Applications In Microwave Electronics Research Articles

The dielectric and impedance spectroscopy of poly vinyl alcohol doped with carbon (PVA-C)

The poly vinyl alcohol (PVA) thin-film composites with a uniform dispersion of carbon nanoparticles were prepared by the solution casting technique. Spectroscopic techniques were used to evaluate the distribution of carbon in the composite film. The surface morphology studies were done using Scanning Electron Microscope. The variation in crystalline property, the formation of groups and variation in direct band gap in PVA and PVA-C composite were studied by X-Ray Diffraction method, Fourier Transform Infrared Radiation - Attenuated Total Reflection and by Ultraviolet–Visible Spectroscopic study. The IV characteristics study shows the non-Ohmic behaviour and the variation in conductivity. The impedance, dielectric properties and electric modulus were evaluated. The impedance value for PVA is 700Ω, and for 0.4%C + PVA is 4.6 MΩ. The tangent loss of PVA is found to be decreased by 67% ± 2 for 0.4%C + PVA. The PVA-C is flexible, and lightweight with enhanced dielectric performance and finds its application in microwave electronics.

Exploring a quantum-information-relevant magnonic material: Ultralow damping at low temperature in the organic ferrimagnet V[TCNE

Quantum information science and engineering require novel low-loss magnetic materials for magnon-based quantum-coherent operations. The search for low-loss magnetic materials, traditionally driven by applications in microwave electronics near room temperature, has gained additional constraints from the need to operate at cryogenic temperatures for many applications in quantum information science and technology. Whereas yttrium iron garnet (YIG) has been the material of choice for decades, the emergence of molecule-based materials with robust magnetism and ultra-low damping has opened new avenues for exploration. Specifically, thin films of vanadium tetracyanoethylene (V[TCNE]x) can be patterned into the multiple, connected structures needed for hybrid quantum elements and have shown room-temperature Gilbert damping (α = 4 × 10−5) that rivals the intrinsic (bulk) damping otherwise seen only in highly polished YIG spheres (far more challenging to integrate into arrays). Here, the authors present a comprehensive and systematic study of the low-temperature magnetization dynamics for V[TCNE]x thin films, with implications for their application in quantum systems. These studies reveal a temperature-driven, strain-dependent magnetic anisotropy that compensates the thin-film shape anisotropy and the recovery of a magnetic resonance linewidth at 5 K that is comparable to room-temperature values (roughly 2 G at 9.4 GHz). The authors can account for these variations of the V[TCNE]x linewidth within the context of scattering from very dilute paramagnetic impurities and anticipate additional linewidth narrowing as the temperature is further reduced.

Impedance tuning with photoconductors to 40 GHz

Light is widely used to control a variety of microwave devices, including switches, antennas, and detectors. Here, the authors present a photoconductive device integrated into a coplanar waveguide to tune complex impedances at microwave frequencies with applied light. The authors measured the current–voltage characteristics of the device as a function of the applied light intensity and fit the behavior to a known metal-semiconductor-metal junction model with two Schottky barriers. The authors also measured the frequency-dependent scattering parameters and extracted the device impedances in a Pi-network model. The devices showed three orders of magnitude impedance tunability from 100 MHz to 40 GHz, and the authors developed a circuit model to fit the frequency-dependent impedances. This simple device has applications in microwave electronics, microwave metrology, and multi-state calibrations.

High-Q microwave dielectrics in wolframite magnesium zirconium tantalate ceramics

A new high-Q microwave dielectric ceramic MgZrTa2O8 was investigated for the first time. Single monoclinic-structured MgZrTa2O8 was obtained by the conventional solid-state route and sintered at 1390–1470°C for 5h. The variation trend of dielectric constant was in accordance with that of relative density and ionic polarizability. The Q×f value increased by increasing the packing fraction. The temperature coefficient of τf correlated with the variation of bond valence of Ta-site. In summary, the MgZrTa2O8 ceramic sintered at 1450°C showed excellent microwave dielectric properties of εr~29.5, Q×f~140,900GHz, τf~−44.3ppm/°C. These make MgZrTa2O8 material a very promising candidates for the application in microwave electronics.

Butyl rubber–Ba0.7Sr0.3TiO3 composites for flexible microwave electronic applications

Butyl rubber–Ba0.7Sr0.3TiO3 composites (BR–BST) were prepared by sigma mixing followed by hot pressing. The stress–strain studies show the good flexibility of the composite. The dielectric properties of the composites were investigated at both radio and microwave frequencies. The relative permittivity (εr) and loss tangent (tanδ) improved with filler loading at both the frequencies. The relative permittivity and loss tangent of the BR–BST composites at a maximum filler loading of 0.39 volume fraction (vf) are 13.1 and 0.009 respectively at 5GHz measured by Split Post Dielectric Resonator (SPDR). The effective relative permittivity of the BR–BST composites is compared with theoretical models. The variation of εr with temperature was also investigated in the range 22–80°C at 1MHz. The microwave dielectric properties of the composites are also studied after repeated bending. The coefficient of thermal expansion (CTE) of the butyl rubber–BST composites decreased with the addition of the BST ceramic.

Employing magnonic crystals to dictate the characteristics of auto-oscillatory spin-wave systems

Spin-wave active rings–positive-feedback systems incorporating spin-wave waveguides–provide important insight into fundamental magnetics, enable experimental investigations into nonlinear wave phenomena, and potentially find application in microwave electronics. Such rings break into spontaneous, monomode oscillation at a certain threshold value of feedback gain. In general, the wavenumber of this initially excited, threshold mode is impossible to predict precisely. Here we discuss how, by exploiting resonant spin-wave reflections from a magnonic crystal, an active ring system having a threshold mode with a well-defined and precisely predictable wavenumber may be realized. Our work suggests that study and development of active ring systems incorporating magnonic crystals may deliver useful insight into spin-wave transmission in structured magnetic films as well as devices with technological applicability.

Effects of Calcination Temperature on the Phase Formation and Microstructure of Barium Zinc Tantalate

Nowadays, high dielectric materials are important materials in microwave electronic applications due to its properties that can provide high frequency range of an antenna. Barium Zinc Tantalate (BZT) is a complex perovskite structure that can produce high quality factor, Q. In this research, the effect of calcinations temperatures on phase formation, density and morphology of BZT powders were investigated. Based on the DTA result, the range of calcinations temperatures to be investigated were between 750°C to 1250°C. Results show that the maximum density of BZT occurred at 1150°C with 99.74% theoretical density. Samples calcined at below 1100°C still containing their raw materials such as BaCO3, ZnO and Ta2O5. The pure phase of BZT was formed at 1150°C when calcined for 1 hour. The lattice distortion of BZT increased when the calcinations temperature increased between 1000°C to 1150°C. The calcined powders show almost spherical morphology and agglomerated. The particle sizes of BZT increased from 0.716μm to 0.258μm when the temperature increased from 750°C to 1200°C.

Influence of Electron Irradiation on the Properties of Ferroelectric BaxSr1-xTiO3 Films

The radiating treatment is an effective way of influence on a structure and electrical properties of condensed matter that essentially expands the possibilities of material research. Ferroelectric compounds are interesting objects for a study of irradiation effects both from physical point of view, and for practical applications in microwave electronics. Till to present, basically bulk ferroelectrics were studied under radiation [1], nevertheless highly oriented thin ferroelectric films are most informative and practically important object for the investigations. The purpose of this work is associated with investigation of high energy electron radiation influence on defect structure and electrical characteristics of Ba0.6Sr0.4TiO3 (BSTO) ferroelectric films.

Characteristics of a new camel-gate field effect transistor (CAMFET) with a composite channel structure

A new camel-gate field effect transistor (CAMFET) with a composite channel structure has been fabricated and demonstrated. Due to the n+-InGaP/p+-InGaP/GaAs camel gate and InGaAs/GaAs composite channel structures employed, good device performance is observed. Experimentally, at room temperature, a gate-drain breakdown voltage over 15 V, maximum transconductance gm,max of 111.5 mS mm−1, voltage gain AV of 93.4, unity current gain cut-off frequency fT of 16.2 GHz and maximum oscillation frequency unity fmax of 24.2 GHz are obtained simultaneously for a 1 × 100 µm2 device. The studied device also shows good properties in a higher temperature regime. Moreover, the studied device exhibits relatively negligible temperature-dependent characteristics over the operating temperature range from 300 to 420 K. Therefore, the studied device provides promise for high-temperature and high-performance microwave electronic applications.

Investigation of a new InGaP-InGaAs pseudomorphic double doped-channel heterostructure field-effect transistor (PDDCHFET)

An interesting new InGaP-InGaAs pseudomorphic double doped-channel heterostructure field-effect transistor (PDDCHFET) is fabricated and demonstrated. Due to the employed InGaAs double doped channel (DDC) structure and Schottky behaviors of InGaP insulator, good dc properties including higher turn-on voltage, lower leakage current, better linearity, and good RF performances are obtained. In addition, the experimental results are fitted well with theoretical simulation data based on a two-dimensional (2-D) simulator. Moreover, the studied device exhibits relatively negligible temperature-dependent characteristics over a wide operating temperature region (300<T<450 K). Therefore, the studied PDDCHFET provides the promise for high-temperature and high-performance microwave electronic applications.

Low-temperature growth of mirror-like superconducting thin films on sapphire

The recently developed process of plasma-assisted laser deposition was used to grow high-quality, mirror-like superconducting Y-Ba-Cu-O films on sapphire, both with and without a buffer layer. At a deposition temperature of 400° C, the as-deposited Y-Ba-Cu-O film on MgO/Al 2O 3 and Ag/Al 2O 3 and Al 2O 3 substrates was superconducting at ≈ 75 K. The orientation of the film and the critical current both depended on the presence of the buffer layer. After suitable patterning, such films should have important applications in microwave electronics.

The propagation of elastic surface waves guided by ridges

The ‘finite element’ technique is used to investigate numerically the guiding of elastic surface waves by ridges with a view to application in microwave electronics and in seismology. The technique is applied first to other problems with a cylindrical geometry such as the propagation of waves along bars and plates where existing theoretical and experimental results are available for comparison. Finally ridged structures are considered. Dispersion curves and displacement functions are obtained for the lowest mode which is the only one which may, under suitable circumstances, propagate unattenuated. Our results indicate that only the lowest antisymmetric mode is properly trapped by the ridge and that this occurs in a certain frequency range.