New theoretical results for noise in cryogenic bolometers are derived. Johnson noise is reduced by as much as 60% by electrothermal feedback from the bias supply. Phonon noise in the thermal link is reduced by as much as 30% relative to the usual equilibrium formula. Photon noise in the Rayleigh-Jeans limit is computed with attention to the attenuation of the photon correlations in the light beam. Basic results on bolometer responsivity, time constant, and thermal properties are presented in a new and convenient form. Excess 1/f and contact shot noise are also discussed.

Bolometer noise: nonequilibrium theory

A high-resolution imaging system based on the combination of ultrawideband (UWB) transmission, multiple-input-multiple-output (MIMO) array, and synthetic aperture radar (SAR) is suggested and studied. Starting from the resolution requirements, spatial sampling criteria for nonmonochromatic waves are investigated. Exploring the decisive influence of the system's fractional bandwidth (instead of previously claimed aperture sparsity) on the imaging capabilities of sparse aperture arrays, a MIMO linear array is designed based on the principle of effective aperture. For the antenna array, an optimized UWB antenna is designed allowing for distortionless impulse radiation with more than 150% fractional bandwidth. By combining the digital beamforming in the MIMO array with the SAR in the orthogonal direction, a high-resolution 3-D volumetric imaging system with a significantly reduced number of antenna elements is proposed. The proposed imaging system is experimentally verified against the conventional 2-D SAR under different conditions, including a typical concealed-weapon-detection scenario. The imaging results confirm the correctness of the proposed system design and show a strong potential of the MIMO-SAR-based UWB system for security applications.

A Sparse Aperture MIMO-SAR-Based UWB Imaging System for Concealed Weapon Detection

A 1 k-pixel camera chip for active terahertz video recording at room-temperature has been fully integrated in a 65-nm CMOS bulk process technology. The 32 × 32 pixel array consists of 1024 differential on-chip ring antennas coupled to NMOS direct detectors operated well-beyond their cutoff frequency based on the principle of distributed resistive self-mixing. It includes row and column select and integrate-and-dump circuitry capable of capturing terahertz videos up to 500 fps. The camera chip has been packaged together with a 41.7-dBi silicon lens (measured at 856 GHz) in a 5 × 5 × 3 cm3 camera module. It is designed for continuous-wave illumination (no lock-in technique required). In this video-mode the camera operates up to 500 fps. At 856 GHz it achieves a responsivity Rv of about 115 kV/W (incl. a 5-dB VGA gain) and a total noise equivalent power (NEPtotal) of about 12 nW integrated over its 500-kHz video bandwidth. At a 5-kHz chopping frequency (non-video mode) a single pixel can provide a maximum responsivity Rv of 140 kV/W (incl. a 5-dB VGA gain) and a minimum noise equivalent power ( NEP) of 100 pW/√Hz at 856 GHz. The wide-band antenna and pixel design achieves a 3-dB bandwidth of at least 790-960 GHz.

A 1 k-Pixel Video Camera for 0.7–1.1 Terahertz Imaging Applications in 65-nm CMOS

Well-defined high resolution structures with excellent electrical conductivities are key components of almost every electronic device. Producing these by printing metal based conductive inks on polymer foils represents an important step forward towards the manufacturing of plastic electronic products on an industrial scale. The development of fast, efficient and inexpensive post-deposition sintering technologies for these materials is an important processing step to make this approach commercially viable. This review discusses the advances in alternative sintering approaches for conductive, metal containing inks, which can be processed by inkjet-printing processes. Each sintering approach is examined regarding its mechanism, its compatibility with commonly used materials in the field of flexible electronics, its compatibility with high-throughput manufacturing processes and its applicability to the production of flexible electronic devices.

Progress of alternative sintering approaches of inkjet-printed metal inks and their application for manufacturing of flexible electronic devices

The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the improved techniques and discoveries in quantum mechanics steadily reduced the uncertainty of h. The central part of this review describes the technical details of the watt balance technique, which is a combination of the mechanical and electronic measurements that now determine h as a direct result, i.e. not requiring measured values of additional fundamental constants. The first technical section describes the basics and some of the common details of many watt balance designs. Next is a review of the ongoing advances at the (currently) seven national metrology institutions where these experiments are pursued. A final summary of the recent h determinations of the last two decades shows how history keeps repeating itself; there is again a question of whether there is a shift in the newest results, albeit at uncertainties that are many orders of magnitude less than the original experiments. The conclusion is that there is room for further development to resolve these differences and find new ideas for a watt balance system with a more universal application. Since the next generation of watt balance experiments are expected to become kilogram realization standards, the historical record suggests that there is yet a need for proof that Planck constant results are finally reproducible at an acceptable uncertainty.

https://iopscience.iop.org/article/10.1088/0034-4885/76/1/016101/pdf

History and progress on accurate measurements of the Planck constant

The Apollo research project is aimed at developing a prototype of an intelligent tyre. The overall goals are to increase traffic safety and enable improvements in vehicle dynamics control, advanced driver assistance systems and services for external users by providing data on the tyre and the local tyre-to-road contact.

A tyre sensor system with electronics for data transmission and power supply

Disclosed is an imaging apparatus. The imaging apparatus comprises a mirror arrangement, optics, and a detector arrangement comprising a plurality of detectors. The plurality of detectors is arranged within a region defined by an outer periphery and an inner periphery of the detector arrangement. The outer and inner peripheries are substantially circular in shape.

Imaging apparatus for monitoring objects

Passive, video-rate THz imaging system for stand-off security screening

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.

Phenomenology of passive multi-band submillimeter-wave imagery

This publication discloses an apparatus and method for reading an electronic code The apparatus comprises means for generating an alternating-electricity signal (2), electrodes (4, 5) connected to the alternating-electricity signal generating means (2) for bringing the alternating-electricity signal to the code (11) being read, and means for measuring the current travelling through the electrodes (4, 5) or the voltage between them According to the invention, the electrodes (4, 5) are open, without an insulator layer, and the means for generating an alternating-electricity signal (2) are such that they generate an alternating-electricity signal of at least 1 MHz

Anssi Rautiainen

Papers

A tyre sensor system with electronics for data transmission and power supply

Imaging apparatus for monitoring objects

Passive, video-rate THz imaging system for stand-off security screening

Phenomenology of passive multi-band submillimeter-wave imagery

Method and apparatus for detecting an electric code