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AlGaN/GaN high electron mobility transistors (HEMTs) on Silicon substrates grown by molecular beam epitaxy have been investigated using small-signal microwave measurements, to see performance Radio-frequency of components. Passivation of HEMT devices SiO2/SiN a different pretreatment is used to reduce the effects of trapping and consequently has a large effect on these radio-frequency parameters. We used cold-FET and hot FET technique to extract the intrinsic and extrinsic parameters in order to show the effect passivation of parasitic elements; the parasitic capacitances, resistances and inductances. From this point we discover the extent of their impact on power and microwave performance. [ABSTRACT FROM AUTHOR]

We have fabricated top-gated ambipolar field-effect transistors (FETs) based on solution-derived carbon nanotube (CNT) network films, and then constructed inverters and ring oscillators (ROs) that can work under supply voltages as low as 0.2 V owing to the high uniformity of the devices. Significant improvements were achieved in the performance of these CNT-based ambipolar FETs and CMOS-like circuits by scaling down the gate length of the CNT FETs and optimizing the device structure and RO layout. In particular, the optimized five-stage RO is shown to present a record high oscillation frequency of up to 17.4 MHz with a propagation time of 5.6 ns at a 12-V working voltage. The CNT film-based ROs were used as carrier-wave generators in radio-frequency systems to demonstrate a complete signal transmission process. These results suggest that CNT thin film-based FETs and integrated circuits may soon find their way to radio-frequency applications with a frequency band of 13.56 MHz. [ABSTRACT FROM AUTHOR]

A combined low-noise amplifier and voltage-controlled oscillator (LNA-VCO) is implemented in a 0.13-µm CMOS technology. The low-power LC VCO and LNA circuits are stacked and share the same bias current. An LC filter is used between the LNA and the VCO to improve the isolation between the two functions. Based on the measurement results of the proof-of-concept prototype, the LNA achieves a gain of 18.4 dB and a noise figure (NF) of 3.8 dB at 2.4 GHz. The VCO has a center frequency of 2.45 GHz with a −5.3 dBm output power and a phase noise of −119 dBc/Hz at 1-MHz offset. The combined LNA-VCO block consumes 240 µW from a 0.8 V supply. [ABSTRACT FROM AUTHOR]

Previous studies have shown that single or multiple treatments by focused ultrasound are effective and safe. However, most include focused ultrasound only and not radio-frequency treatment. There is paucity of magnetic resonance imaging (MRI) measurements and pictures in the literature. This study aimed to assess the efficacy, safety, and pain and satisfaction levels of the combination therapy of focused ultrasound and radio-frequency for improving body contours. Thirty-two Asian patients received 3 sequential treatments every 2 weeks in the abdominal region. Safety parameters and adverse events were recorded. The subjects' pain and satisfaction levels were evaluated using a five-point Likert scale. Two patients underwent MRI study randomly. There was a mean reduction in circumference of 3.91 ± 1.8 cm ( p ≤ 0.001). In MRI measurement, the average in fat thickness reduction was 21.4 and 25 % on the upper and lower abdomen, respectively. There were three mild and self-limited localized adverse events. The satisfaction survey showed that 71.9 % was satisfied with the results, while pain level evaluation showed that 90.5 % felt no pain. Combination therapy of focused ultrasound and radio-frequency for noninvasive body contouring is an effective, safe, and painless procedure in Asians. Although the change is minor compared to traditional surgical procedure, it is real, definite, and effective. [ABSTRACT FROM AUTHOR]

In this paper, the structural and dielectric properties of SrBiNbO (SBN) as a function of BiO or LaO addition level in the radio (RF) and microwave frequencies were investigated. The SBN, were prepared by using a new procedure in the solid-state reaction method with the addition of 3; 5; 10 and 15 wt.% of BiO or LaO A single orthorhombic phase was formed after calcination at 900 °C for 2 h. The analysis by x-ray diffraction (XRD) using the Rietveld refinement confirmed the formation of single-phase compound with a crystal structure ( a = 5.5129 Å, b = 5.5183 Å and c = 25.0819 Å; α = β = γ = 90°). Scanning Electron Microscope (SEM) micrograph of the material shows globular morphologies (nearly spherical) of grains throughout the surface of the samples. The Curie temperature found for the undoped sample was about 400 °C, with additions of Bi, the temperature decreases and with additions of La the Curie temperature increased significantly above 450 °C. In the measurements of the dielectric properties of SBN at room temperature, one observe that at 10 MHz the highest values of permittivity was observed for SBN5LaP (5%LaO) with values of 116,71 and the lower loss (0.0057) was obtained for SBN15LaP (15%LaO). In the microwave frequency region, BiO added samples have shown higher dielectric permittivity than LaO added samples, we highlight the SBN15BiG (15 % BiO) with the highest dielectric permittivity of 70.32 (3.4 GHz). The dielectric permittivity values are in the range of 28-71 and dielectric losses are of the order of 10. The samples were investigated for possible applications in RF and microwave components. [ABSTRACT FROM AUTHOR]

Concerns on health effects of radiofrequency (RF) signals have been discussed. Particularly, the effect on the central nerve system is one of main interest among the general public. So far, there are lots of studies regarding the RF effect on the Blood Brain Barrier (BBB), but no study of the RF effect on the Blood Cerebrospinal fluid Barrier (BCB). In this study we explored the effect on BCB function by radiofrequency electromagnetic fields (RF-EMF) exposure. To attain this purpose, we set about to make a real-time measuring system for BCB function using a micro-perfusion method and examined the short time exposure experiment using rats. Our data suggested the 30 min single exposure of 1.5 GHz RF-EMF at the brain average SARs of 9.5 W/kg for adult and 10.4 W/kg for juvenile, did not affect BCB function in rats under the experimental conditions. [ABSTRACT FROM AUTHOR]

Objectives. Public health concern about the health effects of radio-frequency electromagnetic fields (RF-EMFs) has increased with the increase in public exposure. This study was to evaluate some health effect of RF exposure by the AM radio broadcasting towers in Korea. Methods. We calculated cancer mortality rates using Korean death certificates over the period of 1994–1995 and population census data in ten RF-exposed areas, defined as regions that included AM radio broadcasting towers of over 100 kW, and in control areas, defined as regions without a radio broadcasting tower inside and at least 2 km away from the towers. Results. All cancers-mortality was significantly higher in the exposed areas [direct standardized mortality rate ratio (MRR) =1.29, 95%CI=1.12–1.49]. When grouped by each exposed area and by electrical power, MRRs for two sites of 100 kW, one site of 250 kW and one site of 500 kW, for all subjects, and for one site of 100 kW and two sites of 250 kW, for male subjects, showed statistically significant increases without increasing trends according to the groups of electric power. Leukemia mortality was higher in exposed areas (MRR=1.70, 95% CI=0.84–3.45), especially among young adults aged under 30 years (0–14 years age group, MRR=2.29, 95% CI=1.05–5.98; 15–29 age group, MRR=2.44, 95% CI=1.07–5.24) . Conclusions. We observed higher mortality rates for all cancers and leukemia in some age groups in the area near the AM radio broadcasting towers. Although these findings do not prove a causal link between cancer and RF exposure from AM radio broadcasting towers, it does suggest that further analytical studies on this topic are needed in Korea. [ABSTRACT FROM AUTHOR]

Radio-frequency thermokeratoplasty (RF-TKP) is a technique used to reshape the cornea curvature by means of thermal lesions using radio-frequency currents. This curvature change allows refractive disorders such as hyperopia to be corrected. A new electrode with ring geometry is proposed for RF-TKP. It was designed to create a single thermal lesion with a full-circle shape. Finite element models were developed, and the temperature distributions in the cornea were analysed for different ring electrode characteristics. The computer results indicated that the maximum temperature in the cornea was located in the vicinity of the ring electrode outer perimeter, and that the lesions had a semi-torus shape. The results also indicated that the electrode thickness, electrode radius and electrode thermal conductivity had a significant influence on the temperature distributions. In addition, in vitro experiments were performed on rabbit eyes. At 5 W power, the lesions were fully circular. Some lesions showed non-uniform characteristics along their circular path. Lesion depth depended on heating duration (60% of corneal thickness for 20 s, and 30% for 10 s). The results suggest that the critical shrinkage temperature (55-63 degrees C) was reached at the central stroma and along the entire circular path in all the cases. [ABSTRACT FROM AUTHOR]

SAR distributions were measured in the CDRH phanton, a 1 cm fatequivalent shell filled with an abdomen-equivalent liquid (σ=0.4−1.0 S m; dimensions 22×32×57 cm) to demonstrate the feasibility of the ring applicator to obtain deep heating. The ring electrodes were fixed in a PVC tube; diameter 48 cm, ring width 20 cm and gap width between both rings 31.6 cm. Radio-frequency energy was fed to the electrodes at eight points. The medium between the electrodes and the phantom was deionised water. The SAR distribution in the liquid tissue volume was obtained by a scanning E-field probe measuring the E-field in all three directions. With equal amplitude and phase applied to all feeding points, a uniform SAR distribution was measured in the central cross-section at 30 MHz. With RF energy supplied to only four adjacent feeding points (others were connected to a 50 ω load), the feasibility to perform amplitude steering was demonstrated; SAR values above 50% of the maximum SAR were measured in one quadrant only. SAR distributions obtained at 70 MHz showed an improved focusing ability; a maximum at the centre exists for an electric conductivity of the abdomen-equivalent tissue of 0.6 and 0.4 S m. [ABSTRACT FROM AUTHOR]