Abstract: A method and apparatus for remotely calibrating a system having a plurality of N elements, such as a phased array system, is provided. The method includes generating coherent signals, such as a calibration signal and a reference signal having a predetermined spectral relationship between one another. The calibration signal which is applied to each respective one of the plurality of N elements can be orthogonally encoded based on the entries of a predetermined invertible encoding matrix, such as a binary Hadamard matrix, to generate first and second sets of orthogonally encoded signals. The first and second sets of orthogonally encoded signals and the reference signal are transmitted to a remote location. The transmitted first and second sets of orthogonally encoded signals are coherently detected at the remote location.

Abstract: A small target phased array Doppler detection system receives signals from remote moving targets and determines Doppler frequency shift and the respective powers of coherent electromagnetic signals for the purpose of detection and identification of relatively small, slow moving targets in the presence of scattering echoes due to clutter. The system employs covariance analysis of the received signals followed by eigenanalysis to produce eigenvectors and eigenvalues. A superresolution algorithm creates dwell manifold vectors which indicate velocities of targets from the eigenvectors. The relative power of radar echoes contribute information relevant to the identification of real moving targets as opposed to false alarms.

Abstract: A phased array source identification receives signals from remote sources and determines direction of arrival angles and the respective powers of coherent electromagnetic signals for the purpose of spatial localization and identification of relatively low power coherent sources in the presence of other coherent sources of relatively large signal power. The system employs covariant analysis of the received signals followed by eigenanalysis to produce eigenvectors and eigenvalues. A superresolution algorithm creates array manifold vectors corresponding to source direction of arrival, that lie in the signal subspace of the eigenvectors. In radar applications low power sources correspond to targets, while the high power sources would correspond to jammers. The relative power of radar echoes contribute information relevant to the identification of real sources as opposed to false alarms. Other applications may include cellular telephone systems and sonar systems.

Abstract: Parallel architectures preprocesses large matrices from sampled coherent time apertures receiving signals from distant sources to produce lower order matrices, derived from pseudo coherent time apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent time apertures, each corresponding to different subbands of the temporal frequency spectrum. The signals representing the pseudo coherent time apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms to produce an image of the sources.

Abstract: Parallel architectures preprocesses large matrices from sampled coherent time apertures receiving signals from distant sources to produce lower order matrices, derived from pseudo coherent time apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent time apertures, each corresponding to different subbands of the temporal frequency spectrum. The signals representing the pseudo coherent time apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms to produce an image of the sources.

Abstract: Parallel architectures preprocesses large matrices from digital phased array systems, receiving signals from distant sources, to produce lower order matrices, called pseudo coherent apertures, which are computationally less burdensome. The large matrices are processed by frequency shifting, low pass filtering with an FIR filter, and executing front-end decimation to create the pseudo coherent apertures, each corresponding to different sectors of the spatial frequency spectrum. The pseudo coherent apertures are processed using matrix based superresolution spectral estimation algorithms such as the Tufts-Kumaresan (T-K) reduced rank modified covariance algorithm and the Linear Minimum Free Energy algorithms produce an image of the sources.

Abstract: A method for rapidly estimating power spectral density components .rho.(f) in the spectrum of an input signal, by first digitizing the input signal over a selected time interval at a selected sample rate; computing an m-th order prediction error energy as an arithmetic mean of forward and backward prediction error energies; and then computing an m-th order prediction error power from a previous reflection coefficient .GAMMA. computation. A control parameter .alpha. is generated; using .alpha. and .GAMMA., an m-th order entropy H and free energy F are then computed, from which is computed m-th order reflection coefficients as extremes of the m-th order Free energy. If the proper extremes are not found, new feedback for the (m+1)-st order solution is generated. If the proper extremes are found, the spectral components are computed and recorded.

Abstract: A method for rapidly estimating power spectral density components in the spectrum of an input signal, by digitizing the input signal over a selected time interval at a selected sample rate; and estimating an autocorrelation sequence for the digitized input signal before generating a solution b.sub.s.sup.0 to the autocorrelation sequence in a Yule-Walker equation by use of Levinson recursion. After generating a control parameter (temperature) .alpha., a non-linear MFE equation, ##EQU1## is solved with b.sub.s.sup.0 as an initial solution. Then, power spectral density components ##EQU2## are generated and recorded as estimates of the input signal.

Abstract: A two-input crosstalk-resistant adaptive noise canceller receives a primary input signal including a desired speech signal portion and an undesired noise signal portion and also receives a reference input signal having a reference noise input portion and a crosstalk speech portion. The canceller has first and second summer means and first and second adaptive filter means. The first summer means provides a canceller output signal which is the difference between the primary input signal and the first adaptive filter output signal. The canceller output signal is applied to the reference input of the second adaptive filter and to one of a pair of error-control inputs of the first adaptive filter. The second error-control input of the first adaptive filter is provided by the signal at the output of the second adaptive filter, which receives a single error-control input signal from the output of the second summer means.

Abstract: The efficacy of a high-pressure sodium lamp is increased significantly by enlarging the arc tube diameter and deploying a composite infrared-reflective film on the interior of the outer lamp envelope. The infrared-reflective film acts to maintain the wall temperature of the enlarged arc tube at the same optimum temperature as the arc tube wall in a conventional high-pressure sodium lamp. In one embodiment, the IR reflective film is a multi-layer composite film of In.sub.2 O.sub.3 :Sn or SnO.sub.2 :F overcoated with a TiO.sub.2 or SiO.sub.2 dielectric film. In another embodiment, a three-layer composite film is made up of TiO.sub.2, In.sub.2 O.sub.3 :Sn, or SnO.sub.2 :F, and SiO.sub.2 films sequentially overlaid on the outer envelope. The dielectric films improve lamp efficacy and enhance the high temperature chemical stability of In.sub.2 O.sub.3 :Sn and SnO.sub.2 :F.

Abstract: A high intensity discharge lamp is provided with means for reflecting infrared radiation from the hot central portion of the arc tube onto the cooler end portions of the tube. The infrared reflective means may be provided by one or more infrared reflecting shields surrounding a portion of the arc tube or by an indentation in the outer glass envelope of the lamp.

Abstract: An improved transparent laminar structure useful as a window in a solar collector having an absorber characterized with a low absorption/emission ratio is described. The structure includes a glass substrate, a particularly defined infrared-reflecting (IRR) layer provided on a major surface of the substrate, and a solar reflection-reducing layer of polymethacrylate composition provided on the IRR layer. Also described are an improved solar collector and method for collecting solar radiation, wherein the laminar structure is employed.

Abstract: Composite high intensity discharge lamp constructions are described adapted for use in the recovery, in the form of heat, of energy in the non-visible frequencies emitted by such lamps. A transparent sleeve is disposed around and spaced from the lamp body being directly or indirectly connected thereto. Air passing between the sleeve and the lamp is brought into intimate heat transfer contact with both the outer surface of the lamp outer envelope and the inner surface of the sleeve.

Abstract: A layer of zinc oxide disposed on the surface of a substrate in thicknesses of between 500 and 10,000 Angstroms is characterized by a sharp absorption edge to substantially absorb selected wavelengths of radiation incident thereon while transmitting other selected wavelengths. The wavelength of the absorption edge is selectable as a function of temperature. A method of depositing the zinc oxide layer is also described.