10 results about "Residual carrier" patented technology

The invention discloses a high-sensitivity GPS signal rapid capturing method and system, and the method comprises the steps: S1, carrying out the down-conversion and sampling of a satellite analog signal transmitted by a navigation satellite, and obtaining a digital baseband signal of residual carrier frequency offset; s2, carrying out time delay processing on the data, putting the data into buffer queues, and capturing the data at the back stage of each buffer queue at the same time to form multi-path parallel capturing; s3, segment interception is carried out, and first data with the starting point being cache output is intercepted; s4, by utilizing the linear property of FFT, integral data is shortened through an integral-clearing process, so that the calculation complexity and the calculation time related to subsequent circulation are reduced; s5, performing FFT (Fast Fourier Transform) operation on the data output in the step S4; s6, performing cyclic shift on an output result of the FFT operation in the step S5 by using the frequency domain cyclic shift property of the FFT so as to search and compensate Doppler frequency offset; s7, carrying out zero padding on locally stored pseudo codes, and carrying out correlation operation on the pseudo codes and the data output in the step S6 by utilizing FFT / IFFT cyclic convolution to complete coherent integral operation of a single-path signal; and S8, arranging and combining the integral results, sending the integral results to a peak detector, and outputting the results according to a threshold. According to the method, weak GPS signal capturing can be efficiently and rapidly carried out, and the calculated amount can be greatly reduced on the premise that the capturing precision is guaranteed.

The invention discloses a frequency-modulated continuous wave laser radar signal generation method, a frequency-modulated continuous wave laser radar signal detection method and a frequency-modulated continuous wave laser radar signal detection system. The system comprises a transmitting end and a receiving end, wherein the transmitting end determines a frequency guard interval between a frequency-modulated continuous wave signal and zero frequency according to a modulation bandwidth of a radar signal and a line width of a transmitting laser; generating a frequency modulation continuous wave signal according to the frequency protection interval, modulating the frequency modulation continuous wave signal, generating radar detection signal light which is to be sent and contains residual carrier waves, performing power amplification on the radar detection signal light, and transmitting the radar detection signal light by using an optical lens; the receiving end receives the reflected signal light reflected by the target; filtering, beat frequency and coherent detection are carried out on the reflected signal light and the radar detection signal light to obtain an electric signal, and the electric signal is converted into a digital signal; performing electric domain filtering on the digital signal, and extracting a residual carrier and a beat frequency signal; performing phase noise compensation on the beat frequency signal based on the residual carrier to obtain a signal after phase recovery; and estimating the distance and the relative speed of the target based on the residual carrier and the phase-recovered signal.

The invention belongs to the technical field of optical fiber communication and coherent optical communication, and discloses a multi-residual carrier modulation method, demodulation method and system. The system comprises a transmitting end and a receiving end, the transmitting end comprises a mapping module and a modulator; the mapping module is used for modulating and mapping a to-be-sent digital signal and generating a corresponding modulation signal; the modulator modulates an optical carrier according to the modulation signal to obtain a modulated optical signal; introducing an optical carrier component comprising a plurality of optical carriers into the modulated optical signal to form a composite optical signal comprising the modulated optical signal and a residual carrier component; the receiving end comprises a detection module, a compensation module and a signal recovery module; the detection module performs beat frequency on the received composite optical signal and local oscillation light to realize coherent detection to obtain an electric signal; the compensation module compensates the electric signal; and the signal recovery module filters the compensated signal, and performs phase noise compensation on the signal by using any residual carrier component in the residual carrier components obtained by filtering to obtain a signal after phase recovery.

To improve frequency utilization efficiency in transmitting a frame having a TMCC section in addition to a subframe section.SOLUTION: A transmitter is used in a broadcast transmission system which transmits an OFDM frame in which a TMCC section and a subframe section following the TMCC section are arranged in a time-division manner. The transmitter includes time interleaving means which performs time interleaving to disperse modulation symbols to be transmitted by data carriers in a time direction. The time interleaving means has a symbol buffer for buffering the modulation symbols, for each data carrier. In the case where residual carriers having no TMCC signal assigned thereto in the TMCC section are used as data carriers for allocating data in the subframe section, the time interleaving means determines a length of the symbol buffer on the basis of the number of data carrier symbols in the subframe.SELECTED DRAWING: Figure 13

The invention discloses a low-crosstalk long-distance sensing integrated device and a very-low-frequency sensing method, and relates to the technical field of fusion of optical fiber sensing and optical fiber communication. The device comprises a laser, a coupler, a communication modulation device, a sensing modulation device, an optical fiber transmission and relay link, a communication receiving device, a sensing receiving device and a signal processing device. The communication modulation device adopts digital subcarrier multiplexing and reserves a guard interval in a frequency spectrum center, and residual carrier filtering is combined to reduce the inductance crosstalk; the sensing modulation device realizes high-extinction-ratio pulses through a cascade light modulator, and the signal-to-noise ratio is improved. The optical fiber link adopts a bidirectional amplification relay module to synchronously amplify forward and backward signals so as to realize ultra-long distance transmission. The signal processing device carries out high-density sampling and space-time dimension fusion on the sensing beat frequency signals, and very low frequency vibration information is effectively extracted. According to the invention, common-light-source, low-crosstalk, long-distance, very-low-frequency and high-sensitivity integrated transmission and detection of communication and sensing signals are realized.

A method and an apparatus for satellite laser broadband demodulation are provided. The method includes: setting a residual carrier to a carrier acquisition range of a receiver, pulling the residual carrier to an MHz level by adjusting a frequency of a local oscillator laser, and obtaining a precise carrier frequency according to an accurate frequency acquisition, such that the residual carrier enters a fast acquisition band of a carrier tracking phase-locked loop. After carrier acquisition is achieved, carrier tracking and data recovery processing are performed. According to the present disclosure, signal equalization of an ultra-high bandwidth / ultra-high bit rate can be implemented, and carrier acquisition, tracking, and demodulation are quickly achieved for a modulation signal in a high dynamic range.

The application provides a low-orbit satellite spread spectrum orthogonal frequency division multiplexing frequency offset estimation method based on a carrier loop, and belongs to the technical fields of satellite communication and signal processing. The method comprises the following steps: a receiver divides an integral frame sequence into multiple accumulation blocks with the same structure in time sequence; phase rotation factors of residual carriers corresponding to each symbol period in a current accumulation block are calculated respectively; carrier stripping values and carrier correlation values of each subcarrier in each symbol period in the current accumulation block are calculated in turn respectively; accumulation correlation values corresponding to each subcarrier in the current accumulation block are calculated respectively; the carrier loop state of the current accumulation block is judged according to the index of the current accumulation block, and the carrier frequency control word of the next accumulation block is calculated; the processing of all accumulation blocks is iterated, and the average value of all carrier frequency control words obtained after the carrier loop converges is taken as the frequency offset estimation value of the integral frame sequence. The application can provide high-precision and continuous stable frequency observation values.

The invention relates to the technical field of radio frequency communication, and provides a carrier frequency offset compensation method and device, equipment, a medium and a program product, and the method comprises the steps: carrying out the frequency offset compensation of a first subframe of a radio frequency operation according to a normalized frequency offset in a preset duration after a radio frequency module is started if the radio frequency operation is carried out; wherein the normalized frequency offset is obtained by dividing a historical carrier frequency by a historical carrier frequency offset value, the historical carrier frequency offset value is a carrier frequency offset value obtained by carrying out carrier frequency offset measurement on a first subframe within a preset duration after the historical radio frequency module is started, and the historical carrier frequency is the carrier frequency of the historical radio frequency module; the radio frequency parameter of the historical radio frequency module is the same as the radio frequency parameter of the radio frequency module; and performing frequency offset compensation on subframes except the first subframe in the radio frequency operation according to a preset automatic frequency control method. In this way, the first subframe of the radio frequency operation can be effectively compensated, so that the residual carrier frequency offset of the first subframe is significantly reduced.

The invention provides an optical single-sideband frequency shift generation device and method with an ultrahigh rejection ratio, and the device comprises an optical frequency shift unit, an optical sideband phase modulation interference unit and a control unit, and employs an orthogonal Mach-Zehnder modulation structure to achieve the optical sideband frequency shift of 1.5 [mu] m waveband light waves. The optical signal after frequency shift contains a residual carrier and a residual sideband, and enters an optical sideband phase modulation interference unit at the moment. The optical sideband phase modulation interference unit adopts a two-stage phase modulation structure to respectively realize cancellation suppression of odd and even sidebands, the first stage adopts an optical fiber phase shifter and an adjustable optical fiber delay line to suppress an even-order sideband, and the second stage adopts an optical fiber phase shifter and an adjustable optical fiber delay line to suppress an odd-order sideband. And the control unit respectively adjusts the phase change amount of the optical fiber phase shifter and the delay amount of the adjustable optical fiber delay, and finally outputs an optical single side band frequency shift signal with an ultrahigh suppression ratio. According to the invention, the suppression ratio of each sideband of a radio frequency signal in any modulation format can be increased by more than 20dB.

Charge leakage / injection suppression circuitry within a capacitive programmable gain amplifier provides a low-impedance expulsion path for residual carriers within a feedback-path amplifier-mode switch and equalizes a voltage across a critical-leakage-path component of that amplifier-mode switch, reducing charge injection and leakage into an otherwise isolated amplifier input node to yield a low-noise amplifier output.