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Implementation of edge-filter detection for interrogating optical interferometric ultrasonic sensors is often hindered by the lack of cost-effective laser sources with agile wavelength tunability and good noise performance. The detected signal can also be affected by optical power variations and locking-point drift, negatively affecting the sensor accuracy. Here, we report the use of laser single-sideband generation with a dual-parallel Mach–Zehnder interferometer (DP-MZI) for laser wavelength tuning and locking in edge-filter detection of fiber-optic ultrasonic sensors. We also demonstrate real-time in situ calibration of the sensor response to ultrasound-induced wavelength shift tuning. The DP-MZI is employed to generate a known wavelength modulation of the laser, whose response is used to gauge the sensor response to the ultrasound-induced wavelength shifts in real time and in situ. Experiments were performed on a fiber-optic ultrasonic sensor based on a high-finesse Fabry–Perot interferometer formed by two fiber Bragg gratings. The results demonstrated the effectiveness of the laser locking against laser wavelength drift and temperature variations and the effectiveness of the calibration method against optical power variations and locking-point drift. These techniques can enhance the operational robustness and increase the measurement accuracy of optical ultrasonic sensors. [ABSTRACT FROM AUTHOR]

We present a sensor that utilizes a modified single-frequency split beam metasurface reflector to measure the refractive index of materials ranging from one to three. Samples are placed into a cavity between a PCB-etched dielectric and a reflecting ground plane. It is illuminated using a 10.525 GHz free-space transmit horn with reflecting angles measured by sweeping a receiving horn around the setup. Predetermined changes in measured angles determined through simulations will coincide with the material's index. The sensor is designed using the Fourier transform method of array synthesis and verified with FEM simulations. The device is fabricated using PCB milling and 3D printing. The quality of the sensor is verified by characterizing 3D printed dielectric samples of various infill percentages and thicknesses. Without changing the metasurface design, the sensing performance is extended to accommodate larger sample thicknesses by including a modified 3D printed fish-eye lens mounted in front of the beam splitter; this helps to exaggerate changes in reflected angles for those samples. All the methods presented are in agreement and verified with single-frequency index measurements using Snell's law. This device may offer a viable alternative to traditional index characterization methods, which often require large sample sizes for single-frequency measurements or expensive equipment for multi-frequency parameter extraction. [ABSTRACT FROM AUTHOR]

Implementation of edge-filter detection for interrogating optical interferometric ultrasonic sensors is often hindered by the lack of cost-effective laser sources with agile wavelength tunability and good noise performance. The detected signal can also be affected by optical power variations and locking-point drift, negatively affecting the sensor accuracy. Here, we report the use of laser single-sideband generation with a dual-parallel Mach–Zehnder interferometer (DP-MZI) for laser wavelength tuning and locking in edge-filter detection of fiber-optic ultrasonic sensors. We also demonstrate real-time in situ calibration of the sensor response to ultrasound-induced wavelength shift tuning. The DP-MZI is employed to generate a known wavelength modulation of the laser, whose response is used to gauge the sensor response to the ultrasound-induced wavelength shifts in real time and in situ. Experiments were performed on a fiber-optic ultrasonic sensor based on a high-finesse Fabry–Perot interferometer formed by two fiber Bragg gratings. The results demonstrated the effectiveness of the laser locking against laser wavelength drift and temperature variations and the effectiveness of the calibration method against optical power variations and locking-point drift. These techniques can enhance the operational robustness and increase the measurement accuracy of optical ultrasonic sensors.

We present a sensor that utilizes a modified single-frequency split beam metasurface reflector to measure the refractive index of materials ranging from one to three. Samples are placed into a cavity between a PCB-etched dielectric and a reflecting ground plane. It is illuminated using a 10.525 GHz free-space transmit horn with reflecting angles measured by sweeping a receiving horn around the setup. Predetermined changes in measured angles determined through simulations will coincide with the material’s index. The sensor is designed using the Fourier transform method of array synthesis and verified with FEM simulations. The device is fabricated using PCB milling and 3D printing. The quality of the sensor is verified by characterizing 3D printed dielectric samples of various infill percentages and thicknesses. Without changing the metasurface design, the sensing performance is extended to accommodate larger sample thicknesses by including a modified 3D printed fish-eye lens mounted in front of the beam splitter; this helps to exaggerate changes in reflected angles for those samples. All the methods presented are in agreement and verified with single-frequency index measurements using Snell’s law. This device may offer a viable alternative to traditional index characterization methods, which often require large sample sizes for single-frequency measurements or expensive equipment for multi-frequency parameter extraction.

In this manuscript, we experimentally demonstrate a parity-time-symmetric optoelectronic oscillator (OEO) with polarization multiplexed channels. We obtained a microwave single-mode oscillation at 9.5 GHz with phase noise values of âˆ'116.2 and âˆ'122.3 dBc Hzâˆ'1 at 10 kHz offset frequencies, and side mode suppression values below âˆ'68 and âˆ'75 dBc Hzâˆ'1, by utilizing a 1 km long and 5 km long single mode fiber delay lines, respectively. Our experimental results suggest that parity-time-symmetric OEOs with polarization multiplexed channels are simple and cost-efficient alternatives to their more complex counterparts. [ABSTRACT FROM AUTHOR]

This letter proposes a frequency domain closed‐form analytical solution for large signal condition in radio‐over‐fibre systems that employ external intensity‐modulation and direct‐detection. The received radio frequency signal power was used to evaluate the chromatic dispersion effect in optical links. To the best of knowledge, a comparison between large signal with small signal solutions has been theoretically presented here for the first time. For analogue optical amplitude modulations, the double sideband showed a 30 dB difference between the approaches, a 9 dB for the single sideband, and 17 dB for the suppressed carrier. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an all optical wavelength conversion of Nyquist differential phase 16 quadrature amplitude modulation based on microwave photonics signal processing for flex‐grid optical networks. By analyzing the mechanism of the microwave photonics and adjusting the parameters of the components, multi‐wavelength tunable laser with smooth and adjustable optical intensity can be obtained. Then, the multi‐channel photonic signals with the minimal guard space of 5 GHz can be obtained, which provide more than 20 flex‐grids for optical transmission with transparent rate and format. The optical power of converted wavelengths, optical signal‐to‐noise ratio, error vector magnitude, and bit error rate (BER) are studied under the condition of different flex‐grids, the frequencies of which are from 15 GHz to 36 GHz. The channel frequency spacing and amplitude of the converted wavelength can be dynamically adjusted via parameter configuration. Flex‐grid spacing strategies and channel selecting strategies are given. The BER performance of all converted channels can fall below the forward error correction threshold of 3.8 × 10−3 by optimizing the optical power of the receiver end. The results show the tradeoff between the BER and the detected optical power of the receiver end. These research findings could provide solutions for spectrum allocation and routing selection when wavelength conversion is needed in optical links. [ABSTRACT FROM AUTHOR]

The first successful pump/probe microwave-optical double resonance experiment using a laser ablation/reaction scheme for molecular beam production has been performed. Pure rotational transitions at frequencies up to 52 GHz have been recorded for the transient refractory compounds YF, YO, and SrOH at a resolution of <30 kHz [full-width at half- maximum (FWHM)]. The observed three lowest pure rotational transition frequencies of YF (X 1Σ+) were analyzed to produce an improved set of rotational constants, B=8683.6156(11) MHz and D=0.007 521(74) MHz. The three lowest pure rotational transitions of SrOH (X 2Σ+) were analyzed to give the spectroscopic parameters (in MHz), B=7470.8180(4), D=0.006 25(3), γ=72.706(1), γD=-0.0021(2); bF (H)=1.713(2) and c (H)=1.673(5). The proton magnetic hyperfine interactions were interpreted in terms of a molecular orbital description for the X 2Σ+ state. [ABSTRACT FROM AUTHOR]

Studies the bolometric optical response in microwave meander lines. Resonant frequency as a function of optical pulse energy; Details on the experiment; Results and discussion.

Highlights • Spectral reflectivities of magnetite and hematite in a wide frequency range (from extreme ultraviolet to microwave). • The analysis of microwave optical constants of iron oxides by means of the Kramers–Kronig method. • Approximation dependences of optical constants of magnetite and hematite in the microwave range. Abstract The paper presents an analysis of microwave optical constants of iron oxides (magnetite and hematite) by means of the Kramers–Kronig method. Spectral reflectivities of magnetite and hematite in a wide frequency range (from extreme ultraviolet to microwave) were derived based on multiple experimental data found in the literature. The obtained dependencies were used to calculate optical constants of the minerals at 12–145 GHz and compare the results with other reported theoretical and laboratory studies. [ABSTRACT FROM AUTHOR]

A novel approach to generating background-free microwave pulse based on both bright and dark temporal gate and a single photodetector is proposed and demonstrated. Incoherent wavelength-to-time conversion (WTTC) using only bright or dark gate renders the generation of positive or negative pulse separately. By using both gates simultaneously, background-free pulse is realized with enhanced amplitude compared with that obtained using only bright or dark gate. A dual-output intensity modulator functions as both the bright and dark gate. Narrow drive pulse is provided by the combination of two polarity-opposite electrical pulses with a relative time-delay, which releases the requirement of expensive narrow-pulse generator. Incoherent WTTC using dark gate is demonstrated experimentally. The system resolution remains the same as that using bright gate. Furthermore, UWB pulse with 10-dB bandwidth of 3.8-GHz is generated based on 1-Gb/s gate driven by 1-Gb/s data sequence. Several other background-free pulses are generated to verify the tunability of central frequency, pulse envelope, duty cycle, and repetition rate. In addition, the effect of gate width on WTTC is explored experimentally. With narrower gate width, higher system solution and maximum achievable frequency can be implemented. 10.4-GHz and 14.5-GHz background-free pulses are generated when using 1-Gb/s and 10-Gb/s gate respectively. [ABSTRACT FROM AUTHOR]

The usefulness of a stochastic approach in determining time scales in tunneling processes (mainly, but not only, in the microwave range) is reconsidered and compared with a different approach to these kinds of processes, based on Feynman’s transition elements. This latter method is found to be particularly suitable for interpreting situations in the near field, as results from some experimental cases considered here. [ABSTRACT FROM AUTHOR]

We present a reconfigurable microwave photonic filter (MPF) based on polarization modulation and a tunable optical bandpass filter (TOBPF). The MPF is possible to switch between a low-pass and bandpass responses by simply setting a polarizer. Furthermore, the cutoff frequency of the low-pass MPF, the central frequency, and the bandwidth of the bandpass MPF are widely tunable by adjusting the TOBPF. The proposed MPF is theoretically analyzed and experimentally verified. [ABSTRACT FROM AUTHOR]

Uncertainty in surface soil roughness strongly degrades the performance of surface soil moisture (SSM) and vegetation water content (VWC) retrieval from passive microwave observations. This paper proposes an algorithm to objectively determine the surface soil roughness parameter of the radiative transfer model by fusing microwave and optical satellite observations. It is then demonstrated in a semiarid in situ observation site. The roughness correction of this new algorithm positively impacted the performance of SSM (root-mean-square error reduced from 0.088 to 0.070) and VWC retrieval from the Advanced Microwave Scanning Radiometer 2 and Moderate Resolution Imaging Spectroradiometer. Since this surface soil roughness correction may be transferrable to other microwave satellite retrieval algorithms such as those for the Soil Moisture and Ocean Salinity and Soil Moisture Active Passive satellites, this new algorithm can contribute to many microwave earth surface observation satellite missions. [ABSTRACT FROM PUBLISHER]

We demonstrated a timing fluctuation suppression in outdoor laser-based atmospheric radio-frequency transfer over a 110 m one-way free-space link using an electronic phase compensation technique. Timing fluctuations and Allan Deviation are both measured to characterize the instability of transferred frequency incurred during the transfer process. With transferring a 1 GHz microwave signal over a timing fluctuation suppressed transmission link, the total root-mean-square (rms) timing fluctuation was measured to be 920 femtoseconds in 5000 s, with fractional frequency instability on the order of 1 × 1 0 − 12 at 1 s, and order of 2 × 1 0 − 16 at 1000 s. This atmospheric frequency transfer scheme with the timing fluctuation suppression technique can be used to fast build an atomic clock-based frequency free-space transmission link since its stability is superior to a commercial Cs and Rb clock. [ABSTRACT FROM AUTHOR]

Electro-optic (EO) polymers offer a very attractive possibility of realizing low-cost microwave photonic components with a wide bandwidth and a low driving voltage, thanks to a low dispersion from microwave to optical frequency of polymeric materials on the one hand, and the progress in the synthesis of high hyperpolarizability chromophores on the other hand. This paper studies the influence of titanium dioxide (TiO) nanoparticle loading on the microwave and optical properties of EO polymers. Thus, poly(methyl methacrylate) (PMMA) and disperse red 1 (DR1) are used as host polymer and guest EO chromophore, respectively. With 1-3% TiO nanoparticle homogeneously incorporated in the polymer, the dielectric constant varies from 2.73 to 3.40 over the 400 MHz-10 GHz range, and the refractive index increases from 1.483 to 1.488 at the wavelength of 1539.6 nm. It is shown that fine tuning of dielectric constant and refractive index could allow improvement of the microwave photonic component bandwidth. For example, with an EO interaction length L = 2 cm (typical length of EO modulators), the ultimate modulator bandwidth could be raised to 258 GHz by loading PMMA-DR1 EO polymer with 1% wt of TiO nanoparticles. It is also found that loading polymer with nanoparticles could improve the EO response of poled polymers, represented by the intensity of the second-harmonic-generation (SHG) signal. The latter presents more than a threefold increase by loading PMMA-DR1 EO polymer with 2% wt TiO nanoparticles. [ABSTRACT FROM AUTHOR]

ABSTRACT We report on a terahertz (THz) time-domain system to characterize photoconductive THz emitters and detectors, that is designed for highest reproducibility. This system is excellently suited for studying the performance of THz sources and detectors in a systematic manner, either by varying the substrate materials or the geometrical parameters of metallic antenna contacts building a photoconductive switch. After confirming the reproducibility and stability of the system with errors of only 1.9% (over 3 h) and 2.6% (over 9 days), we use the system to compare the performance of five low temperature grown (LT) GaAs wafers with growth temperatures between 200°C and 300°C. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:468-472, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, the periodic structure-based absorber operating at dual-band or more for applying to new electromagnetic wave measurement facility that does not contain a conventional pyramidal absorber is presented. To achieve the objective, the absorber structure takes the format of two-layer periodic surfaces. Based on the logical design principles, the parametric study results to obtain the desired performance and the final experimental result are addressed. The measured result shows a broadband reflectivity characteristic from 0.60 to 3.27 GHz on the basis of below −10 dB. As a result, the absorber shows the performance supporting CDMA, WCDMA, and WLAN bands in the electromagnetic wave measurement facility. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:478-481, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper describes properties of a new 20-bit chipless RFID tag of the size 52 × 50 mm2, which exhibits an improved magnitude and robustness of the radar cross section. The tag is based on a novel slots-in-plate array approach, which is complementary to a typical tag consisting of an array of single resonators. In order to eliminate the detuning effect of the missing or shortening slots representing '0' bit information on the resonances of neighbouring slots signifying '1' bit information, the modification of the inter-element arrangement was proposed. Both ways of '0' bit information coding were studied and compared. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:488-492, 2017 [ABSTRACT FROM AUTHOR]

This study examined the performance of a developed taper-tube concentrator for 94-GHz millimeter-wave beam reception during wireless power transfer. The received energy is converted into kinetic energy of a working gas in the tube to drive an engine or thruster. The concentrator, which is assumed to have mirror reflection of millimeter waves in it, is designed to be shorter than conventional tapered waveguides of millimeter waves. A dimensionless design law of a concentrator is proposed based on geometric optics theory. Because the applicability of geometric optics theory is unclear, the ratio of its bore diameter to its wavelength was set as small compared to those in other possible applications. Then, the discrepancy between the designed and measured power reception was examined. Results show that the maximum discrepancy was as low as 7 % for the bore-to-wavelength ratio of 20 at the narrow end of the concentrator. [ABSTRACT FROM AUTHOR]

We present spectroscopic measurements looking for the coherent coupling between molecular magnetic centers and microwave photons. The aim is to find the optimal conditions and the best molecular features to achieve the quantum strong coupling regime, for which coherent dynamics of hybrid photon-spin states take place. To this end, we used a high critical temperature YBCO superconducting planar resonator working at 7.7 GHz and at low temperatures to investigate three molecular mononuclear coordination compounds, namely (PPh4)2[Cu(mnt)2] (where mnt2− = maleonitriledithiolate), [ErPc2]−TBA+ (where pc2− is the phtalocyaninato and TBA+ is the tetra-n-butylammonium cation) and Dy(trensal) (where H3trensal = 2,2′,2′′-tris(salicylideneimino)triethylamine). Although the strong coupling regime was not achieved in these preliminary experiments, the results provided several hints on how to design molecular magnetic centers to be integrated into hybrid quantum circuits. [ABSTRACT FROM AUTHOR]

Cadmium substituted cobalt ferrites with formula Cd x Co 1− x Fe 2 O 4 ( x =0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye – Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15–19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd 2+ concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner’s model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system Cd x Co 1− x Fe 2 O 4 the impedance analysis were performed. [ABSTRACT FROM AUTHOR]

ABSTRACT The details of a more general form of the sub-structure characteristic mode concept are presented than previously done. The orthogonality properties of these modes are stated, proven, and discussed. Sub-structure characteristic modes are interpreted in terms of loading. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:481-486, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, we present a composite feed dual circularly polarized (CP) aperture-coupled microstrip antenna at L-band with improved characteristics. Two dedicated feeds have been conceived; one feed produces left hand CP, while the other generates right hand CP (RHCP). A prototype has been designed, fabricated and experimentally measured. 7.8% axial ratio bandwidth at each of the ports and in-band interport isolation over 18 dB without using power divider has been demonstrated. As much as 3.5 dBi gain at each port have been achieved experimentally. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:283-289, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, it is demonstrated a fiber ring resonator connected to an interrogation system usually implemented on a cavity ring-down technique. A long-period grating (LPG) was inserted in the resonant cavity, being operated as a curvature sensor. The experimental results demonstrate that using this setup, different sensitivities can be achieved in terms of analyzing decay time over the radius of the curvature and over curvature. The LPG sensor presented higher sensitivity with larger radius of curvature, namely 6.91 μs/m. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:267-270, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT Filtering patch crossovers with single- and dual-band operation are implemented for the first time. For the single-band filtering crossover, it is composed of four inset fed input/output ports and a circular patch. The dual-band property can be easily realized with high flexibility by loading four open stubs. To verify the design concept, three filtering crossovers are implemented. The measured results agree well with the simulation, exhibiting crossover characteristics throughout the specific passband and high rejection level within the suppression band. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:301-304, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT A compact multiple-input-multiple-output (MIMO) inverted-F antenna system for time division-long term evolution (TD-LTE) E band, 3.50-GHz worldwide interoperability for microwave access, and 5.20-GHz wireless local area network with enhanced isolation is proposed. The proposed MIMO antenna system consists of two identical inverted-F antenna elements operating in the 2.32-2.37/3.40-3.62/5.12-5.29 GHz frequency bands at the reflection coefficient level below −10 dB. The edge-to-edge distance between the two antenna elements is only 0.1 mm. The high isolation is achieved by mirror symmetrical orientation of the two antenna elements on the different side of the FR4 substrate and replacing part of the substrate with pieces of copper to connect the ground planes together to form a common ground. The size of the proposed antenna system has the dimensions of 53.00 mm [ABSTRACT FROM AUTHOR]

ABSTRACT This article proposes dual-mode balanced bandpass filters (BPFs) with high common-mode (CM) rejection performance using the substrate integrated waveguide (SIW) cavity and its size-reduced form, a folded SIW cavity structure. The latter's size (folded cavity) is nearly 50% of the former. The passband response of the proposed dual-mode balanced BPFs are formed by the (folded) SIW cavities' two degenerated modes, TE102 and TE201 modes. The advantages of the proposed BPFs are higher Q value and higher power handling capability as compared with those of the microstrip counterparts. The dual-mode resonance of the SIW cavity also offers the benefit of size reduction and, sometimes, higher Q value than that of its fundamental mode. The hybrid microstrip/slot is used to design the filters' feed structure for enhancing the CM rejection. This high CM rejection is caused by the noncoupling nature of the slot, which bisected by an imposed perfect magnetic wall. The measured in-band CM rejection levels are around 40 dB with the differential-mode insertion losses around 2.5 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:402-406, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT Novel axe-shaped circular microstrip quad band cost effective antenna with simple structure is developed. This design consists of circular patch with elliptical and circular slots loading provide an axe shape patch along with stubs offer quad bands. The proposed antenna provides resonance at the frequencies of 2.8, 4, 5.4, and 6.2 GHz which covers the applications of WLAN/WI-FI and WIMAX. The measured results of reflection coefficient and VSWR are presented. The proposed design provides minimum rejection ratio of 23 dB and maximum rejection ratio of 15 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:400-402, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this work is presented an optical method using the Mach-Zehnder Interferometer for diagnose a pure helium gas subjected to a stationary point-plane corona dischargeat atmospheric pressure, and visualize the spatial map of refraction index, density and temperature.The Mach-Zehnder interferometer that we have applied here is assumed to be cylindrically symmetric and the distance between electrodes equals 6 mm.By studying the interferograms obtained in the experiment, it is possible to determine the distribution of the refraction index and extract the density and temperature through the Gladstone-Dale relation and the ideal gas law respectively. The obtained results are in close agreement with values available in the literature.The obtained results show that the rate variation of the density is varying from 20 to 40% in all the space. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:393-398, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT In this article, it is proposed a model for multilevel polarization modulation tailored to Local Area Networks (LAN's), which exploits optical fiber intrinsic properties to obtain, with the same bandwidth, a higher single-channel throughput with a reduced receiver complexity. This is achieved through a 'fluid' constellation of confined bands. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:389-393, 2016 [ABSTRACT FROM AUTHOR]

A microwave photonic link (MPL) with spurious-free dynamic range (SFDR) improvement utilizing the nonlinearity of a distributed feedback (DFB) laser is proposed and demonstrated. First, the relationship between the bias current and nonlinearity of a semiconductor DFB laser is experimentally studied. On this basis, the proposed linear optimization of MPL is realized by the combination of the external intensity Mach--Zehnder modulator (MZM) modulation MPL and the direct modulation MPL with the nonlinear operation of the DFB laser. In the external modulation MPL, the MZM is biased at the linear point to achieve the radio frequency (RF) signal transmission. In the direct modulation MPL, the third-order intermodulation (IMD3) components are generated for enhancing the SFDR of the external modulation MPL. When the center frequency of the input RF signal is 5 GHz and the two-tone signal interval is 10 kHz, the experimental results show that IMD3 of the system is effectively suppressed by 29.3 dB and the SFDR is increased by 7.7 dB. [ABSTRACT FROM AUTHOR]

We propose a microwave photonics system for radio frequency self-interference cancellation using optical techniques. With a simple structure, this system employs two low-cost directly modulated lasers and a balanced photodetector to subtract the strong self-interference signal from a corrupted received signal. For commonly used wireless applications, 40-dB cancellation within 900-MHz band and 33-dB cancellation within 2.4-GHz band are experimentally obtained, both over 400-MHz bandwidth. Moreover, for ultra-wideband cancellation, this system achieves more than 27-dB cancellation over 6-GHz bandwidth. The experimental results show good recovery of the weak signal of interest buried by strong self-interference after the cancellation. [ABSTRACT FROM AUTHOR]

ABSTRACT Experimental observations from different fiber lasers or different states within a fiber laser confirm that the fiber dispersion parameter is wavelength-dependent, which suggests that the fiber dispersion measurement based on Kelly sidebands should base on either positive or negative sideband order only rather than sideband orders across zero. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:242-245, 2016 [ABSTRACT FROM AUTHOR]

Ag/Zr 0.9 Ni 0.1 O y nanocomposites with different atomic ratios of Ag to Zr 0.9 Ni 0.1 O y (Ag/Zr 0.9 Ni 0.1 O y = x where “ x ” is 0%, 5%, and 20%) were synthesized through co-precipitation technique. The structure and morphology properties of the Zr 0.9 Ni 0.1 O y nanocomposites were evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The permittivity and permeability behaviors of samples were investigated. Results showed that when 20 wt.% Ag was added (named S20), the permittivity and the permeability of the S20 became negative. These results imply the realization of double negative properties in S20 as a desired candidate for the double negative materials (DNMs). [ABSTRACT FROM AUTHOR]

Soil moisture plays a vital role in land surface energy and the water cycle. Microwave remote sensing is widely used because of the physically based relationship between the land surface emission observed and soil moisture. However, the application of retrieved soil moisture data is restricted by its coarse spatial resolution. To overcome this weakness, downscaling methods should be developed to disaggregate coarse resolution microwave soil moisture data to fine resolution. The traditional method is the microwave-optical/IR synergistic approach, in which land surface temperature, vegetation index, and surface albedo are key parameters. Five purely empirical methods based on the triangle feature are selected in this study. To evaluate their performance on downscaling microwave soil moisture, these methods are applied to the Zoige Plateau in China using the Advanced Microwave Scanning Radiometer on the Earth Observing System (AMSR-E) Land Parameter Retrieval Model (LPRM) soil moisture product and Moderate Resolution Imaging Spectroradiometer (MODIS) optical/IR products. The coarse-resolution AMSR-E LPRM soil moisture data are disaggregated into the high resolution of the MODIS product, and the surface soil moisture measurements of the Maqu soil moisture observation network located in the plateau are used to validate the downscaling results. Results show that (1) the relationship models used in these methods can generally capture the variation in soil moisture, withR2around 0.6, but have a relatively high uncertainty under conditions of high soil moisture; (2) the methods can provide high-resolution soil moisture distribution, but the downscaled soil moisture presents a low level correlation with field measurements at different spatial and temporal scales. This comparative study provides insight into the performance of popular purely empirical downscaling methods on enhancing the spatial resolution of soil moisture on the Tibetan Plateau. Although synergistic methods can improve the spatial resolution of AMSR-E soil moisture data, additional studies are needed to exclude the uncertainty from AMSR-E soil moisture estimation, the low sensitivity of the relationship model under high soil moisture, and the spatial representativeness difference between coarse pixels and point measurement. [ABSTRACT FROM PUBLISHER]

A Quantum Hamiltonian formalism is proposed for the description of an electro-optical modulator based on the linear Pockels effect. Optical photons interact with photons of a microwave mode in a combined high- Q cavity made of a LiNbO crystal. The microwave photons occupy a coherent state, while optical photons have an arbitrary density matrix. The spectrum of a photodetected modulated signal is analyzed as a function of the frequency of a tunable optical filter. Numerical estimates are obtained, and quantum effects in the spectrum, such as the red shift of the central frequency and sidebands, the possibility of modulation of the optical signal by the microwave field vacuum, and the asymmetry of the intensity of the spectral sidebands, are discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, we use a nanoparticle cluster composed of silicon nanodisks in both symmetric and antisymmetric regimes to design an artificial efficient nanoswitch. Using appeared Fano dip for the antisymmetric nanocluster in the visible spectrum, we controlled the quality of Fano resonance (FR) by changing the polarization direction of the incident light source. In this method, we showed that appearing and disappearing of FR for different polarizations can be used to design an ON/OFF switch based on the behavior of Fano dip in a silicon-based cluster. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1242-1246, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A dual-band substrate integrated coaxial line (SICL) 3-dB branch-line coupler and its compact realization are proposed in this letter. The SICL coupler with the compact structure shows a comparable performance and great size reduction compared with the conventional structure. The simulated and measured results match very well. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1246-1249, 2015 [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) technology has attracted great interest because it can provide a promising solution of future radar and short-range broadband wireless communications. The generation of millimeter-wave UWB signals using photonic approaches can reduce the high cost of the millimeter-wave electrical circuits. Moreover, it is well compatible with fiber transmission, which can effectively extend its signal coverage. In this paper, a novel approach to the photonic generation of millimeter-wave UWB signals with dual-band operation consideration is proposed. The proposed scheme can simultaneously generate millimeter-wave UWB signals in both 24 GHz and 60 GHz millimeter band, and can efficiently exploit the spectrum limit allowed by the FCC mask by using the linear combination pulse design concept. A model describing the proposed system is developed and the generation of 24/60 GHz millimeter-wave UWB signals is demonstrated via computer simulations. [ABSTRACT FROM AUTHOR]

We report strong coupling between an ensemble of N impurity (PI) centers in diamond and microwave photons using a unique double-post reentrant cavity. The cavity is designed so that the magnetic component of the cavity field is spatially separated from the electric component and focused into the small volume in which the diamond sample is mounted. The novelty of the structure simultaneously allows the high magnetic filling factor (38.4%) and low frequencies necessary to interact, at low magnetic field, with transitions in diamond such as those in negatively charged nitrogen-vacancy and P1 centers. Coupling strength (or normal-mode splitting) of 51.42 MHz was achieved with PI centers at 6.18 GHz and 220 mT in a centimeter-scale cavity, with a corresponding cooperativity factor of 4.7. This technique offers an alternative way, with some significant advantages, to couple 3D cavities to transitions in diamond and achieve the strong coupling necessary for applications to quantum information processing. [ABSTRACT FROM AUTHOR]

We report a technique that can noninvasively add multiple DC wires into a 3D superconducting microwave cavity for electronic devices that require DC electrical terminals. We studied the influence of our DC lines on the cavity performance systematically. We found that the quality factor of the cavity is reduced if any of the components of the electrical wires cross the cavity equipotential planes. Using this technique, we were able to incorporate a quantum dot (QD) device into a 3D cavity. We then controlled and measured the QD transport signal using the DC lines. We have also studied the heating effects of the QD by the microwave photons in the cavity. [ABSTRACT FROM AUTHOR]

ABSTRACT This note describes a new material made of carboned foam glass. Shaped as a pyramid, its leads to great absorption levels. The computation of reflection coefficient is completely derived. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:18-22, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT This article presents the results of a compact modified triangular CPW-fed antenna that exhibits multioctave performance. This modification significantly improves the antenna's impedance bandwidth by 198% over an ultra-wideband (UWB) frequency range from 3.06 to 35 GHz. The return-loss (S11) performance over this frequency range is designed to be better than −10 dB. These characteristics make the proposed antenna an excellent candidate for numerous UWB applications and next generation communication systems. The key physical parameters affecting the antenna's frequency characteristics have also been investigated to determine optimum antenna performance. The antenna's measured return loss and E-plane and H-plane radiation patterns show a very good correlation with the requirements of UWB applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:69-72, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A compact printed monopole antenna on FR4 substrate is proposed for bluetooth and ultrawideband applications. The antenna patch is obtained by joining two distinct semiellipses through their major axes. Results are experimentally demonstrated over significant wideband operation. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:28-31, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT CPW monopoles with textile artificial magnetic conductor (AMC) sheet-like waveguide were designed with the goal to improve transmission between antennas. The AMC substrate is made of Fleece fabric while SHIELDIT fabric is used for the conducting parts. A small AMC sheet as well as an AMC waveguide jacket were fabricated. Experiments were carried out in free space and near to human body settings, with different orientations being considered. The S21 transmission between two monopoles is improved up to maximum 29 dB with the presence of AMC surface. For both free space and on-body placements, significant transmission enhancement has been observed for all the tested positions. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:197-200, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT This article investigates the slotted bow-tie dual-polarization antenna with achieving the wide band. The proposed antenna consists of upper antenna and lower antenna in one PCB substrate. This antenna achieves a −10 dB return loss within the operating band of 1.6-2.3 GHz, which has a 700 MHz bandwidth. Isolation between antenna 1 and antenna 2 is about −30 dB within the operating frequency band. Antenna 1 and 2's gains are above 8 dBi in the entire frequency bandwidth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:22-26, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A compact novel coplanar waveguide-fed antenna with square spiral-patch for multiband applications is presented. The antenna consists of a square-spiral patch with two L-shape strips. With subjoin square spiral the number of frequency resonance is increasing. Also by introducing two L-shaped strips in the inside of square spiral, much wider impedance bandwidth can be produced, especially at the higher bands. The operating frequencies of the proposed antenna are 2.62/3.40/4.42/5.92/8.32 GHz. Some key parameters affecting the antenna performance have been analyzed using computer simulations. To validate the simulation results, the prototypes of the proposed antenna are fabricated on an inexpensive FR-4 substrate and tested. Good radiation characteristics of the proposed antenna have been obtained. The simulated and measured results are in good agreement. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:111-115, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A novel compact microstrip-fed tri-band monopole antenna for WLAN and WiMAX applications is presented in this letter. Hybrid Strips including an L-shaped strip and a meandered strip are used to generate three resonances in the monopole antenna. Due to the use of a meandered line structure, the antenna size is reduced to 38 × 20 × 1 mm3 only. Compared to the existing designs, the proposed antenna has a size 30, 55, and 70% of the designs in [1-3], respectively. To investigate the performance of antenna versus key antenna design parameters, results of a parametric study are presented. Simulated surface current is also shown. To validate the concept, one antenna prototype is implemented and tested, and the measured results show that the antenna can achieve good performance for WLAN 2.4/5.8 GHz and WiMAX 3.5 GHz applications. The antenna has a compact size and is easy for fabrication, hence useful for practical applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:94-99, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT A semianalytical finite element method (FEM) is proposed for analyzing propagation of electromagnetic waves in stratified media. Conventional finite elements are used to discretize the cross-section of a layered structure, and a Riccati equation-based integration scheme is used to handle the longitudinal direction with a very high precision. This semianalytical FEM is easy to implement. Numerical examples demonstrate that the proposed method has high efficiency and accuracy. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:15-18, 2015 [ABSTRACT FROM AUTHOR]