TRULY BALANCED PULSE GENERATOR USING MICROWAVE TRANSISTOR AND SRD

A novel efficient circuit for Ultra-WideBand(UWB) balanced sub-nanosecond monocycle pulse generation is presented.The pulse generator employs wideband bipolar transistor,step recovery diodes,Schottky diodes,and simple charging and discharging circuitry.Simple transient analysis and design of the circuit are presented along with their operating principle.The pulse generator produces truly balanced monocycle pulse with 500 ps pulse-width and 800 mV peak voltage.The generated monocycle pulse also has very symmetrical positive and negative portions and low ringing level.The presented pulse generator can be used as both a transmitter feeding UWB balanced antennas without broadband baluns and a balanced switching pulse generator that used in UWB receiver.

Clinical outcomes of sacral neuromodulation in non-neurogenic,non-obstructive dysuria:A 5-year retrospective,multicentre study in China

BACKGROUND Management of non-neurogenic,non-obstructive dysuria represents one of the most challenging dilemmas in urological practice.The main clinical symptom is the increase in residual urine.Voiding dysfunction is the main cause of dysuria or urinary retention,mainly due to the decrease in bladder contraction(the decrease in contraction amplitude or duration)or the increase in outflow tract resistance.Sacral neuromodulation(SNM)has been used for>10 years to treat many kinds of lower urinary tract dysfunction.It has become increasingly popular in China in recent years.Consequently,studies focusing on nonneurogenic,non-obstructive dysuria patients treated by SNM are highly desirable.AIM To assess the outcome of two-stage SNM in non-neurogenic,non-obstructive dysuria.METHODS Clinical data of 54 patients(26 men,28 women)with non-neurogenic,nonobstructive dysuria treated by SNM from January 2012 to December 2016 in ten medical centers in China were retrospectively analyzed.All patients received two or more conservative treatments.The voiding diary,urgency score,and quality of life score before operation,after implantation of tined lead in stage I(test period),and during short-term follow-up(latest follow-up)after implantation of the implanted pulse generator in stage II were compared to observe symptom improvements.RESULTS Among the 54 study patients,eight refused to implant an implanted pulse generator because of the unsatisfactory effect,and 46 chose to embed the implanted pulse generator at the end of stage I.The conversion rate of stage I to stage II was 85.2%.The average follow-up time was 18.6 mo.There were significant differences between baseline(before stage I)and the test period(after stage I)in residual urine,voiding frequency,average voiding amount,maximum voiding amount,nocturia,urgency score,and quality of life score.The residual urine and urgency score between the test period and the latest follow-up time(after stage II)were also significantly different.No significant differences were observed for other parameters.No wound infection,electrode breakage,or other irreversible adverse events occurred.CONCLUSION SNM is effective for patients with non-neurogenic,non-obstructive dysuria showing a poor response to traditional treatment.The duration of continuous stimulation may be positively correlated with the improvement of residual urine.

Modeling and Simulation of a Gas-Liquid Coupling Excitation-Induced Cavitation Bubble

A gas-liquid coupling excitation mode is proposed and the gas-liquid excitation experimental system is developed. Air from pulse generator is mixed with liquid,through which the generated cavitation bubbles can strip contaminants adhered to the pipe inner wall rapidly. The kinematics equation of the bubble inside the hydraulic oil is established and the numerical simulations are carried out. The influential factors such as gas pressure, excitation frequency,initial bubble radius and fluid viscosity are analyzed.The results show that the cavitation will evolve from steady state to transient state with the increasing gas pressure and initial bubble radius. The pulse generator frequency has a slightly effect on the growth of the bubble radius,and the breakup time of the bubble is shortened with the rising frequency. Similarly, the increasing viscosity of liquid has minimal impact on cavitation effect,which can weaken the growth and the collapse of the bubble. Moreover,the temperature inside the cavitation bubble is investigated,indicating that the instantaneous temperature inside the bubble increases with the rising gas pressure. Once the gas pressure is raised to a certain value greater than the fluid static pressure, the instantaneous temperature inside the bubble will rise sharply. So, it can be concluded that the gas-liquid coupling excitation-induced cavitation process is controllable, and some theoretical basis of the new excitation mode is presented,which is expected to be applied in the online cleaning of the complex hydraulic system.

Pulse Generation and Compression Techniques for Microwave Electronics and Ultrafast Systems

Ultrabroadband systems and ultrafast electronics require the generation,transmission,and processing of high-quality ultrashort pulses rang-ing from nanoseconds(ns)to picoseconds(ps),which include well-established and emerging applications of time-domain reflectometry,arbitrary wave-form generation,sampling oscilloscopes,frequency synthesis,through-wall radar imaging,indoor communication,radar surveillance,and medical radar detection.Impulse radar advancements in industrial,scientific,and medical(ISM)domains are,for example,driven by ns-scale-defined ultrawideband(UWB)technologies.Nevertheless,the generation of ultrashort ps-scale pulses is highly desired to achieve unprecedented performances in all these ap-plications and future systems.However,due to the variety and applicability of different pulse generation and compression techniques,the selection of optimum or appropriate pulse generators and compressors is difficult for practitioners and users.To this end,this article aims to provide a comprehen-sive overview of ultrashort ns and ps pulse generation and compression techniques.The proposed and developed pulse generators available in the litera-ture and on the market,which are characterized by their corresponding pros and cons,are also explored.The theoretical analysis of pulse generation us-ing a nonlinear transmission line(NLTL)presented in the literature is briefly explained as well.Additionally,a holistic overview of these pulse genera-tors from the perspective of applications is given to describe their utilization in practical systems.All of these techniques are well summarized and com-pared in terms of fundamental pulse parameters,and research gaps in specified areas are highlighted.A thorough discussion of previous research work on various topologies and techniques is presented,and potential future directions for technical advancement are examined.

Model and Simulation of a New Ultra-Narrow Trigger Frequency Alterable Pulse Generator

Two new kinds of ultra-narrow trigger frequency alterable picosecond pulse generator are presented.One can produce positive pulses and the other can produce negative pulses.The two pulse generators are subdivided into three parts:signal driving circuit,differentiator network and pulse shaping circuit.The pulse shaping circuit is made of step recovery diode(SRD) and short-circuit microstrip line.A positive pulse with width of 54 ps(50%-50%),rising time of 30 ps(10%-90%) and falling time of 32 ps(90%-10%),and a negative pulse with width of 54 ps(50%-50%),rising time of 30 ps(90%-10%) and falling time of 30 ps(10%-90%) are achieved in simulation.All of the components are ready-made and inexpensive.They can be applied in ultra-wideband(UWB) communication system,such as transmitters and receivers.