Designing unity magnitude input shaping by using PWM technique

This paper proposes a method for reducing vibrations in flexible systems by using the input shaping. A new input shaper technique based on Pulse Width Modulation (PWM) is used to shape the input.Since unity magnitude (UM) input shaping is easy to implement and provides less control duration, it has been preferred for many application areas. An analytical solution to time locations of the UM shaper requires very complex mathematical expressions due to involving in dependent constraint equations. This paper presents a simple PWM based input shaping method. The proposed technique allows designing UM shapers without analytical solution especially for the shapers having higher order impulse sequence. The method requires only the estimated value of system natural frequency and damping ratio. Desired numbers of impulses can be obtained by comparing reference signal amplitude and carrier wave frequency of a PWM. Analysis and experimental results demonstrate the effectiveness of the proposed method.     

被动毫米波焦面阵成像技术

以安全检查为背景,研究了近距离被动毫米波焦面阵成像的关键技术.其中包括采用基模高斯波束法结合几何光学法分析系统准光路;设计多波束宽角扫描透镜天线;提出一种新型结构的介质棒天线,该天线易于排成紧密阵列且能够为透镜提供良好的照射;研制工作于Ka频段的高灵敏度、小型化直接检波式辐射计等.给出了20通道被动毫米波焦面阵成像系统...     

A Comparison of Propagation Between Apertured Bessel and Gaussian beams

A true Bessel beam is a family of diffraction-free beams. Thus the most interesting and attractive characteristic of such beam is non-diffracting propagation. In optics, the comparisons of maximum propagation distance had been done between Bessel and Gaussian beams by Durnin and Sprangle, respectively. However, the results obtained by them are conflict due to the difference between their criteria. Because Bessel beams have many potential applications in millimeter wave bands, therefore, it is necessary and significant that the comparison is carried out at these bands. A new contrast criterion at millimeter wavelengths is proposed in our paper. Under this criterion, the numerical results are presented and a new conclusion is drawn.     

Modelling a millimeter wave harmonic power combiner by a hybrid field analysis technique

A dual-diode millimeter wave harmonic power combiner in which two radial line transformers are used is modelled by a field analysis technique based on Galerkin's method combined with collocation technique. The external circuit impedances looking outside from each of two active devices are computed at both fundamental frequencies and the second harmonic frequencies. Numerical results of the impedances with respect to various structural parameters are presented. Some important characteristics of the harmonic power combiner are revealed. A number of useful conclusions have been deduced for practical design and adjustment.     

Fast and robust control of systems with multiple flexible modes

This paper derives shaped time-optimal servomechanism (STOS) closed-loop control laws using a phase-plane approach to address flexible structures having multiple flexible modes. The STOS control laws for systems having two and three flexible modes are detailed. The flexible modes are addressed by using multimode input shapers to shape the time-optimal control for the rigid body portion of the system. The altered rigid body phase-plane trajectories resulting from this shaping are solved and used to determine an STOS closed-loop controller. Both "convolution" and "simultaneous" method multimode input shapers are considered. We also improve the robustness to modeling errors of the STOS control. The more robust zero vibration and derivative (ZVD) shaper is used. The ZVD shaper consists of more impulses and has a longer time duration than the simpler zero vibration (ZV) shaper which leads to the more robust STOS (RSTOS) control derived from the ZVD shaper having more switches and longer time response than the STOS control derived from the ZV shaper. Simulation results show that using the ZVD shaper in deriving the RSTOS control improves the robustness to modeling errors in frequency and damping of the flexible mode.     

Millimeter-wave Receiver Optics for Korean VLBI Network

Over the past several years the millimeter wave VLBI (Very Long Baseline Interferometry) observations have been intensively performed. However phase fluctuation due to troposphere is one of the key issue in terms of degradation of sensitivity and limits imaging capability in millimeter wave VLBI observations. We describe the details of designed receiver optics for the Korean VLBI Network to calibrate tropospheric phase fluctuation for the millimeter wave VLBI observation. These optics guide beams from one position on sky to 22, 43, 86, and 129 GHz-band receivers simultaneously. Several topics, such as the design principles of imaging and power loss due to phase errors on common ellipsoidal mirrors are discussed.     

Quasioptical Polarizer Based on Self-Complementary Sub-Wavelength Hole Arrays

In this letter, extraordinary transmission in sub-wavelength hole arrays is employed in combination with self-complementary Babinet concepts to design a novel class of quasioptical polarizer for millimeter wave frequencies. After a proper design, the device has been miniaturized in such a way that operation under Fresnel zone of a Gaussian beam has been demonstrated. Experimental validation opens up the way to new possibilities for polarizer design.     

Priority shaping of traffic streams sharing a policed virtual path in an ATM network

Traffic streams with differing service requirements, sharing a single contract for use of a policed virtual path in an ATM network, may be jointly shaped to make the best use of bandwidth available in the path. The shaper may use the information about the network policer to perform self-policing with a form of priority service to ensure satisfactory levels of cell loss and delay for both real-time and non-real-time traffic. Two such shapers are considered assuming a mean bit-rate contract with the network in which a leaky-bucket mechanism performs the policing function. The performance of the shapers is analysed using Markov-modulated models of bursty traffic sources and stochastic fluid methods, and the analytical results are corroborated by simulations. The choice of the shaper type and optimization of the shaper design parameters are discussed using correlated and non-correlated source models.     

Design of High-Performance Millimeter Wave and Sub-Millimeter Wave Quasi-Optical Isolators and Circulators

Faraday rotators using permanently magnetized ferrite materials are used to make quasi-optical isolators and circulators at millimeter wave and sub-millimeter wave frequencies that have far higher performance than their waveguide equivalents. This paper demonstrates state-of-the-art performance for four-port quasi-optical circulators with 60-dB isolation, 0.2-dB insertion loss, and better than 80-dB return loss for devices centered at 94 GHz. A method is presented for the accurate characterization of the complex permeability and permittivity of permanently magnetized ferrites via a series of frequency and polarization dependent transmission and reflection measurements. The dielectric and magnetic parameters for the sample are determined by fitting theoretical curves to the measured data. These fitted parameters are then used in a model for a complete quasi-optical Faraday rotator, including matching layers, allowing the accurate design and fabrication of these devices for any specific operational frequency band in the millimeter wave and sub-millimeter wave regime. Examples are given showing typical results and demonstrating how temperature cycling can significantly improve the temperature stability of these devices, while allowing fine tuning of the center frequency. We also indicate the performance possible at higher frequencies to above 1 THz and outline performance of truly planar isolators where lossy polarizer material is built into the Faraday rotator matching structure     

High speed semiconductor laser design and performance

The design of semiconductor lasers for efficient response to direct current modulation at microwave and millimeter wave frequencies is described. A rate equation analysis is used to relate the effect of current modulation on laser intensity and frequency. This analysis is also used to relate the 0, 3 and 6 dB frequencies to the peak frequency and to predict the maximum bandwidth obtainable in a single longitudinal mode laser. The design of structures and packaging for millimeter wave bandwidths is also described.     

Design guidelines and comparison of detector readout front end integrated S-G shapers using transconductance circuits

An analysis of readout front end electronics semi-gaussian (S-G) shapers is carried out. Innovative design methodology is proposed and an advanced filter design technique based on operational transconductance amplifiers (OTA) is used, in order to implement fully integrated structures. Three respective novel CMOS shaper topologies are designed and compared in terms of noise performance, total harmonic distortion, dynamic range and power consumption as to examine which is the most preferable in readout applications. Analysis is supported by simulations results using SPICE in a 0.6?µm process by the Austria Mikro Systeme (AMS). The optimum implementation appears to be the OTA based cascade shaper structure with the inductor simulation. The specific shaper implementation is used in a fully integrated preamplifier-shaper system for a space application silicon strip detector of 2?pF capacitance. The readout system achieves an equivalent noise charge of 327 electrons at 1.7?µs peaking time in ?40°C.     

A Future Millimeter/Sub–Millimeter Radiometer for Satellite Observation of Ice Clouds

The instrument concept of a future spaceborne millimeter/sub-millimeter radiometer is proposed in this paper for the remote sensing of ice clouds from satellite. The proposed radiometer is expected to operate at a series of frequencies within the millimeter and sub-millimeter wave range from 150 to about 900 GHz. Five frequencies are selected in the atmospheric windows, i.e., 150, 220, 463, 683, 874 GHz, and at each frequency there are two orthogonally polarized channels. Three water vapor channels located close to 183.31 GHz are also included in this instrument, since they can provide water vapor information, which is needed for ice cloud parameter retrieval. To simplify system design and test, a modular design philosophy is followed in the receiver frontend design and two antennas are used separately for the millimeter and sub-millimeter channels. Overall, the instrument requirements can be met with today's technology, except for the channels at the highest frequencies, where the radiometric sensitivity can be larger than the required 1.0 K for the 10 km spatial resolution (2.5 ms integration time). However, this situation can be improved by averaging neighboring pixels in data processing if certain compromise in the spatial resolution can be made at these frequencies.     

A novel noncontacting waveguide backshort for submillimeter wave frequencies

A novel noncontacting waveguide backshort has been developed for millimeter wave and submillimeter wave frequencies. It employs a metallic bar with rectangular or circular holes. The size and spacing of the holes are adjusted to provide a periodic variation of the guide impedance on the correct length scale to give a large reflection of rf power. This design is mechanically rugged and can be readily fabricated for high submillimeter wave frequencies where conventional backshorts are difficult or impossible to fabricate. Model experiments have been performed at 4 GHz – 6 GHz to empirically optimize the design parameters. Values of reflected power greater than 95% over a 30% bandwidth have been achieved. A specific design is presented which has also been successfully scaled to WR-10 band (75 GHz – 110 GHz). A theoretical analysis is compared to the experiments and found to agree well with the measured data.     

W波段带状注速调管电子光学系统的研究进展

带状注速调管以其在毫米波段可获得高功率和高增益输出,以及小型化、紧凑型、平面微加工成形等的技术优势而备受国际前沿领域广泛关注。本文重点给出了正在开展的W波段带状注速调管的研究工作,通过采用均匀场聚焦的带状电子注的方式,研制出了椭圆截面带状电子注成形与传输的束流样管。通过实验测试获得的电子枪压缩和成形的带状电子注截面为10 mm×0.7 mm,且在电子注电压为20~82 kV,电流0.5~4.27 A时,长度为100 mm的漂移通道内电子注传输的直流通过率达到98%以上,从而验证了采用均匀场传输带状注的方案是完全可行的。     

Investigations on optically controlled millimeter wave Gunn oscillators

There is a growing interest in optically controlled millimeter wave oscillators. In this paper, we have investigated the external-circuit impedances of an optically controlled millimeter wave subharmonic Gunn diode oscillator, which is illuminated by GaAs/GaAlAs laser beam. The variation of the external-circuit impedances looking outward from the Gunn diode with respect to the optical injection plasma density are calculated based on a field analysis method. The results give some useful conclusions for optically controlled millimeter wave Gunn diode oscillator design. Experimentally an optical tuning frequency shift of 7MHz is achieved at W-band.     

Optically Controlled Broadband Millimeter Wave Beam-Splitter-Type Coupler

Recently, Laser-controlled four-port beam-splitter-type couplers with photoinduced plasma layer and band-limited coupling characteristics at millimeter wave frequencies have been proposed for use in dielectric and image guides and circuits. In order to achieve a large dynamic range regarding the optical control of the coupling coefficient narrowband destructive interference in the dark state has been used. In this paper an ultra-broadband coupler for applications at millimeter wave band is proposed. This configuration requires waveguides to be transparent for the optical excitation. Numerical examples for the lowest order modes are presented and discussed considering fused quartz for the dielectric strips of the guides and a 50 μm GaAs film for the active layer.     

Injection Locked Millimeter Wave Oscillators at Ka, V, and W-Bands

Injection locked Gunn oscillators have been developed to amplify the upconverted millimeter wave frequencies. They are being used in millimeter wave communication systems at Ka, V and W-Bands respectively.     

A RF window for broadband millimeter wave tubes

The equivalent circuit and design method for a RF window in millimeter wave band are presented. Computation and experiment show that matching band of the RF window is wider. It can be used as output window for broadband millimeter wave tubes.     

W 波段回旋行波管双阳极磁控注入电子枪的设计

回旋行波管是大功率、高频率的微波毫米波器件。根据W波段回旋行波管的要求,设计了双阳级磁控注入电子枪。由电子光学理论,计算得到电子枪的初始参量,然后利用粒子模拟软件MAGIC构造电子枪模型,分析电子枪各个参数对电子注性能的影响,为电子枪设计优化提供了一定的依据。最后优化得到符合设计要求的低速度零散电子枪结构。电子枪阳极电压为70kV,电流10A,电子注速比1.07,电子注横向速度零散0.8%。     

Electromagnetic analysis of beam-scanning antenna at millimeter-wave band based on photoconductivity using Fresnel-zone-plate technique

The proposed antenna is a Fresnel-zone-plate antenna (FZPA) in the Ka band that scans the beam of millimeter wave source. The antenna includes a semiconductor wafer (silicon, gallium arsenide) in which a spatially varying density of charge carriers is selectively established through selective optical illumination using a pulse laser. It is shown that the beam of the antenna can be scanned through the space by reconfiguring the masking of the wafer. The beam scanning is done in the transmission mode. The analysis of the far-zone radiation characteristics is presented using physical optics. Results for the antenna gain, the efficiency, and the co- and cross-polar patterns are given.