This PDF file contains the front matter associated with SPIE Proceedings Volume 9830, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

We demonstrate a nondestructive electromagnetic-wave imaging system with a photonics-based W-band synthe- sizer, traveling-wave tube amplifier and focal-plane transistor array in real time manner. High-power amplifier with multi-watts output will enhance the quality of obtained images under transmission and reflection imaging configurations.

Optoelectronic methods are promising for rapid and highly reconfigurable beam steering across the microwave to the terahertz range. In particular, the photo-injected Fresnel zone plate antenna (piFZPA) offers high speed, wide angle, precise beam steering with good beam quality, to enable video rate millimeter wave imagery with no moving parts. We present a piFZPA demonstrator based on a commercial digital light projector (DLP) and high power laser which achieves steering rates up to 17,500 beams per second at 94 and 188 GHz. We also demonstrate radar imaging at 94 GHz at frame rates of 40 Hz (2D PPI) and 7 Hz (3D volumetric).

Imaging, Doppler, and spectroscopic radars from 95 to 700 GHz, all using the frequency-modulated continuous-wave technique, are in various stages of development for both defense and science applications at the Jet Propulsion Laboratory. For standoff security screening, a 340 GHz imaging radar now achieves an 8.3 Hz frame, and it has been tested using power-efficient MMIC-based active multiplier sources into its front end. That system evolved from a 680 GHz security radar platform, which has also been modified to operate in a Doppler mode for probing the dynamics of blowing sand and sensing small-amplitude target vibrations. Meanwhile, 95 and 183 GHz radars based on similar RF architectures are currently being developed to probe cometary jets in space and, using a differential absorption technique, humidity inside upper-tropospheric clouds.

A MIMO radar imaging system at 360 GHz is presented as a part of the comprehensive approach of the European FP7 project TeraSCREEN, using multiple frequency bands for active and passive imaging. The MIMO system consists of 16 transmitter and 16 receiver antennas within one single array. Using a bandwidth of 30 GHz, a range resolution up to 5 mm is obtained. With the 16×16 MIMO system 256 different azimuth bins can be distinguished. Mechanical beam steering is used to measure 130 different elevation angles where the angular resolution is obtained by a focusing elliptical mirror. With this system a high resolution 3D image can be generated with 4 frames per second, each containing 16 million points. The principle of the system is presented starting from the functional structure, covering the hardware design and including the digital image generation. This is supported by simulated data and discussed using experimental results from a preliminary 90 GHz system underlining the feasibility of the approach.

Since several years the use of active (radar) and passive (radiometer) MMW remote sensing is considered as an appropriate tool for a lot of security related applications. Those are personnel screening for concealed object detection under clothing, or enhanced vision for vehicles or aircraft, just to mention few examples. Radars, having a transmitter for scene illumination and a receiver for echo recording, are basically range measuring devices which deliver in addition information about a target’s reflectivity behavior. Radiometers, having only a receiver to record natural thermal radiation power, provide typically emission and reflection properties of a scene using the environment and the cosmic background radiation as a natural illumination source. Consequently, the active and passive signature of a scene and its objects is quite different depending on the target and its scattering characteristics, and the actual illumination properties. Typically technology providers are working either purely on radar or purely on radiometers for gathering information about a scene of interest. Rather rarely both information sources are really combined for enhanced information extraction, and then the sensor’s imaging geometries usually do not fit adequately so that the benefit of doing that cannot be fully exploited. Consequently, investigations on adequate combinations of MMW radar and radiometer data have been performed. A mechanical scanner used from earlier experiments on personnel screening was modified to provide similar imaging geometry for Ka-band radiometer and K-band radar. First experimental results are shown and discussed.

TeraSCREEN is an EU FP7 Security project aimed at developing a combined active, with frequency channel centered at 360 GHz, and passive, with frequency channels centered at 94, 220 and 360 GHz, imaging system for border controls in airport and commercial ferry ports. The system will include automatic threat detection and classification and has been designed with a strong focus on the ethical, legal and practical aspects of operating in these environments and with the potential threats in mind. Furthermore, both the passive and active systems are based on array receivers with the active system consisting of a 16 element MIMO FMCW radar centered at 360 GHz with a bandwidth of 30 GHz utilizing a custom made direct digital synthesizer. The 16 element passive receiver system at 360 GHz uses commercial Gunn diode oscillators at 90 GHz followed by custom made 90 to 180 GHz frequency doublers supplying the local oscillator for 360 GHz sub-harmonic mixers. This paper describes the development of the passive antenna module, local oscillator chain, frequency mixers and detectors used in the passive receiver array of this system. The complete passive receiver chain is characterized in this paper.

We present a 220 GHz 3D imaging ‘Pathfinder’ radar developed within the EU FP7 project CONSORTIS (Concealed Object Stand-Off Real-Time Imaging for Security) which has been built to address two objectives: (i) to de-risk the radar hardware development and (ii) to enable the collection of phenomenology data with ~1 cm³ volumetric resolution. The radar combines a DDS-based chirp generator and self-mixing multiplier technology to achieve a 30 GHz bandwidth chirp with such high linearity that the raw point response is close to ideal and only requires minor nonlinearity compensation. The single transceiver is focused with a 30 cm lens mounted on a gimbal to acquire 3D volumetric images of static test targets and materials.

In 2015, Asqella Oy commercialized a passive multi-band submillimeter-wave camera system intended for use in walk-by personnel security screening applications. In this paper we study the imagery acquired with the prototype of the ARGON passive multi-band submm-wave video camera. To challenge the system and test its limits, imagery has been obtained in various environments with varying background surface temperatures, with people of different body types, with different clothing materials and numbers of layers of clothing and with objects of different materials. In addition to the phenomenological study, we discuss the detection statistics of the system, evaluated by running blind trials with human operators. While significant improvements have been made particularly in the software side since the beginning of the testing, the obtained imagery enables a comprehensive evaluation of the capabilities and challenges of the multiband submillimeter-wave imaging system.

This paper will discuss the development of a millimeter-wave (mm-wave) receiver module used in a sparse array passive imaging system. Using liquid crystal polymer (LCP) technology and low power InP low noise amplifiers (LNA), enables the integration of the digital circuitry along with the RF components onto a single substrate significantly improves the size, weight, power, and cost (SWaP-C) of the mm-wave receiver module compared to previous iterations of the module. Also comparing with previous generation modules, the operating frequency has been pushed from 77 GHz to 95 GHz in order to improve the resolution of the captured image from the sparse array imaging system.

Millimeter-wave (mm-wave) imaging provides compelling capabilities for security screening, navigation, and bio- medical applications. Traditional scanned or focal-plane mm-wave imagers are bulky and costly. In contrast, phased-array hardware developed for mass-market wireless communications and automotive radar promise to be extremely low cost. In this work, we present techniques which can allow low-cost phased-array receivers to be reconfigured or re-purposed as interferometric imagers, removing the need for custom hardware and thereby reducing cost. Since traditional phased arrays power combine incoming signals prior to digitization, orthogonal code-modulation is applied to each incoming signal using phase shifters within each front-end and two-bit codes. These code-modulated signals can then be combined and processed coherently through a shared hardware path. Once digitized, visibility functions can be recovered through squaring and code-demultiplexing operations. Pro- vided that codes are selected such that the product of two orthogonal codes is a third unique and orthogonal code, it is possible to demultiplex complex visibility functions directly. As such, the proposed system modulates incoming signals but demodulates desired correlations. In this work, we present the operation of the system, a validation of its operation using behavioral models of a traditional phased array, and a benchmarking of the code-modulated interferometer against traditional interferometer and focal-plane arrays.

We propose a real-time algorithm of computer processing for the passive THz image with the aim of concealed object detection without looking through this image. The algorithm uses a correlation function between the THz image and a standard image. The sound alarm takes place if a correlation function value is greater than its certain value. This algorithm allows us to do a conclusion about presence of forbidden objects on the human body by using computer analysis.