High-resolution wideband electroencephalograph based on nanosensors

Conventional spaceborne SAR is limited by range and Doppler blur, so it cannot achieve simultaneous high-resolution wide mapping band. To solve this problem, this paper adopts the multi-channel ScanSAR technology scheme of azimuth-oriented multi-phase center bias combined with range beam scanning. The application of multi-channel system in ScanSAR operation mode can effectively make up for the defects of low azimuth-oriented resolution of conventional ScanSAR, so as to obtain high resolution wide mapping band. This paper describes the principle of multi-channel ScanSAR to realize high-resolution wide-band mapping, and proposes a multi-channel frequency domain reconstruction algorithm combined with full-aperture RD algorithm to realize multi-channel ScanSAR imaging. The effectiveness of the algorithm is verified by 7×7 lattice imaging simulation, which lays a foundation for the engineering implementation of high-resolution wide-band mapping SAR.

Cascade and multibit quantisation 1-bit feedback (NA/D1) noise shaping modulators are presently considered the most attractive topologies for implementing high resolution A/D convertors. This is because the cascade concept allows stable high order noise shaping modulators to be implemented easily, and because the NA/D1 architecture allows the amount of quantisation noise handled to be reduced while avoiding the disadvantages of using N-bit D/A convertors (N≥2). The work presented here proposes that cascade and multibit modulators should be seen as particular cases in a wider modulator architecture, here referred to as GaMeS. The design methodology proposed also permits several new modulators to be derived. All of them allow us to explore the three parameters in the design of an A/D convertor, which are the oversampling ratio, M, the noise shaping order, L, and the quantiser resolution, N. An analytical study is made of integrator gain and pole error effects in the SNR performance, as well as of nonidealities present in N-bit quantisers. Simulations made with a userfriendly and behavioural simulator we had developed, prove the correctness of the analyses made, and indicate that high resolution wideband A/D convertors can take advantage of these new topologies.

The design of transmitting waveforms is an effective way to improve the detection performance of sonar systems. For the problem of high-range sidelobe when designing reverberation-resistant waveforms, this paper proposes a high-resolution wideband composite waveform design with reverberation suppression performance and a waveform parameter improvement method. Firstly, we propose a novel wideband waveform, which utilizes linear frequency modulation (LFM) as the fundamental pulse, referred to as multi-parameter coded modulation LFM pulse (MPCM-LFM). Additionally, we deduce the wideband ambiguity function for waveform design. Then, we deduce the constraint relations of the waveform parameters for different sub-band overlaps, and according to the mathematical expressions of the obtained range ambiguity function, we analyze in detail the effects of the waveform parameters on the range ambiguity function under different constraints. Secondly, on the basis of the analysis, we also propose a hopping carrier frequency constraint rule to optimize the spectral performance, and the range sidelobe is restrained effectively in significant measure by this parameter improvement method. Finally, we analyze the computer simulation results. It is obvious that our proposed waveform parameter improvement method leads to good results. The proposed improved MPCM-LFM signal shows a “near-thumbtack” ambiguity function, whose sidelobe suppression performance is superior to other classical waveforms in the desired region, and it can realize high-precision parameter estimation. In addition, the proposed improved MPCM-LFM signal possesses good performance in detecting stationary and low Doppler targets in the background of reverberation.

High-resolution wideband digital channelizer is the key component for extraction and reconstruction of multichannel signals in software radio systems. It has been proved that complex-exponential modulated (CEM) perfect reconstruction (PR) filter-bank is an efficient structure for the wideband channelizer, in which the Parks-McClellan (PM) algorithm based design method for the PR prototype filter and PR filterbank is effective when the number of sub-channels is less than 1024. However, due to the limitation of the PM algorithm for the filters with extremely high-order or narrow transition band, it doesn't work well when the number of sub-channels increases further. In this paper, we propose an efficient design method for such high-order PR filterbanks, which is based on the classical Frequency Sampling (FS) method and the criterion of least mean square error (LMSE). By this proposal, the designs for any high-order PR filters and related high-resolution wideband channelizers can be guaranteed with excellent reconstruction performance. Some numerical simulations are provided to verify the effectiveness of the proposed method, even when the number of sub-channels reaches to 8192.

Terahertz frequency modulation continuous wave (THz FMCW) imaging technology has been widely used in non-destructive testing (NDT) applications of non-metallic materials. However, THz FMCW real-aperture radar usually has a narrow bandwidth and small depth of field, thus restricting the application of THz FMCW NDT. In this paper, a wideband THz signal (220-500 GHz) generation method is proposed by time-division multiplexing. Moreover, a dual-band quasi-optical design with a large depth of field is proposed based on the THz Bessel beam, and a high-quality range profile is obtained. Especially, a signal fusion extended Fourier analysis algorithm without prior knowledge is proposed to further enhance the range profile accuracy, which improves the range resolution to 0.28 mm (λ/3, center frequency 360 GHz). The effectiveness and advantages of the proposed system are verified by artificially constructing composite materials.

High resolution eigenstructure-based techniques for signal source localization are known to be ineffective when the source covariance matrix is not of full rank. We present here two techniques to circumvent this problem in the context of wideband active source localization. An extension is made to show how eigenstructure methods can be applied even when there is only one snapshot available to estimate the wideband spectral matrices.

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a heavily modified Boeing 747SP aircraft, accommodating a 2.5m infrared telescope. This airborne observation platform takes astronomers to flight altitudes of up to 13.7 km (45,000ft) and therefore allows an unobstructed view of the infrared universe at wavelengths between 0.3 m and 1600 m. SOFIA is currently completing its fourth cycle of observations and utilizes eight different imaging and spectroscopic science instruments. New instruments for SOFIAs cycle 4 observations are the High-resolution Airborne Wideband Camera-plus (HAWC+) and the Focal Plane Imager (FPI+). The latter is an integral part of the telescope assembly and is used on every SOFIA flight to ensure precise tracking on the desired targets. The FPI+ is used as a visual-light photometer in its role as facility science instrument. Since the upgrade of the FPI camera and electronics in 2013, it uses a thermo-electrically cooled science grade EM-CCD sensor inside a commercial-off-the-shelf Andor camera. The back-illuminated sensor has a peak quantum efficiency of 95% and the dark current is as low as 0.01 e-/pix/sec. With this new hardware the telescope has successfully tracked on 16th magnitude stars and thus the sky coverage, e.g. the area of sky that has suitable tracking stars, has increased to 99%. Before its use as an integrated tracking imager, the same type of camera has been used as a standalone diagnostic tool to analyze the telescope pointing stability at frequencies up to 200 Hz (imaging with 400 fps). These measurements help to improve the telescope pointing control algorithms and therefore reduce the image jitter in the focal plane. Science instruments benefit from this improvement with smaller image sizes for longer exposure times. The FPI has also been used to support astronomical observations like stellar occultations by the dwarf planet Pluto and a number of exoplanet transits. Especially the observation of the occultation events benefits from the high camera sensitivity, fast readout capability and the low read noise and it was possible to achieve high time resolution on the photometric light curves. This paper will give an overview of the development from the standalone diagnostic camera to the upgraded guiding/tracking camera, fully integrated into the telescope, while still offering the diagnostic capabilities and finally to the use as a facility science instrument on SOFIA.

The Stratospheric Observatory For Infrared Astronomy (SOFIA) is a 2.5 m telescope which will fly in a Boeing 747SP, commencing operation in late summer 2004. SOFIA is a joint American/German project and for most of this decade it will be the largest far-infrared telescope. SOFIA will have a suite of instruments available to the astronomical community, including the High-resolution Airborne Wide-band Camera (HAWC) - its facility far-infrared camera.

Application of the Analog Chirp Fourier Transform (ACFT) in generating low-latency, continuous, real-time frequency spectra of wide bandwidth radio frequeny (RF) signals is presented as an alternative to the digital FFT processor. Insights into the mathematical construct of ACFT, system modeling, and practical design considerations are presented. Resolution and worst-case frequency error are key metrics evaluated over design parameter choices and process, voltage, and temperature (PVT)-induced parameter variations. Experiments show accurate frequency spectrum representation over several decades extending from 200 MHz to 6 GHz with a 58 MHz worst-case resolution and 1 µs latency.

We report the demonstration of a high-resolution dual-channel wideband microwave photonic (MWP) switch exploiting Fano resonance based on stimulated Brillouin scattering in single-mode fiber. We demonstrate MWP switch from 1-11GHz with achieved extinction >30dB.

Transient radiated fields caused by impulsively excited apertures and aperture response caused by incident impulsive waves has been the subject of considerable research in acoustics. This research is also of importance to wideband radar. Medical ultrasound steered phased arrays use transmitted pulses consisting of from one to three cycles of a damped sinusoid, which is similar to certain ultra-wideband radar systems. Related studies applied to wide-band radar transmitting a single cycle of a sine wave indicate that it may be possible to construct a steered phased array radar with ultra high resolution using very sparse array apertures. In narrowband phased arrays, grating lobe considerations require that the array elements be placed close together. In contrast, very sparse, utra high resolution wide band arrays may be constructed without incurring grating lobe problems.

Because parametric array can generate wide band and narrow beam low frequency signals, it is widely used in high resolution subbottom profiling. Parametric sonar has been one of the most effective equipment in seabed configuration detection and property identification. Emphases of this paper are on source signal correction of wide band parametric subbottom profiler, so we can get desired difference frequency detective signals after non-linear self-demodulation of the wide-band parametric arrays. In order to generate desired Chirp subbottom profiling signal, we have to divide the Chirp waveform which is the envelope of wide-band parametric array's primary wave by its instantaneous frequency. The correction method which is called fragment correction is analyzed subsequently, it is used to correct 1/8 Sine-Square weighted Chirp envelope signal which is a high resolution source signal of subbottom profiler. The expressions of Chirp difference signals after self-demodulation of the wide-band parametric array are derived, and the simplified forms are also proposed at the same time. We can see that the Chirp difference frequency signals with its frequency and bandwidth twice of the primary frequency wave's envelope will be generated by self-demodulation process of wide-band parametric array no matter it was weighted or not. The comparison between expressions before and after simplification indicated that simplify process and the correction methods are all reasonable, computer simulations are given simultaneously. Researches on source signal correction of wide-band parametric array are important in designing source signals of high resolution wide-band parametric subbottom profiling and some other relevant engineering applications.

High-resolution methods for passive array processing have proved to be very efficient in increasing resolving power. The theory developed up to now is essentially narrowband, but it has been proved, using the Cramer-Rao bound, that it is possible to increase the resolving power by using a broad frequency bandwidth. A method that allows the solution to be computed analytically for a linear array with equally spaced sensors is presented. Results that show the improvement are reported. >

The compensation method of high resolution range profile of radar targets was talked over in this paper. Based on the need of the wide band high resolution signal processing, this paper discussed the one dimensional high resolution range profile (HRRP) obtained by the linear frequency modulated (LFM) wave. Because of the effect of velocity of the target, the one dimensional range profile will be displaced and defocused. We suggested some new methods to alleviate the effect of velocity, and simulated with the point scattering source model and the measured data of target model.

The wide band high resolution radiometer on the NIMBUS 7 satellite provides a detailed view of the net outgoing long wave radiation around the 11.5μm band. The availability of this data during 1979 made it possible to explore a statistical relationship among the radiance data and the divergent circulations based on the 200mb wind from the analysis of the Global Experiment data sets. This study reveals a very strong relationship between these fields at a horizontal resolution of wave number 8 (two dimensional). Examples of the monthly averaged and daily maps of the divergent wind, observational and statistically derived at this resolution, are compared. The use of this relationship, especially over the data sparse tropical latitudes, for numerical weather prediction and climate studies is suggested.