Phase Shift Technology Research Articles

Research on Course Radius Measurement for Vertical Petroleum Tank Volume Metrology Based on 3D Laser Scan Principle

One course radius measurement method for vertical petroleum tank volume metrology based on 3D laser scan principle was researched. Method of distance measurement by laser phase-shift technology and angular measurement by optical grating was applied to acquire coordinates of points in each course under the control of servo system. The permitted error of measured point location is 2mm. Fitting algorithms base on direct iterative method (DIM) and least square method (LSM) were used to process measured data and deduce equivalent radius of each course. In comparison experiment, one 1000m3 vertical tank was used as test object. Compared to strapping method (international mandatory standard), the maximal deviation radius value of method discussed is 2.8mm. The maximal difference of radius value calculated by DIM and LSM is 0.1mm. The experimental results verified the method discussed in this paper.

OCDMA En/Decoders Employing Multiple $\pi$ Equivalent Phase Shifts

Based on the equivalent phase shift (EPS) technology, the optical code-division multiple access (OCDMA) en/decoders employing multiple pi-EPSs have been studied both numerically and experimentally, which demonstrate good en/decoding performances. It is also shown that the insertion of multiple pi-EPSs offers a new degree of freedom for OCDMA security, in which the multiple pi -EPSs decoder is completely unmatched with single pi-EPSs encoder even if they have the same code sequence.

Improvement for optical mechanics method of coherent gradient sensing

Coherent gradient sensing (CGS) is double grating lateral-shearing interferometric technique with the simplicity of the optical set-up, non-contact, real-time, full-field optical information and variable resolution, which has shown many applications in the study of quasi-static as well as dynamic crack-tip field in both homogeneous and composite materials. It can be used both in a reflection mode (for opaque materials) and in a transmission mode (for transparent materials). The accuracy of the fringe order in the CGS interference image will deeply influence the precision of experimental study. Because of the difference in the optical principle from other optical methods, the fringe order of CGS cannot be obtained through the phase-shift technology. In this paper, a kind of modified CGS method is introduced and analyzed, which can accurately obtain the fringe order of random position in the CGS interference image. This method does not need additional optical set-up and complicated image processing techniques, but only needs several (greater than two) CGS interference images under different loadings. Static fracture experiments show that this method can evidently improve the precision of the CGS method.

A ZVS Bidirectional DC–DC Converter With Phase-Shift Plus PWM Control Scheme

The current-voltage-fed bidirectional dc-dc converter, which refers to a current-fed inverter at low voltage side and a voltage-fed inverter at high voltage side, can realize zero voltage switching (ZVS) for the switches with the use of phase-shift (PS) technology. However, the current-fed switches suffer from high voltage spike and high circulating conduction loss. In order to solve these problems, a novel phase-shift plus pulsewidth modulation (PSP) control ZVS bidirectional dc-dc converter is proposed in this paper. By adopting active clamping branch and PSP technology, the converter can realize ZVS for all switches in a wide range of load variation while input or output voltage varies. In addition, a novel control strategy with one port voltage regulation and another port current regulation is proposed to make energy bidirectional conversion freely. The operation principle is analyzed and verified by a 28 V/270 V conversion prototype rated at 1.5 kW.

Investigation of Ferroelectric Thick-Film Varactors for Microwave Phase Shifters

This paper presents a novel cost-effective microwave phase-shifter technology using thick-film ferroelectric varactors as the tuning component. The devices are fabricated by conventional screen-printing techniques with silver/platinum as the conducting layers and Ba <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7 </sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as the tunable dielectric layer. The microwave performance of the ferroelectric varactors is optimized in terms of both material process parameters and the varactor gate area dimensions. S-parameter measurements on a tunable reflective circuit are used to evaluate the performance of the varactor at around 2 GHz. The varactor parameters such as RF capacitance, tunability, and the Q factor of the varactor are studied as a function of the gate dimension. At 100-V dc-biasing voltage, the BSTO varactor loaded tunable reflective circuit exhibits a differential phase shift of 70deg with a return loss of -1.2 dB. This is equal to a figure-of-merit value of 58deg/dB. Full analog reflection-type and all-pass network phase shifters are also implemented in order to explore the monolithic integration of phase control devices into the RF system based on low-cost ceramic thick-film technology

Photorefractive crystal-based holographic interferometry system for full-field wave propagation metrology

Although, photorefractive materials have been discovered for many years, research using pulsed laser as the light source and photorefractive material as the recording media to record a pulsed laser hologram have been scarce despite its vast application potential. A newly proposed optical configuration which adopts a Nd:YAG pulsed laser of 532nm wavelength as the light source and uses an iron-doped lithium niobate crystal as the recording media for holographic recording of an un-deformed specimen is presented. Real-time holographic interferometry was achieved by inducing repetitive impacts on the specimen through a precise piezoelectric impact hammer. With timing control better than microseconds, several interferograms created at each instance were obtained with each corresponding 9ns laser pulse. A five-step phase-shifting technology, median filter algorithm, and weighted iterative DFT phase unwrap algorithm were integrated to reconstruct the deformation information at each instance. Using a series of measured deformation data, surface wave propagation phenomenon on the specimen could be observed. Some of the potential applications for this newly developed pulsed laser holographic interferometry system are detailed.

Modification of Coherent Gradient Sensing (CGS) to Accurately Get the Fringe Order

In this paper, a novel optical method, namely, Coherent Gradient Sensing (CGS) is used to study the fracture properties of IR window materials in the guidance missile. CGS can produce high contrast fringes and provide some degree of control on the sensitivity of measurement during experiment. It is highly attractive for solid mechanics applications, especially to new materials, such as IR window materials. But the accuracy of the fringe order in the CGS interference image will deeply influence the precision of experiment. Because of the different optical principle from other method, the fringe order of CGS can’t be obtained through the phase-shift technology. To satisfy the precision request of IR window materials, a kind of modified CGS method, loading CGS method is introduced and analyzed, which can accurately obtain the fringe order of random position in the CGS interference image. This method doesn’t need additional optical set-up and complicated image processing techniques, but only need two CGS interference images under different loading. Static fracture experiments of ZnS show that this method can evidently improve the precision of the CGS method.

Focus on photonics and imaging

Focus on photonics and imaging

Study on Method of Ultrasonic Gas Temperature Measure Based on FPGA

It is always a problem to measure instantaneous temperature of high-temperature and high-pressure gas. There is difficulty for the conventional method of measuring temperature to measure quickly and exactly, and the measuring precision is low, the ability of anti-jamming is bad, etc. So the article introduces a method of measuring burning gas temperature using ultrasonic based on Field-Programmable Gate Array (FPGA). The mathematic model of measuring temperature is built with the relation of velocity of ultrasonic transmitting and gas Kelvin in the ideal gas. The temperature can be figured out by measuring the difference of ultrasonic frequency δf. FPGA is introduced and a high-precision data acquisition system based on digital phase-shift technology is designed. The feasibility of proposed above is confirmed more by measuring pressure of burning gas timely. Experimental result demonstrates that the error is less than 12.. and the precision is heightened to 0.8%.

Improvement of measurement error for modified coherent gradient sensing

Recently, a novel optical method, coherent gradient sensing (CGS), has been widely used in the study of deformation near crack tips under quasi-static and dynamic conditions, which can produce high contrast fringes and provide some degree of control on the sensitivity of measurement during experiment. It involves a simple optical set-up and is relatively insensitive to vibrations and rigid body motions. Like other interferometries, such as electronic speckle pattern interferometry, moiré method, etc, the accuracy of the fringe order in the CGS interference image will deeply influence the precision of experimental study. But because of the different optical principle, the fringe order of CGS cannot be obtained through the phase-shift technology. In this paper, a modified CGS method is introduced and analysed, which can accurately obtain the fringe order of a random position in the CGS interference image. The modified CGS method needs two original CGS optical set-ups, and can be used in static and dynamic conditions, which requires no complicated image processing techniques. Static fracture experiments on mode-I crack in homogeneous materials show that this modified method can evidently improve the measurement precision of the CGS method.

Digital phase-shifting atomic force microscope Moiré method

In this study, the digital atomic force microscope (AFM) Moiré method with phase-shifting technology is established to measure the in-plane displacement and strain fields. The Moiré pattern is generated by the interference between the specimen grating and the virtual reference grating formed by digital image processes. The overlapped image is filtered by two-dimensional wavelet transformation to obtain the clear interference Moiré patterns. The four-step phase-shifting method is realized by translating the phase of the virtual reference grating from 0 to 2π. The principle of the digital AFM Moiré method and the phase-shifting technology are described in detail. Experimental results show that this method is convenient to use and efficient in realizing the microscale measurement.

MEMS 2-Bit Phase-Shifter Failure Mode and Reliability Considerations for Large&amp;gt;tex&amp;lt;$X$&amp;gt;/tex&amp;lt;-Band Arrays

RF microelectromechanical systems (MEMS) switch technology used in the fabrication of phase-shifter circuits is examined from the perspective of failure mode and reliability implications on the performance of large X-band array antennas. Amplitude and phase-state failure probability density functions (pdfs) conditioned on switch probability of failure are formulated for both the hybrid-T (switched line) and coupled-line phase-shifter circuit topologies. The pdfs are used to assess the phase-shifter failure impact on overall array level performance in terms of gain loss and the increase in RMS sidelobe level. Reliability and lifetime implications are addressed through considering a probability of switch failure that increases with cycling. The phase-shifter lifetime switching considerations are related to radar system lifetime beam switching requirements consistent with plausible radar system applications. The key findings are that RF MEMS switch mean time to failure /spl sim/125000 h or longer, consistent with /spl sim/100-125 phase-shifter state switches per second (/spl sim/10/sup 11/ switch operations), are reasonable expectations for RF MEMS phase-shifter technology to meet in order to be considered viable for a broad range of array antenna applications.

Optical imaging properties of dense phase shift feature patterns

Optical lithography resolution enhancement methods are continuing to develop, driven by the semiconductor industry’s requirements for imaging subwavelength feature sizes. In the phase shift area, pattern decomposition into multiple exposures has been found to be useful and is finding its way into production. Recently, layout construction based on dense fine-pattern imaging has received increasing interest. This type of approach can minimize the proximity and other spatial frequency effects that otherwise limit strong phase shift technologies. Simple fine-feature template masks are easier and cheaper to fabricate and inspect as well as offering the potential to be reused for multiple designs. In this article, imaging and process issues specific to dense phase shift patterns are explored both experimentally and through simulation. Progress is reported in applying our gratings of regular arrays and trim exposures for ultralarge scale integrated circuit lithography (GRATEFUL) imaging method to fine features in both x and y orientations. The use of a graytone trim mask to vary fine-feature dimensions in a dual-exposure, strong phase shift process has been explored. We have also studied multiple-exposure lithography using one mask and varying illumination between exposures.

A 2 million transistor digital processor with 120 nm gates fabricated by 248 nm wavelength phase shift technology

Alternating phase shift technology has been shown to substantially improve focus latitude and resolution for several years. However, the use of phase shift masks to improve the process latitude in gate level lithography has been hindered by the lack of commercially available tools that can convert conventional gate layouts into phase shift mask patterns. A software package has recently become available that allows a user to create phase shift masks to reduce the gate length of features in existing circuit layouts. A digital signal processing chip with 2 million gates has been used as a test vehicle to evaluate the feasibility of phase shifting and processing a large number of devices in a complete circuit. Three wafer lots have been processed with a target feature size of 120 nm with a variation of 25 nm 3σ. The timing circuits of the chips have been tested; those with 120 nm gates showed a nearly fourfold improvement in speed when compared to 240 nm gate circuits at 1 volt operation.

Evaluating voltage-tunable materials for RF phase shifter technology

Today's phased-array antennas use hundreds of radiating elements that use relatively high-loss phase shifters that operate over a limited bandwidth. The number of elements and the phase shifter losses affect the overall cost of the antenna system. Ferroelectric RF phase shifters have the potential to meet the low-loss, low-cost requirements driving many phased-array applications. Some of the issues affecting the development of ferroelectric phase shifters include ferroelectric tunability, dielectric losses, conductor losses, and impedance mismatch. We used the measured tunability (250 kHz, room temperature), dielectric constant, and loss tangent (10 GHz, room temperature) of Ba1-xSrx/TiO3 (0.4x 0.6) with various amounts of MgO additive, 0 to 60 wt.%, to estimate the device performance of microstrip phase shifters. The electromagnetic model of the microstrip (which uses a standard 3-mil-wide 1-oz. copper line, 3-mil-thick BST/MgO composite and the bias criteria of 2 V/μm) has produced performance benchmarks for a number of composites providing 360° of phase shift. While the accuracy of the electromagnetic model used to evaluate these materials has limitations, the results do provide some insight as to which materials may be better suited for 10-GHz phase shift devices.

Analysis of 3-D surface waviness on standard artifacts by retroreflective metrology

Retroreflective metrology has been used to measure the 3-D surface waviness on standard artifacts. An optical configuration was constructed for the measurement, in which the grating image is produced by projection. The three-step algorithm of phase-shifting technology was applied to analyze the image. Two standard artifacts with 8.0- and 16.0-µm peak-to-peak wave amplitudes were tested. The experiments show that retroreflective metrology can successfully recover the contour and amplitude of the surface waviness on the standard artifacts. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)02101-2]

Calculation of energy deposition in thin resist films over multilayer substrates

Multilayer substrates are of great importance for direct write applications. Recently, they are getting more and more importance in mask making as well, for example in the phase shift technology. In the case of direct writing, the substrate consists of various layers of different materials while for mask fabrication, the mask plate consists of at least two different layers, e.g. Cr on glass. A new method for the calculation of energy deposition due to e-beam exposure in thin resist films over composite substrates is presented. The method is based on the solution of the Boltzmann transport equation and has proven to be very fast compared to Monte Carlo method, and its accuracy has been shown by successful comparison with experimental obtained results. The method is incorporated in a complete e-beam lithography simulator.

Fabrication of 0.2 μm gate pseudomorphic inverted HEMT by phase-shifting technology

A phase-shifter edge line (PEL) mask method is applied to the gate fabrication process of InGaAs AlGaAs pseudomorphic inverted high electron mobility transistors (HEMTs). In phase-shifting technologies, the PEL mask method suits forming a fine line pattern owing to its high resolution. Mushroom shaped 0.2 μm gate pseudomorphic inverted HEMTs fabricated by using the PEL mask method show high d.c. and r.f. performances. As one of the applications of the 0.2 μm gate pseudomorphic inverted HEMTs, a decision circuit IC for 10 Gb/s optical communication systems is successfully fabricated.

Imaging Characteristics of Multi-Phase-Shifting and Halftone Phase-Shifting Masks

Phase-shifting masks and imaging characteristics are discussed and compared with those of conventional transmission masks. Then, new phase-shifting masks with intermediate values of phase shifting or transmittance are proposed, and their imaging characteristics are investigated. A phase-shifting mask with a 90° phase difference can ease the restrictions on pattern geometries used in phase-shifting technology but does not increase the focus latitude. It is also suggested that a halftone phase-shifting mask is suitable for printing isolated patterns and it gives wider focus latitude than conventional mask technology.

Optical lithography using phase-shifting technology

Optical lithography using phase-shifting technology