Abstract: The present invention includes methods and apparatuses for imaging material properties in natural-fiber-containing materials. In particular, the images can provide quantified measures of localized moisture content. Embodiments of the invention utilize an array of antennas and at least one transceiver to collect amplitude and phase data from radiation interacting with the natural-fiber-containing materials. The antennas and the transceivers are configured to transmit and receive electromagnetic radiation at one or more frequencies, which are between 50 MHz and 1 THz. A conveyance system passes the natural-fiber-containing materials through a field of view of the array of antennas. A computing device is configured to apply a synthetic imaging algorithm to construct a three-dimensional image of the natural-fiber-containing materials that provides a quantified measure of localized moisture content. The image and the quantified measure are both based on the amplitude data, the phase data, or both.

Abstract: Improved microwave imaging using a reflector. By providing a reflective surface in the range of the imaging system, additional information is available for imaging objects. The relative surface provides silhouette information on the object, and increases the effective thickness of the object to aid analysis.

Abstract: A system includes a multi-system approach to detecting concealed weapons and person borne improvised explosive devices (PBIED). A first and second radar system operate at different center frequencies to provide, respectively, isolation of a target of interest from clutter and fine detail information on the target, such as whether the target is a living person, whether a concealed object may be present, material composition of the object, and shape, size, and position of the target relative to the system. Circular polarized radar beam may be used to distinguish a suspect object from within a crowd of people. Radar image of the object may be overlaid on visual image of a person carrying the object. Radar tracking of the object is coordinated with visual tracking of the target provided by a camera system, with visual display and tracking of the target overlaid with the radar information.

Abstract: A radar apparatus in which an interpolated sweep between adjacent real sweeps is formed irrespective of an interval between the real sweeps, and image data corresponding to one cycle of sweeping can be certainly updated. A sweep azimuth generator (12) generates and outputs an azimuth of sweep interpolated between a current and previous real sweep azimuth based on the current and previous real sweep azimuths, to a draw address generator (7). A sweep data generator (11) performs linear interpolation based on solitariness removed data of current real sweep data read from a sweep memory (4), and the previous solitariness removed real sweep data stored therein to generate and output interpolated sweep data to an image memory (8). The image memory (8) stores the solitariness removed real sweep data or the interpolated sweep data based on the real and interpolated sweep azimuths from the draw address generator (7), and outputs them to a display (9).

Abstract: Disclosed are systems, methods, devices, and apparatus to determine if a clothed individual is carrying a suspicious, concealed object. This determination includes establishing data corresponding to an image of the individual through interrogation with electromagnetic radiation in the 200 MHz to 1 THz range. In one form, image data corresponding to intensity of reflected radiation and differential depth of the reflecting surface is received and processed to detect the suspicious, concealed object.

Abstract: A system and a method to receive radar data from a plurality of radars and to reduce the data from the plurality of radars to a common universal latitude-longitude coordinate frame. The plurality of radars may be positioned at separate geographical locations and may have one or more overlapping regions. The data may be combined in the one or more overlapping regions.

Abstract: A method of imaging a moving object, including the steps of acquiring radar data reflected by the moving object, determining a motion state of the moving object; and generating a three-dimensional representation of the moving object based on the determined motion state, is disclosed. The motion state may be a complete solution of translational and rotational motion determined based on at least one of the inertia tensor components of the moving object, or solutions of Euler's torque-free equations of motions. The three-dimensional representation may be generated by reconstructing static patterns of the moving object based on estimated initial translational and rotational conditions of the object. A system for imaging the moving object according to this method is also disclosed.

Abstract: A system and method for presenting wind speed information in a manner so as to be easily understood and appreciated by viewers of televised weather report presentations and the like. Wind speed information is presented as a planar representation of three-dimensional wind speed data using contour lines, delineating areas with a planar location in the three dimensional data, overlaid on a geographic map display either alone, or in combination with radar reflectivity information. Wind velocity information received from a weather radar system, such as NEXRAD, relative to the weather radar is converted to absolute wind speed information for display.

Abstract: An active imaging system for imaging a target is described. The system includes a transmitting unit, a receiving unit, an antenna arrangement coupled to the transmitting unit and/or the receiving unit via a front end unit, and an image processing unit coupled to the receiving unit. The system also includes a control system coupled to the transmitting unit, the receiving unit and/or the image processing unit for controlling operation thereof. The antenna arrangement includes at least one rotating antenna synthetically forming a circular antenna. The image processing unit is configured for creating an image of the object by employing a synthetic aperture radar imaging algorithm.

Abstract: Techniques to image life forms through obstructions and at long standoff ranges employ a radar system that simultaneously transmits a plurality of RF pulse trains having different transmission frequencies and receives returns of the RF pulse trains reflected from a life form target. The returns are processed to generate digital radar data associated with the transmission frequency of each RF pulse train. The digital radar data is segmented and averaged to generate a Doppler spectrum response associated with the transmission frequency of each RF pulse train. Target classification is performed using the Doppler spectrum responses to extract biometric data describing the life form target.

Abstract: A system for draping meteorological data on a three dimensional terrain image has been developed. The system includes a central processing server that receives meteorological data in real time and drapes the meteorological data over a three dimensional terrain image. The image is then transmitted to a display computer for use by an end user.

Abstract: Method for organizing computer operations on a system of parallel processors to invert electromagnetic field data (11) from a controlled-source electromagnetic survey of a subsurface region to estimate resistivity structure (12) within the subsurface region. Each data processor in a bank of processors simultaneously solves Maxwell's equations (13) for its assigned geometrical subset of the data volume (14). Other computer banks are simultaneously doing the same thing for data associated with a different source frequency, position or orientation, providing a “fourth dimension” parallelism, where the fourth dimension requires minimal data passing (15). In preferred embodiments, a time limit is set after which all processor calculations are terminated, whether or not convergence has been reached.

Abstract: A millimeter-wave (MMW) based screening system is provided that may operate with an active sensor, a passive sensor, or in a dual mode using both the active and passive sensors. One or more such sensors are mounted so as to rotate along an axis that passes through a target region of detection, in which a person or object is positioned for screening. A reflector is disposed radially outward from the one or more rotating sensors to reflect MMW radiation between the sensors and the target region. The system may be employed as a portal screening system, and may include a structure having a wall and a roof, for rapidly screening persons for concealed objects. Algorithms may be employed to provide data output that avoids privacy issues.

Abstract: The system and method for standoff detection of human carried explosives (HCE) automatically detects HCE (112) up to a range of (200) meters and within seconds alerts an operator to HCE (112) threats. The system (100) has radar only, or both radar and video sensors, a multi-sensor processor (102), an operator console (120), handheld displays (122), and a wideband wireless communications link. The processor (102) receives radar and video feeds and automatically tracks and detects all humans (110) in the field of view. Track data continuously cues the narrow beam radar (118) to a subject of interest (110), (112) the radar (106), (108) repeatedly interrogating cued objects (110), (112), producing a multi-polarity radar range profile for each interrogation event. Range profiles and associated features are automatically fused over time until sufficient evidence is accrued to support a threat/non-threat declaration hypothesis.

Abstract: An interrogating system can include an interrogating apparatus configured to transmit toward and receive from a subject in a subject position, millimeter-wave electromagnetic radiation. Such a system can also include a controller configured to operate the interrogating apparatus, and produce data representative of a characteristic of the subject from received radiation. Some embodiments of such an interrogating system may include interrogating apparatus adapted to be mounted to a vehicle or at a vehicle loading zone, to interrogate passengers and/or other persons prior to boarding or accessing the vehicle. Such embodiments may include one or more controllers positioned within the vehicle or at the loading zone.

Abstract: An imager comprising a sphere of dielectric material and a geodesically configured substrate disposed adjacent said sphere. The geodesically configured substrate comprises a plurality of triangularly shaped elements, at least selected ones of the triangularly shaped elements having an array of detectors disposed thereon, the detectors in the array also being disposed adjacent the dielectric sphere for receiving and detecting incoming electromagnetic waves delivered via said sphere.

Abstract: The invention relates to a method of determining an estimated speed of an aircraft relative to ground being overflown by the aircraft, in which use is made of the sum of an acceleration measurement of the aircraft plus a difference value, the difference value being obtained from observation data or signals relating to a region of the ground.

Abstract: A radar imaging system for capturing an image of an object within an area of interest through at least one visual impairment. The radar imaging system comprises at least one radar array. The radar array includes a plurality of transmitter elements and a plurality of receiver elements for receiving a plurality of coded return signals from an object through the at least one visual impairment.

Abstract: A method and apparatus determines the shape of an orbiting or airborne object. A radar determines the general location and a telescope is directed toward the object to form an image of background stars, which will be occluded by the object. The image is compared with a memorized star map, to identify the region of the image in the map. Stars visible in the map which are not visible in the image are listed. The invisible stars are paired with next adjacent visible stars to form star pairs. The midpoints are identified of lines extending between star pairs. Segment lines are drawn between a midpoint and the next closest midpoint. The segment lines define an outline of the object.

Abstract: A radar device includes an antenna, from which a detection signal is transmitted while the antenna being rotated and by which a reflective wave of the transmitted detection signal is received to detect echo data, wherein image data is generated based on the detected echo data, a continuity detecting module for detecting a planer continuity of the currently detected echo data with respect to a pixel concerned in the image data, a behavior data generating module for generating behavior data indicative of a behavior of the echo data for a predetermined number of scans of the past in the pixel concerned based on behavior determination data, and an echo kind determining module for determining a kind of the echo data of the pixel concerned based on the planer continuity and the behavior data.

Abstract: A short range millimeter wave imaging radar system. The system includes electronics adapted to produce millimeter wave radiation scanned over a frequency range of a few gigahertz. The scanned millimeter wave radiation is broadcast through a frequency scanned transmit antenna to produce a narrow transmit beam in a first scanned direction (such as the vertical direction) corresponding to the scanned millimeter wave frequencies. The transmit antenna is scanned to transmit beam in a second direction perpendicular to the first scanned direction (such as the horizontal or the azimuthal direction) so as to define a two-dimensional field of view. Reflected millimeter wave radiation is collected in a receive frequency scanned antenna co-located (or approximately co-located) with the transmit antenna and adapted to produce a narrow receive beam approximately co-directed in the same directions as the transmitted beam in approximately the same field of view.

Abstract: An improved millimeter wave illumination system includes at least one primary source of millimeter wave radiation, a reflecting surface and a baffle comprising a plurality of exit apertures arranged such that at least some of the radiation from the source is reflected from the reflective surface before proceeding to the baffle, characterized in that means are incorporated for generating a plurality of radiation field states within a pre-determined time interval. The baffle, source and reflector are preferably packaged into a container with the exit apertures providing an illumination output. The generation of the plurality of radiation field states provides an illumination at the illuminator output that is less spatially variable when integrated over the pre-determined time interval.

Abstract: A navigation system having a radar altimeter is disclosed. The navigation system comprises a signal processing unit and one or more antennas in operative communication with the radar altimeter and the signal processing unit. The system further comprises a forward looking radar communicatively coupled to the radar altimeter. The forward looking radar and the signal processing unit are configured to provide forward looking radar measurements, radar altitude measurements from the radar altimeter, and datalink communications within a single forward looking radar scanning sequence.

Abstract: Systems and methods for mapping a surface of a celestial body containing objects and terrain are provided. One system includes a Synthetic Aperture RADAR (SAR) module configured to capture a high-resolution image of the terrain of at least a portion of the surface and a map module configured to store map data representing the portion of the surface. The system also includes a fusion module configured to combine the high-resolution image and the map data to generate a high-resolution map of the portion of the surface. A method includes orbiting the celestial body, capturing, via the SAR module, a high-resolution image during each orbit, and fusing the captured high-resolution image with a low-resolution map of the surface to generate a high-resolution map of the surface. A computer-readable medium for storing instructions that cause a processor to perform the above method is also provided.

Abstract: The spread spectrum radar apparatus in the present invention (i) includes: a transmission code generator (110); a reception code generator (121) generating a reception code obtained by delaying a transmission code; a spread modulator (112) spread-modulating a signal generated by a local oscillator (111) using the transmission code; a transmission antenna (113) transmitting the spread-modulated signal; a reception antenna (120) receiving a signal; a spread demodulator (122) demodulating the signal using the reception code to provide a correlation signal; a mixer (123) mixing the correlation signal and the signal generated by the local oscillator (111) to generate a radar signal; a virtual image determining unit (130) determining a virtual image; and a radar signal calculation device (160) calculating the radar signal using a virtual image determination signal, and (ii) adds a calculation and an offset signal for suppressing a peak intensity of the virtual image when the virtual image occurs.

Abstract: The vessel monitoring system has, in a trial navigation by provisionally setting a value of the speed of the own vessel arbitrarily, a display unit immediately display an Obstacle Zone by Targets (OZT) corresponding to the speed of the own vessel. The vessel monitoring system includes a calculator for calculating an Obstacle Zone by Targets, a display unit for displaying the Obstacle Zone by Targets obtained by the calculation by the calculator, and an integrated controller for processing trial navigation that integrally controls mutually cooperated processing of calculation by the calculator and display by the display unit, in a trial navigation by provisionally setting a value of the speed of the own vessel arbitrarily, so that the calculator calculates an Obstacle Zone by Targets corresponding to the arbitrarily and provisionally set value of the speed of the own vessel, and the display unit displays the result of the calculation.

Abstract: A method of error handling in a slope monitoring system that generates slope movement data from interferometric signal processing of radar images of the slope monitoring system. The error handling occurs in two steps. The movement data is corrected for changes in atmospheric conditions and disturbances are identified. It is convenient to mask the regions identified as disturbed in the display of the corrected movement data. Typical disturbances include short term disturbances, such as trucks, and long term disturbances, such as vegetation.

Abstract: An object information acquisition apparatus for acquiring information on the inside of an object includes an electromagnetic wave generation unit capable of outputting a terahertz wave and of changing the output intensity, an irradiation unit that irradiates an electromagnetic wave onto an object, a scanning unit and a detection unit that detects the electromagnetic wave irradiated onto the object. The scanning unit changes the relative positions of the irradiated electromagnetic wave and the object. The detection unit detects the electromagnetic wave transmitted through or reflected by the object as a result of interaction of the object and the electromagnetic wave.

Abstract: According to one embodiment, a synthetic aperture radar includes an image former coupled to a pair of antennas that are oriented at differing elevational angles relative to one another. The antennas are configured in a land-based vehicle that moves horizontally relative to a target having one or more internal features. The image former receives signals from the antennas that are indicative of electro-magnetic radiation reflected from a target and generates images according to the signals. The image former then generates a final image by filtering the amplitude component of the imagery from a first antenna against the amplitude component of the imagery from a second antenna.

Abstract: Motion measurement errors that extend beyond the range resolution of a synthetic aperture radar (SAR) can be corrected by effectively decreasing the range resolution of the SAR in order to permit measurement of the error. Range profiles can be compared across the slow-time dimension of the input data in order to estimate the error. Once the error has been determined, appropriate frequency and phase correction can be applied to the uncompressed input data, after which range and azimuth compression can be performed to produce a desired SAR image.

Abstract: Heretofore, a plurality of packages were used in a high frequency module in which a plurality of waveguide terminals were positioned resulting in problems, such as degradation of characteristics in the connection lines between packages, lower ease of assembly when mounting and connecting the connection lines, increased cost, and so forth. To solve these problems, a plurality of cavities having a part or the entire side metallized is formed in a multi-layer dielectric substrate. The multi-layer dielectric substrate is provided with a plurality of waveguide terminals, microstrip line-waveguide converters, RF lines, bias and control signal wiring, and bias and control signal pads. A high frequency circuit is mounted within the cavity and sealed with a seal and cover. This is intended to reduce the number of package, improve performance, improve fabrication, and lower the cost.

Abstract: To suppress cross-ambiguities in the examination of an ice region or dry region by means of aircraft- or aerospace-supported radar echo sounding, the region to be examined is overflown by a radar sensor (6) by multiple compatible radar sensors of the same operating wavelength on multiple spatially separated, substantially parallel paths, wherein the radar signal data received on each path are recorded. The radar signal data recorded for each of the different paths are summed coherently and using a weighting to form a radargram, wherein an adaptive complex-valued weighting for each of the individual paths is performed using a geometrical model which takes into account the topography of the environment of the region to be examined. The weighting for every depth of the examined region is determined by solving a system of linear equations from which is calculated a synthetic antenna pattern which has zeros in the direction of the ambiguities.

Abstract: In one aspect, a system to generate a radar signature of an object includes electromagnetic processing modules that include a first module including at least one processing unit to perform a shooting and bouncing (SBR) technique to solve for physical optics and multi-bounce characteristics of the object, a second module including a processing unit to perform a physical theory (PTD) technique to solve for material edges of the object and a third module including a processing unit to perform an incremental length diffraction coefficient (ILDC) to solve for material boss/channel. Results from the first, second and third modules are coherently integrated by frequency to generate radar cross section (RCS) values of the object in real-time. Performance of the system is scalable by adding processing units to at least one of the first, second or third modules.

Abstract: A sensor array having a plurality of modulated slots for microwave and/or millimeter wave imaging. The locations of the slots in the array define a spatial domain away from an object for detecting an electric field from the object. Each of the slots outputs a signal representative of the measured field and the location of the slot. A processor decodes the signals and generates an image of the object.

Abstract: A radar apparatus transmits a pulse signal including pulses having at least two different pulselengths in a specific transmit pulse pattern and receives a returning echo signal through a single antenna. A tuning voltage setting timing generator generates a timing of setting a tuning voltage according to a combination of transmission pulselengths and a tuning processor performs tuning operation in a manner suited to a current transmission pulselength based on the tuning voltage setting timing. The radar apparatus may include a tuning voltage alteration decider for deciding whether or not to alter the tuning voltage based on a combination of alternate pulselengths before altering the pulselength of the pulse signal generated by a transmitter and the tuning processor alters the tuning voltage based on the result of decision made by the tuning voltage alteration decider.

Abstract: A method for the detection of moving objects by SAR images envisages the steps of: generating a pulse-repetition frequency signal starting from a radar signal; and generating a sequence of SAR images starting from the pulse-repetition frequency signal. In particular, SAR images with low azimuth resolution are generated by of coherent integration of the pulse-repetition frequency signal for a sub-aperture time shorter than an aperture time. In addition, the method envisages generating difference images through point-to-point difference between subsequent low azimuth resolution SAR images, and recognizing patterns associated to moving objects in the difference images.

Abstract: A document retrieving apparatus can retrieve a target document and output the retrieved target documents according to ranking when a retrieval keyword or retrieval expression is input. However, it requires a skilful technique to narrow a retrieval range since an appropriate retrieval keyword or retrieval expression needs to be created. A document retrieving apparatus of the present invention reads out and compiles a document list included in a designated area when a user designates an area of a document to be read on a two-dimensional map. When the user designates an area of a document to be read on the two-dimensional map, the document retrieving apparatus of the present invention combines query vectors of a plurality of documents included in a designated area and extracts documents based on a combined query vector.

Abstract: In a holographic surveillance system (10) for near real-time imaging of a target (15), a source of RF radiation directs a non-amplified reference beam of pulsed coherent RF electromagnetic radiation toward a target. An array of antennas (31) receives a reflected beam from the target together with a component of the reference beam so as to produce a signal representative of phase and amplitude data of received energy, and a processor (20) processes the signals so as to produce a holographic image for display on a display device coupled to the processor.

Abstract: A computer system for processing complex synthetic aperture radar (SAR) images includes a database for storing complex SAR images to be processed, and a processor for processing a complex SAR image from the database. The processing includes receiving a complex SAR data set for a SAR image comprising a plurality of pixels, and applying a complex anisotropic diffusion algorithm to the complex SAR data set. The complex SAR data set includes a real and an imaginary part for each pixel.

Abstract: A method and system for generating images from projection data; a preferred embodiment comprising inputting projection data from at least one receiving element; generating a first aperture or array of data points containing positional and signal data; arbitrarily and/or randomly removing data points from the first array to form a series of subarrays comprising different sets of data points; generating preliminary images from the subarrays; comparing the corresponding image pixels from two preliminary images to determine for each pixel location the lesser or equal pixel values; forming a merged image from the lesser or equal pixel values; and repeating the comparison of corresponding image pixels of another preliminary image to the merged image to determine the lesser or equal pixel values until a merged image of the desired quality is obtained. A preferred embodiment of the system may comprise at least one processor, comparator and/or image generator.

Abstract: A weather radar system can be utilized on-board an aircraft. The weather radar system includes processing electronics for sensing weather. The processing electronics is configured to utilize sensed weather data to generate a vertical weather prediction for a given altitude in response to a range and an azimuth. The system can also include a display. The display provides visual indicia of the vertical weather prediction in response to the processing electronics.

Abstract: Systems and methods differentiate weather, such as storm cells and/or turbulence regions, based on location relative to a planned flight path of an aircraft. An exemplary embodiment compares a location of the weather with a location of a region of space corresponding to the planned flight path of the aircraft. In response to the location of the weather region being outside of the region of space, an icon is presented on a display corresponding to the weather using a first icon format. In response to location of the weather being within the region of space, the icon corresponding to the weather is presented on the display using a second icon format, the second icon format different from the first icon format.

Abstract: A method for estimating a radar cross-section (RES) of a given object by using a diffraction model of this object. With the model, it is possible to determine a basis adapted to said object on which is projected a vector of measurement. With the projected vector, it is possible to obtain a more complete reconstructed vector than the measurement vector in terms of incident wave and diffracted wave observation directions/polarizations and the components of which have a better signal/noise ratio than the measurements. The reconstructed vector is then used for calculating the RCS.

Abstract: The method processes measured vertical profiles of the power of the echoes returned following a transmission of radar signals, each measured vertical profile being a function of the sweep angle of the radar beam and associated with a given pointing angle/distance box pair of the radar beam. The method generates a synthetic vertical profile of the power of the echoes returned by the ground only, and includes, for each measured vertical profile: superposition of the synthetic vertical profile on the measured vertical profile in question, for various values of the sweep angle, calculation of the error that exists between the measured vertical profile and the synthetic vertical profile, for each sweep angle value in question, and an exclusion, from the measured vertical profile, of the values for which the calculated error is less than a given threshold, in order to generate a resultant vertical profile with no ground echoes.

Abstract: A millimetric wave imaging device includes: a lens antenna; a polygon mirror; a receiving portion; a scanning unit; and an image data generating unit. The receiving portion receives millimetric wave radiated from an object, transmitted through the lens antenna, and reflected on a mirror surface of the polygon mirror rotated by the scanning unit to detect a signal level of the millimetric wave. The image data generating unit generates image data representing an object image by receiving a detection signal from the receiving portion while driving the polygon mirror through the scanning unit.

Abstract: A millimeter-wave (MMW) based screening system is provided that may operate with an active sensor, a passive sensor, or in a dual mode using both the active and passive sensors. One or more such sensors are mounted so as to rotate along an axis that passes through a target region of detection, in which a person or object is positioned for screening. A reflector is disposed radially outward from the one or more rotating sensors to reflect MMW radiation between the sensors and the target region. The system may be employed as a portal screening system, and may include a structure having a wall and a roof, for rapidly screening persons for concealed objects. Algorithms may be employed to provide data output that avoids privacy issues.

Abstract: A traffic radar utilizes digital signal processing (DSP) to determine targets based on signal strength histories. From these histories, a target vehicle having the strongest Doppler return signal is identified and its speed is displayed, and a target vehicle having the highest frequency return signal is identified and its speed is displayed. The traffic radar may also display the relative strength of the strongest return signal and the relative strength of the highest frequency return signal, thereby showing a comparison of the strengths of the return signals from the target vehicles.

Abstract: A synthetic aperture radar to provide high resolution in the azimuth direction under the predetermined conditions of wide observation swathwidth in the range direction, stripmap observation and free PRF (Pulse Repetition Frequency) comprises a transmission antenna 102 for a single system and receiving antennae 104a, 104b for two systems. The beam width in the azimuth direction of a transmission beam 103 from the transmission antenna 102 is set equal to twice as wide as the beam width of each of the receiving antennae 104a, 104b. Moreover, a receiving antenna beam 105a is directed to the moving direction, while the other receiving antenna beam 105b is directed to opposite to the moving direction. The transmission antenna 102 and the receiving antennae 104a, 104b for two systems are used in common by dividing a single array antenna in the elevation direction to configure the receiving antennae 104a, 104b.

Abstract: A system and method for presenting wind speed information in a manner so as to be easily understood and appreciated by viewers of televised weather report presentations and the like. Wind speed information is presented as two or three-dimensional wind speed contour lines, delineating geographic areas corresponding to different wind speeds, overlaid on a geographic map display either alone, or in combination with radar reflectivity information. Wind velocity information received from a weather radar system, such as NEXRAD, relative to the weather radar is converted to absolute wind speed information for display.

Abstract: Systems and methods for producing radar images are provided. In illustrated embodiments, a representative system includes: a transmitter operative to transmit a pulsed signal; a receiver operative to sample the pulsed signal after reflection; a Doppler-shifting mechanism operative to create a Doppler shift in the pulsed signal; and a platform upon which the transmitter and the Doppler-shifting mechanism are mounted, the Doppler shift being associated with relative motion between the Doppler-shifting mechanism and the platform.