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Controlled Reception Pattern Antenna
Controlled reception pattern antennas (CRPA) are active antennas that are designed to resist radio jamming and spoofing. They are used in navigation applications to resist GPS spoofing attacks. Background CRPAs are active antenna arrays composed of multiple antenna elements, typically arranged in a compact configuration. Unlike traditional omnidirectional antennas, which receive signals equally from all directions, CRPAs use sophisticated signal processing techniques to create a directional reception pattern. This allows the antenna to focus on legitimate signals (e.g., GPS satellite signals) while nullifying or attenuating interfering or malicious signals, such as those from jammers or spoofers. The primary function of a CRPA is to mitigate various types of threats: * GPS jamming: Deliberate transmission of high-power radio signals to disrupt or block GPS signals. * Spoofing: Transmission of counterfeit GPS signals to deceive a receiver into calculating an incorrect posit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Active Antenna
An active antenna is an antenna that contains active electronic components such as transistors, as opposed to most antennas which only consist of passive components such as metal rods, capacitors and inductors. Active antenna designs allow antennas of limited size to have a wider frequency range (bandwidth) than passive antennas, and are primarily used in situations where a larger passive antenna is either impractical, such as inside a portable radio or on a vehicle, or impossible, such as in a suburban residential area with restrictions on large outdoor antennas. Most active antennas consist of a short conventional antenna, such as a small whip antenna, connected to an active component (usually a FET). The active circuit compensates for the signal attenuation caused by the mismatch between antenna size and signal wavelength. The active circuit consists of an impedance translating stage and an optional amplification stage. This arrangement is especially useful for constructing low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space-time Adaptive Processing
Space-time adaptive processing (STAP) is a digital signal processing, signal processing technique most commonly used in radar systems. It involves adaptive array processing algorithms to aid in target detection. Radar signal processing benefits from STAP in areas where interference is a problem (i.e. ground clutter (radar), clutter, radar jamming, jamming, etc.). Through careful application of STAP, it is possible to achieve order-of-magnitude sensitivity improvements in target detection. STAP involves a two-dimensional digital filter, filtering technique using a phased-array antenna with multiple spatial channels. Coupling multiple spatial channels with Pulse-doppler radar, pulse-Doppler waveforms lends to the name "space-time." Applying the statistics of the interference environment, an adaptive STAP weight vector is formed. This weight vector is applied to the Coherence (physics), coherent samples received by the radar. History The theory of STAP was first published by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Separation
Source separation, blind signal separation (BSS) or blind source separation, is the separation of a set of source signals from a set of mixed signals, without the aid of information (or with very little information) about the source signals or the mixing process. It is most commonly applied in digital signal processing and involves the analysis of mixtures of signals; the objective is to recover the original component signals from a mixture signal. The classical example of a source separation problem is the cocktail party problem, where a number of people are talking simultaneously in a room (for example, at a cocktail party), and a listener is trying to follow one of the discussions. The human brain can handle this sort of auditory source separation problem, but it is a difficult problem in digital signal processing. This problem is in general highly underdetermined, but useful solutions can be derived under a surprising variety of conditions. Much of the early literature in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GPS Satellites
GPS satellite blocks are the various production generations of the Global Positioning System, Global Positioning System (GPS) used for satellite navigation. The first satellite in the system, Navstar 1, was launched by the United States Air Force on 22 February 1978. The GPS satellite constellation is now operated by the 2nd Navigation Warfare Squadron (2 NWS) of Mission Delta 31, United States Space Force. The GPS satellites circle the Earth at an altitude of about 20,000 km (12,427 miles) and complete two full orbits every day. Satellites by block Block I satellites Rockwell International was awarded a contract in 1974 to build the first eight Block I satellites. In 1978, the contract was extended to build an additional three Block I satellites. Beginning with Navstar 1 in 1978, ten "Block I" GPS satellites were successfully launched. One satellite, "Navstar 7", was lost due to an unsuccessful launch on 18 December 1981. The Block I satellites were launc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Global Navigation Satellite System
A satellite navigation or satnav system is a system that uses satellites to provide autonomous geopositioning. A satellite navigation system with global coverage is termed global navigation satellite system (GNSS). , four global systems are operational: the United States's Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), China's BeiDou Navigation Satellite System (BDS), and the European Union's Galileo. Two regional systems are operational: India's NavIC and Japan's QZSS. '' Satellite-based augmentation systems'' (SBAS), designed to enhance the accuracy of GNSS, include Japan's Quasi-Zenith Satellite System (QZSS), India's GAGAN and the European EGNOS, all of them based on GPS. Previous iterations of the BeiDou navigation system and the present Indian Regional Navigation Satellite System (IRNSS), operationally known as NavIC, are examples of stand-alone operating regional navigation satellite systems (RNSS). Satellite navigation de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal Processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, Scalar potential, potential fields, Seismic tomography, seismic signals, Altimeter, altimetry processing, and scientific measurements. Signal processing techniques are used to optimize transmissions, Data storage, digital storage efficiency, correcting distorted signals, improve subjective video quality, and to detect or pinpoint components of interest in a measured signal. History According to Alan V. Oppenheim and Ronald W. Schafer, the principles of signal processing can be found in the classical numerical analysis techniques of the 17th century. They further state that the digital refinement of these techniques can be found in the digital control systems of the 1940s and 1950s. In 1948, Claude Shannon wrote the influential paper "A Mathematical Theory of Communication" which was publis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planar Array
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. The individual antennas (called ''elements'') are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase relationship. The radio waves radiated by each individual antenna combine and superpose, adding together ( interfering constructively) to enhance the power radiated in desired directions, and cancelling ( interfering destructively) to reduce the power radiated in other directions. Similarly, when used for receiving, the separate radio frequency currents from the individual antennas combine in the receiver with the correct phase relationship to enhance signals received from the desired directions and cancel signals from undesired directions. More sophisticated array antennas may have multiple transmitter or receiver modules, each connected to a separate a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line-of-sight Propagation
Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves can only travel in a direct visual path from the source to the receiver without obstacles. Electromagnetic transmission includes light emissions traveling in a straight line. The rays or waves may be diffracted, refracted, reflected, or absorbed by the atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles. In contrast to line-of-sight propagation, at low frequency (below approximately 3 MHz) due to diffraction, radio waves can travel as ground waves, which follow the contour of the Earth. This enables AM radio stations to transmit beyond the horizon. Additionally, frequencies in the shortwave bands between approximately 1 and 30 MHz, can be refracted back to Earth by the ionosphere, called skywave or "skip" propagation, thus giving radio transmissions in this range a potentially global reach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Jamming
Radio jamming is the deliberate blocking of or interference with wireless communications.https://apps.fcc.gov/edocs_public/attachmatch/DA-12-347A1.pdf Enforcement Advisory No. 2012-02 FCC Enforcement Advisory Cell Jammers, GPS Jammers, and Other Jamming Devices Consumer Alert: Using or Importing Jammers is Illegal In some cases, jammers work by the transmission of radio signals that disrupt telecommunications by decreasing the signal-to-noise ratio. The concept can be used in wireless data networks to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country. Jamming is usually distinguished from interference that can occur due to device malfunctions or other accidental circumstances. Devices that simply cause interference are regulated differently. Unintentional "jamming" occurs when an operator transmits on a busy frequency without first checking whether it is in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gps Spoofing
In the context of information security, and especially network security, a spoofing attack is a situation in which a person or program successfully identifies as another by falsifying data, to gain an illegitimate advantage. Internet Spoofing and TCP/IP Many of the protocols in the TCP/IP suite do not provide mechanisms for authenticating the source or destination of a message, leaving them vulnerable to spoofing attacks when extra precautions are not taken by applications to verify the identity of the sending or receiving host. IP spoofing and ARP spoofing in particular may be used to leverage man-in-the-middle attacks against hosts on a computer network. Spoofing attacks which take advantage of TCP/IP suite protocols may be mitigated with the use of firewalls capable of deep packet inspection or by taking measures to verify the identity of the sender or recipient of a message. Domain name spoofing The term 'Domain name spoofing' (or simply though less accurately, 'Domain s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GPS Jamming
GPS jamming is an act of overwhelming satellite navigation receivers with powerful radio signals that drown out the signals from GPS satellites, rendering the receiver unable to calculate its position or time accurately. Such jamming can disrupt various GPS-dependent devices, from vehicle and aircraft navigation systems to precision agriculture and mobile phone networks. In civil aviation, GPS jamming can disrupt ADS-B transmission. GPS jamming is a particular type of GNSS interference. Under ITU rules, countries are obliged to eliminate harmful interference through GPS jamming and spoofing, but the ITU lacks effective enforcement measures. The ICAO legal framework requires that countries should implement appropriate prevention and mitigation of GPS jamming and spoofing. Under the ICAO's Montreal Convention, countries shall make GPS jamming and spoofing punishable. In the United States, the operation, marketing, or sale of any GPS jamming equipment is prohibited under federal la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
