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Smart Antenna
Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas and, recently, Multiple-input multiple-output communications, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial signal signatures such as the direction of arrival (DOA) of the signal, and use them to calculate beamforming vectors which are used to track and locate the antenna beam on the mobile/target. Smart antennas should not be confused with reconfigurable antennas, which have similar capabilities but are single element antennas and not antenna arrays. Smart antenna techniques are used notably in acoustic signal processing, track and scan radar, radio astronomy and radio telescopes, and mostly in 3G, cellular systems like W-CDMA, UMTS, and LTE (telecommunication), LTE and 5G-NR. Smart antennas have many functions: DOA estimation, beamforming, interference nulling, and constant modulus preservation. Direction of arrival (DOA) estimation The sma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Antenna Array
Digital antenna array (DAA) is a smart antenna with multi channels digital beamforming, usually by using fast Fourier transform (FFT). The development and practical realization of digital antenna arrays theory started in 1962 under the guidance of Vladimir Varyukhin (USSR). History The history of the DAA was started to emerge as a theory of multichannel analysis in the 1920s.Slyusar V. I. Origins of the Digital Antenna Array Theory.// International Conference on Antenna Theory and Techniques, 24–27 May 2017, Kyiv, Ukraine. – Pp. 199 - 20/ref> In the 1940s this theory evolved to the theory of three-channel antenna analyzers. The implementation of effective signal processing in radars by the end of the 1950s predetermined the use of electronic computers in this field. In 1957, Ben S. Meltont and Leslie F. Bailey published article regarding using algebraic operations for signal processing with the help of electronic circuits or analog computer. Three years after in 1960 th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensor Array
A sensor array is a group of sensors, usually deployed in a certain geometry pattern, used for collecting and processing electromagnetic or acoustic signals. The advantage of using a sensor array over using a single sensor lies in the fact that an array adds new dimensions to the observation, helping to estimate more parameters and improve the estimation performance. For example an array of radio antenna elements used for beamforming can increase antenna gain in the direction of the signal while decreasing the gain in other directions, i.e., increasing signal-to-noise ratio (SNR) by amplifying the signal coherently. Another example of sensor array application is to estimate the direction of arrival of impinging electromagnetic waves. The related processing method is called array signal processing. A third examples includes chemical sensor arrays, which utilize multiple chemical sensors for fingerprint detection in complex mixtures or sensing environments. Application examples of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Israel Defense Forces
The Israel Defense Forces (IDF; , ), alternatively referred to by the Hebrew-language acronym (), is the national military of the State of Israel. It consists of three service branches: the Israeli Ground Forces, the Israeli Air Force, and the Israeli Navy. It is the sole military wing of the Israeli security forces, Israeli security apparatus. The IDF is headed by the Chief of the General Staff (Israel), chief of the general staff, who is subordinate to the Ministry of Defense (Israel), defense minister. On the orders of first prime minister David Ben-Gurion, the IDF was formed on 26 May 1948 and began to operate as a Conscription in Israel, conscript military, drawing its initial recruits from the already-existing paramilitaries of the Yishuv—namely Haganah, the Irgun, and Lehi (militant group), Lehi. It was formed shortly after the Israeli Declaration of Independence and has participated in List of wars involving Israel, every armed conflict involving Israel. In the wak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CEA-909
CEA-909 is the ANSI standard for 8VSB/ATSC smart antennas. The basic concept is that the smart antenna either physically rotates toward the signal, or is stationary, but has elements pointed in different directions and uses only those elements that maximize the received signal. This is accomplished by feedback from the control device, such as a digital-to-analog converter box, telling the smart antenna when the signal is stronger or weaker. Analog televisions generally give instant feedback as the signal gets better or worse as you move the antenna. Digital television antennas can be difficult to aim correctly because of the cliff effect and because of delays in decoding and displaying the signal. Smart antennas remove the burden of positioning the antenna for digital TVs and can make the tuning process easier than it was with analog television. Information from TVP9900 document There are two basic modes of operation for a CEA-909 antenna, mode A and mode B. Mode A allows fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coupon-eligible Converter Box
A coupon-eligible converter box (CECB) was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government. The subsidy program was enacted to provide terrestrial television viewers with an affordable way to continue receiving free digital terrestrial television services after the nation's television service transitioned to digital transmission and analog transmissions ceased. The specification was developed by the National Telecommunications and Information Administration (NTIA), with input from the broadcast and consumer electronics industries as well as public interest groups. History Early proposals In March 2005, United States House Commerce Committee chairman Joe Barton of Texas said he would introduce a bill requiring the transition to digital television "sometime in the spring", saying he wanted analog broadcasting to end on December 31, 2006. Included in his plan was a $400–$500 million subsidy for c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Telecommunications And Information Administration
The National Telecommunications and Information Administration (NTIA) is a bureau of the United States Department of Commerce that serves as the president's principal adviser on telecommunications policies pertaining to the United States' economic and technological advancement and to regulation of the telecommunications industry. Agency goals Among its stated goals are: * Working to ensure that all Americans have affordable phone and cable TV service. * Helping to bring the benefits of advanced telecommunications technologies to millions of Americans in rural and underserved urban areas through its information infrastructure grants. * Providing the hardware that enables public radio and television broadcasters to extend and maintain the reach of their programming. * Advocating competition and liberalization of telecommunications policies around the world. * Participating in international government-to-government negotiations to open markets for U.S. companies. * Negotiati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
McGraw-Hill Professional
McGraw Hill is an American education science company that provides educational content, software, and services for students and educators across various levels—from K-12 to higher education and professional settings. They produce textbooks, digital learning tools, and adaptive technology to enhance learning experiences and outcomes. It is one of the "big three" educational publishers along with Houghton Mifflin Harcourt and Pearson Education. McGraw Hill also publishes reference and trade publications for the medical, business, and engineering professions. Formerly a division of The McGraw Hill Companies (later renamed McGraw Hill Financial, now S&P Global), McGraw Hill Education was divested and acquired by Apollo Global Management in March 2013 for $2.4 billion in cash. McGraw Hill was sold in 2021 to Platinum Equity for $4.5 billion. History McGraw Hill was founded in 1888, when James H. McGraw, co-founder of McGraw Hill, purchased the ''American Journal of Railwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast Fourier Transform
A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). A Fourier transform converts a signal from its original domain (often time or space) to a representation in the frequency domain and vice versa. The DFT is obtained by decomposing a sequence of values into components of different frequencies. This operation is useful in many fields, but computing it directly from the definition is often too slow to be practical. An FFT rapidly computes such transformations by Matrix decomposition, factorizing the DFT matrix into a product of Sparse matrix, sparse (mostly zero) factors. As a result, it manages to reduce the Computational complexity theory, complexity of computing the DFT from O(n^2), which arises if one simply applies the definition of DFT, to O(n \log n), where is the data size. The difference in speed can be enormous, especially for long data sets where may be in the thousands or millions. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Least Mean Squares
Least mean squares (LMS) algorithms are a class of adaptive filter used to mimic a desired filter by finding the filter coefficients that relate to producing the least mean square of the error signal (difference between the desired and the actual signal). It is a stochastic gradient descent method in that the filter is only adapted based on the error at the current time. It was invented in 1960 by Stanford University professor Bernard Widrow and his first Ph.D. student, Ted Hoff, based on their research in single-layer neural networks ( ADALINE). Specifically, they used gradient descent to train ADALINE to recognize patterns, and called the algorithm " delta rule". They then applied the rule to filters, resulting in the LMS algorithm. Problem formulation The picture shows the various parts of the filter. x is the input signal, which is then transformed by an unknown filter h that we wish to match using \hat h. The output from the unknown filter is y, which is then interfere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steepest Descent
Gradient descent is a method for unconstrained mathematical optimization. It is a :First order methods, first-order Iterative algorithm, iterative algorithm for minimizing a differentiable function, differentiable multivariate function. The idea is to take repeated steps in the opposite direction of the gradient (or approximate gradient) of the function at the current point, because this is the direction of steepest descent. Conversely, stepping in the direction of the gradient will lead to a trajectory that maximizes that function; the procedure is then known as ''gradient ascent''. It is particularly useful in machine learning for minimizing the cost or loss function. Gradient descent should not be confused with Local search (optimization), local search algorithms, although both are Iterative method, iterative methods for Global optimization, optimization. Gradient descent is generally attributed to Augustin-Louis Cauchy, who first suggested it in 1847. Jacques Hadamard indepe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minimum Mean Square Error
In statistics and signal processing, a minimum mean square error (MMSE) estimator is an estimation method which minimizes the mean square error (MSE), which is a common measure of estimator quality, of the fitted values of a dependent variable. In the Bayesian setting, the term MMSE more specifically refers to estimation with quadratic loss function. In such case, the MMSE estimator is given by the posterior mean of the parameter to be estimated. Since the posterior mean is cumbersome to calculate, the form of the MMSE estimator is usually constrained to be within a certain class of functions. Linear MMSE estimators are a popular choice since they are easy to use, easy to calculate, and very versatile. It has given rise to many popular estimators such as the Wiener–Kolmogorov filter and Kalman filter. Motivation The term MMSE more specifically refers to estimation in a Bayesian setting with quadratic cost function. The basic idea behind the Bayesian approach to estimation st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
