34results about How to "Eliminate Phase Noise" patented technology

A method of generating a susceptibility map of an object utilizes a regularizing inverse function, oversampling k-space, removing external phase noise and rapid phase change effects, accounting for the known geometry of the object, and using modified SWI phase data to generate reasonable susceptibility maps and digital images therefrom, such as SWI images. The inventors refers to the inventive methods set forth herein as Susceptibility Weighted Imaging and Mapping (SWIM).

A differential voltage controlled oscillator (VCO) employed in a frequency synthesizer used as a local oscillator of a wireless communication on-chip transmitter / receiver is provided. More particularly, a differential current negative feedback VCO equipped with a current-current negative feedback circuit that suppresses low- and high-frequency noise is provided.A differential current negative feedback VCO includes a resonator determining oscillation frequency, and an oscillator generating negative resistance. In the oscillator of the differential current negative feedback VCO, transistors Q1 and Q2 form a cross-coupled pair, and negative resistance is generated by positive feedback of the cross-coupled pair. And, transistors Q1 and Q3 together with an emitter resistor and a capacitor form a current negative feedback part, and transistors Q2 and Q4 together with an emitter resistor and a capacitor form another current negative feedback part which is disposed opposite to a resonator. Thus, the VCO operates differentially.In the oscillator of the differential current negative feedback VCO, emitter noise currents generated by base noise voltages of Q1 and Q2 induced by low- and high-frequency noise sources in the bases of Q1 and Q2 are sampled by emitter resistors, amplified through bases of Q3 and Q4, and thus return to the bases of the Q1 and Q2 and suppress the base noise voltages. Measurement of the phase noise of the differential current negative feedback VCO reveals a phase noise reduction of approximately 25 dB compared to a conventional differential VCO.

The present invention relates to an apparatus and method for feedforward-type phase noise elimination in a portable terminal, which detect and eliminate phase-reversed phase noise by subtracting a GSM transmission signal, passed through the power amplifier of a GSM transmission device, from a GSM transmission signal, extracted from an upstream stage of the power amplifier, so that phase noise signals attributable to high-power transmission signals.

In one embodiment, the present invention includes a method for digitizing a phase noise value indicative of a level of phase noise present in a LO signal and downconverting an RF signal to a second frequency signal using the LO signal. This downconversion can cause the phase noise to be transferred to the second frequency signal. The method may thus further include removing the phase noise from the second frequency signal using the digitized phase noise value.

The invention provides a multi-modulus frequency divider and an electronic device, which relate to the field of frequency dividing technologies. The multi-modulus frequency divider comprises a frequency division module, wherein the frequency division module comprises N divide-by-2 / 3 frequency divider units which are differentially cascaded, and each divide-by-2 / 3 frequency divider unit is composed of a high-speed differential D trigger based on CMOS logic. Therefore, the multi-modulus frequency divider can operate at a radio frequency and has low power consumption; in addition, the multi-modulus frequency divider comprises a retiming module 13, thus can eliminate phase noise to certain extent. The electronic device adopts the multi-modulus frequency divider, thus has the same advantages as the multi-modulus frequency divider.

Disclosed in the present invention are an optical phase demodulation method and system based on polarization-division receiving. The method comprises: performing I / Q demodulation on optical signals collected by two sensing points, and performing signal polarization-division receiving by using a polarization-division receiving device, and obtaining a corresponding signal component; constructing an optical phase vector according to the corresponding signal component; determining a birefringence phase vector according to the optical phase vector, and normalizing a phase difference; and after the birefringence phase vector is compensated, obtaining a phase change between the two sensing points by means of vector synthesis. According to the present invention, the birefringence phase vector is compensated, so that the influence of polarization fading on signal demodulation is reduced, and the system stability is improved; and an I signal and a Q signal are subjected to orthogonal decomposition, and optical signals are converted into vectors to implement depolarized phase demodulation, so that the birefringence phase difference can be accurately estimated, and the accuracy of signal restoration is improved.

The invention discloses a Brillouin optical time domain analysis system based on Brillouin phase shift demodulation, which is composed of two parts: optical path detection and circuit demodulation; The light is generated by cascade modulation of Mach-Zehnder modulator and phase modulator, the light generated by the first stage modulation is used as the light interacting with the pump, the light generated by the second stage is used as auxiliary light to eliminate phase noise, and the receiving end is coherently detected; The circuit uses envelope detection to demodulate the signal. The system of the invention is simple, easy to implement and easy to adjust; single channel, low sampling rate, less data volume; high Brillouin phase measurement accuracy and high stability can be obtained.

A detection apparatus and method for noise intensity and a coherent optical receiver where the detection method includes: preprocessing a received signal to obtain a pilot sequence contained in the received signal; removing a phase noise of a receiving pilot sequence by using a known transmitting pilot signal; calculating a noise power density of the receiving pilot sequence with no (or without) phase noise within a predetermined spectral width near a pilot frequency; and calculating power of a linear noise of the received signal based on a bandwidth of the received signal and the noise power density within the predetermined spectral width. Hence, linear noises and nonlinear noises may be split efficiently without introducing much complexity, and information on intensities of various noises may be obtained.

The present invention discloses an oudoor field RCS measurement method, which comprises the steps of acquiring at least one group of echo signals, wherein any group of echo signals comprises a target intermediate-frequency (IF) echo signal and a scaling body IF echo signal; for any group of echo signals, conducting the analog-to-digital conversion on the target IF echo signal in the above group of echo signals to generate a first digital signal, conducting the analog-to-digital conversion on the scaling body IF echo signal in the above group of echo signals to generate a second digital signal; conducting the fast Fourier transformation on the first digital signal to obtain a first complex-quantity signal, obtaining a first electric field strength in accordance with the first complex-quantity signal; conducting the fast Fourier transformation on the second digital signal to obtain a second complex-quantity signal, obtaining a second electric field strength in accordance with the second complex-quantity signal; calculating a candidate RCS according to the first electric field strength and the second electric field strength; on the condition that only one group of echo signals is acquired, adopting the candidate RCS as a target RCS. According to the technical scheme of the invention, the phase noise and the attenuation in the oudoor field RCS, caused by the external interference, can be eliminated, so that the RCS measurement error is reduced.

The invention discloses an optical signal receiving device, an optical signal receiving method, and a coherent optical transmission system with the device, relating to the field of coherent optical transmission systems. The optical signal receiving device comprises: a local laser, two polarization beam splitters, two polarization beam combiners, two photodetectors, two analog to digital converters, and a digital signal processing unit, wherein the digital signal processing unit comprises a self-beating frequency noise eliminating module configured to eliminate the influence of the self-beatingfrequency of the signal on the system performance, and a phase noise compensation module configured to eliminate the phase noise of the signal by utilizing the phase noise compensation algorithm. Theinvention is capable of solving the problem of high cost of laser in the existing coherent optical transmission system.

A method for realizing a self-oscillating multi-carrier optical fiber light source and a multi-carrier optical fiber light source system: establish a multi-carrier optical fiber light source based on a cyclic frequency shift loop; amplify the optical signal output by the multi-carrier optical fiber light source in the optical domain; Perform longitudinal mode selection processing in the signal optical domain; convert the optical signal after longitudinal mode selection processing into corresponding electrical signals of different frequencies; perform electrical domain filtering on the electrical signal; perform electrical domain amplification on the filtered electrical signal; The final electrical signal is fed back to the frequency shifter in the cyclic frequency shifting loop of the multi-carrier fiber optic light source, which is used to drive the frequency shifter to control the frequency shift of the optical signal, so that the multi-carrier fiber optic light source outputs an optical signal with a set frequency interval. Part of the above optical signals returns to step 2 for the next cycle, and the other part of the optical signals is used as the multi-carrier output of the entire system. The invention has the characteristics of large output signal carrier coverage, flat power, low phase noise, and no external radio frequency driving source.

The invention discloses an inductor-capacitor (LC) oscillator with basically constant variable capacitance in an oscillation period. The LC oscillator comprises a resonance network consisting of an inductor L and a self-adaptive compensation variable capacitor, a complementary cross-coupling negative resistance amplifier and a bias current source, wherein the variable capacitor is a self-adaptive compensation varactor (AC-Varactor). By dynamically compensating the variable capacitance of the AC-Varactor, variable capacitance variation caused by amplitude variation of output waveform is avoided, and frequency modulation caused by the amplitude variation is avoided, so that phase noise performance deterioration caused by amplitude noise is minimized. The LC oscillator overcomes the defects that in one oscillation period, the variable capacitance can change the oscillation frequency along with the change of voltage at two ends, and the oscillator phase noise performance is decreased by an amplitude modulation to frequency modulation (AM-FM) process; and the LC oscillator with the basically constant variable capacitance in the oscillation period has good phase noise performance and can be widely applied to wireless communication systems.