Abstract
The C band microwave signals are widely used for Earth observation in the field of remote sensing by using synthetic aperture radar sensor. The coverage of Indian regions by Sentinel 1A SAR ...sensor in interoferometric wide swath mode, provide an opportunity to research and conduct studies in remote sensing areas from urban planning to disaster management applications. The sensor acquired images undergo calibration test to confirm the quality requirements. The foremost significant step to ensure the availability of the signal of Sentinel 1A on the ground surface is by designing a antenna system which tracks and monitor the signal strength. In this context, the following stages are significant in signal monitoring system: satellite downlink budget calculation to ensure minimum signal strength, designing and configuring antenna system to receive the signals and measurement system such as spectrum analyser to monitor the signal strength. The paper presents the mathematical analysis of designing a down link for receiving Sentinel-1A SAR signals. An antenna subsystem is implemented which includes the design of the parabola antenna with horn feed and the simulation of the same using Matlab platform to confirm antenna parameters such as gain, directivity, VSWR and beam-width which meets the practical requirements
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•3D-printed tilt sensors are easy to manufacture, light, compact and cost effective.•Biaxial measurements provide larger operating range of the tilt sensor.•Fiber Bragg gratings ...approach were used due to its immunity against electromagnetic interference and short circuits.•A fiber Bragg grating is added as a temperature sensor to compensate the shift due to the change in temperature.
In this work, a novel 3D-printed biaxial sensor system for tilt measurement, based primarily on the use of four Fiber Bragg Grating (FBG) devices, has been developed and its performance characterized. The tilt sensor system created is of a compact design and relatively small dimensions, making it ideally suited to a variety of industrial applications. In the system developed, the four FBGs used were spliced in a serial formation and attached to four different sides of the sensor structure designed, to allow biaxial measurements to be made. The wavelengths' shift of the FBGs used were monitored as a function of the tilt of the device, using an Optical Spectrum Analyzer (OSA) for this development work. In the sensor, an average FBG-based responsivity of 0.01 nm/° of tilt was measured for each of the different FBGs used. To provide compensation for temperature changes in the system itself, a further FBG-based approach was used (in which they were configured to be insensitive to the effect of the tilt). They were thus calibrated by being exposed to a range of operational temperatures for the system, showing, as a result, a calibration of 0.011 nm/°C. Prior work on the sensor system had proved it to be highly linear in response, over the tilt range of 0° ± 90°. The experimental results obtained from the performance characterization indicate that the small, compact design of this type yields excellent responsivity, compared to other larger and more complex designs discussed in the literature. The sensor system was also relatively easy to fabricate using the 3D-printing method, creating in that way an inexpensive, temperature-compensated tilt monitoring device that had a wide variety of potential industrial applications.
The technological progress in the means of transmission of information is very fast and it became necessary to obtain high speed in data transmission and high rate of data. Therefore, optical ...communication systems are the leading methods in this field because they cover these needs, but despite all these characteristics, there is a problem, And we will get rid of this problem in practice in this research through the use of two separate and different wavelengths and connect them to the Wavelength Division Multiplexing and send them to a distance of 3 Km and calculate the amount of dispersion in the signal to the outside of the Optical spectrum analyzer with and without Optical Fiber Bragg Gratings.
A design rule for a Mach-Zehnder interferometer (MZI) sensor is presented, allowing tunable sensitivity by appropriately choosing the MZI arm lengths according to the formula given in this paper. The ...present MZI sensor designed by this method can achieve an ultra-high sensitivity, which is much higher than any other traditional MZI sensors. An example is given with silicon-on-insulator (SOI) nanowires and the device sensitivity is as high as 10
nm/refractive-index -unit (or even higher), by choosing the MZI arms appropriately. This makes it possible for one to realize a low-cost optical sensing system with a detection limit as high as 10
refractive-index-unit, even when a cheap optical spectrum analyzer with low-resolution (e.g., 1 nm) is used for the wavelength-shift measurement.
In this communication, an echo suppression method is presented to recover the true antenna gain pattern measured in a nonanechoic environment based on phaseless measurement data. With the proposed ...technique, the antenna pattern convoluted with the multipath spatial profile can be extracted with a deconvolution operation based on the scalar frequency response measurement, which can be easily obtained with a spectrum analyzer. The proposed scheme is advantageous compared to complex-signal-based methods since it is a phaseless solution. Moreover, a generalized solution jointly exploiting the frequency (i.e., using wideband scalar frequency response measurement) and spatial (i.e., using several spatial samples) domain is proposed to further improve the pattern reconstruction accuracy, where the state-of-the-art spatial-domain and the proposed frequency-domain solutions can be seen as special cases. Numerical simulations as well as experimental measurement results demonstrated the feasibility and advantages of the proposed algorithm.
The performance of high baud-rate fiber optical transmission with the use of advanced modulation formats is sensitive to the imperfection arising in transmitter optical sub-assembly (TOSA), and thus ...the effective calibration of the TOSA full-field response is essential. However, traditional TOSA frequency response characterization solutions are either inconvenient for the on-field measurement or unable to obtain the phase frequency response (PFR). Here, we report a simple and precise scheme to characterize the full-field frequency response of broadband TOSA, including both amplitude frequency response (AFR) and PFR, when only a single photodetector (PD) with narrow bandwidth is employed. A multiple dual-tone signals with specially designed frequency positions are implemented for electrical-to-optical modulation. Then, a few beat signals after direct detection occur at unique frequencies without the spectral overlapping. Thus, it is feasible to extract the full-field frequency response of broadband TOSA, under the single-shot measurement. Moreover, the in-phase and quadrature (IQ) skew can be obtained by comparing PFRs between I and Q tributaries. In the experiment, we successfully characterize a coherent TOSA with a 10 dB bandwidth of 40 GHz, when a single PD with a 3 dB bandwidth of 2 GHz is used. In comparison with the optical spectrum analyzer (OSA) based scheme, the measured AFR deviation is less than 1 dB over the 10 dB bandwidth. When multiple single-shot measurements are implemented within 1 minute, the fluctuation of measured PFR and IQ skew are less than 0.2 rad and 1 ps, respectively. With the help of the measured full-field frequency response, the coherent TOSA can be calibrated to realize 64 GBaud 16-quadrature amplitude modulation (QAM) back-to-back transmission, when the threshold of 7% hard-decision forward error correction (HD-FEC) is set.
Survey of CH3NH2 and its Formation Process Suzuki, Taiki; Majumdar, Liton; Goldsmith, Paul F. ...
The Astrophysical journal,
09/2023, Letnik:
954, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the observational results of a precursor of glycine, methylamine (CH3NH2), together with methanol (CH3OH) and methanimine (CH2NH) for the high-mass star-forming regions NGC 6334I, ...G10.47+0.03, G31.41+0.3, and W51 e1/e2 using the Atacama Large Millimeter/submillimeter Array. The molecular abundances of these sources were derived using the CASSIS spectrum analyzer and compared with our state-of-the-art three-phase chemical model NAUTILUS. We found that the observed abundance ratio of CH3NH2/CH3OH is between 0.008 and 1.0 for all sources, except for NGC 6334I MM3, where a ratio less than 0.002 is found. This may be due to its later evolutionary stage relative to the other cores. We also found that the observed CH3NH2/CH3OH ratio agrees well with the three-phase chemical model NAUTILUS, which includes the formation of CH3NH2 on the grain surface via a series of hydrogenation processes of HCN. This result clearly shows the importance of hydrogenation processes to form CH3NH2.
Optical transmission links are generally composed of optical fibers, optical amplifiers, and optical filters. In this paper, we present a channel reconstruction method (CRM) that extracts physical ...characteristics of multiple link components such as longitudinal fiber losses, chromatic dispersion (CD), multiple amplifiers' gain spectra, and multiple filters' responses, only from receiver-side (Rx) digital signal processing (DSP) of data-carrying signals. The concept is to reconstruct a virtual copy of an actual transmission channel in the digital domain, where optical fibers and amplifiers are modeled as the split-step Fourier method for the Manakov equation while optical filters are emulated as complex-valued finite impulse response filters. We estimate the model parameters such as losses, CD, gains, and filter responses from boundary conditions, i.e., transmitted and received signals. Experimental results show that, unlike traditional analog testing devices such as optical time-domain reflectometers and optical spectrum analyzers, CRM visualizes multi-span characteristics of fibers, amplifiers, and filters in Rx DSP, and thus localizes anomaly components among multiple ones without direct measurement.
We report the experimental generation of a broadband and flat mid-infrared supercontinuum in a silicon-germanium-on-silicon two-stage waveguide. Our particular design combines a short and narrow ...waveguide section for efficient supercontinuum generation, and an inverse tapered section that promotes the generation of two spectrally shifted dispersive waves along the propagation direction, leading to an overall broader and flatter supercontinuum. The experimentally generated supercontinuum extended from 2.4 to 5.5 µm, only limited by the long wavelength detection limit of our spectrum analyzer. Numerical simulations predict that the supercontinuum actually extends to 7.8 µm. We exploit the enhanced flatness of our supercontinuum for a proof-of-principle demonstration of free-space multi-species gas spectroscopy of water vapor and carbon dioxide.
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