64results about How to "Improve anti-intercept performance" patented technology

The present invention uses discrete multicarrier spread spectrum, direct sequential spread spectrum and inverse dicrete Fourier transformation to form a two-dimensional spread spectrum module, and the two-dimensional spread spectrum module, frequency hopping and time hopping spread spectrum are used to form the emission part of the united extending spectrum communication method. The inverse discrete multicarrier, direct sequential despreading spectrum and discrete Fourier transformation are used to form a two-dimensional despreading spectrum module and two-dimensional despreading spectrum module, time dehopping and frequency dehopping unit are used to form the receiving part of the united extending spectrum communication method.

The invention relates to a method and a system for generating instantaneous broadband multi-frequency composite radar signals based on engineering implementation. For the carrier signal from the radar carrier source, the design is carried out from the aspects of frequency and broadband. Instantaneous multi-frequency carrier signals to obtain flexible and diverse broadband LPI signals with low signal-to-noise ratio, that is, composite radar transmission signals, overcoming the ultra-high-speed AD sampling, large-capacity data transmission network, and high-speed digital signal processor brought about by engineering implementation. Due to the limitation of hardware resources, the obtained composite radar transmission signal is used in practical projects, and the signal-to-noise ratio (SNR) of the wideband signal is high, which can effectively improve the anti-jamming and anti-interception performance of the radar.

The invention relates to a method for enhancing physical layer security of a free space optical network, comprising: S1, sending a data signal by a legitimate user Alice of the sender, and an interference module sending an interference signal according to channel state estimation; S2, interfering with the data signal and the interference according to different data symbols The signal is modulated by a modulator; S3, using different encoders to encode the modulated data signal and the optical signal of the interference signal; S4, using a coupler to couple the encoded data signal and interference signal to the atmospheric turbulence channel Transmission; S5. The legal user Bob at the receiving end uses the decoder to perform matching decoding on the received optical signal; S6. Uses the photoelectric detector APD to perform photoelectric detection on the signal; S7. The legal user uses the demodulator to perform photoelectric detection on the signal Perform demodulation to obtain the data signal sent by the sender Alice. Therefore, the safety of the FSO transmission system is improved.

The present invention proposes a digital random multi-frequency-point frequency-hopping time-hopping signal transmission method and system, including sampling N-bit signals, building an N-point FFT module, building a frequency-hopping pattern generation module, building a data cache module, building a subcarrier mapping module, Build the IFFT module. Aiming at the small dimension of the frequency hopping set, OFDM-based digital frequency hopping communication technology is adopted to increase the dimension of the frequency hopping set by caching data before subcarrier mapping and then mapping, so as to achieve the goal of enhancing the anti-intercept performance of the frequency hopping system Purpose.

The invention provides a double side band frequency diversity array radar system and an object positioning method thereof and belongs to the technical field of radar signal processing. The double side band frequency diversity array radar system consists of N array elements that are linearly and uniformly arranged at an interval, N is a positive integer, and each array element comprises an emitting part and a receiving part. The emitting part comprises a modulation signal generator, a double side band modulator and an emitting antenna, wherein an output end of the modulation signal generator is connected with an input end of the double side band modulator, and an output end of the double side band modulator is connected with the emitting antenna. The receiving part comprises a receiving antenna, a filter group and a positioning calculation unit, wherein the filter group consists of two narrow band filters that are different in frequency, the receiving antenna is connected with input ends of the two narrow band filters, and output ends of the two narrow band filters are connected with an input end of the positioning calculation unit.

The invention belongs to the technical field of wireless communication, and in particular relates to a group index OFDM communication method based on the combination of message and random sequence. The principle of packet SIM-OFDM communication technology based on the combination of random sequence and message is to use the combination of message drive and random sequence drive to activate some subcarriers of each carrier block in each OFDM symbol to transmit modulation symbols, and other subcarriers remain silent. State, the group index OFDM communication technology based on the combination of message and random sequence uses the randomness of a PN sequence to cause the relationship between index bits and active carrier distribution to also change randomly, making the index bit information more concealed. In the joint driving mode of PN sequence and index bit, without sacrificing the spectral efficiency of the system, the anti-interception performance of the system is greatly improved without reducing the anti-interference performance.

The invention relates to a difference frequency hopping communication method based on the correlation capture of an m sequence, belonging to the field of digital communication and comprising the following steps: setting m sequence data, deserializing, carrying out G functional mapping, generating a baseband frequency wave form, and carrying out intermediate frequency filtering and emission processing in the launch flow; receiving and processing signals, generating the baseband frequency wave form, carrying discrete acquisition, carrying out time / frequency signal transformation, decoding, carrying out correlation processing, judging capture, separating data, carrying out serial conversion processing, and outputting in the receiving flow. The invention has the characteristics of effective capture probability enhancement, false alarm rate reduction, capture time shortening, effective intercept resistance and anti-interference performance enhancement of a system and the like because the invention firstly transmits the m sequence data inserted with random numbers in a uniformly spaced mode and carrying out the G functional mapping processing of the m sequence data and serial Bit data on a transmitting terminal, and eliminates the random numbers through Viterbi decoding and carries out the correlation capture processing on the m sequence after time / frequency signal conversion on a receiving terminal.