340 GHz FMCW pulse-Doppler radar to characterize the dynamics of particle clouds

This is a document that will describe a 340 GHz pulse Doppler radar. It will describe the system and its performanc

220GHz wideband 3D imaging radar for concealed object detection technology development and phenomenology studies

Part of the research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 312745.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 & materials.Publisher PD

Confocal Ellipsoidal Reflector System for a Mechanically Scanned Active Terahertz Imager

We present the design of a reflector system that can rapidly scan and refocus a terahertz beam for high-resolution standoff imaging applications. The proposed optical system utilizes a confocal Gregorian geometry with a small mechanical rotating mirror and an axial displacement of the feed. For operation at submillimeter wavelengths and standoff ranges of many meters, the imaging targets are electrically very close to the antenna aperture. Therefore the main reflector surface must be an ellipse, instead of a parabola, in order to achieve the best imaging performance. Here we demonstrate how a simple design equivalence can be used to generalize the design of a Gregorian reflector system based on a paraboloidal main reflector to one with an ellipsoidal main reflector. The system parameters are determined by minimizing the optical path length error, and the results are validated with numerical simulations from the commercial antenna software package GRASP. The system is able to scan the beam over 0.5 m in cross-range at a 25 m standoff range with less than 1% increase of the half-power beam-width

A 220 GHz 3D imaging radar with sub-cm3 voxel resolution for security applications

Radars operating at high millimetre and sub-millimetre wave frequencies are promising candidates for security applications such as people screening since they offer the possibility to form 3D images through clothing with sufficient resolution to detect concealed objects. High spatial resolution of order 1 cm can be achieved using practically sized antennas and high range resolution can be achieved using wideband FMCW chirps, e.g. 30 GHz, to yield 0.5 cm range bins. We present a 220 GHz test-bed ‘Pathfinder’ radar which achieves sub-cm3 voxel resolution with very high signal fidelity. The radar is used to de-risk technology under development for next generation people screening systems.Postprin

A broadband heterostructure barrier varactor tripler source

We present the first demonstration of a broadband Heterostructure Barrier Varactor tripler, designed to cover a major part of the WR-8 waveguide band. The source comprises a waveguide housing, a six-barrier InP-HBV diode flip-chip mounted on an AlN microstrip filter circuit. The conversion loss 3-dB bandwidth was measured to 17 % at a center frequency of 112 GHz. The maximum output power was more than 15 mW for an input power of 300 mW. There are no mechanical tuners or DC-bias, which simplifies assembly and allows for ultra-compact design

Ueber die Behandlung der Geburt bei Atresie der Vagina

http://www.ester.ee/record=b3581049*es

Time-Delay Multiplexing of Two Beams in a Terahertz Imaging Radar

We demonstrate a time-delay multiplexing technique that doubles the frame rate of a 660–690-GHz imaging radar with minimal additional instrument complexity. This is done by simultaneously projecting two offset, orthogonally polarized radar beams generated and detected by a common source and receiver. Beam splitting and polarization rotation is accomplished with a custom designed waveguide hybrid coupler and twist. A relative time lag of approximately 2 ns between the beams’ waveforms is introduced using a quasi-optical delay line, followed by spatial recombination using a selectively reflective wire grid. This delay is much longer than the approximately 20-ps time-of-flight resolution of the 30-GHz bandwidth radar, permitting the two beams’ reflected signals from a compact target to be easily distinguished in digital post-processing of the single receiver channel

Bistatic noise radar: Demonstration of correlation noise suppression

In this study, spatial separation of the radar transmitter and receiver units is considered, as a means of reducing the masking effect in noise radars. A bistatic radar system is constructed, with emphasis on a lightweight transmitter unit that can be mounted on a commercial Unmanned Aerial Vehicle (UAV). The system uses pseudo-random noise, generated digitally at the receiver and transmitter units. Correlation losses, due to non-linearities in the transmitter and receiver units, are measured to 0.1\ua0dB. This study shows that by separating the transmitter and receiver unit the masking effect is significantly reduced, compared to a monostatic setup. This reduction is enough for the system to detect a slow flying UAV. Thus, bistatic separation should be considered as a practical tool to reduce the masking effect. By processing clutter with an extended CLEAN algorithm, the correlation noise floor is further suppressed

Implementation of a coherent real-time noise radar system

The utilisation of continuous random waveforms for radar, that is, noise radar, has been extensively studied as a candidate for low probability of intercept operation. However, compared with the more traditional pulse-Doppler radar, noise radar systems are significantly more complicated to implement, which is likely why few systems exist. If noise radar systems are to see the light of day, system design, implementation, limitations etc., must be investigated. Therefore, the authors examine and detail the implementation of a real-time noise radar system on a field programmable gate array. The system is capable of operating with 100% duty cycle, 200\ua0MHz bandwidth, and 268\ua0ms integration time while processing a range of about 8.5\ua0km. Additionally, the system can perform real-time moving target compensation to reduce cell migration. System performance is primarily limited by the memory bandwidth of the off-chip dynamic random access memory