Bias Voltage Level Research Articles

Optimization of dual-electrode ratio and driving phase of piezoelectric MEMS speakers for improving sound pressure level

The integration of dual-electrode driving to enhance diaphragm deformation, thereby increasing the diaphragm’s average out-of-plane displacement, has proven to be effective in improving the sound pressure level (SPL) of MEMS speakers. In this work, a piezoelectric MEMS speaker with a quasi-enclosed diaphragm and a dual-top electrode (inner and outer) configuration is proposed. With the inner electrode area ideally configured at 70 % of the whole diaphragm, the MEMS speaker with a diaphragm of 2.5 × 2.5 mm2 demonstrates an SPL higher than 73.5 dB in the frequency range from 1 kHz to 20 kHz at a driving voltage of only 2 Vpp. The acoustic performance of the dual-electrode MEMS speaker was also investigated by applying a series of driving signals with different phases and bias voltages to the inner and outer electrodes. It is found that the optimal driving phase varies across different frequency ranges and is dependent on the bias voltage level as well. Moreover, an adequate bias voltage was noted to incrementally enhance the SPL. With proper driving signals optimization, the proposed MEMS speaker achieves an SPL over 88 dB from 100 Hz to 20 kHz at 15 Vpp AC and −2.5 VDC bias voltage. This study furnishes an effective electrode design methodology and driving scheme for the practical deployment of MEMS loudspeakers in future applications.

Control of the preferential orientation and properties of HiPIMS and DCMS deposited chromium coating based on bias voltage

This study investigates the effects of varying bias voltages on the crystallographic orientation and properties of DCMS + HiPIMS-deposited chromium coatings. Under bias voltages varying from 100 to 500 V, dense Cr coatings were obtained, and the deposition rate decreased by 13 %. The bias voltage significantly impacts the hardness, crystallographic orientation, electrical conductivity, and bonding strength of the coating. As the bias voltage increases, the hardness of the Cr coating gradually increases. The crystallographic orientation of the coating is governed collectively by surface energy, strain energy, and sputtering effects. The preferential crystallographic orientation of the Cr coating transitions from (222) to (110), subsequently changing to a mixed preferential crystallographic orientation of (110), (211), and (222). Under the combined influence of thermal effects and ion bombardment, a (110) preferential crystallographic orientation was obtained at a bias voltage of 300 V, featuring moderate hardness and optimal wear resistance. This study establishes that the electrical characteristics of the coatings have a significant correlation with bias voltage levels.

Thermal sensing capability and current–voltage–temperature characteristics in Pt/n-GaP/Al/Ti Schottky diodes

We have discussed the thermal sensing capability under a constant current level and current versus voltage (I–V) traces by measuring the temperature of high series resistance Pt/n-GaP/Al/Ti Schottky structures in the 100−320 K range. The Rs values of 35 Ω and 4.50 × 103 kΩ for the device have been determined from I–V traces at 320 and 100 K, respectively. The thermal sensing (V–T) curves are expected to give a straight line at each current level. However, the V–T curves have deviated upward from linearity due to the high Rs value of the device after a certain temperature. The deviation point from linearity in V–T traces shifts to higher temperatures with an increase in bias voltage and current level. Thereby, the straight-line interval portion of the V–T curve has become too small with an increase in the current value. The thermal sensing coefficient α changed from 2.49 mV/K at 10 μA to 3.21 mV/K at 0.50 nA. Therefore, it has been concluded that the Pt/n-GaP/Al/Ti Schottky barrier (SB) is preferable for thermal sensor applications at the small current levels of 0.50, 1.0, 2.0, and 10.0 nA with high sensitivity up to a minimum temperature of 100 K. From I–V curves, qΦb0 and ideality factor values have ranged from 1.200 eV and 1.066 at 320 K to 0.854 eV and 1.705 at 100 K. It has been reported in the literature that the large SB height leads to a better temperature response.

Demonstration of giant anisotropic magnetoresistance, high spin filtering efficiency, and negative differential resistance in nanodevices based on oxygen doped black arsenic phosphorus nanoribbons

We investigate the electrical properties of pure black arsenic phosphorus and oxygen atom doped monolayer black arsenic phosphorus using first principle calculations. The density of states results reveals that oxygen atom doped black arsenic phosphorus is a magnetic semiconductor. The current-voltage characteristic curves of oxygen atom doped monolayer black arsenic phosphorus nanoribbons based devices have been determined using the non-equilibrium Green's function associated with the density function theory. The results demonstrate that the device made of doped black arsenic phosphorus has a substantial current difference between armchair and zigzag black arsenic phosphorus nanoribbons, implying that the device made of nanoribbons has a large anisotropic magnetoresistance. The spin filtering efficiency is nearly 100% at some bias voltage levels, and the transmission spectrums of the associated bias voltage window can explain the significant negative differential resistance. Furthermore, these findings suggest that oxygen atom doped black arsenic-phosphorus nanoribbons are suitable for spintronic devices.

100GHz micrometer-compact broadband monolithic ITO Mach-Zehnder interferometer modulator enabling 3500 times higher packing density.

Electro-optic modulators provide a key function in optical transceivers and increasingly in photonic programmable application-specific integrated circuits (ASICs) for machine learning and signal processing. However, both foundry-ready silicon-based modulators and conventional material-based devices utilizing lithium-niobate fall short in simultaneously providing high chip packaging density andfast speed. Current-driven ITO-based modulators havethe potential to achieve both enabled by efficient light-matter interactions. Here, we introduce micrometer-compact Mach-Zehnder interferometer (MZI)-based modulators capable of exceeding 100GHz switching rates. Integrating ITO-thin films atop a photonic waveguide, one can achieve an efficient =0.1Vmm, spectrally broadband, and compact MZI phase shifter. Remarkably, this allows integrating more than 3500 of these modulators within the same chip area as only one single silicon MZI modulator. The modulator design introduced here features a holistic photonic, electronic, and RF-based optimization and includes an asymmetric MZI tuning step to optimize the extinction ratio (ER)-to-insertion loss (IL) and dielectric thickness sweep to balance the trade-offs between ER and speed. Driven by CMOS compatible bias voltage levels, this device is the first to address next-generation modulator demands for processors of the machine intelligence revolution, in addition to the edge and cloud computing demands as well as optical transceivers alike.

Analysis of Random Body Bias Application in FDSOI Cryptosystems as a Countermeasure to Leakage-Based Power Analysis Attacks

This paper analyses a novel countermeasure to Leakage Power Analysis Attacks based on the application of a random Body Bias voltage level at the beginning of the encryption process. The countermeasure effectiveness is established through the development of a theoretical model of the Pearson correlation coefficient in the presence of a varying body bias under both noiseless assumptions and in the presence of algorithmic noise, and through simulations on a partial cryptosystem implemented in 28 nm FDSOI technology. A study of the effect of averaging power measurements is also developed and contrasted against Monte Carlo simulations of the countermeasure scheme, effectively providing a floor for the increase in required measurements to identify the secret key.

Effect of Bias Voltage on Mechanical Properties of HiPIMS/RFMS Cosputtered Zr-Si-N Films.

Zr–Si–N films with atomic ratios of N/(Zr + Si) of 0.54–0.82 were fabricated through high-power impulse magnetron sputtering (HiPIMS)–radio-frequency magnetron sputtering (RFMS) cosputtering by applying an average HiPIMS power of 300 W on the Zr target, various RF power levels on the Si target, and negative bias voltage levels of 0–150 V connected to the substrate holder. Applying a negative bias voltage on substrates enhanced the ion bombardment effect, which affected the chemical compositions, mechanical properties, and residual stress of the Zr–Si–N films. The results indicated that Zr–Si–N films with Si content ranging from 1.4 to 6.3 atom % exhibited a high hardness level of 33.2–34.6 GPa accompanied with a compressive stress of 4.3–6.4 GPa, an H/E* level of 0.080–0.107, an H3/E*2 level of 0.21–0.39 GPa, and an elastic recovery of 62–72%.

Digitally-Controlled Dynamic Bias Switching을 이용한 LTE 기지국용 전력증폭기의 효율 개선

Abstract This paper presents an efficiency enhancement for the high power amplifier using DDBS(Digitally-controlled Dynamic Bias Switching) method which dynamically provides the power amplifier with two bias voltage levels according to the input envelope signal. It is quite easy to adjust the control signal by using a digital processing. The fabricated DDBS PA was evaluated using an 64 QAM FDD LTE signal, which has a center frequency of 2.6 GHz, a bandwidth of 10 MHz and a PAPR of 9.5 dB. The DDBS increases the power amplifier’s PAE(Power-Added Efficiency) from 40.9 % to 48 %, at an average output power level of 43 dBm. Key words: Digitally-Controlled Dynamic Bias Switching, Envelope Tracking, High Power Amplifier  IJK1LM N(CN JOJKAP(QRS3 /XY1ZClass-S .JK.[ \]>^_C`Ya^N(School of Information and Communication Engineering, Sungkyunkwan University) *DZbYJKc(Electronics and Telecommunications Research Institute)Manuscript received June 26, 2014 ; Revised July 29, 2014 ; Accepted August 6, 2014. (ID No. 20140626-01S)Corresponding Author: Youngoo Yang (e-mail: yang09@.skku.edu)

Self-Heterodyne Spectrometer Using Uni-Traveling-Carrier Photodiodes for Terahertz-Wave Generators and Optoelectronic Mixers

We demonstrate a self-heterodyne terahertz (THz) frequency-domain spectrometer in which commercially available uni-traveling-carrier photodiodes (UTC-PDs) are used as optical-to-electrical (O/E) converter and optoelectronic mixer (OEM). The optical intensity beat generated by mixing two frequency-detuned free-running 1.55 $\mu$ m laser diodes (LDs) is used as a source for the photomixing at the O/E converter, and as an optical local oscillator (LO) signal for the OEM. The frequency of the optical LO signal is coherently shifted with an electrooptic frequency shifter so that the heterodyne detection is realized using free-running LDs for the beat source. We investigate the sensitivity characteristics of the spectrometer as functions of diode bias voltage and optical LO level. The maximum signal-to-noise ratio of 47 dB for the RF power of $-$ 16 dBm is achieved at 300 GHz with the lock-in time constant of 23.4 ms. The standard deviation of the phase measurement is 0.73 $^\circ$ , where the amplitude noise limited standard deviation is 0.25 $^\circ$ . We measure the system response ranging from 200 to 1450 GHz and find that it fits well the response which is calculated using the frequency characteristics of the output power of the UTC-PDs. Our results show that UTC-PDs are promising candidates not only for the high-power terahertz wave generator, but also for the wide-band THz-OEM. Integration of UTC-PDs with free-running LDs on the same substrate with the same process steps would significantly reduce the cost and size of the present spectrometer.

A highly linear squarer design for energy-detection RF receivers

A highly linear Gilbert cell squarer is designed using a modified derivative superposition (MDS) technique, which employs a pair of NMOS–PMOS auxiliary transistors in weak inversion and an auxiliary PMOS transistor in moderate inversion. This technique reduces the inherent sensitivity of derivative superposition linearization schemes to bias voltage level. The Volterra series analysis of the squarer is reported to examine the effectiveness of the new technique. Simulation result using TSMC 0.13μm CMOS technology, demonstrates that MDS gives rise to 15dB improvement in IIP2 and 5dB improvement in IIP3 of squarer. Moreover, Bias voltage of squarer can be tolerated within 0.45–0.6V with acceptable IIP2 and IIP3 performances. The new linearization technique is applicable to RF modules in many wireless communications.

(Invited) Technological Approaches Towards High Voltage, Fast Switching GaN Power Transistors

Approaches towards fast switching GaN devices for applications in power electronics are discussed. First, an overview on the most prominent techniques towards increased breakdown voltage will be given for devices grown on SiC and Si substrates. These tech-niques will then be set in relation to dynamic switching properties at different bias voltage levels. Dynamic switching properties are still lagging behind competing devices, especially if switching at high bias levels is considered. The switching properties are usually expressed by the so-called dynamic on-state resistance. It signifi-cantly depends on technological parameters such as epitaxial layer design and crystalline quality of the buffer layer, passivation layers and, last but not least the lateral device designs (e.g. field plate ar-rangements). A balanced trade-off between all these influencing quantities is shown and correlated to current state of GaN high voltage switching devices.

Implementing a Piezoelectric Transformer for a Ferroelectric Phase Shifter Circuit

This paper describes the successful development of a piezoelectric transformer-based driver circuit used to bias a ferroelectric phase shifter. The proof-of-concept circuit achieves voltages in excess of 400 VDC and accomplishes 0 to 180 degrees of phase shift at Ka-band. The ferroelectric phase shifter is the fundamental component in a new type of scanning phased array, the ferroelectric reflectarray. The coplanar ferroelectric phase shifter requires only one control signal, currently generated by magnetic circuit components. However magnetic devices suffer from resistive and magnetic losses, and dimensional and economic costs. New phased array architecture, not reliant on magnetics, can be realized because the piezoelectric transformer allows a low level signal to be routed to each phase shifter and converted to the proper bias voltage levels at each phase shifter. This research explores the use of a piezoelectric transformer (PT) as the alternative enabling component in the voltage supply for a ferroelectric phase shifter utilizing piezoelectrics in an AC-DC converter.

Phase and Quadrature Pulsed Bias LC-CMOS VCO

Pulsed bias is an attempt to improve the performance of oscillators in integrated circuits as a result of architectural innovation. Given the relatively low value of resonator quality factor achievable on-chip, for a specified bias voltage level, pulsed bias may result in a lower power consumption and in an improvement of the spectral purity of the oscillation. The main drawback of this approach is the need to introduce a certain time delay in order to properly position pulses with respect to oscillation waveform. Delay accumulation requires further energy dissipation and introduce additional jitter. In this paper we present a new architecture capable to avoid unnecessary delay, based on the idea to apply the pulsed bias approach to a quadrature oscillator. A ?rst circuit-level implementation of this concept is presented with simulation results.

Dynamic Bias Switching을 이용한 3.5 GHz Balanced Power Amplifier의 효율 개선

본 논문에서는 3.5 GHz에 설계된 balanced amplifier에 DBS(Dynamic Bias Switching)를 적용하여 평균 전력에서 효율을 개선하였다. DBS는 입력 신호의 포락선 크기에 따라 전력 증폭기에 두 단계의 드레인 전압을 인가하여 효율을 개선하는 기술로써 balanced amplifier에 DBS를 적용하기 위해서 동일하게 구성된 DBS 회로를 각 단에 설치하여 실제 제작하였다. 20 MHz 대역폭과 8.5 dB의 PAR(Peak to Average Ratio)을 갖는 OFDM 신호를 사용하여 측정한 결과, 28 V 단일 드레인 전압을 사용했을 때보다 42.5 dBm에서 6 %의 PAE 개선을 나타냈다. This paper presents an efficiency enhancement for the balanced power amplifier using DBS(Dynamic Bias Switching) method which dynamically provides the power amplifier with two bias voltage levels according to the input envelope signal. In order to apply the dynamic biases to each side of the balanced power amplifier, two switching stages are adopted. Using an OFDM signal with a bandwidth of 20 MHz and a PAR(Peak to Average Ratio) of 8.5 dB, 6 % of PAE(Power-Added Efficiency) is improved at an output power of 42.5 dBm.

Magnetoelectric, pinning and depinning properties in Pb(Zr0.5Ti0.5)O3/Fe3O4 composite films

The magnetoelectric (ME) coupling effect was demonstrated in sol–gel deposited Pb(Zr,Ti)O3 films embedded by Fe3O4 nanoparticles. The polarization–field hysteresis curves show ‘pinched’ shapes at room temperature and higher frequencies, whereas they display normal square-like loops at 150 °C and frequencies lower than 0.5 Hz. Our data confirm that the pinched loop can be relaxed after the Pb(Zr,Ti)O3/Fe3O4 composite films are poled magnetically, and an anisotropic magnetoelectric (ME) coupling effect is demonstrated. Analysis of the dc voltage dependence of the dielectric response indicates two peaks of dielectric constant loops for each half cycle at lower temperatures and bias voltages, which are different from the butterfly shape for normal ferroelectrics. Nevertheless, the normal butterfly hysteresis loops are presented at 360 K and at a bias voltage level of 25 V. The occurrence of pinched polarization–voltage loops and two peaks of dielectric constant curves for each half cycle may be attributed to the unintentional doping of iron ions in Pb(Zr,Ti)O3/Fe3O4 composite films.

An Analog RF MEMS Slotline True-Time-Delay Phase Shifter

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> An analog RF microelectromechanical systems (MEMS) slotline true-time-delay (TTD) phase shifter is presented for use in conjunction with tapered slot antennas, such as the Vivaldi aerial and the double exponentially tapered slot antenna. The design is a scalable distributed loaded-line cascade of 62 novel differential slow-wave unit cells. Each differential slow-wave unit cell comprises an electrically short slotline section, which is loaded with a shunt impedance consisting of two center-pulled contactless fixedfixed beam RF MEMS varactors in series, sharing a common electrode. The analog RF MEMS slotline TTD phase shifter is demonstrated on a borosilicate glass wafer using a microfabrication process requiring six masks. It is designed for transistortransistor logic bias voltage levels and exhibits a measured phase shift of 28.2$^{\circ}/{\hbox{dB}}$ (7.8 ps/dB) and 59.2$^{\circ}/{\hbox{cm}}$ at 10 GHz, maintaining a 75-$\Omega$ differential impedance match $(S_{11_{dd}}&lt;-15.8\ {\hbox{dB}})$ . The input third-order intercept point is 5 dBm at 10 GHz for a $\Delta{ f}$ of 50 kHz, measured in a 100-$\Omega$ differential transmission line system. Design and fabrication opportunities, concerning distortion and loss reduction, as well as packaging, are highlighted. </para>

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies--500 kHz to 30 MHz, and rf bias waveforms--sinusoidal, square, and dual frequency.

Effects of applied substrate bias during reactive sputter deposition of nanocomposite tantalum carbide/amorphous hydrocarbon thin films

Nanocomposite tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin film composition, structure, and mechanical properties depend on the direct current bias voltage ( V b) level applied to the substrate during reactive sputter deposition. A set of TaC/a-C:H films was deposited across the range V b = 0 to − 300 V with all other deposition parameters held constant except substrate temperature, which was allowed to reach its steady state during the depositions. Effects of V b on film composition and structure were explored, including TaC crystallite size and dispersion using X-ray diffraction and high resolution transmission electron microscopy. In addition, the dependency of stress and hardness on V b was studied with an emphasis on relationships to a-C:H phase structure.

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh)−1. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh)−1, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Mechanical property development in reactively sputtered tantalum carbide/amorphous hydrocarbon thin films

Hardness, elastic modulus, and stress directly influence the ability of tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin films to enhance the wear-resistance of steel tribological component surfaces. Designed factorial experiments enabled an evaluation of the effects of acetylene flow rate (QC2H2), direct current bias voltage level (Vb), and substrate rotation rate (ωRot) during deposition on the mechanical properties of reactively sputtered TaC/a-C:H films. Significant relationships were found between compressive stress level and Vb, whereas hardness and elastic modulus were dependent primarily on Vb and secondarily on QC2H2 within the studied parameter space. It is proposed that effects of ion bombardment on the a-C:H phase during growth are responsible for property dependencies on Vb. Decreases in hardness and elastic modulus with increasing QC2H2 are attributed to increased hydrogen concentration and a concomitant decreased volume fraction of TaC crystallites in the films.