Input End Research Articles

Model of Anti-Stokes Fluorescence Cooling in a Single-Mode Optical Fiber

We report a comprehensive model that quantifies analytically and numerically the heat that can be extracted by anti-Stokes fluorescence (ASF) from a fiber doped with a quasi-two-level laser ion. This model is used to investigate the effects on cooling of all relevant fiber and pump parameters, as well as amplified spontaneous emission. Simulations of a typical Yb-doped ZBLANP single-mode fiber show that for short enough fibers the heat extraction is relatively uniform along the fiber length. There is an optimum pump wavelength and power that maximizes the heat extracted per unit length. At this power, the coolest point is at the fiber input end. At higher powers, the coolest spot moves further down the fiber. The total heat extracted from a fiber, important for payload cooling, depends on the fiber absorptive loss, the pump wavelength, and the pump power. Simple expressions are derived to predict the optimum dopant concentration that maximizes heat extraction and the maximum tolerable absorptive fiber loss above which cooling is unobtainable. In a fiber with negligible residual absorption, the cooling efficiency is predicted to be 3.7%. In the modeled fiber, it is reduced to 1.7% in part by concentration quenching, but mainly due to the fiber absorptive loss (∼15 dB/km). Since the total extracted heat increases linearly with core radius and dopant concentration (up to a limit determined by concentration quenching), highly doped multimode fibers are strong candidates for payload cooling. This model can be straightforwardly expanded to design and optimize fiber lasers and amplifiers that utilize ASF for cooling.

Thermal oxidation-resistant GeO2 ATR hollow waveguide based on NiCr capillary tube and its thermal effects

Transmission characteristics of a metallic tube GeO2 ATR hollow waveguide degenerate due to metal thermal oxidation caused by transmission, coupling and misalignment losses. NiCr has intrinsic resistance to thermal oxidation and is often used in thermocouple heater. Thermogravimetric analysis shows that NiCr substrate tube material suffers no thermal oxidation with temperature up to 1100 °C. Thus, NiCr capillary tube is investigated for construction of a thermal oxidation-resistant GeO2 ATR hollow fiber. A NiCr capillary tube GeO2 ATR hollow fiber was fabricated based on liquid phase deposition. The fiber sample has a transmission attenuation of 0.25 dB/m when transmitting a 6-W CO2 laser. Sample temperature distributions that originated from transmission loss and coupling loss are theoretically simulated and practically measured. Results confirm that the simulation can properly tell the influence of laser power losses on the fiber temperature and is further used to predict the maximum input power of the ATR fibers. To illustrate the thermal oxidation resistance of NiCr ATR hollow fiber, NiCr-based and stainless steel (SUS)-based ATR hollow fibers are directly irradiated by 6 W CO2 laser. The SUS fiber input end became darkened. No obvious changes happened on NiCr fiber. Output beam profile and divergence angle are also taken to support the analysis. The NiCr capillary tube GeO2 ATR hollow fiber is a good candidate for construction of durable GeO2 ATR hollow fiber in high power applications.

Dominance of backward stimulated Raman scattering in gas-filled hollow-core photonic crystal fibers

Backward stimulated Raman scattering in gases provides a promising route to compression and amplification of a Stokes seed-pulse by counter-propagating against a pump-pulse, as has been already demonstrated in various platforms, mainly in free-space. However, the dynamics governing this process when seeded by noise has not yet been investigated in a fully controllable collinear environment. Here we report the first unambiguous observation of efficient noise-seeded backward stimulated Raman scattering in a hydrogen-filled hollow-core photonic crystal fiber. At high gas pressures, when the backward Raman gain is comparable with, but lower than, the forward gain, we report quantum conversion efficiencies exceeding 40% to the backward Stokes at 683 nm from a narrowband 532-nm-pump. The efficiency increases to 65% when the backward process is seeded by a small amount of back-reflected forward-generated Stokes light. At high pump powers the backward Stokes signal, emitted in a clean fundamental mode and spectrally pure, is unexpectedly always stronger than its forward-propagating counterpart. We attribute this striking observation to the unique temporal dynamics of the interacting fields, which cause the Raman coherence (which takes the form of a moving fine-period Bragg grating) to grow in strength towards the input end of the fiber. A good understanding of this process, together with the rapid development of novel anti-resonant-guiding hollow-core fibers, may lead to improved designs of efficient gas-based Raman lasers and amplifiers operating at wavelengths from the ultraviolet to the mid-infrared.

Analyzing characteristics of spiral vector beams generated by mixing of orthogonal LP11 modes in a few-mode optical fiber.

We have demonstrated a method for the generation of spiral vector beams using a few-mode optical fiber. The beams are generated due to the combination of orthogonal linearly polarized modes with a tilted polarization vector in the few-mode optical fiber. The excitation of these modes is controlled by the incident state of polarization and coupling conditions at the input end of the fiber. The beams with clockwise and counterclockwise nature of spiral polarization are generated, and switching between them is demonstrated. The obtained results emphasize the strong dependency of polarization of generated spiral vector beams and other orthogonal linearly polarized modes on the input state of polarization. The simulated results of mode mixing are verified experimentally with good agreement.

Mode Couplers and Converters Based on Dual-Core Hollow-Core Photonic Bandgap Fiber

We propose mode couplers and converters based on dual-core hollow-core photonic bandgap fiber (HC-PBGF) structures, which might be potential solutions for integrated all-fiber multiplexers or demultiplexers of a mode-division multiplexed (MDM) transmission system using HC-PBGFs. Coupling properties of ${\text{LP}}_{01}$ and ${\text{LP}}_{11}$ mode in the mode coupler are investigated and applied to mode separators and polarization separators. Mode transition from ${\text{LP}}_{01}$ to ${\text{LP}}_{11}$ and ${\text{LP}}_{21}$ mode are demonstrated in the mode converter whose smaller core is expected as input end and matched with single-mode fiber. The coupling between fundamental mode and high-order modes is accomplished through the resonant effect, which is fulfilled by modifying the structure parameter of the smaller core. Such mode converters based on dual-core HC-PBGF could be a promising substitute for the free-space coupling device, which is costly and not suitable for integration design in MDM systems and other hollow-core fiber experiments and applications.

FRS-DAB Converter for Elimination of Circulation Power Flow at Input and Output Ends

Dual active bridge (DAB) converter is the most suitable converter to transfer high power with bidirectional power flow capability and isolation. However, it has the drawbacks of circulation power flow (CPF) and limited range of zero voltage switching (ZVS). To overcome these drawbacks, several modulation strategies have been proposed; however, the CPF can be eliminated either at input or output voltage ends. In order to eliminate the CPF at both input and output sides, a novel front and rear end switch DAB (FRS-DAB) bidirectional dc–dc converter has been proposed in this paper. It has the advantages of lower current stress, extension of ZVS range, higher power transfer capacity, and improved efficiency compared to the conventional DAB converter. The paper presents the detailed operating modes and analysis of power flow control for the proposed FRS-DAB converter. The operation and analytical results of the proposed converter have been verified through the experimental results using an FPGA Spartan 3AN processor.

Cladding waveguide splitters fabricated by femtosecond laser inscription in Ti:Sapphire crystal

Highly-compact devices capable of beam splitting are intriguing for a broad range of photonic applications. In this work, we report on the fabrication of optical waveguide splitters with rectangular cladding geometry in a Ti:Sapphire crystal by femtosecond laser inscription. Y-splitters are fabricated with 30 μm × 15 μm and 50 μm × 25 μm input ends, corresponding to two 15 μm × 15 μm and 25 μm × 25 μm output ends, respectively. The full branching angle θ between the two output arms are changing from 0.5° to 2°. The performances of the splitters are characterized at 632.8 nm and 1064 nm, showing very good properties including symmetrical output ends, single-mode guidance, equalized splitting ratios, all-angle-polarization light transmission and intact luminescence features in the waveguide cores. The realization of these waveguide splitters with good performances demonstrates the potential of such promising devices in complex monolithic photonic circuits and active optical devices such as miniature tunable lasers.

Shupe effect of fiber sensing coils in multidimensional thermal field

Optical fibers have a wide range of applications and constitute the core of fiber-optic gyroscope which is revolutionizing the ancient inertial rotation detection. However, fiber coils in these instruments are susceptible to surrounding physical quantities, which can seriously deteriorate their accuracy. And the thermally induced parasitic effect is one of the most critical factors leading to the bias drift. This drift error is due to the nonreciprocity phase shift in the counter-propagating optical loops when a thermal gradient passes through the fiber coil as described by Shupe. The quadrupole winding patterns along with other coiling schemes have been proposed to reduce the Shupe effect by maintaining fiber parts at equal distances from the coil center beside each other. Many researchers have investigated the thermal effect on this drift on the assumption that the temperature transient propagates only radially along the fiber coil, while little attention has been paid to the case of the multidimensional thermal field. This can hardly satisfy completeness of the theory, and be applied to certain complicated working conditions. In this paper, we develop theoretical models that describe drift signals caused by radially, axially and circumferentially transmitted thermal effects on the quadrupole winding fiber coil. The obtained findings indicate that the bias error excited by the thermal flow in radial and axial directions is proportional to the weighted sum of the difference in temperature changing rate between outer and inner sides of the fiber ring. And the share of the sum linearly grows when approaching to the top surface near the input and output end (I/O end) of the fiber. Thus, it is suggested that it should be avoided to place heat sources in the neighboring area. For the circumferentially distributed temperature field, the drift depends on the symmetry of the thermal gradients on both sides of the centerline connecting the fiber midpoint and the I/O end. This circumferential thermal effect can be dominant, since it tends to cover a larger spatial scale than its counterparts in radial and axial directions. And besides making a good symmetrical design of the temperature distribution with respect to the centerline, it can be suppressed by arranging the nonuniformity of the thermal field in the opposite direction of the fiber coil to the I/O end, which is also beneficial to reducing its sensitivity to the angular change. Our results can help better understand the mechanisms for the thermal error formation and guide us in optimizing and facilitating the thermo-structure design of both fiber gyroscopes and navigation systems.

Modeling and Analysis of a Novel Decoupled Vibration-Assisted Swing Cutting System for Micro/Nano-Machining Surface

The flexure-based motion platform with high-positioning precision and fast response is really attractive for the realization of micro/nano-machining surface. However, coupling motion effect existed in most positioning systems, which will induce the asymmetry and incline deformation and lead to a poor processing quality. To alleviate this problem, we proposed a decoupled vibration-assisted swing cutting (VASC) system driven by two piezoelectric actuators in this paper. A double symmetric L-shaped parallel flexure hinge with decoupled actuation and decoupled output motion has been designed in this system. In order to analyze the effect of the parameter variation to the system, the kinematics, statics, and dynamics properties of the VASC system were modeled by the geometrical method, matrix-based compliance modeling, and Lagrangian principle, respectively. Meanwhile, we have validated the effect of the parameter variation for angle-position trajectory, output stiffness, and natural frequencies by simulation analysis. In addition, the decoupled performance could be determined by finite-element analysis. In the view of the decoupling property, the result shows that the motion stroke of the input end can reach up to $15.67~\mu \text{m}$ , and the coupling ration has effectively decreased to 1.27%. Both analysis and experiment have verified the decoupled properties of VASC that have proved the effectiveness of the present VASC system for micro/nano-machining surface.

CoMET: Composite-Input Magnetoelectric- Based Logic Technology

This paper proposes composite-input magnetoelectric-based logic technology (CoMET), a fast and energy-efficient spintronics device for logic applications. An input voltage is applied to a ferroelectric (FE) material, in contact with a composite structure—a ferromagnet (FM) with in-plane magnetic anisotropy placed on top of an intragate FM interconnect with perpendicular magnetic anisotropy (PMA). Through the magnetoelectric (ME) effect, the input voltage nucleates a domain wall (DW) at the input end of the PMA-FM interconnect. An applied current then rapidly propagates the DW toward the output FE structure, where the inverse-ME effect generates an output voltage. This voltage is propagated to the input of the next CoMET device using a novel circuit structure that enables efficient device cascading. The material parameters for CoMET are optimized by systematically exploring the impact of parameter choices on device performance. Simulations on a 7-nm CoMET device show fast, low-energy operation, with a delay/energy of 99 ps/68 aJ for INV and 135 ps/85 aJ for MAJ3.

Analysis Method of Compound ADC Modeling

A new type of ADC with a precision of 10-bit and a sampling rate of 250M is implemented by modeling. The new composite ADC proposed in this paper achieves high power consumption and reduced area with high accuracy and medium speed by combining the advantages and disadvantages of pipeline ADC and SAR ADC. In this paper, the system modeling and simulation verification are carried out for the new composite structure ADC. In the premise of considering many non-ideal factors, the input end access 36.6MHz input signal, sampling clock frequency using 250MHz, the system can achieve SNR = 58.5dB, SFDR = 68.8dB, ENOB = 9.3 and other design indicators. The design of this system model provides the direction for the determination of important module design parameters in the actual circuit-level design system. At the same time, it provides the basis for analyzing the influence of various non-ideal factors on static and dynamic characteristics and the ADC energy in ADC system design.

Application value of Braun anastomosis in pancreaticoduodenectomy

Objective To investigate the application value of Braun anastomosis in pancreatico-duodenectomy. Methods The retrospective cohort study was conducted. The clinicopathological data of 389 patients who underwent pancreaticoduodenectomy in the Fudan University Shanghai Cancer Center from March 2012 to July 2014 were collected. Of 389 patients, 235 receiving Braun anastomosis and 154 receiving non-Braun anastomosis were respectively allocated into Braun anastomosis group and non-Braun anastomosis group. All the patients underwent pancreaticoduodenectomy with digestive tract reconstruction using Child method. Patients in the Braun anastomosis group received 5-10 cm Braun anastomosis between input and output end of jejunum, and patients in the non-Braun anastomosis group didn′t receive jejunum-jejunum Braun anastomosis after gastrojejunostomy. Observation indicators included: (1) intraoperative situations; (2) postoperative recovery; (3) follow-up. Patients were followed up using outpatient examination and telephone interview up to May 2015. Follow-up included monthly routine blood retest, hepatorenal function retest and urine and stool routine retest, and enhanced CT scan in the epigastric region for every three months to detect recovery of digestive tract function. Measurement data with normal distribution were represented as ±s. Comparison between groups was analyzed using t test, and count data were analyzed using chi-square test. Results (1) Intraoperative situations: 389 patients underwent successful pancreaticoduodenectomy. Standard pancreaticoduodenectomy and pyloric-preserving pancreaticoduodenectomy were respectively applied to 205 and 30 patients in the Braun anastomosis group and 137 and 17 patients in the non-Braun anastomosis group, with no statistically significant difference (χ2=0.259, P>0.05). Anastomosis and reconstruction of pancreatic stump: anastomosis of main pancreatic duct and jejunal mucosa, embedded anastomosis of papillary main pancreatic duct and pancreas-stomach anastomosis were detected in 138, 89, 8 patients in the Braun anastomosis group and 85, 60, 9 patients in the non-Braun anastomosis group, respectively, with no statistically significant difference (χ2=1.535, P>0.05). Total operation time, pancreas-jejunum anastomosis time and volume of intraoperative blood loss were (398.9±61.9)minutes, (20.6±3.5)minutes, (401±59)mL in the Braun anastomosis group and (401.3±59.2)minutes, (20.7±2.1)minutes, (407±159)mL in the non-Braun anastomosis group, respectively, with no statistically significant difference (t=-0.380, -0.562, -0.319, P>0.05). (2) Postoperative recovery: time to initial anal exsufflation, time for fluid diet intake and time of drainage tube removal were (103±28)hours, (77±25)hours, (12±5)days in the Braun anastomosis group and (102±31)hours, (79±30)hours, (13±6)days in the non-Braun anastomosis group, respectively, with no statistically significant difference (t=0.330, -0.712, -1.783, P>0.05). Delayed gastric emptying, gastrointestinal hemorrhage, obstruction of afferent loop and pancreatic fistula were detected in 25, 3, 0, 30 patients in the Braun anastomosis group and 27, 4, 2, 23 patients in the non-Braun anastomosis group, respectively, with no statistically significant difference (χ2=3.818, 0.918, 3.068, 0.695, P>0.05). Seventeen patients were combined with delayed gastric emptying and pancreatic fistula, including 8 in the Braun anastomosis group and 9 in the non-Braun anastomosis group, with no statistically significant difference between the 2 groups (χ2=1.363, P>0.05). Patients with postoperative complications were improved by symptomatic and supporting treatment. Duration of hospital stay and treatment expenses were (14±7)days, (73 205±4 538)yuan in the Braun anastomosis group and (22±11)days, (83 219±5 738)yuan in the non-Braun anastomosis group, with statistically significant differences between the 2 groups (t=-8.767, -19.139, P<0.05). (3) Follow-up: 389 patients were followed up for 6 months, without death. Six and 9 patients in the Braun anastomosis group and non-Braun anastomosis group had regurgitation cholangitis. There was no readmission due to gastrointestinal hemorrhage and digestive tract obstruction, and no signs of hyperglycaemia and intractable diarrhea occurred. Conclusion Braun anastomosis can reduce duration of postoperative hospital stay and treatment expenses. Key words: Pancreaticoduodenectomy; Braun anastomosis; Delayed gastric emptying; Pancreatic fistula

Analytical and experimental study of an ultrasonic horn with a bend angle

An ultrasonic horn is a key component in power ultrasonic longitudinal vibration systems, and the most common horns are designed to allow vibration to travel along a single straight axis. However, change of the propagation direction is required in such applications as ultrasonic cleaning of the inner surface of a bent pipe, ultrasonic-assisted turning for a deep concave workpiece, and ultrasonic bone cutting devices. To address this requirement, this work proposes an angled horn comprising two uniform rods of finite length, which can be excited to resonate in longitudinal mode to change the propagation direction of a longitudinal vibration. Experimental comparison of the working frequencies of the designed and fabricated angled horns validated the effectiveness of the proposed design method. Experimental tests also showed that longitudinal vibration excited by a transducer along the axial direction was successfully transferred from the input end to the output end via the angled horn. Furthermore, the linear vibration characteristics of nine prototype vibration systems (composed of one transducer and nine angled horns) were obtained by measuring the vibration amplitudes induced by various excited voltages applied to the transducer.

A novel hybrid actuation mechanism based XY nanopositioning stage with totally decoupled kinematics

Abstract This paper reports the design, analysis and testing of a parallel two degree-of-freedom piezo-actuated compliant stage for XY nanopositioning by introducing an innovative hybrid actuation mechanism. It mainly features the combination of two Scott–Russell and a half-bridge mechanisms for double-stage displacement amplification as well as moving direction modulation. By adopting the leaf-type double parallelogram (LTDP) structures at both input and output ends of the hybrid mechanism, the lateral stiffness and dynamic characteristics are significantly improved while the parasitic motions are greatly eliminated. The XY nanopositioning stage is constructed with two orthogonally configured hybrid mechanisms along with the LTDP mechanisms for totally decoupled kinematics at both input and output ends. An analytical model was established to describe the complete elastic deformation behavior of the stage, with further verification through the finite element simulation. Finally, experiments were implemented to comprehensively evaluate both the static and dynamic performances of the proposed stage. Closed-loop control of the piezoelectric actuators (PEA) by integrating strain gauges was also conducted to effectively eliminate the nonlinear hysteresis of the stage.

Investigation on photonic crystal based all‐optical clocked D‐flip flop

In this study, the authors propose a photonic crystal-based clocked D-flip flop using multi-mode interference (MMI). A central MMI waveguide is created for the interference of the input light and ports are placed at both input and output ends of it. The proposed structure is resulted with a contrast ratio (CR) of 9.63 and 5.84 dB at the outputs Q and QQ with a response time or delay of less than 0.29 ps. Furthermore, the input and output waveguides are extended with sharp and smooth bend waveguides, respectively, in order to increase the delay of the structure as the delayed output is one of the main objectives of D-flip flop. The modified D-flip flop structure is operated with a delay of more than twofold of the basic structure by maintaining nearly the same CR at the output. The compactness and the fair simulation results of the proposed structure show that it is quite suitable to be a part of photonic integrated circuit.

Low-loss and low-crosstalk multi-channel mode (de)multiplexer with ultrathin silicon waveguides.

A multi-channel mode (de)multiplexer based on the supermode evolution in cascaded dual-core adiabatic tapers is designed and realized with ultrathin (∼50 nm) silicon-on-insulator nanowire waveguides. This dual-core adiabatic taper is designed optimally, so that all the supermodes are confined in the wide core at the input end and the highest-order supermode is localized in the narrow core at the output end. In this way, the highest-order supermode is dropped as the fundamental mode at the cross port. As an example, a (de)multiplexer with three mode channels is designed and fabricated. From the measured spectral responses, the fabricated device has a crosstalk lower than -20 dB and an excess loss less than 0.2dB in a bandwidth of ∼65 nm.

Speech Emotion Classification Analysis using Short-term Features

Speech is an auditory signal produced from the human speech production system used to express ourselves. In this era, speech signals are also used in biometric identification technologies and interacting with machines, so that it can give different response. Emotion recognition is not a new topic and researches and applications exist using different methods to extract specific features from the speech signals. This paper presents a classification analysis of emotional human speech only with short term processing features of the speech signals using artificial neural network based approach. Speech rate, pitch and energy are the most basic features of speech signal but they still have significant differences between emotions such as angry and sad. The most common way to analyze the speech emotion is to extract important features which are related to different emotion states from the voice signal. In the speech pre-processing phase, the samples of four basic types of emotional speeches sad, angry, happy, and neutral are used. Then feed those extracted short term features into the input end of the classifier and obtained different emotions at the output end. 23 short term audio signal features of 40 samples of two frames are selected and extracted from the speech signals to analyze the human emotions. These derived data along with their related emotion target matrix are fed to test and design the classifier using artificial neural network pattern recognition algorithm. The confusion matrix is generated to analyze the performance results. The overall correctly classified results for two times trained network is 73.8 %, while increasing the training times to ten, 95 % of the emotions are correctly classified. The accuracy of the neural network system is improved by multiple times of training. The overall system provides a reliable performance and correctly classifies more than 85 % for the new non-trained dataset.

Formation of long nanosecond rectangular pulses in the active RF pulse compression system with a compact resonant cavity

This work presents the results of the study of an active microwave pulse compression system capable of forming the rectangular pulses with duration ∼10-100 ns, while its dimensions are several times smaller than the radiated wave train. Such compression system is based on the compact planar-voluminal resonant cavity constructed in the shape of a meander from waveguide sections and H-plane tees. The resonant cavity sections are parallel and are in the same plane with tees. The energy input element is located in the input end of the first section. The output device designed as an H-plane tee interference switch is connected to the output end of the last section. Each end of remaining sections is connected through a straight arm to an H-tee with a short-circuited quarter-wave second straight arm. The side arm of each tee is connected with the side arm of the tee in the next section, thus coupling the sections. The short-circuited arm provides the “open” mode and transmission of the wave from tee to tee. We determined the expressions for wave amplitudes in the components of the meander resonant cavity made of three sections and analyzed the expressions as the functions of the parameters determining the oscillation range and energy distribution in the resonant cavity. Experiments demonstrated that under certain conditions the compressors with such resonant cavity could generate nearly rectangular pulses with duration equal to the time of wave two-way traveling along the resonant cavity, and with the power compatible with that of the wave in the resonant cavity, and the length of the radiated wave train several-fold exceeding the size of the compressor. At pulse duration equal to 25 ns, the gain coefficient was 13 dB and pulse power was 40 MW. The work demonstrates the possibility to change the geometry of the resonant cavity by rearranging its components without changing the output pulse parameters.

Using the locus-of-slack logic to determine whether inhibition of return in a cue-target paradigm is delaying early or late stages of processing.

Inhibition of return (IOR) is a phenomenon characterized by slower responses to targets at cued locations relative to those at uncued locations. Based on the results of previous research, it has been suggested that IOR affects a process at the input end of the processing continuum when it is generated while the reflexive oculomotor system is suppressed (cf. Satel, Hilchey, Wang, Story, & Klein, 2013). To test this theory, we employed a modified psychological refractory period paradigm designed to elicit input IOR with visual stimuli, allowing us to use the locus-of-slack logic to determine whether an early or late stage of processing was inhibited by IOR. On each trial a visual cue was presented, followed by an auditory target (T1) and visual target (T2) separated by a target-target onset asynchrony (TTOA) of varying lengths (200 ms, 400 ms, or 800 ms). Participants (31 young adults) were instructed to ignore the cue and respond to the targets as quickly and accurately as possible. Eye tracking was used to ensure that participants actively suppressed eye movements during trials. As predicted, the inhibitory effect of the cue was observed at the longest TTOA but not when TTOAs were short, supporting our hypothesis that, when generated while the reflexive oculomotor system is suppressed, IOR affects processing before response selection. (PsycINFO Database Record

Multiphase Oscillator Using Traveling Pulses Developed in a System of Transmission Lines with Regularly Spaced Resonant-tunneling Diodes

A scheme is proposed for generating multiphase oscillatory signals in millimeter-wave frequencies based on the dynamics of a traveling pulse developed in a closed transmission line periodically loaded with resonant-tunneling diodes (RTDs) that is coupled with several straight RTD lines. When supplied with an appropriate voltage at the end of an RTD line, a pulse edge is shown to exhibit a spatially extended limit-cycle oscillation on the line. We consider the case where several RTD lines are connected halfway to a closed one at even intervals. In this case, the oscillatory edge developed in each straight RTD line is mutually synchronized such that a pulse-shaped rotary traveling wave develops on the closed RTD line. The oscillating edge on each straight line is also synchronized with the traveling pulse on the closed line, such that the leading edge of the traveling pulse on the closed line and the forward edge on the straight line pass the cross point simultaneously. As a result, when N L straight lines are connected to the closed line, the phase difference between two adjacent oscillatory edges becomes 2π/N L . On the other hand, the trailing edge of the traveling pulse at the cross point breaks the voltage wave on the straight line into two pieces, one of which travels forward to form a solitary wave and the other of which travels backward to reach the input end, where it is reflected and starts to travel forward and this forward moving edge is supposed to be synchronized with the leading edge of the traveling pulse. It means that a back-and-forth edge and a forward-moving solitary wave develop periodically on each straight line. Because the time required for the traveling pulse to go around the closed line must be coincident with the period of the edge oscillation on each straight line, a unique traveling pulse cannot synchronize with each oscillating edge when the cell size of the closed line becomes large, resulting in the development of multiple traveling pulses on the closed line. In this paper, the design criteria are discussed concerning the connecting point between the straight and closed lines, the number of straight lines, and the size of the closed line. In addition, we describe several measurement results that validate the essential properties of the traveling pulse and then show several results of full-wave analysis of a monolithically integrated RTD line.