The invention relates to a method for a radar device arranged above a reflecting surface, whereby the height of an object above said surface can be estimated. The inventive method is implemented without the need for improved angle resolution and is solely based on signal processing. The invention takes advantage of an interference pattern which occurs in the radiation field of the radar antenna and which is generally considered as a drawback. The intensity modulation of a received signal coming from an object inside the monitoring area which is displaced in relation to the radar device is evaluated and considered in conjunction with the measured object distance in order to estimate a value corresponding to the height of the object above the travel path.

Method for processing radar signals

A combined defense and navigational system on a naval vessel is disclosed. The disclosed system includes a track-while-scan pulse radar which is controlled to provide either navigational information or tracking information on selected targets. Additionally, the disclosed system includes a plurality of guided missiles, each of which may be vertically launched and directed toward intercept of a selected target either by commands from the track-while-scan radar or from an active guidance system in each such missile.

Shipboard point defense system and elements therefor

Method and apparatus for using a plurality of correlators to improve an estimate of direct signal arrival time by identifying features of a correlation function at and adjacent to the correlation peak. In a first embodiment, the errors in location of the center point of a correlation function R(τ), formed by the incoming composite signal and a stored copy of the expected signal, are assumed to be strongly correlated for narrow sample spacing and wide sample spacing of the correlation function. In a second embodiment, multipath signal strengths and phases are estimated, using multiple sampling of the correlation function R(τ). This approach assumes that path delays of the direct signal and of the multipath signals can be determined separately. Path delays can be determined by any of at least three approaches: (1) identification of slope transition points in the correlation function; (2) Cepstrum processing of the received signal, using Fourier transform analysis; and (3) use of a grid of time points on the correlation function domain, and identification of time values, associated with certain solution parameters of the least mean squares analysis that have the largest absolute values, as times of arrival of the direct and multipath signals. Separate identification of multipath time delays reduces the least mean squares analysis to a linear problem. A modified signal is constructed, with the multipath signal(s) approximately removed from the incoming composite signal. This modified signal allows a better estimate of the arrival time of the direct signal.

Adaptive multipath equalization

Capability is provided using coherent synthetic aperture radar (SAR) techniques for substantially extending the useful range for producing 3 scaled high resolution orthogonal image projections on a CRT of a translating ship under the influence of rotational motions arising from sea state conditions, for the purpose of ship classification and weapon delivery from an airborne platform at long stand-off ranges. This advantage is brought about by determining image coordinates on the basis of range, doppler, and doppler rate measurements of individual scatterers and from ship angular rotational velocities derived from a weighted multivariate regression solution to doppler processed interferometric azimuth and elevation angle measurements of all significant ship target scatterers. In this manner, the image degradation suffered by plotting angular measurements directly, whose location accuracies are known to deteriorate rapidly with increased range due to high signal-to-noise requirements, is circumvented.

Extended sar imaging capability for ship classification

Method and apparatus for using a plurality of correlators to improve the estimate of direct signal arrival time by identifying detailed features of a correlation function at and adjacent to the correlation peak. The errors in location of the center point of a correlation function R(τ), formed by the received signal and a stored copy of the expected signal, are assumed to be strongly correlated for narrow sample spacing and wide sample spacing of the correlation function. Alternatively, the multipath signal strengths and phases are estimated by a least mean squares analysis, using multiple sampling of a correlation function of an expected signal and an arriving composite signal that includes the direct signal and one or more multipath signals. Times of arrival or path delays of the direct signal and the multipath signals are determined separately. Path delays can be determined by at least three approaches: (1) identification of slope transition points in the correlation function R(τ); (2) Cepstrum processing of the received signal, using Fourier transform and inverse transform analysis; and (3) use of a grid of time shift points for the correlation function, and identification of time shift values, associated with certain solution parameters for a least mean squares analysis that have the largest absolute values, as times of arrival of the direct and multipath signals. Separate identification of path delays reduces the least mean squares analysis to a solvable linear problem. A modified received signal is constructed, with multipath signal(s) approximately removed.

Adaptive equalization of multipath signals

The present invention relates to a method and system for determining target elevation angle, altitude and range and the like in a monopulse radar system with reduced multipath errors. A transmitter/receiver unit receives monopulse sum and difference signals caused by echoes from targets. The sum and difference signals are then logarithmically-amplified in a logarithmic amplifier unit. A selector selects one of the sum and difference signals having the largest amplitude, and generates a selection signal indicating which of the sum and difference signals has the largest amplitude. The selection signal is provided to a search radar target tracking unit which determines whether a target at a given range interval and azimuth interval, for example, has been selected for tracking by an operator. The search radar target tracking unit then controls a gate unit to selectively provide either the logarithmically-amplified sum signal or the logarithmically-amplified difference signal to a peak detection unit based on the selection signal, and based on whether a particular target has been selected for tracking. The peak detection unit determines peak value(s) in the logarithmically-amplified sum and difference signals provided by the gate unit. A target elevation angle/altitude calculation unit uses the peak value(s) to determine target elevation angle or altitude values, or average target elevation angle or altitude values. Such values may be displayed on a CRT for in correspondence with the selected target(s).

Method and apparatus for determining target elevation angle, altitude and range and the like in a monopulse radar system with reduced multipath errors

A monopulse radar system which optically displays radar information in 3-D for visual identification of targets. By visually displaying the radar target information in 3-D, the radar operator can quickly discern from its shape whether a particular target is a bomber, fighter, etc. and whether it is an enemy or friendly target. The system receives data from a high range resolution monopulse radar system having wideband monopulse tracking capability and processes it in a Display Processor so that its three outputs are representative of the three coordinate data information. The data is then displayed in a three coordinate display apparatus.

Digital radar target imaging with high radar resolution monopulse radar

A mirror antenna employing a continuous mirror without a hole. A feed hornnd an electromagnetic lens, located behind a rotatable twist reflector (the mirror), collimates a beam toward a polarized reflector located near the twist reflector and tilted to aim energy toward the twist reflector. Energy reflected back toward the polarized reflector from the twist reflector passes through the polarized reflector to free space.

Low sidelobe, high efficiency mirror antenna with twist reflector

The disclosed invention provides an accurate, simple and flexible method processing the receiver output of a high range resolution monopulse tracking radar to generate range and angle tracking error voltages based on the location of only the leading edge of the target echo replacing the conventional analog range error detectors and angle error processors in closed tracking loop systems The invention also processes the radar return signal to avoid interference from repeater jammers or multipath returns at low angle tracking

Range and angle discriminator for leading edge radar tracking

The invention relates to an apparatus and method for generating target range, azimuth angle, or elevation angle output signals corresponding to an apparent beam in a multiple-feed monopulse radar system. The multiple-feed monopulse radar system according to the present invention includes a transmitter/receiver unit, an adder/subtracter unit and a video comparator/adder unit. The transmitter/receiver unit is used to generate first and second actual antenna beams. Echoes caused by such actual beams are received and processed to provide first sum and first difference signals and second sum and second difference signals corresponding to the first and second actual beams, respectively. These signals are then supplied to the adder/subtracter unit which adds the first sum and first difference signals to provide a result Σ 1 +KΔ 1 , subtracts the first sum and first difference signals to provide a result Σ 1 -KΔ, adds the second sum and second difference signals to provide a result Σ 2 +KΔ 1 , and subtracts the second sum and second difference signals to provide a result Σ 2 -KΔ 2 . These results are supplied to the video comparator/adder unit which generates the sum or difference signals corresponding to the apparent beam. Through the mere addition of a comparator/adder unit to a prior art multiple-feed monopulse radar system, the precision of target range, azimuth angle or elevation angle measurements may be increased dramatically without significantly increasing the size, cost or complexity of the monopulse radar system.

Dean D. Howard

Papers

Method and apparatus for determining target elevation angle, altitude and range and the like in a monopulse radar system with reduced multipath errors

Digital radar target imaging with high radar resolution monopulse radar

Low sidelobe, high efficiency mirror antenna with twist reflector

Range and angle discriminator for leading edge radar tracking

Method and apparatus of generating sum or difference signals corresponding to an apparent beam in a monopulse radar system