A wideband reflectarray antenna using single‐layer dipole element attached with T‐shaped stubs

A wideband reflectarray antenna consisting of single‐layer dipole element attached with T‐shaped stubs is proposed. By varying the lengths of the T‐shaped stubs, the unit cell can provide a linear phase curve covering about 420°. Critical design parameters are analyzed to understand its wideband operating mechanism. Using this novel type of unit cells, a 441 element 25° offset‐fed reflectarray with grid spacing of λ/3 at 10 GHz is designed, fabricated, and measured. The experimental results show that the proposed reflectarray can achieve 1‐dB gain bandwidth of 24% and 1.5‐dB gain bandwidth of 37%. In addition, aperture efficiency of 66.6% and cross polarization level of 29 dB are obtained at 10 GHz, respectively.     

A broadband wide‐incident‐angle reflective polarization converter

Abstract— A high‐performance reflective polarization converter which could be used in a backlight recycling system for liquid‐crystal‐display (LCD) devices is proposed. The device consists of a twisted‐nematic (TN) liquid‐crystal film, a uniaxial A‐plate, and a reflector. The configuration parameters, such as thickness and orientation of the films, are optimized using a genetic algorithm. As a result, the design can convert light from TM to TE polarization (or TE to TM) at a maximum 99.7%, minimum 91.3%, and average 96.7% conversion efficiency for the entire visible spectrum and incident angle from 0 to 60°. Such a broadband reflective polarization converter is particularly useful for enhancing the light efficiency and reducing the power consumption of LCDs.     

Development of 100‐in. TFT‐LCDs for HDTV and public‐information‐display applications

Abstract— LCDs have achieved a full‐high‐definition resolution of 1920 × 1080 (16:9), 600‐nit brightness, 3000:1 dynamic contrast ratio, 92% color gamut, 178° viewing angle, and 5‐msec response time at all gray levels and are targeted for HDTV and public‐information‐display applications. Some unique technologies, such as Cu bus line, advanced wide view polarizer, and wide‐color‐gamut lamp, were applied. A new stitching‐free technology was developed to overcome the size limitation of the photomask in both the TFT and color‐filter processes. The size of the panel (100 in.), based on the wide format (16:9), is determined by the maximum efficiency of the world's first seventh‐generation line (glass size, 1950 × 2250 mm) in LG.Philips LCD's (LPL) Paju display cluster. The issues facing 100‐in. TFT‐LCDs will be discussed.     

Design of a dual‐f‐number illumination system and its application to DMD™ projection displays

Abstract— A dual‐f/# optical system is evaluated and considered for illumination. Étendue theory has been employed to increase the optical throughput and collection efficiency. A classical Cooke triplet with a dual f/# is included for illustration. As a demonstration of the potential application to projection displays, an elliptically shaped illumination‐pupil system is proposed to increase the optical collection efficiency in the DMD? (Digital Micromirror Device?)‐based projection system. With a dual‐f/# configuration, this design can eliminate the f/2.4 constraint that was caused by the light‐steering action of the narrow ±12° tilt angles on the DMD?. The percentage of increase in the optical collection efficiency is 6.2% in the dual f/2.0 × f/2.4 optical projection system by using ray‐tracing simulation. This method enables a lower than f/2.4 optical design with a high brightness and an adequate contrast ratio in the DMD?‐based projectors.     

GaN‐based high‐output‐power blue laser diodes for display applications

Abstract— We succeeded in fabricating high‐output‐power blue (445 nm) laser diodes (LDs) with an output power of 500 mW. The operating current, voltage, and wall‐plug efficiency of these LDs were 480 mA, 4.8 V, and 21.7%, respectively. The lifetime of these LDs was estimated to be 10,000 hours under continuous‐wave operation at 25°C. From examination of the degradation mode, we found that the operating current seriously affects the lifetime of LDs. In the next stage, we will focuse on the optimization and sophistication of the manufacturing processes to fabricate longer‐lifetime (>30,000 hours) blue LDs.     

Green laser sources optimized for highly efficient microdisplay‐based field‐sequential mobile projectors

Abstract— A novel green laser source, based on a monolithic cavity microchip laser platform, has been developed. The laser is designed to be a part of a miniature and efficient RGB light source for microdisplay‐based mobile projector devices. The use of highly efficient, periodically poled MgO‐doped lithium niobate as the non‐linear frequency doubler allows for a significant increase in the overall efficiency of the green microchip laser. Specifically, a 50–150‐mW green output with a wall‐plug efficiency exceeding 10% in the temperature range of greater than 40°C has been demonstrated. A compact package for this laser source with a volume less than 0.33 cm³ is discussed and results of performance tests are presented.     

3‐D mobile display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel

Abstract— An autostereoscopic display based on dual‐directional light guides with a fast‐switching liquid‐crystal panel was designed and fabricated to provide better 3‐D perception with image qualities comparable to that of 2‐D displays. With two identical micro‐grooved light guides, each with a light‐controlled ability in one direction, two restricted viewing cones are formed to project pairs of parallax images to the viewer's respective eyes sequentially. Crosstalk of less than 10% located within ±8°–±30° and an LC response time of 7.1 msec for a 1.8‐in. LCD panel can yield acceptable 3‐D perceptions at viewing distance of 5.6–23 cm. Moreover, 2‐D/3‐D compatibility is provided in this module.     

Active‐matrix organic light‐emitting displays employing two thin‐film‐transistor a‐Si:H pixels on flexible stainless‐steel foil

Abstract— An active‐matrix organic light‐emitting diode (AMOLED) display driven by hydrogenated amorphous‐silicon thin‐film transistors (a‐Si:H TFTs) on flexible, stainless‐steel foil was demonstrated. The 2‐TFT voltage‐programmed pixel circuits were fabricated using a standard a‐Si:H process at maximum temperature of 280°C in a bottom‐gate staggered source‐drain geometry. The 70‐ppi monochrome display consists of (48 × 4) × 48 subpixels of 92 ×369 μm each, with an aperture ratio of 48%. The a‐Si:H TFT pixel circuits drive top‐emitting green electrophosphorescent OLEDs to a peak luminance of 2000 cd/m².     

A spoof surface plasmon leaky‐wave antenna with circular polarization

In this article a circularly polarized (CP) leaky‐wave antenna (LWA) based on spoof surface plasmon (SSP) is proposed. Corrugated circular patches are loaded on either side of the SSP waveguide periodically and asymmetrically, which enables continuous CP beam steering from backward to forward quadrant eliminating “the open stopband” at broadside. The antenna exhibits an impedance bandwidth of 43.5% (<?10 dB) and a 3‐dB axial‐ratio bandwidth of 27.8%; within the impedance bandwidth from 4.5 to 7 GHz the radiation beam can be steered from 120° to 70°. With a ground plane placed underneath, the antenna can achieve average radiation gain and efficiency of about 10 dBic and 84.2%, respectively, showing a radiation gain increase of about 3 dB over that without a ground plane. The proposed SSP‐based CP LWA is expected to find applications in wireless communication systems based on planar antennas.     

A 60‐GHz on‐chip slot‐array antenna in integrated‐passive‐device technology for antenna‐in‐package applications

A new millimeter‐wave antenna structure on a low‐cost, production platform integrated passive device technology is presented. The antenna consists of a 2‐by‐1 array of slot antennas at 60 GHz. An in‐house developed on‐chip antenna measurement setup was used to characterize the fabricated antenna. The measurement results show an antenna gain of more than 5 dBi with a return loss of 18 dB at 60 GHz. The better‐than‐10‐dB impedance bandwidth of the antenna covers the 60‐GHz unlicensed band from 57 to 64 GHz. The 3‐dB beamwidths of the antenna are 105° and 76° at E‐plane and H‐plane at 60 GHz, respectively. The size of the die of the antenna is 2 mm × 4.5 mm. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:155–160, 2014.     

Mode‐matching analysis of H‐plane ferrite‐loaded rectangular waveguide discontinuities

The full set of eigenmodes existing in a ferrite‐slab‐loaded rectangular waveguide is first obtained and then used to compute the scattering matrix of a junction between an air‐filled rectangular waveguide and an H‐plane ferrite‐slab‐loaded rectangular waveguide by using the mode‐matching method. Numerical results for the scattering parameters of the H‐plane waveguide discontinuity are compared to experimental data and those obtained by Ansoft's HFSS. Good agreement is observed. To demonstrate the usefulness of this structure, a computer‐optimized 90° nonreciprocal phase shifter is designed using an H‐plane ferrite‐slab‐loaded waveguide. With only one‐step impedance matching sections at both ends of the ferrite slab, a compact design is achieved to have 2° phase error and less than ?30 dB return loss over about 5% bandwidth. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 259–268, 2003.     

Low‐temperature‐applicable polymer‐stabilized blue‐phase liquid crystal and its Kerr effect

Abstract— A type of polymer‐stabilized blue‐phase liquid crystal, which can be used in a low‐temperature environment, is proposed. The blue‐phase range after polymerization was widened to more than 73°C, and the blue‐phase texture is very stable even at a temperature as low as ?35°C. The electro‐optical performances dependence on polymer concentration was investigated. The results indicate that the saturation voltage increases and the hysteresis enhances as the polymer concentration increases. The rise and decay times could reach as low as 391 and 789 μsec, respectively. Such material also shows good electro‐optical behavior at a temperature of ?35°C. In addition, the Kerr constant was tested under a uniformly distributed electric field to be 2.195 nm/V² at room temperature and 2.077 nm/V² at ?35°C. The Kerr constant tested under white‐light illumination was 1.975 nm/V², which shows a small dispersion.     

A viewing‐angle‐controllable blue‐phase liquid‐crystal display

Abstract— A viewing‐angle‐controllable liquid‐crystal display (LCD) is proposed. When the device is only driven by an in‐plane electric field, it exhibits a wide‐viewing‐angle (WVA) mode. And it exhibits narrow‐viewing‐angle (NVA) mode when it is driven by a vertical electric field as well as an in‐plane electric field. In this manner, the viewing angle of the device can be controlled from 100° to 30°. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

Broadband low‐profile transmitarray antenna using three‐dimensional cross dipole elements

This article presents a novel transmitarray antenna using three‐dimensional frequency selective structures as the radiating elements. The proposed unit cell, which consists of two cascaded cross dipoles, has a thickness of 0.22λ₀ and provides a 310° transmission phase range with transmission magnitude equal or better than ?0.8 dB. Compared with those conventional transmitarray antennas, the proposed one can realize greater flexibility in the installation with less manufacturing complexity. For the purpose of validation, a transmitarray prototype using the proposed elements has been manufactured and tested at X‐band. The peak gain of 25.5 dB is achieved at the frequency of 10 GHz, resulting in an aperture efficiency of 64%. Besides, antenna bandwidth of 10% for 1‐dB gain is achieved in this design.     

Invited Paper: Surface‐emitting‐diode lasers and laser arrays for displays

Abstract— High‐power red, green, and blue laser light sources made from vertically emitting arrays of intracavity doubled IR lasers is reported. The emitted infrared light from a monolithic array of large‐aperture vertical cavity lasers is converted into visible light using a PPLN doubling crystal in an external cavity. A volume Bragg grating provides simultaneous feedback for all emitters in the array and sets the laser wavelength. Increased diffraction losses for higher‐order modes result in quasi‐Gaussian beams with excellent conversion efficiency. Green 532‐nm lasers with more than 5.8‐W visible power have been demonstrated at a base temperature of 40°C. Blue 465‐nm lasers with 4.4‐W power at 40°C are unmatched in performance and wavelength when compared to competing GaN‐based edge emitters. Typical wall‐plug efficiencies are higher than 8%. We have measured single‐emitter operating lifetimes to be more than 28,000 hours. Red lasers based on highly strained InGaAs achieve record laser powers of 2.0W at 618 nm in the same form factor as the green and blue lasers. Red single‐emitter lifetimes of more than 10,000 hours have been attained. The technology described in this paper delivers on a full suite of cost efficient and reliable red, green, and blue lasers that meet the demands of the display markets.     

Microstrip tapered traveling wave antenna for wide range of beam scanning in X‐ and Ku‐bands

In this work, a broadband traveling wave antenna (TWA) is presented as a microstrip design that is capable of a wide range of beam scanning by changing the operation frequency within 8 to 14 GHz. For this purpose, a rhombus shaped microstrip patch is used as a unit element and TWA is built as a tapered microstrip line consisting of the cascaded rhombus shaped unit elements and terminated by a rectangular antenna instead of traditional resistive termination which can be called patch loaded traveling wave antenna (PLTWA). Optimization and simulation of the PLTWA is carried out using 3‐D Microwave simulation software CST and its dimensions are resulted as 130 × 30 mm. From the simulations, it should be noted that the patch termination increases the maximum gain almost 3 dB and the total efficiency up to 90% compared to the traditional resistive load over the operation band at the expanse of a small distortion on S₁₁ characteristics. Then the PLTWA is fabricated and measured along its operation band 8 to 14 GHz and it exhibits a peak gain of 9.5 dBi at 11 GHz. The measured gain of the proposed antenna is found between 9 dB and 12 dB and its beam direction is steerable with the range of 80° (?65°‐15°) over the operation band 8 to 14°GHz.     

High‐efficiency leaky‐wave antenna with continuous wide‐angle scanning using hybrid composite right/left handed structure

A hybrid composite right/left handed (CRLH) structure based leaky‐wave antenna with continuous wide beam scanning is proposed in this article. Six series‐wound periodic units, combining spoof surface plasmon polariton (SSPP) with CRLH, form the radiating portion of proposed antenna. The unit is connected to the ground with metal hole, which provides the equivalent parallel inductance, and the unit is separated from its adjacent unit at prescheduled intervals, which provides the equivalent series capacitance. Additionally, the unit operates at balanced state and the open stopband is obviously suppressed. Dispersion diagram is also used to analyze this continuous scanning. A prototype of proposed antenna is fabricated and measured. The main beam of the antenna scans continuously from ?70° to +40° in the range from 5.2 to 8.8 GHz. The antenna radiation efficiency reaches a maximum of 92% in the working band. Measurement results agree quite well with the simulation, which indicate this leaky wave antenna can find potential applications in communication systems and radars.     

Amorphous‐silicon thin‐film transistor on soda‐lime glass

Abstract— Amorphous‐silicon (a‐Si:H) thin‐film transistors (TFTs) on soda‐lime glass were fabricated by using a diffusion barrier and a low‐temperature process at 200°C. The silicon nitride barrier was optimized in terms of diffusion blocking effectiveness, film adhesion, and surface finish. TFTs on soda‐lime glass achieved a saturation mobility 0.47 cm²/V‐sec, threshold voltage of 0 V, an off‐current of 7.7×10^?11 A, and a sub‐threshold swing of 1.0 V/dec. From diffusion experiments, a 30,000‐hour lifetime for the TFT device at 80°C was estimated, and the robustness of the silicon nitride barrier against long‐term migration of sodium was demonstrated.     

Novel wideband metal‐only transmitarray antenna based on 1‐bit polarization rotation element

In this article, a novel wideband metal‐only transmitarray based on 1‐bit polarization rotation element is proposed. First, a novel wideband polarization rotation element is designed, which consists of four metallic layers without any substrate layers. The element can be used to rotate polarization of the transmission wave by 90° with respect to that of the incident wave. The element and its mirror image can provide 0° and 180° phase shifts with 1‐bit phase quantization in the 9.2 to 11.2 GHz band with more than 80% polarization conversion rate. Then, by using the proposed element, a 21 × 21‐element transmitarray with a standard pyramidal horn feed is designed and fabricated. The measured results show that the transmitarray achieves 16.8% 1‐dB gain bandwidth with a peak gain of 21.6 dBi. Its cross‐polarization and side‐lobe levels are below ?20 and ?10 dB, respectively, in the operating band. The measured results agree well with the simulation ones, validating effectiveness of the transmitarray design method.     

Tilted bi‐sense circularly‐polarized antenna and its application for radio frequency identification system

A tilted bi‐sense circularly polarized (CP) antenna and its application for UHF radio frequency identification (RFID) system is proposed. A planar concial monopole working as the electric dipole is designed at first. When a shorting pin is added, a loop radiator would be generated, and thus a pair of orthogonally oriented complementary dipoles is realized. In this way, both right‐handed circularly polarized (RHCP) and left‐handed circularly polarized waves (LHCP) are generated simultaneously in tilted directions within one hemisphere. Then, closed‐form formulas are derived to reveal the tunability mechanism of bi‐sense property and provide a design guideline for system application. It is demonstrated that flare angle of conical monopole has a linear relationship and sine function to CP beam direction and 3‐dB axial ratio (AR) beamwidth, respectively. Finally, antenna prototypes are fabricated and tested for validation. It is also demonstrated that at the tilted direction of θ = ± 45°, a 3‐dB AR bandwidth of 4.9%, and gain up to 5 dB are realized. Comparing with conventional microstrip patch antenna, an enhanced reading range over 5 m can be obtained in the tilted range from 40° to 75° and ? 75° to ?40° in UHF RFID sytem application.