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A new circular patch antenna with a novel metamaterial structure that achieves high bandwidth and positive gain across the operating band. The proposed antenna was Designed by incorporating three split ring resonators into the patch and fabricating it with 15 ×10 ×1.6 mm3. The use of a metamaterial structure with negative permittivity and permeability reduced mutual coupling in a wideband antenna. The designed antenna shows the isotropic nature at 9.71 GHz in the operating band from 8.80 to 12.89 GHz for X band applications specifically for detecting objects using radars. The optimetrics technique analyzed impedance matching with a good return loss of -30 dB. In comparison to previous works, miniaturization achieved up to 81.94%. The efficiency of 95.6% and isotropic pattern were also achieved at 9.71 GHz using HFSS020R2.

Unlike the original Cloude-van Zyl decomposition of reflection symmetric polSAR data, a recently suggested version of the decomposition for full/quad pol data relies on the Cloude-Pottier mean alpha angle (ᾱ) to characterize the scattering mechanism. ᾱ can be calculated from the eigenvectors of the coherency matrix. By means of the eigenvector-eigenvalue identity (EEI) we can avoid the calculation of the eigenvectors. The EEI finds ᾱ by means of eigenvalues of the 3×3 coherency matrix and its 2×2 minor(s) only and is well suited for fast array based computer implementation. In this paper with focus on computational aspects we demonstrate fast EEI based determination of ᾱ on X-band F-SAR image data over Vejers, Denmark, including a detailed example of calculations and computer code.

In this paper, a broad band A-sandwich radome wall structure based on band-pass FSS (frequency selective surface) is proposed for an airborne radar applications. The FSS structure having two square conducting rings, which are embedded on either side of core layer. The conventional and proposed FSS based radome wall is analyzed with different incidence angles (0°, 10°, 20° and 30°) for both TE and TM polarization. The radome wall structure consist of a low density Nomex honeycomb core layer sandwiched between two high density Quartz skin layers. The structure shows the percentage impedance bandwidth of 40.8 % in the frequency range from 7.8GHz to 11.8GHz with sharp roll-off characteristics. The proposed novel approach involves high frequency unit cell simulation, which is carried out using EM Simulation Tool. To understand the practical behavior of the proposed structure for radome application the conformal analysis has been also carried out, with respect to different radius. The superior EM performance of the proposed broadband novel radome wall structure makes it suitable for the design of airborne radome.

In this paper, a transparent parasitic slot antenna is proposed for 1U and 2U CubeSats. The proposed antenna is low profile and present physical size suitable for all CubeSat configurations. Moreover, the proposed study introduces a tradeoff between two electromagnetic/ Satellite aims. The first one is about space for the CubeSat solar panels, which is preferred to be wide for producing the maximum energy possible. The second is about the use of CubeSat top face for increasing the antenna peak gain at X-band. The proposed parasitic slot antenna is designed and optimized using ANSYS HFSS and Quasi Newtonian method. The obtained results show that the antenna gain is increased by about 7.0 dBi and 8.0 dBi for both 1U and 2U CubeSats, respectively. In addition to that, the proposed antenna gives large impedance bandwidth of about 600 MHz at X-Band. In general, the constructed transparent slot antenna with parasitic elements mounted on both 1U / 2U CubeSat box presents high antenna performances that make it very candidate for unlimited lifetime CubeSat Communication.

In this paper, a novel digitally reconfigurable unit-cell and $4\times 4$ transmitarray operating at X-band is proposed that allows the implementation of beamforming and polarization conversion operations in a programmable way. The lower layer of transmitarray responsible for beam steering consists of two PIN diodes and a circular type patch which has two states of operations with 0 and $\pi $ phase responses which we name “State1” and “State2”. “State1” and “State2” can be represented by a digital notation as “1” and “0” elements. Similarly, the upper layer of the transmitarray responsible for polarization conversion operation consists of two states of operation which we name as “State3” and “State4”, respectively. “State3” and “State4” also can be represented by digital notations as “1” or “0” elements. By coding “0” and “1” elements for the lower side of the transmitarray in a 1-bit sequence, we can steer the beam in our desired direction. Similarly, by coding “0” and “1” elements in a 1-bit sequence element for the upper layer, we can get X-polarized and Y-polarized beams. Combining the upper layer 1-bit sequence and lower layer 1-bit sequence, we can get both polarization conversion and beam steering simultaneously. A $4\times 4$ array with our proposed unit cell was designed and fabricated. A good agreement between simulated and measured results was observed. The proposed design is a promising concept because it can be fabricated using the conventional fabrication process, it is cost-effective compared to conventional phased array antenna for satellite and radar applications. A $4\times 4$ array was taken just to check the transmission and reflection coefficients of the proposed unit cells. A very small transmitarray was manufactured and experimentally characterized just as a proof of concept, to verify that the unit cells work properly.

Data from TanDEM-X in single-pass and bistatic interferometric mode together with the interferometric water cloud model (IWCM) can provide estimates of forest height and stem volume (or the related above-ground biomass) of boreal forests with high accuracy. We summarize results from two boreal test sites using two approaches, i.e., 1) based on model calibration using reference insitu stands, and 2) based on minimization of a cost function. Both approaches are based on inversion of IWCM, which models the complex coherence and backscattering coefficient of a homogeneous forest layer, which includes gaps where free-space wave propagation is assumed. A digital terrain model of the ground is also needed. IWCM is used to estimate forest height or stem volume, since the two variables are assumed to be related through an allometric equation. A relationship between the fractional area of gaps, the area-fill, and stem volume is also required to enable model inversion. The accuracy of the stem volume estimate in the two sites varies between 16% and 21% for height of ambiguity

A compact quad-band circularly polarized (CP) G-shaped printed antenna with square slot is proposed in this paper. Two semicircular notches have been etched from lower periphery of the ground to increase the impedance bandwidth (IBW). In order to increase significantly the axial ratio bandwidth (ARBW), a spring-shaped notch is etched from the upper periphery of the ground. For further increase of ARBW and better impedance matching, another notch is etched from G-shaped radiating element. The proposed design exhibits simulated IBW = 22.046 GHz (8.954–31 GHz) with the center frequency fc = 20 GHz, and the measured IBW below –10 dB is from 8.8376 to 20 GHz. The IBW above 20 GHz are not measured due to limitations of the available VNA. The ARBW are 306.3 MHz (fc = 11.6 GHz), 363.1 MHz (fc = 21.3 GHz), 380.7 MHz (fc = 27.6 GHz), and 332.2 MHz (fc = 28.6 GHz), which are within the range of IBW. The maximum simulated peak gain is 5.46 dBi at 25.7 GHz. The proposed antenna is suitable for applications in the X-, K- and Ka-bands in the field of wireless communication.

In this paper, we present a modified UWB antenna with hexagonal slotted ground plane inspired with a double combined symmetric T-shaped slots and dual rotated L-shaped strip for dual band notched characteristics. Initially, the operating frequency range is from 3GHz to 12 GHz. To eliminate the unwanted C-band (3.625-4.2GHz) and the entire uplink and downlink of X-band satellite communication systems (7.25 -8.39 GHz) frequency bands, we are investigating the conventional UWB patch antenna and loaded it with a mentioned strips and slots respectively. The performances of the antenna are optimized both by CST Microwave Studio and Ansoft HFSS. To further analyze the parametric effects of the slots and strips, the surface current distribution is presented and discussed. The antenna gain versus frequency gives an acceptable value except the notched band regions, these values are reduced from its normal to be a negative in the notched bands (3.625-4.2GHz) and (7.25 to 8.39 GHz).

In this paper, a fully-integrated dual-mode X-band radar transceiver that supports Doppler radar and frequency modulated continuous wave (FMCW) radar is proposed. To remove large off-chip DC-blocking capacitors in the Doppler mode, the double-conversion technique and local oscillator (LO) chopping technique are introduced. These techniques remove the DC offset and makes the transceiver more robust to the TX to RX leakage. In addition, they also improve the noise figure (NF) by filtering out 1/f noise of the analog baseband. The FMCW radar is realized using a direct-conversion receiver and a chirp generator. The chirp generator consists of a frequency sweep generator (FSG) and a fractional-N phase-locked loop (PLL). All the analog baseband components including a programable gain amplifiers (PGA) and 1/R4 range compensation filters are integrated on the chip as well as a bandgap and low-dropout regulators. The operating frequency is from 9.7 to 12.3 GHz, which consumes 216 mW in Doppler mode and 201.6 mW in FMCW mode from a 1.2-V supply voltage. The maximum chirp bandwidth is 750 MHz and the maximum receiver gain is 76 dB with 6-dB gain step. The chip size of the transceiver is 7.68 mm2 including all the pads.

Design, development, and measurements of X-band patch antennas for a CubeSat platform are presented in this paper. The challenge was in the design of circularly polarized patch antennas suitable for building an array since the goal is to achieve highest possible radiation efficiency. Therefore, six antenna designs were developed which can be differentiated by the number of PCB layers and by the method of excitation. Also, for achieving circular polarization two shapes were considered, a corner truncated square patch and a nearly square patch. The characteristics of the developed antennas were analyzed and measured showing the advantages and disadvantages of certain designs. Based on the analysis of measured results we reached guidelines that will be used further for designing the full X-band array.

Development of satellite and radar applications has been continuously studied to reach the demand in the recent communication technology. In this study, a new oval-square-shaped split-ring resonator with left-handed metamaterial properties was developed for C-band and X-band applications. The proposed metamaterial was fabricated on 9 × 9 × 0.508 mm3 size of Rogers RO4003C substrate. The proposed metamaterial structure was designed and simulated using Computer Simulation Technique (CST) Microwave Studio with the frequency ranging between 0 to 12 GHz. The simulated result of the proposed design indicated dual resonance frequency at 5.52 GHz (C-band) and 8.81 GHz (X-band). Meanwhile, the experimental result of the proposed design demonstrated dual resonance frequency at 5.53 GHz (C-band) and 8.31 GHz (X-band). Therefore, with a slight difference in the dual resonance frequency, the simulated result corresponded to the experimental result. Additionally, the proposed design exhibited the ideal properties of electromagnetic which is left-handed metamaterial (LHM) behavior. Hence, the metamaterial structure is highly recommended for satellite and radar applications.

In this dissemination, a glueless compact dual port dielectric resonator antenna (DRA) is proposed for X-band applications. A prototype has been fabricated with RT Duroid substrate and Eccostock (ϵr = 10)-made DRA. The ring shaped DRA is excited by aperture coupled feeds maintaining symmetry between both the ports. Four cylindrical copper rods with four strips have been used to fix the DRA on the substrate and provide additional mechanical stability. Eight copper strips are used to provide impedance matching and impedance bandwidth (IBW) widening. The measured IBW of dual port DRA is 10.5% (8.05–8.95 GHz) and maximum gain of radiator is 6.2 dBi. The proposed antenna becomes compact when the net volume of DRA is approximately 3.5 cm3 and the volume of the substrate is 2.88 cm3, with a surface area of 36 cm2 and operating in X-band, which finds applications in satellite communication, weather radar, synthetic aperture radar, and telemetry tracking and control.

In this study, the quantitative precipitation estimation (QPE) capability of three X-band dual-polarization phased array radars (PAR) in Guangzhou, South China, was demonstrated, with an S-band operational dual-polarization radar as the benchmark. Rainfall rate (R) estimators based on the specific differential phase (KDP) for summer precipitation for both X-band and S-band radars were derived from the raindrop size distributions (DSDs) observed by a 2-dimensional video disdrometer (2DVD) in South China. Rainfall estimates from the radars were evaluated with gauge observations in three events, including pre-summer rainfall, typhoon precipitation, and local severe convective precipitation. Observational results showed that radar echoes from the X-band PARs suffered much more severely from attenuation than those from the S-band radar. Compared to S-band observations, the X-band echoes can disappear when the signal-to-noise ratio drops to a certain level due to severe attenuation, resulting in different estimated rainfall areas for X- and S-band radars. The attenuation corrected by KDP had good consistency with S-band observations, but the accuracy of attenuation correction was affected by DSD uncertainty and may vary in different types of precipitation. The QPE results demonstrated that the R(KDP) estimator produced better rainfall accumulations from the X-band PAR observations compared to the S-band observations. For both the X-band and S-band radars, the estimates of hourly accumulated rainfall became more accurate in heavier rainfall, due to the decreases of both the DSD uncertainty and the impact of measurement errors. In the heavy precipitation area, the estimation accuracy of the X-band radar was high, and the overestimation of the S-band radar was obvious. Through the analysis of the ZH-ZDR distribution in the three weather events, it was found that the X-band PAR with the capability of high spatiotemporal observations can capture minute-level changes in the microphysical characteristics, which help improve the estimation accuracy of ground rainfall.

Phased array technology features rapid and directional scanning and has become a promising approach for remote sensing and wireless communication. In addition, element-level digitization has increased the feasibility of complicated signal processing and simultaneous multi-beamforming processes. However, the high cost and bulky characteristics of beam-steering systems have prevented their extensive application. In this paper, an X-band element-level digital phased array radar utilizing fully integrated complementary metal-oxide-semiconductor (CMOS) transceivers is proposed for achieving a low-cost and compact-size digital beamforming system. An 8–10 GHz transceiver system-on-chip (SoC) fabricated in 65 nm CMOS technology offers baseband filtering, frequency translation, and global clock synchronization through the proposed periodic pulse injection technique. A 16-element subarray module with an SoC integration, antenna-in-package, and tile array configuration achieves digital beamforming, back-end computing, and dc–dc conversion with a size of 317 × 149 × 74.6 mm3. A radar demonstrator with scalable subarray modules simultaneously realizes range sensing and azimuth recognition for pulsed radar configurations. Captured by the suggested software-defined pulsed radar, a complete range–azimuth figure with a 1 km maximum observation range can be displayed within 150 ms under the current implementation.

This article belongs to the Collection RF and Microwave Communications A new simple design of an inverted microstrip Gap Waveguide filtering antenna integrated with two stopband filters is proposed in this work. In order to simultaneously provide filtering and radiating functions, we use the direct integration approach to cascade two periodic sets of coplanar coupled EBG resonators with a slot antenna. The analysis shows that the filters can be easily adjusted in the same feeding layer of the antenna, without extra circuitry and without modifying the lines. EBG-filters are compact and offer great flexibility in determining the frequency, width and selectivity of the rejected bands. Experimental results for an X-band filtering antenna prototype are provided showing a 7.3% transmission band centered at 10.2 GHz and a realized gain peak of 2.1 dBi. The measurements demonstrate the filtering capability of the proposed antenna, achieving rejection levels greater than 12 dB and 20 dB for the bands below and above the operation band. The proposed low-complexity design offers good performance as a filter and as an antenna, showing the essential advantages of the Gap Waveguide Technology, including low losses, self-packaging and limited cost. This work demonstrates the possibility of integrating the new coplanar EBG-filters into future Gap Waveguide antenna designs to avoid unwanted radiation, to reduce interfering signals or to provide high isolation in multiband systems. This research was funded by the Spanish Ministerio de Ciencia, Innovación y Universidades grant numbers [Agencia Estatal de Investigación PID2019-107688RB-C21 and TEC2016-79700-C2-R].

An inset fed-microstrip patch antenna (MPA) with a partial ground structure is constructed and evaluated in this paper. This article covers how to evaluate the performance of the designed antenna by using a combination of simulation, measurement, creation of the RLC equivalent circuit model, and the implementation of machine learning approaches. The MPA’s measured frequency range is 7.9–14.6 GHz, while its simulated frequency range is 8.35–14.25 GHz in CST microwave studio (CST MWS) 2018. The measured and simulated bandwidths are 6.7 GHz and 5.9 GHz, respectively. The antenna substrate is composed of FR-4 Epoxy, which has a dielectric constant of 4.4 and a loss tangent of 0.02. The equivalent model of the proposed MPA is developed by using an advanced design system (ADS) to compare the resonance frequencies obtained by using CST. In addition, the measured return loss of the prototype is compared with the simulated return loss observed by using CST and ADS. At the end, 86 data samples are gathered through the simulation by using CST MWS, and seven machine learning (ML) approaches, such as convolutional neural network (CNN), linear regression (LR), random forest regression (RFR), decision tree regression (DTR), lasso regression, ridge regression, and extreme gradient boosting (XGB) regression, are applied to estimate the resonant frequency of the patch antenna. The performance of the seven ML models is evaluated based on mean square error (MSE), mean absolute error (MAE), root mean square error (RMSE), and variance score. Among the seven ML models, the prediction result of DTR (MSE = 0.71%, MAE = 5.63%, RMSE = 8.42%, and var score = 99.68%) is superior to other ML models. In conclusion, the proposed antenna is a strong contender for operating at the entire X-band and lower portion of the Ku-band frequencies, as evidenced by the simulation results through CST and ADS, it measured and predicted results using machine learning approaches.

Silicon carbide (SiC) has good chemical resistance, excellent mechanical properties, thermal conductivity, especially in extreme conditions of application, and has proved to be a very promising electromagnetic absorption material. However, single silicon carbide cannot meet the increasing demand for high performance of absorbing materials. It has become an important research direction to combine it with other absorbing materials to improve its absorbing performance. In this study, a composite absorber material was prepared by 50 wt.% micron-sized beta-silicon carbide (β-sic) powder, mixed with a 0.2 wt.% multiwalled carbon nanotubes (MWCNTs) and 50 wt.% polyurethane (PU) substrate. The mixture was stirred and deaerated to form a slurry, and sprayed onto synthetic fabric. The results showed that the composite material was flexible, with a thickness of less than 2 mm and favorable adhesion. The results obtained by reflection graph of the radar waves, indicated that the return loss within the X-band range (8–12 GHz) was less than −40 dB, indicating favorable radar wave absorption. Therefore, composite materials could thus be used successfully as radar wave absorbers, and was suitable for stealth materials in “asymmetric warfare”.

The research vessel ‘Polarstern’, moored to an ice floe, completed a year long drift with Arctic pack ice in the autumn of 2020. During that expedition, named MOSAiC, a comprehensive data set of airborne laser scanner (ALS) and spaceborne X-band SAR images in the area of the research vessel was acquired. With successful fusion of these two measurements, we can extrapolate sea ice features from the ALS data to the entire SAR scene using a convolutional neural network (CNN). From two preliminary scenes of ALS data we are able to show this for classes of sea ice roughness. This will be the basis for more comprehensive research, once the complete data set is available.

International audience; Multitemporal synthetic aperture radar (SAR) interferometry (InSAR) is a widely used technique to measure the ground subsidence and has already shown its ability to map such phenomena on a large spatial scale with millimetric accuracy from space. In Vietnam, to have independent SAR data for surface risk applications, a new X-band SAR mission (JV-LOTUSat) has been scheduled for launch for the 2019-2020 timeframe. However, Vietnam is located in tropical regions where their conditions are impacted by strong atmosphere. The aim of this article is to provide a better understanding of the capabilities of the X-band for estimating the ground subsidence under tropical atmospheric conditions. Analysis is carried out on two stacks, TerraSAR-X and Cosmos SkyMed X-band, from 2011 to 2014 in Ha Noi. We show that the results on the ground subsidence from InSAR processing can describe consistently the subsidence area based on ground measurements. This article demonstrates that the InSAR technique can be effective at detecting and estimating the subsidence phenomena even with the X-band and under conditions typical of tropical regions. The displacement results from TerraSAR-X and Cosmos SkyMed datasets are consistent, with a correlation coefficient (R2) of 0.91 for the period during which their coverage overlaps. Groundwater overexploitation is one of the main causes of the ground subsidence in Ha Noi. This study provides strong support for the scientific potential of the X-band SAR space-borne mission in Vietnam and other tropical countries because it demonstrates the feasibility of the ground subsidence estimates by the X-band SAR, even in conditions impacted by strong atmosphere.

In the future, the need to identify and sense objects through ultra-low-power or zero-power communication mechanisms will be more crucial than now. Backscattering-based radiofrequency identification (RFID) technology could still play a major role through the possible implementation of low-power identification (ID) and communication directly over other technologies. In this work, RFID capabilities are introduced over the X-band microwave motion sensor (MMS), typically used to detect and locate objects. Specifically, the concept of offset-carrier backscattering modulation is exploited to design a 10.525 GHz RFID system where the reader is purposely and slightly modified commercial and low-cost MMS (a few euros) to make the technology actually reliable. The transponder is instead a new microwave device capable of backscattering an MMS compatible wave modulating ID code and sensor data. The proposed RFID-over-MMS system has been designed, prototyped, and tested to verify the appropriateness of the proposed approach. © 2019 IEEE.

In this study, the electromagnetic interference (EMI) shielding effectiveness (SE) of polymer composites based on natural graphite in flakes (NGF) and silicone rubber was investigated with the aim to contribute to the development of the technology of electromagnetic shielding materials. This topic has attracted great attention to the aeronautical and aerospace applications, due to the serious problems that EMI can cause to the functioning of electronic devices. According to this, the present work has produced samples of composite materials with variations on the sizes of the filler particles and composition of the samples. The electromagnetic characterization of the samples is given by the Vector Network Analyzer (VNA) in the X-band frequency range (8.2 – 12.4 GHz). The results indicate that the variation of particle sizes is determinant to the SE performance along with the X-band frequency range. Furthermore, the expansion of the range of granulometry allows controlling the curves of the peaks along the X-band.

This paper illustrates the design, modeling, and analysis of bridge type structure based capacitive RF MEMS switch with different beam thickness and materials. We have used Ashby's approach to select the best materials in each and every level which helped to improve the overall performance of the switch in terms of mechanical, electrical, and RF properties. Silicon Nitride thin film (εr = 7.8) is used as a dielectric material. The beam structure stiffness is analyzed with different materials, such as gold, titanium, and platinum, within these materials gold with high thermal conductivity and Euler-Young's modulus of 77 GPa is offering the best performance. Incorporation of meanders and perforations to the membrane helped to reduce the pull-in voltage. The proposed switch is offering very low pull-in voltage of 1.9 V. The deflection of beam thickness is tabulated for the three materials among them the 2 ţm thickness is best beam thickness for the switch for X-band applications. The switch offers best return loss (S11) of -21.36 dB, insertion loss (S12) of -0.147 dB, and isolation (S21) of -52.04 dB at 8GHz. The switch presented in this paper is preferable in X-band applications.

In weather radar applications, the Z-R relationship is considered one of the most crucial factors for providing quality quantitative precipitation estimates. However, the relationship’s parameters vary in time and space, making the derivation of an optimal relationship for a specific weather radar system challenging. This research focused on the analysis of the spatiotemporal variability of the parameters for a newly installed X-Band weather radar in Athens, Greece, by performing correlation and optimization analyses between high temporal resolution weather radar and rain gauge datasets. The correlation analysis was performed to assess the available datasets and provide the base of quality control. Multiple Z-R relationships were then derived for the following three optimization procedures; event-based relationships, station-based relationships, and a single area-based relationship. The results highlighted the region’s spatial variability regarding the Z-R relationship and the correlation between the station location and its parameter values. Moreover, it was found that stations near the coast and the front end of precipitation systems featured parameter values typical of convective type events. Finally, a single Z-R relationship was determined under a calibration and validation scheme, Z = 321R1.53,, which was validated with good agreement.

A proven CubeSat form factor is leading to increasingly ambitious payloads and mission requirements, resulting in more data products and the need for higher space-to-ground transmission rates. This thesis contributes to the Naval Postgraduate School (NPS) CubeSat project and Mobile CubeSat Command and Control (MC3) initiative to increase network capacity through X-band downlinks. The Space Systems Academic Group at NPS is developing and fielding a 6U CubeSat with an X-band software-defined radio (SDR) payload, constructed using commercial-off-the-shelf hardware and operated via the MC3 ground station network. The objective of this thesis research was verification of end-to-end compatibility between the X-band SDR payload and MC3 ground station receivers. Research, testing, and analysis determined radio frequency signal parameters and communications standards that enable transmission of data from the X-band SDR payload to the AMERGINT satTRAC SDR and Kratos quantumRadio SDR receivers. Simulation (through MathWorks Simulink models) and interoperability testing were conducted. Research culminated in demonstration of a successful baseband link from payload SDR hardware to both ground station receivers, with a QPSK-modulated, PN11 data transmission. Further functional and environmental testing will ensure the X-band SDR payload can effectively communicate on-orbit with the MC3 network. Lieutenant, United States Navy Approved for public release. Distribution is unlimited.

In this paper we present the study and obtained results of a MMIC High Power Amplifier operating in X-band. The device is designed using 250nm GaN HEMT on SiC process. The targeted specifications include pulsed operation from 8 to 10.5GHz. In pulsed mode and 28V of drain voltage, an output power more than 40W with (37-40)% PAE has been achieved throughout the bandwidth, while remarkable 52.4W output power with associated 37% PAE has been recorded at 8.75GHz for a 32V of drain voltage. The HPA stability has been studied by considering the influence of external decoupling components and dedicated testing environment.

3Cat-NXT is a 12 unit CubeSat project developed in the Nanosatlab department of the Universitat Politècnica de Catalunya which main mission is to measure the Earth?s surface soil moisture every three days for at least 3 years. The CubeSat is formed by different subsystems that are being developed to be ready if a launch opportunity comes. This work focuses on the communications subsystem. This thesis is the continuation of the design of the X-band communications subsystem started in the PAE subject of Spring 2020 semester. The work includes the design description, test and characterization of the different parts that form the subsystem that have been performed and modified from the initial design. This parts are the reception amplification stage, the transmission amplification stage, the frequency shifting stage, the digital stage and the power supply. The tests will validate the design performed and quantify the performance of each of the parts that form the communications subsystem. 3CAT-NXT es un proyecto de un CubeSat de 12 unidades desarrollado por el grupo Nanosatlab de la Universitat politècnica de Catalunya que tiene como misión principal medir la humedad superficial de la Tierra cada tres días y como mínimo durante 3 años. El CubeSat está formado por diferentes subsistemas que están siendo desarrollados para tenerlos listos para cuando haya una oportunidad de lanzamiento. Éste trabajo se centra en el subsistema de comunicaciones. Éste trabajo fin de grado es la continuación del diseño del subsistema de comunicaciones en banda X empezado en la asignatura PAE del semestre de primavera de 2020. El trabajo se centra en la descripción, testeo y caracterización de las diferentes partes que forman el subsistema que han sido implementadas y modificadas a partir del diseño inicial. Éstas partes son la etapa de amplificación en recepción, la etapa de amplificación en transmisión, la etapa de cambio de frecuencia, la etapa digital y el suministro de potencia. Los test servirán para validar el diseño desarrollado y cuantificar el rendimiento de cada parte que forma el subsistema de comunicaciones. 3CAT-NXT és un projecte d'un CubeSat de 12 unitats desenvolupat al grup Nanosatlab de la Universitat politècnica de Catalunya que té com a missió principal mesurar la humitat superficial de la Terra cada tres dies durant com a mínim 3 anys. El CubeSat està format per diferents subsistemes que estan sent desenvolupats per ternir-los llestos per quan hi hagi una oportunitat de llençament. Aquest treball es centra en el subsistema de comunicacions. Aquest treball final de grau és la continuació del disseny del subistema de comunicacions en banda X començat a l'assignatura PAE del quatrimestre de primavera de 2020. El treball se centra en la descripció, testeig i caracterització de les diferents parts que formen el subsistema que s'han implementat i modificat a partir del disseny inicial. Aquestes parts són l'etapa l'amplificació en recepció, l'etapa d'amplificació en transmissió, l'etapa de canvi de freqüència, l'etapa digital i el subministrament de potència. Els tests serviran per validar el disseny desenvolupat i quantificaran el rendiment de cada part que forma el susbistema de comunicacions.

A novel I-shaped metamaterial (ISMeTM) using split-ring resonator (SRR) for multi-band wireless communication is presented in this paper. The proposed ISMeTM unit cell structure is designed using the three-square split-ring resonators (SSRRs) and I-shaped copper strip at the center. The size of the proposed ISMeTM is 10 × 10 × 1.6 mm3 while utilizing the FR-4 dielectric substrate material. The analysis of various array arrangements, variation in the ring gap, variation in strip length, and the variation in strip width is performed to achieve the optimum results for multi-band operation. The effective permittivity, permeability, and refractive index of the unit cell have been analyzed. The design and simulation of the ISMeTM unit cell and arrays are performed using the Computer Simulation Technology (CST) Studio Suite and MATLAB. The equivalent circuit of the ISMeTM is designed using the Advanced Design System (ADS) software. The split ring’s inner loop’s gap functions as a capacitor, while the metallic ring itself functions as an inductor. Electric resonance is created by the interaction between the split ring and the electric field. The interaction of magnetic fields with metallic loops during EM propagation in the structure causes the magnetic resonance. The variation in dimensions of the structure causes the variation in the inductance and capacitance, which causes the variation in resonant frequency. The proposed design is optimized after several parametric analyses. A comprehensive analysis of 1 × 2, 2 × 2, and 2 × 4 array is also investigated. The results confirm the multi-band operation of the proposed ISMeTM. The proposed ISMeTM is suitable for the multi-band C/X/Ku-band microwave applications.

The small synthetic aperture radar (SAR) technology experimental project (S-STEP) mission aims to develop an innovative spaceborne SAR microsatellite as a constellation of 32 microsatellites featuring a high-resolution stripmap mode of 1 m. The S-STEP is a spaceborne SAR microsatellite technology demonstration program in which innovative approaches have been proposed and investigated for SAR payload system designs for improving the development speed, affordability, size and weight parameters, and quality of SAR satellite systems. In this study, the major design approach includes a bus–payload integrated flat-panel-type SAR payload based on an active phased-array antenna. This study conducted an SAR image performance analysis considering the mission requirements to validate the feasibility of the innovative SAR payload design of the S-STEP. These performance analysis results are presented to demonstrate the effectiveness of the proposed SAR payload design approach under the new space paradigm.

The objective of this research was to design, build, and test the next iteration of a low-cost, high-bandwidth X-band software-defined radio (SDR). The flight version of this iteration of the payload will be integrated into a commercially provided 6U bus to transmit and receive data, commands, and telemetry between the satellite and the MC3 network. The spacecraft reference design included two other payloads and used the Astro Digital Corvus-6 bus as the baseline for defining payload-bus-ground interfaces. This project utilized MATLAB Simulink to program the SDR. The SDR will primarily operate in the store-and-forward mode for transmissions when in line-of-sight of a ground station. The up/down convert board was designed, and manufacturing options were explored. Additionally, this project finalized the mechanical enclosure and bus interfaces. The payload aimed to maintain a 0.5U CubeSat form-factor and achieve a data rate of up to 10 Mbps with 1e-5 bit error rate. Following design and construction, the hardware and software components were subjected to functional end-to-end testing to evaluate performance. Further flight qualification will subject the payload to environmental testing to ensure survivability through launch and the expected low-Earth orbit environment. Lieutenant, United States Navy Approved for public release. distribution is unlimited

A tapered symmetrical coplanar waveguide (S-CPW) fed monopole antenna is initially studied. To achieve multiband characteristics, the radiating element of this monopole antenna is loaded with multiple narrow slots and multiple slotted stubs (MSS). The designed slot-loading monopole is further transformed into a two-antenna MIMO type with a gap distance of only 0.12λ (at 5 GHz), and thus it has a small overall size of 32 × 20 × 0.8 mm3. By deploying five concentric ring elements between the two adjacent antenna elements, the desirable isolation of better than 20 dB is yielded. As the low band and high band operation of the proposed two-antenna MIMO is 81.08% (3.3–7.8 GHz) and 40% (8.0–12.0 GHz), respectively, it can therefore satisfy the Sub-6 GHz 5G New Radio (NR) n77/78/79, IEEE 802.11ac/ax, X-band/C-band wireless and satellite applications. Furthermore, it has shown a desirable gain of above 3 dBi and a radiation efficiency greater than 69% throughout the two bands of interest.

This paper presents the electromagnetic wave (EW) absorption properties in terms of complex permittivity and permeability of novel green composites coconut fiber coir and charcoal powder materials. The samples were fabricated using the raw agricultural waste coconut fiber coir, charcoal powder, epoxy resin and hardener with varied composition. The dielectric properties of the materials were characterized using two-port waveguide measurement method over the X-band frequency (8.2 – 12.4GHz). The average permittivity value measured is approximately 3.00 with 10wt% charcoal has the highest permittivity of 3.59. Apart from that, all samples exhibit good reflection loss of better than -25dB which means more than 99% absorption rate. The result shows the composite material is a promising organic material for electromagnetic absorber applications.

Made available in DSpace on 2019-09-12T16:53:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2017 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The study of radar absorbing materials increasingly thin, lightweight and flexible has gained growing importance in recent years. In military area these characteristics allow the reduction of weight and volume of platforms, and in civilian sector these materials stimulate innovative projects of electronic and microwave devices. The present work was devoted to studying ultrathin films of Al (20-80 nm) and Cu (10-100 nm) deposited on poly(ethylene terephthalate) (PET) substrate by magnetron sputtering technique. The electrical conductivity values of the films were determined by 4 probes method, the S parameters (S-11 and S-12) were obtained by transmission line using a X-band waveguide and the skin depth calculated. The results show the dependence of the electrical conductivity with the thickness for both films. The experimental values of microwave attenuation were compared with calculated values based on the equivalent electric circuit theory. This comparison shows a good adjustment and confirms the use of electrical conductivity measurements to predict the microwave absorption behavior of ultrathin films. (C) 2017 Elsevier B.V. All rights reserved. [Costa, D. S.; Rezende, M. C.] Inst Ciencia & Tecnol UNIFESP, Rua Talim 330, BR-12231280 Sao Jose Dos Campos, SP, Brazil [Nohara, E. L.] Universidade de Taubaté (Unitau), Rua Daniel Danelli S-N, BR-12060440 Taubate, SP, Brazil

Design of a conical-disc-backed circular-polarized Archimedean single-arm spiral antenna is presented in this paper. The antenna operation covers the $X$ -band frequencies ranging from 8 to 12 GHz. The antenna makes use of a very simple structure having the single-arm spiral backed by a cone-shaped metallic disc to achieve high gain, circular polarization, and unidirectional symmetric radiation near the boresight. The diameter of the antenna only measures to 40 mm. The simulated and measured results show that the antenna has a very good impedance matching (better than −10 dB), good right-hand circular polarization (with an axial ratio of ≤3 dB) throughout the frequency range of interest, and offers a maximum peak gain of 11.4 dBiC. The presented $S_{11}$ response and radiation pattern results also show that the antenna offers excellent performance in the $X$ -band with no need of a balun. Antenna usefulness is also established through a detailed parametric study and comparison with a traditional flat disc structure. Compact size, simple design, wide range, and high gain make the proposed antenna design a good choice for radar, terrestrial communications, and satellite/aerospace communications applications.

6th IEEE-Antennas-and-Propagation-Society (IEEE AP-S) Topical Meeting on Antenna Measurements & Applications (CAMA) -- OCT 23-25, 2019 -- Bali, INDONESIA, WOS: 000528918400027, In the current work, a new Wideband Substrate Integrated Waveguide Bandpass Filter (SIW-BPF) is presented. the target is to allow vertical roaming between the X and Ku band applications. As a first step, we performed a parametric study of different etched slot geometries namely, H-Slotted, T-Slotted, and U-Slotted DGS in order to examine the effects of altering different geometrical parameters of the unit on its response. H-Slotted DGS shows the highest FBW with 82.89% on the average compared to other geometries. As a second step, the cell size and the numbers of the H-Slotted DGS were optimized with the use of finite element method with the following constraints taken into consideration: low cost fabrication, high Q-Factor, compact size and easy integration. One of the designs was chosen for fabrication to validate the designed circuit. the measured results show that our optimized filter achieves an insertion loss of 2.01 dB at 8.5 GHz, return loss higher than 11 dB and fractional bandwidth of 90.87% for a single cell and a fractional bandwidth 80.05% for multiple cells. the measured results are in good agreement with the simulated results., IEEE, IEEE Indonesia MTT AP Joint Chapter, IEEE Antennas & Propagat Soc, Univ Indonesia

Software-defined radios (SDRs) are used in many communications applications and offer flexibility in designing a communication network by offering rapid configuration changes after the radio is already produced. This is of interest in the small satellite industry, where small, lightweight, low-cost, and programmable radios will be needed for a wide array of upcoming missions of increasing complexity. Previous Naval Postgraduate School (NPS) research has produced a C-band SDR payload in a 1U CubeSat form factor. The X-band of the radio frequency spectrum offers more bandwidth, and opens the possibility of higher data rate transmissions. The objective for this project was to build an X-band SDR that can be used in future NPS research and flown on multiple platforms, including high altitude balloons, high altitude rockets, and CubeSats. This project built on previous C-band SDR research by converting the transmissions to X-band, expanding the over-air software protocol, implementing a new waveform, increasing the over-air data rate, and assessing the overall performance of the system. DoD Space http://archive.org/details/xbandsoftwaredef1094563431 Outstanding Thesis Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.

The author presents his gratitudes to Isik University for the encouragement of him to present the paper in the conference of PGSRET-2019 and also the financial support of him. Design and simulation of a microwave wideband microstrip unit element bandpass matching network is presented, potential use might be a broadband WPT (microwave wireless power transfer) application in X-band frequencies (8-12 GHz). The source of the main energy can be wind, fossil, tidal, solar, nuclear, hydro etc. and the main energy can be converted from DC to microwave energy which then can be transmitted via the proposed WPT circuit towards a few or a network of a multiple microwave harvester receivers located at a near or far field from the main source. In the work, a bandpass matching network (BPMN) composed of microstrip "unit elements (UEs)" is designed to operate along the whole X-band (8-12 GHz). Designed BPMN is excited by an X-band commercial PA (power amplifier) MMIC (monolithic microwave integrated circuit) packaged chip, and it is loaded by an X-band microstrip patch antenna. A bond wire soldered between the RF output pad of MMIC chip and the input pad of the BPMN has an equivalent LC parasitic impedance assumed to be the generator complex impedance that must be compensated in a typical matching problem. SRFT (simplified real frequency technique) is used in the design of the matching network that compensates the effect of bond wire and very good agreement found between the theoretical design and simulations done in MWO (AWR). Int Islam Univ Gazi Univ, Tech Fac Int Islam Univ, Fac Engn & Technol Publisher's Version WOS:000611393300021

This paper reports an in-field experiment of a photonics-based coherent MIMO radar network. The use of photonics guarantees the coherence of the transmitted and received RF signals, and allows remoting the antennas exploiting deployed optical fibers, thus a MIMO approach can be applied on a network of widely distributed coherent radars. In the in-field experiment, a photonics-based radar core connects two transmitters and two receivers, with 100-MHz bandwidth signals in X-band, observing a collaborative target. The results demonstrate an improvement in radar precision, and envisage real applications wherever fiber is available for deploying the radar network.

Power divider and combiner structures are the necessary and crucial passive components in order to reach high power levels for the microwave applications. The improvements in the RF/Microwave systems in the past decades have led to increasing demand for the compact, high performance power divider/combiners. In this thesis, four-way offset power divider/combiner, two-way ring power divider/combiner, three-way phase shifted Wilkinson power divider/combiner and four-way corporate power divider are designed at 8-12 GHz frequency band by using miniaturization techniques. Their analytical solutions are presented, and design procedures are explained using Advance Design System (ADS) software environment. These divider and combiner structures are fabricated using Bilkent University Nanotechnology Research Center (NANOTAM)’s Gallium Nitride (GaN) on Silicon Carbide (SiC) process. Details of the fabrication steps are demonstrated. On-wafer measurements of the designed divider and combiner structures are performed in NANOTAM laboratories are presented. Measurement and simulation results for insertion losses, input and output losses and isolations of the output ports are investigated for each power divider/combiner structures. Comparison of the measurement and simulation results are examined in detail. Güç bölücü ve birleştirici yapılar, mikrodalga uygulamalarında yüksek düzeyde güçlere ulaşabilmek için gerekli ve kritik pasif elementlerdir. Son yıllardaki RF/Mikrodalga sistemlerindeki gelişmeler, yüksek kaliteli, yüksek performanslı güç ayırıcı/birleştiricilere olan talebin artmasına neden olmuştur. Bu tez çalışmasında, dört yönlü ofset güç bölücü/birleştirici, iki yönlü halka güç bölücü/birleştirici, üç yönlü faz kaydırmalı Wilkinson güç bölücü/birleştirici ve dört yönlü birleşmiş güç bölücü, minyatürleştirme teknikleri kullanılarak, 8-12 GHz frekans bandında dizayn edilmiştir. Analitik çözümleri ve tasarım prosedürleri Advance Design System (ADS) yazılımı kullanılarak incelenmiştir. Bu bölücü ve birleştirici yapılar Bilkent Üniversitesi Nanoteknoloji Araştırma Merkez’inin (NANOTAM) Silisyum Karbür (SiC) tabanlı Galyum Nitrür (GaN) prosesi kullanılarak üretilmiştir. Fabrikasyon detayları adım adım gösterilmiştir. Tasarlanan bölücü ve birleştirici yapılar, NANOTAM laboratuvarlarında ölçülmüştür. Her güç bölücü/birleştirici yapı için ekleme kayıplarının, giriş ve çıkış geri dönüş kayıplarının ve çıkış portlarının yalıtımının ölçüm ve simülasyon sonuçları incelenmiştir. Ölçüm ve simülasyon sonuçlarının karşılaştırılması detaylı olarak sunulmuştur.

This paper presents a highly compact frequency-selective surface (FSS) that has the potential to switch between the X-band (8 GHz–12 GHz) and C-band (4 GHz–8 GHz) for RF shielding applications. The proposed FSS is composed of a square conducting loop with inward-extended arms loaded with curved extensions. The symmetric geometry allows the RF shield to perform equally for transverse electric (TE), transverse magnetic (TM), and 45∘ polarizations. The unit cell has a dimension of 0.176 λ0 and has excellent angular stability up to 60∘. The resonance mechanism was investigated using equivalent circuit models of the shield. The design of the unit element allowed incorporation of PIN diodes between adjacent elements for switching to a lower C-band spectrum at 6.6 GHz. The biasing network is on the bottom layer of the substrate to avoid effects on the shielding performance. A PIN diode configuration for the switching operation was also proposed. In simulations, the PIN diode model was incorporated to observe the switchable operation. Two prototypes were fabricated, and the switchable operation was demonstrated by etching copper strips on one fabricated prototype between adjacent unit cells (in lieu of PIN diodes) as a proof of the design prototypes. Comparisons among the results confirmed that the design offers high angular stability and excellent performance in both bands.

In this paper, to the best of our knowledge, this is the first time that the generation and reception of online software-reconfigurable real-time 4/16/64-quadrature amplitude modulation (QAM)-encoded and forward error correction (FEC)-enabled orthogonal frequency-division multiplexing (OFDM) signals over X-band fiber-over-radio-based upstream links has been demonstrated. A Reed-Solomon code, i.e., RS (288, 256), with symbol interleaving/deinterleaving is applied to enhance bit-error-rate (BER) performance. The experimental results show that the 4/16/64-QAM-OFDM signals with net data rates of 1.6/3.2/4.8-Gb/s after 1.5-m wireless and 2.26-km SMF-28 transmission with BERs below the hard-decision FEC threshold of 3.8e-3 can be successfully achieved without using FEC. With the help of symbol-interleaved RS code, a post-FEC BER below 1e-8 can be observed when the pre-FEC BER is around 1e-3.

A compact design of ultra-wideband (UWB) antenna with dual band-notched characteristics based on split-ring resonators (SRR) are investigated in this paper. The wider impedance bandwidth (from 2.73 to 11.34 GHz) is obtained by using two symmetrical slits in the radiating patch and another slit in the partial ground plane. The dual band-notch rejection at WLAN and X-band downlink satellite communication system are obtained by inserting a modified U-strip on the radiating patch at 5.5 GHz and embedding a pair of rectangular SRRs on both sides of the microstrip feed line at 7.5 GHz, respectively. The proposed antenna is simulated and tested using CST MWS high frequency simulator and exhibits the advantages of compact size, simple design and each notched frequency band can be controlled independently by using the SRR geometrical parameters. Therefore, the parametric study is carried out to understand the mutual coupling between the dual band-notched elements. To validate simulation results of our design, a prototype is fabricated and good agreement is achieved between measurement and simulation. Furthermore, a radiation patterns, satisfactory gain, current distribution and VSWR result at the notched frequencies make the proposed antenna a suitable candidate for practical UWB applications.

This paper deals with the retrieval of snow depth (SD) and snow water equivalent (SWE) using dual-polarization (HH-VV) synthetic aperture radar (SAR) data. The effect of different snowpack conditions on the SD and SWE inversion accuracy was demonstrated by using three TerraSAR-X acquisitions. The algorithm is based on the relationship between the SD, the co-polar phase difference (CPD), and particle anisotropy. The Dhundi observatory in the Indian Himalaya was selected as a validation test site where a field campaign was conducted for ground truth measurements in January 2016. Using the field measured values of the snow parameters, the particle anisotropy has been optimized and provided as an input to the SD retrieval algorithm. A spatially variable snow density ( ρ s ) was used for the estimation of the SWE, and a temporal resolution of 90 m was achieved in the inversion process. When the retrieval accuracy was tested for different snowpack conditions, it was found that the proposed algorithm shows good accuracy for recrystallized dry snowpack without distinct layering and low wetness (w). The statistical indices, namely, the root mean square error (RMSE), the mean absolute difference (MAD), and percentage error (PE), were used for the accuracy assessment. The algorithm was able to retrieve SD with an average MAE and RMSE of 6.83 cm and 7.88 cm, respectively. The average MAE and RMSE values for SWE were 17.32 mm and 21.41 mm, respectively. The best case PE in the SD and the SWE retrieval were 8.22 cm and 18.85 mm, respectively.

This paper proposed quadruple notched frequency bands ultra-wideband (UWB) antenna. The antenna is a semicircular-shaped monopole type of a compact size 36x24 mm, covering frequency range of 3.02-14 GHz. Four rejected narrow bands including WiMAX (3.3-3.7GHz), ARN (4.2-4.5 GHz), WLAN (5.15-5.825GHz), X-Band (7.25-7.75) have been achieved using inserting slots techniques in the patch, feed line, and ground plane. The slots dimensions have been optimized for the required reject bands. The antenna design and analysis have been investigated by simulation study using CST-EM software package. The antenna characteristics including impedance bandwidth, surface current, gain, radiation efficiency, radiation pattern have been discussed.

With traditional radio frequency (RF) bands becoming congested and the Department of Defense (DoD) expanding its efforts in the field of small satellites, the need for an on-orbit software-defined radio (SDR) has emerged. SDRs are a compact, off-the-shelf, low-cost, low-risk options for small satellite communication and can provide the flexibility of on-orbit configurability. This study includes the research toward the development of an on-orbit SDR CubeSat payload that can transmit on X-band spectrum (8–12 GHz). This band of interest can provide higher data rates and more bandwidth. Work in CubeSat transmitters and receivers supports development of national capabilities in space of benefit to warfighters. The payload designed, built, and tested for this research is called Com-Cube. Com-Cube utilizes hardware components and software considered for incorporation into a future CubeSat payload. Com-Cube was tested on a low altitude balloon (LAB) flight and demonstrated the transmission of images taken in-flight to a ground station via an amateur radio C-band frequency (5.75 GHz). This work directly supports a transmitter and receiver needed for future telemetry, tracking, and command (TT&C) and payload applications in the field of small satellites. This type of payload provides a test platform for further NPS research in the Mobile CubeSat Command and Control (MC3) ground station network operations and broadcast and receive experiments at frequencies of interest. http://archive.org/details/softwaredefinedr1094561218 Outstanding Thesis Lieutenant, United States Navy Approved for public release; distribution is unlimited.

The interferometric synthetic aperture radar (InSAR) data set, used for the generation of the global TanDEM-X (TDX) DEM, includes multiple acquisitions with different parameters. It enables a big opportunity for scientific geo-applications, such as for land characterization, classification, and monitoring. One valuable information that can be derived from interferometric SAR data for land classification describes the presence/absence of vegetation. At X-band, volume scattering produces decorrelation, even in the presence of short vegetation. As TerraSAR-X and TanDEM-X satellites are still acquiring data, the exploitation of the signatures for specific or detailed vegetation is possible. In August 2016 a ground field campaign was conducted in the Bavaria region, while dedicated TanDEM-X data takes over the same area were commanded by using different acquisition geometries and configurations. The aim of this paper is to characterize the interferometric signatures of agricultural areas from single-pass bistatic TDX acquisitions at 12 meters posting, using the on ground typification for classification purposes.