474 results about "Frequency shifter" patented technology

An antenna device configured to be fed at a feed portion included in a printed board of a radio apparatus is provided. The antenna device has a feed element connected to the feed portion. The antenna device has a first parasitic element at least a portion of which is arranged close and electrically coupled to at least a portion of the feed element. The first parasitic element is loaded with a first frequency shifter. The antenna device has a second parasitic element at least a portion of which is arranged close and electrically coupled to at least a portion of the feed element. The second parasitic element is loaded with a second frequency shifter.

A novel method and apparatus for calibrating DC offsets in a direct conversion receiver. The present DC offset calibration method and apparatus comprises a direct conversion receiver equipped with a frequency shifter means and a DC offset measurement and correction technique. In accordance with the present invention, DC offsets are calibrated in direct conversion receivers through an inventive method including two steps: a DC offset measurement step and a DC offset correction step. In the DC offset measurement step the frequency of a local oscillation signal (typically generated by a voltage-controlled oscillator (VCO)) is shifted by a selected frequency shift value during the inactive time intervals of the receiver. DC offsets are measured while the frequency of the down-conversion oscillation signal is shifted by the frequency shift value. Before the inactive time interval expires, the frequency of the down-conversion oscillator signal is shifted back to its original value. In the DC offset correction step of the present invention incoming signals are corrected using a correction means that removes the DC offset measured during the DC offset measurement step.

A dual-frequency laser ranging method and a device based on polarization state regulation and wavelength synthesis belong to the technical field of laser application. In absolute distance measurement and relative displacement measurement, the method adopts the same frequency stabilized laser as a measuring light source, realizes organic integration of absolute distance measurement and relative displacement dynamic measurement through the control of a polarization rotator and wavelength tuning of acoustooptic frequency shifters and simultaneously meets the requirements on extra long distance precise measurement and fast local displacement ultraprecise monitoring. The device comprises an acoustooptic frequency shifter A and an acoustooptic frequency shifter B, a reflecting mirror A and a reflecting mirror B, a frequency control unit A and a frequency control unit B, a polarization rotator, a polarization splitter B and a laser wavelength split and synthesis unit formed by partial optical splitters. The invention has the advantages of both extra long distance ultraprecise measurement capability and integral formation, etc.

Provided is an optical image measuring apparatus forming a three-dimensional image based on tomographic images of an object, acquired at various depths even when the object moves during measurement. Including a half mirror (6) for dividing a light beam signal light (S) and reference light (R), a frequency shifter (8), a reference mirror (9) and a piezoelectric element (9A) used to change an optical path length of the reference light (R), CCDs (21, 22) for receiving interference light beams (L) resulting from interference light produced by superimposing the signal light (S) and the reference light (R) on each other by the half mirror (6) and outputting detection signals, an image forming portion for forming tomographic images based on the detection signals, a measurement depth calculating means (53), and an image processing portion (57). Forming a three-dimensional image or the like based on the arranged tomographic images.

Provided is an optical image measuring apparatus capable of taking images of an object to be measured in plural depth regions in parallel. An optical image measuring apparatus of the present invention includes: a beam splitter (4) for dividing a light beam into signal light (S) and reference light (R); beam splitters (5-1 to 5-(n−1)) for dividing the reference light (R) into plural reference light beams (R1 to Rn); frequency shifters (6-1 to 6-n) for shifting frequencies of the reference light beams (R-1 to Rn) by different amounts; and reflector plates (7-1 to 7-n) arranged at different distances from an object to be measured (O). The reference light beams (R1 to Rn) and the signal light (S) reflected by the object to be measured in depth regions (D1 to Dn) are superimposed on each other to thereby produce interference light (L). Shutters (9-1 to 9-3) extract interference light components (L1 to Ln) from the reference light (L), and CCD cameras (10-1 to 10-3) receive the interference light component and convert the interference light component into electrical signals to output the signals. A computer (20) forms images in depth regions corresponding to the interference light components based on the electrical signals.

The application provides a low noise fiber laser frequency combs device with controllable carrier envelope phase shift frequency. The low noise fiber laser frequency combs device with controllable carrier envelope phase shift frequency comprises an optical path structure and a circuit structure, wherein the optical path structure comprises an oscillator, an acousto-optic frequency shifter, an optical fiber amplifier, a pulse compressor, an optical fiber spread spectrum device and a coherent heterodyne beat device; and the circuit structure comprises a feed-forward circuit control phase device and a phase-locked loop circuit control repetition frequency device. The fiber laser oscillator can ensure long-time operation of a system, so that the stability of the system is superior to that of a system adopting a solid laser oscillator; through the technologies of optimizing intracavity net dispersion of the fiber oscillator, introducing an inner cavity modulator in the oscillator, adopting the feed-forward acousto-optic frequency shifter, and the like, the low noise fiber laser frequency combs device can be realized; and meanwhile, due to the application of the acousto-optic frequency shifter, the carrier envelope phase shift frequency of the optical frequency combs can be accurately regulated, so that the optical frequency combs device with precise phase position regulation and secular stability is provided for realizing applications such as optical frequency standard, attosecond science and non-linear optics.

Apparatus and methods for fluorescence imaging using radiofrequency multiplexed excitation. One apparatus splits an excitation laser beam into two arms of a Mach-Zehnder interferometer. The light in the first beam is frequency shifted by an acousto-optic deflector, which is driven by a phase-engineered radiofrequency comb designed to minimize peak-to-average power ratio. This RF comb generates multiple deflected optical beams possessing a range of output angles and frequency shifts. The second beam is shifted in frequency using an acousto-optic frequency shifter. After combining at a second beam splitter, the two beams are focused to a line on the sample using a conventional laser scanning microscope lens system. The acousto-optic deflectors frequency-encode the simultaneous excitation of an entire row of pixels, which enables detection and de-multiplexing of fluorescence images using a single photomultiplier tube and digital phase-coherent signal recovery techniques.

A BOTDA system based on pulse coding and coherent detection comprises a narrow linewidth laser device (10), a first polarization-maintaining coupler (11), a second polarization-maintaining coupler (12), a microwave signal source (17), testing optical fibers (18), an optical circulator (19), a 3dB coupler (20), a balance photoelectric detector (21), a scrambler (16), a spectrum analyzer (22) and a digital signal processing unit (23), wherein continuous light emitted by the arrow linewidth laser device (10) is divided into two channels of continuous light, namely, a first channel of the continuous light and a second channel of the continuous light, through the first polarization-maintaining coupler (11); and the system further comprises a frequency shifter (9), a first electrooptical modulator (13), a pulse signal source (14) and a second electrooptical modulator (15). The system adopts a pulse coding technology and a coherent detection method, so that the signal to noise ratio of the BOTDA and the measurement accuracy can be improved, the sensing distance is increased, and the system has the function of breakpoint detection.

The invention provides a speed measurement and distance measurement system and a speed measurement and distance measurement method based on pseudo-random code phase modulation and heterodyne detection. The basic principle is that laser is divided into two parts via a coupler. The majority part is subjected to phase modulation through an electro-optic phase modulator according to a pseudo-random code signal and is transmitted by a telescope as emergent laser; the other part is subjected to frequency shift through an acousto-optic frequency shifter and is used for coherent detection as a local oscillator signal; a laser echo signal and the local oscillator signal are subjected to a coherent action in the coupler, an electric signal is converted through a photoelectric balance detector, and a digital signal is converted through a dual-channel AD acquisition card; the other channel of the dual-channel AD acquisition card acquires a driving signal of the electro-optic phase modulator; and the acquired two ways of signals are subjected to signal processing in a computer. The invention provides a new method of simultaneously acquiring the target speed and the distance information in a high-precision mode.

A BOTDA system that combined optical pulse coding techniques and coherent detection includes a narrow linewidth laser, two polarization-maintaining couplers, microwave generator, two electro-optic modulators (EOMs), fiber under test, an optical circulator, a 3 dB coupler, a polarization scrambler, a pulse generator, a balance photodetector, an electrical spectrum analyzer, digital signal processing unit and a frequency shifter. The optical pulse coding techniques and coherent detection are simultaneously used in the invented system, which can be enhance the signal-to-noise ration (SNR), the measuring accuracy and the sensing distance of BOTDA. Moreover, the proposed system has the capacity of break interrogation.

An interference cancellation device comprises an input for a disturbed signal, a first frequency shifter, a bandpass filter, and a signal combiner. The first frequency shifter shifts the disturbed signal from an original frequency range to a filtering frequency range. The frequency-shifted signal is filtered by the bandpass filter. The filtered signal is supplied to the signal combiner which combines the filtered signal with the disturbed signal to substantially reduce the interference signal that is present in the disturbed signal. A method for interference signal cancellation is also proposed. Furthermore, a computer program product with instructions for the manufacture and a computer program product enabling a processor to carry out the method for interference signal cancellation are also proposed.

The invention discloses a novel method for realizing spectral combination amplification based on the frequency division multiplexing technology, which comprises the following steps of: (a), pre-amplifying and broadening laser pulse generated by an ultra-short pulse oscillator; (b), segmenting the frequency spectrum of a super-continuous broad-band spectrum into multiplex optical pulses with different central wavelengths; (c), amplifying each optical pulse, outputting a part of amplified seed light to a self-reference zero-frequency detection device by using a splitting slice, and taking a beat frequency signal output by the self-reference zero-frequency detection device as the driving frequency of an acousto-optic frequency shifter after filtering and amplifying; (d), coherently synthesizing amplification pulses output by various multi-stage optical fibre amplifiers through a wavelength division multiplexing beam combiner; and (e), carrying out dispersion compensation and pulse width compression of coherently synthesized pulses by using a compressor so as to obtain ultra-short pulse output with high peak power. According to the invention, the frequency division multiplexing technology and the coherent synthesizing technology are organically combined; therefore, the pulse synchronization problem and the spectrum coherent problem in the ultra-short pulse optical fibre laser coherent synthesizing process are solved.

A feedback interferometer of quasi-copath micro-plate laser consists of micro-plate laser; lens and beam splitter set on axle of emission end in sequence; two acousto-optic frequency shifters, light block plate, focusing lens and reference reflector set in sequence on transmission light path of beam splitter; photoelectric detector and two sine signal generators set on reflection light path of beam splitter; reference electric signal generating circuit and two orthogonal phase sensitive detectors.

A local oscillator architecture provides a signal at an output frequency with reduced pulling effect. A voltage controlled oscillator (VCO) generates a first signal having a frequency that is a fraction of the output frequency. A frequency shifter generates a second signal with a frequency substantially equal to the difference between the VCO frequency and the output frequency. Single-sideband mixers are used to produce output signals at the sum of the VCO frequency and the shifted frequency while suppressing an unwanted sideband at the difference of the two frequencies.

The invented Rayleigh windfinding laser radar calibration method uses acoustooptic frequency shift and laser spectrum Doppler broadening principle as basis, and utilizes two acoustooptic frequency shifters whose frequency can be regulated, and makes them be series-connected to implement laser frequency zero-crossed wideband continuous regulation, and utilizes Doppler stretcher to stretch spectrum so as to make accurate and quick calibration of Rayleigh windfinding radar.

An optical image measuring apparatus capable of measuring an object to be measured which includes a birefringent layer in a short time is provided. The optical image measuring apparatus includes a broad-band light source, lenses for increasing a diameter of the light beam, a polarizing plate, a half mirror, a wavelength plate for converting the reference light to circularly polarized light, a wavelength plate for converting the signal light to circularly polarized light and converting the signal light to linearly polarized light, a frequency shifter, a polarization beam splitter for separating an S-polarized light component and a P-polarized light component from interference light, CCDs for receiving the respective polarized light components and outputting detection signals each including intensity change information, and a signal processing portion for forming an image reflecting a birefringent property, of an object to be measured based on the intensity change information.

The invention relates to a method and a system for improving phase stability of a photon microwave signal. The method comprises the following steps that: light output by a laser device is divided into two beams of vertical polarized light by a polarized light beam splitter; a reference light is combined with transmission light via a polarized light beam combiner after frequency-shift, and passes through the polarized light beam splitter after passing through a light micro-wave modulation and a light delay link, finally the reference light is interfered by the transmission light after being rotated and polarized by a faraday rotation mirror, and then a beat frequency signal is detected through a low-speed photodetector; the beat frequency signal is subjected to phase comparison with a 25MHz reference signal to obtain a phase disturbance situation of a transmission system, and the signal output by a phase discriminator is used as a control signal of a microwave photonic phase shifter after being processed. The system comprises a DFB (distributed feedback) laser device, the polarized light beam splitter, an acoustooptic frequency shifter, the polarized light beam combiner, an RF (radio frequency) signal generator, a Mach-Zehnder modulator, the photon microwave signal phase shifter, the polarized light beam splitter, an optical interferometer, a low-frequency optical receiver phase discriminator and a proportion integrator.

The invention discloses a dynamic distributed Brillouin optical fiber sensing device and method. The dynamic distributed Brillouin optical fiber sensing device comprises a narrow linewidth laser, a polarization-maintaining coupler, a coupler, a first electro-optic intensity modulator, a pulse signal generator, a frequency shifter, an optical amplifier, a polarization scrambler, an optical circulator, a polarization controller, a second electro-optic intensity modulator, a microwave signal source, a sensing optical fiber, a 3dB coupler, a balanced photoelectric detector and a data acquisition and processing module. Two technologies including a Brillouin gain spectrum dual-slope frequency point assisted method and a coherent detection technology are adopted at the same time. The coherent detection technology can increase the signal-noise ratio of a system, improve the measurement precision and increases the sensing distance; the Brillouin gain spectrum dual-slope frequency point assisted method solves a problem of influence of optical power fluctuation of a pumping pulse on the measurement precision in a conventional Brillouin gain spectrum slope frequency point assisted method. Therefore, the dynamic distributed Brillouin optical fiber sensing device and method can realize dynamic event measurement with relatively high measurement precision while guaranteeing that the Brillouin optical fiber sensing system has relatively long sensing distance.

Provided is an optical image measuring apparatus capable of effectively obtaining a signal intensity of interference light and phase information thereof by improving detection sensitivity. The optical image measuring apparatus includes a broad-band light source for outputting a light beam whose intensity is periodically modulated, a polarizing plate for converting the light beam to linearly polarized light, a half mirror for dividing the light beam into signal light and reference light and superimposing the signal light and the reference light on each other to produce interference light, a wavelength plate for converting the reference light to circularly polarized light, a frequency shifter for shifting a frequency of the reference light, a reference mirror which is moved by a piezoelectric element, a polarization beam splitter for extracting an S-polarized light component and a P-polarized light component from the interference light, CCDs for detecting the respective polarized light components and outputting detection signals, and a signal processing portion for calculating a signal intensity of the interference light and a phase thereof based on the detection signals. An image of an object to be measured is formed based on a result obtained by calculation.

The invention discloses an optical path structure for a stimulated Brillouin optical fiber gyroscope. A light source emitted by an Erbium-doped narrow-linewidth optical fiber laser is split into two beams to transmit in different paths after passing through a coupler A. One beam of light enters a photonic crystal optical fiber resonant cavity after passing through an all-optical fiber acousto-optic frequency shifter, an optical fiber circulator A, a polarization controller A and a coupler B; and the other beam of light enters the photonic crystal optical fiber resonant cavity after passing through a variable attenuator, an optical fiber circulator B, a polarization controller B and the coupler B. The two beams of light are pump light transmitting anticlockwise and pump light transmitting clockwise respectively. As the wave field of the pump light in a photonic crystal optical fiber and an elastic sound wave field interact to generate stimulated Brillouin scattering, the stimulated Brillouin scattering can be described as periodical modulation of the refractive index of a medium which is caused by the nonlinear interaction performed between pump light waves and Stokes light waves through sound waves that are generated by the electrostriction of the pump light waves.

A tuner comprising a signal input 2 for receiving an input signal comprising multichannel data, a filter 3 having an input coupled to said signal input, the filter being tunable to pass a selected frequency channel, a first frequency changer 8 having an input coupled to an output of said filter 3 and arranged to upconvert the filtered input signal so that said selected frequency channel is shifted to a predefined high intermediate frequency, a second filter 9 having an input coupled to an output of said first mixer 9 and arranged to pass said predefined high intermediate frequency, and a second frequency shifter 12 having an input coupled to an output of said second filter 9 and arranged to downconvert the filtered high intermediate frequency to a predefined output frequency.