This PDF file contains the front matter associated with SPIE Proceedings Volume 7837, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Simulated RF time-domain characteristics for advanced Gunn diodes with hot electron injection and sub-micron transit region lengths for use at frequencies over 100GHz are reported. The physical models used have been developed in SILVACO and are compared to measured results. The devices measured were originally fabricated to investigate the feasibility of GaAs Gunn diode oscillators capable of operating at D-band frequencies and ultimately intended for use in high power (multi-mW) Terahertz sources (~0.6THz) when used in conjunction with novel Schottky diode frequency multiplier technology. The device models created using SILVACO are described and the DC and time-domain results presented. The simulations were used to determine the shortest transit region length capable of producing sustained oscillation. The operation of resonant disk second harmonic Gunn diode oscillators is also discussed and accurate electromagnetic models created using Ansoft High Frequency Structure Simulator presented. Novel methods for combining small-signal frequency-domain electromagnetic simulations with time-domain device simulations in order to account for the significant interactions between the diode and oscillator circuit are described.

Millimeter-wave monolithic integrated circuit (MMIC) technology is now widely recognized as a key to many modern applications in safety and security, ranging from near and far-field imaging and sensing to non-invasive material inspection. In this paper, we apply our state-of-the-art MMIC technology to the analysis of gaseous media by spectroscopic techniques. The paper presents recent developments of amplifying and frequency-translating MMICs based on metamorphic HEMT technology and their application to the spectroscopic analysis of the frequency range from 250 to 330 GHz, including the important absorption line of water around 321 GHz.

We report on active imaging with CMOS transistors at 300 GHz and 1.05 THz. Two basic focal plane arrays consisting of nMOS transistors and wide-band bow-tie antennas have been implemented in a low-cost 130 nm CMOS technology. Raster scan imaging of objects concealed in a paper envelope has been achieved at 300 GHz with a commercial radiation source. The images clearly reveal the concealed objects with a dynamic range of 35 dB and a resolution of 3 mm. At 1.05 THz, the pixels achieve a responsivity of 50 V/W and a noise equivalent power of 900 pW/Hz^0.5.

High performance terahertz (THz) radiation sources hold great promise for a variety of military and space applications. With micro-electro-mechanical systems (MEMS) fabrication techniques, it is possible to attain the smaller, more precisely machined resonant structures required by Vacuum Electronic Devices (VEDs) to function in these frequencies. The research presented here proposes a design and fabrication process for a micro-klystron with a targeted operating frequency of 200 GHz; being developed jointly by Duke University, the University of Strathclyde, UK, and Logos Technologies. It also analyzes the use of a pseudospark (PS) discharge as a novel electron beam source to drive the klystron. Dimensional tolerances are investigated using both analytic and numeric techniques. The incorporation of alignment structures into the fabrication process that utilize kinematic and elastic averaging effects, along with clever stacking techniques, allows submicron alignment tolerances yielding an expected power output of approximately 5W per klystron with an overall efficiency of 20%. The device proposed here, with a volume on the order of 0.01 cc, should be capable of output power densities of up to 1kW/cc. A fabrication run recently completed at MIT's Microsystems Technology Laboratories yielded promising results and 32 silicon die were successfully bonded into a stack 1.4cm tall. Difficulties remain, however, in controlling surface roughness and integrating a klystron with alignment features for parallel processing. Several alternative fabrication schemes have been proposed and another fabrication run based on these modifications is currently underway.

Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable technological effort is being undertaken, in terms of technological development, THz device design and integration. The ultimate goal is to develop a miniaturised THz amplifier based on vacuum-tube principles The main target specifications of the OPTHER amplifier are the following: - Operating frequency: in the band 0.3 to 2 THz - Output power: > 10 mW ( 10 dBm ) - Gain: 10 to 20 dB. The project is in the middle of its duration. Design and simulations have shown that these targets can be met with a proper device configuration and careful optimization of the different parts of the amplifier. Two parallel schemes will be employed for amplifier realisation: THz Drive Signal Amplifier and Optically Modulated Beam THz Amplifier.

TowerJazz offers high volume manufacturable commercial SiGe BiCMOS technology platforms to address the mmWave market. In this paper, first, the SiGe BiCMOS process technology platforms such as SBC18 and SBC13 are described. These manufacturing platforms integrate 200 GHz f_T/f_MAX SiGe NPN with deep trench isolation into 0.18μm and 0.13μm node CMOS processes along with high density 5.6fF/μm² stacked MIM capacitors, high value polysilicon resistors, high-Q metal resistors, lateral PNP transistors, and triple well isolation using deep n-well for mixed-signal integration, and, multiple varactors and compact high-Q inductors for RF needs. Second, design enablement tools that maximize performance and lowers costs and time to market such as scalable PSP and HICUM models, statistical and Xsigma models, reliability modeling tools, process control model tools, inductor toolbox and transmission line models are described. Finally, demonstrations in silicon for mmWave applications in the areas of optical networking, mobile broadband, phased array radar, collision avoidance radar and W-band imaging are listed.

The properties of terahertz (THz) radiation are well known. They penetrate well most nonconducting media; there are no known biological hazards, and atmospheric attenuation and scattering is lower than for visual and IR radiation. Recently we have found that common miniature commercial neon glow discharge detector (GDD) lamps costing typically about 30 cents each exhibit high sensitivity to THz radiation, with microsecond order rise times, thus making them excellent candidates for such focal plane arrays. Based on this technology we designed, built and tested 4X4 and 8X8 GDD focal plane arrays. A line vector of 32 GDD pixels is being designed in order to increase the number of pixels in such arrays and thus the image resolution. Unique large aperture quasi optic mirrors were design and tested experimentally in this work. A new technology of light weight large aperture mirrors is proposed in this work. In this case a metal coating on plastic substrate is demonstrated. According to first experiments this technology proves to reliable with minimal deformation in LAB conditions. THz Images at 100 GHz were taken using this new inexpensive technology with good quality and resolution.

The potential of terahertz technology has been clearly demonstrated by its large applications in security and defence (remote detection of object). A flexible alternative monochromatic millimeter wave system coupled with an original infrared temperature sensor has been developed to visualize large size 3D manufactured opaque phantoms with different refractive index contrasts. The results clearly illustrate applied terahertz tomography particularities such as boundary effects, refraction and diffraction losses that must be prevented for efficient inspection and detection.

Uncooled antenna-coupled microbolometer focal plane arrays have been specifically tailored for optimum performance in the 1-5 Terahertz range. A prototyping batch of 160 × 120 pixel chips has been designed and then processed above 8" silicon substrates. An actively illuminated system has been experimentally tested where Quantum Cascade Lasers (QCLs) are associated with the room-temperature operating 2D sensor. Whereas explosives samples were introduced in the THz beam optical path, the profile of the modified beam has been sensed by a unique pixel translated via an X-Y stage. These represent the first demonstration essays of explosive identification using our system.

Increasing terroristic attacks raise the danger to the public and create a new and more complex dimension of threat. This evolution must and can only be combat by the application of new counter-measures like advanced imaging technologies for wide-area surveillance and the detection of concealed dangerous objects. Passive microwave remote sensing allows a daytime independent non-destructive observation and examination of the objects of interest under nearly all weather conditions. The acquisition of polarimetric object characteristics can increase the detection capability by gathering complementary object information. Over years the DLR Microwaves and Radar Institute developed several problem-orientated radiometer imaging systems covering nearly the whole frequency spectrum between 1 GHz and 100 GHz for a multitude of applications. Actually a fully-polarimetric radiometer receiver at W band is developed in order to explore the polarimetric information content of interesting objects simultaneously. Some important theoretical characteristics of polarimetric radiometry at millimeterwaves are introduced and discussed. The actual design and construction of the receiver system is outlined and first experimental imaging results are presented.

In this paper, the design and implementation of a sub-millimeter line scanning imager using a novel imageforming device is described. The system consists of a coherent illuminator, an optical system, an image plane mask, and a coherent detector. The image plane mask is formed by making a sequence of holes along a constant radius of a metal disk. Spinning the disk scans the holes through the image formed on it. A detector placed behind the spinning disk collects radiation passing through the holes. The holes are arranged in a pseudorandom pattern. At each detector sample time, energy from a different pattern of holes is collected. A rigorous electromagnetic analysis shows that, for a certain minimum size and spacing of holes and certain disk thicknesses, these measurements constitute a linear measurement of the energy in the image formed on the disk. Using techniques reminiscent of those used in compressive sensing, the image is then reconstructed by applying an inverse linear matrix transform to these measurements. We show how simulation can be used to optimize the design of the disk. We demonstrate a laboratory version of this device and discuss future efforts to systematize it. Extensions to full two-dimensional imaging are also discussed.

The low attenuation of millimeter-wave radiation propagating through sandstorms has created an interest in using millimeter-wave imagers in desert environments. The ground in desert environments can have significant differences in polarization properties depending on the angle of observation. Perturbations to the natural desert surface will change these polarization properties and by using a polarization difference technique these changes are highlighted. This technique has been applied to millimeter-wave images from a desert environment for several different objects including holes in the ground, footsteps, and changes to the surface created by digging.

The Scanning Polarimetric Imaging Radiometer (SPIRA) is a passive microwave imaging system operating around 91 GHz. It consists of a two orthogonally polarized receiver channels and an analog adding correlator network with 2 GHz bandwidth, which can measure all four Stokes parameters simultaneously by scanning the scene with an offset parabolic reflector on an elevation over azimuth scanner. In October 2008 the SPIRA instrument has participated in the joint Swiss-German Radiometer Experiment Thun where it has been operated in parallel with two PMMW systems of Fraunhofer Institut fur Hochfrequenzphysik und Radartechnik and an IR camera. During this measurement campaign different camouflage kits, vehicles and persons with hidden threats have been observed together with reference objects. This paper gives an overview of the three different instruments and discusses selected images of the joint measurement campaign.

The method of THz spectrum dynamics analysis (SDA - Spectral dynamics analysis - method) is applied for the detection and identification of substances by using the signal reflected from sample. It allows to obtain the spectrogram - composite Fourier spectrum dynamics - of the signal and to analyze the dynamics of many spectral lines simultaneously, even if the measurements are made on short time interval (less than 50 ps). The efficiency of the SDA method used for longer time intervals (more than 100 ps) is discussed also. The Fourier-Gabor sliding window method is used for obtaining the spectrogram. We consider the examples of finding selected explosives and harmless materials in pellets by using a THz pulse reflected from them. A THz pulse with a few cycles falls on the sample and reflects from it. The receiver makes the discrete measurements of electric field strength of signal reflected from the sample. To restore the signal to the required accuracy the SVD - Single Value Decomposition - technique is used. Our investigations show that the spectrograms and dynamics of several spectral lines of the THz pulse reflected differ from the corresponding spectrograms and dynamics of spectral lines for the reference pulse and hence it is possible to detect the presence of the material in the sample of interest. The efficiency of using the SDA method for identification of a substance by a THz pulse reflected from the sample is discussed and a comparison with an efficiency of applying the SDA method for the identification of substance by analysis of the pulse transmitted through the sample.

We report on our initial results of passive, real-time imaging in the Q-band using a distributed aperture and optical upconversion. The basis of operation is collection of incident mmW radiation by the distributed aperture, as embodied by an array of horn antennas, which is then amplified and upconverted to optical frequencies using commercially available electro-optic modulators. The non-linear mixing of the modulators creates sidebands containing the mmW signal with both amplitude and phase preserved. These signals are relaunched in the optical domain with a homothetic mapping of the antenna array. The optical carrier is stripped via dielectric stack filters and imagery is synthesized from the sidebands using the Fourier transform properties of a simple lens. This imagery is collected using a standard nearinfrared camera with post-processing to enhance the signal of interest and reduce noise. Details of operation and presentation of sample imagery is presented herein.

The first passive millimetre wave (PMMW) imagery is presented from two proof-of-concept aperture synthesis demonstrators, developed to investigate the use of aperture synthesis for personnel security screening and all weather flying at 94 GHz, and satellite based earth observation at 183 GHz ^[1]. Emission from point noise sources and discharge tubes are used to examine the coherence on system baselines and to measure the point spread functions, making comparisons with theory. Image quality is examined using near field aperture synthesis and G-matrix calibration imaging algorithms. The radiometric sensitivity is measured using the emission from absorbers at elevated temperatures acting as extended sources and compared with theory. Capabilities of the latest Field Programmable Gate Arrays (FPGA) technologies for aperture synthesis PMMW imaging in all-weather and security screening applications are examined.

We will present the continued development of a millimeter-wave/sub-THz radar system used to capture and assess micro-Doppler signatures of humans. This system is being developed to remotely monitor respiration and heartbeat rates at standoff distances of up to 100 meters. We will discuss the latest hardware and software developments and recent studies of the performance of the system under a variety of conditions.

We report on measurement of transmission spectra of commonly used explosives (RDX, PETN, HMX) covered by popular materials: paper, polyester and cotton in THz range (0.3-2.5 THz). Explosives were prepared as pellets, where Teflon was applied as the matrix material. We made use of Time Domain Spectroscopy and Fourier Transform Infrared Spectroscopy, which are described and results are compared. We show that characteristic features of explosives can be still identified up to 2.0 THz.

This paper discusses a practical and affordable approach to the accurate calibration of electronic beam-forming passive millimetre-wave imagers. With the aim of calibrating imagers with radiometric sensitivities ΔT < 1 K, we have constructed a thermal radiation source at ambient temperature that fills the imager field-of-view at close range and can support several controllable thermal radiation sources to provide absolute and differential radiation temperature standards. Using a variety of temperature sensors, which have been extensively cross-calibrated against each other and a commercially provided calibration standard that is accurate to < 0.1 K, we have achieved absolute and relative calibration temperature uncertainties of less than 0.25 K.

This paper gives an overview about a new security concept on airports. Because single systems have not often the desired reliability, the concept is based on the fusion of different sensors. Moreover, first measurements of a 94 GHz person scanner with circular synthetic aperture are presented showing the capability to detect metallic as well as nonmetallic objects without violating the personal privacy.