91 results about "Autocorrelator" patented technology

Interferometers and autocorrelator based sensors are disclosed that are configured to have multiple sample arms which can be scanned and the backscattered low coherence source light from a sample resolved in a single sweep of one or more variable delays of the sensor. Borescopes and catheters capable of scanning multiple sections or areas of materials and tissues using these sensors are described.

A radar based sensor detection system comprises a microwave source operative to provide a continuous wave signal at an output. A pulse-former is coupled to the output of the source and is operative to provide at an output a variable length pulse that increases the transmitted energy of the radar system according to the range of object detection. A modulator is coupled to the output of the pulse-former for providing a modulated pulse signal when required. A transmit / receive switch coupled to the output of the modulator is selectively operative between a first transmit position and a second receive position. A transmit channel coupled to the transmit / receive switch transmits the pulse signal when the switch is operated in the transmit position. A receiving channel coupled to the transmit / receive switch receives the modulator signal when the switch is operated in the receive position. First and second voltage multipliers each have a local oscillator input for receiving the modulator signal in the receive position, and each have an input signal port, and an output port. A receiver channel receives a reflected transmitted signal from an object and applies the received signal to the receive signal input ports of the voltage multipliers. An autocorrelator coupled to the output ports of the voltage multipliers correlates the received signal to produce an output signal indicating the detection and position of the object.

An autocorrelator apparatus and method for economically measuring physical properties of an object where the measurement path is at least semi-translucent to light, such as thicknesses in multilayered optical structures, group index of refraction, and distance to a surface. The apparatus includes a non-coherent light fiber interferometer and an optional coherent light fiber interferometer in association so as to share PZT fiber modulators. Thickness and boundary extent measurements can be made, for example, of solids, liquids, liquids moving along a horizontal plane, or liquids flowing down a plane.

A frame timing synchronization technique for orthogonal frequency division multiplexing (OFDM) systems is presented. First, a coarse synchronization technique generates a coarse frame timing estimate. The coarse synchronization technique applies a sliding window differentiator to the output of a conventional auto-correlator to mitigate the plateau effect associated with conventional auto-correlation techniques. Second, a fine synchronization technique generates a fine frame timing estimate. The fine synchronization technique uses the coarse frame timing estimate to reduce the number of cross-correlation calculations. Additionally, the fine synchronization technique acquires a fine frame timing estimate based on a signal-to-interference ratio (SIR) metric, which is more robust to multi-paths and pseudo multi-paths caused by cyclic delay diversity (CDD) schemes than conventional cross-correlation synchronization techniques. A fine-tuning technique generates a desired frame timing estimate by searching a first signal path in a searching window around the fine frame timing estimate to further refine frame timing synchronization.

A CW lightwave modulated by a continuously reiterated autocorrelated spectrum-spreading signal is launched into an end of a span of ordinary optical fiber cable. Portions of this lightwave back propagate to the launch end from a continuum of span locations because of innate fiber properties including Rayleigh effects. This is picked off the launch end and heterodyned producing an r.f. beat signal. The beat signal is processed by a plurality (can be thousands) of multifunction despreader, autocorrelator and de-multiplexer units respectively operated in different time delayed relationships to the timing base of launch signal reiteration. This provides r.f. time-domain reflectometry outputs representative of acoustic, or other signals incident upon virtual sensors at positions along the fiber corresponding to the various delay relationships. Material attenuation of undesired noises (e.g., reflections due to presence of couplers in the fiber cable line) is effected by the spectrum spreading and de-spreading.

Advantageous online and / or real-time OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. The apparatus, systems and methods employ a receiver with a bank of parallel branches, with each branch having a self-correlator matched to a different waveform scaling factor. A detection is declared when any of the branches leads to a correlation metric larger than a pre-defined threshold. The branch with the largest metric yields a Doppler scale estimate and a coarse synchronization point. The proposed apparatus, systems and methods use one OFDM preamble, thereby avoiding the need to buffer the whole data packet before data demodulation and enabling online and / or real-time operation. Thus, the disclosed apparatus, systems and methods are advantageously applicable to UWA communications.

Provided are a synchronization apparatus and method for improving timing estimation performance in an OFDM-FDMA / CDMA / TDMA system, which can correctly estimate symbol timing through a more correct timing metric using a guard interval of a preamble. The synchronization apparatus includes an auto-correlator for calculating an auto-correlation value of a received signal and a signal delayed by a predetermined time, a power detector for calculating power of the received signal, a timing metric / normalizer for normalizing the auto-correlation value by dividing the auto-correlation value by the calculated power to obtain a timing metric, and a peak detector for finding a peak value of the timing metric to estimate a frame starting position and an initial symbol timing. The auto-correlator calculates an auto-correlation length as long as a length of a guard interval, considering the preamble characteristic that the patterns are repeated in the time domain. The initial symbol timing is set to a position determined by adding the position where the timing metric has a peak value to the length of the guard interval and subtracting the maximum value of the expected channel delay spread from the result value.

The invention discloses a weak signal detection method based on joint denoising and frequency modulation, and belongs to the technical field of signal processing. The method comprises the steps that 1) partial noise suppressing is carried out on low signal to noise ratio signals which are to be detected and are mixed with noise through an autocorrelator; 2) wavelet threshold transforming is carried out on the signals which are processed in the step of 1) and are to be detected, so as to remove residual noise after signal autocorrelation; 3) a modulatable standard signal is used to modulate the frequency of the signals output in the step of 2), so that the modulated signal frequency can meet the detection condition of a dual Duffing oscillator difference system, and high frequency signals in the modulated signals are filtered out through a low pass filter; 4) the signals output by the low pass filter in step of 3) are input into the dual Duffing oscillator difference detection system, and initial state parameters of the system are set; and 5) whether the dual Duffing oscillator difference detection system has the phenomenon of regular intermittence chaos is judged, and if the phenomenon of regular intermittence chaos occurs, a continuous zero method is used to acquire an intermittence chaos period and the frequency of the signals to be detected. Compared with a traditional detection method, the method can be used to detect the weak signals of any frequency in a background with strong noise, and is of great significance in practical application.

The present invention provides nano particle size measuring method and device with scattered dynamic low-strength laser. The method includes: radiating liquid sample with monochromic laser beam of proper length to produce scattered light signal; collecting and transmitting to light signal with single-modular fiber with gradient refractive index; recording with single-photon counter module the scattered photons and converting into output electric pulse signal; and processing the signal in an autocorrelator. The device includes: light source, polarizer, focusing lens, two-layered refractive index sample matching pool, fiber, single-photon counter module, autocorrelator and computer. The present invention can measure nano particle size fast and accurately.

A frame timing synchronization technique for orthogonal frequency division multiplexing (OFDM) systems is presented. First, a coarse synchronization technique generates a coarse frame timing estimate. The coarse synchronization technique applies a sliding window differentiator to the output of a conventional auto-correlator to mitigate the plateau effect associated with conventional auto-correlation techniques. Second, a fine synchronization technique generates a fine frame timing estimate. The fine synchronization technique uses the coarse frame timing estimate to reduce the number of cross-correlation calculations. Additionally, the fine synchronization technique acquires a fine frame timing estimate based on a signal-to-interference ratio (SIR) metric, which is more robust to multi-paths and pseudo multi-paths caused by cyclic delay diversity (CDD) schemes than conventional cross-correlation synchronization techniques. A fine-tuning technique generates a desired frame timing estimate by searching a first signal path in a searching window around the fine frame timing estimate to further refine frame timing synchronization.

A base station apparatus, communication terminal apparatus, communication system, and communication method are provided that enable the data part transmission amount to be increased, that are resistant to frequency selective fading, and that enable a BS with low transmission loss to be selected. An OFDM transmitting apparatus 100 sets a power measurement pilot as one OFDM symbol in one frame, assigns power measurement pilot subcarrier numbers to base station apparatuses, and transmits a power measurement pilot according to common frame timing among the base station apparatuses, and a communication terminal apparatus 200 is equipped with an autocorrelator 210 that outputs a symbol synchronization signal, an autocorrelator 220 that finds an autocorrelation characteristic of a repeat waveform part that is a repetition of the same waveform having a cycle of ½ effective symbol length or a waveform with the sign reversed having a cycle of ½ effective symbol length from a received power measurement pilot, and an in-phase averaging section 230 that performs in-phase averaging in frame units of an autocorrelation characteristic of the repeat waveform part and detects the positional frame timing of a power measurement pilot on the time axis.

The invention relates to a multifunctional wide-range ultra-short pulsed laser autocorrelator which comprises a precision mobile platform, a first right-angle reflector, a chopper, a second right-angle reflector, a parabolic mirror, a two-photon detector and a signal acquisition system, wherein the first right-angle reflector is fixed on the precision mobile platform and comprises two reflectors; the chopper is positioned at the front end of one reflector in the first right-angle reflector, a first light path is formed between the chopper and one reflector in the first right-angle reflector, and a first beam splitter is placed on the first light path; the second right-angle reflector comprises two reflectors, the second right-angle reflector is positioned at one side of the first light path, and a second light path is formed between the first beam splitter and one reflector in the second right-angle reflector; the parabolic mirror is positioned at the other side of the first light path, a third light path is formed between the parabolic mirror and the other reflector in the second right-angle reflector, a second beam splitter is placed on the third light path, and a fourth light path is formed between the second beam splitter and the other reflector in the first right-angle reflector; the two-photon detector is positioned at one side of the parabolic mirror; and the signal acquisition system is electrically connected with the two-photon detector.

The invention provides an optical path autocorrelator for distributed optical fiber strain sensing measurement, which is formed by sequentially connecting a broad spectrum light source (1), an annular multibeam generator (2), an optical path autocorrelation detecting unit (3), a transmission optical fiber (4) and an optical fiber sensor array (5) end to end; the annular multibeam generator (2) comprises a 2*2 optical fiber coupler (21), a first three-port optical circulator (22), an optical fiber collimator (23) and a movable optical reflector (24); and the optical path autocorrelation detecting unit (3) comprises a second three-port optical circulator (31), an optical detector (32) and an interference signal detecting and processing unit (33). The invention can realize real-time monitoring and measurement of physical quantities, such as multi-point strain or deformation, and the like,solve the problems of overlarge light source power loss and superlow light source utilization ratio when a plurality of sensors are multiplexed in an optical fiber and the problem of measurement precision reduction caused by the existence of light source feedback light and improve the stability of a system.

The invention relates to the technical field of high-precision time delay measurement, in particular to a method and device for measuring optical delay with an optical autocorrelation method. The method for precisely measuring the delay based on optical autocorrelation is provided to solve the problems in the prior art, the time delay smaller than 10 picoseconds can be measured, the largest measuring range is determined by the measuring range of an autocorrelator, and relative measuring precision is superior to 1%. The method and device are achieved through the cooperation of a pulse laser, a first optical fiber coupler, a delay line device, a second optical fiber coupler, the autocorrelator, a processor and the like. The method and device are suitable for the precise measurement of subnanosecond time delay in the optical fiber and free space optical field.

An optical performance monitor (OPM) adapted to (i) sample an autocorrelation function corresponding to an optical signal transmitted in an optical network and (ii) based on the sampling, characterize two or more impairments concurrently present in the optical signal. In one embodiment, the OPM has an optical autocorrelator (OAC) coupled to a signal processor (SP). The OAC receives the optical signal from the network, generates two or more samples of its autocorrelation function, and applies said samples to the SP. The SP processes the samples and generates two or more signal metrics. Based on the signal metrics and reference data corresponding to the impairments, the SP then obtains a measure of each of the impairments.

The invention discloses an autocorrelator for measuring the width of ultra-short laser pulses. The autocorrelator comprises an incidence reference hole, a wedge-shaped spectroscope, a first right-angle reflector, a second right-angle reflector, a scanning device platform, a paraboloidal mirror, a detector and a control device, wherein the incidence reference hole is used for passing to-be-detected lasers which enter horizontally and straightly at equal heights to form an incidence light path; and the wedge-shaped spectroscope is positioned on the incidence light path, and the included angle of the wedge-shaped spectroscope and the incidence light path is 45 degrees. According to the autocorrelator, the wedge-shaped spectroscope is adopted to replace two beam splitting slices in the prior art, and the two sides of each beam slitting slice are parallel to each other, so that a light path structure of the autocorrelator is simple, and interference field signals formed by multiple reflections of two surfaces of the wedge-shaped spectroscope cannot coincide with an emergent light path any more, so that the detector can detect neat autocorrelation signals.

The invention provides a decision method for estimating the frequency deviation of OFDM, which belongs to the technical field of communication and comprises the following steps: setting the correlation length of a short autocorrelator and the correlation length of a long autocorrelator according to the range change of system frequency deviation parameters; operating and working out the peak value of the short autocorrelator and the peak value of the long autocorrelator according to the correlation length of the short autocorrelator and the correlation length of the long autocorrelator; estimating a wide-range frequency deviation estimation gross value according to the peak value of the short autocorrelator; estimating a narrow-range frequency deviation estimation gross value according to the peak value of the long autocorrelator; determining the architecture type and the frequency deviation subsection range of a frequency deviation value determining device; and determining the result of frequency deviation according to the architecture type and the frequency deviation subsection range of the frequency deviation value determining device, the wide-range frequency deviation estimation gross value and the narrow-range frequency deviation estimation gross value. The decision method reduces the operation complexity of a frequency synchronization algorithm.

An optical receiver including an optical divider to divide a signal light from an optical transmission line into two portions, a first and a second dispersion compensators, each dispersion compensator having variable dispersion compensation to compensate chromatic dispersions of each of the two portions of signal light output from the optical divider, and a data demodulator to demodulate a data carried by a signal light output from the first dispersion compensator. The optical receiver further includes an optical autocorrelator to operate on a signal light output from the second dispersion compensator and a controller to control the second dispersion compensator to increase autocorrelation of the optical autocorrelator, and to control the first dispersion compensator according to the result of said controlling the second dispersion compensator.

Provided are an apparatus for estimating frequency offset from received signal and method for the same. The apparatus and method estimates frequency offset precisely without increment of autocorrelator by performing moving average filtering on a noised signal to thereby alleviate jitter. The frequency offset estimating apparatus includes: moving average filter for alleviating jitter of received signal; multiplier for multiplying a filtered signal by conjugate complex operanded pilot signal; phase-rotation value calculator for calculating a phase-rotation value from multiplicand operanded signal by using of symbol delay and an autocorrelation function; frequency offset estimator for estimating frequency offset from the phase-rotation value based on a smoothing function multiplication.

A spectral tissue Doppler processor for an ultrasound system produces Doppler phase shift estimates of sequences of signal samples from a sample volume with a short-lag autocorrelator. The autocorrelation products are summed and an arc tangent taken of each sum to produce angle estimates. The angle estimates, which are proportional to the tissue motion velocity, are plotted, smoothed, and displayed as a spectral tissue Doppler display. The angle estimates are also used to produce the audio Doppler signal which is frequency-adjustable by a user. The spectral Doppler display exhibits good time and velocity resolution for motion which is less than that of blood flow such as myocardial motion. Major causes of blurring, unevenness, and distortion are reduced or eliminated.

The invention discloses a signal source positioning method of a Duffing-Lorenz-based chaotic system. Signal receivers at three different positions form a group of receiving base stations and consist of same auto-correlators and Duffing-Lorenz circuits; before a weak signal is received, the Duffing-Lorenz circuits are adjusted to guarantee that output voltage waveforms of the circuits are chaotic waveforms; when the weak signal is received by the three signal receivers at different times respectively, the signal is denoised by the respective auto-correlator to serve as an input signal to be introduced into the respective Duffing-Lorenz circuits; the change of the voltage waveforms output by the three Duffing-Lorenz circuit circuits from the chaotic waveforms to large periodic waveforms is detected by using the detector and mutant site times t1, t2 and t3 are recorded; the mutant site times t1, t2 and t3 are input into a computer; the position of a signal source is calculated by using the computer. The method has the advantages of high sensitivity, accurate detection and positioning of the weak signal and the like.

The invention provides an integrated optical autocorrelator based on molybdenum selenide double-photon absorption and a measuring method. The integrated optical autocorrelator comprises a substrate, an input waveguide, a splitter, a connection waveguide, a fixed time delayer, an adjustable time delayer, an adjustable time delayer interface, a first connector, a combiner, an output waveguide, a molybdenum selenide thin film, an on-chip electrode, a second connector and a controller. According to the integrated optical autocorrelator, on-chip integration of the optical autocorrelator and measurement of the on-chip pulse width can be realized through a simple structure by employing the double-photon absorption characteristic of a molybdenum selenide material.

The invention provides a laser online sensing device and method for simultaneously measuring turbidity and particle size. The laser online sensing device comprises a laser modulation module, a laser, an optical fiber, an optical fiber circulator, an optical fiber focuser, a photoelectric detector, an amplifying and demodulating circuit, an autocorrelator and a computer, and is characterized as follows: by using full-optical fiber type detecting structures of the optical fiber circulator, the optical fiber focuser and the autocorrelator, using the single laser and the photoelectric detector and using integral light intensity variation and autocorrelation characteristics of backward scattered lights, liquid turbidity and particulate size are simultaneously measured online in narrow spaces at a distance. The laser online sensing device and method for simultaneously measuring the turbidity and the particle size, provided by the invention, have the advantages of simple structure, small size and practicability and are suitable for monitoring the liquid turbidity and the particulate size online under complicated environments.

A multiple optical channel autocorrelator based on an optical fiber circulator includes a broad-band light source, at least an optical-fiber sensor array, an adjustable multiple light beams generator, at least an optical fiber circulator and at least a photoelectric detector. The optical-fiber sensor array is composed of the sensing fibers connected end to end. The online mirrors are formed by the connecting end faces of the adjacent fibers. The adjustable multiple light beams generator includes a fixed arm and an adjustable arm. The optical path difference between the fixed arm and the adjustable arm is adjustable in order to match the optical path of each sensor in the sensor array. The optical fiber circulator couples the signals generated by the multiple light beams generator to the sensor array, and couples the signals returned by the sensor array to the photoelectric detector. The photoelectric detector is connected to the optical fiber circulator. The multiple optical channel autocorrelator based on the optical fiber circulator can implement the real-time online measurement of the physical quantity of multipoint strain or deformation, and has advantages of low light source power loss, high efficiency and good stability.

In a receiver of electromagnetic or other waves, scaling of received frequencies in proportion to the respective source distances, so as to reveal the source distances and permit isolation of signals from a particular source by simple spectral filtering. Phase differences between transmitted frequencies due to the common source path lead to chirp eigenfunctions registering in the receiver as scaled frequencies. The chirps are extracted by implementing exponentially varying path delays in autocorrelators and diffractive spectrometers say using a medium with variable refractive index. Analogous exponentially varying phase shifts are applied to successive samples in the kernel of discrete Fourier transform implementations. Advantage lies in enabling distance-dependent frequency scaling in autocorrelation spectroscopy, as well as in conventional diffractive or refractive spectrometers or digital signal processing with uniform sampling.