Search

We investigate recirculating transmission of a wideband S-, C- and L-band signal in a 4-core fiber. We transmit 552 x 25 GHz spaced, 24.5 GBd channels. covering more than a 120 nm bandwidth from 1487.8 nm to 1608.33 nm through each core of the multi-core fiber (MCF) which has the same 125m cladding dimeter as standard single-mode fiber. We first use PDM-16QAM modulation and measure performance at distances up to 3001 km, corresponding to 43 spans of the 69.8 km MCF. At this distance we measure a decoded throughput of 319 Tb/s or 342 Tb/s when estimating from the generalised mutual information (GMI). Extending the transmission distance to 8027 km, a selection of PDM-QPSK modulated channels across the spectrum were received with an average GMI estimated data-rate of 82.8 Gb/s. These results show that wideband transmission including the S-band has the potential to increase data-rates in long-haul optical fiber transmission. Further, our experiment confirms that 125 m diameter MCFs can multiply transmission capacity whilst offering benefits of resource sharing and integration, expected in SDM systems.

Synthetic aperture radar tomography (TomoSAR) at different radar wavelength can be used to measure different structural elements of forests. In this letter, we compared the airborne P- and L-band synthetic aperture radar (SAR) tomograms and TomoSAR-measured canopy height model (CHM) and above-ground biomass (AGB) over a tropical forest in Lope, Gabon. The SAR data sets were acquired by German Aerospace Center (DLR)'s F-SAR system during the AfriSAR2016 campaign. First, the Weighted covariance fitting-based Iterative Spectral Estimator (WISE) was applied to obtain tomograms. CHM was then retrieved based on the canopy phase center derived from the tomograms. Finally, AGB was estimated via an empirical logarithmic model developed from field measurements and the tomographic backscatter power of vegetation layers between 40 and 50 m above ground. Compared with the classical approaches of Capon and Wavelet-based Compressed Sensing, the WISE method can achieve better resolution with higher computational efficiency and reduce the ambiguity level of L-band tomograms successfully. The experimental results also show that there is no substantial difference between P- and L-band TomoCHM, while P-band tomographic intensity is more sensitive than the L-band for the inversion of tropical forest AGB at a resolution of 50 m x 50 m.

Synthetic aperture radar tomography (TomoSAR) at lower frequencies allows the reconstruction of the 3-D radar reflectivity of volume scatterers allowing access to their physical 3-D structure by means of multiangular SAR acquisitions. The performance of the reconstruction critically depends on the number and (spatial) distribution of the tomographic acquisitions (tracks). This dependence is addressed in this letter with respect to forest applications (volume scatters) at L-band. The letter discusses the optimum definition of tomographic configurations based on the peak sidelobe level (PSL) of the point spread function (PSF). For demonstration, a tomographic data set consisting of 15 acquisitions acquired by the DLR's F-SAR system at L-band over the Traunstein test site in Germany is used, complemented by airborne LiDAR measurements. Three different reconstruction algorithms (Fourier beamforming, Capon beamforming, and compressive sensing) are implemented and compared to each other for scenarios with a reduced number of acquisitions. Although the limitation of the specific forest, the results show the potential of using the PSL of the PSF to define tomographic configurations optimized for forest structure applications.

This article presents a study on the power consumption and performance analysis of a small, portable, and ultra-low power total power L-band radiometer. The article explores two processing architectures: the ZYNQ 7010 and the ARM A8 embedded microprocessor. The processing algorithm based in C++ was tested for different clock frequencies, ADC sampling speeds, and sizes of the ADC buffer. To reduce the power consumption and the algorithm execution time, high-level and system-level optimizations, along with fixed-point Q(16,16) data representation, were applied to the main code running on LINUX Debian V8. In the case with the ZYNQ 7010, the optimizations had no notable impact on reducing power or execution time in comparison with the ARM A8, where significant variations were measured, showing a tradeoff between power consumption and algorithm performance that limits the processing capability and the system flight time. The ZYNQ 7010 runs the algorithm faster, but the power consumption is higher than the ARM A8. Using the fixed-point Q(16,16) implementation reduced the power consumption and the execution time in both architectures. Based on these results, we developed a heuristic methodology to minimize power consumption and increase the performance. Energy consumption savings for the radiometer during 20 min of flight was 48%. The size of the radiometer was reduced to 30 cm × 30 cm × 10 cm, with a weight of 1.36 kg, (3 lb) allowing the system be carried by small drones. The results were validated measuring salinity at two locations in Western Puerto Rico.

Cross-polarized temporal coherence observations of a boreal forest, acquired using a tower-based radar, are presented in this article. Temporal coherence is analyzed with respect to frequency, temporal baseline, time of day of observation, season, meteorological variables, and biophysical variables. During the summer, P- and L-band temporal coherence exhibited diurnal cycles, which appeared to be due to high rates of transpiration and convective winds during the day. During the winter, freeze-thaw cycles and precipitation resulted in decorrelation. At temporal baselines of seconds to hours, a high temporal coherence was observed even at C-band. The best observation times of the day were midnight and dawn. Temporal coherence is the main limitation of accuracy in interferometric and tomographic forest applications. The observations from this experiment will allow for better spaceborne SAR mission designs for forest applications, better temporal decorrelation modeling, and more accurate forest parameter estimation algorithms using interferometric and tomographic SAR data.

In this work, Er3+-doped phosphate glass with good flatness of the emission spectrum of the L+ band was prepared by optimizing the content of BaO. The absorption and emission spectra were measured. Increase of BaO content is conducive to the broadening of the emission spectrum in the L+ band. The dependence of flatness with Raman intensity has been shown by linear fitting. The results show that B31 sample has best flatness of the emission spectrum in the L+ band. It is showed that the largest emission cross-section at 1630 nm is 0.0529 × 10-20 cm2 and higher than other Er3+-doped phosphate glass. Decay curves of the 4I13/2 level were measured and the longest fluorescent lifetime is 10.18 ms and longer than other glass except germinate glass. The broadening of the Er3+-doped phosphate glass spectrum of the L+ band has been achieved successfully, which provides a reference for the material of optical amplifiers.

The potential of interferometric synthetic aperture radar (InSAR) for subsurface height estimation has long been recognized; however, this method is greatly limited by the data sources and the various errors encountered in a highly dynamic environment such as a desert. In this letter, a coherence scattering model based on the volume coherence and imaging geometry of the InSAR acquisitions is proposed to retrieve the penetration depth of the synthetic aperture radar (SAR) signal in a hyperarid desert area. The proposed method includes two main parts: 1) the dielectric constant of the study area is first derived by employing an empirical model with the L-band SAR data, and then, the results are used to calibrate the vertical effective wavenumber after the refraction process and 2) together with the extracted volume coherence from the SAR data, the scattering model is employed to retrieve the penetration depth. The application scope of the vertical effective wavenumber in the volume and temporal decorrelation effect of the model is also discussed in this letter. The method was tested with the Advanced Land Observing Satellite-1 (ALOS-1) Phased Array-type L-Band Synthetic Aperture Radar (PALSAR) data from a desert area in southeast Libya. The results show that the average penetration depth of the L-band SAR in the study area is 2.98 m, and the standard deviation is 1.06 m.

A less explored aspect of L-band microwave emission is the surface roughness effect on the multiangular brightness temperature $(T_{\mathrm {B}}^{\mathrm {p}})$ modeling and retrieval of liquid water content $(\theta _{\mathrm {liq}})$ in frozen soil. This letter investigates this effect based on a data set of multiangular ETH L-band radiometer (ELBARA-III) $T_{\mathrm {B}}^{\mathrm {p}}$ measurements performed in a seasonally frozen Tibetan meadow ecosystem. The surface roughness effect is first investigated via comparing the performance of the HQN model and Shi’s parameterization of the integral equation model in simulating the measured $T_{\mathrm {B}}^{\mathrm {p}}$ signatures. Overestimations are noted for the two model simulations at the vertical polarization in comparison to the ELBARA-III measurements, and Shi’s model with Gaussian autocorrelation function shows better performance especially for the vertical polarization at large incidence angles. The HQN model is then calibrated with the multiangular $T_{\mathrm {B}}^{\mathrm {p}}$ measurements, which leads to $h = 0$ and $Q > 0$ that depends on the polarization. As such, the noncoherent emission contribution to cross-polarization mixing can be accounted for by the HQN model. Furthermore, $\theta _{\mathrm {liq}}$ retrievals are derived from the multiangular $T_{\mathrm {B}}^{\mathrm {p}}$ measurements using the default and optimized HQN model and Shi’s model and compared to the in situ $\theta _{\mathrm {liq}}$ . Unbiased root-mean-square errors of less than 0.025 m3 m−3 are obtained for these retrievals, which are well within the satellite mission requirements. This study demonstrates that the multiangular $T_{\mathrm {B}}^{\mathrm {p}}$ modeling can be enhanced with site-specific calibration of the HQN model that also leads to the improvement of the $\theta _{\mathrm {liq}}$ retrievals, and consideration of polarization mixing is necessary for L-band emission modeling.

Withthe advent of the 5G era, the demand for data communication is increasing explosively. Extending the L-band gain bandwidth is considered to be the most direct and effective approach to increasing communication capacity. However, the signal excited state absorption (SESA) prevents the L-band gain from extending to longer wavelength. In this report, Er3+ and Ce3+ are introduced into the phosphosilicate fiber to regulate the SESA. The results show that the addition of Ce3+ into the phosphosilicate fiber can weaken the effect of SESA and extend the L-band gain bandwidth. The SESA of the Er3+/Ce3+ co-doped phosphosilicate fiber do not begin until 1620 nm, which is shifted and suppressed efficiently. The longest wavelength of the Er3+/Ce3+ co-doped phosphosilicate fiber is extended to 1623 nm. This result provides an effective approach to realizing the extended L-band amplification.

The moisture retrieval depth is commonly held to be the approximately top 5 cm at L-band (~21-cm wavelength/1.41 GHz), which is seen as a limitation for hydrological applications. A widely held view is that this moisture retrieval depth increases with wavelength, ranging approximately from one-tenth to one-fourth of the wavelength. Accordingly, P-band (~40-cm wavelength/0.75 GHz) is under investigation for soil moisture observation over a deeper layer of soil. However, there is no accepted method for predicting the moisture retrieval depth, and there has been no study to confirm that the actual retrieval depth at P-band is indeed deeper than that achieved at L-band. Consequently, this research has estimated the moisture retrieval depth from theory and compared with empirical evidence from tower-based observations. Model predictions and experimental observations agreed that P-band has the potential to retrieve soil moisture over a deeper layer (~7 cm) than L-band (~5 cm) while maintaining the same correlation. However, an alternate interpretation of experimental results is that P-band has a larger correlation with soil moisture (accuracy of retrieval) than L-band but for the same 5-cm moisture retrieval depth. The results also demonstrated the increasing trend of the moisture retrieval depth for increasing wavelength, with the potential to achieving a moisture retrieval depth greater than 10 cm for P-band below 0.5 GHz. Importantly, model predictions showed that moisture retrieval depth was not only dependent on soil moisture content and observation frequency, but also the moisture gradient of the profile.

In this article, we present a statistical narrowband mobile satellite maritime propagation channel model at the ${L}$ -band based on empirical observations using GPS $C/N_{0}$ measurements from a receiver onboard a vessel in different sea conditions. The model is fully parameterized for all possible elevation angles. In the measurements, we have used a low-gain, 6.2 dBi, hemispherical antenna. The parameters provided, thus, are valid for this and similar antenna gains.

Purpose To achieve right-hand circular polarization (RHCP), a 3-dB Wilkinson power divider with a λ/4 phase shifter is used. The crossed-dipoles are placed at almost λ/4 elevation on the ground plane and connected to two coaxial cables. Experiments show that the impedance bandwidth of 49.40% (913.7–1,513.1 MHz) and axial ratio bandwidth (ARBW) of 22.88% (1,145.8–1,441.8 MHz) are achieved. Design/methodology/approach In this study, a wideband crossed-dipole antenna with circularly polarized (CP) radiation for L-band satellite and radar applications is presented. The proposed CP antenna comprises two orthogonally placed printed dipoles, a quadrature coupler and a box-shaped ground plane. Findings Furthermore, by fixing the box-shaped ground plane under the radiators, 5.13 dBic RHCP peak gain at 1,300 MHz and maximum half-power beamwidth (HPBW) of 84.5° at 1,170 MHz are realized for the antenna. Originality/value Eight metallic walls are connected to four corners of the substrate to stabilize the radiation properties in this study. Results show that the ARBW and front-to-back ratio are improved and the maximum HPBW around 127° across the operating frequency band is achieved. The proposed CP antenna is a good candidate for Global Positioning System (GPS) L2 (1.227 GHz), GPS L5 (1.176 GHz) and air route surveillance radar system at 1,215–1,390 MHz frequency band.

The design and first experimental results of Tx and Rx L-band bandpass filters for a high-power satellite diplexer are presented in this paper. Designed in the framework of an ESA ARTES AT project, the filters are based on TM010 mode dielectric resonators. These resonators allow for better results in terms of volume occupation with respect to other dielectric resonators still maintaining high Q-factor values (>2000). Volume saving above 30% is achieved with respect to standard coaxial filters. The filter geometries and materials have been chosen in order to improve the power-handling and to cope with related critical issues for space applications (i.e. avoid any multipactor discharge in the operating RF power range and low-PIM response). Measurements of Tx filter show good correlation with the design in terms of central frequency, BW, and unloaded Q-factor (almost 3000). Measurements of Rx filter show a worse correlation with the design in terms of filter response shape. This is ascribed to size tolerances of one of the filter resonators. Multiple analyses are ongoing to remove this degradation in the final engineering model.

Variations in gain with the least noise figure and noise are the challenging issues for the hybrid amplifier. This is resolved in the proposed model of 400×10 Gb/s superdense wavelength division multiplexing (SD-WDM) system with a channel spacing of 100 GHz. Further, we evaluate the performance in terms of gain, flattened gain, and noise figure, respectively. We achieve the highest gain equal to 38.55 dB and most suitable rating of flattened gain > 20 dB, with a least variation of noise of 0.05 dB employing a dual pumping at 1550 nm (600 mW) and 1555 nm (459 mW) respectively. We also report a least noise figure of −2 dB with the help of a hybrid amplifier without using any cost effective and gain equalizer filter technique.

The dual polarimetric study including degree of polarization (mL) and energy span (λ1+ λ2) for vegetation targets infer the accuracy of vegetation algorithms. The Sentinel − 1 A and ALOS − 2 satell...

The present study addresses the potential of airborne NASA – ISRO Synthetic Aperture Radar (NISAR) compact polarimetric (CP) data to discriminate the land cover classes emphasizing the urban area for parts of Ahmedabad city, India. This has been carried out by generating m-Delta, m-Chi and m-Alpha polarimetric decompositions using Compact Polarimetric L band NISAR data. In Hybrid Polarimetric data, both m-delta and m-chi decompositions have almost the same formulations, indicating that delta and chi play the same roles as indicators of single-bounce and double-bounce scattering. However, M-delta seem preferable over M-chi as stoke parameter delta is highly susceptible towards orientation. It is also observed that building orientation and density has effect on scattering pattern. This is attributed to the target orientation which is parallel to the look direction of the sensor. Supervised classification of m-Delta decomposition was carried out and over all accuracy of 81.1 % was observed in the study.

The Doppler signature of a man walking in a forested area analysed at L‐band is presented here. The aim is twofold: to assess the best time‐frequency distribution to characterise the activity; to highlight the similarity of the simulated data to the measured ones to validate the simulation tool. Indeed, the Doppler‐Time (DT) signal variation represents the main characteristic of Artificial Neural Networks (ANNs) for classification. The more accurately the DT characterises the activity, the higher the machine’s accuracy in classifying it. Besides, in the training data frame, reliable simulated models may supply the amount of data needed by ANN applications. Thus, a short‐time Fourier transform (STFT), a reassigned spectrogram (RE‐Spect), and a pseudo‐Wigner–Ville distribution have been applied to the measured and simulated data. The measurements have been performed using a bistatic radar working at 1 GHz. Then, the measurement setup has been replicated in simulation, and 3‐D human bodies walking in free space have been computed using physical optics. The results show that the STFT is the most suitable time‐frequency method for recognising and classifying the walk. Moreover, the simulated data are in agreement with the measured data, regardless of the chosen Cohen’s technique.

We present the theoretical study of polarization-maintaining multi-core few-mode fiber (PM MC-FMF) with a cladding diameter of 125 μm, in order to secure the maximum number of independent spatial channels arising in the single fiber. By taking both the inter-core crosstalk (XT) and the intra-core mode coupling into account, we identify that the PM five-core three-mode fiber is able to provide 19 parallel channels without the need of MIMO signal processing. After the numerical optimizations, the inter-core XT of MC-FMF is less than −30 dB/100km, due to the use of trench-assisted heterogeneous core distribution. Meanwhile, the effective refractive index (RI) differences among both spatial modes and polarization modes are more than 8 × 10−4 and 3.26 × 10−4 over the C+L band, respectively, due to the introduction of stress and geometric birefringence. Moreover, the cladding diameter of such MC-FMF is the same as that of the standard single-mode fiber (SSMF), leading to a convenient upgrading from the SSMF to the MC-FMF.

We report on the generation and transmission of 30 GHz millimeter-wave (MMW) beat-tone signals employing external- (EIL) and self-injection-locked (SIL) InAs/InP quantum-dash based dual-wavelength laser (QD-DWL) sources emitting in mid L-band. Later, successful transmission of 2 Gbps quadrature phase-shift-keying (QPSK) signal over clear weather conditions on 2 m wireless (WL), and hybrid channels consisting of 20 km single-mode fiber (SMF) and 2 m WL, and 20 km single-mode fiber (SMF), 5 m free-space-optics (FSO) and 2 m WL, are demonstrated employing both MMW sources, with a slight ∼1.4 dBm extra received optical power requirement from SIL QD-DWL. Lastly, examining the effect of dusty weather conditions on the MMW transmission over 20 km SMF, 0.9 m FSO and 1 m WL hybrid channel, considering both EIL and SIL sources, showed maximum visibility range (V) of 12 ± 2 m and 16 ± 2 m for successful transmission, respectively. These investigations reinforce the simple, cost-effective, and energy-efficient SIL QD-DWL as a candidate L-band millimeter-wave (MMW) source compared to the EIL counterpart in 5G and next-generation radio-over-fiber wavelength-division multiplexing networks.

This research work conducted a design and simulation of an ultra-low power all-optically tuned nonlinear ring resonator-based add-drop filter. The purpose of this study is to investigate a CMOS-compatible nonlinear material system for an optical filter with temperature resilience, polarization insensitivity, and fast and energy-efficient tunability. The all-optical tunability was achieved using an optical pump that photo-excites the high nonlinear Kerr effect in the device material system. A three-dimensional multiphysics approach was used, combining the electromagnetics and thermo-structural effects in the filter. Hybrid graphene on an ultra-rich silicon nitride ring resonator-based filter enabled the realization of an ultra-high tuning efficiency (0.275 nm/mW for TE mode and 0.253 nm/mW for TM mode) on a range of 1.55 nm and thermal stability of 0.11 pm/K. This work contributed to the existing literature by proposing (1) the integration of a high Kerr effect layer on a low loss, high index contrast, and two-photon absorption-free core material with an athermal cladding material system and (2) the use of a cross-section shape insensitive to polarization. Moreover, the tuning mechanism contributed to the realization of an all-optical on-chip integrable filter for Dense Wavelength Division Multiplexing systems in the less occupied L band.

A persistent challenge in the measurement of soil moisture from satellites stems from the inherently low spatial resolution using active or passive system. The lobe differencing correlation radiometer (LDCR) on a small unmanned aerial system (sUAS) is shown to provide a capability to measure soil moisture at high spatial resolution for a range of scientific and operational purposes. Flight tests of LDCR on a fixed wing sUAS were performed at the Canton, Oklahoma Soilscape site in September 2015, and Irrigation Research Foundation (IRF) in Yuma, Colorado, in June 2016. The LDCR design and performance are discussed, and the calibration using both preflight lab test data and in-flight data over a calm pond was performed to calibrate the radiometer. Radio frequency interference (RFI) from the sUAS platform was observed and mitigated. The LDCR sampling processes are detailed and an implementation of the $\tau -\omega $ vegetation correction model along with a semiempirical surface roughness correction model incorporating a full-domain soil moisture mapping algorithm is presented. The algorithm uses a weakly nonlinear observation operator suitable for irregular sUAS flight trajectories that maps volumetric soil moisture (VSM) on a user-defined product grid from the sUAS sampling grid. Using LDCR radiometric and thermal measurements, along with Landsat-based vegetation water content (VWC) and soil texture information, soil moisture was mapped at decameter spatial resolution. The retrieved VSM data are favorably compared with in situ VSM measurements and irrigation records. A method for determining LDCR VSM estimation errors is developed to quantify the mapping algorithm accuracy and assess the impact of error sources.

An ${L}$ -band all cavity axial extraction (ACAE) relativistic magnetron (RM) with a split cathode is proposed. The proposed RM is driven by virtual cathode that formed by axial flow of electrons from two conical emitters at both sides of slow wave structure, which is different from other RM that powered by radial flow of electrons from a cathode inside the interaction region. This cathode structure is simple but practical to generate a squeeze state electron in an RM with almost all the output structure. To improve the output performance, the anode blocks are modified with additional sections at both ends. Particle-in-cell (PIC) simulation results illustrate that when this tube is applied with a diode voltage of 600 kV, an average output microwave power of 1.6 GW can be obtained. Comparing with ACAE-RM using a conventional transparent cathode, the power conversion efficiency is improved from 47% to 67%.

An unexplored aspect of L-band microwave emission is the impact of soil moisture and soil temperature (SMST) profile dynamics on diurnal brightness temperature ( $T_{\mathrm {B}}$ ) signatures of frozen soil. This study investigates this effect by comparing the $T_{\mathrm {B}}$ simulations of layered ( $T_{\mathrm {B,l}}$ ) and uniform ( $T_{\mathrm {B,u}}$ ) soils using a newly developed integrated land emission model. The multilayer Wilheit model and the single-layer Fresnel model are adopted to compute the smooth soil reflectivity for the layered and uniform soils, respectively. A four-phase dielectric mixing model is used to calculate the soil permittivity ( $\varepsilon _{s}$ ). A data set of concurrent ELBARA-III $T_{\mathrm {B}}$ and SMST profile measurements performed in a seasonally frozen Tibetan meadow ecosystem is used for the analysis. The simulated $T_{\mathrm {B,l}}$ considering SMST profile information captures well the ELBARA-III measurements with low biases (≤6 K) and high correlations ( $R^{2}\ge0.88$ ). $T_{\mathrm {B,u}}$ produced based on the Fresnel model using the soil moisture of 2.5 cm is more consistent with the $T_{\mathrm {B,l}}$ . The sensitivity test of averaging SMST profile below 2.5 cm leads to maximum differences of 2 K in $T_{\mathrm {B,l}}$ simulations, indicating that the $T_{\mathrm {B}}$ variations are primary dominated by the SMST dynamics at the surface layer. A sensitivity test of the Wilheit model to different $\varepsilon _{s}$ parameterizations shows that the dielectric model of Zhang et al. is comparable to the four-phase dielectric model in simulating $T_{\mathrm {B,l}}$ , while the Mironov et al. ’s model demonstrates larger biases for frozen soil with, on average, 2.2% clay content, 49.7% sand content, and a bulk density of 1 $\text{g}\cdot $ cm−3.

This work presents a gallium nitride (GaN) high electron mobility transistor (HEMT)–based cascaded multistage power amplifier (MPA) in class‐AB for L‐band radar applications. The purpose of this endeavour is to develop an MPA using GaN HEMT devices to achieve optimised parameters such as high gain, high power, better efficiency, and linearity in a compact size. In an MPA design with multiple stages, oscillations are common owing to unwanted high gain at the lower frequency range. To overcome this issue, we introduced interstage harmonic termination networks as a novel approach to suppress high gain at low frequencies, which are prone to oscillations. The proposed cascaded MPA provides the maximum radio‐frequency output power of 89 W and a power gain of 52 dB with an associated power‐added efficiency of 51%. Second and third harmonic levels are −32.5 and −37 dBc, respectively. Two‐tone measurements are performed with a frequency separation of 10 MHz, and an intermodulation level of less than −33 dBc is achieved.

Propagation path loss exponent is an important component of system design, and knowing the values helps to avoid surprises when the actual service begins. The path loss exponent is known to be critical in establishing the coverage of any new cellular network. Estimating the path loss exponent of any environment requires raising new data sets, which can be accomplished by conducting experiments. With this objective, the present study reports the L-band signal RSS level measurements of 6 GSM base stations in the urban, suburban and rural environments of Ondo and Ekiti States in the Southwestern region of Nigeria. Using a Sony Ericsson TEMS phone monitoring device—connected to a laptop equipped with TEMS software and base station cell reference—and a GPS device, RSS measurements were performed in each sector of the base station up to 1200 m, employing a single sector verification method. The values of path loss exponents were computed from the deduced values of path loss at 50 m intervals up to distances of 1200 m. Close to the base station, the following exponent values were observed—between 2.0 and 3.8 in the urban environment, 2.0 to 2.8 in the suburban environment while for the rural environment, 1.5 to 2.6 we're observed. After the breakpoint distance, higher path loss exponent values of up to 6 was recorded in the urban environment, exponent value of up to 4.3 was observed in the suburban environment and up to 3.5 exponent value in the rural environment. It was also observed that the rural environment presented the longest breakpoint distance of 500 m. The high path loss exponents observed, especially in the urban environment, could cause GSM operators to rethink the margins they have provided. This study is useful for the design of upcoming network systems in these regions and in similar regions.

Secondary forests (SFs) are one of the major carbons sinks in the Neotropics due to the rapid carbon assimilation in their above-ground biomass (AGB). However, the accurate contribution of SFs to t...

The interaction of radar signals with a planetary surface is critical for the utility of radar data. Herein, a power‐law roughness spectrum is used to model the roughness and an inhomogeneous vertical permittivity to describe the dielectrics from the surface of Mars. Numerical simulations of depolarised radar backscattering are then conducted. To gain a more complete picture of depolarised characteristics, a wide range of surface roughness is considered. Results reveal that the depolarised backscattering is sensitive to the dielectric profiles with –10 dB is observed. The polarization conversion ratio, the ratio of depolarisation to total polarization backscattering, is a sensitive indicator of dielectric profiles and roughness, and thus is useful in retrieving dielectric profile.

Present paper focuses on design and simulation of an inset fed rectangular microstrip patch antenna for GPS applications. The proposed antenna is designed at frequency 1.9 GHz which comes in L-Band region and simulated using Electromagnetic Simulator such as HFSS simulation software with three different dielectric substrates and comparing their performance characteristics such as gain, bandwidth, beam width, VSWR and return loss. The simulation results shows that the maximum bandwidth is obtained with FR4 substrate and the minimum bandwidth is found with Arlon AD320 substrate, where as the maximum gain obtained with air (vaccum) substrate. The proposed antenna has been designed for the range of 1.9 GHz and which is highly suitable for GPS applications.

Two-dimensional (2D) materials have attracted extensive attention for use in fiber lasers for pulse generation due to their unique nonlinear optical properties. While 2D materials with tunable band...

This letter focuses on modeling and studying the RF interference between a civilian Inmarsat FB emitter at 1627 MHz (culprit) and a GPS L1 band maritime system at 1575 MHz (victim) on close antennas proximity onboard a submarine. Once predicted the RFI, we propose the design of an adequate mitigation for it. The chosen platform to host this study is a 3D model of the U.S. Navy retired Los Angeles SSN-688 original class submarine. The proposed methodology consists on calculating through numerical 3D electromagnetic simulation the electromagnetic decoupling between culprit and victim’s antennas on different antenna placement scenarios onboard the SSN-688’s masts; modeling a typical GPS front-end receiver simultaneously excited with both the interferer signal after decoupling, and the GPS weak signal reception; to observe the RFI effects on the modeled receiver circuit; and to finally propose and design an adequate filter to control and mitigate the interference. The result is a pre-filter, to be connected to the GPS receiver front-end before the GPS’s low noise amplifier, which attenuates the Inmarsat signal on the rejection band below the RFI threshold level and inserts a low insertion loss on GPS pass band.

We investigate high-throughput, multi-band transmission in a 4-core multi-core fiber (MCF) with the same 125 μm cladding diameter of standard single-mode fiber (SMF). A single wideband comb source is used to transmit up to 561 wavelength channels with 25 GHz spacing over a 120 nm bandwidth in S, C, and L bands. We demonstrate a maximum decoded throughput of 610 Tb/s in PDM-256QAM and PDM-64QAM signals over a 54 km fiber, transmitting more than 155 Tb/s in a single core and measuring a per-core average throughput exceeding record transmission demonstrations in SMF. In addition, we use noise loading measurements to characterize the achievable signal quality across the wideband transmitter. These results show that a single comb source can enable high-spectral efficiency modulation over wide bandwidths and further that low-core count homogeneous MCF technology can offer the same transmission performance as single-mode fibers without sacrificing mechanical reliability, and still offering the benefits of shared resources and greater efficiency that drives SDM technologies.

Excessive exploitation of underground mine resources has caused serious land subsidence in China. This paper focused on monitoring and modeling the single subsidence basin in coal mining area based on SAR interferometry (InSAR). The optimum InSAR processing strategy to monitor the mining subsidence was built to obtain the land subsidence with large deformation. And a method of three-dimensional mathematical modeling of single subsidence basin based on InSAR measurements was presented. Using Jining Coalfield (China) as the study area, we acquired 7 L-band PALSAR images from January 2008 to February 2010 to monitor the land subsidence in Jining Coalfield. The deformation maps in Jining Coalfield in different periods were obtained. Taking the Geting Coal Mine within the Jining coalfield as an example, we finely analyzed and interpreted the deformation maps. Compared with the simultaneous filed measurements, the precision of deformation measurement using D-InSAR in mining area was analyzed. The root mean square error was 1.37 cm. The method of fine interpretation and analysis for a single subsidence basin was established. The experiments have proved that InSAR technique with L-band InSAR data is suitable for monitoring mining subsidence with large deformation. And the 3D mathematical modeling method could be used for the single subsidence basin in coal mining area.

Waves much shorter than those measured by operational systems make significant contribution to the ocean surface roughness. This article describes a method to obtain the L-band tilting ocean surface roughness using wind speed and windsea dominant wave period coupled with a wind–wave spectrum model. Examples are presented with wind and dominant wave data from ocean buoys and hurricane hunters. Several related issues are discussed: high-frequency wave spectrum, integration limit, swell contribution, and measurements in extreme winds: 1) it is well known since the 1970s that with stationary sensors, extending the frequency range in measuring elevation spectrum does not yield useful short-wave information because of the low signal level and large Doppler frequency shift involved in measuring short waves. 2) Low-pass mean square slopes (LPMSSs) integrated to 5 and 11 rad/m are computed to quantify their difference as a function of wind speed and inverse wave age (IWA). The normalized difference decreases with increasing wind speed and decreasing IWA. 3) Swell contribution to the L-band LPMSS is almost negligible for wind speed greater than 5 m/s (less than 5% in 99% of observations). In low-wind conditions (wind speed less than 5 m/s), the swell contribution is difficult to assess because of inaccuracy in identifying the weak windsea system. 4) The coarse resolution in National Data Buoy Center (NDBC) wave spectra causes large data scatter in the computed LPMSS in very high winds (greater than 20 m/s). A mitigating solution is offered.