Internal RF Research Articles

Indigenous Development of MIC-Based C-Band Dual Chain Down Converter Unit for GEOSAT- Spacecraft Checkout System

As part of miniaturization, the development work for the C-band dual-chain down converter, which is extensively used in TM (Telemetry) data acquisition system in GEOSAT spacecraft checkout system has been taken up in MIC (Microwave Integrated Circuit) approach using microstrip line structure. A prototype unit is realized using standard surface mount devices (SMD) and few indigenously developed MIC components namely, the directional couplers, the power dividers etc. The MIC-based down converter module, which forms the heart of the unit is housed in an Aluminium milled box having the dimension of 150 x 150 x 25 mm3. Except internal Local Oscillator (LO), RF Switches and Power supply, all other circuitry are mounted withinthis milled box which is housed in 1U chassis. It meets all the requirements of a conventional down converter. The paper describes the salient features of the unit, its detailed design approach and realization plan and finally the test and evaluation results of the prototype unit developed indigenously.

Factors Influencing the Fluctuation Amplitude of the H− Ion Beam Extracted from an RF Wave Excited Ion Source Plasma

The beam oscillation of J-PARC ion source is being studied as AC electric field at 2 MHz ion source driving frequency can directly change the extraction characteristics of both H− ions and electrons. The internal RF antenna inducing the electric field generated two peaks of plasma production during one RF cycle as confirmed by 4 MHz modulation of Balmer-alpha (Hα) emission intensity. The coupling between the plasma production at 4 MHz and the oscillation of the local plasma potential in the vicinity of the extraction hole at 2 MHz can cause 6 MHz oscillation, which was observed in the measurement of extraction current from the ion source. Phase-delay of Hα intensities from the source plasma and those of the extraction electron current were compared with the RF input signal to the amplifier.

Publisher Erratum: Physical design of a high-intensity compact D–D/D–T neutron generator based on the internal antenna RF ion source

Publisher Erratum: Physical design of a high-intensity compact D–D/D–T neutron generator based on the internal antenna RF ion source

Effect due to Cs injection upon current oscillation of the beam extracted from the J-PARC negative hydrogen ion source

A high-speed emittance measurement system installed at the J-PARC RF negative hydrogen (H-) ion source test stand can construct emittance diagrams of the beam of a specific frequency component. The driving 2 MHz RF power produces small amplitude oscillating components at 2 MHz and at higher harmonic frequencies in the total H- ion beam detected by a Faraday installed downstream of the emittance measurement system. Magnitudes of oscillating component at 2 MHz and 4 MHz frequencies become appreciable as the slits of the emittance measurement system separate the H- ion beam into the position/angle resolved phase space elements. The reconstructed emittance diagrams of H- ion beams for the operation condition with continuous supply of Cs realizing large H- ion current to total extraction current ratios indicate that 2 MHz and 4 MHz frequency oscillating beam components propagate surrounding the center DC beam. Both 2 MHz and 4 MHz oscillating beam components comprise two to three beam particle groups in the phase space. The DC component of the H- ion beam exhibit a single peak in the angular distribution. Meanwhile, oscillating components often take the minima where the DC H- ion beam takes the maximum in the angular distribution diagram. Thus, the regions that produce large amplitude oscillations of the H- ion beam are considered located at the circumference of the beam extraction aperture. One possible explanation for observing larger amplitude beam oscillation can be the enhanced H- ion surface production at the plasma facing the wall of the beam extraction aperture. The operation without the Cs delivery to the source increased electron current coextracted with H- ions and changed the structure of the beam emittance diagram. In the direction perpendicular to the magnetic fields created by a magnetic filter and electron suppression magnets, the peak of the 4 MHz oscillating beam components appeared at the center of the DC beam. This observation suggests the extraction of H- ions formed in the central region by the volume production process near the internal RF antenna. Mechanisms that can excite and diminish the beam fluctuation amplitudes of the extracted H- ion beam are discussed.

Physical design of a high-intensity compact D–D/D–T neutron generator based on the internal antenna RF ion source

Physical design of a high-intensity compact D–D/D–T neutron generator based on the internal antenna RF ion source

Optical design and stray RF investigation of ITER EC H&CD equatorial launcher using mockup

The aim of this study is to assess power transmission characteristics of ITER EC H&CD equatorial launcher (EL) which will deliver 20 MW of millimeter wave power to the ITER tokamak. A precise optical mockup of the launcher is fabricated in order to experimentally verify the characteristics of 170 GHz beam transmission. To observe the intensity distribution of output beams, a mobile high-sensitivity power detection system is used for millimeter wave monitoring, which is in good agreement with quasi-optical calculations. Internal stray RF generation presents an additional concern regarding heat load inside the launcher especially in case of deteriorated input mode purity. Therefore, firstly, the stray RF power is quantified by observation after the beam duct (i.e., launcher exit) of the mockup. The results show that a significant portion of stray RF (>20%) is emitted and does not contribute to the heat load. For another approach to estimate the heat load, geometric optics is performed with various degrees of scattering. This approach indicates that nearly half of the stray RF power is emitted from the launcher exit. Thus, the internal heat load due to stray RF is calculated 44 kW/m2, which is an important result in relaxing the design conditions of the EL.

High power solid state RF amplifiers for SARAF Phase II Linac

Compact narrow-band high power Solid State Power Amplifiers (SSPA) capable of delivering up to 10/20 kW CW RF power at 176 MHz were developed at SNRC for SARAF Linac Phase II. The 10/20 kW amplifiers were built by combining RF power from two/four 5 kW high power amplifiers using 3 dB 0–90° High Power Quad Hybrid Couplers (HPQHC). In their turn, the 5 kW amplifiers were combined from eight LDMOS water cooled amplifiers modules equipped with internal circulators and RF loads. The total power gain of the 10/20 kW amplifiers (including the driver stages) is 70/73 dB. These amplifiers have the ability to withstand with continuous wave full reflection power (VSWR at nominal rating > 100:1) for a long time without the use of an external circulator. Unconditional stability for CW and pulsed operation, reliability, linearity, high efficiency, simple design and compact size are the main features we sought for this amplifier. The underlying design principles, indigenous development and test results are presented.

A Local Oscillator Phase Compensation Technique for Ultra-Wideband Stepped-Frequency Continuous Wave Radar Based on a Low-Cost Software-Defined Radio.

The paper discusses a way to configure a stepped-frequency continuous wave (SFCW) radar using a low-cost software-defined radio (SDR). The most of high-end SDRs offer multiple transmitter (TX) and receiver (RX) channels, one of which can be used as the reference channel for compensating the initial phases of TX and RX local oscillator (LO) signals. It is same as how commercial vector network analyzers (VNAs) compensate for the LO initial phase. These SDRs can thus acquire phase-coherent in-phase and quadrature (I/Q) data without additional components and an SFCW radar can be easily configured. On the other hand, low-cost SDRs typically have only one transmitter and receiver. Therefore, the LO initial phase has to be compensated and the phases of the received I/Q signals have to be retrieved, preferably without employing an additional receiver and components to retain the system low-cost and simple. The present paper illustrates that the difference between the phases of TX and RX LO signals varies when the LO frequency is changed because of the timing of the commencement of the mixing. The paper then proposes a technique to compensate for the LO initial phases using the internal RF loopback of the transceiver chip and to reconstruct a pulse, which requires two streaming: one for the device under test (DUT) channel and the other for the internal RF loopback channel. The effect of the LO initial phase and the proposed method for the compensation are demonstrated by experiments at a single frequency and sweeping frequency, respectively. The results show that the proposed method can compensate for the LO initial phases and ultra-wideband (UWB) pulses can be reconstructed correctly from the data sampled by a low-cost SDR.

Bipolar Radiofrequency as an Adjunct to Face and Body Contouring: A 745-Patient Clinical Experience.

Radiofrequency (RF) technology has ushered in a new paradigm in body contouring for patients with mild to moderate skin laxity who desire fat removal without exacerbating skin laxity issues. A bipolar internal RF device, used as an adjunct to liposuction, has been found to be simpler and more accurate than previous technologies. The aim of this study was to review the authors' clinical experience with bipolar RF-assisted liposuction (RFAL). We conducted a review of our large experience with bipolar RFAL, evaluating the nuances from appropriate patient selection and specific treatment areas. The review covered 745 patients treated from January 2017 to January 2020 at 2 centers. A retrospective chart review was performed of the first and last 50 patients treated at each center (for a total of 100 patients in each group) to assess trends in outcomes and adverse events. Results were generally excellent from physician evaluation, and overall patient satisfaction was high (96%). The two most common adverse events were temporary swelling (9%) and nodules (8.5%). Selected examples of a variety of cases are reviewed. The ability to tighten skin with a minimally invasive tool adds much to the contemporary approach to the body-contouring patient with skin laxity. Adverse events were minimal and greatly decreased after an initial short learning curve. Bipolar RFAL is a strong addition to our surgical armamentarium and has become an essential tool for our practices.

Soil organic carbon in peninsular Spain: Influence of environmental factors and spatial distribution

Soil organic carbon (SOC) stocks and their geographical distribution in peninsular Spain were estimated from a georeferenced database consisting of 12,724 surface samples (0–30 cm) and 3607 subsurface samples (30–50 cm), covering different climate, land use, elevation, parent material, soil type and soil pH. SOC density showed a high heterogeneity, with the lowest values in arid regions, where the average in topsoil ranged between 20 and 60 t C ha−1, under woody crops and forest respectively. Carbon stocks gradually increases as precipitation increases, and its variability is also dependent of other factors, fundamentally the presence/absence of active lime or active Al. In semi-arid zones, calcaric soils (pH ≈ 8.3) have higher contents of SOC than neutral to weakly acidic soils from siliceous materials. However, in humid regions, calcareous materials have undergo total or partial decarbonatation in the upper layer (pH < 4.0–7.5) and SOC stocks are markedly lower than in other materials. In forest soils it seems that a steady state (around 100–120 t C ha−1) (0–30 cm) has been reached in a wide range of precipitation, between 900 and 1700 mm; most of this carbon (about 80%) is labile-C. Soils from granitic rocks are acidic (pH 4.5–5.5) (Al buffering) and the mean SOC stock in the indicated precipitation range is between 170 and 200 t ha−1 (it is estimated that approximately 60% is stabilized as metal-C or mineral-C complexes). The highest values (190–240 t ha−1) are recorded in acidic soils derived from mafic rocks, which in these regions usually develop andic properties (around 73% is involved in stable metal-C or mineral C complexes). Finally, the SOC stored in neutral soils from serpentinized ultramafic rocks (without excess Ca or Al) is similar to that of the decarbonated soils derived from calcareous materials. In all regions, forest soils are a much more important SOC sink than live forest biomass (2–4 times higher in the upper 30 cm and 3–6 times greater in the upper 50 cm).Random Forest regression was used as modeling tool and digital mapping. Mean annual precipitation was estimated to be the most important predictor variable, followed by land use, lithology/soil type and soil pH. Model performance was calibrated by the internal RF validation and through cross-validation, and the results were similar. In topsoil, the mean error, root mean square error and R2 were −0.007% C, 1.48% C and 0.61, respectively. In the subsurface layer these indices were −0.020, 1.07 and 0.37, respectively. SOC stock for peninsular Spain was estimated at 3.33 Pg in the upper (0–30 cm) layer, and 0.85 Pg in the subsurface (30–50 cm) layer. Total SOC stock for 0–50 cm was 4.19 Pg, with a 95% confidence interval ranging between 3.33 and 5.03 Pg.

Precision Near-Field Reconstruction in the Time Domain via Minimum Entropy for Ultra-High Resolution Radar Imaging

Ultra-high resolution (UHR) radar imaging is used to analyze the internal structure of objects and to identify and classify their shapes based on ultra-wideband (UWB) signals using a vector network analyzer (VNA). However, radar-based imaging is limited by microwave propagation effects, wave scattering, and transmit power, thus the received signals are inevitably weak and noisy. To overcome this problem, the radar may be operated in the near-field. The focusing of UHR radar signals over a close distance requires precise geometry in order to accommodate the spherical waves. In this paper, a geometric estimation and compensation method that is based on the minimum entropy of radar images with sub-centimeter resolution is proposed and implemented. Inverse synthetic aperture radar (ISAR) imaging is used because it is applicable to several fields, including medical- and security-related applications, and high quality images of various targets have been produced to verify the proposed method. For ISAR in the near-field, the compensation for the time delay depends on the distance from the center of rotation and the internal RF circuits and cables. Required parameters for the delay compensation algorithm that can be used to minimize the entropy of the radar images are determined so that acceptable results can be achieved. The processing speed can be enhanced by performing the calculations in the time domain without the phase values, which are removed after upsampling. For comparison, the parameters are also estimated by performing random sampling in the data set. Although the reduced data set contained only 5% of the observed angles, the parameter optimization method is shown to operate correctly.

Dynamic magnetic susceptibility and electrical detection of ferromagnetic resonance

The dynamic magnetic susceptibility of magnetic materials near ferromagnetic resonance (FMR) is very important in interpreting the dc voltage obtained in its electrical detection. Based on the causality principle and the assumption that the usual microwave absorption lineshape of a homogeneous magnetic material around FMR is Lorentzian, the general forms of the dynamic magnetic susceptibility of an arbitrary sample and the corresponding dc voltage lineshapes of its electrical detection were obtained. Our main findings are as follows. (1) The dynamic magnetic susceptibility is not a Polder tensor for a material with an arbitrary magnetic anisotropy. The two off-diagonal matrix elements of the tensor near FMR are not, in general, opposite to each other. However, the linear response coefficient of the magnetization to the total radio frequency (rf) field (the sum of the external and internal rf fields due to precessing magnetization is a quantity which cannot be measured directly) is a Polder tensor. This may explain why the two off-diagonal susceptibility matrix elements were always wrongly assumed to be opposite to each other in almost all analyses. (2) The frequency dependence of dynamic magnetic susceptibility near FMR is fully characterized by six real numbers, while its field dependence is fully characterized by seven real numbers. (3) A recipe of how to determine these numbers by standard microwave absorption measurements for a sample with an arbitrary magnetic anisotropy is proposed. Our results allow one to unambiguously separate the contribution of the anisotropic magnetoresistance to the dc voltage signals from the anomalous Hall effect. With these results, one can reliably extract the information of spin pumping and the inverse spin-Hall effect, and determine the spin-Hall angle. (4) In the case that resonance frequency is not sensitive to the applied static magnetic field, the field dependence of the matrix elements of dynamic magnetic susceptibility, as well as the dc voltage, may have another non-resonance broad peak. Thus, one should be careful in interpreting the observed peaks.

Reverse factoring in the supply chain: objectives, antecedents and implementation barriers

Purpose Reverse factoring (RF) can generate win-win situations for buyers, banks and suppliers. However, the SCM literature generally tends to ignore financial influences and accounting support structures. Research in the area of reverse factoring is relatively new and considerably fragmented. To address this research gap this paper provides an analysis of the objectives, antecedents and barriers of implementation. Design/methodology/approach The study contributes fundamental new insights derived from eleven case studies. 28 interviews were conducted from the perspective of buyers, banks and suppliers and analyzed regarding influencing factors of different RF approaches. Findings Reverse factoring predominantly is used to extend days payable outstanding (DPO). However, secondary objectives such as the reduction of supplier default risk and process simplifications also play an important role. The number of integrated suppliers, dependence of suppliers on their buyers, spread between internal refinancing and RF costs and the diversity of target agreements strongly influence these objectives and therefore the configuration of RF solutions. Originality/value Most studies fall short of exploring the mechanism of reverse factoring from all of the different perspectives of buyers, banks and suppliers. This approach allows new insights regarding prerequisites and different motivations behind RF.

Digitally Assisted CMOS RF Detectors With Self-Calibration for Variability Compensation

In this paper, a technique of digitally assisted RF detectors with variability compensation is proposed. It enables the ability to obtain a high dynamic-range linear-in-dB characteristic with a small footprint. Digital assistance is used to correct for a nonlinear characteristic and to perform a self-calibration. In state-of-the-art CMOS RF systems-on-chip (SoCs), the digital capabilities required for this technique would not represent an overhead for the design, as they are already available. The self-calibration compensates for the process variability relying on internal dc measurements and statistical information derived from the statistical models provided by the foundry. This technique would benefit SoCs, which implement built-in self test or built-in self calibration by enabling multiple high dynamic-range internal RF measurements, while complying with tight area and power budgets. A proof-of-concept detector cell is presented in a 90-nm CMOS process, which provides a maximum linearity error of $\pm {\hbox{1.5 dB}}$ and a 33-dB dynamic range at 2 GHz after digital correction. The circuit occupies an area of ${\hbox{0.004 mm}}^{2}$ and consumes a maximum of ${\hbox{240-}}\mu{\hbox{A}}$ from a 1.2-V supply. The results are confirmed by measurements performed on ten samples.

Beam-loaded frequency shift study in an over-sized backward wave oscillator

The oversized backward wave oscillator (BWO) can significantly decreases the internal rf electric field in the device. The beam-loaded effect is obvious in such devices and its performance is also significantly affected. Based on the characteristics of the oversized BWO, a self-consistent equation is developed to study its beam-loaded frequency shift together with particle in cell (PIC) simulations. The mechanism whereby the output rf frequency is affected by the beam's parameters and the device's structure is theoretically studied. The frequency's dependence on the drift tube length between the reflector and SWS (slow wave structures) in the device is deduced in the paper and the theoretical results agree with those obtained in PIC simulations.

Electromagnetic assessment of embedded micro antenna for a novel sphincter in the human body

This paper presents a wireless, miniaturized, bi-directional telemetric artificial anal sphincter system that can be used for controlling patients' anal incontinence. The artificial anal sphincter system is mainly composed of an executive mechanism, a wireless power supply system and a wireless communication system. The wireless communication system consists of an internal RF transceiver, an internal RF antenna, a data transmission pathway, an external RF antenna and an external RF control transceiver. A micro NMHA (Normal Mode Helical Antenna) has been used for the transceiver of the internal wireless communication system and a quarter wave-length whip antenna of 7.75 cm has been used for the external wireless communication system. The RF carrier frequency of wireless communication is located in a license-free 433.1 MHz ISM (Industry, Science, and Medical) band. The radiation characteristics and SAR (Specific Absorption Rate) are evaluated using the finite difference time-domain method and 3D human body model. Results show that the SAR values of the antenna satisfy the ICNIRP (International Commission on Nonionizing Radiation Protection) limitations.

Current-induced synchronized switching of magnetization

We investigate current-induced magnetization switching for a multilayer structure that allows a reduced switching current while maintaining high thermal stability of the magnetization. The structure consists of a perpendicular polarizer, a perpendicular free-layer, and an additional free-layer having in-plane magnetization. When the current runs perpendicular to the structure, the in-plane free-layer undergoes a precession and supplies an internal rf field to the perpendicular free-layer, resulting in a reduced switching current for one current polarity. For the other polarity, the in-plane free-layer almost saturates perpendicular to the plane and acts as another perpendicular polarizer, which also reduces the switching current.

Radio Frequency Plasma Transition Caused by Gas Puffing and/or Direct Current Biasing Using Multiturn Internal Antenna

The transitions between capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) were investigated using chemical vapor deposition (CVD) plasma with the internal RF multiturn antenna. The typical electron densities of both 1015/m3 in CCP mode and 1017/m3 in ICP mode were measured, and the measured electron temperature profile was hollow in the CCP mode, which was in contrast to the broadened temperature profile in the ICP mode. Finally, we succeeded in controlling the RF plasma transition by changing the gas density and also by supplying the direct current (DC) voltage.

Behavior of Transition into Inductively Coupled Plasma Mode with Internal Radio Frequency Multiturn Antenna

The transition between capacitively coupled plasma (CCP) and inductively coupled plasma (ICP) was investigated using a chemical vapor deposition (CVD) system with an internal RF multiturn antenna. Repeated transitions were generated for the first time, but for a single standard transition. A single standard transition showed a flat threshold dependence on gas pressure (10–100 Pa) in Ar gas and a marked increase at approximately 1.5–8 Pa. On single standard transition, the amounts of increases in electron temperature and density induced by the transition into ICP were almost three fold and double figures higher, respectively. The time evolution of transition was 8 µs at 10 Pa, which became longer with an increase in gas pressure in inverse proportion to electron temperature and density. The trigger of the sudden transition to the ICP mode from the CCP mode was considered to be due to the increase in electron temperature.

Crystal structure, stability and in vitro RNAi activity of oligoribonucleotides containing the ribo-difluorotoluyl nucleotide: insights into substrate requirements by the human RISC Ago2 enzyme

Short interfering RNA (siRNA) duplexes are currently being evaluated as antisense agents for gene silencing. Chemical modification of siRNAs is widely expected to be required for therapeutic applications in order to improve delivery, biostability and pharmacokinetic properties. Beyond potential improvements in the efficacy of oligoribonucleotides, chemical modification may also provide insight into the mechanism of mRNA downregulation mediated by the RNA–protein effector complexes (RNA-induced silencing complex or RISC). We have studied the in vitro activity in HeLa cells of siRNA duplexes against firefly luciferase with substitutions in the guide strand of U for the apolar ribo-2,4-difluorotoluyl nucleotide (rF) [Xia, J. et al. (2006) ACS Chem. Biol., 1, 176–183] as well as of C for rF. Whereas an internal rF:A pair adjacent to the Ago2 (‘slicer’ enzyme) cleavage site did not affect silencing relative to the native siRNA duplex, the rF:G pair and other mismatches such as A:G or A:A were not tolerated. The crystal structure at atomic resolution determined for an RNA dodecamer duplex with rF opposite G manifests only minor deviations between the geometries of rF:G and the native U:G wobble pair. This is in contrast to the previously found, significant deviations between the geometries of rF:A and U:A pairs. Comparison between the structures of the RNA duplex containing rF:G and a new structure of an RNA with A:G mismatches with the structures of standard Watson–Crick pairs in canonical duplex RNA leads to the conclusion that local widening of the duplex formed by the siRNA guide strand and the targeted region of mRNA is the most likely reason for the intolerance of human Ago2 (hAgo2), the RISC endonuclease, toward internal mismatch pairs involving native or chemically modified RNA. Contrary to the influence of shape, the thermodynamic stabilities of siRNA duplexes with single rF:A, A:A, G:A or C:A (instead of U:A) or rF:G pairs (instead of C:G) show no obvious correlation with their activities. However, incorporation of three rF:A pairs into an siRNA duplex leads to loss of activity. Our structural and stability data also shed light on the role of organic fluorine as a hydrogen bond acceptor. Accordingly, UV melting (TM) data, osmotic stress measurements, X-ray crystallography at atomic resolution and the results of semi-empirical calculations are all consistent with the existence of weak hydrogen bonds between fluorine and the H-N1(G) amino group in rF:G pairs of the investigated RNA dodecamers.