V‐shaped electro‐optical mode based on deformed‐helix ferroelectric liquid crystal with subwavelength pitch

Abstract— V‐shaped electro‐optical response is shown, both theoretically and experimentally, to be an inherent property of a deformed‐helix ferroelectric liquid‐crystal cell (DHFLC) under a special choice of the applied rectangular alternating‐electric‐field waveform, frequency, and cell geometry. In contrast to other known V‐shaped ferroelectric liquid‐crystal (FLC) modes, the discovered V‐shaped switching is observed in a broadband frequency range including 1 kHz, and not at a certain characteristic frequency. This type of V‐shaped switching allows for a drastic increase in the operating frequency of field‐sequential‐color (FSC) LCD cells in comparison with fast nematic liquid‐crystal (NLC) modes.     

Solution‐processed and low‐temperature metal oxide n‐channel thin‐film transistors and low‐voltage complementary circuitry on large‐area flexible polyimide foil

High‐performance solution‐based n‐type metal oxide thin‐film transistors (TFTs), fabricated directly on polyimide foil at a post‐annealing temperature of only 250 °C, are realized and reported. Saturation mobilities exceeding 2 cm²/(Vs) and on‐to‐off current ratios up to 10⁸ are achieved. The usage of these oxide n‐type TFTs as the pixel drive and select transistors in future flexible active‐matrix organic light‐emitting diode (AMOLED) displays is proposed. With these oxide n‐type TFTs, fast and low‐voltage n‐type only flexible circuitry is demonstrated. Furthermore, a complete 8‐bit radio‐frequency identification transponder chip on foil has been fabricated and measured, to prove that these oxide n‐type TFTs have reached already a high level of yield and reliability. The integration of the same solution‐based oxide n‐type TFTs with organic p‐type TFTs into hybrid complementary circuitry on polyimide foil is demonstrated. A comparison between both the n‐type only and complementary elementary circuitry shows the high potential of this hybrid complementary technology for future line‐drive circuitry embedded at the borders of flexible AMOLED displays.     

Spectroscopic analysis of the non‐circular external electrode fluorescent lamp for large‐sized LCD backlight applications

Abstract— The spectroscopic analysis of the external electrode fluorescent lamp (EEFL) having non‐circular cross sections was carried out in order to obtain insight into the discharge condition confined in this unusual discharge space. The emitting spectra of EEFLs with and without phosphor layers were investigated as a function of the measurement position and/or time. It was found that the argon (Ar) emission was intense when the lamp was turned on and decreased rapidly as the Hg emission lines got stronger. The intensities of visible lines from mercury atoms were measured as a function of position along the direction perpendicular to the channel axis. It was found that the positive column does not spread in the entire discharge space but was contracted at the center of the channel. This result was discussed in relation to the ionization process occurring in the low‐pressure discharge lamps. In addition, the correlation between the cross‐sectional shape and the backlight efficiency was investigated, from which optimized shape parameters could be derived.     

A novel TFT‐OLED integration for OLED‐independent pixel programming in amorphous‐Si AMOLED pixels

Abstract— The direct voltage programming of active‐matrix organic light‐emitting‐diode (AMOLED) pixels with n‐channel amorphous‐Si (a‐Si) TFTs requires a contact between the driving TFT and the OLED cathode. Current processing constraints only permit connecting the driving TFT to the OLED anode. Here, a new “inverted” integration technique which makes the direct programming possible by connecting the driver n‐channel a‐Si TFT to the OLED cathode is demonstrated. As a result, the pixel drive current increases by an order of magnitude for the same data voltages and the pixel data voltage for turn‐on drops by several volts. In addition, the pixel drive current becomes independent of the OLED characteristics so that OLED aging does not affect the pixel current. Furthermore, the new integration technique is modified to allow substrate rotation during OLED evaporation to improve the pixel yield and uniformity. The new integration technique is important for realizing active‐matrix OLED displays with a‐Si technology and conventional bottom‐anode OLEDs.     

A cross‐coupling controller using an H∞ scheme and its application to a two‐axis direct‐drive robot

A cross‐coupling controller (CCC) using an H_∞ control scheme has been proposed to reduce the contouring error for a two‐axis, direct‐drive robot in tracking linear and circular contours effectively. Under the consideration that contour‐tracking performance is a primary target over point‐to‐point tracking performance in a trajectory‐tracking task, a CCC has been associated with joint controllers to reduce the contouring error by coordinating the motion of a two‐axis robot arm. Contouring performance can thus be improved significantly. Furthermore, the proposed CCC design, which is a typical Multi‐Input Multi‐Output (MIMO) system with linear time varying (LTV) characteristics, has been verified as being internally stable. A USM (ultrasonic motor)‐driven, two‐axis, direct‐drive robot is utilized to demonstrate the feasibility of the proposed scheme. Several experiments under various operating conditions are performed to validate its efficacy, and the results showed that the proposed scheme can reduce the contouring error significantly. © 2002 Wiley Periodicals, Inc.     

Multi‐dimensional asymptotic waveform evaluation method and adaptive hopping technique

The multi‐dimensional asymptotic waveform evaluation (MD‐AWE) method is proposed as an extension of the conventional one dimensional asymptotic waveform evaluation (1D‐AWE) method. It can be applied in parameter analysis of structures, particularly with multiple variables, at which repeated calculations are required. The MD‐AWE is proposed at first, and then an adaptive hopping technique similar to the complex frequency hopping (CFH) technique to expand the approximation region of MD‐AWE is delivered, and this technique also helps to reduce the memory usage by taking lower order of MD‐AWE. In the end, two examples are given with good results, which show the efficiency and accuracy of the proposed method. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Efficient and compact green laser for micro‐projector applications

Abstract— Efficient and compact green lasers are keystone components for micro‐projector applications in mobile devices. An architecture that consists of an infrared‐producing DBR (distributed Bragg reflector) laser with a frequency‐doubling crystal is used to synthesize a green laser that has high electrical‐to‐optical conversion efficiency and can be modulated at speeds required for scanner‐based projectors. The design and performance of a green‐laser package that uses adaptive optics to overcome the challenge of maintaining alignment between the waveguides of the DBR laser and the frequency‐doubling crystal over temperature and lifetime is described. The adaptive optics technology that is employed uses the piezo‐based smooth impact drive mechanism (SIDM) actuators that offer a very small step size and a range of travel adequate for the alignment operation. The laser is shown to be compact (0.7 cm³ in volume) and capable of a wall‐plug efficiency approaching 10% (at 100‐mW green power). It was demonstrated that the adaptive optics enables operation over a wide temperature range (10–60°C) and provides the capability for low‐cost assembly of the device.     

Address‐While‐Display technique combined with gas‐discharge AND logic for driving AC‐PDPs

A hybrid AWD/AND drive technique has been developed in which an Address‐While‐Display (AWD) scheme is combined with an AND logic characteristic that gas discharges demonstrate. The AWD technique enables AC‐PDPs to be driven at high luminance, while the AND logic reduces the number of scan drivers by an order of magnitude. A detailed analysis of the addressing operation has been made. The hybrid drive utilizes the AND logic in two ways: (1) a combination of two voltage pulses and (2) a combination of a voltage pulse and discharge‐priming particles. It was found that the addressing operation requires the establishment of a discharge between the scan and data electrodes, and also between the scan and display electrodes.     

Waveform engineering: State‐of‐the‐art and future trends (invited paper)

The term waveform engineering denotes all those circuit design techniques that are based on shaping the transistor voltage and current waveforms. From a general perspective, these design techniques can be grouped in two main categories according to the adopted design tool: measurement‐ and model‐based. In the last two decades, thanks to the proliferation of setups enabling calibrated waveform acquisition at microwave frequencies, waveform engineering has attracted continuously increasing interest in the microwave engineering community. In this article, a comprehensive analysis of the waveform‐engineering based design techniques is reported, paying particular attention to the advantages and drawbacks associated to each approach.     

High‐frequency drive of high‐Xe‐content PDPs for high efficiency and low‐voltage performance

Abstract— It has been well known that the luminous efficiency of PDPs can be improved by increasing the Xe content in the panel. For instance, the efficiency is improved by a factor 1.7 when the Xe content is increased from 3.5% to 30%. The sustain pulse voltage, however, increases from 180 to 230 V by a factor 1.3. It was found that the increase in the sustain pulse voltage can be suppressed by increasing the sustain pulse frequency. The high‐frequency operation further increases the luminous efficiency. If the Xe content is increased from 3.5% to 30% and the drive pulse frequency is increased from 147 to 313 kHz, the luminous efficiency becomes 2.7 times higher and the luminance 4.5 times higher. Furthermore, the increase in the sustain pulse voltage is suppressed 1.1 times, from 180 to 200 V. A mechanism of attaining high efficiency and low‐voltage performance can be considered as follows. A train of pulses is applied during a sustain period. As the sustain pulse frequency is increased, the pulse repetition rate becomes faster and a percentage of the space charge created by the previous pulse remains until the following pulse is applied. Due to the priming effect of these space charge, the discharge current build‐up becomes faster, the width of the discharge current becomes narrower, ion‐heating loss is reduced, and the effective electron temperature is optimized so that Xe atoms are excited more efficiently. The intensity of Xe 147‐nm radiation, dominant in low‐pressure Xe dis‐charges, saturates with respect to electron density due to plasma saturation. This determines the high end of the sustain pulse frequency.     

Driving large‐sized OLED TVs with an amorphous‐silicon backplane

Abstract— A 20‐in. OLED display driven by an amorphous‐silicon backplane has been demonstrated. It has been widely believed that the characteristics of amorphous‐silicon TFTs are not sufficient to drive OLED display. This paper challenges this hypothesis and proves that amorphous silicon can be applied to large active‐matrix‐driven displays and discusses many possible approaches that lead to good front‐of‐screen quality. Superior‐video‐image‐quality amorphous‐silicon‐driven OLEDs opens a bright future for a new generation of wall‐hanging televisions.     

A dipole‐type millimeter‐wave antenna with directional radiation characteristics

A dipole‐type millimeter‐wave (mm‐wave) antenna with directional radiation characteristics is presented. A radiating patch structure composed of a dipole‐type radiation patch and a rectangular‐shaped parasitic patch are initially investigated to achieve a wider bandwidth. To further improve the operating bandwidth and to realize a directional radiation characteristic, this radiating patch structure is top‐loaded above a conducting cavity‐backed ground structure, which has a low profile (thickness of 3 mm). The measured results show that the proposed mm‐wave antenna can achieve a wide 10‐dB bandwidth of 51.3% (29.6‐50.0 GHz) and stable gain across the desired frequency range. Furthermore, good directional characteristics over the entire mm‐wave frequency band with a compact antenna size of 0.64λ_40GHz × 0.91_λ40GHz × 0.43_λ40GHz are also realized. Hence, it is suitable for many small size wireless mm‐wave systems.     

Efficiency enhancement by employing the transistor nonlinear capacitors effects in a 6W hybrid X‐band Class‐J power amplifier

This article presents the design and fabrication of a 6 W X‐band hybrid Class‐J power amplifier (PA) based on a bare die GaN on SiC HEMT by accurate implementing the transistor nonlinear capacitor effects. The transistor input capacitor is precisely modelled and its nonlinearity effects on Class‐J performance is studied for the first time. It is shown that the harmonic generation property of the nonlinear input capacitor, especially at the second harmonic, can be of benefit to shape the transistor gate voltage as a quasi‐half wave sinusoidal waveform and consequently, it can improve the power added efficiency (PAE). A complete 3D thermal model of the power transistor is developed using ANSYS software and it is calibrated based on the thermal measured data. The PA achieves 13 dB average power gain over the frequency range of 8.8‐9.6 GHz. The drain efficiency and PAE are about 67% and 58% at 9.2 GHz, respectively.     

State‐space µ analysis for an experimental drive‐by‐wire vehicle

This paper considers the application of the skewed structured singular value to the robust stability of systems subject to strictly real parametric uncertainty. Three state‐space formulations that counteract the discontinuous nature of this problem are detailed. It is shown that the calculation of the supremum of the structured singular value over a frequency range using these formulations transforms into a single skewed structured singular value calculation. Similar to the structured singular value, the exact calculation of the skewed structured singular value is an NP‐hard problem. In this work, two efficient algorithms that determine upper and lower bounds on the skewed structured singular value are presented. These algorithms are critically assessed using a series of robustness analysis tests on a safety‐critical experimental drive‐by‐wire vehicle. Copyright © 2008 John Wiley & Sons, Ltd.     

High‐speed low‐voltage driving of high‐Xe‐content PDPs with priming particles

Abstract— Power savings, image‐quality improvement, and cost reduction are the major issues facing PDP development. High‐Xe‐content PDPs have attained improved luminous efficiency, but with sacrifices in higher switching and sustain voltages and slower discharge build‐up. By examining PDPs having 3.5%–30% Xe content, it was found that utilization of the space‐charge priming effect as well as wall‐charge accumulation are effective in obtaining a low operating voltage and a high switching speed. The improvements are enhanced for higher Xe pressures. By using space‐charge priming, the statistical time lag of the discharge triggering for the 30% Xe content is reduced significantly and becomes approximately equal to that of 3.5% Xe content. Once triggered, the formative time lag of the discharge becomes shorter and the space charge experiences diffusion/drift; hence, accumulation of the wall charge is faster for discharges with higher Xe contents. These indicate that the use of an erase addressing scheme, rather than a write addressing scheme, is preferable when driving high Xe‐content PDPs, because the erase addressing scheme provides the addressing operation with an abundant amount of priming particles. Also, the drive voltages are lower for the erase addressing scheme. In order to reduce the address voltage, it is effective to accumulate wall charges prior to addressing. It was found that there are limiting values for the charge accumulation, above which self‐erase discharges ignite and the wall charge is dissipated. The self‐erase discharge occurs at relatively low wall voltages when the Xe percentages becomes higher. The sustain pulse voltage can be reduced while keeping the luminous efficiency high by increasing the sustain pulse frequency. As the frequency is increased, a residual amount of space charge created by the preceding sustain pulse increases. Due to the priming effect of these space charge, the build‐up of the discharge current becomes faster, resulting in a lower voltage.     

Feasibility of driving PDPs with 1‐V data and 30‐V scan pulses by controlling the self‐erase‐discharge threshold

Abstract— In order to realize low‐voltage addressing of PDPs, an erase‐addressing scheme was adopted together with an accumulation of an appropriate amount of wall charge by using priming and bias pulses prior to addressing. The switching operation is performed by using sharp threshold characteristics of the self‐erase discharge. Cessation of the scan pulse ignites a weak self‐erase discharge, which, together with the data pulse, triggers an intense self‐erase discharge. By using the drive scheme, the data‐ and scan‐pulse voltages can be reduced to 1.1 and 29.6 V, respectively, provided that the panel has perfectly uniform voltage characteristics.     

Serial‐fed linear frequency diverse arrays for obtaining direction of arrival (DOA) of frequency modulated continuous waveform (FMCW) sources with ambiguity reduction

Possibility of exploiting serial‐fed linear arrays for obtaining the direction of arrival (DOA) of frequency modulated continuous waveform (FMCW) sources is discussed in this article. The angle of incident wave is assumed to be in the range, [?90°, 90°] , with ambiguity reduction compared with the previous work. At first, the serial‐fed arrays are assumed as a transmitter with triangular FMCW sources, composing modified frequency diverse arrays. An explicit angle dependency is obtained on the separations between the maximums of the produced spatial power pattern in a design procedure. The approach is generalized for modified sawtooth frequency modulated continuous waveform (SFMCW) sources, which are combinations of two SFMCW sources with two different slopes of frequency shifts. In addition, a measurement setup is implied assuming the serial‐fed array as the receiver and an antenna with a known FMCW source and an unknown DOA as the transmitter. The DOA will be obtained from the separations between maxima of the received signals. Advantages of the proposed structure are the simplicity of antenna structure, ability of operation with narrowband antenna elements, and ambiguity reduction compared with the previous work.     

Factors affecting the dynamics of a π‐cell (Invited Paper)

Abstract— The basic factors related to the dynamics of a π‐cell device are reviewed. Specifically, the director dynamics are studied for the case of a periodic drive voltage that is sometimes referred to as “impulse drive.” It is found for this type of drive waveform the desired bend state is more stable against the twisting effect of transverse electric fields found in AMLCD devices. This effect causes the reduction in light transmission due to “impulse drive” to be smaller in π‐cell devices than is expected to be found in other AMLCD modes.     

Analysis of the driving characteristics for an ACPDP with an auxiliary electrode using the voltage‐transfer closed surface

Abstract— The driving characteristics and wall‐charge model of an ac plasma‐display panel (ACPDP) with an auxiliary electrode were investigated by using voltage‐transfer closed‐surface modeling. To understand the wall‐charge behavior of an ACPDP with an auxiliary electrode qualitatively, voltage‐transfer closed‐surface analysis was applied to a test panel under the full driving waveform. The voltage‐transfer closed surfaces were obtained after the sustain, reset, and address periods, when the full‐stage driving waveform was employed with the test panel. As a result, it was proven that the wall‐charge model predicted in the previous work corresponded with the wall‐charge behavior of an ACPDP with an auxiliary electrode. Also, based on the resultant form after the address period, the wall‐charge model after the address period was recently added and the entire wall‐charge model was completed in this work. In addition, by investigating the trajectory of the cell‐state movement during the reset period, it was confirmed that the priming effect affected the reduced discharge time lag of an ACPDP with an auxiliary electrode under the newly proposed driving waveform for reducing address time lag.     

Dual‐band rotary standing‐wave voltage‐controlled oscillator

In this article, a dual‐band rotary standing‐wave oscillator (RSWO) is introduced that generates sinusoidal signals by the formation of a standing wave on a ring (closed‐loop)‐distributed composite right/left‐handed (CRL) Inductor‐Capacitor (LC) transmission line network. The LC network consists of four unit cells of CRL LC resonator stacked in series, and two pairs of cross‐coupled transistors are used to compensate for the loss of LC resonator. Varactors are used as the control to switch on/off the high‐ or low‐frequency bands. In the fundamental mode, the RSWO operates at the high‐frequency band. In the harmonic mode, the oscillator provides low‐frequency band outputs. The dual‐band function exploits the multiple oscillation modes of the CRL RSWO. The proposed RSWO has been implemented with the Taiwan Semiconductor Manufacturing Company, Limited (TSMC) 0.18‐μm SiGe BiCMOS technology. It can generate differential signals in the high‐band frequency range of 6.73–8.60 GHz and in the low‐band frequency range of 3.68–3.73 GHz. The die area of the RSWO is 1.123 × 1.123 mm². © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:536–543, 2014.