40 results about "Quadratic nonlinearity" patented technology

Provided is a method for estimating carrier wave or doppler frequency offset based on an approximated quadratic non-linear function in fine search, and a receiver employing the method. The method for estimating frequency offset includes the steps of: a) extracting more than three discrete samples in an order where the discrete samples are close to a maximum value of a power spectrum density function; b) inducing a quadratic non-linear function by using the extracted discrete samples; and c) estimating the frequency offset from a maximum point of the quadratic non-linear function. The technology of the present research makes it possible to exactly estimate frequency offset without increasing hardware complexity in estimation of carrier wave or doppler frequency offset.

The purpose of the present invention is to provide a phase-sensitive optical amplifier device, which can be adapted for optical communication and can provide low noise amplification. A phase-sensitive optical amplifier device according to the present invention is a phase-sensitive optical amplifier device, which amplifies signal light by optical mixing using nonlinear optical effect, comprising a first second-order nonlinear optical element (602-1) and a second second-order nonlinear optical element (602-2). The first second-order nonlinear optical element (602-1) generates from fundamental wave light (621) second harmonic light (622) used as excitation light and is provided with a filter (606-1) that separates only the second harmonic light from the fundamental wave light and the second harmonic light. The second second-order nonlinear optical element (602-2) is provided with a multiplexer (606-2) that mixes the signal light and the second harmonic light, performs parametric amplification using the multiplexed signal light and second harmonic light, and is provided with a filter (606-3) that separates only the amplified signal light from the second harmonic light and the amplified signal light.

A pulse compressor for compressing many-cycle femtosecond-duration high-energy pulses to near-single-cycle durations uses a single quadratic nonlinear crystal. A pulsed laser beam is controlled and its passage is aligned through the quadratic nonlinear crystal such that the detrimental effects of group-velocity mismatch are avoided, while still allowing enough nonlinear phase accumulation for compression to near-single-cycle pulse durations. To do so, the perturbation to nonlinear Schrödinger-type soliton compression due to group-velocity mismatch is minimized which requires that the soliton order must not exceed an optimal value set by the amount of group-velocity mismatch.

The invention relates to a visual saliency detection method with fusion of region color and HoG (histogram of oriented gradient) features. At present, the existing method is generally based on a pure calculation model of the region color feature and is insensitive to salient difference of texture. The method disclosed by the invention comprises the following steps of: firstly calculating a color saliency value of each pixel by analyzing color contrast and distribution feature of a superpixel region on a CIELAB (CIE 1976 L*, a*, b*) space color component diagram of an original image; then extracting an HoG-based local rectangular region texture feature on an RGB (red, green and blue) space color component diagram of the original image, and calculating a texture saliency value of each pixel by analyzing texture contrast and distribution feature of a local rectangular region; and finally fusing the color saliency value and the texture saliency value of each pixel into a final saliency value of the pixel by adopting a secondary non-linear fusion method. According to the method disclosed by the invention, a full-resolution saliency image which is in line with sense of sight of human eyes can be obtained, and the distinguishing capability against a saliency object is further stronger.

The invention relates to the field of video image processing and provides a bit rate control method for video compression. The method comprises the following steps: A. image features are analyzed, andimage feature complexity factors are calculated; B. the number of target bits which are needed to be distributed to an image is calculated; and C. quantization parameters of codes are obtained by a rate distortion model and combining the number of target bits needed to be distributed to the image. In the invention, the bit rate distribution and the image feature complexity are closely combined, and the quantization parameters Q p of codes are obtained by a secondary non-linear rate distortion model, thereby increasing the bit rate control accuracy and improving the image quality.

The invention discloses a power distribution network state estimation method based on an event trigger transmission mechanism and hybrid measurement. The method comprises the steps of firstly obtaining the measurement in a power distribution network, then referring to the prediction feedback returned by a recursion filter, screening the measurement through the event trigger transmission mechanism,and transmitting the data meeting a trigger condition to an estimation center; after the estimation center obtains the data, carrying out filtering estimation under the conditions of simplifying hybrid measurement and considering non-triggering errors; when the filtering gain is solved, converting high-order nonlinear voltage amplitude measurement into an error-bounded quadratic nonlinear form, and designing an uncertainty term linear transformation method of a second-order nonlinear function ; solving a filtering gain when the upper bound of the covariance of the filtering error is minimum;and finally, estimating the state of the power distribution network. According to the method provided by the invention, the calculation process is greatly simplified and the calculation time is shortened on the premise of ensuring the estimation performance.