30 results about "Skywave" patented technology

The invention discloses an ionospheric-reflection-based time difference of arrival positioning method for a shortwave radiation source, and belongs to the technical field of shortwave communication. The method comprises the following steps of selecting corresponding receiving sites to acquire found and monitored target signals; locally compressing the target signals, and transmitting the target signals to a master server; estimating propagation channels of the signals received by each receiving site, performing joint positioning error estimation in combination with each time difference of arrival, optimizing a positioning result according to the geographic position distribution of each receiving site and the variation amplitude of ionospheric parameters and the time differences of arrival, and giving a positioning error. According to the method, a conventional shortwave receiving antenna can be utilized, a large direction-finding antenna array is not required, the reflection influence of an ionospheric layer on shortwave sky wave signals is taken into full account, and the time differences of arrival of the signals at different receiving sites through different paths are used for positioning the shortwave radiation source; the method is disclosed according to actual needs, is particularly applied to regions where large antenna arrays cannot be erected, and is practically significant, and manpower and funds can be greatly saved.

An electromagnetic vector sensor (EMVS) system, having a plurality of EMVS devices consisting of a plurality of loop antenna elements spatially orthogonally integrated with and electrically isolated from a plurality of dipole antenna elements, mounted on a rotatably adjustable platform having a true north orientation, including active circuitry residing in antenna housings, and external executing software programs causing the active circuitry in cooperation with the EMVS device and receivers to determine angle of arrival and resolution of incoming wave vectors and polarization of incoming signals and to perform accurate high frequency geolocation signal processing; the programs which perform calibration and antenna element placement determination operations, also cause the system to collect data of known transmitted high frequency skywave signals, and estimate direction of arrival of unknown signals by detecting, resolving and measuring components of an electric field and a magnetic field at a single point.

The invention discloses a sky wave massive MIMO communication method, model and system. A large-scale antenna array is used to build a sky-wave communication base station in the short-wave band, and perform sky-wave massive MIMO communication with user terminals in the coverage area through ionospheric reflection. The sky wave communication base station determines the antenna array spacing according to the highest operating frequency, uses TDD to communicate with user terminals, and uses OFDM or its power efficiency improved modulation method for signal transmission. According to the real-time ionospheric channel characteristics, the sky wave communication base station selects the carrier frequency within the short wave band range, and adaptively selects OFDM modulation parameters and signal frame structure. The Skywave communication base station uses the channel information of each user terminal to perform user scheduling to form a space division user group. Different user groups use different time-frequency resources, and the same user group uses the same time-frequency resource to communicate with the Skywave communication base station. The invention can greatly improve the frequency spectrum and power efficiency, transmission bandwidth and distance, as well as speed and terminal capacity of sky wave communication.

The invention provides a short-wave sky-wave propagation time difference positioning method based on the linear distance difference. The present invention pre-acquires the conversion coefficient of the group path of the short wave emitted by the analog radiation source to the receiving station and the straight-line distance between the analog radiation source and the receiving station, and obtains the average conversion coefficient by taking the average value of the conversion coefficients obtained in advance; receiving the target radiation The short-wave signal of the source, and calculate the time difference data from the target radiation source to each receiving station by the generalized cross-correlation method; calculate the coordinates of the target radiation source according to the average conversion coefficient and the time difference data. The invention adds an ionospheric model to the traditional model, uses the actual time difference or path difference to convert into the straight-line distance difference in the traditional model through the average conversion coefficient, and then uses the traditional direct wave model to locate the target radiation source. The invention improves the positioning accuracy of the radiation source.

The invention discloses a method for simultaneously receiving sky wave and ground wave BVR radar signals. A distance offset method is used for transmitted signals on a sky wave transmitting station and a ground wave transmitting station so that a ground wave radar station on a shore base can simultaneously receive echo signals obtained by signals transmitted by a sky wave radar and a ground wave radar and scattered by a sea surface or a ship or a low altitude flight object. The method is simple and convenient to achieve, distance offset only needs to be conducted on sky wave transmitting signals and ground wave transmitting signals, it is guaranteed that the ocean of the sky wave radar and the ground wave radar or an object echo wave spectrum is within the bandwidth of a receiver filter, and aliasing of the distances and spectrum can not happen. An existing ground wave radar receiving system is used so that the purpose that the two BVR methods of sky wave transmitting and ground wave transmitting can be simultaneously used for detecting the ocean or target can be achieved. The combined detection mode can improve the detection accuracy of ocean surface dynamic parameters such as wind, waves and currents, the detection distance of a high-frequency BVR radar system is increased, and close distance fine detection and long distance ocean surface dynamic element detection are achieved.

A multiuser detector based on iterative message passing algorithm relates to a rapid pseudo code acquisition method and a multiuser detector in marine radio navigation system, which solves the problems of serious sky-wave interference in the marine radio navigation system and difficulty in eliminating the sky-wave interference by conventional method. The detector comprises an interference cancellation structure with serial-parallel sub-groups, wherein signals are divided into a plurality of groups according to power, a parallel interference cancellation structure is adopted within each group, and a serial interference cancellation structure is adopted between the groups. Based on IMPA algorithm, the invention can acquire pseudo codes, which comprises the following steps: representing the constraint relationship of the pseudo code sequence by a factor graph, carrying out soft message iterative computation to obtain maximum a-posteriori estimation and generating a local sequence according to the maximum a-posteriori estimation and the decision condition. The invention shortens the acquisition time of long pseudo codes and effectively improves the acquisition probability, and can be applied in signal detection of satellite navigation, 4D mobile communication system, ultra-wide band system, etc.