- 标题
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- 实验方案
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Point-Spread-Function (PSF) Characterization of a 340 GHz Imaging Radar using Acoustic Levitation
摘要： In this paper, resolution characterization and beam analysis of a 340 GHz imaging radar are demonstrated by means of a point-spread-function imaging an acoustically levitated point-like target. It is shown that at THz frequencies, conventional PSF measurement techniques are limited by the presence of strong scattering response of background objects, such as suspension threads, within the imaging field-of-view (FOV). Using acoustic levitation, it is possible to eliminate secondary objects within the FOV and achieve a pure PSF characterization of the radar. It is shown that the PSF patterns obtained using acoustic levitation exhibit high fidelity and are free from artifacts. We demonstrate this using a small water droplet suspended in air at the focus of the 340 GHz radar. The measured PSF characteristics of the radar are in excellent agreement with physical optics (PO) simulations and analytical results.
关键词： acoustic levitation,submillimeter,antenna,beam,point-spread-function (PSF),Radar,imaging,acoustics
更新于2025-09-11 14:15:04
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High spectral and spatial resolution observations of the PDR emission in the NGC 2023 reflection nebula with SOFIA and APEX
摘要： We have mapped the NGC 2023 reflection nebula in [C ii] and CO(11?10) with the heterodyne receiver GREAT on SOFIA and obtained slightly smaller maps in 13CO(3?2), CO(3?2), CO(4?3), CO(6?5), and CO(7?6) with APEX in Chile. We use these data to probe the morphology, kinematics, and physical conditions of the C ii region, which is ionized by FUV radiation from the B2 star HD 37903. The [C ii] emission traces an ellipsoidal shell-like region at a position angle of ～?50?, and is surrounded by a hot molecular shell. In the southeast, where the C ii region expands into a dense, clumpy molecular cloud ridge, we see narrow and strong line emission from high-J CO lines, which comes from a thin, hot molecular shell surrounding the [C ii] emission. The [C ii] lines are broader and show photo evaporating gas flowing into the C ii region. Based on the strength of the [13C ii] F = 2?1 line, the [C ii] line appears to be somewhat optically thick over most of the nebula with an optical depth of a few. We model the physical conditions of the surrounding molecular cloud and the PDR emission using both RADEX and simple PDR models. The temperature of the CO emitting PDR shell is ～90?120 K, with densities of 105?106 cm?3, as deduced from RADEX modeling. Our PDR modeling indicates that the PDR layer where [C ii] emission dominates has somewhat lower densities, 104 to a few times 105 cm?3.
关键词： ISM: clouds,ISM: lines and bands,ISM: molecules,ISM: individual objects: NGC 2023,photon-dominated region (PDR),submillimeter: ISM
更新于2025-09-10 09:29:36
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Integrated Beam Scanning Silicon Lens Antenna at Submillimeter Wavelengths
摘要： This paper presents a lens antenna that scans the beam using an integrated piezo-motor at submillimeter wave frequencies. The lens antenna is based on the concept presented in [1], a leaky wave waveguide feed in order to achieve wide angle scanning and seamless integration with the receiver. The lens is translated from the origin of the waveguide producing the scanning of the beam over a 50 deg Field of View (FoV) (or about 6.25 beamwidths) with a maximum scanning loss of 1 dB. The lens movement is achieved with a piezoelectric motor that is integrated within the antenna and receiver block. A prototype was built and measured at 550 GHz achieving scanning beam angles close to 20 degrees with only 0.6 dB of loss. The scanning of the 50 deg FoV, which corresponds to a lens displacement of approximately 2 mm, takes about 0.9 s achieving a scanning rate of 0.75 Hz of the FoV. The accuracy in continuous mode of the piezo actuator has been measured to be less than 28μm in the worse of cases for displacements of 2 mm, which corresponds to a beam steering of 0.76 deg, much smaller than the antenna half power beamdwith of 8 deg.
关键词： leaky-wave waveguide feed,piezo-motor,Beam-scanning,submillimeter-wave,silicon lens
更新于2025-09-09 09:28:46
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[IEEE 2018 15th Workshop on Positioning, Navigation and Communications (WPNC) - Bremen, Germany (2018.10.25-2018.10.26)] 2018 15th Workshop on Positioning, Navigation and Communications (WPNC) - 100 Gbps and beyond: Hardware in the Loop experiments with PSSS modulation using 230 GHz RF frontend
摘要： The terahertz frequency range provides abundant bandwidth (25GHz ~ 50 GHz) to achieve ultra-high-speed wireless communication and enables data rates up to and above 100 Gbps. Parallel Sequence Spread Spectrum (PSSS) is a physical layer (PHY) baseband technology which is suitable for ultra-high speed wireless communication since the receiver architecture is straightforward and can be implemented almost entirely in analog hardware. In this paper, a PSSS modulated signal at a chip rate of 20 Gcps with a spectral efficiency of 4 bit/s/Hz is transmitted using a 230 GHz RF-front-end operating in the linear range to achieve 80 Gbps. The PSSS transceiver models are implemented in MATLAB/Simulink. The PSSS transmitter generates the PSSS modulated symbols that are loaded into an Arbitrary Waveform generator (AWG) and are then transmitted using the available 230 GHz wireless frontend. A Real-Time Oscilloscope samples and stores the received signal. The PSSS receiver performs synchronization, channel estimation, and demodulation. For a coded data rate of 80 Gbps, a BER of 2.072?10-3 has been measured. Thus, PSSS modulation is the promising modulation technique to achieve a data rate up to or above 100 Gbps in the Terahertz domain
关键词： PSSS,100 Gbps,broadband receiver,THz,wireless,PHY layer,submillimeter-wave,Hardware-In-The-Loop
更新于2025-09-09 09:28:46
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Planet-induced disk structures: A comparison between (sub)mm and infrared radiation
摘要： Context. Young giant planets, which are embedded in a circumstellar disk, will significantly perturb the disk density distribution. This effect can potentially be used as an indirect tracer for planets. Aims. We investigate the feasibility of observing planet-induced gaps in circumstellar disks in scattered light. Methods. We perform 3D hydrodynamical disk simulations combined with subsequent radiative transfer calculations in scattered light for different star, disk, and planet configurations. The results are compared to those of a corresponding study for the (sub)mm thermal re-emission. Results. The feasibility of detecting planet-induced gaps in scattered light is mainly influenced by the optical depth of the disk and therefore by the disk size and mass. Planet-induced gaps are in general only detectable if the photosphere of the disks is sufficiently disturbed. Within the limitations given by the parameter space here considered, we find that gap detection is possible in the case of disks with masses below ～10?4···?3 M(cid:4). Compared to the disk mass that marks the lower Atacama Large (Sub)Millimeter Array (ALMA) detection limit for the thermal radiation re-emitted by the disk, it is possible to detect the same gap both in re-emission and scattered light only in a narrow range of disk masses around ～10?4 M(cid:4), corresponding to 16% of cases considered in our study.
关键词： radiation mechanisms: general,planet-disk interactions,radiative transfer,planets and satellites: general,hydrodynamics,submillimeter: general
更新于2025-09-09 09:28:46
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Perspective Field Emitters For Electron-Beam Microwave Devices Of Short-Wave Millimeter And Submillimeter Range
摘要： In this report, distributed field emitters are considered, which are perspective for use in miniature but high-voltage electronic devices operating in a technical vacuum. The main attention is paid to the latest developments of the authors on the creation of a new type cathodes: multitip silicon cathodes with protective metal-fullerene coating and multilayer cathodes prepared from the brought into contact materials with different work function. The possibility of obtaining with the help of these cathodes field emission currents and current densities sufficient for maintenance of operation of microwave devices of millimeter and submillimeter range is demonstrated.
关键词： millimeter and submillimeter range,microwave devices,multilayer cathodes,metal-fullerene coating,field emitters,multitip silicon cathodes
更新于2025-09-09 09:28:46
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - A Compact Room-Temperature 510-560 GHz Frequency Tripler with 30-mW Output Power
摘要： We report on a compact high-power 510-560 GHz GaAs Schottky diode based frequency tripler with enhanced power handling capabilities, showing a world-record measured peak power of 30 mW, at room-temperature, when pumped with 350-400 mW. This corresponds to a ten times better performance than previously reported sources in this frequency range. The increase in power handling capabilities is achieved by using an improved epitaxial structure together with an on-chip power combined topology that allows to combine several multiplying structures onto a single chip. The chip also exhibits a state-of-the- art conversion efficiency of 8-9% without any correction for the losses in fixtures/transitions used for the tests.
关键词： Schottky diodes,frequency multipliers,submillimeter-wave technology,terahertz technology.,Submillimeter-wave sources
更新于2025-09-04 15:30:14
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Generation of Electromagnetic Rogue-Waves in Submillimeter-Band Gyrotrons
摘要： Rogue-waves in gyrotrons represent sporadically emitted ultrashort electromagnetic pulses with intensities significantly greater than the average radiation power and, in optimal conditions, higher than the power of the driving electron beams. In this paper within the framework of the average approach and direct 3D PIC (particle-in-cell) simulations, we study the possibility of rogue wave generation in submillimeter-band gyrotrons operating at high-order modes. It is demonstrated that in a 500 GHz fundamental cyclotron harmonic gyrotron excited by the 30 kV/50 A helical electron beam the peak power of generated picosecond electromagnetic spikes at TE61 mode can reach 5 MW that more than three times exceeds the power of the driving beam.
关键词： Rogue waves,Submillimeter-wave radiation,Gyrotron
更新于2025-09-04 15:30:14
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Uncertainties and biases of source masses derived from fits of integrated fluxes or image intensities
摘要： Fitting spectral distributions of total ?uxes or image intensities are two standard methods for estimating the masses of starless cores and protostellar envelopes. These mass estimates, which are the main source and basis of our knowledge of the origin and evolution of self-gravitating cores and protostars, are uncertain. It is important to clearly understand sources of statistical and systematic errors stemming from the methods and minimize the errors. In this model-based study, a grid of radiative transfer models of starless cores and protostellar envelopes was computed and their total ?uxes and image intensities were ?tted to derive the model masses. To investigate intrinsic e?ects related to the physical objects, all observational complications were explicitly ignored. Known true values of the numerical models allow assessment of the qualities of the methods and ?tting models, as well as the e?ects of nonuniform temperatures, far-infrared opacity slope, selected subsets of wavelengths, background subtraction, and angular resolutions. The method of ?tting intensities gives more accurate masses for more resolved objects than the method of ?tting ?uxes. With the latter, a ?tting model that assumes optically thin emission gives much better results than the one allowing substantial optical depths. Temperature excesses within the objects above the mass-averaged values skew their spectral shapes towards shorter wavelengths, leading to masses underestimated typically by factors 2?5. With a ?xed opacity slope deviating from the true value by a factor of 1.2, masses are inaccurate within a factor of 2. The most accurate masses are estimated by ?tting just two or three of the longest wavelength measurements. Conventional algorithm of background subtraction is a likely source of large systematic errors. The absolute values of masses of the unresolved or poorly resolved objects in star-forming regions are uncertain to within at least a factor of 2?3.
关键词： submillimeter: ISM,techniques: photometric,stars: formation,methods: data analysis,infrared: ISM,techniques: image processing
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Integrated Beam-Scanning Antenna for Heterodyne Instruments at Submillimeter-Wave Frequencies for Martian Climatology Measurements
摘要： The aim of this paper is to present an integrated beam-scanning antenna for a submillimeter wave instrument. The ultimate goal is to be able to scan the limb of the Martian surface to measure the wind, temperature and water vapor. The scanning of the limb can be achieved by the mechanical translation of a micro-lens using a piezo-electric motor integrated with the receiver. A prototype has been fabricated and measured at 550 GHz, achieving a scanning loss lower than 0.4 dB for beam angles up to 15 degrees.
关键词： beam-scanning,submillimeter-wave,micro-lens,silicon,antenna
更新于2025-09-04 15:30:14