bluetooth headset and the right Bluetooth headset are subjected to time synchronization, and on thatbasis, data are accessed through the related DMA controllers, and thus the accurate synchronizing playing is achieved.

An anti-parallel loop carrier synchronization circuit for coherent binary phase shift keying (BPSK) demodulation is disclosed. One embodiment comprises an anti-parallel dual phase-locked loop (PLL), which locks the carrier by its upper PLL (0°) and lower PLL (180°) alternately, according to the data bits contained in the received BPSK signal. Demodulation of the data is completed through control of the upper PLL and the lower PLL.

The invention provides a joint LDPC encoding recursive MSK modulation and demodulation system, which comprises a transmitting end and a receiving end. The transmitting end comprises an LDPC external encoder and a recursive MSK modulator, and the receiving end comprises a quadrature down conversion and low-pass filter, a coarse carrier frequency offset estimation module, a buffer, a demodulation selector, an MSK differential demodulator, an N frame synchronization head-related detector, an MSK coherent demodulator, a carrier and timing synchronization processing module, a parallel/series conversion module and an LDPC decoder. The invention completely eliminates the performance loss caused by MSK differential encoding by fully integrating the recursive MSK differential encoding part into LDPC codes, fully utilizes the characteristic that the recursive MSK can carry out the differential demodulation, rapidly realizes the detection of frame synchronization head sequence of the LDPC codes under the premise of having no need of precise carrier synchronization, further switches to the MSK coherent demodulation, carries out synchronization and LDPC decoding and realizes the functions of rapid demodulation and decoding.

The invention discloses a three-phase inverter parallel-connection control method without an output isolation transformer. The method comprises the following steps: an output end of each three-phase inverter is connected with an LCL filter, and a filtering capacitor of each LCL filter is connected with a dumping resistor in series, so that the stability is improved, the harmonic wave of a harmonic point is limited, and stability range of control parameters is increased. By means of pre-synchronization before parallel connection and carrier synchronization in the process of parallel connection operation, the phases among the three-phase inverters and parallel-connected communication buses are synchronized, carriers among the three-phase inverters connected in parallel are synchronized, and stability of parallel connection is guaranteed. By means of the algorithms combining pole assignment capacitor voltage control and virtual resistance matching control, the response speed of the inverters is improved, the control performance is improved, and the influence on parallel-connection current sharing by circuit resistance is lowered. By means of seamless mode switching and alternative current over-current and short-circuit failure protection base on three-ring control, under the condition of absence of the output isolation transformer, the three-phase inverter parallel-connection control method is used for independently resolving short-circuit failures of a parallel-connection micro power grid.

An approach is provided for supporting carrier synchronization in a digital broadcast and interactive system. A carrier synchronization module receives one or more signals representing a frame that includes one or more overhead fields (e.g., preamble and optional pilot blocks and one or multiple segments separated by pilot blocks). The module estimates carrier frequency and phase on a segment by segment basis and tracks frequency between segments. Carrier phase of the signal is estimated based upon the overhead field. Estimates carrier phase of random data field are determined based upon the estimated phase values from the overhead fields, and upon both the past and future data signals. Further, the frequency of the signal is estimated based upon the overhead fields and/or the random data field. The above arrangement is particularly suited to a digital satellite broadcast and interactive system.

A method for determining an angle of arrival (AOA) of a received signal is disclosed, comprising: generating a baseband information signal by mixing a received signal with a local oscillator (LO) signal, the received signal being an in-phase signal and quadrature signal uncorrelated with each other and derived from different input data sets; obtaining baseband signal samples of the baseband information signal having an in-phase signal sample and a quadrature signal sample; determining a transmitter phase offset based on an estimated correlation between the in-phase signal samples and the quadrature signal samples; performing a plurality of phase measurements using a plurality of antennas to obtain a plurality of phase measurements; correcting the plurality of phase measurements based on the transmitter phase offset to produce a plurality of corrected phase measurement; and calculating an AOA of the received signal based on the difference between the plurality of corrected phase measurements.

The invention provides a communication link used for a telemetry and telecontrol communication system. An uplink broadcasing and downlink TDMA (time division multiple access) mode is adopted to solve the measurement and control problems of a single ground station for multiple aircrafts. A downlink adopts hybrid spread spectrum BPSK (binary phase shift keying) with multiple stages of adjustable gain for modulation, an uplink adopts coded spread spectrum QPSK (quadrature phase shift keying) with fixed gain for modulation, so that the anti-interference, anti-interception and anti-capturing capacity of a wireless link is improved, and asymmetry of the uplink and the downlink is considered. Both the uplink and the downlink adopt a single-pulse modulation symbol packet transmission mode, a fixed interval is inserted into every two adjacent symbol pulses, and accordingly, the spread spectrum signal capturing, tracking and synchronizing complication of receivers is reduced. Non-coherent demodulation is adopted, a complicated carrier synchronization problem is avoided, and the design and project realization of the receivers are further simplified. The complicated carrier synchronization problem is avoided, and wireless communication between a single ground station device and multiple telecontrol terminal devices is realized.

The invention provides a timing synchronization method and a timing synchronization system for power line carrier communication. The system comprises an analog-to-digital converter, an I/O (Input/Output) demodulator, a narrowband interference detector, an adaptive filter, a normalization module, an auto-correlation calculation module, a comparator and a postprocessor, wherein an OFDM (Orthogonal Frequency Division Multiplexing) carrier signal is converted into an OFDM carrier frequency domain signal by the analog-to-digital converter, the I/O demodulator and the narrowband interference detector. The method comprises the following steps: 1, acquiring average power P of each OFDM subcarrier f; 2, performing narrowband interference detection on the OFDM subcarrier f; 3, filtering the OFDM signal and then performing normalization processing; 4, acquiring start time of the OFDM carrier signal and outputting an OFDM carrier synchronization signal. Compared with the prior art, the timing synchronization method and the timing synchronization system for power line carrier communication have the advantage of higher robustness under various different channel environments of narrowband interference, pulse noise, multi-path propagation and violent change or nonlinear input signal amplitude.

The invention discloses a method of symbol timing synchronization and carrier synchronization applied to an OFDM system. The method comprises the following steps that a transmitter module of the OFDM system sends a first training sequence and a second training sequence before an effective OFDM symbol; accurate symbol timing synchronization is carried out according to the first training sequence in a receiving process; thick carrier frequency offset estimation is carried out according to the received first training sequence; thin carrier frequency offset estimation is carried out according to the received first training sequence and the received second training sequence; correction is carried out on the thin carrier frequency offset estimation according to thin carrier frequency offset estimation values; total carrier frequency offset is calculated according to the results of the first step and the third step; and carrier frequency offset compensation is carried out according to the last step. The method of the symbol timing synchronization and the carrier synchronization applied to the OFDM system is not only low in complexity, but also good in performance, the timing error of the timing synchronization and the error of mean square of the carrier frequency offset estimation are both small, the method is insensitive to signal noise and the carrier frequency offset, and the maximum range capable of being estimated is four times of subcarrier spacing.

An apparatus of compensating for a frequency offset using a guard interval and a pilot symbol, which are inserted at a transmitter, in an OFDM (Orthogonal Frequency Division Multiplexing) system. The OFDM system receives an OFDM signal in which a pilot symbol is inserted in data of a frame unit at regular intervals and a guard interval is inserted in a data symbol. In the system, a first carrier synchronizer receives a data symbol stream obtained by converting the OFDM signal to digital data, and detects a guard interval of each data symbol, to compensate for a coarse frequency offset. A fast Fourier transform part OFDM-demodulates a signal output from the first carrier synchronizer. A second carrier synchronizer detects the pilot symbol from the demodulated data symbol stream to compensate for a fine frequency error.

The invention provides a method for realizing a multi-user spread spectrum broadcasting station based on parallel interference cancellation algorithm, which can realize data transmission between a plurality of users and a receiver at the same time under the same frequency. The parallel interference cancellation algorithm is realized on a receiver; and before the algorithm is realized, a code synchronization module of the receiver outputs a spreading code of the current phase position, and a despreading module outputs a primary despreading signal. The parallel interference cancellation algorithm comprises the following steps: firstly, a spreading code is utilized to despread the primary despreading signal for the second time and the cross correlation coefficients of different user spreading codes are worked out at the same time; secondly, all secondary spread spectrum signals that interfere with users are multiplied and added with the corresponding cross correlation coefficients respectively to obtain interference signals; thirdly, the interference signals are subtracted from baseband digital signals to obtain baseband signals without interference; and finally, code synchronization, despreading and carrier synchronization demodulation are performed to the baseband signals without interference so as to obtain the current user data. According to the invention, the processes are carried out concurrently, so that radio station communication and data transmission between a plurality of users and the receiver can be realized in the same frequency band at the same time.

A clock regeneration circuit for regenerating a clock signal for demodulating data from an AM data multiplex modulated signal where digitally modulated signals are multiplexed in the same frequency band as those of an amplitude-modulated signal at the same time. The carrier for an amplitude-modulated signal is extracted from an AM data multiplex modulated signal where digitally modulated signals are multiplexed in the same frequency band as those of the amplitude-modulated signal at the same time through a band-pass filter, and the oscillation frequency of a voltage-controlled oscillator is controlled by the output of a phase comparator through a loop filter. The oscillation output of the voltage-controlled oscillator is supplied to a direct digital synthesizer and the phase of the carrier extracted through the band-pass filter is compared with the phase of the output of the direct digital synthesizer using the phase comparator. The oscillation output of the voltage-controlled oscillator is then synchronized with the carrier for the amplitude-modulated signal to produce a clock signal for demodulating data.