Broadband Electronics Research Articles

Development of a toroidally resolved broadband ECE imaging system for measurement of turbulent fluctuations on the KSTAR.

The two electron cyclotron emission imaging (ECEI) systems installed at adjacent ports (G and H) on the KSTAR tokamak incorporate large-aperture mm-wave optics, broadband electronics, and high speed digitization (up to 1 MSa/s) for 2D and quasi-3D visualization of MHD-scale fluid dynamics. Recently, the ECEI systems have been proved to be capable of visualization of smaller scale fluctuations albeit with a limited spatiotemporal resolution and even capable of measurement of ion cyclotron harmonic waves by direct high-speed sampling of the ECE IF signals. A four-channel prototype subsystem with a higher sampling rate up to 16 GS/s has been integrated into the G-port ECEI system, enabling the measurement of plasma waves in the GHz range in the form of modulated ECE signals and characterization of high-frequency turbulence during the evolution of pedestal. To achieve higher toroidal resolution in the turbulence measurement, the H-port ECEI system is now being upgraded to have a toroidally dual detector array of 2(toroidal) × 12(vertical) × 8(radial) channel configuration and a high-speed subsystem of 2(toroidal) × 4 channel configuration. The new mm-wave optics has been designed via beam propagation simulation, and the measured performance of the fabricated lens indicates a toroidal resolution of 8-10cm depending on the focus position and zoom factor, allowing for the measurement of parallel wavenumber up to k‖ ∼ 0.8cm-1.

Real-time, chirped-pulse heterodyne detection at room temperature with 100 GHz 3-dB-bandwidth mid-infrared quantum-well photodetectors

Thanks to intrinsically short electronic relaxation on the ps time scale, III-V semiconductor unipolar devices are ideal candidates for ultrahigh-speed operation at mid-infrared frequencies. In this work, antenna-coupled, GaAs-based multi-quantum-well photodetectors operating in the 10–11 µm range are demonstrated, with a responsivity of 0.3 A/W and a 3-dB-cutoff bandwidth of 100 GHz at room temperature. The frequency response is measured up to 220 GHz: beyond 100 GHz we find a roll-off dominated by the 2.5-ps-long recombination time of the photo-excited electrons. The potential of the detectors is illustrated by setting up an experiment where the time dependent emission frequency of a quantum cascade laser operated in pulsed mode is measured electronically and in real time, over a frequency range >60GHz. By exploiting broadband electronics, and thanks to its high signal-to-noise ratio, this technique allows the acquisition, in a single-shot, of frequency-calibrated, mid-infrared molecular spectra spanning up to 100 GHz and beyond, which is particularly attractive for fast, active remote sensing applications in fields such as environmental or combustion monitoring.

Crystalline Orientation‐Tunable Growth of Hexagonal and Tetragonal 2H─PtSe2 Single‐Crystal Flakes

AbstractDue to the narrow bandgap, environment stability, and Pt vacancy‐induced magnetism, PtSe2 has been considered a promising candidate for future broadband photodetection and electronics. However, the growth of single‐crystal PtSe2 is still a challenge. Herein, the synthesis of hexagonal and tetragonal 2H─PtSe2 single‐crystal flakes by precisely tailoring the growth temperature is reported. Through atomic structure analysis, hexagonal and tetragonal flakes are proven c‐axis and a‐axis orientations of 2H─PtSe2, indicating the preferred nucleation orientations are along the basal plane and vertically basal plane, respectively. The crystalline orientation‐dependent properties are studied including high‐pressure and polarized in situ‐Raman, electrical transport. The out‐of‐basal plane vibration (A1g) is sensitive to pressure showing 2.744 and 3.282 cm−1 GPa−1 corresponding to c‐2H─PtSe2 and a‐2H─PtSe2, respectively. The conductivity of c‐2H─PtSe2 is 57 times higher than that of a‐2H─PtSe2. Furthermore, by studying magnetic transport at low temperatures, both c‐2H─PtSe2 and a‐2H─PtSe2 exhibit butterfly‐shaped magnetoresistance hysteresis suggesting their ferromagnetic property. The c‐2H─PtSe2 has a higher |MR| ratio and higher coercive field compared with a‐2H─PtSe2, indicating that across multilayer carrier regulation for c‐2H─PtSe2 is more difficult than intra‐layer carrier regulation for a‐2H─PtSe2. This study opens the way to grow different crystalline orientations of 2D materials and will bring more abundant properties.

MAPbI3-based efficient, transparent and air-stable broadband photodetectors

Numerous structures have been reported in search of affordable self-powered broadband photodetectors, however with limited success. The hybrid perovskite heterostructures have been attracted great attention due to their advance optical and electrical properties. The stability and facile synthesis are critical issues in achieving the potential success of realizing perovskite-based photodetectors. Herein, we report a facile one-step spray-coated method to synthesize MAPbI3 perovskite polycrystalline thin-film on the glass as photodetector followed by their morphological (Atomic force microscopy), structural (X-ray diffraction/Fourier transform infrared spectroscopy, optical (UV–Vis), and electrical characterization. The device shows a very good response for visible and NIR region with the responsivity, detectivity, and external quantum efficiency of 1.682 mA/W, 1.5065 × 1012 Jones, and 0.3799, respectively. Further, the device exhibits photoresponse under visible to IR (400–900 nm) light illuminations, which holds great futuristic promises for affordable, broadband, stable, and efficient energy-conserving electronics.

Video-rate centimeter-range optical coherence tomography based on dual optical frequency combs by electro-optic modulators.

Imaging speed and range are two important parameters for optical coherence tomography (OCT). A conventional video-rate centimeter-range OCT requires an optical source with hundreds of kHz repetition rate and needs the support of broadband detectors and electronics (>1 GHz). In this paper, a type of video-rate centimeter-range OCT system is proposed and demonstrated based on dual optical frequency combs by leveraging electro-optic modulators. The repetition rate difference between dual combs, i.e. the A-scan rate of dual-comb OCT, can be adjusted within 0~6 MHz. By down-converting the interference signal from optical domain to radio-frequency domain through dual comb beating, the down-converted bandwidth of the interference signal is less than 22.5 MHz which is at least two orders of magnitude lower than that in conventional OCT systems. A LabVIEW program is developed for video-rate operation, and the centimeter imaging depth is proved by using 10 pieces of 1-mm thick glass stacked as the sample. The effective beating bandwidth between two optical comb sources is 7 nm corresponding to ~108 comb lines, and the axial resolution of the dual-comb OCT is 158 µm. Dual optical frequency combs provide a promising solution to relax the detection bandwidth requirement in fast long-range OCT systems.

Flexible RF Filtering Front-End For Simultaneous Multinuclear MR Spectroscopy.

Simultaneously interrogation of multiple nuclei has been of interest since the very earliest days of MRI [1]-[3]. Our group and several others are revisiting this topic [4]-[6]. Very fast broadband electronics make it possible to digitize a wide spectrum, including multiple nuclei, but this places great demands on data throughput. Another issue is that there can be great variance between RF preamplifier gain required for the different nuclei. To overcome the data problem, it is desirable to use undersampling, but this requires passband filtering around the resonant frequency of each nuclei. Here we present a frequency agile front end that provides separate data paths for each nucleus, either from a single coil or from multiple ports, allows independent gain, filters each using very flexible transmission line filtering, and then combines them back for undersampling.

Broadband power electronics controlled voltage source with output stage based on GaN transistors

Broadband power electronics controlled voltage source with output stage based on GaN transistors

Broadband power electronics controlled current source with analouge control section and output stage based

Broadband power electronics controlled current source with analouge control section and output stage based

Broadband power electronics controlled current source with analogue control section and output stage based on GaN transistors

Broadband power electronics controlled current source with analogue control section and output stage based on GaN transistors

Modular Printed Circuit Boards for Broadband Characterization of Nanoelectronic Quantum Devices

We report on the development of a modular system of high-frequency printed circuit boards (PCBs) for electrical low-noise characterization of multigate quantum devices. The whole measurement setup comprises PCBs operating from room temperature to a few kelvins, and custom software to control the broadband electronics held at cryogenic and room temperature. The PCBs coupling scheme and the custom tailoring of the user panel make our platform particularly flexible. At the cryogenic stage, one board hosts the electronics for readout. It consists in a custom complementary metal–oxide–semiconductor circuit for the current sensing. It is composed by a multiplexer for a digital selection of the device under test among up to four samples, connected to a cryogenic transimpedance amplifier with two possible gains, the maximum bandwidth of 250 kHz and the minimum equivalent input noise of 10 fA/ $\sqrt {\mathrm{Hz}}$ . Such board is coupled to the PCB sample holder, where 14 low-frequency input lines bias the devices and control the gates. Four additional high-frequency input paths with a bandwidth of 1 GHz and an isolation lower than −40 dB at 3 GHz have been implemented to apply a few millivolt pulses with a minimum duration of 1 ns. The PCBs assemblage and the cryogenic electronics are electrically characterized at 4.2 K and later used to perform quantum transport spectroscopy and single-charge dynamics readout at a few microsecond scales in two silicon nanoscaled field-effect transistors.

VHF Lightning Observations on JEM-GLIMS Mission -Gradual Approach to Realize Space-borne VHF Broadband Digital Interferometer-

Global Lightning and sprIte MeaSurements (GLIMS) mission is scheduled on Exposed Facility of Japanese Experiment Module (JEM-EF) of the International Space Station (ISS). This paper introduced an electromagnetic (EM) payload of JEM-GLIMS mission, very high frequency (VHF) broadband digital InTerFerometer (VITF). VITF consists of a pair of VHF broadband antennas and electronics to record EM waveforms from lightning discharges. It is designed to estimate the direction-of-arrival with about 10 km resolution that is equivalent to the scale of a thundercloud. It means that VITF is able to monitor thunderclouds with lightning activities globally. Comprehensive observations with the optical payloads of JEM-GLIMS mission for lightning activities and related transient luminous events (TLEs) are expected to give us many scientific impacts to the field. The developments of VITF are based on the heritage of VHF sensor on Maido-1 satellite.

Charge transport properties of single crystal CVD-diamond particle detectors

The charge transport properties of virgin and heavily irradiated intrinsic Single-Crystal CVD-Diamond Detectors (SC-CVD-DD) are discussed by means of the Transient-Current Technique (TCT), which proved to be a sensitive tool to detect the first changes of the detector's performance. Charge-carrier mobilities μ e = 1300–3100 cm 2/V s, μ h = 2400 cm 2/V s and effective deep-trapping lifetimes τ eff-h = 300–900 ns, τ eff-e = 160–360 ns were measured in the non-irradiated state, decreasing slightly after irradiation by a fluency F > 10 13 p 26MeV cm − 2 . The carriers drift velocity remained almost unchanged after irradiation, indicating the creation of mainly neutral defects. After exposure to fluency above 10 16 p cm − 2 however, TC signals were not detectable with the available broadband electronics. A significant improvement was observed after annealing at 1000 °C, and almost complete restoration was obtained by priming with 90Sr-electrons. Optical absorption (OA) spectra confirmed the degradation of the detector performance after exposure to increasing particle fluencies, showing deviations from the intrinsic ‘edge absorption’ shape around 5.3 eV that was observed before irradiation.

Characterisation of single crystal CVD diamond particle detectors for hadron physics experiments

AbstractCharacterisation results from a single‐crystal CVD diamond detector are reported, which is under development for heavy‐ion particle identification and minimum‐ionizing particles timing in nuclear physics experiments. The charge collection efficiency is about 100%, never obtained from polycrystalline CVD‐diamond detectors. An energy resolution of 20 keV (ΔE/E ≈ 0.004) is achieved using a mixed nuclide α‐source, which is comparable to the energy resolution of silicon pin diode detectors. Using low impedance broadband electronics and a ToF technique, where holes or electrons drift separately inside the diamond bulk, the saturation velocity, mobility and lifetime of both charge carriers are estimated. In addition the thermoluminescent properties of the new material are discussed in comparison to polycrystalline diamond. A much lower density of trapping centres has been found for single‐crystal CVD diamond. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The use of CVD-diamond for heavy-ion detection

The suitability of CVD-diamond detectors is investigated for applications in heavy-ion accelerator facilities with high intensity beams. Various diamond films of ‘optical’ and ‘electronic grade’ used and unpolished (as grown) are tested with different ions from α-particles ( 241Am-source) up to the heaviest ions like 208Pb and 238U. The diamond signals are processed in a single-particle mode with current sensitive low-noise broadband electronics. An intrinsic time resolution of σ i (Δ T)=29 ps is achieved using detectors of ‘optical grade’ with a thickness of 100 μm. The time resolution improves for thicker samples and for higher electric field applied to the detector. Determined by the strip capacitance and the electronics used, a single-particle counting rate capability >10 8 ions/s is obtained. The charge collected from different particles increases linearly with the energy loss of the particle and non-linearly with the detector thickness. The pulse-height resolution depends strongly on the material texture and on the irradiation state of the sample and weakly on the ionisation density produced by the particle. ‘Priming’ is observed up to a fluence of 10 10 ions/cm 2. The homogeneity over the detector area increases significantly. The charge-collection efficiency improves by a factor of 2 and the pulse-height resolution significantly by a factor of 5. The bandwidth of available electronics limits the results obtained at present. Nevertheless, the selection of data presented demonstrates an excellent suitability of CVD diamond for a variety of heavy-ion applications.

Broadband electronics for CVD-diamond detectors

The application of CVD-diamond detectors for particle detection has created a demand for the development of very fast, low-noise electronics operated at high dc bias voltages. To take advantage of the high charge-carrier mobility of the new detector material the signal processing is performed using microwave layout techniques as well as picosecond pulse shapers and GHz-frequency dividers. The particle detection limits of CVD-diamond detectors processed with low impedance broadband electronics are described. The properties of the developed electronics are discussed in conjunction with results from beam diagnostics operation in the broad energy range of 120 keV/amu up to 2 GeV/amu for GSIs heavy ion accelerators.

Design and performance of a self-contained fan-beam ADCP

Recent field studies have shown the utility of acoustic Doppler current profilers (ADCPs) with fan-shaped transducer beam patterns (narrow in azimuth and broad in elevation) for the measurement of oceanic surface currents. For wind speeds greater than about 3 m/spl middot/s/sup -1/, the acoustic backscatter is dominated by microbubbles in the upper few meters of the water column, and beams intersecting the surface from below effectively map out horizontal profiles of near-surface current. This paper describes the design and performance of a self-contained, fan-beam ADCP consisting of RD Instruments 300 kHz BroadBand electronics mated to a specially designed transducer head, and intended for long-term deployment on conventional oceanographic moorings. The instrument operated successfully during two field deployments, providing horizontal profiles of near-surface velocity with precision of about 1 cm/spl middot/s/sup -1/ and horizontal resolution of about 5 m. Profiles were obtained once per minute during 20 min "burst" samples each hour. The usable horizontal range varied with wind speed from about 100 to 200 m. Distinct convergence patterns indicative of Langmuir circulation were evident in the cross-wind velocity field during strong forcing events. Time-range maps and horizontal wavenumber spectra of velocity showed evolution of the strength and dominant scale of the circulation during these events.

23.8 Gb/in.2 areal density demonstration

We have demonstrated 23.8 Gb/in.2 areal density using a merged read-write grant magnetoresistive head, with an oriented thin film medium tested with broadband electronics and enhanced EPR4 channels. The medium had high signal to noise ratio metrics that was robust unto temperatures as high as 75 °C. A unique aspect of the head design at such a narrow track width is the simultaneous enhancement of the transducer sensitivity while keeping product and system manufacturability in the forefront. The areal density was demonstrated at a track density of 45.8 k tracks/in., using photolithographically defined poles and linear density of 520 k bits/in.

An air-supported polarizer rotator with precise phase control for LF modulation of optical and infrared radiation

A high precision rotator with accurate mechanical phase control has been constructed. The system is primarily designed for the rotation of polarizers, diameters up to 100 mm, to produce amplitude modulation of broad band radiation in acousto-optical instruments for radiation intensity measurement. Rotation speed may be phase-locked at 2, 4 or 8 Hz to a crystal oscillator or over the range 0.625-10.5 Hz to an external signal. Air bearings are used for low friction and noise: acoustic output, at 80 mm, is only 16 mu Pa at 4 and 8 Hz. A high torque motor gives fast rotor acceleration, 57 rad s-2, and broad-band phase control electronics (analogue and digital) utilizing encoding marks on the rotor circumference give good stability over the range of speeds without external adjustment. Outputs at 128 and 4 pulses rev-1 are provided for synchronization of external apparatus such as phase sensitive detectors. The standard deviation, at 4 Hz (240 RPM), in phase determined between pi /2 pulses (4 per rev) is 1 mrad and in frequency, measured over 100 s, is 0.8 mu Hz (2*10-7).

Radar cross section measurements

The progress in radar cross section measurements is strongly related to the progress in radar technology. The recent acceleration in radar technology and processing techniques has generated a corresponding acceleration in interest for radar cross section measurements. Historically, early radar cross section measurements were performed to determine the detection range of radar systems, a fundamental objective that still exists. Later measurements, coupled with analytic techniques and computer codes, were performed to extend our understanding of the radar scattering process. At the present time, the availability of broad-band electronics, signal processing techniques, and digital technology results in radar cross section measurement programs which are directed toward exploring the performance of operational waveforms and processing, target discrimination, target detectability in clutter, and radar scattering control. The fundamentals of radar cross section measurements are reviewed. Measurement facilities, including the present research activities on compact range techniques, are then described. Instrumentation radars have benefited from both wide-bandwidth electronics and digital processing capabilities; Fourier transform techniques, in particular, provide both additional information on target scattering, and increase measurement accuracy by isolating the target from radar returns from the measurement facility. The frequency coverage has also extended to include millimeter-wave frequencies. Achievable accuracy is important in any measurement program, and those factors that limit the accuracy of radar cross section measurements are discussed.