UHF Research Papers - Academia.edu (original) (raw)

An integrated remote sensing/field ecology project was carried out to link the use of synthetic aperture radar (SAR) and other remotely sensed data to studies of landscape spatial heterogeneity and bird community ecology as a first step... more

An integrated remote sensing/field ecology project was carried out to link the use of synthetic aperture radar (SAR) and other remotely sensed data to studies of landscape spatial heterogeneity and bird community ecology as a first step toward applications in predicting biodiversity. P-, L-, and C-band SAR data were collected over a section of the South Alligator River in Kakadu

SIR-C/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get... more

SIR-C/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get four-polarization radar imagery at multiple surface angles. The X-SAR system is an X-band imaging radar operating at 9600 MHz. The discussion covers the mission concept; system design; hardware; RF electronics; digital electronics; command, timing, and telemetry; and testing.

Readability of ultra-high frequency (UHF) passive tag applied on food depends on many factors, such as tag features (inlay design, chip type), reader antenna polarization, tag-to-reader antenna distance and orientation, reader transmitter... more

Readability of ultra-high frequency (UHF) passive tag applied on food depends on many factors, such as tag features (inlay design, chip type), reader antenna polarization, tag-to-reader antenna distance and orientation, reader transmitter power output, environmental characteristics, packaging material, as well as product composition. In a real production context, apart the environmental interference which can affect RF wave propagation, both product and packaging characteristics (shape, material, composition) must be considered. The goal of this work is to identify technological features and limits of UHF RFID systems for the electronic identification of food products in different kind of packaging. The effects of different factors as food product, packaging material and tag type were considered for UHF transponder readability evaluation. At this purpose, different tag models and food product categories were subjected to performance analysis comparing, in different item positioning,...

Resumo: This work presents the results of the repetition of the experiments and the continuity of the studies on Radar Absorbing Material (RAM). The RAM is made with dielectric or magnetic substances, and produced in order to promote a... more

Resumo: This work presents the results of the repetition of the experiments and the continuity of the studies on Radar Absorbing Material (RAM). The RAM is made with dielectric or magnetic substances, and produced in order to promote a high absorption in the intensity of the electromagnetic field incident on them. These materials are used in the military and civilian areas as electromagnetic isolators. The purpose of this work is to characterize the absorption level for the 462.6 MHz and 1.800 GHz frequencies caused by the overlapping of asphalt emulsion, graphite and silicone. For this purpose, the measurements were carried out in ceramic boxes coated with the overlap of these materials in well defined layers. The obtained attenuation is superior to 50%, confirming the previous study and the improvement obtained with the addition of the silicone in the set of the RAM. With these results, it is concluded that it is possible to use materials found in local commerce to achieve an ideal electromagnetic insulation with low cost.

This paper investigates the problem of improving the identification performance of a UHF RFID system inside a room. We assume static reader, passive tags and availability of commodity antennas. A ray-tracing propagation model is developed... more

This paper investigates the problem of improving the identification performance of a UHF RFID system inside a room. We assume static reader, passive tags and availability of commodity antennas. A ray-tracing propagation model is developed that includes multipath in 3D space. It is found that careful selection of reader antenna placement and tilting must be performed to control destructive interference effects. Furthermore, 3D coverage performance gains on the order of 10% are observed by implementing tags’ diversity. A device that successfully manipulates destructive interference is introduced. All theoretical findings are verified by measurements. Finally, a method to perform propagation measurements with commodity RFID hardware is demonstrated.

In this paper, a novel compact wideband rejection LPF using defected ground structure (DGS) is presented. The proposed LPF consists of hi-lo etched slots in ground metallic plane as defected ground structure(DGS) and of microstrip hi-lo... more

In this paper, a novel compact wideband rejection LPF using defected ground structure (DGS) is presented. The proposed LPF consists of hi-lo etched slots in ground metallic plane as defected ground structure(DGS) and of microstrip hi-lo structure, which corresponding to capacitance and Inductance on the top layer. The effect of the DGS slot on the characteristics of the investigated filter is examined. In this work we have proposed a simple method to realize a compact DGS LPF with good characteristics . In order to prove the efficiency of the method, a comparison is made between the new DGS LPF and conventional filters , which shows that the proposed filter with etched cells is enough to obtain better performance by suppressing ripples and a very large stop band. Measured results are found to be in good agreement with the simulation results.

The performance of space and frequency diversity techniques at 1800 MHz in an indoor environment are investigated. Three linear signal combining techniques are considered: signal selection (SEL), maximal ratio combining (MRC), and equal... more

The performance of space and frequency diversity techniques at 1800 MHz in an indoor environment are investigated. Three linear signal combining techniques are considered: signal selection (SEL), maximal ratio combining (MRC), and equal gain combining (EGC). The computations of received fading envelopes are performed by means of an analytical model, based on a three-dimensional ray-tracing (RT)/uniform theory of diffraction (UTD) technique; the reliability of the adopted approach is confirmed by comparison with some test measurements. The electromagnetic field components are adequately processed to obtain the single branch and combined signal envelope. The results show the very significant benefits that can be achieved both in terms of diversity gain and diversity advantage for both diversity techniques. Antenna spacings of about 0.75-1λ are nearly sufficient for achieving optimum performance, whereas frequency separation on the order of 10 MHz is needed for sufficiently decorrelated transmission on the two carriers