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To develop a high voltage read margin ΔVrd, deep reset engineering and defect engineering are proposed. To realize the defect engineering, the amount of oxygen vacancy of the resistor was controlled by optimizing the material of the reservoir (RSV) and switching oxide. We investigated the barrier height modulation, which was formed by the Ru bottom electrode (BE) having a high work function, to demonstrate the concept of deep reset engineering by reducing the set current (Iset) of the HfO2 resistor (1R) to the turn-on current (Ith) of the selector device (1S). Further, we identified the causes of the negative set fail through the chemical analysis of the HfO2/BE TiN interface to improve the reset switching fail. Unstable TiON and TiOx chemical species, which present in the interface of HfO2/BE TiN, take oxygen from the resistor HfO2 and create the parasitic defect (or filament), which was injected from BE TiN. To improve the negative set fail of RRAM, we proposed the O3 surface treatment of BE TiN at a high temperature (∼320 °C) and the BE Ru with a superior oxidation resistance. By using deep reset engineering, we successfully increased the ΔVrd of 1S1R by more than 0.5 V. We also demonstrated that Ru BE and the O3 surface treatment of BE TiN improved both the reset window and the negative set.

In this paper, the magnetic field design of a superconducting fixed-frequency isochronous cyclotron with four spiral sectors for proton therapy was performed. The basic parameters of the isochronous cyclotron magnet and its characteristics are described. Several magnet sectors were designed during the iteration process to achieve an isochronous magnetic field. The result of 3-D magnetic field simulation using OPERA-3D and the analysis of the designed magnetic field are presented. A special geometry was introduced into the sector gap to achieve the isochronous condition, and the spiral angle was adjusted to control the vertical focusing parameter. The equilibrium orbits were checked for the designed magnetic field, and a single particle tracking simulation was performed with CYCLONE code.

In this letter, a compact low noise amplifier (LNA) with high stable gain using distributed elements with composite right/left-handed (CRLH) metamaterial is presented. In the proposed LNA, the CRLH is composed of distributed elements with a compact meander-line structure. The transistor (TR) in the proposed LNA is selected as a HEMT device due to its low noise and high stable gain performances. In this structure, the CRLH is adopted as the input and output matching networks in the LNA. The operating frequency of the proposed LNA is 2.0 GHz, the minimum noise figure is 0.71 dB, and the maximum stable gain is 10.4 dB. Also, the total size of the proposed LNA is 10.8 × 13.6 mm2. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1715–1720, 2016

Magnetic nanofluids (MNFs) are an interesting energy harvesting source. Oil- or water-based MNFs include a certain percentage of magnetized nanoparticles (MNPs) and have unique features that vary with the strength of the external electromagnetic field [1]-[3]. For MNFs, it was proved that the electric power generation could be achieved by using waste heat energy [4]. In this work, the flow energy harvesting was experimentally and numerically investigated in a millimeter-sized channel by using an externally applied permanent magnet to control the magnetizing direction of the MNPs. When the MNF flows through a cross-sectional area of the coil loop, the electric current can be obtained by following the Faraday's law because the MNPs act as permanent magnets [5]. When the MNFs are used for flow energy harvesting, the main issue is the in-phase mode alignment of the MNPs magnetization with the coil loop. Although without the in-phase mode the electric power cannot be generated, as the net magnetization of the MNF is zero, most of the previous research works have not considered it. Thus, to implement this mode, we proposed an externally applied magnetic field generated by a cylindrically shaped permanent magnet. Short and closed Teflon tubing with a 3 mm inner diameter, containing the MNF, was located inside long silicon tubing and moved along the positive and negative direction by a pump. Then, the generated voltages were measured and exhibited similar results to those obtained analytically.

Proliferation characteristics of CHO-K1 cells were investigated under a variety of medium perfusion rate conditions in a microfluidic perfusion cell culture platform. Five microcavities of $$800\,\upmu \hbox {m}~(w)\,\times \,800\,\upmu \hbox {m}~(l)\,\times \,400\,\upmu \hbox {m}~(h)$$ were adopted in order to minimize or isolate the shear effects on cell surfaces. Microchannels of $$800\,\upmu \hbox {m}~(w)\,\times \,3.5\,\hbox {mm}~(l)\,\times \,100\,\upmu \hbox {m}~(h)$$ serially connecting these microcavities created flow contractions and expansions repeatedly, resulting in two different diffusion and convection timescales through the platform. Average shear stresses on the bottom of microcavity were both numerically and analytically estimated, and medium flow was operated at rates where shear stress is below $$\sim$$ 2 mPa. Proliferation rates of CHO-K1 cells were investigated based both on population groups derived from the number of initially seeded cells and on the microcavity locations. Population groups showed minimal influences on proliferation rates, while proliferation rates increased clearly with medium perfusion rates. Strong effects of microcavity locations were observed on proliferation at $$\hbox {Pe}\,\ge \,45$$ . Such effects were analyzed by investigating the relationships of reaction, diffusion, and convection timescales associated with perfusion conditions. The ratio of diffusion timescale and convection timescale was suggested as a guideline to estimate the upper limit of perfusion rate in microfluidic perfusion cell culture platform.

In this article, a flexible coplanar waveguide (CPW) series resonator combined with short- and open-end CPW series stubs on polyimide film is presented. To obtain equivalent circuit of each stub, a new phase compensation method is applied. The accuracy of equivalent circuit with this method is confirmed by comparison between electromagnetic simulation and circuit simulation results. Based on equivalent inductance and capacitance for short-end series stub and open-end series stub, respectively, a CPW series resonator is designed without optimization at 5.8 GHz. The measured frequency responses of the series stubs and resonator are in good agreement with the predicted simulation results. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:193–196, 2015

In this article, a new compact narrow bandwidth elliptic function band-pass filter (BPF) using combination of stepped impedance resonator shaped hair-pin, interdigital capacitor, and meander-line resonator with μ-near zero (MNZ) metamaterial is studied. The MNZ metamaterial resonator has band-stop resonance and positive phase response (+90°) due to its zero-value permeability. The experimental result of the resonator shows the loaded quality factor (QL) of 244 at the resonant frequency of 9.95 GHz. Also, the insertion and return losses of the proposed BPF are 1.55 and 15.4 dB with bandwidth of 2.5% and center frequency of 9.95 GHz, respectively. The size of the proposed BPF is 3.56 × 4.47 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2245–2248, 2014

In this article, a stable low noise and high gain dual-band active bandpass filter (BPF) with GaAs-metal-semiconductor field effect transistor (MESFET) using composite right-/left-handed (CRLH) metamaterial is presented. The CRLH approach in a microstrip structure is applied to develop a dual-band BPF using an amplifier circuit with two arbitrary frequency bands. The two center frequencies of the filter are then chosen as ω1 = 1.23 GHz and ω2 = 1.63 GHz, where the phase slope characteristics of the response are chosen as −90° and −270° at frequencies of ω1 and ω2, respectively. The experimental results show gain values of 7.82 and 7.03 dB and the return losses of −15.1 and −10.1 dB with bandwidth of 55 (4.4%) and 105 MHz (6.4%) at the center frequencies of 1.22 and 1.61 GHz, respectively. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1985–1988, 2014

In this article, a size-reduced dual band-pass transmission line (TL) with a composite right/left handed (CRLH) shunt-stub is presented. It uses a T-shaped quarter-wavelength TL, which shows dual band-pass characteristics, when the electrical length is +nλ/4 or −nλ/4, where n is odd integer. These wavelengths can be achieved at arbitrary frequencies by the CRLH-TL with the property of a nonlinear β versus ω. The phase delay at the two operating frequencies can be adjusted by designing the series TL part, identical to the case of a conventional TL. The performance of this TL is demonstrated in both simulations and measurements, which show good agreement, exhibiting insertion losses of 0.32 and 0.98 dB at the two operating frequencies, respectively. Also, the phase response difference was determined to be 180° at these frequencies. The size of the proposed TL is 16 × 19 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2150–2153, 2014

In this article, a new compact narrow bandwidth slow- wave band-pass filter (BPF) using combination of stepped impedance resonator-shaped hair-pin, interdigital capacitor, and meander-line reso- nator with m-near zero (MNZ) metamaterial is suggested. The MNZ metamaterial resonator has band-stop resonance and positive phase response (190� ) due to zero-value permeability. The experimental result of the resonator shows the loaded quality factor (QL) of 249 at the reso- nant frequency of 10.0 GHz. Also, the insertion and return losses of the proposed BPF are 1.49 and 15.0 dB with the bandwidth of 4% and cen- ter frequency of 10 GHz, respectively. The size of the proposed BPF is

In this article, a new high-loaded quality factor (QL) resonator using combination of a stepped impedance resonator-shaped hair-pin resonator, interdigital capacitor, and a meander-line with μ-near-zero (MNZ) metamaterial is suggested. An interdigital capacitor is applied to the resonator to obtain high-QL performance and MNZ characteristic for size reduction. The resonator is designed to operate at 10 GHz, and the experimental result shows the Q-factor value of 167. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1781–1785, 2014

In this article, a new narrow band pass filter (BPF) with second harmonic suppression using triple-split ring resonator (T-SRR) in mu-negative metamaterial on Teflon substrate is presented. Then by replacing the series quarter-wavelength transmission lines with the equivalent T-shaped line, a compact-BPF with second harmonic suppression can be obtained. This filter shows an insertion loss of 0.47 dB and return loss of 21.8 dB with bandwidth of 10% at the center frequency of 10 GHz. Also, the experimental result for the second harmonic (S21) suppression is 17.7 dB at a frequency of 14.7 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:535–538, 2014

Free-burning arcs where the work piece acts as an anode were numerically analyzed using a computational domain including the arc itself and its anode region based on the local thermodynamic equilibrium model. Because the major arc parameters such as temperature, axial velocity, electric potential difference and pressure-rise from ambient atmospheric pressure are much dependent on the working current, our investigation was concerned with developing a capability to model free-burning argon arcs and considering the energy flux going into the anode at various values of the electrical current (I = 50, 100 and 200 A) by computational fluid dynamics analysis. Predicted temperatures along the z-axis between the electrodes were in fair agreement with existing experimental results. Particularly, reasonable relationships between the maximum velocity or temperature and the applied current were predicted, which matched well with other theoretical results. In addition, some discrepancies with other predictions were shown in the results about electric potential and pressure-rise. It should be related to the omission of the space-charge effect near the electrodes for a simplified unified model and the application of a turbulence model for the steep temperature gradient at the arc edges.

A narrow-bandwidth dual-band (DB) band-pass filter (BPF) with λg/2 open stubs constructed using composite right/left-handed (CRLH) metamaterial transmission lines (TLs) is presented. A conventional narrow BPF with λg/2 open stubs is first designed using series λg/2 open stubs and λg/4 TLs. Then, a DB filter can then be easily implemented by replacing the microstrip lines with the CRLH-TL unit cells. The DB BPF using the CRLH-TL unit cell is experimentally demonstrated at dual-operating frequencies of 5.8 and 10.02 GHz. The experimental results are in good agreement with the simulation results. The DB BPF shows 11 and 13% pass bandwidth at the center frequencies of 5.8 and 10.02 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1887–1890, 2013

Magnetic-thermal-fluidic analyses were conducted to assess the cooling performance of magnetic nanofluids by comparing the performance with that of transformer oil and air using the fully coupled finite element method (FEM) considering the magnetoconvection phenomena. Magnetic nanofluids (MNFs) have been studied extensively for bio- and nanotechnology applications. In particular, some studies reported that the MNF has good characteristics for thermal management and electric insulation in experiments. With this motivation, this study focused on the cooling performance of MNFs including the experimental and numerical approaches. Until now, research on the cooling effect of MNF has focused mainly on heat propagation without any real magnetic system, in which the magnetic force plays a key role in driving fluidic flow. This flow driven by the magnetic force density was related to the magnetoconvection effect. To analyze this effect quantitatively, a coupled analysis technique should be developed using the magnetic-thermal-fluidic equations. To validate the cooling performance of MNFs numerically, the numerical results were verified by a comparison with those from the experimental tests in the air, transformer oil, and MNF. After confirming the numerical setup, some experiments were conducted with a vertical solenoid coil immersed in a MNF with different volume fractions of magnetic nanoparticles. The temperature at the inside part of the coil decreased dramatically by approximately 5 $^{\circ}$ C in the 7 vol. % MNF compared to the transformer oil. These temperatures were also predicted well using the proposed numerical setup.

In this article, a narrow-bandwidth duplexer with a triple-split ring resonator (T-SRR) using mu-negative metamaterial is presented. The T-SRR not only has negative permeability at the operating frequency band but also flexibility in size adjustment. The experimental results for insertion and return losses are 1.33 and 16.1 dB with a bandwidth of 10% at a RX center frequency of 8 GHz, and they are 1.27 and 16.8 dB at the same bandwidth at a TX center frequency of 10 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1537–1540, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27656

In this paper, a novel tunable bandpass filter with an improved J-inverter is suggested. In this resonator, as the loading capacitance is increased, the resonant frequency is decreased. Also, the phase of the admittance inverter has characteristics that are variable by series capacitors and parallel varactor diodes. The electrical length of the inverter always maintains 90° at a given physical length of the inverter, which should be changed for different operating frequencies. This new bandpass filter has a tuning range of 1.8 GHz ∼ 2.45 GHz and an insertion loss of less than 2.5 dB. Also, the bandwidth is almost constant within the tuning range. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:852–855, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27467

We report on the simulated performance of a two–layered Microstrip and Coplanar Waveguide (CPW) band-pass filters by using one layer simulation method. The two layer is composed of Ag(Ta0.5Nb0.5)O3 (ATN) thick film and alumina substrate. The ATN thick film of about 7 μm in thickness is prepared by screen printing method on an alumina substrate of about 635 μm in thickness at a sintered temperature and time of 1150°C and 2 hrs, respectively. Au conductor of about 2 μm in thickness is deposited by sputtering method. The 2-pole band-pass filters are designed for a center frequency of 5.88 GHz, and 5.76 GHz with 7.8% and 8.6% bandwidth, respectively. Both ATN-based filters offer a similar selectivity as well as a loss parameter compared to that of two-layer simulation.

The design of a differential-mode wideband bandpass filter (BPF) with good common-mode suppression is presented in this article. The structure of the proposed filter is divided to behave like a bandpass or bandstop filter (BSF) under differential- or common-mode operation. The open stubs in the BSF are used to control the 3-dB bandwidth (BW) of the BPF by slightly reducing the 3-dB cut-off BW of the BSF. To validate the design idea, a differential-mode BPF centered at 4 GHz with a 3-dB BW of 55%, near 30 dB common-mode suppression, is designed and fabricated. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:197–200, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27230

In SF6 self-blast interrupters, which are being developed as the next-generation switching mechanism, the arc burns within insulating nozzles with an ablation of the nozzle material and leads to an incoming gas flow for the pressure chamber with a pressure-rise during the high-current phase. Close to current zero, the arc can be cooled down and quenched completely by the reverse gas flow from the chamber to the arcing zone according to the pressure gradient between them. Therefore, the interruption of fault currents is dependent on the thermal decay of arcs during the current-zero phase by the blowing-off force, which is generated by the pressure-rise of the chamber during the high-current phase. In this study, we calculated SF6 arc plasmas caused by fault current interruption inside a SF6 self-blast interrupter using a computational fluid dynamics (CFD) technique and investigated the thermal interruption performance with thermal decay near current zero as well as the switching mechanism of the interrupter with an ablation of the nozzle material.

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This article proposed a new high-QL resonator with a combination of a double spiral resonator and single split ring resonator with μ- near zero metamaterial.It is applied to the design of an X-band oscillator. A very low phase noise for the oscillator can be obtained due to its sharp band- rejection characteristic of the new resonator. The oscillator is designed to operate at 9.2 GHz using the new resonator. Experimental results show the output power is 14.13 dBm, the second harmonic suppression is −46.33 dBc, and the phase noise is −104.54 dBc/Hz at 100-kHz offset. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1577–1582, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26867

In this article, a novel high QL triple-split ring resonator (T-SRR) of mu-negative metamaterial is suggested. It is used in the

In this article, a new compact branch-line coupler with third harmonics suppression using the meander T-shaped line is suggested. The meander T-shaped line works similar to a bandstop filter at the second and third harmonics frequencies. The size of the proposed coupler is 22.2 × 14.9 mm2, while a conventional coupler is 32.6 × 27.8 mm2. Thus, the proposed coupler is considerably smaller than the conventional coupler. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1382–1384, 2014

In this article, the dualband bandpass filters (BPFs) using dual-mode resonator are designed and implemented. Also, the J-inverter is investigated as function of the impedance and the electrical length of the open-stub in the dual-mode λg/2 microstrip resonator. Especially, the dualband BPFs using dual-mode resonator are realized by the stepped impedance resonator (SIR) structure and have good out-of-band performance as the inverter is alternating by the coupling structure and tapped-line geometry. The first transmission zero of the dualband BPFs is made by the dual-mode resonator and the second transmission zero is defined by the open-stub of the tapped-line geometry as a function of J-inverter. The dualband BPF using dual-mode resonator with two transmission zeros shows the insertion losses of 1.92 and 1.71 dB at the center frequency of 2.42 and 5.65 GHz, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:108–111, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25627

In this article, a compact dual-mode λg/2 bandpass filter with the characteristic of harmonic rejection is designed and implemented.The second and third harmonics of the suggested bandpass filter are rejected by using the additional open stubs of the T-type equivalent circuit for the quarter wavelength line. Also, the J-inverter is investigated as functions of the impedance and electrical length of the open stub of dual-mode λg/2 resonator. From the results, the lower impedance of open stub of dual-mode λg/2 resonator is better for the good performance of the dual-mode λg/2 bandpass filter. The harmonic-rejected dual-mode λg/2 bandpass filter shows the characteristic of suppression of harmonics until 8 GHz and the insertion and return losses of 0.96 and 18.89 dB, respectively, at the center frequency of 2.43 GHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2288–2291, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25457

In this article, a narrow band pass filter with reduced size using the λg/4 short stubs is presented.The filter size is reduced by realization of transmission line at the second harmonic while the power can be transferred to the output using the fundamental frequency band generated in the resonator and the transmission line in which the impedance mismatching technique is adopted. The experimental results show that the insertion loss is 2.0 dB and return loss is 11.1 dB, and the fractional bandwidth is 10% at the center frequency of 5.8 GHz. The filter size is 19.7 × 8.6 mm2. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 2002–2005, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25419

This article reports a novel broadband rectifying antenna (rectenna) using the printed monopole antenna and the band-pass stub band-pass filter, which is designed in the microstrip line structure at 2.45 GHz for the wireless transmission of microwave power. We suggest a novel H-shape printed monopole antenna with size reduction of the radiator and the ground plane using surface current distribution, and a broadband stub band-pass filter with suppression of the second harmonic. The rectifying circuit with stub filter doesn't need additional area because it is fabricated on the ground plane, which is widened to acquire broadband characteristic of the monopole antenna. The RF-to- DC conversion efficiency of 66% is obtained by using a load resistor of 270 X at 2.45 GHz. Also, the conversion efficiency is maintained from 2 GHz to 3 GHz above 50%. V C 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1194-1197, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25130

It is reported that CuInO2 single phase is hardly obtainable by using the general mixed oxide synthesis route [M. Shimode, M. Sasaki, K. Mukaida, J. Solid State Chem. 151(1) (2000) 16.; L. Liu, K. Bai, H. Gong, P. Wu, Phys. Rev. B 72(12) (2005) 1252041.; H. Hahnn, C. Lorent, Z. Anorg. Allg. Chem. 279 (1955) 281.]. Therefore, the manufacturing of highly dense single phase targets for CuInO2 thin film growing is still challenging. In this study, a Cu2O–In2O3 composite target instead of a CuInO2 single phase target was fabricated by using the general mixed oxide synthesis route. Thin films of CuInO2 were grown on sapphire substrates by a pulsed laser deposition (PLD) process under various conditions, and c-axis oriented single phase CuInO2 thin films were grown successfully when oxygen partial pressure was controlled.

A simplified mathematical design method for tapped-line geometry is presented and the stub bandpass filters (BPFs) of λg/4 and λg/2 stubs with a center frequency of 5.8 GHz and a bandwidth of 5% are successfully designed, fabricated, and characterized using this approach. Design parameters for the tapped-line geometry of the filter prototypes are obtained using input (output) admittance toward source (load), where the open-stub and the additional transmission-line with a negative electrical length are taken into account for filter implementation. The electrical lengths of the stubs and lines are functions of the line admittance and J-inverter. The filters are implemented on a RT-duroid substrate and the results from modeling and measurement show good agreement with each other. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2338–2341, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24615

In this article, a broadband double-balanced mixer is presented using a wideband Marchand balun implementation by vertical coupler. Frequency is selected as 1.0–3.7 GHz for radio frequency (RF), 1.14–3.84 GHz for LO, and 140 MHz for IF signals. When LO signal with 7 dBm at 2.64 GHz is injected, a conversion loss of 7.5 dB, and RF to LO isolation of −45 dB are obtained. Also, an average conversion loss of 9 dB, and RF to LO isolation of −25 dB are obtained for frequency band of 1.0–3.7 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1811–1814, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24488

In this paper, the harmonics suppressed waveguide filter with SIW (substrate-integrated waveguide) structure using inductive windows at satellite communication band is discussed. The SIW structure is realized by via-holes and can be integrated with other circuits on the same substrate. The SIW filter has the insertion loss of 2.85 dB and return loss of 17.57 dB at the center frequency of 12 GHz. Also, the proposed SIW filter has the harmonics suppression under 20 dB until 30 GHz by inserted low-pass filter (LPF). This harmonics suppressed SIW filter can be used in satellite communication systems. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 447–450, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23114

In this article, λg/2 open stub bandpass filters with flexible narrow bandwidth on duroid substrate are presented. This filters show flexible bandwidth with variation of the position of the open stubs using the external quality factor, Qe without changing the impedance value at microwave range. On the other hand, by replacing the series quarter-wavelength connecting-lines with the equivalent T-shaped line, a compact stub bandpass filter with second harmonic suppression can be obtained. This filter shows the insertion loss of 1.2 dB and the return loss of 21.9 dB at the center frequency of 5.8 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1763–1766, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23492

(100) epitaxial Ba0.6Sr0.4TiO3 (BST) thin films were grown on Si substrates using a 9 nm thick SrO buffer layer. The phase shifter fabricated on BST films grown on a SrO buffered Si substrate showed a larger figure of merit (FOM) of 24.7°/dB as a result of improving the phase tuning while retaining an appropriate insertion loss compared to that (15.3°/dB) for the BST/MgO structure. This work demonstrates that a thin SrO buffer layer plays an important role in the successful integration of BST-based microwave tunable devices onto Si wafers.

In this letter, a novel design method of tapped-line gap-coupled half-wavelength band-pass filter (BPF) using J- or K-inverter is proposed. A model of tapped-line is composed of shunt stub and the additional transmission line that has the electrical length of the negative value. The electrical lengths of the stub and line are functions of the line's impedance and the inverter that has a variable of filter's bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1253–1256, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22417

In this paper, a broadband microstrip Marchand balun is presented. It is implemented by new vertical coupled structure, which is suggested to improve the coupling effect in the conventional coupler. Using this vertical coupling structure, the Marchand balun shows broad bandwidth of larger than 115% at the center frequency of 2.3 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 752–755, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22281

In this article, the potential feasibility of integrating BST films into Si wafer by adopting tunable interdigital capacitor (IDC) with TiO2 thin film buffer layer is suggested. TiO2 as buffer layer is grown onto Si substrate by atomic layer deposition and the coplanar IDC on BaxSr1−xTiO3(500 nm)/TiO2(50 nm)/high resistivity Si (HR-Si) is fabricated. BST interdigital tunable capacitors integrated on HR-Si substrate with high tunability and low loss tangent are characterized for their microwave performances. BST/HR-Si and BST/TiO2/HR-Si IDCs show much enhanced tunability values of 31% and 40%, respectively as compared to the value of 21% obtained with BST film on MgO single crystal substrate at the bias of 5 kV/cm. BST/TiO2/HR-Si structure shows much improved figure of merit of 504.4 as compared to 418.53 and 101.68 of BST/MgO and BST/HR-Si structure, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2144–2148, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22657

We report on high tunablity of Ba0.6Sr0.4TiO3 (BST) thin films realized through the use of atomic layer deposited TiO2 films as a microwave buffer layer between BST and a high resistivity (HR) Si substrate. Coplanar waveguide (CPW) meander-line phase shifters using BST/TiO2/HR-Si and BST/MgO structures exhibited a differential phase shift of 95∘ and 24.4∘, respectively, at 15 GHz under an electric field of 10 kV/cm. The figure of merit of the phase shifters at 15 GHz was 30.6∘/dB for BST film grown on a TiO2/HR-Si substrate and 12.2∘/dB for BST film grown on a MgO single crystal substrate. These results constitute significant progress in integrating BST films with conventional silicon technology.

In this paper, a new microstrip stepped-impedance hairpin resonator with interdigital capacitor (IDC) slow-wave band-pass filter (BPF) using dielectric supported air-gapped microstrip line (DAML) of surface micromachining on GaAs substrate is proposed. Unlike conventional slow-wave filters, the proposed bandpass filters are designed to produce a narrow passband at the fundamental mode of the resonators with small size and a sharp skirt characteristic. The proposed slow-wave band-pass filter with IDC is designed to produce a passband of 7.7% at the fundamental frequency of 56 GHz. It shows insertion loss of 3.37 dB, return loss of better than 15 dB, and a stopband characteristic greater than 31 dB within 37.03–45.51 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1244–1247, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21667

In this paper, new design method of a bandpass filter (BPF) using tapped-line structure is suggested on BST/MgO substrate. A tunable BPF with interdigital capacitor (IDC) using BST thin film is successfully demonstrated for the improved tunability characteristic. The center frequency of the tunable hair-pin BPF with IDC is moved from 6.08 GHz to 6.30 GHz at 50 V bias with 2% bandwidth.