A new design approach for dual-band power amplifiers based on dual-band HCC and bandpass filter.

This paper introduces a novel design approach based on the dual-band harmonic control circuit and bandpass filter for dual-band power amplifiers. The circuit schematic of the proposed approach is constructed using four resonators and RFC inductors. The first two resonators are dedicated to controlling the second harmonics, while the third and fourth resonators serve as a harmonic blocker, allowing only the main signals to pass through to the load. Subsequently, all components are replaced by circuits based on microstrip elements, forming the proposed OMN. This OMN includes a novel wideband bias circuit, elliptically coupled resonators, and a new dual-band bandpass filter. To ensure compatibility with the transistor, a compensator line has been integrated. As a result, a dual-band power amplifier has been fabricated and measured at two operating frequencies, 2.1 GHz and 2.91 GHz. The measured values for drain efficiency, output power, and power gain at 2.1 GHz are 75.98%, 37.5 dBm, and 12.5 dB, respectively. Similarly, at 2.91 GHz, these values are 75.73%, 37.24 dBm, and 12.24 dB, respectively.

High Transmission All-Optical Combinational Logic Circuits Based on a Nanoring Multi-Structure at 1.31 µm.

The main purpose of this study is to design combinational logic gates based on a novel configuration of insulator-metal-insulator (IMI) nanoring plasmonic waveguides. Plasmonic logic gates are half adder, full adder, half subtractor, full subtractor, and one-bit comparator and are realized in one structure. The performance of the logic circuits is based on constructive and destructive interferences between the input and control signals. The transmission threshold value is assumed to be 0.35 at the resonance wavelength of 1.310 µm. The transmission spectrum, contrast loss (CL), insertion loss (IL), modulation depth (MD), and contrast ratio (CR) are calculated in order to evaluate the structure's performance. The maximum transmission of the proposed structure is 232% for full a adder logic gate, and MD exceeds 90% in all plasmonic combinational logic circuits. The suggested design plays a key role in the photonic circuits and nanocircuits for all-optical systems and optical communication systems. The combinational logic gates are analyzed and simulated using the finite element method (FEM).

Design of dual-band power amplifier using bandstop filter and dual-mode bias circuit for multistandard transceiver systems.

This paper presents a dual-band power amplifier (PA) using a meandered line bandstop filter (BSF). An important challenge addressed in this design is to achieve proper isolation between the operational bands of the amplifier. The proposed BSF provides isolation and efficiency, effectively separating the output power and power gain between the two operational bands. Additionally, a dual-mode bias circuit is designed to serve as an inductor choke and control the second harmonics for both operating frequencies simultaneously. Two dual-band PAs, utilizing LDMOS and GaN HEMT transistors, have been designed using the proposed output matching circuit, which incorporates the BSF, bias circuit, and compensation circuit. The results obtained from both PAs, employing different transistors, are identical. Based on the presented concepts, a dual-band PA with an LDMOS transistor has been fabricated and measured. The measurements reveal an efficiency of 79.23%, an output power of 39.85 dBm, and a power gain of 14.85 dB at a frequency of 0.7 GHz. Similarly, at a frequency of 1.9 GHz, the efficiency is 77.24%, the output power is 38.22 dBm, and the power gain is 13.22 dB.

Investigation of temperature variations on a Class-E inverter and proposing a compensation circuit to prevent harmful effects on biomedical implants.

In this paper, a Class-E inverter and a thermal compensation circuit for wireless power transmission in biomedical implants are designed, simulated, and fabricated. In the analysis of the Class-E inverter, the voltage-dependent non-linearities of Cds, Cgd, and RON as well as temperature-dependent non-linearity of RON of the transistor are considered simultaneously. Close agreement of theoretical, simulated and experimental results confirmed the validity of the proposed approach in taking into account these nonlinear effects. The paper investigated the effect of temperature variations on the characteristics of the inverter. Since both the output power and efficiency decrease with increasing temperature, a compensation circuit is proposed to keep them constant within a wide temperature range to enable its application as a reliable power source for medical implants in harsh environments. Simulations were performed and the results confirmed that the compensator enables significant improvements by maintaining the power and efficiency almost constant (8.46 ± 0.14 W and 90.4 ± 0.2%) within the temperature range of - 60 to 100 °C. Measurements performed at 25 °C and 80 °C with and without the compensation circuit were in good agreement with the theoretical and simulation results. The obtained measured output power and efficiency at 25 °C are equal to 7.42 W and 89.9%.

Narrow-band power dividers with wide range tunable power-dividing ratio.

This paper presents two narrow-band power dividers with a wide range power-dividing ratio based on the two new controlling insertion loss methods, which are low-impedance line and coupling capacitor. Initially, a narrow-band BPF is designed based on the equivalent circuit model and LC equivalent circuit. Then, using the surface current density, it is determined by which part of BPF structure the insertion loss (IL) can be controlled at center frequency. The tunable Wilkinson power dividers (TWPDs) are designed based on IL control components to create a wide range of power-dividing ratios, using only two DC voltages. The center frequency of first designed TWPD is 2.5 GHz, and the power-dividing ratio can be controlled up to 1:45 by variation of two DC voltages from 0 to 8 V. Since the structure of TWPDs are symmetric, the inverse voltages results in the inverted divided power between the output ports. The center frequency of second designed TWPD is 2.52 GHz, and power-dividing ratio can be controlled up to 1:134 by variation of two DC voltages from 1.7 to 4 V. Two proposed TWPDs are fabricated and measured. Comparisons of the measured and simulated results are presented to verify the theoretical predictions.

Low Cost Digital Implementation of Hybrid FitzHugh Nagumo-Morris Lecar Neuron Model Considering Electromagnetic Flux Coupling.

Digital realization of neuron models, especially implementation on a field programmable gate array (FPGA), is one of the key objectives of neuromorphic research, because the effective hardware realization of the biological neural networks plays a crucial role in implementing the behaviors of the brain for future applications. In this paper, a hybrid FitzHugh Nagumo-Morris Lecar (FNML) neuron model with electromagnetic flux coupling is considered, and two multiplierless piecewise linear (PWL) models, which have similar behaviors to the biological neuron, are presented. A comparison between digital implementation results of the original FNML and PWL models illustrates that, the PWL1 model provides a 65% speed-up with an overall saving (in FPGA resources) of 66.2%, and the PWL2 model yields a 71% speed-up with an overall saving of 78.2%.

Optical biosensors using plasmonic and photonic crystal band-gap structures for the detection of basal cell cancer.

One of the most interesting topics in bio-optics is measuring the refractive index of tissues. Accordingly, two novel optical biosensor configurations for cancer cell detections have been proposed in this paper. These structures are composed of one-dimensional photonic crystal (PC) lattices coupled to two metal-insulator-metal (MIM) plasmonic waveguides. Also, the tapering method is used to improve the matching between the MIM plasmonic waveguides and PC structure in the second proposed topology. The PC lattices at the central part of the structures generate photonic bandgaps (PBGs) with sharp edges in the transmission spectra of the biosensors. These sharp edges are suitable candidates for sensing applications. On the other hand, the long distance between two PBG edges causes that when the low PBG edge is used for sensing mechanism, it does not have an overlapping with the high PBG edge by changing the refractive index of the analyte. Therefore, the proposed biosensors can be used for a wide wavelength range. The maximum obtained sensitivities and FOM values of the designed biosensors are equal to 718.6, 714.3 nm/RIU, and 156.217, 60.1 RIU-1, respectively. The metal and insulator materials which are used in the designed structures are silver, air, and GaAs, respectively. The finite-difference time-domain (FDTD) method is used for the numerical investigation of the proposed structures. Furthermore, the initial structure of the proposed biosensors is analyzed using the transmission line method to verify the FDTD simulations. The attractive and simple topologies of the proposed biosensors and their high sensitivities make them suitable candidates for biosensing applications.

A Digital Realization of Astrocyte and Neural Glial Interactions.

The implementation of biological neural networks is a key objective of the neuromorphic research field. Astrocytes are the largest cell population in the brain. With the discovery of calcium wave propagation through astrocyte networks, now it is more evident that neuronal networks alone may not explain functionality of the strongest natural computer, the brain. Models of cortical function must now account for astrocyte activities as well as their relationships with neurons in encoding and manipulation of sensory information. From an engineering viewpoint, astrocytes provide feedback to both presynaptic and postsynaptic neurons to regulate their signaling behaviors. This paper presents a modified neural glial interaction model that allows a convenient digital implementation. This model can reproduce relevant biological astrocyte behaviors, which provide appropriate feedback control in regulating neuronal activities in the central nervous system (CNS). Accordingly, we investigate the feasibility of a digital implementation for a single astrocyte constructed by connecting a two coupled FitzHugh Nagumo (FHN) neuron model to an implementation of the proposed astrocyte model using neuron-astrocyte interactions. Hardware synthesis, physical implementation on FPGA, and theoretical analysis confirm that the proposed neuron astrocyte model, with significantly low hardware cost, can mimic biological behavior such as the regulation of postsynaptic neuron activity and the synaptic transmission mechanisms.