RF Lines Research Articles

Rotary encoding for intravascular ultrasonic imaging systems

Images produced with an intravascular ultrasound system (IVUS) can be distorted because of uncertainty in the instantaneous angular position of a rotating ultrasonic transducer. A rotary encoder placed in proximity to the transducer is required to detect the problem; however, size constraints make a conventional electromechanical or optomechanical encoder difficult to implement. Measurements that test the feasibility of a software-derived encoder, based of the rate of decorrelation of ultrasonic RF lines with angle, are reported. Provided that the instantaneous angular velocity of the transducer can be measured, adjustments can be made to the pulse rate of the transducer, which would eliminate the image distortion.

High-frequency estimation of the ultrasonic attenuation coefficient slope obtained in human skin: simulation and in vivo results

In vivo ultrasonic characterization of the skin was performed at 40 MHz by estimating the slope of the attenuation coefficient in the human dermis. The centroid algorithm was first tested on simulated backscattered RF lines with a second-order autoregressive model to carry out the spectral analysis. A relative error of less than 8.5% and a relative precision of less than 6% were predicted for a 2-mm tissue thickness and for temporal window sizes ranging from 0.25 to 0.45 micros. In vivo measurements performed on 138 healthy volunteers yielded values of the attenuation coefficient slope ranging from 0.8 to 3.6 dB/cm MHz. A decrease was observed with advancing age, but no significant difference appeared between men and women. The results from this study suggest that this acoustic parameter shows the effect of the ageing process on normal skin tissue in vivo.

Synchronisation of subterahertz optical pulse trainfromPLL-controlled colliding pulse modelocked semiconductor laser

The synchronisation of a 192 GHz optical pulse train, generated from a colliding pulse modelocked laser diode, to an electrical signal is successfully demonstrated by a phase-locked loop that uses optical modulation sidebands. The synchronisation is confirmed by a synchro-scan streak camera and the timing jitter is estimated to be 0.6 ps from the RF line spectrum of the beat note between the high-order sidebands generated by 40 GHz electroabsorption modulation.

3.5 mm coaxial power standard

A 3.5 mm twin line coaxial calorimeter is the first microwave power calorimeter in this line size to be constructed at the National Physical Laboratory. The instrument consists of two terminated coaxial lines with a length of high thermal resistance line between an APC-3.5 mm input connector and a tractorial load. The principle of operation is to measure RF power dissipated in one of the loads in terms of DC power dissipated in the other load. A temperature change due to the dissipation of power is detected by platinum resistance thermometers (PRTs) fixed on the coaxial line in the region of the load. Two PRT sensors connected in series on both sides of each coaxial line are incorporated in an AC bridge and detection circuit. Initially the output from the detection circuit is zero but once power is applied to the RF line the bridge goes out of balance. This signal is then used to control a feedback voltage to the DC line until the bridge output is returned to zero. The final DC feedback voltage that balances the bridge is then used to determine the RF power to the calorimeter. The instrument operates over the frequency range DC to 26.5 GHz at power levels 0.1–10 mW. The calculated effective efficiency for the calorimeter ranges from 102.4% at 0.1 GHz to 99.3% at 26.5 GHz. The VSWR of the RF line ranges from 1.006 at 1 GHz to 1.06 at 26.5 GHz with a maximum of 1.12 at 25.1 GHz.

Line-loss and size reduction techniques for millimeter-wave RF front-end boards by using a polyimide/alumina-ceramic multilayer configuration

This paper proposes a concept for constructing low-loss and small-size millimeter-wave RF front-end boards by using a polyimide/alumina-ceramic multilayer configuration. The thick polyimide layer enables us to design low-loss wide microstrip lines (MS's). Moreover, the board size can be reduced by compactly arranging all RF and dc lines in the intermediate layers of the polyimide/alumina-ceramic substrate. The size of a prototype board designed for the quasi-millimeter-wave region is 30 mm/spl times/30 mm. In experiments, it showed 23.2-dB linear gain and 7.4-dBm P/sub -1/ RF output power in transmitter (TX) mode, and 3.1-dB linear gain and -20.1-dBm P/sub -1/ IF output power in receiver (RX) mode. These performance levels agree well with predicted values. This paper further discusses applications to the integration of passive circuits fabricated in the substrate. The proposed configuration has enough potential to integrate all monolithic microwave integrated circuit (MMIC) chips, dc-bias integrated circuits (IC's), and passive circuits, and can improve the total performance in terms of the RF characteristics, board size, and fabrication cost.

Plant Regeneration through Anther Culture and Induced Parthenogenesis in Genus Helianthus

ABSTRACTTwo possibilities, based on the androgenic and gynogenic approach for development of haploid plants in vitro, were studied in the Genus Helianthus. Six F1 interspecific hybrids between the wild species H.decapetalus, H.hirsutus, H.rigidus, H.mollis, H.eggertii and H.laevigatus, and the cultivated H. animus L. have been used as donor plants for anther culture. Anthers were plated on two different callus induction media: AA medium (Alissa et al., 1985) and mod. L4M medium (Lenee P. and Chupea Y., 1985). Depending on the genotype callus induction occurred in a range of 50–100% on the mod. L4M medium and 15–60% on the AA medium. Plant regeneration and shoot multiplication were observed in the F1 hybrids of H.eggertii, H.mollis, H.decapetalus and H.rigidus after the third transfer of the calluses on the B5 hormone free medium (Chandler and Beard, 1983). For inducing gynogenic development 8 wild sunflower species (H. decapetalus, H. hirsutus, H.rigidus, H. eggertii, H. laevigatas, H. ciliaris, H. x laetiflorus and H. strumosus), were pollinated with inactivated through gamma—irradiation pollen of Rf line 147. The formed embryos were cultured in vitro. Seven plants of the variant H.x laetiflorus x Rf 147, where the pollen were treated with 600 Gy gamma rays, were grown in greenhouse.

Introduction of a gene from fertility restored radish (Raphanus sativus) into Brassica napus by fusion of X-irradiated protoplasts from a radish restorer line and iodacetoamide-treated protoplasts from a cytoplasmic male-sterile cybrid of B. napus

To establish a cytoplasmic male-sterile/restored fertility (cms-Rf) system for F1 seed production in Brassica napus, we transferred a gene from fertillity restored radish to B. napus by protoplast fusion. X-irradiated protoplasts, isolated from shoots of Raphanus sativus cv Kosena (Rf line), were fused with iodoacetamide-treated protoplasts of a B. napus cms cybrid. Among 300 regenerated plants, six were male-fertile. The fertile plants were characterized for petal color, chromosome number and the percentage of viable pollen grains. Three fertile plants had aneuploid chromosome numbers and white or cream petals, which is a dominant marker in radish. Of these three plants, one which had 2n = 47 chromosomes and white petals was used for further backcrosses. After two backcrosses, chromosome number and petal color became identical to that of B. napus. No female sterility was observed in the BC3 generations.

Penetration depth and critical current in NbN resonators: predicting nonlinearities and breakdown in microstrip

Parallel plate and microstrip resonator experiments show that NbN films have large magnetic penetration depth and a peak RF critical current density which either matches or exceeds the DC critical current density, depending on the temperature. The large penetration depth, /spl lambda/, suggests that narrow NbN transmission lines will have increased inductive nonlinearities, when compared with other superconductors. The relation between the DC and peak RF critical current densities indicates that by modeling the RF current distribution a simple DC breakdown measurement can be used to estimate a transmission line's RF current carrying capacity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A novel topical probe for MRI: the flat, truncated line probe.

The construction and imaging characteristics of flat, truncated line probes (FTLPs) are described here. These probes illustrate a novel design of local probes for magnetic resonance imaging, with four major differences from conventional loop surface probes: (1) The B1 fields are directed perpendicular to the usual loop probes' direction. (2) The RF fringe electric fields are inherently shielded, which allows reduced loading from electrically lossy samples. (3) The homogeneity across the plane of the probe can be adjusted locally. And (4) when not used with tuning and matching circuits, a probe's local impedance can be set to match the RF line impedance. The probes are, in essence, a single loop significantly flattened with the outside conductor (away from the imaged object) wider than the inside conductor (against the imaged object). The probes are shaped so as to provide a homogeneous signal across the plane area of the probe. The signal intensity drops off faster than a loop of the same size. With a minimally loading phantom, along the midline normal to the surface, the S/N at the surface region is approximately 20% greater than a commercial probe (Phillips R2) of the same area dimensions, while at 5 cm depth, the S/N is lower. However, when used for imaging a body--again along the midline normal to the probe--the S/N at 5 cm depth is equal, and rises to approximately twice that of the Philips R2 probe at the surface.

Estimation of in Vivo Pulses in Medical Ultrasound

An algorithm for the estimation of one-dimensional in-vivo ultrasound pulses is derived. The routine estimates a set of ARMA parameters describing the pulse and uses data from a number of adjacent rf lines. Using multiple lines results in a decrease in variance on the estimated parameters and significantly reduces the risk of terminating the algorithm at a local minimum. Examples from use on synthetic data confirms the reduction in variance and increased chance of successful minimization termination. Simulations are also reported indicating the relation between the one-dimensional pulse and the three-dimensional, attenuated ultrasound field for a concave transducer. Pulses are estimated from in-vivo liver data showing good resemblance to a pulse measured as the response from a planar reflector and then properly attenuated. The main application for the algorithm is to function as a preprocessing stage for deconvolution algorithms using parametric pulses.

Estimation of in vivo pulses in medical ultrasound.

An algorithm for the estimation of one-dimensional in-vivo ultrasound pulses is derived. The routine estimates a set of ARMA parameters describing the pulse and uses data from a number of adjacent rf lines. Using multiple lines results in a decrease in variance on the estimated parameters and significantly reduces the risk of terminating the algorithm at a local minimum. Examples from use on synthetic data confirms the reduction in variance and increased chance of successful minimization termination. Simulations are also reported indicating the relation between the one-dimensional pulse and the three-dimensional, attenuated ultrasoud field for a concave transducer. Pulses are estimated from in-vivo liver data showing good resemblance to a pulse measured as the response from a planar reflector and then properly attenuated. The main application for the algorithm is to function as a preprocessing stage for deconvolution algorithms using parametric pulses.

Nonparametric estimation of ultrasound pulses.

An algorithm for nonparametric estimation of 1-D ultrasound pulses in echo sequences from human tissues is derived. The technique is a variation of the homomorphic filtering technique using the real cepstrum, and the underlying basis of the method is explained. The algorithm exploits a priori knowledge about the structure of rf line echo data and can employ a number of adjacent rf lines from an image. The prime application of the algorithm is to yield a pulse suitable for deconvolution algorithms. This will enable these algorithms to properly take into account the frequency dependence of the attenuation and its variation within a patient and among patients. It is also possible to use the estimated pulse for attenuation estimation, and the consistency of the assumptions underlying the proposed technique is demonstrated by its ability to recover low variance attenuation estimates in the normal liver from in vivo pulse-echo data. Estimates are given for eight different patients.

Propagation Characteristics and Mode Utilizability of Electromagnetic RF and Optical Surface Waves Travelling between a Pair of Metal Sheets

Several characteristic features of electromagnetic (EM) surface waves propagating between a pair of planar conductors are disclosed analytically along with the other normal EM modes. The solutions are obtained on the basis of electron plasma oscillation in metals. The results are summarized as follows: (I) there exist primarily two independent surface waves (or optical surface waves), even and odd surface modes; (II) the odd surface mode (SWo) becomes a pure transverse electromagnetic (TEM) wave in the limiting case of an infinite value of electron density in metals; and (III) the even surface mode (SWe) will smoothly change to the even TM1e mode at a certain point of the dispersion curve. Utilizability of the lower modes is discussed for very-high-frequency RF and optical wave transmission lines and for long or large-area plasma production between planar electrodes.

The Sagittarius B2 star-forming region - Subarcsecond radio spectral line and continuum observations

Results are reported of a subarcsecond spatial resolution RF line and continuum study of the Sgr B2 region, observed at the frequency of the 76-alpha hydrogen recombination line and at the (J,K = 3,2) transition of NH3. Also reported are new observations of the ground-state OH main line masers toward Sgr B2 in both left and right circular polarization. The continuum images showed no less than 19 separate H II regions in the Sgr B2 complex. Ammonia emission was observed in the Sgr B2 K and F regions. The emission toward K was found near the K1, K2, and K3 regions. The NH3 emission and absorption toward the F region, along with the OH maser emission, delineate a rotating disk or torus of molecular material surrounding the Sgr B2 F complex of H II regions. The mass interior to the NH3 and OH emission regions was calculated to be on the order of 1400 solar masses. 38 refs.

Alloplasmic male sterility in AD allotetraploid Gossypium hirsutum upon replacement of its resident A cytoplasm with that of D species G. harknessii

Alloplasmic male sterile (cms) and restoration-of-fertility (Rf) lines of the AD allotetraploid Gossypium hirsutum were earlier derived from the presumed introgression of the cytoplasm of the D species G. harknessii. To confirm that this happened and address its significance, cytoplasms of the maternal progenitor, backcross intermediates, derived breeding lines, related A, D, and F species, and a synthetic AD tetraploid were examined by agarose and polyacrylamide gel electrophoresis of 140 restriction enzyme fragments of chloroplast DNA. Length mutations of 10-50 nucleotides predominate over site loss/gain mutations. Chloroplast DNA is maternally inherited and that of G. harknessii has been maintained in the cms lines for at least 13 successive generations without detectable alteration. Chloroplast DNA divergence is consistent with current nuclear genome classification and shows that the A progenitor was the maternal parent of the AD tetraploids. As predicted from incompatability models of cms, the degree of male sterility in alloplasmic Gossypium tetraploids is correlated with the extent of evolutionary divergence of their cytoplasms. It is suggested that the A genome in the AD tetraploids dominates those nuclear-cytoplasm interactions reflected by male fertility.

Radio frequency performance of an HVDC converter station AC Switchyard

Abstract The propagation of HVDC converter station generated RF signals through a 345 kV AC switchyard to injection on the AC lines has been examined. A one-line analytical model of the AC buses, yard equipment and converter transformers has been formulated based upon measured RF impedances. The calculations were compared with relative measurements of RF line currents as different filter banks were switched in and out. The results indicate that the model will be a promising means of analysis and mitigation of unwanted RF effects. Phase-to-phase coupling and extension of the approach to a three-line model have been considered but absolute RF measurements would be required prior to any definitive assessment.

Noise current measurements and signal-to-noise improvement in low-temperature, low-frequency nuclear-magnetic-resonance experiments

A NMR pickup coil cooled to low temperature generates virtually no noise. Advantage can be taken of this fact in the low megahertz range by proper design and, in particular, by taking the current noise sources in of the room-temperature input circuitry carefully into account. A low-noise rf line and a method to measure very small in’s in the 10-kHz–1-MHz frequency range are described.

Two-spark-gap RF line generator with improved performance

The design of the two-spark-gap RF line generator is modified by including small inductors in series with the initially uncharged capacitors. These inductors balance the effect of the parasitic inductances associated with the spark gaps and the plate connections. The modified line generator more closely approximates a uniform lumped transmission line and hence improved performance is achieved because of the reduction in partial reflections at each LC section of the line. A 16-period line generator has been constructed to be used in plasma physics experiments. The optimum value of the balancing inductors for this line was calculated numerically. The current pulses obtained from this line generator, with and without the balancing inductors, are presented.

A high-power RF line generator of novel design

A modification of the Weibel radio frequency line generator is described. The modification substantially reduces the necessary number of spark gap switches and yields both a significant saving in construction costs and a greater ease of construction and reliability of operation. The construction and performance of an eight-period line generator incorporating this design modification are described. The equivalent root mean square open-circuit voltage and generator impedance are 14.1 kV and 9.7 Omega .

COMBINING ABILITY FOR MALE FERTILITY AND YIELD IN HYBRID WINTER WHEAT

Sixty-seven F1 winter wheat hybrids (Triticum aestivum) between eight cytoplasmic male sterile (cms) lines with T. timopheevi cytoplasm and 10 fertility restoration (Rf) lines carrying restoration genes from T. timopheevi, T. spelta and T. aestivum ’Primepi’ were analyzed for male sterility and grain yield in a field trial. Both male and female parents showed wide differences in the male fertility and yield of their hybrid arrays. However, the parental effects were largely additive. Two cms lines 8780 E5 and Mironovskaya 808 were outstanding for ease of restoration compared to several soft white winter wheat cultivars. Mironovskaya 808 also showed high combining ability for yield. The two best restored hybrids had 96% male fertility.