Abstract: According to one aspect of the present invention, a radar system is provided which accurately measures the surface profile in a wide sector beneath and forward of a helicopter, to aid low level transit and landing in poor visibility. This uses an electronic beam synthesis technique to form multiple beams directed at the area of interest, each measuring the distance to the first reflected signal received by each beam. These distances represent the profile of the ground and any objects on the ground. A processor then compares the measured profile with the ideal ground profile for safe landing. If the deviations from straight and level exceed the specified requirement for safe landing, or if sufficient rotor clearance is not detected, then a warning is given to the operator. A display will show the measured ground profile highlighting the unsafe regions, allowing the operator to seek a safe region to land.

Abstract: A land-based Smart-Sensor System and several system architectures for detection, tracking, and classification of people and vehicles automatically and in real time for border, property, and facility security surveillance is described. The preferred embodiment of the proposed Smart-Sensor System is comprised of (1) a low-cost, non-coherent radar, whose function is to detect and track people, singly or in groups, and various means of transportation, which may include vehicles, animals, or aircraft, singly or in groups, and cue (2) an optical sensor such as a long-wave infrared (LWIR) sensor, whose function is to classify the identified targets and produce movie clips for operator validation and use, and (3) an IBM CELL supercomputer to process the collected data in real-time. The Smart Sensor System can be implemented in a tower-based or a mobile-based, or combination system architecture. The radar can also be operated as a stand-alone system.

Abstract: This disclosure provides an information display device. The information display device includes an acquirer for acquiring positional information on one or more display targets including at least one of a landmark serving as a reference mark used when a movable body is in move, another movable body, and a location registered by an operator, and a controller for displaying positional information and circumferential information on the movable body in an information display area, associating at least one of the one or more display targets of which a position is outside the information display area with a direction to which the at least one of the one or more display targets is located centering on the movable body, and displaying the at least one of the one or more display targets in an outer circumferential area of the information display area.

Abstract: An antenna device is provided. The antenna device includes a radiator for radiating an electromagnetic wave, and a dielectric body arranged on an electromagnetic wave radiating side of the radiator, and having a plurality of dielectric members arrayed in a longitudinal direction of the radiator, wherein boundaries between the plurality of adjacent dielectric members are asymmetric with respect to a virtual line perpendicularly passing through the center of the dielectric body in the longitudinal direction.

Abstract: A method for indicating a weather threat to an aircraft is provided. The method includes inferring a weather threat to an aircraft and causing an image to be displayed on an aviation display in response to a determination by aircraft processing electronics that the inferred weather threat to the aircraft is greater than a measured weather threat to the aircraft.

Abstract: A radiometric imaging device and a corresponding method for scanning a scene. The device comprises a radiometer configured to detect radiation in a predetermined spectral range emitted from said scene and to generate a radiation signal from said detected radiation, and a processor configured to process said generated radiation signal by de-convoluting said generated radiation signal by use of a distance-dependent de-blur kernel, which is determined depending on the distance between said scene and the radiometer.

Abstract: This invention will be an apparatus, system and use of Ground Penetrating Radar (GPR) as a noninvasive and non-destructive means to detect and examine tree roots, below grade of the soil surface. This invention will provide a means and methodology for objective evaluation of tree root defects based upon standards for urban trees at all levels of the Nursery Tree Industry. The output from software algorithms will provide guidance for remediation of defects when appropriate, inventory and management data for proactive maintenance at all levels of the supply chain. This apparatus, system and methodology will be a new and useful process at all levels of the supply chain for nursery tree stock.

Abstract: A system and method for adjusting a target value for generating a vertical profile view in an aircraft weather radar system is provided. Processing electronics are configured to receive a target value for generating a vertical profile view of weather detected by the radar system. The processing electronics are also configured to adjust the target value to account for the motion of the aircraft and/or the motion of the detected weather.

Abstract: Autonomous Underwater Vehicles (AUV) collect and transmit information about ice floe thickness; this is combined with SYNTHETIC APERTURE RADAR images from satellites to identify and track dangerously thick regions of ice. The overlayed data is presented graphically to allow tracking of the thick ice regions over time. This information is used to alert drilling platforms in icy ocean conditions of pending ice floe dangers.

Abstract: Systems and method for near-field millimeter wave imaging are provided, in particular, near-field millimeter wave imaging systems and methods that enable sub-wavelength resolution imaging by scanning objects with sub-wavelength probe elements and capturing and measuring phase and intensity of reflected energy to generate images.

Abstract: In an embodiment of the disclosed technology, a visual output of data from a ground-penetrating radar is displayed on a visual medium. The display has a first exhibition of output from a higher frequency range antenna, a second exhibition of output from a lower frequency range antenna (compared to the other antenna; see definition in the “detailed description”), and a transition area between the first and second exhibition having merged data from the lower frequency antenna and the higher frequency antenna. The depth range of the transition area may be varied based on optimal depth range of each antenna, such as manually by a viewer viewing the visual output, which may occur in real-time, that is, while operating the radar and viewing the visual output thereof. Or, the transition depth range and/or width of the transition region may be varied as part of post-processing.

Abstract: One aspect relates to determining a position of at least one positional display element that can be used to display at least an image portion; and displaying the at least the image portion with the at least one positional display element based at least in part on the determining the position of the at least one positional display element. Another aspect relates to determining a position of at least one positional display element, in which the position can be used to affect a visual presentation.

Abstract: This disclosure provides an echo image display device, which includes an antenna for discharging electromagnetic waves and receiving echo signals reflected on one or more target objects, an echo signal input unit for inputting the echo signals from the antenna, an echo signal level detector for detecting a level of each of the echo signals with reference to a distance and an azimuth from the antenna, an image data generating module for generating image data based on the levels of the echo signals, a display unit for displaying the image data, and a data amount changing module for changing a data amount rate of a predetermined area that is set as a part of a display area of the display unit, into a different rate in another part of the display area.

Abstract: A data processing apparatus that can set the magnification factor according to the distance from the antenna is provided so that the display of objects close to the antenna is easier to see and with which the changes in the settings of the magnification factor is easy. The buffer memory stores the digital signals converted by the A/D converter in association with the distance and azimuth with respect to the antenna. The digital filter filters the digital signals read from the buffer memory. A digital filter is provided that converts a value of data of interest, of digital data stored in the memory, to a value based on values of the data of interest to be processed and peripheral data in a periphery of the data of interest, and the digital filter changes a range of the peripheral data used for a filter processing according to the distance from the antenna to the data of interest.

Abstract: An electromagnetic body scanning system may include a measuring system for measuring data of radio waves scattered by a body in two distinct subbands; and a computer system. The computer system is arranged for constructing a first image of the body using the measured data, generating synthetic scattered data of the body in a frequency range outside the subbands, and constructing a second image of the body using both the measured data and the synthetic data. The step of constructing a first image includes matching an image to a human model.

Abstract: A presence detector unit (PDU) of the type relying on microwave radiation provides a signal indicating movement within a defined space when such movement occurs. A source of microwave radiation within a housing projects a beam of microwave radiation directed through a side of the housing to suffuse at least a portion of the defined space. A detector within the housing senses changes in microwave radiation reflected back toward the detector. An adjustable beam occlusion structure is supported by the housing and blocks a portion of the microwave radiation emanating from the source and through the side of the housing.

Abstract: A subterranean radar array system and method for imaging a subterranean target area. In one example, the subterranean radar array includes a plurality of radar chains disposed in a plurality of underground columns, each radar chain including a plurality of radar units forming the plurality of radar chains and at least one processor coupled to a corresponding at least one of the plurality of radar chains and configured to generate an image of a subterranean target area from signals received from the at least one radar chain.

Abstract: A system and method for pseudo real time collection of receive signal data in a single- or multi-channel ground penetrating radar. Each channel transmits electromagnetic impulses into a medium under test during each of a plurality of runs over the medium. Run receive signals are received in response to the transmitted impulses. Each run receive signal is sampled multiple times at a run sample rate. The sample points of each run are delayed by delay sequences with respect to the sample points of the other runs. The sample points of the individual runs are stored as a composite set of sample points representative of a receive signal sampled at an effective sample rate equal to a multiple of the run sample rate where the multiple is the number of runs.

Abstract: A system and method is shown for receiving microwave/millimeter-wave signals. The system and method are balanced and can be effectively implemented on a silicon substrate using single pole double throw switches.

Abstract: This disclosure provides a signal processing device, which includes a reception signal acquiring module for acquiring reception signals received by a radar antenna, an identifying module for identifying a kind of each reception signal, an extracting module for extracting the reception signal for each kind, and a kind-base signal processing module for performing individual signal processing for each kind of the extracted reception signal.

Abstract: A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

Abstract: A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

Abstract: An unsynchronized acoustic or radio-frequency (RF) computed tomography (CT) imaging system with matched, but independent, continuous wave (CW) transmitters and receivers configured to radiate acoustic or RF transmissions in a plurality of vector paths through solid geologic material. A computer calculates and displays tomographic images constructed from individual acoustic or RF path signal travel time or attenuation measurements logged from registered locations from the CW transmitters and receivers after their being shuttled amongst a number of different transmitter and receiver perspectives available around said geologic material to generate data necessary for computed tomography. Each of the transmitters and receivers include independent unsynchronized crystal oscillators rated at 10-ppm or better frequency uncertainty to produce and to detect CW radio frequency (RF) transmissions.

Abstract: Described are a method and apparatus for high-speed phase shifting of an optical beam. A transparent plate having regions of different optical thickness is illuminated by an optical beam along a path of incidence that extends through the regions. The transparent plate can be moved or the optical beam can be steered to generate the path of incidence. The optical beam exiting the transparent plate has an instantaneous phase value according to the region in which the optical beam is incident. Advantageously, the phase values are repeatable and stable regardless of the location of incidence of the optical beam within the respective regions, and phase changes at high modulation rates are possible. The method and apparatus can be used to modulate a phase difference of a pair of coherent optical beams such as in an interferometric fringe projection system.

Abstract: A method, a radar image registration manager, and a set of instructions are disclosed. A primary sensor interface 430 may receive a primary sensor image and a camera model of the primary sensor image. A data storage 420 may store a digital elevation model. A processor 410 may automatically align the primary sensor image with the digital elevation model.

Abstract: A signal processor (30) for a submillimeter wavelength active radar system (10, 20, 30) processes signals received and downconverted by the radar system, the downconverted signals corresponding to a given pixel of the field of view having time varying amplitude and phase components which have a periodic component which is dependent on content. Information about the content is discriminated from the periodic component. By using phase rather than only amplitude, there is additional information in the downconverted signals. The phase is more sensitive to changes in the content such as objects, background and atmospheric conditions, than amplitude alone. The phase information enables the periodic component to be retained which can be characteristic of the content owing to content flutter, changes in submillimeter standing waves and interference fringes in received reflections of submillimeter illumination if surface layers have a thickness of a number of half wavelengths.

Abstract: This disclosure provides a radar device, which detects an object of interest from image data produced based on an input signal containing echo signals caused by transmitted signals reflecting on objects. The radar device includes a memory module for storing template image data produced based on one or more characteristics of the echo signals of the object of interest, a pattern matching module for performing pattern matching of the image data and the template image data, an identifying module for identifying an area within the image data containing the object of interest corresponding to the template image data, when the object of interest is detected from the image data as a result of the pattern matching.

Abstract: A system and method for detecting dangerous objects and substances are disclosed. According to one embodiment, a method comprises generating a microwave signal that is reflected by a target to render one or more reflected signals. The one or more reflected signals are received at an antenna array. The one or more reflected signals are converted into digital reflected signals. The microwave signal is converted into a digital signal. The digital reflected signals and the digital signal are processed to determine the three dimensional position of the target. The digital reflected signals and the digital signal are processed to identify the target. The digital reflected signals and the digital signal are processed to determine a state of the target; and determine whether the target a dangerous object.

Abstract: Methods and systems may image an object of interest using one or more probes. More specifically, such exemplary methods and systems may deliver electromagnetic energy (e.g., microwave energy) using a transmitting antenna to the object while activating a probe to interact with the scattered field and sampling the resulting scattered field using one or more receiving antennas. The sampled electromagnetic energy may then be used to reconstruct an image of the object.

Abstract: The present invention relates to an active radar system and a corresponding method. The proposed system comprises at least two transmit antennas that each transmits radiation to a scene as a transmit signal, said transmit signal comprising a series of frequency modulated pulses, at least one receive antenna that receives radiation from said scene as a receive signal, a controller that controls said at least two transmit antennas. The transmissions of the transmit signals are subsequently initiated with time offsets, controlled to be larger than the time delay between transmission of a first transmit signal of said two transmit signals and reception of radiation of said first transmit signal by said at least one receive antenna and to be smaller than the time duration of a complete frequency modulated pulse of said first transmit signal.

Abstract: A standoff range, sense-through-obstruction radar system is capable of detecting micro-Doppler, or life form signatures, and movements through obstructions at stand-off ranges and displaying the target information over a live video feed of the area under surveillance. The sense-through-obstruction radar system comprises an antenna assembly that includes a horn antenna and a reflector configured to reflect radio frequency (RF) energy to/from the horn antenna. An antenna pointing assembly supports the antenna assembly. The antenna pointing assembly is configured to move the antenna assembly to point the antenna assembly toward an obstruction. A sensor assembly is mounted to the antenna assembly so that the sensor assembly is aligned with the RF beam formed from the RF energy reflected from the reflector to the horn antenna. The sensor assembly is configured to detect the location of the obstruction and to provide information to assist pointing of the antenna assembly toward the obstruction.

Abstract: A method and a terminal for providing a route in a navigation system using a satellite image are provided. The terminal includes a route calculation unit for calculating a route from a current location to a destination when a user inputs the destination, a satellite image requesting unit for requesting a satellite image server for satellite images corresponding to locations on the route and for downloading the requested satellite images, a satellite image storage unit for storing the downloaded satellite images, and a controller for retrieving a satellite image corresponding to the current location from the satellite image storage unit and for displaying the retrieved satellite image simultaneously while downloading the satellite images corresponding to the locations on the route.

Abstract: A method for generating an image is provided including taking a first active radar image of an object from a first position with a handheld screening device; taking a second active radar image of the object from a second position with the handheld screening device; and generating a third image based on the first active radar image and the second active radar image. A corresponding handheld screening device is provided as well.

Abstract: A display system and method is provided for deployment on board a vehicle and includes a data source that provides the display system with data indicative of at least time, position, and velocity of the vehicle. The system comprises a monitor, a display included within the monitor for displaying range data indicative of a specific distance and time data indicative of time it takes to travel the specific distance, an input device, and a processor coupled to the monitor and to the input device and configured to (1) render symbology on the display visually representative of the time data and the range data, and (2) update the range data, and correspondingly change the time data in response to the change in range data made via the input device.

Abstract: An indirect radar holography apparatus for scanning a scene and generating a high-density signal pattern representing the scene. The apparatus illuminates the scene with radiation according to an illumination signal; generates a reference signal from the illumination signal; detects radiation emitted in a predetermined spectral range from a spot of the scene; generates a radiation signal per spot from the detected radiation; performs control so that radiation is detected at a number of spots distributed over the scene, the number being lower than the number of intensity signals of the high-density signal pattern; combines the radiation signals generated from the detected radiation and the reference signals to obtain a low-density signal pattern of intensity signals; and processes the intensity signals of said low-density signal pattern to generate the high-density signal pattern by applying compressive sensing to the low-density signal pattern.

Abstract: A method of managing an aircraft in flight may include electronically monitoring for a presence of a threat object along a flight path of the aircraft and at a destination airport of the aircraft, and electronically generating an alert when the presence of the threat object is detected. The alert may include information enabling air traffic control (ATC), flight dispatch, and a pilot of the aircraft to make a collaborative flight path correction decision that may prevent the aircraft from being affected by the threat object.

Abstract: Described are a method and apparatus for high-speed phase shifting of an optical beam. A transparent plate having regions of different optical thickness is illuminated by an optical beam along a path of incidence that extends through the regions. The transparent plate can be moved or the optical beam can be steered to generate the path of incidence. The optical beam exiting the transparent plate has an instantaneous phase value according to the region in which the optical beam is incident. Advantageously, the phase values are repeatable and stable regardless of the location of incidence of the optical beam within the respective regions, and phase changes at high modulation rates are possible. The method and apparatus can be used to modulate a phase difference of a pair of coherent optical beams such as in an interferometric fringe projection system.

Abstract: Radiometric imaging for scanning a scene includes a radiometer for detecting radiation emitted in a predetermined spectral range from a spot of the scene and for generating a radiation signal from the detected radiation. Spot movement circuitry effects a movement of the spot, from which the radiation is detected, to various positions. Control circuitry controls the spot movement circuit to effect the movement of the spot from one position to another position so that radiation is detected at a number of spots distributed over the scene. The number is lower than the number of pattern signals of the high-density signal pattern and the radiation signals generated from the radiation detected at the number of spots form a low-density signal pattern. Processing circuitry processes the radiation signals of the low-density signal pattern and generates the high-density signal pattern by applying compressive sensing to the low-density signal pattern.

Abstract: The disclosed device generates a plurality of pixel data in an XY coordinate system. The pixel data includes first pixel data generated on a first sweep line, according to a distance from a transmitting source, based on an echo of a detection signal from the source toward a first direction, and second pixel data generated on a second sweep line, according to a distance from the source, based on an echo of a detection signal from the source toward a second direction different from the first direction. The device includes a module for converting the first and second pixel data into data in the XY coordinate system, a module for generating pixel data of an interpolation target pixel located between a first pixel as an observing pixel on an interpolation axis parallel to X-axis or Y-axis and a second pixel as a corresponding pixel on the same interpolation axis, based on the pixel data on the first and second sweep lines.

Abstract: A microwave imaging system uses microwave radiation provided by a microwave source to image targets. The system includes an array of antenna elements that are capable of being programmed with a respective direction coefficient to direct the microwave illumination from the microwave source toward a position on the target. The antenna elements are further capable of being programmed to receive reflected microwave illumination reflected from the position on the target. A processor is operable to measure an intensity of the reflected microwave illumination to determine a value of a pixel within an image of the target. Multiple beams can be directed towards the target to obtain corresponding pixel values for use by the processor in constructing the image.

Abstract: The invention provides a security scanner that produces a radar profile of a clothed person or another object such as a bag carried by a person at a distance and does not require close proximity of the person or object to the scanner itself. The scanner includes a millimeter wave antenna system optimised for short-range active imaging and arranged to provide rapid high-resolution images of an object or person of interest and processing means for resolving the images so as to detect the presence of predetermined objects. The processing means preferably includes means for comparing contrasts in reflectivity in the scanned images with predetermined expected values from skin and light clothing. The processing means may also include means for detecting predetermined behavioral or physical traits such as the effect on gait on carried weighty objects or stiff structures strapped to the person from the images of a scanned object or person. The scanner may be incorporated within a turnstile access arrangement.

Abstract: A heterogeneous antenna array containing antenna elements of different antenna element sizes interleaved among one another is disclosed. Heterogeneous antenna arrays as disclosed herein can efficiently cover a broad range of frequencies without loss of optimality at higher frequencies. Also disclosed are methods of frequency-domain oriented image reconstruction which are suitable for use with heterogeneous antenna arrays.

Abstract: A method and system for generating images from projection data comprising: at least one processor for processing input data, the input data comprising positional data and image data, the image data comprising frequency data for a pre-determined number k frequencies the at least one processor operating to: a) set the frequency data to zero for a predetermined percentage of the k frequencies to form modified frequency data; b) form a preliminary image comprising an array of retained pixel values based upon first positional data and the modified frequency data; c) set the frequency data to zero for a predetermined percentage of the k frequencies to form modified frequency data; d) form a modified image comprising an array of pixels based upon the positional data and the modified frequency data; e) compare the retained array of pixel values to the pixel values of the modified image formed at step (d); f) retain the minimum pixel value at each pixel location to form an image comprising minimum pixel values; g) rep

Abstract: A standoff range, sense-through-obstruction radar system is capable of detecting micro- Doppler, or life form signatures, and movements through obstructions at stand-off ranges and displaying the target information over a live video feed of the area under surveillance. The sense-through-obstruction radar system comprises an antenna assembly that includes a horn antenna and a reflector configured to reflect radio frequency (RF) energy to/from the horn antenna. An antenna pointing assembly supports the antenna assembly. The antenna pointing assembly is configured to move the antenna assembly to point the antenna assembly toward an obstruction. A sensor assembly is mounted to the antenna assembly so that the sensor assembly is aligned with the RF beam formed from the RF energy reflected from the reflector to the horn antenna. The sensor assembly is configured to detect the location of the obstruction and to provide information to assist pointing of the antenna assembly toward the obstruction.

Abstract: A method of mapping a space using a combination of radar scanning and optical imaging. The method includes steps of providing a measurement vehicle having a radar system and an image acquisition system attached thereto; aligning a field of view of the radar system with a field of view of the image acquisition system; obtaining at least one radar scan of a space using the radar scanning system; obtaining at least one image of the space using the image acquisition system; and combining the at least one radar scan with the at least one image to construct a map of the space.

Abstract: A method and system for investigating and displaying an image of an area of interest comprising a moving vehicle; at least one processor for producing an image of the area of interest; at least one first transmitter for emitting first signals substantially in a first direction, the at least one first transmitter being operatively associated with the moving vehicle and the processor; at least one first receiver for receiving backscattered signals resulting from the first radar signals, the at least one first receiver being operatively associated with the moving vehicle and the processor; at least one second transmitter operatively for emitting second signals in a direction substantially opposite to the first direction, the at least one second transmitter being operatively associated with the moving vehicle and the processor; at least one second receiver for receiving backscattered signals resulting from the second signals, the at least one second receiver being operatively associated with the moving vehicle an

Abstract: A radar device is provided, which includes a receiver for transmitting a pulse-shaped radio wave and receiving a corresponding reflection signal as a reception signal, a Doppler processor for generating Doppler processed signals that are signals obtained by separating the reception signal according to Doppler frequencies or signals obtained based on the signals separated, an improvement level calculator for calculating a signal improvement level by comparing an amplitude value of the reception signal with amplitude values of the Doppler processed signals, a signal synthesizer for synthesizing the reception signal and the Doppler processed signals based on the signal improvement levels, and a display processor for generating a radar image based on the synthesized signal.

Abstract: A method and apparatus is devised for detecting objects of interest in which frequency-scanned RF in the HF region of the electromagnetic spectrum is projected out across a given area and returns are detected and converted into image data in which phase, amplitude, range and frequency associated with the incoming data is correlated with frequency-dependent range templates to determine the existence of, the range of and the direction of the objects of interest.

Abstract: A method includes inputting an echo signal from an antenna for discharging an electromagnetic wave to a predetermined area and receiving an echo signal reflected on a target object, outputting a level of the echo signal from every location so as to associate the level with a distance from the antenna in an azimuth direction where the electromagnetic wave is discharged, calculating a degree of change in the level of the echo signal from mutually adjacent locations among all the locations concerned, performing edge emphasis processing for the level of the echo signal in the azimuth direction based on the degree of change and outputting an edge-emphasized echo signal, and performing scan-to-scan correlation processing to calculate a correlation value of the echo signals of two or more scans using the edge-emphasized echo signals, where the echo signals from the entire predetermined area is used as one scan.

Abstract: In embodiments a system to generate a dual frequency, circularly polarized beam of rotating electromagnetic radiation comprises a first radiation source to generate a first radiation beam at a first frequency, a second radiation source to generate a second radiation beam at a second frequency, different from the first frequency, and a tee. In some embodiments the tee receives the first radiation beam and the second radiation beam, outputs a third radiation beam which represents a sum of the first radiation beam and the second radiation beam, and outputs a fourth radiation beam which represents a difference between the first radiation beam and the second radiation beam, wherein the third radiation beam and the fourth radiation beam are separated by a ninety-degree phase shift. The system further comprises a combiner to combine the third and fourth beams to produce an output beam. Other embodiments may be described.