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

The invention provides a communication link used for a telemetry and telecontrol communication system. An uplink broadcasing and downlink TDMA (time division multiple access) mode is adopted to solve the measurement and control problems of a single ground station for multiple aircrafts. A downlink adopts hybrid spread spectrum BPSK (binary phase shift keying) with multiple stages of adjustable gain for modulation, an uplink adopts coded spread spectrum QPSK (quadrature phase shift keying) with fixed gain for modulation, so that the anti-interference, anti-interception and anti-capturing capacity of a wireless link is improved, and asymmetry of the uplink and the downlink is considered. Both the uplink and the downlink adopt a single-pulse modulation symbol packet transmission mode, a fixed interval is inserted into every two adjacent symbol pulses, and accordingly, the spread spectrum signal capturing, tracking and synchronizing complication of receivers is reduced. Non-coherent demodulation is adopted, a complicated carrier synchronization problem is avoided, and the design and project realization of the receivers are further simplified. The complicated carrier synchronization problem is avoided, and wireless communication between a single ground station device and multiple telecontrol terminal devices is realized.

The invention discloses a method for resisting interception and inference for signals based on quadrinomial weighted fractional Fourier transform of multiple-path variable parameters, relating to the communication technical field and solving the problems of poor interception resistance and poor interference resistance in the existing transmission resistance process of communication signals. The method comprises the following steps: at a transmitting end: digital signals are modulated by a baseband and then are subjected to spread spectrum encoding and quadrinomial weighted fractional Fourier transform under the control of a dynamic encryption parameter alphai and a dynamic encryption vector Vi, and encryption data synthesized by signals in multiple paths are subjected to digital carrier modulation and then are sent to a channel to transmit after D/A conversion and up-conversion; and at a receiving end: the data after down-conversion and A/D sampling is subjected to digital carrier coherent modulation, is decomposed by the signals in multiple paths, is subjected to quadrinomial weighted fractional Fourier transform for m times under the control of the dynamic encryption parameter alphai and dynamic encryption vector Vi, and is modulated by the baseband. The method is suitable for occasions of communication signal transmission.

The invention provides a cylindrical integrated active phased-array antenna. 96 linear radiation arrays are arranged in parallel to form a cylindrical array phase, each linear radiation array includes 8 radiation units and 8 phase shifters, and wave beam scanning in the pitching surface is realized; and each radiation column is connected with a switch array via a T/R assembly, the switch array divides the 96 linear radiation arrays into four groups, and a power amplifier is connected via an circulator. According to the invention, an independent antenna can be used to realize omnidirectional scanning with neither increase of array planes nor addition of mechanical scanning, the complexity and power consumption of an antenna system are reduced, and problems in heat radiation and the like are solved.

The invention provides a code-hopping direct spread communication method and system based on OVSF codes. According to data rate requirements of different users, the OVSF codes of different spreading factors serve as a spreading code block, and a code-hopping pattern is generated under the spreading factors to control hopping of spreading codes, namely, code-hopping direct spread of user data is carried out on the basis of the spreading code block. The method and system meet the rate requirements of different users by the adoption of the OVSF code spreading factors, meanwhile carry out spreading on data signals under the same spreading factor by means of code-hopping, and greatly improve anti-interference performance and an-intercept performance of code-hopping direct spread communication.

The invention relates to the field of optical signal processing in optical communication systems and discloses a method for encoding and decoding optical signals on a raster and structures of an optical encoder and an optical decoder to solve the safety problem of eavesdropping existing in an existing optical communication system. The method and the structures are characterized in that according to the technology, the optical signals are encoded and decoded on the raster based on a wavelength selective switch (WSS) and by combining an optical fiber delay line network, and code word dynamic reconstitution of optical encoding and optical decoding can be achieved. The method and the structures have the advantages that the outstanding advantages that the code word dynamic reconstitution amount of optical encoding and decoding is large, the dynamic change range is large, remote software controllability can be achieved, mobile parts do not exist, reliability is high, the insertion loss is low and the power consumption is low are achieved, so that the interception resisting capability of the optical communication system is greatly improved, and the safe transmission of the optical signals is ensured. The technology can be widely applied to optical information safe transmission in the field of optical communication (optical fiber communication and wireless optical communication).

The invention provides a digital random multi-frequency-point frequency hopping and time hopping signal transmission method and system. The method comprises the steps of 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 and building an IFFT module. Aiming at the problemsthat the dimension of a frequency hopping set is small and the like, an OFDM (Orthogonal Frequency Division Multiplexing)-based digital frequency hopping communication technology is adopted, the dimension of the frequency hopping set is improved in a mode of caching data before subcarrier mapping and then remapping, and the purpose of enhancing the anti-interception performance of a frequency hopping system is achieved.

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.

The invention discloses a long-short code joint spread spectrum system unmanned aerial vehicle data link transmitter. It adopts the two-way signal orthogonal modulation system of short code direct spread signal and long code direct spread signal. The short code modulation information is the time synchronization information guiding the long code acquisition mode, and the long code modulation information is user data information. Compared with the data link of the short-period direct-spread system, the patent of the present invention adopts the long-period pseudo-random sequence spread spectrum, which significantly improves the anti-intercept ability of the UAV link, and also has high degree of digitization, small size, easy debugging, With the advantages of stable and reliable performance, it is suitable for information transmission in a complex electromagnetic environment that requires a high degree of command information security.

The invention discloses signal modulation and demodulation methods and phase hopping modulation and demodulation units. The signal modulation method comprises the steps of 1, generating a phase hopping sequence via a phase hopping sequence generator under the control of a clock reference; and 2, performing corresponding phase shifting on the waveform of each chip in a signal to be modulated underthe control of the phase hopping sequence to acquire a modulated signal, wherein the phase hopping modulation unit comprises a phase shifter and a phase hopping sequence generator; the input end of the phase hopping sequence generator is used for being connected with the clock reference, and used for generating the phase hopping sequence under the control of the clock reference; the input end of the phase shifter is used for receiving the signal to be modulated; the control end of the phase shifter is connected with the output end of the phase hopping sequence generator; and after the phase shifter performs corresponding phase shifting on the waveform of each chip in the signal to be modulated under the control of the phase hopping sequence, the output end of the phase shifter outputs themodulated signal. According to the modulation method provided by the invention, the signal is equivalently subjected to twice PSK modulations, so that the modulated signal is close to noise characteristics, and the anti-detection performance of the signal can be improved.

The invention discloses a high-density differential frequency hopping communication method, which belongs to communication technology. The high-density differential frequency hopping communication method comprises an emitting process and a receiving process, wherein the emitting process comprises serial-to-parallel conversion, the mapping treatment of a differential frequency hopping bit frequency point, the generation of a secondary frequency control word, the generation of a high-density differential frequency hopping frequency control word, and emitting; and the receiving process comprisesreceiving, discrete sampling, the recovery of the secondary frequency control word, frequency-domain waveform output, soft decision, synchronous decision, the serial-to-parallel conversion and data output. In the invention, on the basis of the initial primary secondary word, the secondary frequency word is added to increase the frequency point set density of transmission signals; while a receiving end performs frequency-shifting alignment treatment on the discrete data to remove secondary frequency signals, recover primary frequency signals and restore into the frequency point density of the traditional differential frequency hopping system. Thus, the high-density differential frequency hopping communication method has the characteristics that: the information transmission is safe and reliable; decoding is difficult; the confidentiality and anti-interception capability are high; the frequency point density can be adapted to a system security level according to requirements; and the like.

The present invention provides a target remote positioning system, which belongs to the technical field of radar signal processing, wherein the target remote positioning system is composed of N array elements arranged linearly at equal intervals, wherein N is a positive integer; each array element includes a transmitter part and receiving part. The transmitting part includes a modulated signal generator, a double sideband modulator and a transmitting antenna; the output end of the modulated signal generator is connected with the input end of the double sideband modulator, and the output end of the double sideband modulator is connected with the transmitting antenna. The receiving part includes a receiving antenna, a filter bank and a positioning calculation unit; the filter bank is composed of two narrow-band filters with different passing frequencies; the receiving antenna is connected to the input ends of the two narrow-band filters at the same time, and the two narrow-band filters The output end is simultaneously connected with the input end of the positioning solving unit.

The invention relates to a physical layer anti-interception secure communication method and system. The method is characterized in that modulation and coding for anti-interception security are carriedout on an original information bit stream in a physical layer, and then a plurality of symbol code elements are generated and sent, on one hand, a plurality of symbol code elements have a rateless characteristic in the aspect of encoding, so transmission efficiency of the original information bit stream can be improved, transmission can be carried out close to the capacity of a preset channel between a legal transmitting end and a legal receiving end, and decoding difficulty of an illegal receiving end, namely an illegal eavesdropper, is increased while transmission efficiency is ensured, onthe other hand, as a plurality of symbol code elements are in Gaussian distribution, ultra-Gaussian distribution or sub-Gaussian distribution, an illegal eavesdropper cannot extract specific distribution of a plurality of symbol code elements by using a blind detection method based on a high-order cumulant and the like, so interception resistance and security of a physical layer of a communicationsystem are further improved.