Passive Microwave Devices Research Articles

Flexible branch‐line coupler using rubber conductive Zoflex for conformal application

AbstractThis letter presents the design of a flexible branch‐line coupler (BLC) using a rubber conductor (Zoflex) as the conductive element and polydimethylsiloxane (PDMS) as a substrate. The BLC is meant to operate at 6 GHz operating frequency. The use of PDMS material as a substrate for the BLC design adds a special characteristic of the PDMS on this passive microwave device. The PDMS has some unique properties such as transparency, durability, and lightweight. Moreover, its high electrical resistivity of 2.9 × 1014 Ω m and moderate dielectric constant of 2.7 make the PDMS a good substrate material for flexible devices. This desirable property gives the proposed device full range of flexibility and a great advantage in terms of durability without degrading the performance of the BLC. From the results obtained for bending and non‐bending conditions, it can be seen that within the frequency range of operation, both the return loss and the isolation are kept below the theoretical value of −10 dB. The slight difference observed in the simulated and measured FBWs is due the fabrication tolerances.

Adaptive suppression of passive intermodulation in digital satellite transceivers

For the performance issues of satellite transceivers suffering passive intermodulation interference, a novel and effective digital suppression algorithm is presented in this paper. In contrast to analog approaches, digital passive intermodulation (PIM) suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems. A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect. The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function. A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing. In consideration of the time-varying characteristics of passive intermodulation, this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources. Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference, and achieve a high signal-to-interference ratio gain.

Determination of the Trace-Gas Concentrations at the Altitudes of the Lower and Middle Mesosphere from the Time Series of Ozone Concentration

We present a statistical (Bayesian) approach to retrieving the concentrations of the most important mesospheric trace gases at altitudes of 50–75 km using the photochemical model based on the time series of ozone concentration, which are measured during the daylight hours in one day with the help of the ground-based passive microwave devices. Using the model noisy time series of ozone concentration with allowance for the realistic accuracy of its measurements in the mesosphere, which is ensured by the available ozonometers, the accuracy of retrieving the non-measurable mesospheric characteristics is studied as a function of the altitude and the time-series length.

Frequency‐periodic microwave passive circuits and their digital matching

Frequency-periodic microwave passive devices can be analysed in such a way that the coefficients of their digital counterparts can be extracted. In this study, this analysis procedure is exploited with the aim of providing a new theoretical framework to model these circuits, which could hopefully make their synthesis easier in the future. Interesting results observed from the application of this method to three examples of passive devices are as follows: (i) the appearance of zero-pole cancelations (ZPCs), (ii) the explanation of the required redundancy in certain microwave structures, and (iii) some difficulties observed in the synthesis of some frequency-periodic circuits, given a predefined digital design as a single starting point. The ZPCs appearing for the first example corresponding to a stepped-impedance-stub-based lowpass filter explain its inherent structure redundancy. Next, the analysis performed for a frequency-periodic wide-band matching network as second example also reveals the ZPC phenomenon, which justifies the existence of difficulties in its theoretical synthesis starting from a prefixed digital design. Finally, the third example consists in the application of the procedure to the well-known 3-dB branch-line hybrid, for which no ZPCs arise.

Твердотельные СВЧ-модули для радиотехнической аппаратуры и систем миллиметрового диапазона длин волн

The paper presents scientific, technological and production potential of Research Institute «Orion» in the field of creation of wide range of high performance active and passive solid-state microwave devices, modules and components as well as multifunctional devices on their basis. These products taken as a whole form a component base for promising equipment and systems working in the frequency range from 1.0 to 200 GHz.

Novel neural network modeling method and applications

Neural networks play an important role for designing the parametric model of electromagnetic structures. The current neural network methods are unfit for a circuit model with many input variables because it is costly to extract a large number of the training data and test data to complete the highly nonlinear mapping approximation. This article proposes a new neural network modeling method-the multidimensional neural network model, which can be used to solve the issue of multivariable radiofrequency and microwave passive device modeling. The entire multidimensional neural network modeling problem is simplified into a set of neural network submodels through decomposition method. Then the submodels are combined into an equivalent model, and the final entire model is produced through the neural-network mapping model developed with the submodels and equivalent model. A microstrip hairpin filter model is developed using the proposed method. The simulation results show the correctness and the effectivity of the proposed method. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:769-779, 2015.

Main Source of Microwave Loss in Transition‐Metal‐Doped Ba(Zn1/3Ta2/3)O3 and Ba(Zn1/3Nb2/3)O3 at Cryogenic Temperatures

Microwave resonator measurements were performed on high‐performance microwave ceramics Ba(Zn1/3Ta2/3)O3 (BZT) and Ba(Zn1/3Nb2/3)O3 (BZN) containing additives commonly used by commercial manufacturers (i.e., Co, Mn, and Ni). We find that the loss tangent, even in ambient magnetic fields, is dominated by electron paramagnetic resonance (EPR) absorption by exchange‐coupled 3d electrons in transition metal clusters at cryogenic temperatures. The large orbital angular momentum in Co2+ and Ni2+ ions of L = 3 causes strong anisotropic‐broadened dipolar interactions that extend EPR losses to zero applied field. This effect is greatest in BZN with Co concentrations greater than 0.5 mol%, dominating the losses at liquid nitrogen temperatures (77 K) and below. In samples containing Mn2+ ions with L = 0, the dipolar interactions and associated EPR losses in ambient fields are smaller. We show the magnetic‐field‐dependent changes in the EPR losses (i.e., tan δ) and magnetic reactive response (i.e., μr) are from the same mechanism, as they follow the Kramers–Kronig relation. Finally, we note that these materials can make ultra‐high Q passive microwave devices with externally controlled transfer functions, as the quality factor (Q) of the composition Ba(Co1/15Zn4/15Nb2/3)O3 at 77 K can be tuned from 1 100 to 12 000 at 10 GHz by applying practical magnetic fields.

Microstructure and microwave properties of inkjet printed barium strontium titanate thick-films for tunable microwave devices

Abstract Barium strontium titanate (BST) is a promising material for passive tunable microwave devices such as phase shifters, tunable filters or tunable matching networks. This publication covers the preparation of BST thick-films for microwave applications through inkjet printing. A Ba 0.6 Sr 0.4 TiO 3 ink was prepared, printed on alumina substrates and sintered at temperatures between 1100 °C and 1200 °C. The microstructure of the thick-films reveals the evolution of grain growth and porosity with increasing sintering temperature. Furthermore, a reaction with the substrate was observed for T ≥ 1175 °C. A maximum tunability of 36% was observed at temperatures right below the onset of the substrate reactions. This process conditions were used for the preparation of a loaded line phase shifter, which successfully shows the capability of the inkjet printing process for future microwave device fabrication.

A novel RF fingerprinting approach for hardware integrated security

A novel approach for RF fingerprinting using a simple microwave passive device is proposed. This device is a multi-port cavity resonator filled with a dielectric material mixed with randomly-distributed micro- or nano-particles. Such structure generates a typical Physical Unclonable Function (PUF) that can be perfectly used for storing and protecting secure information. This mixture guarantees a spatial random distortion on the electromagnetic fields and consequently a unique fingerprint. The extraction of these fingerprints is based on the scattered near-fields which are represented by the S-parameters. Preliminary measurement results show a high degree of reliability and reproducibility of the fingerprints over the UWB frequency range.

Epitaxial growth of 100-μm thick M-type hexaferrite crystals on wide bandgap semiconductor GaN/Al2O3 substrates

Thick barium hexaferrite BaFe12O19 (BaM) films having thicknesses of ∼100 μm were epitaxially grown on GaN/Al2O3 substrates from a molten-salt solution by vaporizing the solvent. X-ray diffraction measurement verified the growth of BaM (001) textured growth of thick films. Saturation magnetization, 4πMs, was measured for as-grown films to be 4.6 ± 0.2 kG and ferromagnetic resonance measurements revealed a microwave linewidth of ∼100 Oe at X-band. Scanning electron microscopy indicated clear hexagonal crystals distributed on the semiconductor substrate. These results demonstrate feasibility of growing M-type hexaferrite crystal films on wide bandgap semiconductor substrates by using a simple powder melting method. It also presents a potential pathway for the integration of ferrite microwave passive devices with active semiconductor circuit elements creating system-on-a-wafer architectures.

Preparation of Integrated Passive Microwave Devices Through Inkjet Printing

Barium strontium titanate (BST) is a promising material for passive tunable microwave devices such as phase shifters or tunable matching networks. This publication covers the preparation of BST thick-films for microwave applications through inkjet printing. Two barium strontium titanate (BST) inks were prepared, printed on alumina substrates and sintered at different temperatures. The first ink was prepared with pure BST and sintered between 1100°C and 1200°C. The second ink was prepared with a BST–ZnO–B2O3 composition and was suitable to reduce the sintering temperature down to 800°C. The microstructure of the thick-films reveals the evolution of grain growth with increasing sintering temperature in the thick-films. Furthermore, a reaction with the substrate was observed for both inks at high sintering temperatures. The microwave characterization of the thick-films shows that for the permittivity and the tunability of the films, the effect of grain growth and reaction with the substrate compete against each other. Hence, the optimal microwave properties were achieved at a transition temperature, where first additional phases could already be observed. Even though, the properties are poorer for lower sintering temperatures, the investigations show that the preparation of silver- or gold-based metal–insulator–metal (MIM) structures through inkjet printing is possible with this composition. This allows various new design concepts for partly or fully inkjet printed passive microwave devices. Furthermore, it gives the opportunity for a future integration of passive tunable microwave devices in a low temperature co-fired ceramic (LTCC) fabrication process.

Inkjet catalyst printing and electroless copper deposition for low-cost patterned microwave passive devices on paper

A scalable, low-cost process for fabricating copper-based microwave components on flexible, paper-based substrates is demonstrated. An inkjet printer is used to deposit a catalyst-bearing solution (tailored for such printing) in a desired pattern on commercially-available, recyclable, non-toxic (Teslin®) paper. The catalystbearing paper is then immersed in an aqueous copper-bearing solution to allow for electroless deposition of a compact and conformal layer of copper in the inkjet-derived pattern. Meander monopole antennas comprised of such electroless-deposited copper patterns on paper exhibited comparable performance as for antennas synthesized via inkjet printing of a commercially-available silver nanoparticle ink. However, the solution-based patterning and electroless copper deposition process avoids nozzle-clogging problems and costs associated with noble metal particle-based inks. This process yields compact conductive copper layers without appreciable oxidation and without the need for an elevated temperature, post-deposition thermal treatment commonly required for noble metal particle-based ink processes. This low-cost copper patterning process is readily scalable on virtually any substrate and may be used to generate a variety of copper-based microwave devices on flexible, paper-based substrates.

Inkjet‐printed antennas, sensors and circuits on paper substrate

Inkjet-printing is a very promising technology for the development of microwave circuits and components. Inkjet-printing technology of conductive silver nanoparticles on an organic flexible paper substrate is introduced in this study. The paper substrate is characterised using the T-resonator method. A variety of microwave passive and active devices, as well as complete circuits inkjet-printed on paper substrates are introduced. This work includes inkjet-printed artificial magnetic conductor structures, a substrate integrated waveguide, solar-powered beacon oscillator for wireless power transfer and localisation, energy harvesting circuits and nanocarbon-based gas-sensing materials such as carbon nanotubes and graphene. This study presents an overview of recent advances of inkjet-printed electronics on paper substrate.

Impedance spectroscopy of Li2CO3 doped (Ba,Sr)TiO3 ceramic

(BaxSr1−x)TiO3-based ceramic has been considered as one of the most important electronic materials widely employed in microwave passive device applications. Many researches have been performed to lower the high sintering temperature, by adding various dopants such as B2O3, La2O3, etc. In our previous study, by adding Li2CO3 to (Ba0.5,Sr0.5)TiO3 ceramics, the sintering temperature of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics decreased from 1350 to 900 °C.This study observed the crystalline structure and electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics. In scanning the crystalline structure of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, no pyro phase was observed by X-ray diffraction analysis. To investigate the electrical properties of Li2CO3 doped (Ba0.5,Sr0.5)TiO3 ceramics, real and imaginary parts of the impedances were analyzed. Complex impedance data were measured from 100 Hz to 1 MHz at various temperature ranges.

Ultra-low power electrically reconfigurable magnetoelectric microwave devices

We present an electrical tunable spiral inductor design and simulation results. By integrating (011) oriented single crystal ferroelectric substrate [Pb(Mg1/3Nb2/3)O3](1−x)-[PbTiO3]x (PMN-PT, x ≈ 0.32) with tunable and switchable remanent strain property, the tunability of such magnetoelectric microwave inductor can retain after releasing the electric actuation, i.e., electrically reconfigurable. A series of reconfigurable passive magnetoelectric microwave devices based on this concept are proposed and discussed. Those electrically reconfigurable magnetoelectric microwave devices have the advantage of low power consumption and fast and wide tunability, which can be potentially used for many applications.

Multiband microwave passive devices using generalized negative-refractive-index transmission lines (Invited paper)

This article presents an overview of the generalized negative-refractive-index transmission-line (G-NRI-TL) and summarizes the design equations that determine the frequencies of each of its four passbands. Specific multiband devices to which G-NRI-TLs have been applied are discussed: both a dual-band coupled-line coupler operating at 2.7 and 4.7 GHz and a printed single-ended all-pass cell with two pairs of right- and left-handed bands are explained. The details of how each may be fabricated in a fully-printed layout are provided and simulated and measured results are given. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22:459–468, 2012. © 2012 Wiley Periodicals, Inc.

Quasi Static Modeling of Weak Nonlinearity in Superconducting Transmission Lines with Sub-Wavelength Non-Uniformity

Superconducting passive microwave devices unlike routine normal conductor ones, due to dependence of superfluid density (ns) to current distribution, have a nonlinear behavior called Nonlinear Meissner Effect (NME). In this paper, a nonlinear distributed circuit model for HTS transmission lines with sub-wavelength longitudinal non-uniformity in the case of weak nonlinearity is proposed. This model is based on the quasi-TEM approximation of sub-wavelength non-uniform transmission lines (SW-NUTLs) that proposes closed form formulas for effective characteristic impedance and complex propagation constant of SW-NUTLs. Any NUTLs can be modeled with the mentioned method through dividing it into adequately small subsections to fulfill sub-wavelength condition. Regarding these propagation parameters relations, some effective equations for RLGC parameters are inferred. Because of dependence of the penetration depth and the real part of conductivity on ns, the proposed effective resistance and inductance depend on current distribution that in case of weak nonlinearity, follow a square-law form. As such the nonlinear microwave effects such as Intermodulation distortion (IMD) and harmonic generation can be calculated with harmonic balance (HB) Analysis. This semi-analytical approach shows great accuracy in different test cases.

Demonstration of the high RF power production feasibility in the CLIC power extraction and transfer structure [PETS

A fundamental element of the CLIC concept is two-beam acceleration, where RF power is extracted from a high current, low energy drive beam in order to accelerate the low current main beam to high energy. The CLIC Power Extraction and Transfer Structure (PETS) is a passive microwave device in which bunches of the drive beam interact with the constant impedance of the periodically loaded waveguide and excite preferentially the synchronous mode. The RF power produced is collected downstream of the structure by means of the RF power extractor; it is delivered to the main linac using the waveguide network connecting the PETS to the main CLIC accelerating structures. The PETS should produce 135 MW at 240 ns RF pulses at a very low breakdown rate: BDR < 10{sup -7}/pulse/m. Over 2010, a thorough high RF power testing program was conducted in order to investigate the ultimate performance and the limiting factors for the PETS operation. The testing program is described and the results are presented.

Determination of Moisture Content in Oil Palm Fruits Using a Five-Port Reflectometer

This paper presents the development of a PC-based microwave five-port reflectometer for the determination of moisture content in oil palm fruits. The reflectometer was designed to measure both the magnitude and phase of the reflection coefficient of any passive microwave device. The stand-alone reflectometer consists of a PC, a microwave source, diode detectors and an analog to digital converter. All the measurement and data acquisition were done using Agilent VEE graphical programming software. The relectometer can be used with any reflection based microwave sensor. In this work, the application of the reflectometer as a useful instrument to determine the moisture content in oil palm fruits using monopole and coaxial sensors was demonstrated. Calibration equations between reflection coefficients and moisture content have been established for both sensors. The equation based on phase measurement of monopole sensor was found to be accurate within 5% in predicting moisture content in the fruits when compared to the conventional oven drying method.

Structure, magnetic, and microwave properties of thick Ba-hexaferrite films epitaxially grown on GaN/Al2O3 substrates

Thick barium hexaferrite [BaO⋅(Fe2O3)6] films, having the magnetoplumbite structure (i.e., Ba M), were epitaxially grown on c-axis oriented GaN/Al2O3 substrates by pulsed laser deposition followed by liquid phase epitaxy. X-ray diffraction showed (0,0,2n) crystallographic alignment with pole figure analyses confirming epitaxial growth. High resolution transmission electron microscopy images revealed magnetoplumbite unit cells stacked with limited interfacial mixing. Saturation magnetization, 4πMs, was measured for as-grown films to be 4.1±0.3 kG with a perpendicular magnetic anisotropy field of 16±0.3 kOe. Ferromagnetic resonance linewidth, the peak-to-peak power absorption derivative at 53 GHz, was 86 Oe. These properties will prove enabling for the integration of low loss Ba M ferrite microwave passive devices with active semiconductor circuit elements in systems-on-a-wafer architecture.