Ultra High Frequency Band Research Articles

Study of matching characteristics for Ni0.97−xZnxCo0.03Fe2O4 spinel ferrites

A perfect matching chart is designed to obtain the matching frequency fm and the matching thickness tm of electromagnetic (EM) attenuation material. Based on the chart, the relationship between matching parameters (fm and tm) and high-frequency dynamic parameters [μ′(f), μ″(f), and ϵ′(f)] are studied for Ni0.97−xZnxCo0.03Fe2O4 (NiZnCo) spinel ferrites with x=0.5 and 0.65. At tm, the spinel ferrites exhibit excellent EM attenuation characteristics with low reflectivity and broad bandwidth at very high frequency and ultrahigh frequency bands.

UHF 대역 RFID 시스템용 고감도 광대역 태그 안테나의 설계

본 논문은 UHF 대역 RFID 시스템용 고감도 광대역 태그 안테나의 설계에 대하여 기술한다. 제안된 태그 안테나의 크기는 <TEX>$60\;mm\;{\times}\;10\;mm\;{\times}\;1\;mm$</TEX>이다. 공진 주파수는 910 MHz 이고, - 10 dB이하 대역폭은 약 900 MHz이다. 측정된 반사손실과 지향성 패턴은 계산결과 잘 일치하는 것으로 확인되었다. 칩을 가진 제안한 태그 안테나의 인식거리는 6.5 m로 관측되었으며, 이 값은 상용 태그 안테나의 인식거리보다 평균 0.5 m이상 멀리 감지된 결과이다. This paper presents the design of high sensitive/broadband tag antenna for Radio Frequency Identification (RFID) in Ultra High Frequency(UHF) band. A proposed tag antenna size is <TEX>$60\;mm\;{\times}\;10\;mm\;{\times}\;1\;mm$</TEX>. The resonant frequency is 910MHz and bandwidth is about 900 MHz at -10 dB below. The measured return loss and directional pattern have been confirmed a good agreement with the calculation results. The read range of proposed tag antenna with chip is observed about 6.5 m and proposed tag antenna has been observed an average 0.5 m for more than read range of the commercial tag antenna.

Adjustable axial ratio of single-layer circularly polarised patch antenna for portable RFID reader

A novel single-layer, proximity-fed technique for a slot-coupled circularly polarised square patch antenna operated in the ultra-high frequency band is presented. In the proposed design a pair of radiating square patches with a cross-slot and a microstrip feed line are both etched on the top of a microwave substrate, and a coupling arrow-shaped slot is etched on the bottom of this substrate. Simulated and measured results indicate that the proposed structure can achieve circular polarisation operation. Proper adjustment of the feed coupling gap distance between the patch and the feed line results in good impedance matching and circularly polarised radiation, and an impedance bandwidth (VSWR≤2) of about 3.74% and a 3 dB axial-ratio bandwidth of about 1.62% were obtained.

Postured voxel-based human models for electromagnetic dosimetry

High-resolution anatomically realistic whole-body voxel models have recently been developed for electromagnetic dosimetry. However, the posture of most models is similar to the standing one, which strongly limits electromagnetic dosimetry when simulating a realistic exposure scenario. In this paper, we present the development of postured models based on anatomically realistic voxel models with standing posture. Voxel models of the Japanese adult male and female were used as the original upright standing models. The Japanese models were composed of 2 mm cubic voxels, each of which was segmented into 51 different tissue types. We developed several different types of posture models using a novel posture transformation method. These posture models were smoothly transformed, while the continuity of the internal tissues and organs was maintained. In this paper, we also present our calculations of the whole-body averaged specific absorption rates (SARs) of sitting male and female models exposed to electromagnetic plane waves at very high (VHF) and ultra high frequency (UHF) bands.

Some experimental investigation of the effect of railway tunnels on mobile communications in Western India

Establishing of mobile communications in guided structures like railway tunnels, coal mines, etc., is gaining increasing importance due to the passage of high speed and high density of trains in tunnels and for monitoring of information on safety of workers and day-to-day operations in various mines. The present study reports investigation of mobile communication experiments in ultra high frequency band in railway tunnels of western India conducted in a moving train both in uplink and downlink directions. The observed signal fluctuations are discussed in terms of tunnel characteristics and different modes of propagation in tunnels and compared with model deduced values.

Multiport Sensor RFIDs for Wireless Passive Sensing of Objects—Basic Theory and Early Results

A new family of passive sensor radio-frequency identification devices is here proposed for applications in the context of wireless sensor networks. The new tags, working in the ultra-high frequency band, are able to detect the value or the change of some features of the tagged body without using any specific sensor. Such tags are provided with multiple chips embedded either within a cluster of cooperating antennas or in a single multiport antenna, and exploit the natural mismatch of the antenna input impedance caused by the change of the tagged object. A basic theory of multiport sensor tags is formulated with the purpose to describe the possible classification and detection performances in a unitary context. Some numerical examples and a first experiment corroborate the feasibility of the idea.

A fractal dipole tag antenna for RFID dual‐band application

AbstractNew design of a dipole antenna with rectangular fractal shape radiator element with two operating bands for radio frequency identification (RFID) is presented. By using fractal shape slot and metal meander patch, the proposed antenna has the wide and dual measured return loss bandwidth. Besides, the omnidirectional radiation pattern of the design antenna cover the entire frequency range including ultra high frequency (UHF, 860–960 MHz) band and microwave (2.45 GHz) band has been obtained. Several properties of the proposed antenna for dual‐band operation such as impedance bandwidth, radiation pattern, and measured gain have been investigated numerically and experimentally in detail. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1963–1966, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23512

Study of a dielectric‐loaded folded monopole antenna at UHF band for DVB‐H terminals

AbstractThis article presents a study on a dielectric‐loaded folded monopole antenna operating at ultra high frequency band for Digital Video Broadcasting‐Handheld terminals. It is an optimization of the folded monopole antenna in our previous work. The proposed antenna has a 43% reduction in volume when compared with the previous design. Because of the ground plane independency of the antenna, the proposed antenna can be mounted on any type of ground plate, thus improving the adaptability to different terminal designs. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 487–490, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23111

Compact wideband cavity-backed slot antenna

A wideband cavity-backed slot antenna operated in the ultra-high frequency (UHF) band is introduced. The antenna has a compact structure and low profile with the size ratio of the ground plane to the slot only 1.6:1. The measured impedance bandwidth of VSWR⩽3 achieves 85.3%, covering a frequency range from 390 MHz to 970 MHz. The measured gain is about 5.5∼7.5 dB.

Low frequency lumped element-based negative index metamaterial

A lumped element-based negative index metamaterial (NIM) was designed, fabricated, and tested for operation at 400MHz in the ultrahigh frequency (UHF) band. At 400MHz the measured real part of the index of refraction of this NIM was nreal=−3.11 with a loss that was less than 1dB∕cm using unit cells whose overall size d was λ∕d∼75. The NIM bandwidth was &amp;gt;10% in the neighborhood of 400MHz.

An Ultra-Low-Power Long Range Battery/Passive RFID Tag for UHF and Microwave Bands With a Current Consumption of 700 nA at 1.5 V

We present for the first time, a fully integrated battery powered RFID integrated circuit (IC) for operation at ultrahigh frequency (UHF) and microwave bands. The battery powered RFID IC can also work as a passive RFID tag without a battery or when the battery has died (i.e., voltage has dropped below 1.3 V); this novel dual passive and battery operation allays one of the major drawbacks of currently available active tags, namely that the tag cannot be used once the battery has died. When powered by a battery, the current consumption is 700 nA at 1.5 V (400 nA if internal signals are not brought out on test pads). This ultra-low-power consumption permits the use of a very small capacity battery of 100 mA-hr for lifetimes exceeding ten years; as a result a battery tag that is very close to a passive tag both in form factor and cost is made possible. The chip is built on a 1-mum digital CMOS process with dual poly layers, EEPROM and Schottky diodes. The RF threshold power at 2.45 GHz is -19 dBm which is the lowest ever reported threshold power for RFID tags and has a range exceeding 3.5 m under FCC unlicensed operation at the 2.4-GHz microwave band. The low threshold is achieved with architectural choices and low-power circuit design techniques. At 915 MHz, based on the experimentally measured tag impedance (92-j837) and the threshold spec of the tag (200 mV), the theoretical minimum range is 24 m. The tag initially is in a "low-power" mode to conserve power and when issued the appropriate command, it operates in "full-power" mode. The chip has on-chip voltage regulators, clock and data recovery circuits, EEPROM and a digital state machine that implements the ISO 18000-4 B protocol in the "full-power" mode. We provide detailed explanation of the clock recovery circuits and the implementation of the binary sort algorithm, which includes a pseudorandom number generator. Other than the antenna board and a battery, no external components are used.

Partial discharge diagnosis method using electromagnetic wave mode transformation in gas insulated switchgear

Though the gas insulated switchgear (GIS) insulation diagnosis method using ultra high frequency (UHF) band signal is widely used as a method to detect partial discharge (PD) sensitively, diagnosis methods for the electromagnetic wave mode propagation behavior in GIS tanks have not been investigated enough. Especially, diagnosis methods based on the electromagnetic wave distribution of the circumferential direction have been rarely discussed. In the preceding studies by the authors comparing investigations were made by experiments and analyses on the electromagnetic field distribution patterns of the GIS circumferential direction in front of or behind the L-shape or T-shape structures. It was found that the electromagnetic field distributions that are characteristic of mode transformations are seen when the electromagnetic waves of the PD signals are propagated through the L-shape and/or T-shape structures in the GISs. In this study, the diagnosis algorithm is constructed by extracting the characteristics in the output of the high order mode electromagnetic waves transmitted through the L-shape part and/or T-shape part. If the output distributions of the signals detected before and/or after the transmitting have those characteristics, the signals can be determined to be the ones propagated inside and the information on the circumferential direction position of the signal source can be obtained. A simple diagnosis method with high precision has been developed as a GIS-PD diagnosis technology in the field based on the diagnosis algorithm as above. The diagnoses in the field can be classified into the first order diagnosis for high sensitivity detection and the second order diagnosis for high precision judgment by using the algorithm to do more reliable evaluation.

An Efficient Tree-Based Tag Anti-Collision Protocol for RFID Systems

This paper proposes an efficient tree-based anti-collision protocol for passive tags used in ultra high frequency (UHF) band. To simultaneously achieve the minimization of the time complexity and of the power consumption, this paper first employs the depth-first search (DFS) algorithm as a basic search criterion of this protocol, and then implements the DFS algorithm through a height-oriented method of using an encoded binary number corresponding to the height of the vertex at which the tag collision most recently occurred

A Fundamental Study on Management Method for Light Weight Temporary Facilities Using Metal Radio Frequency Identification Tags

As light weight temporary facilities are used many times and are deteriorating over a long time, it is desired to identify the actually used period for each member and to abandon the members if they are used overtime. However, this has never been executed before since it takes too much time and cost. The authors performed experiments for applying ultra high frequency (UHF) band radio frequency identification (RFID) tags to management of light weight temporary facilities before and found it feasible but observed the necessity of protecting soft UHFT RFID tags used for the experiments. Now that new 2.45GHz band RFID tags that are covered with metal and that are resistant to shocks have been developed, the authors executed experiments on the usability of the new metal RFID tags and on the application of them to light weight temporary facilities. The results showed that the new metal RFID tags can be used if they are attached to metal members by inserting 2mm thick non metal object between the metal surface and the RFID tag. Furthermore, the authors developed a prototype of a database system for managing the usage of light weight temporary facilities by using the metal RFID tags. The database system deployed a relational data model having five tables representing data of facility members and leasing track records. This system was tested for reading multiple RFID tags attached facility members and demonstrated its feasibility and practicality.

Urban Propagation Measurements for Ground Based Communication in the Military UHF Band

Results are presented from an experimental investigation to characterize path loss in urban terrain within the military ultrahigh frequency band (225 to 450 MHz) between ground-based communicators. Testing was conducted over a two-day period in downtown Philadelphia. Profiles of received power versus distance were generated along a variety of straight and L-shaped paths for different radio frequencies and antenna heights. The results were analyzed to determine the dependency of the received power on street width, frequency, antenna height, and corner distance (the distance between the transmitter and the corner on an L-shaped path). The results showed well-defined dependencies on all of the parameters except antenna height, which did not appear to affect the results over the range of values considered in this study. An empirical model for predicting received power was developed by fitting regression curves to the data. The model was found to be accurate to within approximately /spl plusmn/10 dB when compared against the data collected in this investigation. This study addresses an important but heretofore largely overlooked propagation environment.

A direct-conversion receiver for DVB-H

A fully integrated low-power ultrahigh-frequency (UHF) tuner integrated circuit (IC) design for the digital video broadcasting-handheld (DVB-H) market is presented. A direct-conversion receiver is chosen over classical digital video broadcasting-terrestrial (DVB-T) architectures. The tuner IC covers UHF bands IV/V. The solution is based on a radio frequency integrated circuit (RFIC) and external low-noise amplifier (LNA) to meet the noise figure (NF) specification of 5 dB, IIP3 of 4dBm, and Gain of 89 dB. The IC includes an LNA, dual quadrature mixers, multiple bandwidth baseband (BB) filtering, three 4X voltage-controlled oscillators (VCOs), integer phase-locked loop (PLL), and reference oscillator. The design is implemented in a SiGe:C bipolar complementary metal oxide semiconductor (BiCMOS) technology and the die area is 11.5 mm/sup 2/.

소화관 내 압력 측정을 위한 텔레메트리 캡슐 구현

As the cause and the treatment about gastrointestinal disease has been issued recently, the importance of measuring the pressure in the gastrointestinal tract has been increased. However, the conventional measurement methods of the pressure in the gastrointestinal tract cause the patients' pain and inconvenience as well as an inaccurate pressure measurement. In this paper, the pressure monitoring telemetry system has been designed and implemented for an accurate pressure measurement inside the gastrointestinal tract with minimizing pain and inconvenience. The pressure monitoring telemetry system is composed of a pressure measurement capsule and an external receiver. The capsule has been miniaturized into the same size of a vitamin tablet so that the capsule can be swallowed through the oral cavity. After the capsule acquires and encodes the pressure data in the gastrointestinal tract, the encoded pressure data are modulated by frequency shift keying (FSK) and transmitted with ultrahigh frequency (UHF) band signal to the outside of a body. The performance of the telemetry capsule for monitoring pressure in the gastrointestinal tract is demonstrated by the results of animal in-vivo experiments.

Microplasma Noise Stimulated by Microwave Electric Field

Si and GaAs avalanche diodes containing microplasmas are investigated.Microwave fleld applied to the diode in addition to reverse dc bias results inconsiderable spread of noise spectrum and in the increase of noise power. Themicroplasma noise spectra cover very high (30 to 300 MHz) and ultrahigh(300 to 1000 MHz) frequency bands, while the efiective noise temperature isabout 10

Every Bag in Place

This article focuses on the use of radio-frequency (RF) technology in Las Vegas airport. The RF technology is provided by Matrics Inc. of Columbia, Md., which has a five-year contract to supply the airport with 100 million tags. The tags, which hold 96 bits of information, require no separate power source and are activated by a signal from the RF reader in the ultra-high frequency band between 902 and 928 MHz. The Federal Aviation Administration requires that passengers’ names pass through the Computer Assisted Passenger Pre-screening System. Those profiled as suspicious by the system are known as ‘selectees.’ At Jacksonville, their bags are tracked by an ultra-high frequency UHF system. According to a case study published by FKI Logistex, the selectees’ bags are separated from the main stream of luggage and sent to a machine set for more intense screening. However, at Las Vegas airport, everybody will be tagged.

Impact-ionization wave breakdown and generation of picosecond pulses in the ultrahigh-frequency band in GaAs drift step-recovery diodes

It is shown experimentally for the first time that the operation of GaAs drift step-recovery diodes produced on the basis of p + - p 0 - n 0 - n + is accompanied by the generation of ultrahigh-frequency oscillations in the form of trains of short pulses with a duration of ~10 ps. The amplitude and repetition frequency of these pulses are as high as ~100 V and ~(10-100) GHz, respectively. The phenomena of delayed reversible wave breakdown and excitation of ultrahigh-frequency oscillations in the structures of GaAs step-recovery diodes are found to open up new avenues for progress both in the physics and technology of semiconductor devices based on GaAs structures and in the technology of ultrahigh-frequency systems and devices that deal with pulsed sig- nals of picosecond-scale duration. © 2003 MAIK "Nauka/Interperiodica".