Cheol Sig Pyo

A Circular Polarized Metallic Patch Antenna for RFID Reader

A novel single feed circularly polarized metallic patch antenna for RFID reader is proposed. The proposed antenna has a simple structure, it has corner truncated square patch, ground plane and a probe feed. In addition to structure of the proposed antenna is simple and low cost. Experimental results of a constructed prototype with the center operating frequency at 911 MHz showed that the antenna has an impedance bandwidth (2:1 VSWR) of about 23 MHz, a 3 dB axial ratio of about 9 MHz, and a gain level of about 9 dBi

A NEW TYPE OF WIDEBAND SLOT-FED U-SLOTTED PATCH ANTENNA

A slot-fed U-slotted patch antenna is de eloped as an aperture-coupling structure, and is compared to the existing feed types. Its wideband mechanism is explained, and its samples for Kuand S-bands are designed, simulated, and tested. A bandwidth of about 42% for VSWR less than 2:1; and 30.1% for y3 dB peak gain are obtained. Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22:

Design of Steerable Linear and Planar Array Geometry with Non-uniform Spacing for Side-Lobe Reduction

In this paper, we present a noble pattern synthesis method of linear and planar array antennas, with non-uniform spacing, for simultaneous reduction of their side-lobe level and pattern distortion during beam steering. In the case of linear array, the Gauss-Newton method is applied to adjust the positions of elements, providing an optimal linear array in the sense of side-lobe level and pattern distortion. In the case of planar array, the concept of thinned array combined with non-uniformly spaced array is applied to obtain an optimal two dimensional (2-D) planar array structure under some constraints. The optimized non-uniformly spaced linear array is extended to the 2-D planar array structure, and it is used as an initial planar array geometry. Next, we further modify the initial 2-D planar array geometry with the aid of thinned array theory in order to reduce the maximum side-lobe level. This is implemented by a genetic algorithm under some constraints, minimizing the maximum side-lobe level of the 2-D planar array. It is shown that the proposed method can significantly reduce the pattern distortion as well as the side-lobe level, although the beam direction is scanned.

RF performance and effect of calibration in smart antenna system

This work presents the RF performance and effect of phase and amplitude error calibration in a smart antenna system based on WCDMA. We focus on the design and implementation of the RF subsystem and suggest a phase and amplitude error calibration method for the smart antenna system. The RF subsystem consists of an 8-element array antenna, RF front-end, high power amplifier, RF transceiver, digital IF transceiver, and the digital calibration unit which can support switched and adaptive beamforming simultaneously. Experimental results are shown for RF performance and we propose phase and amplitude error calibration at the analog part which can mitigate the amount of DSP in the digital calibration unit.

RF integrated aperture coupled antenna for satellite communication at Ku-band

An active microstrip patch antenna in, which a high power MMIC amplifier is integrated behind the ground plane of the antenna, is presented, to obtain extra power gain and reduce losses at Ku band. The patch antenna, integrated with the HPA MMIC, has an aperture-coupled feeding structure. The advantages of this structure lie in the reduction of power loss in the feed line and spurious effects from the active circuit and feeding network. The 2/spl times/2 array antenna, integrated with the HPA MMIC, obtains an extra gain of 14 dB at 14.3 GHz. The beamwidth of the active array antenna is about 8% wider than that of a passive array antenna.

Hybrid Sensor Module and Data Processing Using Low-Power Wakeup in WSN

Due to the development and proliferation of ubiquitous technologies and services, various sensor network applications are being appeared on the stage. The needs for algorithms requiring complex signal processing with a high-performance processor such as digital signal processor are also increased. However, it is difficult to use such processor for the low-power sensor network operating with a battery because of power consumption. This paper proposes and implements hardware and software architecture of the hybrid-type sensor module composed of a low-power sensor module and a high-performance sensor module for the complicated signal processing in the wireless sensor node. Although this approach needs some additional hardware, it results in some improvements in operation time supporting complex algorithms for target detection in the sensor networks.

The Access Control Model in Ubiquitous Sensor Network Environment

With the increasing need for intelligent environment monitoring applications and the decreasing cost of manufacturing sensor devices, it is likely that a wide variety of sensor networks will be deployed in the near future. In this environment, the way to access heterogeneous sensor networks and the way to integrate various sensor data are very important. The COSMOS is a kind of USN middleware that plays a central service platform part in USN service environment. The COSMOS provides its own services (sensor network abstraction query processing, etc) using multiple heterogeneous sensor networks to the various USN applications. Multiple applications share USN middleware services with other USN applications. Therefore, access control to COSMOS is very important for the applications which shares USN middleware services. This paper introduces the access control model which is implemented in COSMOS to control multiple applications’ access to COSMOS.

WISE: web of object architecture on IoT environment for smart home and building energy management

Fog computing extends cloud-based computing concept to the edge of the network, thus enabling a breed of services and applications. Previous research topics on fog computing have significantly focused on the concepts and fundamentals of fog computing and its importance in the context of Internet of things (IoT) and Web of object (WoO). Recently, inspired by IoT and WoO, the era of connecting all the things and people is coming. Unfortunately, various devices and objects in IoT environments hardly show the method for automatic connection and the cooperation applied to IoT applications and services. Firstly, in this paper we propose WoO based on the architecture which contains various devices and objects for providing Web base IoT services and applications. Secondly, various service overlay network concepts for providing mashup by service federation and composition are introduced. Also, we describe service deployment architecture over smart home IoT architecture on fog computing environment. Thirdly, we propose a new architecture for selecting optimal objects or things attributed from the metadata, resource and profiles by our WoO-based smart building energy prediction methodology.

EC-MAC: A Cross-Layer Communication Protocol for Dynamic Collaboration in Sensor Networks

In numerous sensor network applications, a group of nodes surrounding an event (forming an active region) must collaborate to collect locally generated data, reliably and efficiently. Active regions are often characterized by intense data transfer, packet collisions and congestion, resulting in significant network performance loss. Previous studies dealt these scenarios either at the application or network layers, where potential performance gains at the MAC layer were not considered. In this paper, a cross-layer communication protocol Event-Centric MAC (EC-MAC) is introduced in which the channel access time is divided into two intervals. During slot reservation interval, all nodes within an active region collaborate to construct a Transmit/Receive schedule on-the-fly. Once the schedule is in place, data forwarding is performed during the data transmission interval towards a designated root node. By allowing contention-free channel access, EC-MAC outperforms fully awake and LPL-based MAC protocols in terms of both energy efficiency and data throughput.

Data traffic based route selection for real-time data delivery in wireless sensor networks

Surveillance and reconnaissance applications such as military in wireless sensor networks require timely transfer of important data (i.e., the detection of enemy troops and vehicles) to a remote base station or sink node. Unfortunately, picking up the reliable routing path to deliver the data in realtime is difficult because of various interferences, often environmental changes, and so on. Thus, routing protocols based on the link quality to select the routing path are affected by those kinds of factors. In this paper, we propose a reliable routing mechanism that provides real-time transfer of the important data. In other words, we provide the weighted link quality metric that reflect the TX/RX traffic flow to select the reliable route over the routing path. Moreover, we also provide a cross-layer routing protocol design in order to reduce the data queue processing time and to send out the priority data at both network and MAC layer.