A Time-Domain z−1 Circuit with Digital Calibration

This paper presents a novel circuit of a z−1 operation which is suitable, as a basic building block, for time-domain topologies and signal processing. The proposed circuit employs a time register circuit which is based on the capacitor discharging method. The large variation of the capacitor discharging slope over technology process and chip temperature variations which affect the z−1 accuracy is improved using a novel digital calibration loop. The circuit is designed using a 28 nm Samsung FD-SOI process under 1 V supply voltage with 5 MHz sampling frequency. Simulation results validate the theoretical analysis presenting a variation of capacitor voltage discharging slope less than 5% over worst-case process corners for temperature between 0 °C and 100 °C while consuming only 30 μA. Also, the worst-case accuracy of z−1 operation is better than 33 ps for input pulse widths between 5 ns and 45 ns presenting huge improvement compared with the uncalibrated operator.

Time-Domain Pulse Waveform Correction for Pulsed Electric Field Measurement in Microwave Cable with Frequency-Dependent Loss

This paper presents a method that corrects pulse waveforms distorted by the frequency-dependent loss of microwave cables in measuring pulsed electric fields (PEFs). Because the distortion resulting from the microwave cable disrupts accurate PEF measurements, the distorted pulse should be corrected for precise PEF effect testing. The proposed correction method is achieved by a transfer function that is determined by ABCD parameters calculated from the scattering parameters of the cable. A 10-m microwave cable is tested to validate the proposed method, where the input pulse is a 2-ns sine pulse of a single cycle. Here, the output pulse, scattering parameters, and cable resistance are measured. These measurement results are used to represent the transfer function in MATLAB for the proposed correction method. The test results show that the corrected pulse obtained from the transfer function has an error of 4.5% in the peak-to-peak voltage and an error of 0.8% in the bipolar pulse width compared to the reference input pulse. The errors of PEF measurement decrease dramatically by using the proposed correction method. Moreover, the correction method is validated for various pulse durations, pulse shapes, and cable types.

Power Bus Management Techniques for Space Missions in Low Earth Orbit

In space vehicles, the typical configurations for the Solar Array Power Regulators in charge of managing power transfer from the solar array to the power bus are quite different from the corresponding devices in use for terrestrial applications. A thorough analysis is reported for the most popular approaches, namely Sequential Switching Shunt Regulation and parallel-input Pulse Width Modulated converters with Maximum Power Point Tracking. Their performance is compared with reference to a typical mission in low Earth orbit, highlighting the respective strengths and weaknesses. A novel solar array managing technique, the Sequential Maximum Power Tracking, is also introduced in the trade-off and was demonstrated able to boost energy harvesting, especially in the presence of mismatching in the solar array. It also can achieve top levels of reliability using a rather simple control hardware. Its operation was verified both by a Matlab–Simulink model and by an experimental breadboard.

Design of Broadband Flat Optical Frequency Comb Based on Cascaded Sign-Alternated Dispersion Tellurite Microstructure Fiber

We designed a tellurite microstructure fiber (TMF) and proposed a broadband optical frequency comb generation scheme that was based on electro-optical modulation and cascaded sign-alternated dispersion TMF (CSAD-TMF). In addition, the influence of different nonlinear effects, the ultrashort pulse evolution in the CSAD-TMF with the anomalous dispersion (AD) zones and the normal dispersion (ND) zones were analyzed based on the generalized nonlinear Schrodinger equations (GNLSE) modelling. According to the simulations, when the input seed comb had a repetition rate of 20 GHz and had an input pulse peak power of 30 W, the generation scheme could generate optical frequency combs with a 6 dB spectral bandwidth spanning over 170 nm centered at 1550 nm. Furthermore, the generated combs showed good coherence in performance over the whole 6 dB spectral bandwidth. The highly coherent optical frequency combs can be used as high-repetition-rate, multi-wavelength light sources for various integrated microwave photonics and ultrafast optical signal processing applications.

Microwave cyclotron protective devices for radar receivers

Brief overview of the latest developments of microwave cyclotron protective devices, their functioning and parameters is given. It is noted that these devices have a number of important advantages over other types of protective devices: they are autonomous, provide no peak of microwave power leaking to the output, frequency filtering and low noise figure (0.7-1.2 dB). The upper limit of the linearity of cyclotron protective devices in the signal transmission mode when the transmission coefficient is compressed by 1 dB is ~ 1 mW. The devices can operate with an input pulse power of up to 10 kW or more, while the attenuation of the input power in the protection mode is more than 60-80 dB. The recovery time of parameters after the end of a powerful input pulse is 10-20 ns. For devices of the 3-cm wavelength range, experimental data are given on the recovery time, the upper limit of linearity, attenuation of the input power in the protection mode, and filtration characteristics.

Electrical Stress on the Medium Voltage Medium Frequency Transformer

This paper proposes an equivalent circuit model to obtain the transient electrical stress quantitatively in medium voltage medium frequency transformers in modern power electronics. To verify this model, transient simulation is performed on a 1.5 kV/1 kHz transformer, revealing voltage overshoot quantitatively between turns and layers of the transformer’s HV winding. Effects of rise time of the input pulse voltage, stray capacitance of the winding insulation, and their interactions on the voltage overshot magnitude are presented. With these results, we propose limiting the voltage overshoot and, thereafter, enhancing medium voltage medium frequency transformer’s insulation capability, which throws light on the transformer’s insulation design. Additionally, guidance on the future studies on aging and endurance lifetime of the medium voltage medium frequency transformer’s insulation could be given.

Design Of All-Normal Dispersion With Ge11.5As24Se64.5/Ge20Sb15Se65 Chalcogenide PCF Pumped At 1300nm For Supercontinuum Generation

Supercontinuum spectrum generation is a process in which laser beam in femtoseconds and high power (kilowatts) is converted into a broad-spectrum beam of light after passing through a specific environment. Of course, achieving this range comes with many limitations. In this paper, photonic crystal fibers are used as a substrate for input pulse due to the ability to control dispersion and loss, and creating single-mode operating conditions. One of the main factors for the formation of supercontinuum spectra of injection pulses is maintaining the nonlinear performance of this type of fiber by controlling the effective mode area and also using chalcogenides (nonlinear coefficients about 100 times higher than silica) in their structure. In the proposed structure, a photonic crystal fiber with silica base element and air cavities with hexagonal structure with the center of Ge11.5As24Se64.5 chalcogenide element have been used to provide the nonlinear property of the structure. Also, in this structure, a ring of Ge20Sb15Se65 chalcogenide elements has been used to reduce the effective mode region and create a flat dispersion curve at a wavelength of 1300 nm (second telecommunication window). The input pulse power is 10 kW and its width is 50 femtoseconds, which has caused the range of the supercontinuum from 800 nm to 1900 nm. This structure can be used to provide the required wavelengths as a carrier in a wavelength division multiplexing (WDM).

BEHAVIORAL FUNCTIONS IMPLEMENTATION ON SPIKING NEURAL NETWORKS

The question of behavioral functions modeling of animals (in particular, the modeling and implementation of the conditioned reflex) is considered. The analysis of the current state of neural networks with the possibility of structural reconfiguration is carried out. The modeling is carried out by means of neural networks, which are built on the basis of a compartmental spiking model of a neuron with the possibility of structural adaptation to the input pulse pattern. The compartmental spike model of a neuron is able to change its structure (the size of the cell body, the number and length of dendrites, the number of synapses) depending on the incoming pulse pattern at its inputs. A brief description of the compartmental spiking model of a neuron is given, and its main features are noted in terms of the possibility of its structural reconfiguration. The method of structural adaptation of the compartmental spiking model of the neuron to the input pulse pattern is described. To study the work of the proposed model of a neuron in a network, the choice of a conditioned reflex as a special case of the formation of associative connections is justified as an example. The structural scheme and algorithm of formation of a conditioned reflex with both positive and negative reinforcement are described. The article presents a step-by-step description of experiments on the associative connection’s formation in general and conditioned reflex (both with positive and negative reinforcement), in particular. The conclusion is made about the prospects of using spiking compartmental models of neurons to improve the efficiency of the implementation of behavioral functions in neuromorphic control systems. Further promising directions for the development of neuromorphic systems based on spiking compartmental models of the neuron are considered.