Surface wave excitation from open microstrip discontinuities

Radiation properties of open microstrip discontinuities are investigated using a full-wave integral equation technique. Formulas are presented to characterize power loss from open microstrip discontinuities. The technique utilizes microstrip current distributions obtained with the method of moments. The formulas allow the separation of total loss into the individual contributions of space wave and surface wave radiation and indicate the direction in which surface wave power is propagating within the substrate. Patterns depicting the power propagating in the substrate have been computed and verified experimentally     

双音和WCDMA调制阻塞的有效IM2分量评估

引言近年来随着第3代(3G)无线网络在日本(IMT-2000)、欧洲(UMIST)和美国(CDMA2000)的推广,3G移动手机所需的低成本、低功耗和小形状系数的用户设备(UE)变得重要起来。采用硅工艺、电路设计技术实现的直接下变频接收结构是3G手机高集成平台的一种有前途的系统方案。本文给出3G无线电的商业用全集成零中频接收机方案(图1)。广泛讨论接收机输入2阶截点(IIP2),因为它是直接变频接收机的关键性能指标。在此给出测量、仿真和计算结果。直接变频接收机结构如图1所示,直接变频或零中频接收机结构是实现接收机完全片上集成的途经,直接解调信…     

Millimeter-wave double-dipole antennas for high-gain integratedreflector illumination

A double-dipole antenna backed by a ground plane has been fabricated for submillimeter wavelengths. The double-dipole antenna is integrated on a thin dielectric membrane with a planar detector at its center. Measured feed patterns at 246 GHz agree well with theory and demonstrate a rotationally symmetric pattern with high coupling efficiency to Gaussian beams. The input impedance is around 50 Ω and will match well to a Schottky diode or SIS detector. The double-dipole antenna served as the feed for a small machined parabolic reflector. The integrated reflector had a measured gain of 37 dB at 119 μm. This makes the double-dipole antenna ideally suited as a feed for high-resolution tracking or for long-focal-length Cassegrain antenna systems     

Millimeter-wave integrated-horn antennas. I. Theory

The far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane are calculated using full-wave analysis. The solution is based on the numerical evaluation of the pertinent Green's function for the horn structure and the application of the method of moments. The convergence characteristics of the full-wave analysis method are investigated, along the the resonant properties of the strip-dipole and the corresponding behavior of the far-field patterns     

Millimeter-wave integrated-horn antenna. II. Experiment

For pt.I see ibid., vol.39, no.11, p.1575-81 (1991). The impedance and radiation patterns of a dipole-fed horn antenna in a ground plane are experimentally investigated at microwave and millimeter-wave frequencies. The agreement with the full-wave analysis technique presented in part I is good. The results indicate that for a 70° flare-angle horn, horn apertures from 1.0 λ-square to 1.5 λ-square with dipole positions between 0.36 and 0.55 λ yield good radiation patterns with a gain of 10-13 dB a cross-polarization level lower than -20 dB, and resonant dipole impedances between 40 Ω and 120 Ω. It is also found that the impedance measurements can be safely used for 2-D horn arrays, but the radiation patterns differ because of the Floquet modes associated with the array environment. The integrated horn antenna is a high-efficiency antenna suitable for applications in millimeter-wave imaging systems, remote-sensing, and radioastronomy     

Performance Analysis on Network-Based Distributed Mobility Management

Recently, various efforts from both industry and academia are being performed on specifying distributed mobility management (DMM). One of the early and promising network-based DMM proposals is dynamic mobility anchoring (DMA). This paper carries out a performance analysis on DMA in terms of mobility costs and handover performance, comparing it with proxy mobile IPv6 (PMIPv6). For the cost analysis, we consider signaling, processing, data packet delivery, and tunneling costs. For the handover analysis, we consider handover latency, handover failure probability, and handover packet loss as performance metrics. The impacts of several parameters on the mobility costs and handover performance are investigated. The results show that DMA outperforms PMIPv6 significantly in optimizing the network resources consumption as well as the mobility management performance.     

Integrated horn antennas for millimeter-wave applications

The development of integrated horn antennas since their introduction in 1987 is reviewed. The integrated horn is fabricated by suspending a dipole antenna, on a thin dielectric membrane, in a pyramidal cavity etched in silicon. Recent progress has resulted in optimized low- and high-gain designs, with single and double polarization for remote-sensing and communication applications. A full-wave analysis technique has resulted in an integrated antenna with performance comparable to that of waveguide-fed corrugated-horn antennas. The integrated horn design can be extended to large arrays, for imaging and phased-array applications, while leaving plenty of room for the RF and IF processing circuitry. Theoretical and experimental results at microwave frequencies and at 90 GHz, 240 GHz, and 802 GHz are presented     

Freeze-thaw degradation of FRP-concrete interface: Impact on cohesive fracture response

Results from an experimental investigation into the influence of freeze-thaw action on the FRP-concrete interface fracture properties are presented. The FRP-concrete bond behavior is investigated using a direct shear test. The cohesive stress transfer between FRP and concrete during debonding is determined from spatially continuous measurements of surface strains obtained at different stages of the debonding load response. The non-linear material law for the interface shear fracture, which provides a relation between the interface shear stress as a function of relative slip between the FRP and concrete, is established for specimens subjected to different levels of damage associated with freezing and thawing action. The influence of freeze-thaw action on the cohesive stress transfer during crack propagation, and on the cohesive interface fracture parameters is evaluated using a statistical hypothesis testing method. A larger percentage decrease in the interface fracture energy due to freeze-thaw cycles compared to the corresponding decrease in the ultimate nominal stress at debonding was noted. A decrease in the length of the cohesive stress transfer zone and the maximum interface cohesive stress were also observed with freeze-thaw cycling.     

Experimental Investigation and Fracture Analysis of Debonding between Concrete and FRP Sheets

The last few years have witnessed a wide use of externally bonded fiber reinforced polymer (FRP) sheets for strengthening existing reinforced and prestressed concrete structures. The success of this strengthening method relies on the effectiveness of the load-transfer between the concrete and the FRP. Understanding the stress transfer and the failure of the concrete–FRP interface is essential for assessing the structural performance of strengthened beams and for evaluating the strength gain. This paper describes an experimental investigation of the interfacial bond behavior between concrete and FRP. The strain distributions in concrete and FRP are determined using an optical technique known as digital image correlation. The results confirm that the debonding process can be described in terms of crack propagation through the interface between concrete and FRP. The data obtained from the analysis of digital images was used to determine the interfacial material behavior for the concrete–FRP interface (stress versus relative displacement response) and the fracture parameter GF (fracture energy). The instability in the test response at failure is shown to be the result of snapback, which corresponds with the elastic unloading of the FRP as the load carrying ability of the interface decreases with increasing slip.