52results about How to "Avoid quantization error" patented technology

The invention discloses a fast optimized deep hash image coding method and a target image retrieval method. Based on a greedy strategy, a hash image coding model is established for a large image data set, and all images are generated through the optimized deep hash coding network binary code of . When performing target image retrieval, similar images of the same type to the query image can be quickly obtained by calculating the Hamming distance between the query image code and the database image code. The method of the present invention combines the neural network to better solve the problems of gradient disappearance and quantization error, and the coding performance is better; the training process of the deep network is completed with fewer iterations, and the training speed is faster; it can be applied to various systems with discrete constraints problems, and a wider range of applications; further improving the optimization speed of the deep neural network and the retrieval performance of the generated image codes, effectively improving the retrieval accuracy of large image databases.

The invention discloses a coherent demodulation device for a CPT atomic clock, which comprises two paths of modulation and demodulation units, and a digital control circuit and an analog demodulation circuit are adopted to realize high-precision coherent demodulation. A microcontroller is connected with a voltage / current conversion circuit and a frequency synthesis circuit respectively through two paths of digital to analog converters; the microcontroller outputs modulation reference square waves to the voltage / current conversion circuit to realize DC loop modulation; the microcontroller controls frequency synthesis circuit connection to realize microwave loop modulation; the output of the voltage / current conversion circuit and the output of the frequency synthesis circuit are connected with the input end of a VCSEL of a physical system through DC bias devices; photo-signals output by the physical system pass through an optical test amplifying circuit and are connected to a DC demodulation circuit and a microwave demodulation circuit; and demodulation results are respectively input to the microcontroller through an analog to digital converter. The device has the advantages of small volume, low power consumption and high signal to noise ratio. The device-based atomic clock indexes have reached the level of the internationally best commercial small CPT atomic clock.

The invention discloses a system and a method for matched filtering of a spread spectrum signal based on frequency domain processing. In the invention, the spread spectrum signal is sent to a data caching module through an odd-even sequence gating module, data output by the data caching module is sent to a fast Fourier transform module to figure out a frequency spectrum and the frequency spectrum is sent to an odd-even sequence spectrum separation module, and a frequency spectrum of an input digital signal is obtained by an output result through a spectrum synthesis module. The frequency spectrum of the input digital signal is input into a coefficient matching module, and a digital spread spectrum signal autocorrelation result is obtained through multiplication, addition and shift operations with matching coefficients. According to the system and the method, frequency mixing and filtering are realized in a time domain, a quantization error introduced by frequency mixing and filtering during time domain multiplication can be avoided and hardware resources occupied by processing of a high-order filter are reduced.