This PDF file contains the front matter associated with SPIE Proceedings Volume 8715, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

This paper presents a pre-amplified detector receiver based on a 250 nm InP/InGaAs/InP double heterojunction bipolar transistor (DHBT) process available from the Teledyne scientific. The front end consists of a double slot antenna followed by a five stage low noise amplifier and a detector, all integrated onto the same circuit. Results of measured responsivity and noise are presented. The receiver is characterized through measuring its response to hot (293) and cold (78) K terminations. Measurements of the voltage noise spectrum at the video output of the receiver are presented and can be used to derive the temperature resolution of the receiver for a specific video bandwidth.

This paper presents the design and measured results of a highly integrated silicon-based receiver chip for W-band imaging applications. The receiver chip integrates all necessary RF and analog functions including millimeter-wave amplification and power detection, baseband amplification, sample-and-hold, clock generation, imager calibration, bias generation, and digital control. Using a novel flicker-noise cancellation technique, the imaging receiver achieves a record NETD of 0.22K/0.15K/0.1K for 3ms/10ms/30ms integration time, and a responsivity of 140 MV/W. The chip is fabricated in a 0.18-µm SiGe BiCMOS technology with 240/280-GHz f_T/f_max and occupies 2.5mm×2.5mm. The power dissipation of the receiver is 40 mW.

In this paper, we report on the highest speed 240GHz/340GHz F_T/F_MAX NPN which is now available for product designs in the SBC18H4 process variant of TowerJazz’s mature 0.18μm SBC18 silicon germanium (SiGe) BiCMOS technology platform. NFMIN of ~2dB at 50GHz has been obtained with these NPNs. We also describe the integration of earlier generation NPNs with F_T/F_MAX of 240GHz/280GHz into SBC13H3, a 0.13μm SiGe BiCMOS technology platform. Next, we detail the integration of the deep silicon via (DSV), through silicon via (TSV), high-resistivity substrate, sub-field stitching and hybrid-stitching capability into the 0.18μm SBC18 technology platform to enable higher performance and highly integrated product designs. The integration of SBC18H3 into a thick-film SOI substrate, with essentially unchanged F_T and F_MAX, is also described. We also report on recent circuit demonstrations using the SBC18H3 platform: (1) a 4-element phased-array 70-100GHz broadband transmit and receive chip with flat saturated power greater than 5dBm and conversion gain of 33dB; (2) a fully integrated W-band 9-element phase-controllable array with responsivity of 800MV/W and receiver NETD is 0.45K with 20ms integration time; (3) a 16-element 4x4 phased-array transmitter with scanning in both the E- and H-planes with maximum EIRP of 23-25 dBm at 100-110GHz; (4) a power efficient 200GHz VCO with -7.25dBm output power and tuning range of 3.5%; and (5) a 320GHz 16-element imaging receiver array with responsivity of 18KV/W at 315GHz, a 3dB bandwidth of 25GHz and a low NEP of 34pW/Hz1/2. Wafer-scale large-die implementation of the phased-arrays and mmWave imagers using stitching in TowerJazz SBC18 process are also discussed.

We present results of experimental characterization of static 650-GHz reflectarrays. The reflectarrays are based on 123-μm circular microstrip patch antennas with tuning stubs as phase shifters. The static reflectarrays are considered as predecessors for active reflectarrays, and therefore the reflectarray elements have two discrete phase-shift values: 0° and -180°. The reflectarrays have 95000 elements, and they have separation of 400 μm. The reflectarrays are fabricated on 150-mm silicon wafers with a ground plane and a 20-μm polyimide substrate atop. The fabricated static reflectarrays are characterized in a near-field measurement range and their beam patterns at the focusing distance of 20 m are calculated with plane-to-plane transform. At this high frequency, fabrication tolerances are difficult to meet and, e.g., over-etching of the antenna and phase-shifting structure may offset the resonance frequency of the reflectarray element by more than its bandwidth.

As terrestrial remote sensing and communication systems continue to evolve in the 0.1 – 0.3 THz band, the need to understand the scattering behavior of common materials and ground terrain at these frequencies becomes important. Terrain features and surface roughness that would otherwise appear smooth at longer wavelengths begin to significantly impact the radar cross section of the surfaces at these higher frequencies. The HH and VV polarized backscattering coefficient of several types of ground terrain and building materials were measured in indoor compact radar ranges operating at 100 GHz and 240 GHz. Measurements of the various materials were collected at elevation angles ranging from 5 to 35 degrees. The goal of the effort was to develop a better understanding of the polarimetric scattering behavior of materials in the 0.1–0.3 THz region.

Optical upconversion for a distributed aperture millimeter wave imaging system is highly beneficial due to its superior bandwidth and limited susceptibility to EMI. These features mean the same technology can be used to collect information across a wide spectrum, as well as in harsh environments. Some practical uses of this technology include safety of flight in degraded visual environments (DVE), imaging through smoke and fog, and even electronic warfare. Using fiber-optics in the distributed aperture poses a particularly challenging problem with respect to maintaining coherence of the information between channels. In order to capture an image, the antenna aperture must be electronically steered and focused to a particular distance. Further, the state of the phased array must be maintained, even as environmental factors such as vibration, temperature and humidity adversely affect the propagation of the signals through the optical fibers. This phenomenon cannot be avoided or mitigated, but rather must be compensated for using a closed-loop control system. In this paper, we present an implementation of embedded electronics designed specifically for this purpose. This novel architecture is efficiently small, scalable to many simultaneously operating channels and sufficiently robust. We present our results, which include integration into a 220 channel imager and phase stability measurements as the system is stressed according to MIL-STD-810F vibration profiles of an H-53E heavy-lift helicopter.

Active millimeter-wave imaging is currently being used for personnel screening at airports and other high-security facilities. The cylindrical imaging techniques used in the deployed systems are based on licensed technology developed at the Pacific Northwest National Laboratory. The cylindrical and a related planar imaging technique form three-dimensional images by scanning a diverging beam swept frequency transceiver over a two-dimensional aperture and mathematically focusing or reconstructing the data into three-dimensional images of the person being screened. The resolution, clothing penetration, and image illumination quality obtained with these techniques can be significantly enhanced through the selection of the aperture size, antenna beamwidth, center frequency, and bandwidth. The lateral resolution can be improved by increasing the center frequency, or it can be increased with a larger antenna beamwidth. The wide beamwidth approach can significantly improve illumination quality relative to a higher frequency system. Additionally, a wide antenna beamwidth allows for operation at a lower center frequency resulting in less scattering and attenuation from the clothing. The depth resolution of the system can be improved by increasing the bandwidth. Utilization of extremely wide bandwidths of up to 30 GHz can result in depth resolution as fine as 5 mm. This wider bandwidth operation may allow for improved detection techniques based on high range resolution. In this paper, the results of an extensive imaging study that explored the advantages of using extremely wide beamwidth and bandwidth are presented, primarily for 10-40 GHz frequency band.

The Jet Propulsion Laboratory (JPL) is developing compact transceiver arrays housing discrete GaAs Schottky diodes with integrated waveguides in order to increase the frame rate and lower the cost of active submillimeter-wave imaging radar systems. As part of this effort, high performance diode frequency multiplier and mixer devices optimized for a 30 GHz bandwidth centered near 340 GHz have been fabricated using JPL’s MoMeD process. A two-element array unit cell was designed using a layered architecture with three-dimensional waveguide routing for maximum scalability to multiple array elements. Prototype two-element arrays have been built using both conventionally machined metal blocks as well as gold-plated micromachined silicon substrates. Preliminary performance characterization has been accomplished in terms of transmit power, and conversion loss, and promising 3D radar images of concealed weapons have been acquired using the array.

Personnel screening is demanded nowadays for securing air traffic as well as critical infrastructures. The millimeter-waves are able to penetrate clothes and detect concealed objects, making them an attractive choice for security screening. Imaging methods based on multistatic architecture can ensure high quality imagery in terms of resolution and dynamic range. Following the advances in semiconductor technology, fully electronic solutions delivering real-time imaging are becoming feasible. Furthermore, the continuously increasing capabilities of digital signal processing units allow for the utilization of digital-beamforming techniques for image reconstruction, thus offering new opportunities for imaging systems to use sophisticated operation modes. Based on these modern technologies, an advanced realization addressing personnel screening in E-band with planar multistatic sparse array design is demonstrated.

This paper describes a study performed at the Pacific Northwest National Laboratory which investigated the use of active millimeter-wave radar imaging to perform threat detection in non-divested shoes. The purpose of this study was to determine the optimal imaging system configuration for performing this type of task. While active millimeter-wave imaging systems have proven to be effective for personnel screening, the phenomenology associated with imaging within a heterogeneous medium, such as a shoe, dictates limits for imaging system parameters. Scattering, defocusing, and multipath artifacts are significantly exaggerated due to the high contrast index of refraction associated with the boundary at the air and shoe interface. Where higher center-frequency and bandwidth result in much improved lateral and range resolution in the body scanning application, smaller wavelengths are significantly defocused after penetrating the sole of the shoe. Increased bandwidth, however, is essential for the shoe scanning application as well. Obtaining fine enough depth resolution is critical in separating the scattering contribution of each layer of the shoes in range to isolate possible threats embedded within the sole. In this paper, the results of a study to optimize the following imaging system parameters are presented: antenna illumination beamwidth, antenna polarization, transceiver bandwidth, and physical scanning geometry.

Passive Millimeter Wave Imaging for detection of concealed contraband has been demonstrated for decades in various forms. One vexing problem is that when some emissive materials reach body temperature they lose contrast. A solution to this problem, along with results of an implementation, is presented.

Passive submillimeter wave imaging is a concept that has been in the focus of interest as a promising technology for security applications for a number of years. It utilizes the unique optical properties of submillimeter waves and promises an alternative to millimeter-wave and X-ray backscattering portals for personal security screening in particular. Possible application scenarios demand sensitive, fast, and fleixible high-quality imaging techniques. Considering the low radiometric contrast of indoor scenes in the submillimeter range, this objective calls for an extremely high detector sensitivity that can only be achieved using cooled detectors. Our approach to this task is a series of passives standoff video cameras for the 350 GHz band that represent an evolving concept and a continuous development since 2007. The cameras utilize arrays of superconducting transition-edge sensors (TES), i.e. cryogenic microbolometers, as radiation detectors. The TES are operate at temperatures below 1K, cooled by a closed-cycle cooling system, and coupled to superconducting readout electronics. By this means, background limited photometry (BLIP) mode is achieved providing the maximum possible signal to noise ratio. At video rates, this leads to a pixel NETD well below 1K. The imaging system is completed by reflector optics based on free-form mirrors. For object distances of 3–10m, a field of view up to 2m height and a diffraction-limited spatial resolution in the order of 1–2cm is provided. Opto-mechanical scanning systems are part of the optical setup and capable frame rates up to 25 frames per second. Both spiraliform and linear scanning schemes have been developed.

Stand-off detection for concealed weapons is one of the applications for passive submillimetre-wave imaging. The operating frequency (neglecting technology limitations) is often a compromise between the diffraction-limited angular resolution for a fixed maximum aperture diameter, and the extinction of the signal in obscurant layers: At high frequencies towards the 1 THz mark, excellent angular resolution is readily achievable with modest aperture diameters, while scattering and attenuation by clothing is high which creates potentially more clutter rather than improving detection capability. At lower frequencies towards 100 GHz, attenuation and scattering by clothing is much less pronounced, albeit at significantly reduced spatial definition thanks to increased diffraction. In order to avoid the above-mentioned compromise, we have constructed a three-band passive imaging system operating at effective centre frequencies of 250 GHz, 450 GHz and 720 GHz. Aspects of the system will be presented.

We present a novel architecture based upon a Dicke-switched heterodyne radiometer architecture employing two identical input sections consisting of horn and orthomode transducer to detect the difference between the horizontal (H) and vertical (V) polarization states of two separate object patches imaged by the radiometer. We have constructed and described previously a fully polarimetric W-band passive millimeter wave imager constructed to study the phenomenology of anomaly detection using polarimetric image exploitation of the Stokes images. The heterodyne radiometer used a PIN diode switch between the input millimeter wave energy and that of a reference load in order to eliminate the effects of component drifts and to reduce the effects of 1/f noise. The differential approach differs from our previous work by comparing H and V polarization states detected by each of two input horns instead of a reference load to form signals ΔH and ΔV from adjacent paired object patches. This novel imaging approach reduces common mode noise and enhances detection of small changes between the H and V polarization states of two object patches, now given as difference terms of the fully polarimetric radiometer. We present the theory of operation, initial proof of concept experimental results, and extension of the differential radiometer to a system with a binocular fore optics that allow adjustment of the convergence or shear of the object patches as viewed by the differential polarimetric imager.

For many military or peace-keeping operations it is necessary to provide better situational awareness to the commander of a vehicle with respect to possible threats in his local environment (predominantly ahead), at a distance of a few ten to a few hundred meters. Such a challenging task can only be addressed adequately by a suitable multi-sensor system. As a beneficial part of that, an imaging radiometer system with a sufficiently high frame rate and field of view is considered. The radiometer, working 24 hours in all weather and sight conditions, generates quasi-optical images simplifying the microwave image interpretation. Furthermore it offers the advantage to detect and localise objects and persons under nearly all atmospheric obstacles and also extends the surveillance capabilities behind non-metallic materials like clothing or thin walls and thin vegetation. Based on constraints of low costs and the observation of a large field of view, the constructed radiometer still offers a moderate resolution at a moderate scan speed. This paper describes the challenges for the design of a vehicle-based imaging radiometer system at W band, providing high-quality images of sufficient resolution for a large field of view at a moderate frame rate. The construction is briefly outlined and imaging results for several situations are presented and discussed. Those comprise measurements on target detection and a visual comparison of different SUM (Surveillance in an Urban environment using Mobile sensors) data products.

Passive imaging using millimeter waves (mmWs) has many advantages and applications in the defense and security markets. All terrestrial bodies emit mmW radiation and these wavelengths are able to penetrate smoke, fog/clouds/marine layers, and even clothing. One primary obstacle to imaging in this spectrum is that longer wavelengths require larger apertures to achieve the resolutions desired for many applications. Accordingly, lens-based focal plane systems and scanning systems tend to require large aperture optics, which increase the achievable size and weight of such systems to beyond what can be supported by many applications. To overcome this limitation, a distributed aperture detection scheme is used in which the effective aperture size can be increased without the associated volumetric increase in imager size. This distributed aperture system is realized through conversion of the received mmW energy into sidebands on an optical carrier. This conversion serves, in essence, to scale the mmW sparse aperture array signals onto a complementary optical array. The side bands are subsequently stripped from the optical carrier and recombined to provide a real time snapshot of the mmW signal. Using this technique, we have constructed a real-time, video-rate imager operating at 75 GHz. A distributed aperture consisting of 220 upconversion channels is used to realize 2.5k pixels with passive sensitivity. Details of the construction and operation of this imager as well as field testing results will be presented herein.

These days passive microwave (MW) remote sensing has found many applications. For example, in Earth observation missions, it is possible to estimate the salinity of oceans, the soil moisture of landscapes, or to extract atmospheric parameters like the liquid water content of clouds [1, 2, 3]. Due to the penetration capabilities of microwaves through many dielectric materials, and the purely passive character of this kind of remote sensing, this technique nowadays is considered as well in many security and reconnaissance applications (e.g. observation of sensitive areas, detection of concealed objects, trough-wall imaging, etc.). Presently different imaging principles for MW radiometry are possible. Most of them still are based on pure mechanical scanning or they combine this with electronic scanning by using parts of a focal plane array [4]. Due to many advantages, the technological trend is going towards fully-electronic beam steering or two-dimensional focal plane arrays. These systems are able to achieve high frame rates, but they are still very expensive because of a significantly higher number of receiver modules, compared to a mechanical scanning system. In our approach a novel concept for a Ka band fully-electronic wide swath MW imaging radiometer system is introduced [5]. It is based on a combination of beam steering by frequency shift for one scanning direction using a slotted-waveguide antenna, and the application of aperture synthesis in the other. In the following a proof of concept is outlined using a two-element interferometer system called VESAS (Voll elektronischer Scanner mit Apertursynthese) demonstrator. The advantage of using the aperture synthesis technique is the possibility to implement minimal redundant sparse arrays without a degradation of the antenna pattern. In combination with the beam steering by frequency shift, one requires a one dimensional receiver/antenna array for a two dimensional imaging, hence a low-cost, fully-electronic wide swath microwave radiometer system with high frame rates is feasible. In the following a proof of concept is outlined by presenting different MW imaging measurement results, using this kind of imaging principle.

We present work on the development of a long range standoff concealed weapons detection system capable of imaging under very heavy clothing at distances exceeding 100 m with a cm resolution. The system is based off a combination of phased array technologies used in radio astronomy and SAR radar by using a coherent, multi-frequency reconstruction algorithm which can run at up to 1000 Hz frame rates and high SNR with a multi-tone transceiver. We show the flexible design space of our system as well as algorithm development, predicted system performance and impairments, and simulated reconstructed images. The system can be used for a variety of purposes including portal applications, crowd scanning and tactical situations. Additional uses include seeing through dust and fog.

We report on the use of the All-weather Volcano Topography Imaging Sensor (AVTIS) 94 GHz dual mode radar/radiometric imager for environmental monitoring. The FMCW radar yields 3D maps of the terrain whilst the passive radiometer records brightness temperature maps of the scene. AVTIS is a low power portable instrument and has been used operationally to survey terrain at ranges up to 6 km. AVTIS was originally developed for the ground-based measurement of active volcanoes and has been used successfully to measure the Arenal Volcano in Costa Rica and the Soufrière Hills Volcano on Montserrat. However, additional environmental remote sensing applications are emerging for this technology and we will present details of how the instrument is used to perform terrain mapping and thermal surveys of outdoor scenes. The extraction of digital elevation maps is the primary function of the AVTIS radar mode. We review this process covering range drift compensation, radar cross section (RCS) histogram analysis and thresholding, and georeferencing to GPS. Additionally, we will present how careful calibration enables RCS imaging of terrain and the extraction of the intrinsic reflectivity of the terrain material (normalized RCS, or sigma-nought) which can potentially be used to classify terrain types. We have validated the passive mode imagery against infrared thermal imagery and they show good agreement once the differences in spatial resolution are accounted for. This comparison also reveals differences in propagation due to obscurants (steam, gas, ash) in the two wavebands.

Security scanning using sub-millimeter wave 3D imaging radar maps the subsurface structure of subjects, revealing objects hidden under clothing. This requires a wide dynamic range to detect small targets near large ones and centimeter range resolution to resolve small objects. For radar designers this translates into requiring a very low phase noise source which maintains good chirp linearity over a very wide fractional bandwidth, and other researchers have highlighted these effects. We present an assessment of the phase noise and chirp nonlinearity in our IRAD 340 GHz 3D imaging radar and make comparisons of different source architectures and nonlinearity compensation schemes.

The tracking of missiles at close range proximity has been an ongoing challenge for many launch environments. The ability to provide accurate missile trajectory information is imperative for range safety and early termination of flight. In an effort to provide a potential solution to tracking issues that have plagued many traditional techniques, the Tracking Interferometer Pathfinder System (TIPS) was developed at the Naval Research Laboratory, Washington, D.C. The paper herein describes the design, field test, and results of an interferometer deployed for missile tracking.

We present details of our work which has been focused on improving the efficiency and scan rate of the photo-injected Fresnel zone plate antenna (piFZPA) technique which utilizes commercially available visible display technologies. This approach presents a viable low-cost solution for non-mechanical beam steering, suitable for many applications at (sub) mm-wave frequencies that require rapid beam steering capabilities in order to meet their technological goals, such as imaging, surveillance, and remote sensing. This method has the advantage of being comparatively low-cost, is based on a simple and flexible architecture, enabling rapid and precise arbitrary beam forming, and which is scalable to higher frame-rates and higher submm-wave frequencies. We discuss the various optimization stages of a range of piFZPA designs that implement fast visible projection displays, enabling up to 30,000 beams per second. We also outline the suitability of this technology across mm-wave and submm-wave frequencies as a low-cost and simple solution for dynamic optoelectronic beam steering.