Output Branches Research Articles

THE DESIGN OF A NOVEL COMPACT ULTRA-WIDEBAND (UWB) POWER DIVIDER

The design of a compact coplanar power divider with novel structure is presented by making a full use of the theories of microstrip-to-slotline transition. To obtain two in-phase signals over a wide frequency range, the two output branches are placed in the same layer. Moreover, a half-wavelength slotline is employed to expand the working frequency range. The presented compact power divider shows a low insertion and good return loss performance at input port. The simulated and measured results have shown a good agreement over the frequency range 2.2GHz{11GHz.

Integrated Broadband Polarization Splitters Made by Ion-Exchange on Glass

In this letter, we present the design, fabrication, and characterization of a broadband polarization splitter working in the 1550-nm transmission window. The device is an asymmetric Y-junction realized by Ag <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> /Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ion exchange on glass. The transverse electric (TE) output branch of the device filters out the residual transverse magnetic (TM) mode by radiation. Measurements show cross-talks better than (31.1±0.4) dB in TE and better than (32.7±0.4) dB in TM mode over a 70-nm bandwidth limited by the characterization source. Optimal values of, respectively, (33.6±0.4) dB and (37.2±0.4) dB were measured at 1540 nm. At this wavelength, the insertion losses are, respectively, (6.0±0.4) dB and (5.5±0.4) dB in TE and TM modes while the function losses are (0.65±0.12) dB and (0.35±0.12) dB, respectively.

Photonic-assisted approach for instantaneous microwave frequency measurement with tunable range by using Mach-Zehnder interferometers

A novel photonic-assisted approach to microwave frequency measurement is proposed and experimentally demonstrated. The proposed scheme is based on the frequency-to-power mapping with different transmission responses. A polarizer is used in one output branch of a phase modulator to simultaneously implement phase modulation and intensity modulation. Owing to the complementary nature of the transmission responses and the Mach-Zehnder interferometers (MZIs), this scheme theoretically provides high resolution and tunable measurement range. The measurement errors in the experimental results can be kept within 0.2 GHz over a frequency range from 0.1 to 5.3 GHz.

Robot-assisted renal artery aneurysm repair with a saphenous vein Y-graft interposition

Renal artery aneurysms (RAA) treatment includes both surgical repair and endovascular techniques, mostly depending on the location of aneurysm. For complex RAA located at renal artery bifurcation or distally, open surgical repair represents the gold standard of treatment. However, the transperitoneal open access to the renal artery requires a wide laparotomy--hence the attempt to be minimally invasive with the first reports of laparoscopic approach. Even if it represents a possibility, laparoscopy has not yet gained widespread acceptance for the technical difficulties in performing vascular anastomosis. We herein describe the repair of a complex RAA using the Da Vinci Surgical System. A 41-year-old woman had an accidentally discovered saccular aneurysm of the right renal artery with a maximum diameter of 20 mm, with one in and four out. A laparoscopic robot-assisted approach was planned. Intraoperatively, we confirm the strategy to group the four output branches in two different patches. Thus, a Y-shaped autologous saphenous graft was prepared and introduced through a trocar. For the three anastomoses, a polytetrafluoroethylene running suture was preferred. The total operation time was 350 min, and the estimated surgical blood loss was about 200 ml. Warm ischemia time was 58 min for the posterior branch and 24 min for the second declamping. The patient resumed a regular diet on postoperative day 2, and the hospital stay lasted 4 days. No intraoperative or postoperative morbidity was noted. A CT scan performed 2 months later revealed the patency of all the reconstructed branches. The experience of our group counts five other renal aneurysm repair performed with a robot-assisted technique. The presence of five different arterial branches involved in the reconstruction makes this procedure difficult. Robot-assisted laparoscopic technique represents a valid alternative to open surgery in complex cases.

Spin polarization of entangled and mixed electron states in a beam splitter geometry coupled to an electron reservoir

We study the spin polarization of mixed and entangled electron states in a four probe/beam splitter geometry with local Rashba and Dresselhaus interactions. A pair of maximally entangled electrons collides with the beam splitter and enters into two perpendicular branches of length L, composed of spin-orbit active materials (gate confined 2D electron gas). One of the branches is connected to an electron reservoir that acts as a source of decoherence by either behaving as a voltage probe or as a controlled source or sink of current at fixed voltage. Such decoherence source is used to modify the entropy of an unpolarized incoming state in order to generate electron polarization at one or both output branches. The degree of entanglement of the global state and the spin polarization is computed for the outgoing electrons as a function of the coupling to the electron reservoir. Experimentally available spin-orbit strength at the beam splitter arms, for arm lengths of a few micrometers, is able to modulate spin polarization up to 80% in particular spin axes proportional to the decoherence current. The Dresselhaus and Rashba coefficients play a symmetric role in modulating the polarization. Significantly less polarization is achieved for incoming mixed states due to the local operation of the reservoir.

T- and Y-splitters based on an Au/SiO2 nanoring chain at an optical communication band

In this paper, we have utilized Au nanoring chains in an SiO2 host to design certain T-and Y-structures, and expanded it to transport and split the electromagnetic energy in integrated nanophotonic devices operating at an optical communication band (λ≈1550 nm). We compared two structures and tried to choose the best one, with lower losses and higher efficiency at the output branches, in order to split and transport the optical energy. Comparing the different types of nanoparticles corroborates that nanorings have an extra degree of tunability in their geometrical components. Meanwhile, nanorings show strong confinement in near-field coupling, less extinction coefficient, and also lower scattering into the far field during energy transportation at the C-band spectrum. Due to the nanoring's particular properties, transportation losses would be lower than in other nanoparticle-based structures like nanospheres, nanorods, and nanodisks. We demonstrate that Au nanorings surrounded by an SiO2 host yield suitable conditions to excite surface Plasmons inside the metal. Comparison between Y-and T-splitters shows that the Y-splitter is a more suitable alternative than the T-splitter, with higher transmission efficiency and lower losses. In the Y-structure, the power ratio (time-averaged power across the surface) is 24.7%, and electromagnetic energy transportation takes place at group velocities in the vicinity of 30% of the velocity of light; transmission losses are γT=3 dB/655 nm and γT=3 dB/443 nm. In this work, we have applied the finite-difference time-domain method (FDTD) to simulate and indicate the properties of structures.

Synthesis of n-way active topology for wide-band RF/microwave applications

A novel architecture of n-way active topology for RF/microwave module applications is developed. This architecture is based on the use of active cell composed of a field effect transistor (FET) in cascade with shunt resistor. A theoretic analysis illustrating the S-parameters calculation was established. The expressions of the n-way power divider output gains were demonstrated. A synthesis method of active power-splitter or/and 180° balun in function of the considered FET stage number constituting each outer branch was proposed. A simple active power-splitter was designed using an even number of FET between the input–output branches. In addition, a variable gain active power-splitter was simulated. The FETs are biased at Vds = 6 V and Ids = 25 mA. So, insertion losses above −1.5 dB, return losses better than −15 dB and excellent isolation below −30 dB at all three ports were obtained from 0.5 to 5.5 GHz. Using odd number of FET stage, an active balun was realised. Then, simulations of active balun showing a perfectly constant differential out-phase (180° ± 5°), insertion losses above −1.5 dB and an excellent isolation below −30 dB for all three ports, from 0.3 to 4.5 GHz were performed.

A novel low voltage very low power CMOS class AB current output stage with ultra high output current drive capability

In this paper a novel low voltage (LV) very low power (VLP) class AB current output stage (COS) with extremely high linearity and high output impedance is presented. A novel current splitting method is used to minimize the transistors gate–source voltages providing LV operation and ultra high current drive capability. High linearity and very high output impedance are achieved employing a novel resistor based current mirror avoiding conventional cascode structures to be used. The operation of the proposed COS has been verified through HSPICE simulations based on TSMC 0.18μm CMOS technology parameters. Under supply voltage of ±0.7V and bias current of 5μA, it can deliver output currents as high as 14mA with THD better than −53dB and extremely high output impedance of 320MΩ while consuming only 29μW. This makes the proposed COS to have ultra large current drive ratio (Ioutmax/Ibias or the ratio of peak output current to the bias current of output branch transistors) of 2800. By increasing supply voltage to ±0.9V, it can deliver extremely large output current of ±24mA corresponding to 3200 current drive ratio while consuming only 42.9μW and exhibiting high output impedance of 350MΩ. Interestingly, the proposed COS is the first yet reported one with such extremely high output current and a THD even less than −45dB. Such ultra high current drive capability, high linearity and high output impedance make the proposed COS an outstanding choice for LV, VLP and high drive current mode circuits. The superiority of the proposed COS gets more significance by showing in this work that conventional COS can deliver only ±3.29mA in equal condition. The proposed COS also exhibits high positive and negative power supply rejection ratio (PSRR+/PSRR−) of 125dB and 130dB, respectively. That makes it very suitable for LV, VLP mixed mode applications. The Monte Carlo simulation results are provided, which prove the outstanding robust performance of the proposed block versus process tolerances. Favorably the proposed COS resolves the major limitation of current output stages that so far has prevented designing high drive current mode circuits under low supply voltages. In brief, the deliberate combination of so many effective novel methods presents a wonderful phenomenal COS block to the world of science and engineering.

An Improved Full-Bridge Dual-Output DC–DC Converter Based on the Extended Complementary Pulsewidth Modulation Concept

This paper extends the original complementary pulsewidth modulation concept and proposes an improved dual-output dc-dc converter, in which one output branch gets the pulsewidths and is regulated by the duty cycle, while the other output branch gets the complementary pulsewidths and is regulated by the pulse-frequency modulation. The improved converter preserves all the advantages of its original version: both outputs can be fully regulated without additional switches, and all the primary-side switches can achieve the full-range zero-voltage switching. Besides, the improved converter overcomes the disadvantages of the original one: the resonant tank is moved to the primary side; the leakage and magnetizing inductances of the transformers are utilized as parts of the circuit parameters; the bulky output inductor and dissipative snubber are eliminated; both rectifiers can be clamped at the low output voltage; and they can work in the full-range zero-current switching. With these improvements, the cost and size of the proposed converter are significantly reduced, and the overall efficiency is increased. The derivation, operational principle, and circuit analysis of the proposed converter are presented in this paper, and they are verified by a prototype with 300-330 V input, and 24-V/10-A and 48-V/5-A outputs.

Particle-Image Velocimetry Study of a Pediatric Ventricular Assist Device

Particle-image velocimetry (PIV) was used to visualize the flow within an optically transparent pediatric ventricular assist device (PVAD) under development in our laboratory. The device studied is a diaphragm type pulsatile pump with an ejection volume of 30 ml per beating cycle intended for temporary cardiac assistance as a bridge to transplantation or recovery in children. Of particular interest was the identification of flow patterns, including regions of stagnation and/or strong turbulence that often promote thrombus formation and hemolysis, which can degrade the usefulness of such devices. For this purpose, phase-locked PIV measurements were performed in planes parallel to the diaphragm that drives the flow in the device. The test fluid was seeded with 10 microm polystyrene spheres, and the motion of these particles was used to determine the instantaneous flow velocity distribution in the illumination plane. These measurements revealed that flow velocities up to 1.0 m/s can occur within the PVAD. Phase-averaged velocity fields revealed the fixed vortices that drive the bulk flow within the device, though significant cycle-to-cycle variability was also quite apparent in the instantaneous velocity distributions, most notably during the filling phase. This cycle-to-cycle variability can generate strong turbulence that may contribute to greater hemolysis. Stagnation regions have also been observed between the input and output branches of the prototype, which can increase the likelihood of thrombus formation.

A Fully Regulated Dual-Output DC–DC Converter With Special-Connected Two Transformers (SCTTs) Cell and Complementary Pulsewidth Modulation–PFM (CPWM-PFM)

A dual-output dc-dc converter based on the complementary pulsewidth modulation is proposed to overcome the cross-regulation problem between the outputs. Using a special-connected two transformers cell, one operational period is divided into two complementary parts. One output branch gets the pulsewidth and is regulated by the duty cycle; the other output branch gets the complementary pulsewidth and is regulated by the PFM. Only one full bridge and several passive components are needed, but both the two outputs have the fully regulated abilities even in the no-load situation. Moreover, a full zero-voltage-switching (ZVS) range is achieved in all the switches without auxiliary circuits. Therefore, the proposed topology has compact structure, high switching frequency, high-power density, and high efficiency. The operation principle, ZVS conditions, and design considerations are presented in the paper. The analysis is verified by a 300 V input, and 24 V/10 A and 48 V/5 A outputs prototype.

Universal Current-Controlled Current-Mode Biquad Filter Employing MO-CCCCTAs and Grounded Capacitors

This paper presents a universal current-controlled current-mode biquad filter employing current controlled current conveyor trans-conductance amplifiers (CCCCTAs). The proposed filter employs only three MO- CCCCTAs and two grounded capacitors. The proposed filter can simultaneously realize low pass (LP), band pass (BP), high pass (HP), band reject (BR) and all pass (AP) responses in current form by choosing appropriate current output branches. In addition, the pole frequency and quality factor of the proposed filter circuit can be tuned independently and electronically over the wide range by adjusting the external bias currents. The circuit possesses low active and passive sensitivity performance. The validity of proposed filter is verified through PSPICE simulations.

Third Order Current Mode Universal Filter Using Only Op.amp. and OTAs

A novel current mode active-only universal filter using four dual current output Operational Transconductance Amplifiers (OTAs) and three Operational Amplifiers (OAs) is presented. The circuit can realize low pass and high pass filter characteristics by choosing the suitable current output branches. The filter performance factors natural frequency (ω0), bandwidth , quality factor Q and transconductance gain gm are electronically tunable. The proposed circuit has very low sensitivities with respect to circuit active elements. From sensitivity analysis, it has been clearly shown that the proposed circuit has very low sensitivities with respect to the circuit active elements. The gain roll-off of high pass and low pass configuration is 18 dB/oc- tave. The proposed circuit facilitates integrability, programmability and ease of implementation.

Efficient Multipath Diversity Receiver for STBC Block Transmission System

A space-time and multipath diversity combining algorithm is presented for STBC single carrier block transmission system with two transmit and one receive antennas. The initial solution is achieved by an STBC-based frequency domain equalizer, and the multipath components in the received signal are decoupled by this initial solution and channel state information. Finally, STBC combining is carried out on each decoupled multipath component separately, and then the single carrier output branches are combined further using the maximal ratio combining (MRC) algorithm.

Tunable Refractive Index Sensor with Ultracompact Structure Twisted by Poly(trimethylene terephthalate) Nanowires

We report a tunable refractive index sensor with ultracompact structure in a 2 x 2 poly(trimethylene terephthalate) (PTT) nanowire coupling splitter assembled by twisting two flexible PTT nanowires. The sensor consists of two input branches, a twisted coupling region, and two output branches. The changes of optical power caused due to variations in the surrounding medium around the twisted coupling region were measured in the output branches. The highest measured sensitivity of the sensor is 26.96 mW/RIU (refractive index unit) and the maximum detection limit on refractive index change is 1.85 x 10(-7). The average tunabilities observed are 1.2 mW per RIU per twisted turn and 1.8 mW per RIU per 5 degrees branching angle change.

Optical interconnections with photonic crystal self-collimation, directional emission and co-directional coupling mechanism

To combine the advantages of self-collimation, directional emission and co-directional coupling, a structure consisting of a self-collimation region, a coupler, a coupling section and two arbitrarily bent periodic dielectric waveguides is designed and analysed theoretically for optical interconnections. The light from the self-collimation region can be injected into the coupling section and transferred efficiently into the arbitrarily bent output branches if phase matching conditions are satisfied. By using the surface modification method, even when the Gaussian light source is placed far away from the self-collimation region, the desired directional emission effect can still be obtained. The performances of the proposed structure are evaluated by finite-difference time-domain simulations.

A New Low Crosstalk InP Digital Optical Switch Based on Carrier-Induced Effects for 1.55-$\mu$m Applications

This letter demonstrates an original carrier-induced effects InP digital optical switch (DOS) designed to achieve a low optical crosstalk for 1.55-mum wavelength applications. It is based on a widened multimode Y-junction combined with a sinusoidal shape waveguide to increase the optical contrast ratio between the two output branches. The entire InP-InGaAsP-InP DOS was designed using a semi-vectorial three-dimensional beam propagation method. The fabricated InP DOS with lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> = 1.3 mum heterostructure exhibits an optical crosstalk as low as -38.5 dB for a 33-mA switching current at 1.55-mum wavelength for a favourable polarized input light.

Power splitters with different output power levels based on directional coupling

The properties of a wideband photonic crystal power splitter with different output power levels based on directional coupling are investigated numerically with the finite-difference time-domain method. The effects of changing the coupling length and radius of the coupling rods between parallel waveguides on output transmissions are investigated. By further splitting power in each branch a power splitter with four output branches is proposed.

Indoor Characterisation using High-Resolution Signal Processing Based on Five-Port Techniques for Signal Input Multiple Output Systems

Problem statement: The development of wideband mobile communication systems requires a deep knowledge of the characteristics of the indoor mobile radio channel. The characterization of the indoor multi-path propagation structure is important in developing antifading techniques for high-speed digital radio access. The high-resolution of the estimation of the Time of Arrival (ToA) and the Direction of Arrival (DoA) of multi-path signals in wireless communication involves locating a source of Radio Frequency (RF) waves and then directing the beam of antenna in the estimated direction. The time dispersion is relatively small and the frequency dispersion is rather low compared to those expected in outdoor environments. Those characteristics require a high resolution system. This improved the performance of communication system. Approach: The DoA was estimated by measuring the phase difference of signals detected by an antenna array while the estimation of ToA was based on the phase difference measured over two successive frequencies. Low cost and high-resolution were obtained by using five-port receivers and the MUSIC algorithm. The simulation of five ports junction was developed using Advanced Design System (ADS). It was used to optimize the parameters of the structure and the antennas. Results: We obtained the adapted ring with the desired functions, splitting the received power equally over the output branches with a dephasing of 120°. The corresponding output signals appear with an amplitude variation depending on the dephasing between the RF and OL signals. Conclusion: Simulation results, performed around the 2.4 GHz frequency, showed an excellent estimation of the ToA and DoA with a high resolution and a reduced errors in both the time and the direction of multi-path signals.

Estimation of the information pathway in the neural network in the premotor center of Bombyx mori to generate the flip-flop activity and its validation by the simulation

Event Abstract Back to Event Estimation of the information pathway in the neural network in the premotor center of Bombyx mori to generate the flip-flop activity and its validation by the simulation Ikuko Nishikawa1*, Akira Takashima2, Shigehiro Namiki2, Tomoki Kazawa2, Stephan Shuichi Haupt2, Hidetoshi Ikeno3 and Ryohei Kanzaki2 1 Ritsumeikan University, Human and Computer Intelligence, Japan 2 The University of Tokyo, Japan 3 University of Hyogo, Japan The lateral accessory lobe (LAL) and the ventral protocerebrum (VPC) are known to form a premotor center of brain in insects. The present report focuses on the neural network of the LAL-VPC of Bombyx mori. The neuroethological experiments elucidate LAL-VPC generates a motor command of the pheromone oriented behavior, which is composed of a sequential activity of surge, zigzag-turn and loop [1,2]. The LAL-VPC region has been characterized by its temporal activity with alternating flip-flop patterns between both hemispheres, through the records from the descending neurons. Moreover, electrophysiological and immunohistochemical studies enable the physiological and morphological classification of LAL-VPC neurons, and thereby suggest possible anatomical connections among the neurons.The goal of this study is to estimate the functional connection strengths of the above anatomically found synaptic connections to elucidate the main information pathway for generating the flip-flop activity in LAL-VPC. The available data to challenge this problem is the stimulus-evoked activities of LAL-VPC neurons. Another key is the experimental finding that LAL-VPC consists of multiple neuropile regions [3], and each neuron possesses input branches from one or more regions and output branches to other regions. Based on these experimental findings, first, we define the following self-consistent formula to derive the connection strengths. That is, the activity of each neuropile region is given by the weighted summation of the outputs from the connecting neurons, and at the same time, the activity of each neuron is given by the weighted summation of the inputs from the connecting regions. Then, the formula is solved as an optimization problem, whose evaluation function is the reproducibility of the observed neuron activities, and the constraints are the observed anatomical connections. Finally, the connection strengths obtained as optimal solutions of the above static model are evaluated by a network simulation, in which each neuron has a spiking dynamics.A simulator of LAL-VPC network is described by Integrate-and-Fire model for each neuron and two-state kinetic model for each synapse. All of experimentally observed LAL-VPC neurons are connected by the strengths obtained by the above method. Most bilateral neurons are considered as inhibitory, and all local interneurons are set excitatory for the simplicity. Poisson noise is given to each neuron for the spontaneous activity, and the post inhibitory rebound firing is considered. The obtained connection is evaluated by how the temporal activity of each neuron reproduces the physiological data, especially the alternating flip-flop in both hemispheres.