This PDF file contains the front matter associated with SPIE Proceedings Volume 10634, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The increasing publicity behind self-driving cars and other public transport gives rise to, amongst other things, the need for new kinds of sensors that have long range, high resolution and provide the basic data to enable discrimination between different types of objects both moving or stationary. In addition, aircraft such as helicopters which are expected to operate in dangerous and normally inaccessible locations also require highly sophisticated sensors. This paper describes a new kind of millimetre wave all weather radar that is small, light, has long range and very high resolution. It uses electronic scanning, monopulse signal processing and IQ mixing to enable multi-target detection. The radar employs a new chipset designed on 4 mil GaAs PHEMT process with Rotman lenses based on lightweight PTFE/ceramic laminates. The complete front end offers good range, excellent RCS performance and would be applicable to both automotive or airborne applications.

This paper presents calibrated radar cross section (RCS) data of various objects considered to be a hazard for a landing helicopter and a technique for extracting these values from inverse synthetic aperture radar (ISAR) imagery. Data was collected at an outdoor facility using a fully polarimetric, 94-GHz radar mounted on an elevator that was positioned on a 125-foot tower to collect data at various depression angles. Targets were placed on a 22-foot diameter turntable and rotated a full 360 degrees to form ISAR imagery at all aspect angles. The technique being described was formulated to enable the extraction of objects of interest from the imagery. In order to calculate accurate RCS data of each object on the turntable, an area within the ISAR image was assigned to each object for every image formed during a full rotation. This area was tracked as it traveled 360 degrees enabling the generation of polar plots of RCS. This was done at multiple depression angles to capture the linear co- and cross-polarized signatures. The measured objects include a large metal cube, a chain link fence and a 1.5-in. diameter wound-metal cable.

We present a 220 GHz imaging radar prototype that has been developed in the European Defense Agency (EDA) project TIPPSI. The purpose of the development was to demonstrate short-range high-resolution 3D imaging for security applications at checkpoints, and to guide the development of stand-off real-time millimeter wave and sub-millimeter wave imaging systems for detection of larger objects at greater distances. An additional goal was to experimentally verify simulation techniques for active (sub)-mmw imaging systems, the verified simulation techniques can then be used to explore different system architectures. The 220 GHz imaging radar prototype consist of a flexible, mechanically scanned optical system that can support linear arrays of transmit/receive (TxRx) units up to 150 mm in length. The optical system is divided into two parts: A compact Dragonian system including the mechanical scanner that can be used as a stand-alone imager at reduced target distance and resolution, and a confocal system that can be added to achieve the full resolution of 1 cm x 1 cm x 1 cm at 4.5 m target distance. The field of view of the full resolution system is 70 cm x 70 cm. The front-end is currently populated by 4 TxRx units that are sparsely distributed along the 150 mm focal plane. The TxRx units operate in frequency modulated continuous wave (FMCW) mode and have a bandwidth of 24 GHz. Each TxRx unit use a single horn antenna and the transmit- and receive signals are generated and received using the same circuits which avoids the need of a duplexer. We will demonstrate high resolution 3D videos taken at 1 Hz frame rate and compare the individual images with simulations using electromagnetic simulators and character/clothes animation.

In this paper, a spotlight imaging system integrated with a frequency-diverse aperture is presented for security-screening applications. The spotlight imager consists of holographic metasurface antennas that can dynamically be tuned to radiate spotlight patterns allowing the extraction of high-resolution images from a constrained field-of-view (FOV). The reconfigurable holographic metasurface antennas consist of a metasurface layer used to modulate the guided-mode reference to an aperture field of interest producing the desired radiated wavefronts. The reconfigurable operation is achieved in an all-electronic manner without the need for any mechanical moving apparatus or phase shifting circuits. The spotlight aperture operates at a single frequency, 75 GHz, within the W-band frequency regime (75 – 110 GHz) and is used for the high-resolution identification of threat objects while the frequency-diverse aperture operates at K-band frequencies (17.5 – 26.5 GHz) and is used for low-resolution detection purposes. The scene to be imaged is first interrogated using the K-band aperture at low resolution and the constrained-FOV is imaged using the W-band system to achieve the identification of threat objects.

Microwave imaging systems have become increasingly prevalent owing to their ability to obtain 3D images while penetrating optically-opaque materials. These capabilities have motivated the development of various microwave imaging systems for applications ranging from security screening to biomedical imaging. Recent demonstrations have evidenced the idea that metasurface apertures can improve the hardware characteristics of microwave imaging systems due to their lightweight, low-cost, and planar nature. While metasurfaces can improve the antenna hardware, the large spectral bandwidth required for microwave imaging still incurs complex, costly, and performance-limiting RF components. To address the drawbacks inherent to using a large bandwidth, recent works have suggested that near-field microwave imaging can be performed at a single frequency point. In this work, monochromatic imaging is demonstrated by deploying two metasurface apertures to form a near-field microwave imaging system. By leveraging the unique radiation patterns emitted by metasurfaces, a pair of metasurface antennas, one acting as a transmitter and the other as a receiver, can acquire range and cross range information with measurements taken at a single frequency. We will show that this operation can then be supplemented by introducing aperture synthesis in the height direction to obtain fully 3D images. To account for the unusual illumination strategy, a reconstruction algorithm based on the range migration algorithm is formulated and implemented to enable efficient reconstruction of 3D images. Ultimately, the metasurface hardware, aperture synthesis, and monochromatic operation are combined to form an imaging system with high performance capabilities, without requiring complex and costly hardware.

The Pacific Northwest National Laboratory (PNNL) is engaged in the development of next-generation active cylindrical and planar millimeter-wave imaging systems that strive to have higher resolution and improved image fidelity relative to currently deployed systems. The principal method to evaluate the performance of potential imaging system designs has been to emulate them using single-channel radar transceivers that were raster-scanned using x-y scanners for planar scans, or an x-y scanner coupled to a turntable for cylindrical scans. This method has several drawbacks, including the necessity of having an available millimeter-wave transceiver and limiting scanning configurations to quasi-monostatic, uniformly sampled configurations. Modern designs may incorporate sparse, multi-static, sampling strategies, and may deviate from uniform sampling schemes. High-performance computers now allow realistic simulation of many imaging configurations, eliminating the need for such laboratory scanning to evaluate potential designs. In this paper, the use of a commercially-available shooting-and-bouncing-rays simulator for these applications is described and demonstrated with a number of imaging results.

We have completed a 16-channel 340 GHz 3D imaging radar for next-generation airport security screening under the European Union funded CONSORTIS (Concealed Object Stand-Off Real-Time Imaging for Security) project. The radar maps a 1 x 1 x 1 m³ sense volume with ~1 cm³ voxel resolution at multi-hertz frame rates. The radar has been installed in the CONSORTIS system enclosure and integrated with a passenger control system and command module. The full system will ultimately also incorporate a dual-band passive submillimeter wave imager and automatic anomaly detection software for reliable, ethical detection of concealed objects. A large data collection trial on targets of interest has been conducted to support the development of automatic anomaly detection software. Initial threat detection analysis indicates promising results against aviation-relevant objects including simulant dielectric threat materials.

For MW and MMW radar and radiometer measurements the influence of atmosphere like attenuation and path delay is more pronounced at higher frequencies. The sensors group of DLR Microwaves and Radar Institute operates the experimental radar System IoSiS (Imaging of satellites in space) at X band at the DLR ground station Weilheim in southern Germany. The radar images of the satellites in LEO (low earth orbit) are acquired in the ISAR mode (Inverse synthetic aperture radar) over a wide elevation angle of the steered Tx/Rx antenna. For the image processing and object focusing it is important to know the atmospheric attenuation and path delay variation over the wide synthetic aperture angle. The use of atmospheric models in order to retrieve the necessary parameters leads to some uncertainties since the models are mainly on a global scale and do not consider regional and seasonal conditions. Therefore the authors intend to refine an existing atmospheric model based on radiometric profiling measurements of the atmosphere for different weather conditions. The paper shows the measurement setup, mention briefly the Ulaby and ITU atmosphere models and show first experimental radiometer measurements of the atmospheric brightness temperature at four frequencies, namely at X, Ka, W and D band.

Commercial Advanced Imaging Technology (AIT) systems use arrays or synthetic arrays of millimeter wave antennas to generate holographic images and identify anomalies in those images that may present threats. In order to provide additional information for the AIT assessment, we are developing a technique that enables the identification of threat composition based on dielectric constant. The dielectric constant is extracted from the spectral content of the broadband holographic imaging data. The technique is demonstrated from images collected in a prototype personnel-screening system. The dielectric constant is obtained by numerically fitting the reflection coefficient as a function of frequency to an optical model. The reflection coefficient is a function of frequency because of propagation effects, such as multiple reflections and energy loss, that are associated with the material’s complex dielectric constant. In order to accomplish the analysis using an imaging system, the spectrum is obtained from an integration of the reflectivity image spectrum, which is an intermediate result in the image reconstruction algorithm. The present use of an imaging array demonstrates the ability to detect dielectric constant in small areas on a complex target. In principle, the implementation of this technique in standoff imaging systems would allow threat assessment to be accomplished within the scope of millimeter-wave screening.

First responders have the dangerous task of responding to emergency situations in firefighting scenarios involving homes and offices. The importance of the 77GHz radar and IR camera working together are their ability to see through walls and into adjacent areas to provide the first responder with information to assess the status of a building fire, its occupants, and to supplement his thermal camera which is obstructed by the wall. For the firefighter looking into an adjacent room containing unknown objects including humans, the challenge is to recognize what is in that room, the configuration of the room, and potential escape routes. The thermal camera has become an essential tool for the fireman to detect hot spots and the thermal signature of persons and objects within the room. We had previously concluded a series of experiments to illustrate the performance of 77GHz radar in building, fires and are continuing this research with a commercial thermal sensor. The experiments utilized the Delphi Automotive radar as the mm wave sensor, and a FLIR thermal sensor, together with display software developed by L. H. Kosowsky and Associates.

Highly precise signal generation technique is a key for the realization of low-noise radar and ghost-less imaging in millimeter-wave bands. Current technologies based on an oven-controlled oscillator has a better phase noise characteristic; however, relatively low frequency requires multiplication technique to upconvert the signal into millimeter-wave range. In the study, we configured an optoelectronic oscillator (OEO) employed with an optical frequency comb generation using an optical modulator. An optical filter bank implemented in the OEO loop performs an optical path optimization to realize 95-GHz millimeter-wave signal with a phase noise of -86 dBc/Hz at an offset frequency of 10 kHz.

Kinetic inductance bolometer (KIB) technology is a candidate for scalable submillimeter wave imaging systems, particularly suitable for person security screening applications. We have previously shown that the basic figures of merit are compatible with room-temperature radiometric imaging applications, and demonstrated the functionality of kilo-pixel detector arrays. In this article, we report on our imaging system based on 8208 KIBs organized on a 2D focal plane. We provide an overview on the basic components, including the detectors, optics, and cryogenics, and describe aspects relevant in system integration. Moreover, we demonstrate the capacity in actual concealed object detection by presenting datasets revealing metallic and dielectric objects hidden under the clothes of a test person.

Silicon-based integrated circuit technology provides a great platform for enabling compact, efficient, low-power, chipscale THz systems for new applications in sensing, imaging and communication. This is partially facilitated by scaling that has pushed device cut-off frequencies (f_t, f_max) up into the sub-THz and THz frequency range, the true paradigm shift in silicon integration is that it provides a unique opportunity to enable a field of active THz electromagnetics realizable through a circuits-EM-systems co-design approach. At these frequencies, the chip dimension is comparable to THz wavelengths which allows novel scattering and radiating properties in a substrate that simultaneously supports a billion high-frequency transistors that can generate, process and sense these signals. The ability to actively synthesize, manipulate and sense THz EM fields at sub-wavelength scales with circuits opens up a new design space for THz electronics. THz architectures emerging from this space are often multi-functional, reconfigurable and break many of the classical trade-offs of a partitioned design approach. This paper provides examples to illustrate this design methodology on THz signal generation with dynamic waveform shaping and THz spectrum sensing.

Advances in non-mechanical frequency-diverse apertures and reconstruction algorithms have made real-time millimeter-wave data acquisition and volumetric imaging possible. Fast frame rates allow imaging people in motion, which represents a tremendous opportunity to increase security screening throughput over existing solutions where subjects must individually strike and hold a pose. However for non-mechanical systems specularity coupled with limited viewing perspectives diminish coverage for individual images. To mitigate these issues, a system can leverage relative motion between the aperture and subject for a diversity of perspectives across several images. Such an image set offers overlapping and complementary swaths of subject coverage. By stitching together these images a composite image of the subject can be produced with much better overall coverage. Of course, people change shape as they move, which significantly complicates the image stitching registration and blending process. A deformable geometric model of a person suitable for real-time stitching is required. Drawing from the field of computer animation, we introduce a deformation model of a person based on Shape Key Deformation (SKD) and Skeletal Subspace Deformation (SSD). SKD blends shapes together, while SSD utilizes a simplified “skeleton” to guide deformation and modulate SKD. Assuming the pose of the skeleton is known, the deformation model is able to map any arbitrary image of a person onto a single rest image for stitching. The model is simple, fast, and robust. We go on to demonstrate image stitching of a simulated person in motion using software that models a massively multistatic MIMO metasurface computational imaging system.

Depth resolution and contrast (grayscale) resolution test objects have been proposed for incorporation into an ANSI standard for image quality of active millimeter wave (MMW) imagers for screening humans. A design for a depth resolution target has required the need for a thin film to generate a reflection while allowing for metal targets behind it to be visible to MMW imagers. Materials to accomplish this task have been identified, essentially acting as a millimeter wave beam splitter. Images obtained with a wide-bandwidth MMW imaging system are discussed. Additionally, by altering the resistivity of the thin film, the reflection coefficient of the film changes, allowing these films to be used as a contrast phantom for the testing of millimeter wave imaging systems. Measurements using laboratory millimeter wave systems are in good agreement with theory, and an image collected with a commercially-available MMW imaging systems is presented.

Millimeter waves imaging systems have many applications in medicine, communications, homeland security, and space technology. The advantages of MMW includes high penetrates thru almost every dielectric materials and no known ionization hazard for biological tissue, and low atmospheric scattering compared to infrared and optical rays. The Glow Discharge Detector (GDD) is a low cost room temperature MMW detector based on a commercial neon indicator lamp. Previously the GDD was proven to be very sensitive and inexpensive MMW radiation detector capable of direct and heterodyne radiation detection. Focal Plane Arrays (FPA) of GDD pixels were constructed and experimentally tested. In those experiments, the change in the DC bias current of the GDD was measured as function of the incidence MMW radiation. In this work the up-conversion of MMW radiation to visual light is demonstrated. By using a CCD/CMOS camera and GDD FPA a faster, more sensitive, and very inexpensive MMW and THz imaging system can be implemented. Also it is shown that by using the up converting method a real time 2D and 3D images can be obtained. 3D imaging system can provide the topography of the object plane in addition to intensity reflected from the image. Preliminary experimental results of an imaging system based on a unique quasi optical system, an 8×8 GDD's focal plane array (FPA), and a CCD camera is demonstrated. Also it is shown that the MMW images can be obtained in Real time.

Abstract—Main difference of radiometer in comparing with the receiving systems for the communication or the radar is noise character of the radiometric signal. Principal for the all receiving items is the attainment of the low noise parameters of system. According to classic theory it is principle for radiometer to expand the entrance band before the detector. In this case it is possible to reach more big value of the so named radiometric win, which is proportional to the square root from the multiplication of the entrance band with the time of a storage. For the case of the Josephson Junction (JJ) receiver we have principal peculiarity according to the own generation of the JJ, which can be conveniently used for the simple radiometric measuring or for the creation modern passive millimeter and terahertz imaging matrix system with electronic tuning of the receiving frequency band. Practically, JJ is the electronically monitoring mixer (correlator by math) without special heterodyne. It is better to consider JJ as a device with high nonlinearity to external electromagnetic radiation and meanwhile a device suitable as a local heterodyne signal generator. However, comparing with the traditional understanding of a local heterodyne (oscillator) such as a monochromatic generator in case of JJ, we have to deal with the reality of the noise heterodyne. Accordingly, this study presents the theoretical basis and calculation of the possible sensitivity in the radiometer (“pixel” in case of matrix) consisting in the JJ and IF amplifier in the radiometric regime. Figure 1. Schematic representation of the frequency conversation I.

Physical scale modeling of the electromagnetic backscatter behavior of static sea states using dielectric models and indoor compact radar ranges has the potential to offer a unique and advantageous method to probe ocean scattering phenomenology not feasible using conventional radar measurements on dynamic sea surfaces. As an initial step towards developing such modeling techniques, the millimeter-wave backscatter of a static, simplified rough surface made from a material that electromagnetically models the X-band dielectric properties of seawater has been measured. Computational electromagnetic modeling of the surface was performed using Xpatch and is compared with compact range measurements. By starting with simplified sea-state surfaces, the aim is to develop a reliable scale modeling approach capable of studying the backscattering behavior of realistic ocean surfaces.