34results about How to "Eliminate frequency offset" patented technology

This invention discloses a method for eliminating frequency deviation and mobile terminals, in which, the method includes: receiving GPS satellite signals to get time information, estimating the frequency deviation of a voltage-controlled crystal oscillator of the mobile terminal based on the time inforamtion, regulating the deviation voltage of the oscillator of the mobile terminal and utilizing the regulated deviation voltage to control the working frequency of the oscillator. This invention utilizes GPS signals to eliminate deviation of a mobile terminal at the beginning to enable it synchronized with the base station so as to increase probability of success for searching local regions initially.

The invention discloses a self-adapting signal detecting method for eliminating frequency offset interference, which comprises the following steps of: S1 adding a pseudo-random code into a frame head of a data frame as a lead code by a sending end, and sending the sampled data frame; S2 multiplying the received data frame by delay thereof in a conjugating way by a receiving end after receiving the data frame to obtain the received signal which eliminates the frequency offset; S3 dividing the received signal into two same signals, respectively computing a statistical decision quantity and setting a self-adapting threshold; and S4 comparing the magnitude of the statistical decision quantity with the magnitude of the self-adapting threshold, and outputting an identification signal which indicates that an effective signal is detected if the statistical decision quantity is larger than the self-adapting threshold. The method eliminates the frequency offset generated during signal transmission by means of conjugate multiplication, reduces the computation quantity, improves the computation speed, improves the detecting precision of the signal, and is stable in performance, simple in structure, and easy in realization.

The invention relates to a measurement method for OFDM system frequency offset under the high speed environment and an application and a measurement device thereof. The method comprises the followingsteps that S110, a synchronization signal is received; S120, coarse frequency offset deltafcoarse is calculated according to the phase difference of two adjacent segments of sequences of the synchronization signal; S130, pilot frequency is acquired, and the pilot frequency is transformed to the time domain so as to acquire the current signal-to-noise ratio; S140, the signal-to-noise ratio is greater than the threshold S150, the pilot frequency of multiple symbols under the regular time slot is acquired, and measurement of fine frequency offset deltafoffset is performed through repeated correlation of the pilot frequency of multiple symbols; and S160, the target frequency offset deltafall=deltafcoarse + deltafoffset is calculated. According to the measurement method for the OFDM system frequency offset under the high speed environment, the accurate coarse frequency offset is provided and whether the basis of continuing frequency offset measurement is met is judged through the signal-to-noise ratio so that the accuracy of the target frequency offset can be greatly enhanced.

The invention provides a high-stability time base oscillator automatic calibration circuit, which comprises a control system, an FPGA (Field Programmable Gata Array) control unit, a D/A (Digital to Analog) conversion unit and a voltage-stabilizing power supply generating unit, wherein the FPGA control unit is used for detecting the current frequency of a crystal oscillator, and outputting an offset value; the control system is used for performing coarse tuning and high-precision calibration on the frequency of the crystal oscillator; the D/A conversion unit is used for receiving an aging rate DAC (Digital to Analog Conversion) array output by the control system, converting into an analog signal, and outputting EFC (Electrical Frequency Control) voltage to the voltage tuning end of the crystal oscillator; the voltage-stabilizing power supply generating unit comprises a switch voltage-stabilizing power supply and a linear voltage-stabilizing power supply, and is used for outputting reference voltage to the reference end of the D/A conversion unit. According to the high-stability time base oscillator automatic calibration circuit, the dependence on external accurate reference signals and frequency offset caused by the aging rate of the crystal oscillator existing in other calibration methods are eliminated.

The invention discloses a satellite communication antenna based on a quadrifilar helix technology. The satellite communication antenna comprises a cylindrical substrate device with a cross section in a regular polygon shape, wherein a metal antenna circuit is arranged on a surface of the cylindrical substrate device and comprises four groups of spiral arms, the four groups of spiral arms are completely same and are symmetrically and rotatably arranged on a side surface of the axial symmetric cylindrical substrate device, and the four groups of spiral arms are connected by a short-circuit unit when rotating to a top end. With the adoption of a polygonal prism, on one hand, the aperture and the size of a quadrifilar helix antenna are reduced, reliable and stable circular polarization characteristic of the antenna in a working frequency is ensured, and the appearance design flexibility is greatly improved on the basis of ensuring the standard antenna performance; and on the other hand, the short-circuit unit is loaded at the top, a short-circuit point is arranged at a connection part of a lower end, thus, the input impedance is improved, the impedance mismatching caused by excessively small impedance is improved, and the radiation efficiency and the grain of the antenna are improved. The quadrifilar helix technology can be widely applied to various satellite communication antennas.

The invention relates to the technical field of laser, and provides a Fourier mode-locked laser device, which comprises a filtering module, an optical amplifier, a first optical beam splitter, an optical fiber delay line and an optical modulation module which are arranged along an optical path, wherein the filtering module comprises a sweep frequency filter and a filtering control unit, the filtering control unit is connected with the sweep frequency filter, the optical modulation module comprises an optical modulation unit and a modulation control unit, the modulation control unit is connected with the optical modulation unit, the optical modulation unit is used for carrying out frequency shift compensation on an optical signal, and the modulation control unit is used for controlling thefrequency shift amount of the optical modulation unit. According to the invention, the optical modulation unit is accurately and flexibly controlled through the modulation control unit, so that the optical modulation unit can compensate the frequency offset in the laser cavity, so that the frequency offset in the laser cavity can be effectively eliminated so as to improve the coherence of the laser device.

The invention discloses a micro-grid inverter frequency-difference-free control method based on a virtual synchronous machine. The micro-grid inverter frequency-difference-free control method comprises three parts including frequency-difference-free active-reactive power control, reactive power-voltage control and inner loop voltage-current control. In a rotor motion equation, a traditional damping link is replaced with frequency proportional integral feedback, thereby eliminating frequency offset in an isolated-grid mode and enabling the realization of multi-mode control of a micro-grid inverter. Through frequency integral feedback, the steady-state frequency deviation is eliminated; and controller modes do not need to be switched under different operating conditions, thereby being conductive to realizing the multi-mode control and seamless switching of the micro-grid inverter.

The present invention relates to an ultra sensitive in-situ magnetometer system, and more particularly to an ultra sensitive in-situ magnetometer system that can in-situ monitor a magnetic moment of a magnetic thin film with sub-monolayer precision while depositing and growing the magnetic thin film in an ultra high vacuum (UHV) chamber.

The invention discloses a high-precision bistatic linear frequency modulation continuous wave radar synchronization system, and relates to the technical field of radars. The system comprises a first radar subsystem, a second radar subsystem and a scheduling module, the scheduling module uses a wireless transparent transmission module to perform unified control and scheduling on the two radar subsystems, and after each radar is powered on, one radar transmits frequency modulation continuous waves, the other radar receives the frequency modulation continuous waves, the inherent frequency difference of the two radar subsystems can be measured through two echo signals, and the radar systems adjust synchronization signals of the radar systems to achieve approximate alignment of linear frequencymodulation starting moments to eliminate deviation and frequency deviation of the starting moments. Synchronization of the two radar subsystems is achieved, the problem that distance measurement cannot be achieved is solved, and the distance measurement precision is improved.

The invention relates to a method for removing the frequency deviation in the communication system with synchronous head predistortion, which comprises the following steps: (1) removing the frequency deviation of the synchronous head data signal according to the received synchronous head by the terminal; (2) determining the constellation chart rotating angle of the data signal after removing the frequency deviation by observing the constellation chart of the data signal acquired by the procedure (1) and the receiving signal-to-noise ratio of the data signal outputted after the calculation of the terminal; (3) regarding the constellation chart rotating angel of the data signal removed the frequency deviation as the synchronous head predistortion value and configuring the synchronous head predistortion value by the network controller; (4) proceeding with the predistortion process according to the synchronous head predistortion value configured by network controller by the base station; (5) removing the frequency deviation of the synchronous head data signal according to the predistortion synchronous head by the terminal. The method can remove the frequency deviation accurately and effectively in the communication system, which guarantees the normal operation of the system.

The invention discloses an equipment clock calibration method, an equipment clock calibration device, an equipment clock calibration system, a self-calibration method and self-calibration equipment. The equipment clock calibration equipment comprises a TSXO and a WIFI module. The equipment clock calibration method comprises the steps of: eliminating built-in frequency offset of the TSXO by means of the WIFI module; and calibrating the temperature drift of the TSXO. Through adopting the equipment clock calibration method, a clock scheme with a positioning function, which is relatively low in cost and relatively high in precision, can be provided for the universal connection equipment.

The invention discloses a method for eliminating frequency deviation through temperature compensation in a WCDMA frequency selector, wherein frequency deviation is formed due to environmental temperature change in a medium-frequency sound meter, and the N frequency-division coefficient of a phase-locking frequency-doubling circuit is controlled according to a frequency deviation quantity, so thatthe deviation quantity consistent with the medium-frequency sound meter is also generated by the output of a VCO (Voltage Controlled Oscillator) to eliminate the frequency deviation. The invention mainly discloses a device for eliminating the frequency deviation through temperature compensation in the WCDMA frequency selector, which comprises a temperature detection module, a microprocessing module and the phase-locking frequency-doubling circuit, wherein the temperature detection module is used for detecting the environmental temperature of the medium-frequency sound meter, and the microprocessing module is used for outputting a control level according to the frequency deviation quantity generated by temperature and controlling the N frequency-division coefficient in the phase-locking frequency-doubling circuit. The invention eliminates the frequency deviation in the WCDMA frequency selector by using a temperature compensation method and keeps the stability and the good communicationquality of the WCDMA frequency selector.

An LPF eliminates noise components from baseband signal obtained by performing a frequency conversion on the received signal on the basis of the received wireless transmission wave. A passband setting part sets the upper limit of frequency of passband in the LPF at a high frequency while a synchronization signal is not detected and at a low frequency after a synchronization signal is detected.

The invention discloses a method and a device for eliminating frequency offset jump, and belongs to the field of mobile communication. The method comprises the following steps: performing frequency offset estimation on a symbol output by a phase-locked loop by tracking within a first time unit to obtain a first frequency offset estimation value of the first time unit; determining whether or not the frequency offset jump occurs on the symbol output by the phase-locked loop by tracking within the first time unit according to a second frequency offset estimation value of a second time unit and the first frequency offset estimation value of the first time unit, wherein the second time unit is ahead of the first time unit; and if so, eliminating frequency offset generated on the symbol output by the phase-locked loop by tracking within the first time unit by the frequency offset jump according to the first frequency offset estimation value of the first time unit and the second frequency offset estimation value of the second time unit. The device comprises a first acquisition module, a determination module and a first elimination module. Through adoption of the method and device, the frequency offset jump can be eliminated under the situation of not generating interference among users, and the system performance at a base station switching moment is enhanced.

The invention provides a bipolar ultrahigh voltage DC power transmission system, and a control system and method thereof. The control system comprises a first control module used for controlling change of voltages of the DC end of a first high-voltage current transformer among high-voltage current transformers of the bipolar ultrahigh voltage DC power transmission system; and a second control module used for controlling change of voltages of the DC end of a first low-voltage current transformer among low-voltage current transformers of the bipolar ultrahigh voltage DC power transmission system, wherein the first high-voltage current transformer and the first low-voltage current transformer belong to a first pole of the bipolar ultrahigh voltage DC power transmission system, and the change direction of the voltages of the DC end of the first high-voltage current transformer under the control of the first control module is opposite to the change direction of the voltages of the DC end of the first low-voltage current transformer under the control of the second control module. Different power demands of a first AC power network and a second AC power network can be satisfied, and power exchange respectively between the bipolar ultrahigh voltage DC power transmission system and the first AC power network and the second AC power network can be dynamically adjusted.

The invention discloses a magnetic insertion control circuit suitable for a hard label machine and a control method thereof. The control circuit comprises an excitation signal source module, a precision resistor R1, a compensation capacitor unit, a single-coil sensitive probe, a signal processing module and a control unit. The single-coil probe is simple in design structure and convenient to install and debug, and the problem of frequency deviation of a traditional single-coil detection circuit is effectively solved by adopting the design of the compensation capacitor unit. In the process of controlling the magnetic rod to be inserted, when the control unit detects that the digital quantity signal of the AD conversion unit is minimum, the magnetic rod can be stopped being pressed in, the control method is simple, and the circuit and the control method thereof provide technical support for full-automatic production of hard labels.