Vladimir Kolinko

Passive millimeter-wave imaging for airborne and security applications

As a result of its relatively short wavelength coupled with relatively high penetration of such things as fog, bad weather and clothing, millimeter-wave imaging provides a powerful tool for both airborne and security type applications. By using a passive approach such as that implemented here, it is possible to image through bad weather or detect concealed weapons and articles all without generating any form of radiation that might either help an enemey or raise health concerns. In this paper we will show imagery from our second generation state-of-the-art unit and discuss the technology involved.

Video-Rate Passive Millimeter-Wave Imaging Using Phased Arrays

Passive millimeter-wave imaging technology has matured in conformance with the conventional focal-plane imaging architecture of visible light and infrared cameras. The longer wavelength at millimeter-wave frequencies allows for practical implementation of alternative pupil-plane camera architectures based on frequency-scanned phased arrays, with benefits to hardware ruggedness, form factor and cost. Challenges associated with millimeter-wave phased arrays include path matching over relatively long signal paths, and the implementation of transmission lines with extremely low loss compared to commercially available substrates. A W-band millimeter-wave phased array imager operating between 76 and 94 GHz is presented with technical performance data and examples of imagery.

A passive millimeter-wave imaging system for concealed weapons and explosives detection (Invited Paper)

This paper describes a passive millimeter-wave image scanner that leverages technologies previously developed for a video-rate passive millimeter-wave camera (PMC) [1, 2]. The imager has a prime focus elliptical frequency scanned antenna operating in the 75-93 GHz millimeter-wave band, a low noise receiver and a vertical beam former that allows the instantaneous capture of 128 pixel (vertical) column images in 1/30th of a second, with 2-3 K sensitivity. Two dimensional images are created by mechanically rotating the antenna, which produces a 128x60 raster image in 2 seconds. By integrating (averaging) images over a longer time period, we have demonstrated a sub-degree temperature resolution. This sensor has proven itself as a low cost tool for studying the potential of W-band passive imaging for various applications.

Rapid passive MMW security screening portal

Trex Enterprises Corporation has developed a full body passive millimeter-wave security screening imager. The system images naturally occurring W-band blackbody radiation, which penetrates most types of clothing. When operated indoors, the primary mechanism for image formation is the contrast between body heat radiation and the room temperature radiation emitted or reflected by concealed objects that are opaque at millimeter-wave wavelengths. Trex Enterprises has previously demonstrated that an imager noise level of 0.25 to 0.5 K is necessary to detect and image small concealed threats indoors. Achieving this noise level in a head-to-toe image required image collection times of 24 seconds using the previous imager design. This paper first discusses the measurement of the noise temperature of the MMW detectors employed. The paper then explores reducing the image collection times through a new front-end amplifier design and the addition of more imaging units. By changing the orientation and direction of travel of the imaging units, the new design is able to employ more detectors and collect imagery from a subjects front and sides. The combination of lower noise amplifiers and a new scanning architecture results in an imager appropriate for high throughput security screening scenarios. Imagery from the new configuration is also presented.

A real-time wide field of view passive millimeter-wave imaging camera

With the current upsurge in domestic terrorism, suicide bombings and the like, there is an increased interest in high technology sensors that can provide true stand-off detection of concealed articles such as guns and, in particular, explosives in both controlled and uncontrolled areas. The camera discussed in this paper is based upon passive millimeter-wave imaging (75.5-93.5 GHz) and is intrinsically safe as it uses only the natural thermal (blackbody) emissions from living beings and inanimate objects to form images with. The camera consists of four subsystems which are interfaced to complete the final camera. The subsystems are Trexs patented flat panel frequency scanned phased array antenna, a front end receiver, and phase and frequency processors to convert the antenna output (in phase and frequency space) into image space and in doing so form a readily recognizable image. The phase and frequency processors are based upon variants of a Rotman lens.

Concealed weapons detection with an improved passive millimeter-wave imager

Trex Enterprises has developed a second-generation passive millimeter-wave imaging system for detection of concealed weapons and explosives at standoff ranges. Passive millimeter-wave sensors form an image from naturally emitted blackbody radiation in the millimeter-wave portion of the electromagnetic spectrum. Radiation at this wavelength passes through most types of clothing, allowing the user to acquire an image of any articles on a suspect’s person that differ significantly from the human body in their reflectivity or radiometric temperature at millimeter-wave wavelengths. Trex Enterprises previously demonstrated a first-generation concealed weapon detection system with the ability to detect handguns and knives under heavy clothing at a range of 27’. The second-generation imager, while similar in concept, has an improved field-of-view and a much reduced size and weight. The imager is to be put through a battery of tests by both Trex Enterprises and the National Institute Of Justice to determine its ability to detect both metallic and non-metallic knives and handguns as well as various types of explosive devices. The tests will be conducted indoors and outdoors at various ranges.

An E-band Electronically Scanned Imaging Radar System

A bi-static E-band (80GHz) electronically scanned imaging radar system has been fabricated and tested. This radar system combines a stare-mode array within a frequency-scanned antenna to extract azimuth and elevation information, while utilizing a frequency modulated CW (FMCW) transceiver to extract range. This unique architecture provides state of the art instantaneous field of view and voxel refresh rates for electronically scanned systems while requiring less RF components than conventional phased array systems, enabling a cost-effective means for volume production of electronically scanned high resolution imaging radar.

Passive millimeter-wave imaging technology for phased-array systems

Trex Enterprises has developed a passive millimeter-wave imaging system incorporating a number of new technologies. The system has a pupil-plane architecture that uses a phased array, flat panel antenna and a phase processor based upon millimeter-wave optics. The production and operation of a 232-element W-band phased array and processor poses a number of technical problems including minimizing losses in the front end and adjusting the phase lengths of the processor. The system also has 192 frequency processor cards that perform real-time Fourier analysis of W-band signals over an 18 GHz bandwidth using millimeter-wave optics. Production of a suitable phase and frequency processor in large quantities that form good beams and maintain signal strength requires the adoption of new materials and design strategies. The refinement of these technologies at W-band frequencies allowed Trex Enterprises to produce an imager which is both compact and suitable for large-scale production. In this paper, we will discuss the design and production of the millimeter-wave components unique to this system architecture. We will also present the performance of these components and how they affect the performance of the millimeter-wave imager as a whole. An integrated front end is tested to determine the accuracy of the beam-forming network in producing antenna patterns.

Millimeter-wave radar for brown-out landings using passive imager components

A millimeter-wave radar designed for landing helicopters in brown-out conditions is described and data is presented from an initial flight test. The radar operates in a frequency modulated continuous wave architecture, determining range to target by calculating the difference between transmitted and returned frequencies. The millimeter-wave frequency band provides sand and dust penetration and allows for small apertures appropriate for helicopter mounting. This radar also uses a flat panel phased-array receive antenna and phase processor to sample multiple antenna beams simultaneously, an architecture that has previously been successfully used in passive millimeter-wave imaging systems. The radar presents a wide field-of-view image to the operator at a 3 Hz frame rate where range to the ground and obstacles is depicted in grayscale. The flight test showed the radar to be capable of depicting terrain height variations and obstacles such as buildings, vehicles, building materials, and even power lines. Reductions in noise and symbology improvements are necessary developments for a viable landing system.

Flight test of MMW radar for brown-out helicopter landing

Trex Enterprises and US Army RDECOM CERDEC Night Vision Electronic Sensors Directorate developed and tested helicopter radar to aid in brown-out landing situations. A brown-out occurs when sand and dust kicked up by the helicopter rotors impair the pilots vision. Millimeter-wave (MMW) radiation penetrates sand and dust with little loss or scattering, and radar at this frequency can provide a pilot with an image of the intended landing zone. The Brown-out Situational Awareness System (BSAS) is a frequency-modulated, continuous-wave radar that measures range to the ground across a conical field-of-view and uses that range information to create an image for the pilot. The BSAS collected imagery from a helicopter in a blowing sand environment with obstacles including ditches, hills, posts, poles, wires, buildings and vehicles. The BSAS proved the capability to form images of the ground through heavy blowing sand and resolve images of some obstacles. The BSAS also attempted to differentiate flat ground from bumpy ground with limited success at some viewing angles. The BSAS test imagery includes some artifacts formed by high radar cross-section targets in the field-of-view or sidelobes. The paper discusses future improvements that could limit these artifacts.