An X-band high-efficiency MMIC power amplifier with 20-dBreturn losses

Describes the design principles and measured performance of an X-band high-efficiency monolithic-microwave-integrated-circuit (MMIC) power amplifier and discuss pertinent factors of the ion-implantation process. Also presented is a worst-case power prediction of the chip performance and a large-signal design using small-signal simulation. This balanced amplifier is fully monolithic with input and output return losses of better than 20 dB provided by Lange couplers. These return losses make it very convenient to cascade with other components. For high-efficiency operation, the drain voltage is 6 V. Across the 40% bandwidth from 8 to 12 GHz, the amplifier produces 1.6 to 2.1 W of output power at 33 to 40% power-added efficiency. For high-power operation, the drain voltage is 8.5 V. The amplifier can produce 2.4 to 2.8 W of output power at 26 to 29% power-added efficiency across the same 40% bandwidth     

Compact Circularly Polarized Antenna with a Capacitive Feed for GPS/GLONASS Applications

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual‐feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are 28 mm × 28 mm × 4 mm, which is the most compact size among the dual‐band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).     

Reverse link capacity analysis of a CDMA cellular system with mixedcell sizes

The demands for mobile communication services are growing rapidly. In heavily populated areas, cell splits are unavoidable to increase the capacity of the cellular system. Cell splitting makes a cellular system have mixed cell sizes. For cell planning, it is necessary to analyze the reverse link capacity of a code-division multiple-access (CDMA) cellular system with mixed cell sizes. In this paper, we propose a method to calculate the reverse link capacity of a CDMA cellular system with mixed cell sizes. When a macro cell is split into three micro cells, as an example, we calculate the reverse link capacities for the three micro cells and the neighboring macro cells. The results show that as the radius of a micro cell decreases, the reverse link capacity of the micro cell increases, while those of the neighboring macro cells decrease     

Systematic Generation of Current-Mode Linear Transformation Filters Based on Multiple Output CCIIs

A transformation called current-mode linear transformation (CMLT) and its filter applications using multiple output second-generation current conveyors (MOCCIIs) are presented. The systematic method is developed to realize CMLT MOCCII-based filters efficiently. Based on the proposed design tables, we can synthesize high-order current-mode all-pole and elliptic filters with MOCCIIs, grounded resistors and capacitors. Moreover, the high-frequency elliptic filter can also be efficiently realized by adding capacitors to the relative all-pole filter, although floating capacitors are needed. Third-order Chebychev and elliptic lowpass filters are described in this paper. Experimental results that confirm the theoretical analysis are obtained. Furthermore, the proposed circuits can be extended to higher-order filters.     

Classification of pixels in a noisy grayscale image of polar ice

Often, in synthetic aperture radar (SAR) images of polar ice, one encounters shadow-like features across the images. Such features make it difficult to classify pixels into ice and water. Accordingly, it becomes a challenge to determine the true size and boundaries of ice floes in an SAR image of polar ice. We develop a simple statistical procedure which classifies pixels of an image by eliminating the effects of shadow-like features. Methodology developed in this paper is illustrated using some noisy SAR images of ice floes in the Arctic sea.     

Content Protective Multi‐Agent Platform for MsMu Service and Pattern‐Based Content Management

Recent research on mobile Internet protocol television and digital right management (DRM) interconnections has focused on multimedia technologies designed to enhance content scalability and adaptive content distribution. However, due to the architectural and scalable limitations, recent systems are not flexible and securable with respect to their adaptive content distribution and protective policy management. Therefore, we propose a content protective multi‐agent platform that provides secure multimedia services, correlation management, pattern‐based management, and multisource multi‐use (MsMu)‐based services. Our architecture, supported by DRM, lets us create a rich set of MsMu‐based content protection and seamless multimedia services through the extension of one source multi‐use (OsMu)‐based content services. We have verified our platform, which provides scalable and securable services with a 17% lower service response time by using a testbed.     

Adaptive random access and resource allocation scheme based on traffic load in HiperLAN type2 system

The MAC protocol of HiperLAN type2 is based on TDMA/TDD and provides access control and resource allocation schemes. We propose a scheme that provides adaptive random access and efficient resource allocation according to the traffic load for HiperLAN type2, by using access probability. The analysis and simulation results show that the proposed scheme performs better than the conventional scheme and supports priority services easily.     

Performance Analysis on Coexistence of EDCA and Legacy DCF Stations in IEEE 802.11 Wireless LANs

The distributed coordination function (DCF) scheme of IEEE 802.11 MAC protocol does not support any concepts of quality of service (QoS) but the enhanced distributed channel access (EDCA) scheme in IEEE 802.11e standard provides QoS according to access categories using different access parameters. However, the legacy DCF stations may be used together with EDCA stations. In this letter, we investigate and analyze the performance discrimination when EDCA and DCF stations operate simultaneously     

Excellent Switching Uniformity of Cu-Doped $hbox{MoO}_{x}/hbox{GdO}_{x}$ Bilayer for Nonvolatile Memory Applications

We have investigated a Cu-doped MoO_x/GdO_x bilayer film for nonvolatile memory applications. By adopting an ultrathin GdO_x layer, we obtained excellent device characteristics such as resistance ratio of three orders of magnitude, uniform distribution of set and reset voltages, switching endurance up to 10⁴ cycles, and ten years of data retention at 85degC. By adopting bilayer films of Cu-doped MoO_x/GdO_x, a local filament was formed by a two-step process. Improved memory characteristics can be explained by the formation of nanoscale local filament in the ultrathin GdO_x layer.