Design of a Novel Bandpass Filter in Millimeter-Wave Band

In this paper, a novel Bandpass Filter (BPF) combining microstrip parallel-coupled with end-coupled resonators is proposed. The filter not only allows the cross coupling to be realized but also makes itself compactness. At 35GHz, such a filter is designed and experimental results are discussed.     

一种改进的双边带调制产生光毫米波的方案

提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明,下行链路信号通过光纤能传输50km而不需要色散补偿,功率代价小于1dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。     

Photon Generation Scheme of 32-Fold Millimeter-Wave Signal Based on Mach-Zehnder Modulator

This paper proposes a 32-tupling frequency millimeter-wave (MMW) filter-free system based on four Mach-Zehnder Modulators (MZM) connected in parallel and cascaded with a simple radio-fiber (RoF) link structure. The four MZMs are all at the maximum transmission point (MATP), and the radio frequency (RF) driving voltage phase difference between MZMs is π /2. The center carrier is suppressed by using an optical attenuator (OATT) and an optical phase shifter (OPS). Two parallel MZMs can generate ±8th order and ±12th order optical sidebands, and the ±4th order optical sidebands can be suppressed by adjusting the modulation index m of the MZM, using cascaded two dual-parallel MZMS(DPMZM) and the phase difference of the RF signal source is π/4 to generate ±16th order optical sidebands. The theoretical analysis and simulation experiments are performed for the scheme proposed in this paper. The results show that the simulated and theoretical values of the optical sideband suppression ratio (OSSR) for ±16th order optical sideband signals are 60.02 and 59.96 dB, respectively, and the simulated and theoretical values of the RF sideband suppression ratio (RFSSR) for the 32-tupling MMW signal are 56.34 and 53.94 dB, respectively.     

A Novel Parallel-Series Feeding Network of Microstrip Patch Arrays with Composite Right/Left-Handed Transmission Line for Millimeter Wave Applications*

A novel parallel-series feeding network of microstrip patch arrays with composite right/left-handed transmission line (CRLH-TL) for millimeter wave applications is proposed. Since there is no inserting phase shift in the patch elements with CRLH-TL feeding structure, the inherent pattern shift resulting from the traditional parallel-series feeding network is removed. Besides, because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feeding network.* Supported by the National Natural Science Foundation of China (No. 60371010) and (No. 60471037)     

A Simple Closed-form Formula for Backward-Wave Start-Oscillation Condition for Millimeter-Wave Helix TWTs

An accurate and simple closed-form formula, for backward-wave start-oscillation condition for a millimeter-wave helix traveling-wave tube amplifier was developed, using an artificial neural network (ANN) algorithm. The analysis considers the effects of circuit loss and also the variation of electron beam diameter corresponding to beam filling. The formula is simple and amenable to easy computation, even using a scientific calculator, and without resorting to exhaustive numerical iterative search followed in conventional analyses and, at the same time, without sacrificing the accuracy in results. The formula was validated against published results, and excellent accuracy was observed. The analysis has been further used for inferring some physical interpretations on the effects of beam-filling factor and circuit loss on the start-oscillation condition of a typical millimeter-wave helix traveling-wave tube.     

A Novel Millimeter-Wave Power Combining Circuit

This paper presents the analysis and design of a novel millimeter-wave power combining circuit. This combing circuit is composed of a new style 3-dB combiner, which achieves low-loss, wide-band, and symmetric power division. Different from conventional Wilkinson hybrid, the proposed combiner requires no isolating resistor, and is easier fabricated and more suitable for millimeter integrate circuits. Analytical and experimental work on a two-way combining circuit with wave-guide ports in Ka-band shows the combiner has an insertion loss of 0.2dB, and a power-combining efficiency above 80% in 32–33GHz is obtained.     

A Full-Height Waveguide to Thin-Film Microstrip Transition with Exceptional RF Bandwidth and Coupling Efficiency

We describe a waveguide to thin-film microstrip transition for high-performance submillimetre wave and teraherz applications. The proposed constant-radius probe couples thin-film microstrip line, to full-height rectangular waveguide with better than 99% efficiency (VSWR 1.20) and 45% fractional bandwidth. Extensive HFSS simulations, backed by scale-model measurements, are presented in the paper. By selecting the substrate material and probe radius, any real impedance between 15-60 can be achieved. The radial probe gives significantly improved performance over other designs discussed in the literature. Although our primary application is submillimetre wave superconducting mixers, we show that membrane techniques should allow broad-band waveguide components to be constructed for the THz frequency range.     

一种改进的生成四倍频光毫米波的传输方案

针对光载无线通信系统中并联双驱动马赫-曾德尔调制器(MZM)的四倍频方案产生功率周期性衰落效应,以及传输距离短的不足,提出了一种改进的抑制双边带调制产生光毫米波方案。首先在并联MZM后用波分复用(WDM)分离抑制双边带信号的两个边带,将基带信号调制到下边带,再与未调信号耦合后产生光毫米波,最后传输至加入前置补偿的光纤链路中。用optisystem7.0软件对改进方案进行了仿真,结果表明用此类结构不仅能得到高纯度的四倍频光毫米波,还可以消除上述的效应,实现了更长距离、更佳性能的传输。     

A Novel Reconfiguration CPW Leaky-Wave Antenna for Millimeter-Wave Application

A novel reconfigurable millimeter-wave leaky-wave antenna is proposed according to the radiation characteristics of periodically loaded coplanar waveguide and simulated by the finite-difference time-domain method. The simulated results demonstrate that the single main beam of this antenna operating at 35.0GHz can scan with small steps in the E-plane from –90° to 90° except the angle around 0°. The main beam scanning is obtained by the antenna structure reconfiguration with nine discrete states controlled by embedded switches and two feed ports. The antenna is useful for millimeter-wave applications.     

A New Dielectric Grating Antenna with Large Leakage Constant for Millimeter-Wave Applications

The leakage properties of a new dielectric grating leaky wave antenna are carefully examined by an approach of combining the multimode network theory with the mode-matching method. A systematic comparison is given for the leaky characteristics of the n = −1 space harmonic of TM mode polarization between the present antenna and the traditional one. It has been found that the former is not only of lower conductor loss, but also of larger leakage constant than the latter. As a result, the dimension of the antenna could be largely reduced, which is of practical significance for some applications. Extensive numerical results of the radiation characteristics are given to establish useful guidelines for the design of the new grating antenna. Furthermore, special features such as cancellation or resonance effects are high-lighted and discussed. Physical insights for the mathematical findings are also presented.     

Transition metal dichalcogenides (TMDCs) heterostructures: Optoelectric properties

Transition metal dichalcogenides (TMDCs) have suitable and adjustable band gaps, high carrier mobility and yield. Layered TMDCs have attracted great attention due to the structure diversity, stable existence in normal temperature environment and the band gap corresponding to wavelength between infrared and visible region. The ultra-thin, flat, almost defect-free surface, excellent mechanical flexibility and chemical stability provide convenient conditions for the construction of different types of TMDCs heterojunctions. The optoelectric properties of heterojunctions based on TMDCs materials are summarized in this review. Special electronic band structures of TMDCs heterojunctions lead to excellent optoelectric properties. The emitter, p-n diodes, photodetectors and photosensitive devices based on TMDCs heterojunction materials show excellent performance. These devices provide a prototype for the design and development of future high-performance optoelectric devices.     

Spin Transition Molecular Materials: New Sensors

This short review article concerns a new family of iron(II) spin transition chain compounds containing 4-R-1,2,4-triazole derivatives whose properties have been followed by several physical techniques. A clear evidence of the LIESST effect at 20 K has been found for one of these materials by ⁵⁷Fe Mössbauer spectroscopy. Potential applications in terms of pressure and thermal sensors are discussed.     

Novel Broadband Reflectarray Antenna with Windmill-Shaped Elements for Millimeter-Wave Application

A novel broadband millimeter-wave reflectarray antenna composed of windmill-shaped elements of variable lengths is proposed. Compared to the conventional single-layer reflectarray elements, the windmill-shaped elements can realize much larger phase variation range (over 600°), leading to broader bandwidth. Using this technique, a 15°-beam-steering reflectarray operating at 30 GHz is designed. The computed results demonstrate the agreement of the main beam steering with the design requirement, and a 1-dB gain bandwidth close to 20% is obtained. The validity of the obtained results is verified by comparing the ones generated by Ansoft High Frequency Structure Simulator (HFSS) with those produced by Ansoft Designer. The antenna is useful for millimeter-wave applications. This work was supported by the National Natural Science Foundation of China (No. 90505001), the High-Tech Research and Development Program of China (No. 2006AA01Z275), and the Creative Research Group Program of UESTC.     

Transition region where the large-scale and very large scale motions coexist in atmospheric surface layer: wind tunnel investigation

The turbulent structures in atmospheric surface layer (ASL) are investigated in wind tunnel with hot-wire anemometers in present study. The results show that there exist two typical turbulent structures characterised by their streamwise length scales, i.e. large-scale motions (LSMs) and very large scale motions (VLSMs) as reported recently in pipe flow, channel flow, zero-pressure-gradient turbulent boundary layers and near-neutral ASLs. Moreover, a transition region containing both LSMs and VLSMs is first reported in present investigation, and this region depends on the Reynolds numbers. In the transition region, as the wall-normal distance increases, the turbulent energy ratio of LSMs is gradually weakened but VSLMs strengthened.     

Design of Cylindrical Conformal Millimeter-Wave Microstrip Antennas with Broad Beamwidth

This paper describes the design of a novel cylindrical millimeter-wave microstrip antenna (MA) with broad beamwidth by means of isotropic transformation (IT). A planar millimeter-wave antenna with broad beamwidth is designed first, and then IT is used to design a conformal one based on the planar structure. In addition, phased array with eight present elements has been designed as an example. Finally, numerical results are given to show that the present antenna possesses broad beamwidth and its array is of large scanning angle, which also verify the validity of the method of IT.     

Support Vector Regression Model for Millimeter Wave Transitions

In this paper, we introduce a new method, support vector regression (SVR) method, to model millimeter wave transitions. SVR is based on the structural risk minimization (SRM) principle, which leads to good generalization ability for regression problem. The SVR model can be electromagnetically developed with a set of training data and testing data which produced by the electromagnetic simulation. Two Ka-band millimeter wave transitions, i.e., waveguide to microstrip transition and coaxial to waveguide adapter, are used as examples to validate the method. Experimental results show that the developed SVR models have a good predictive ability, and they are useful for interactive CAD of millimeter wave transitions.     

Metallic Nanocrystallites-Coated Piezoelectric Quartz for Applications in Gas Sensing

This article reports the gas-sensing capability of nanocrystalline (NC) transition metal-coated piezoelectric quartz crystal (PQC). NC transition metal particles of Pd and Ag with particles size of 10–15 nm, while Pt and Au are 20–25 nm are used. The NC particles deposited on the quartz substrate adsorbs gaseous pollutants, thereby increasing the weight of the quartz substrate and decreasing its vibration frequency. We have found that transition metals, Pd, Pt, Au, and Ag in particular, show good sensitivity for NH₃-detection; the maximum frequency change occurs at 150°C for Pd and Pt and at 100°C for Au and Ag. The NC Pd- and NC Pt-coated PQC also show good sensitivity for CO₂-detection at 150°C. Likewise, the NC Au-coated PQC shows very good sensitivity for NO₂-detection but at a higher temperature (180^°C). The frequency change as a function of the pollutant gas concentration ( f-curve) follows the Langmuir adsorption isotherm (unimolecular adsorption) except in the case of NC Pd-coated PQC under NH₃ and NC Au-coated PQC under NO₂. The f-curve for the NC Pd-coated PQC is convex with respect to the NH₃ concentration axis. The f-curve for the NC Au-coated PQC is convex in the low NO₂ concentration region, and concave in the high NO₂ concentration region. Both curves indicate multi-molecular adsorption, Type III and Type V adsorption, respectively. Therefore, the good sensitivity and stability of these gas sensors can be attributed to physical adsorption of the pollutant gases as a result of van der Waals attraction.     

Low-Power Testing of Losses in Millimeter-Wave Transmission Lines for High-Power Applications

We report the measurement of small losses in transmission line (TL) components intended for high-power millimeter-wave applications. Measurements were made using two different low-power techniques: a coherent technique using a vector network analyzer (VNA) and an incoherent technique using a radiometer. The measured loss in a 140 GHz 12.7 mm diameter TL system, consisting of 1.7 m of circular corrugated waveguide and three miter bends, is dominated by the miter bend loss. The measured loss was 0.3 ± 0.1 dB per miter bend using a VNA; and 0.22 ± 0.1 dB per miter bend using a radiometer. Good agreement between the two measurement techniques implies that both are useful for measuring small losses. To verify the methodology, the VNA technique was employed to measure the extremely small transmission loss in a 170 GHz ITER prototype TL system consisting of three lengths of 1 m, 63.5 mm diameter, circular corrugated waveguide and two miter bends. The measured loss of 0.05 ± 0.02 dB per miter bend may be compared with the theoretical loss of 0.027 dB per miter bend. These results suggest that low-power testing of TL losses, utilizing a small, simple TL system and a VNA, is a reliable method for evaluating performance of low-loss millimeter-wave TL components intended for use in high-power applications.     

一个新型的毫米波无线信号光纤传输系统及本振信号远程传送结构

摘要提出一个新型的毫米波光纤传输系统及本振信号远程传送的结构.此技术能为将来使用皮蜂窝网络提供宽带无线接入服务给出一个简单的基站接入点解决方案.计算和仿真结果表明,在激光器输出功率为－6.5 dBm,光放大增益为6 dB,激光线宽为1 MHz,75 MHz或150 MHz,误码率不超过10－9的情形下,622 Mbit/s的下行相移键控信号能够在传统单模光纤上传输超过30 km的距离.在具有相对大的激光器线宽150 MHz和光纤距离为30 km时,由激光器相位噪音和光纤色散所引起的（通过远程传送的）毫米波本振信号的额外相位误差的方差仅为1.74°.