Thin Transmitarray Panel with full 360-degree Phase Shift Range

This paper presents a new design technique to reduce the thickness of the transmitarray (TA) panel while maintaining 360 o phase shift range. Two types of unit cells, the receive-transmit unit cell and the frequency selective surface (FSS) unit cell, are placed in the same aperture. Comparing to the existing ultra-thin TA designs of similar panel thickness, the presented TAs do not suffer from the phase quantization loss and achieve better aperture efficiency. This study proves that it is viable to mix different types of TA unit cells to design a TA. The developed TA shows better gain than a homogeneous TA using the same elements and improved the overall efficiency by 60%. To verify the design concept, one TA with central frequency at 13.3 GHz was designed, fabricated and measured. The measured gain is 21.3 dBi and the calculated aperture efficiency of the TA is 37.9%

A Low-Cost Radar Absorber Based on Palm Shell Active Carbon for Anechoic Chamber

Synthesis and characterization of a low-cost Radar Absorber Material (RAM) based on palm shells activated carbon is presented in this work. This low-cost RAM is intended to be used to cover the walls of the anechoic chamber. Palm shells are industrial waste from oil palm plantations and are widely available in West Sumatra. This work aims to investigate the characteristics of RAM based on palm shell for various types of an activating agent. In addition, the characteristics of RAM are also investigated due to the effect of the concentration of the activating agent. In this research, HCl, KOH, H3PO4, and ZnCl2 are operated to activate carbon of palm shell by opening the carbon pores. Characterization of the active carbon in term of absorption and morphological on the surface is performed by using a Vector Network Analysis (VNA) and a Scanning Electron Microscopy (SEM). The waveguide technique is operated in the investigation of the absorption of electromagnetic waves of the RAM on the C-band operating frequency (4 to 8 GHz). The measured results present the maximum absorption of the RAM is obtained -26.3 dB at a frequency of 8 GHz and 1M KOH activating agent. The morphological on the RAM surface shows the pore size of activated carbon on a 1M activating agent preferable than 5M and non-activated carbon. Based on the measurement result, the activated carbon of the palm shell can be used as the radar absorber material for the anechoic chamber application

PENGOLAHAN CITRA SATELIT ALOS PALSAR MENGGUNAKAN METODE POLARIMETRI UNTUK KLASIFIKASI LAHAN WILAYAH KOTA PADANG

The image processing of Alos PalSAR satellite data level 1.1 for land classification in Padang City is described in this work.  The full polarimetry method is adopted in classification process which can receive and process all combinations of the four polarizations of HH, HV, VH, and VV. Yamaguchi Decomposition is applied in polarimetry method and four classification objects are obtained. Based on the modification of class simplification, the surface scattering is presented in blue color which generally describes the waters on the surface of the earth, green color for volumetric scattering, which describes about plants and forest, red or pink for the double bounce scattering depicting the settlement, urban and building and yellow for helix scattering which is the same as double bounce but the helix will more clearly identify the plant-covered settlements

DEVELOPING TROPICAL LANDSLIDE SUSCEPTIBILITY MAP USING DINSAR TECHNIQUE OF JERS-1 SAR DATA

Comprehensive information in natural disaster area is essential to prevent and mitigate people from further damage that might occur before and after such event. Mapping this area is one way to comprehend the situation when disaster strikes. Remote sensing data have been widely used along with GIS to create a susceptibility map. The objective of this study was to develop existing landslides susceptibility map by integrating optical satellite images of Landsat ETM and ASTER with Japanese Earth Resource Satellites (JERS-1) Synthetic Aperture Radar (SAR) data complemented by ground GPS and feature measurement into a Geographical Information Systems (GIS) platform. The study area was focused on a landslide event occurred on 26 March 2004 in Jeneberang Watershed of South Sulawesi, Indonesia. Change detection analysis was used to extract thematic information and the technique of Differential SAR Interferometry (DInSAR) was employed to detect slight surface displacement before the landslide event. The DInSAR processed images would be used to add as one weighted analysis factor in creating landslide susceptibility map. The result indicated that there was a slight movement of the slope prior to the event of landslide during the JERS-1 SAR data acquisition period of 1993-1998. Keywords: Optical Images, JERS-1 SAR, DInSAR, Tropical Landslide, GIS, Susceptibility Map 1. Introduction Recently, natural disasters increased in terms of frequency, complexity, scope, and destructive capacity. They have been particularly severe during the last few years when the world has experienced several large-scale natural disasters such as the Indian Ocean earthquake and tsunami; floods and forest fires in Europe, India and China, and drought in Africa (Sassa, 2005). Mapping such natural disaster areas is essential to prevent and mitigate people from further damage that might occur before and after such event. In Indonesia in particular, in these recent years natural disasters occurred more frequently compared to the last decade (BNPB, 2008). Once within a month in 2011, in three different islands, Indonesia was stricken by earthquake, tsunami, flash floods, and volcanic eruptions with severe fatalities to the people and environment. It was obvious that Indonesia was prone to natural disaster due to its position of being squeezed geologically by three major world plates and this fact makes Indonesia one of the most dangerou

Compact Broadband Dual-Sense Circularly Polarized Microstrip Antenna/Array With Enhanced Isolation

This paper presents a novel method of designing the compact dual-sense circularly polarized (CP) microstrip antenna/array with improved impedance bandwidth, axial ratio (AR) bandwidth, and interpolarization isolation. The left-hand and right-hand CP characteristics are achieved simultaneously by conceiving a vertically coupled resonant structure for the first time. Different from traditional methods, the antenna shows a compact size but exhibits the wide impedance and 3 dB AR bandwidths. For each input, two coupling paths are purposely designed to excite the TM10 and TM01-mode of the patch, respectively. By composing different coupling units in the two paths, an intrinsic ±90° phase difference over a broadband can be obtained, resulting in the broadband CP characteristics. In addition, a novel method of using the neutralization line between the two feeds is investigated to improve the isolation between the polarizations. Based on the dual-sense CP element, a 1×4 dual-sense CP array is composed to exemplify its potential applications in large arrays. Compared with traditional CP antennas, the proposed antennas have the advantages of compact size, simplified feed, broad impedance and 3 dB AR bandwidths, and improved isolation. Experimental results verify the predictions

Simulated Mitigation of Tsunami Disasters in the Coastal Area of Purworejo Regency, Central Java, Indonesia

The coastal area of Purworejo Regency has the potential to be hit by a mega-tsunami disaster because it includes the southern coast of Java Island which is faced with seismic gaps that may produce large earthquakes in the future. This study aims to simulate tsunami disaster mitigation in the coastal area of Purworejo Regency in an effort to raise awareness and increase the community capacity for dealing with potential tsunamis so that the level of loss can be minimized. The tsunami risk analysis is based on the Disaster Crunch model, which is a combination of vulnerability analysis based on the weighted overlay quantitative method and tsunami hazard analysis based on tsunami inundation reduction modeling and cost distance analysis. The planning of the tsunami evacuation route is based on the network analysis method. The tsunami-risk area with a run-up scenario of three meters in the coastal area of Purworejo Regency 126,29 square kilometers or about 72,52% of the total coastal area. There are five tsunami evacuation plan points, with five main tsunami evacuation routes that lead directly to each of these points