Ultra-high frequency ultrasound and simultaneous influence of ultra-high and low frequency ultrasound in sonoluminescent spectroscopy

Radio frequency identification (RFID) technology has been widely used in various industries due to its object identification and monitoring capability. In recent years, low-frequency (LF) RFID has been increasingly used in hydraulic studies for sediment transport studies and the detection of underground utilities. Nevertheless, prior studies have indicated that the use of LF RFID technology is limited due to its short detection range and high sensitivity of orientation relative to the antenna place. Ultra-high frequency (UHF) RFID (865-928 MHz) technology has much longer reading ranges compared to the LF RFID. However, up to date, the application of UHF RFID technology in aquatic environments is still rare because of its high sensitivity to water. This study aims to investigate the reading range behaviors of passive UHF RFID tags for surface applications in aquatic environments. This research used circular and linear polarization antennae, which have a gain of 8 dBic, 9 dBic, and 12.5 dBi, respectively, to examine six pre-selected UHF RFID tags behaviors. The results of this study showed that a decrease in the performance of maximum reading distances when the tags are placed in a vertical orientation at the center of the antenna compared with the horizontal orientation. The maximum reading ranges varied between 1 to 35% when using the 8 dBic antenna, between 0% to 48% with the 9 dBic antenna, and between 14 to 82% with the 12.5 dBi antenna. Based on key findings and observations from this study, we demonstrated design requirements of tags to overcome sensitivity limitations to design for future surface-water velocity monitoring applications in the natural open water and built water transport environments.

Passive UHF (ultra high frequency) RFID (radio frequency identification) is a promising technology for products tracking in logistics or routing packages in supply chain. However, passive UHF RFID tag suffers a lot when it is placed on conductive plane or water surface. Many designs like microstrip antenna and ferrite antenna have been used to solve this metal-water problem. But their use is limited by narrow bandwidth and low antenna gain. The electromagnetic band gap (EBG) material which exhibits a unique forbidden band gap at certain frequency offers a potential solution to solve the problem of backside objects effects. Previous research paper indicated that the dipole RFID antenna above three-layer mushroom like EBG material exhibited a good antenna gain and long read range. However, the complicated structure and high material cost greatly limit the application of tag. In this paper, we developed a new type of EBG material which uses ferrite film to reduce size and lower forbidden frequency. A commercial ferrite film which has a high permeability is applied to form two-layer mushroom like EBG material for UHF RFID. This two-layer mushroom like EBG material is a two-layer structure with a ground plane. The design of EBG material for UHF RFID which operates at 915 MHz was discussed in this paper. An EBG tag on metal with a gain of 7 dBi was achieved in simulation. The simulation results showed that the RFID tag still could be read on EBG substrate with a good gain (~7 dBi).

Passive UHF (ultra high frequency) RFID (radio frequency identification) is a promising technology for products tracking in logistics. However, the UHF RFID tag is greatly affected by backside goods especially metallic objects. In this paper, we introduce a new technique to insulate the UHF RFID tag from backside objects. An electromagnetic band gap (EBG) material which is a good electromagnetic wave insulator is prepared as RFID tag substrate. With this substrate, the measurement results shows that the UHF RFID tag still can be read with high speed even on the metallic objects within a short range (0.5 m).

Summary The Electromagnetic Propagation Tool (EPT) has demonstrated that the electrical conductivity and dielectric permittivity of rocks at microwave frequencies are different from those at low frequencies. These differences are helpful in determining the properties of the rocks and the fluids they contain and thus contribute to improved formation evaluation. Electrical parameters of rocks are found generally complex. A technique has been developed for measuring the complex dielectric permittivity, conductivity, and magnetic permeability over a range of frequencies in the ultrahigh frequency (UHF) and microwave frequency bands (100 MHz to 2.0 GHz). The sample core constitutes the dielectric of a coaxial transmission-line sample holder. With an S-parameter setup, two-port S-parameter measurements are made. The complex constituent parameters ( ', '', sigma, mu) of the core samples then are computed from the S-parameters. Measurements on bulkwater of various salinities demonstrate the salinity dependence of the dielectric constant (E'/Eo) of water at high salinities. The total measured loss is separated into a conductivity loss (sigma) and a dielectric loss (E"/Eo), since the frequency dependence of conductivity loss is well-known. Computed conductivity of bulk water shows little dispersion and is in good agreement with measured low-frequency (400-Hz) values. Introduction The microwave EPT has produced a need for laboratory measurement of the electrical parameters of various rocks at UHF and microwave frequencies and a need to deduce their relationship to formation parameters such as lithology, water saturation, water salinity, etc. This paper describes the first results of our laboratory investigation of the formation constituents (rock matrix and borehole fluids) and the composite formation. Measurements are made over a wide frequency range, from 100 MHz to 2 GHz. A special experimental setup, built for this purpose, also is described. The principal quantities of interest are the (complex) dielectric constant and the electrical conductivity. Measurements are made by using samples in a coaxial transmission line and the well-known S-parameter method of data analysis. Measurements have been made on bulk water of various salinities (NaCl) and on carbonate and silicate rock samples, both dry and impregnated with waters of various salinities. Measurements also have been made on fused glass beads impregnated with waters of several salinities. Measured values of dielectric constant are compared with values computed for clean formations. Measurement Theory Type of Measurement Measurements of electrical parameters at high frequencies can be made by reflection, transmission, or resonant-cavity methods. The reflection method is a one-port measurement. (The other port is terminated successively in an open circuit and short circuit at each frequency). This method gives good results for low- and medium-loss samples but poor results for samples with high losses. The transmission method is ideal for high-loss samples. However, in samples that are too short, end reflections will produce spurious measurements. The resonant-cavity technique gives good results for medium- and low-loss samples. For high-loss samples, the sample size has to be reduced drastically to maintain the accuracy of the measurements. When measurements are made over a wide frequency range, the cavity dimensions must be changed with each resonant frequency, a rather cumbersome procedure. JPT P. 2689^

Wearable electronics are occupying an increasing portion of our daily activities. The span of wearable applications extends from purely medical, over different security services to various sports and fashion devices. Antennas play one of the most important roles in wearable networks as they have a key contribution to the overall efficiency of a wearable wireless link. This work focuses on the design and practical realization of robust wearable antennas intended for voice communication inside the Ultra High Frequency (UHF) band. The proposed antennas are mainly envisioned for security services such as military, police or rescue services. To this aim, several questions have been addressed while analyzing and designing the proposed antennas. The on-body environment significantly affects the characteristics of an antenna. The coupling between the antenna and the host body influences both the antenna and the body characteristics. On one hand, the complex lossy nature of the hosting body tends to deteriorate the radiation performances of the wearable antenna, while on the other hand, the radiation from the antenna can cause an increase of the temperature of the wearer’s body (localy and/or of the entire body). The wearability aspect also requires that the size and the profile of the antenna are appropriate so that it can be easily integrated into the wearer’s garment. The size of the wearable antennas becomes more critical at lower frequencies (for instance UHF), where the wavelengths become comparable with the size of the body, thus adding an additional limitation while selecting the type of the antenna. A Planar Inverted F Antenna (PIFA) was selected as an appropriate antenna candidate addressing the introduced specifications. In parallel with the antenna prototype, a suitable technology, combining flexible conductors and stretchable substrates, has been proposed. The suggested technology also enables an adjustment of the electric properties of the designated substrate materials. Several antenna prototypes were successfully designed, fabricated and characterized. Finally, a set of tests in realistic everyday conditions were performed, thus validating the performance of the proposed antenna concepts along with the proposed technology and assessing their potential of being used for commercial purposes. We believe that the obtained results provide useful guidelines for future design of robust flexible wearable antennas.

Radiofrequency Identification (RFID) is a technology that is being rapidly developed and that uses radiofrequency (RF) signals for the automatic identification of objects or persons. Although the first article regarding modulated electromagnetic backscattering (basic principle of passive RFID) was published in 1948 (Stockman, 1948) it has been a long way to progress for reaching today levels (Rao, 1999; Finkenzeller, 2004; Pozar, 2004). Nowadays RFID finds many applications in logistics, supply chain management, access control, electronic toll systems, targets identification, vehicle security, animals tracking and patients’ identification in hospitals. An RFID system is composed of a reader, a reader antenna (usually circularly polarized patch antenna), RFID ‘tags’ or transponders and a middleware or subsystem of data processing. A passive RFID tag consists of an antenna and an application specific integrated circuit (ASIC) chip. IC chips have complex input impedances, and their impedances vary with frequency. A key point for tag antenna design is that it must be conjugately matched with the desired IC chip for the maximum power transfer (Gevi, 2004; Rao et al, 2005). The different types of RFID systems are distinguished by two major characteristics: the power source of the tag and the frequency of operation. With regards to the power source of the tag, they can either be active (powered by battery), passive (powered by the reader field) or semi-passive (battery assisted backscatter). According to the frequency of operation the RFID systems are generally distinguished into four frequency ranges; i.e., low frequency (LF) (125-134.2 kHz), high frequency (HF) (13.56 MHz), ultra high frequency (UHF) (433, 860-960 MHz) and microwave frequency (2.45, 5.8 GHz). In addition, the standards of the UHF RFID are different for each country: 866-869 MHz in Europe, 902-928 MHz in America and 950-956 MHz in Asia. The communication frequencies used depends to a large extent on the application. Regulations are imposed by most countries (grouped into 3 Regions: US, Europe and Asia) to control emissions and prevent interference with other Industrial, Scientific and Medical equipment (ISM). The higher the frequency band the faster the speed of tag reading and also the larger the information storage capacity. This is the reason why UHF RFID has gained popularity in many applications and it can be expected that the same will happen in the near future with microwave RFID. In a typical application tags are attached to objects (or persons). Each tag has a certain amount of internal memory (EEPROM) in the chip in which it stores information about the

Recently, with the downsizing of computers and the development of wireless communication advances, sensor networks are being widely studied. However, it is necessary to know the location of each node, in order to apply sensor data. Many researchers have tried to find a good approach to position estimation in indoor environment. In our study, we focus on position estimation by using Received Signal Strength Indication (RSSI). It has the advantage of implementation with limited resources in the sensor network. However, since RSSI value is affected by multipath and obstacles, position estimation may yield considerable errors. In our research, we propose a range estimation technique with RSSI on Low Frequency (LF) waves. Since RSSI value on LF waves is less affected by multipath and obstacles compared with RSSI on Ultra High Frequency (UHF) waves used for a communication, position estimation with high accuracy can be calculated using this method. We show an RSSI measurement sensor which measures the RSSI on LF waves and a transmitter which sends radio waves on the 125 kHz band. Results of experiments using our developed modules and a ZigBee module demonstrated the robustness of RSSI on LF waves against multipath and obstacles compared with UHF waves. In this paper, a range estimation experiment was performed by applying the proposed modules and range estimation accuracy was evaluated through experiments.

RFID (radio frequency identification) technology has gained popularity in a number of applications. Decreased cost of hardware components along with wide adoption of international RFID standards have led to the rise of this technology. One of the major factors associated with the implementation of RFID infrastructure is the cost of tags. RFID tags operating in the low frequency spectrum are widely used because they are the least expensive, but have a small implementation range. This paper presents an analysis of RFID performance across low frequency (LF), high frequency (HF), and ultra-high frequency (UHF) environments. The authors' evaluation is theoretical, using a passive-tag BFSA based simulation model that assumes 10 to 1,500 tags per reader and is created with OPNET Modeler 17. Ceteris paribus, the authors' results indicate that total census delay is lowest for UHF tags, while network throughput performance of LF tags is highest for large scale implementations of hundreds of tags in reader's range. A statistical analysis has been conducted on the findings for the three different sets.

RFID or Radio Frequency Identification refers to the technology of transmitting the identity of people or objects wirelessly as a unique code [1]. This technology is divided into four categories depending on the frequency band in which it is operated: low frequency (LF), high frequency (HF), ultra-high frequency (UHF) and microwave frequency (MW). UHF RFID flourished when the Auto-ID centre at Massachusetts Institute of Technology was established in 1999 [2]. This type of RFID has several advantages compared to other types including higher data rates, requiring only simple dipole-like antennas, and longer ranges [3]. Standards of use of RFID's depend on the country in which they are used. In Australia, the allocated band for UHF RFID is 918 MHz- 926 MHz [3]. This paper proposes an array of three compact phase shifters for use in UHF RFID applications such as phased array antennas. The proposed phase shifters operate at 910 MHz with a bandwidth of 100 MHz, thus covering the Australian band completely.

Standard probes for near-field antenna measurements, open-ended waveguides, become bulky and heavy at lower frequencies, below about 2 GHz, that complicates their handling. This paper presents a practical design of a log-periodic dipole antenna (LPDA) specifically developed to possess low level of cross-polarization, to be used as a probe for near-field antenna measurements at frequencies below 2 GHz. The manufactured antenna has low weight and it is easy to handle. The covered frequency band is from 500–1100 MHz, which corresponds to two standard waveguide bands. The antenna can be easily scaled to lower or higher frequencies in the UHF band.

This paper presents experiments carried out on sections of typical subsea 11kV HV cable with an artificially created fault geometry, namely a semiconductor point fault which is then compared to a clean termination (no point fault) with the fault removed. Partial Discharge (PD) measurements using IEC60270 phase-charge-number (PQN or (Φ-q-n), peak High Frequency Current Transformer (HFCT) (Φ-q-n, Low Frequency (LF) HFCT RF EMI and radiated Ultra High Frequency (UHF) RF are undertaken. All measurements are synchronised in time allowing correlation between the produced Φ-q-n and RF spectral measurements over time to investigate changes and possible characteristic behavior between the four methods. Few publications have investigated the correlation of IEC60270 Φ-q-n, HFCT Φ-q-n, RF EMI spectra from a LF HFCT and radiated (UHF) RF spectra for potential PD cable fault geometries. Initial results demonstrate that a semiconductor point fault condition produces different PD characteristics in both the frequency domain and Φ-q-n domain. This has the potential for higher discrimination ability between this fault geometry and clean termination when both systems are utilized. This could also show RF EMI HFCT measurements to be comparable to and potentially replace the IEC60270 method.

As part of a large population-based study of hearing and aging, ultra high-frequency (9-20 kHz) threshold measures are reported for 3396 participants grouped by age (48-59 years, n = 1233; 60-69 years, n = 1031; 70-79 years, n = 851; 80-92 years, n = 281). Ultra high-frequency (UHF) thresholds were higher for older age groups. The percentage of unmeasurable responses also was significantly higher for older age groups and for higher frequencies in the UHF range. The observed age effects remained significant after adjusting for gender. In general, UHF thresholds were significantly higher for men compared to those for women at lower UHF frequencies (9-14 kHz), but were not significantly different by gender for the highest UHF frequencies (16, 18, and 20 kHz). After accounting for hearing loss at traditional audiometric frequencies (250-8000 Hz), the age effect still remained; even for comparable degrees of sensorineural hearing loss, participants in older age groups evidenced higher UHF thresholds.

BackgroundHearing loss (HL) is a well-known feature of Fabry disease (FD). Its presence and characteristics have mainly been studied in adult patients, while only limited data are available on the presence and degree of HL in children with FD. This prompted us to study hearing sensitivity in pediatric FD patients.MethodsAll available audiograms of the Dutch and Norwegian children with FD were retrospectively collected. First, hearing sensitivity was determined by studying hearing thresholds at low, high, and ultra-high frequencies in children with FD and comparing them to zero dB HL, i.e., healthy children. In addition, the presence and type of slight/mild HL (defined as hearing thresholds at low frequencies of 25–40 dB HL) and moderate to severe HL (hearing thresholds >40 dB HL) at first visit were analyzed. If available, follow-up data were used to estimate the natural course of hearing sensitivity and HL in children with FD.ResultsOne-hundred-thirteen audiograms of 47 children with FD (20 boys, median age at first audiogram 12.0 (range 5.1–18.0) years) were analyzed. At baseline, slight/mild or moderate to severe HL was present in three children (6.4%, 2 boys). Follow-up measurements showed that three additional children developed HL before the age of 18. Of these six children, five had sensorineural HL, most likely caused by FD. Compared to healthy children (zero dB HL), FD children showed increased hearing thresholds at all frequencies (p < 0.01), which was most prominent at ultra-high frequencies (>8 kHz). Hearing sensitivity at these ultra-high frequencies deteriorated in a period of 5 years of follow-up.ConclusionA minority of children with FD show slight/mild or moderate to severe HL, but their hearing thresholds are poorer than the reference values for normal-hearing children. Clinical trials in FD children should demonstrate whether HL can be prevented or reversed by early treatment and should specifically study ultra-high frequencies.

The dielectric behavior of different polar high polymers at ultra‐high frequencies has been investigated by means of a dielectrometer, suitably modified to permit measurements at different temperatures. Experimental measurements were made at about 9 × 109 cps over the temperature range of −150 to 200°C. for polyoxymethylene, polythiomethylene, poly(3,3′‐chloromethyl)oxetane (Penton), polycarbonate of 4,4′‐dioxydiphenyl‐2,2′‐propane (Makrolon), poly(vinyl alcohol), poly(vinyl acetate), poly(vinyl chloride), vinyl chloride–vinyl acetate copolymer, and two ABS plastics, type B (blend) and type G (graft). On comparing the dielectric behavior of the examined materials at ultra‐high frequencies with the corresponding ones determined at low or at radiofrequencies, it is observed that, in the microwave region, all relaxation peaks, either connected with cooperative motions in main chain (primary processes) or with local motions in the backbone or in side chains (secondary processes), usually observed at lower frequencies, tend to disappear; the corresponding relaxation effects, however, manifest themselves through a progressive increase of losses with increasing temperature, which is particularly marked above the glass transition temperature Tg. The latter transition, in spite of the very high frequency, is easily distinguished, in most cases, by the sudden change of slope in the tan δ versus temperature curve which accompanies its onset. This is explained on the basis of the very wide distribution times of molecular relaxation processes in polymers and the increase in strength of the secondary relaxation effects, which is verified at Tg, as a consequence of the increased kinetic energy of macromolecules and of the larger free volume for orientation of side chains. Each case is discussed separately and the experimental results interpreted on the basis of the molecular structure and chain mobility of the examined polymers.

A consideration of the special problems encountered at ultra-high frequencies has led to the design of a push-pull power pentode, useful as an amplifier, frequency multiplier, and modulator at frequencies of 300 megacycles per second and below. Unusual construction features include the mounting of two pentodes in the same envelope with interconnected screen and suppressor grids, complete shielding between the input and output circuits with no common leads, and provision for cooling all grids while maintaining extremely small inter-electrode spacings. The electrical characteristics depart from the conventional mainly in the low value of lead inductances and the high value of the grid input resistance at ultra-high frequencies. The second part of the paper describes a single stage amplifier unit built for testing the tube at frequencies between eighty and 300 megacycles, and the associated apparatus for measuring input impedance, gain, and harmonic distortion. The results given indicate that by using this new tube it is possible to construct stable amplifiers at ultra-high frequencies up to 300 megacycles, having gains of twelve to twenty-five decibels per stage and delivering several watts of useful power. Stability and distortion compare favorably with those obtained from conventional tubes at much lower frequencies.