Operating Frequency Range Research Articles

Thin active region HgCdTe-based quantum cascade laser with quasi-relativistic dispersion law.

HgCdTe is promising as a material to solve a problem of the development of semiconductor sources with an operational frequency range of 6-10 THz due to the small optical phonon energies and electron effective mass. In this study, we calculate the dependence of the metal-metal waveguide characteristics on the number of cascades for the 3-well design HgCdTe-based quantum cascade laser at 8.3 THz. It is shown that four cascades are sufficient for lasing at a lattice temperature of 80 K due to the large gain in the active medium. The results of this study provide a way to simplify the fabrication of thin active region HgCdTe-based quantum cascade lasers for operation in the range of the GaAs phonon Reststrahlen band inaccessible to existing quantum cascade lasers.

Application of harmonic included CPL‐QPHD model of GaN device for broadband PA design

In this work, a harmonic included canonical piecewise linear (CPL) function based quadratic poly-harmonic distortion (QPHD) model is presented. The proposed model employs the framework of the standard QPHD model, making use of the CPL functions for interpolation of the amplitude of the dominant input signal. Compared with the standard QPHD model, the model described in this work is able to predict transistor behavior at different levels of input powers with one single set of model coefficients. The harmonic information has also been added in this model to make it more complete. The model is validated in terms of both DC and RF behavior through simulated data of a 10 W gallium nitride (GaN) high-electron-mobility transistor (HEMT) over a wide range of load conditions and power levels. In addition, the model is implemented in advanced design system (ADS) with frequency-defined device (FDD), and applied for a broadband power amplifier (PA) design. Chebyshev low-pass topology is used for both input and output matching network design. Finally, a broadband PA is implemented with an average power added efficiency of 66.23%, an average power of 41.09 dBm, and an average gain of 13.09 dB across the operating frequency range from 0.6 to 1.7 GHz. The simulation results of the harmonic included CPL-QPHD model are highly matched with the measurement results of the designed PA, demonstrating the feasibility of applying the proposed model for broadband PA design.

Design of C band Bandpass Filter using Fractal based Symmetrical Ring Resonator

Symmetrical ring resonator metamaterial along with fractal boundary is proposed for Band Pass Filter (BPF) design in this paper. A combination of symmetrical ring resonators and vias is used for designing a bandpass filter. Bandpass filter with low insertion loss, better fractional bandwidth even at higher frequencies is achieved by using moore fractal applied symmetrical ring metamaterial resonators along the microstrip transmission line. The operating frequency range of the simulated filter is in the C-band between 5.47 GHz - 6 GHz having fractional bandwidth (FBW) of 9.25% and with a minimum insertion loss of 1.2 dB. Application of moore fractal to the above implementation improved the bandwidth of the filter. Fractal applied symmetrical ring resonator simulated filter operates in the C-band between 7.15 GHz - 8.15 GHz having FBW of 13%, with a minimum insertion loss of 1 dB. The proposed filter is simulated, fabricated and S-parameters are measured using network analyzer N5222A. S-parameters results of fractal applied symmetrical ring resonator filter realized from simulations match closely with those from measurements results performed on prototypes but with a small shift in a frequency range. The measured filter operates in 6.95 GHz - 7.8 GHz having FBW of 11.5%, with a minimum insertion loss of 0.4 dB.

Research on Automotive Bidirectional CLLC Resonant Converters Based on High-Order Sliding Mode Control

A CLLC resonant converter’s gain is easily influenced by the operating frequency, and when the operating frequency is adjusted over a wide range, the efficiency of the converter is greatly reduced. Traditional closed-loop control strategies also have disadvantages such as slow dynamic response and vulnerability to load. In this paper, a high-order sliding mode control (SMC) design method is proposed based on the current problems and the characteristics of automotive CLLC resonant converters. A sliding mode surface based on the output voltage characteristics of the CLLC converter includes higher-order differential terms for voltage and current and an error integral term for the output voltage, which reduces the operating frequency range of the converter and improves its dynamic responsiveness, thus increasing its efficiency. In order to verify the accuracy of the algorithm, a simulation model is built in MATLAB to verify the stability of the controller by varying the input voltage and the magnitude of the load and to verify the dynamics by abruptly varying parameters such as load and voltage. Comparing high-order SMC with PID control also shows that high-order SMC is more suitable for automotive converters.

A programmable digital metasurface structure designed using ANN technique

ABSTRACT In this paper, an 8-bit programmable digital metasurface is designed in the operating frequency range from 4 to 7 GHz. A monopole antenna operating at 5 GHz is characterised by using a metasurface structure as the ground plane. Various combinations of the metasurface structure are examined by altering the state of each unit-cell between ‘ON (1)’ and ‘OFF (0)’ in the coding matrix. The purpose of the 8-bit programmable digital metasurface is to control the electromagnetic wave effectively in the frequency range of interest. Dynamically controllable metasurface structure is utilised to change the unit cells’ configurations. In addition, the proposed adjustable metasurface is capable to control the monopole antenna directivity, gain and main lobe magnitude, efficiently. According to various via conditions, different metasurface-based antenna parameters such as return loss (S11), radiation pattern, directivity and surface current distribution are investigated by means of the commercial numerical simulation software, CST microwave studio. Employing the simulation results of the metasurface-based antennas, the artificial neural network (ANN) data set is obtained. 128 activation conditions are trained and tested by Levenberg Marquart learning algorithm. During the ANN procedure, MATLAB is used to obtain accurate results by changing the rate of test and training data set.

Machine learning guided electrochemical sensor for passive sweat cortisol detection

A noninvasive sensor was developed on a flexible, nano-porous substrate with the capability to detect cortisol passively from human sweat. A Machine Learning (ML) algorithm was also developed to analyze sensor data to detect rising and falling trends of cortisol with time, which can potentially inform the wearer of rising or falling cortisol levels. Sensor response was measured by Electrochemical Impedance Spectroscopy (EIS) assay with spiked synthetic sweat within the physiological concentration range of cortisol, for which responses to low, medium, and high concentrations were significant. Calibration studies established a dynamic range of 8–140 ng/ml and EIS demonstrated a dose-dependent response and operational frequency range of 100–500 Hz. Inter-assay and intra-assay variations were below 20%. One-way ANOVA and post hoc Tukey test established significant response (p < 0.05) to different concentrations of cortisol. EIS was performed with dosing ranging from high-low and low-high concentrations of cortisol, to simulate rising and falling cortisol levels over time. Rate of change of response to shifts in cortisol concentration was used to train a weighted K nearest neighbor (KNN) machine learning algorithm to detect and classify increasing and decreasing cortisol in sweat. Accuracy was validated to be 100% by k means cross validation. Sensor analysis of sweat samples from human subjects showed a 100% accuracy in testing with the algorithm along with a 100% True positive and 0% False negative rate, thus showing that a wearable sweat sensor can be used with ML to detect rising and falling trends in cortisol for on demand, noninvasive sensing.

Electrothermal Design of SIW Slot Antenna Array With Fin-Shaped Heatsink Enclosed

In this article, an electrothermal co-design of substrate integrated waveguide (SIW) slot antenna array combined with fin-shaped heatsink is proposed. The antenna array is constructed by 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times8$ </tex-math></inline-formula> SIW slot elements. The heatsink structure above the antenna array not only improves the radiation performance of the antenna array but also enhances the electromagnetic compatibility (EMC) and the heat dissipation capability of the whole structure. The measured realized gains over the operating frequency range increase from 15.4–18.1 to 16.1–19.7 dBi when the heatsink is mounted on the antenna array. Meanwhile, the enclosed heatsink reduces the hotspot temperature rise of the system by 57%. The measured results are in good agreement with the simulated ones.

Safety analysis of 2-pin capacitor as 4-pin capacitor with frequency response

This paper presents an experiment to verify the safety effect of resolving an open capacitor failure by 4-pin capacitor structures or 2-pin capacitor structures by cut the copper pattern of the printed circuit board (PCB). Both solutions to the problem of open capacitor failure do not affect the next part of the circuit or devices in the operating frequency range of 100 kHz to 500 kHz. This research analyses the effect of using a 2-pin capacitor by cutoff the printed circuit board. The results of parallel patterns of copper stripes were analyzed at different stages and frequency responses analysis in the range of 100 kHz to 4.50 GHz based on a frequency response analysis (FRA), which are experimental results of insertion loss (S21) and return loss (S11). Using a conventional capacitor instead of a 4-pin capacitor of RT2010 type did not show any harmful effects from self-oscillation within the circuit or from the external circuit. The accuracy was verified by simulating the computer program and measuring the test circuit.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ЗАЩИТНОГО УСТРОЙСТВА

The protective device (limiter) at the receiver input is an important component, as it ensuresthe safety of the receiver operation in conditions of receiving powerful signals. The results of anexperimental study of a protective device in the 1-4 GHz band are presented. It is shown that theminimum bandwidth losses at a low power level do not exceed 0.63 dB, the maximum bandwidthlosses are 1.23 dB. At an input power of 25 dBm, the protective device operates in a non-linearmode, therefore it creates harmonics of the input frequency. The experimental amplitudefrequencyresponse (AFC) of the protective device, as well as amplitude characteristics at threefrequencies are presented. The experiment to remove the frequency response was carried out on avector analyzer of circuits. The experiment to remove the amplitude characteristics was carriedout using a standard signal generator and a spectrum analyzer at three frequencies: 1 GHz;2 GHz; 4 GHz. Structurally, the protective device is a polycor substrate on which all elementsexcept connectors are placed. The substrate is placed in a frame-type housing and closed with twosealed lids. Type III sockets according to GOST13317- 89 are used as connectors. A schematicdiagram and a brief description of the design are given. The following main parameters have beenachieved: losses do not exceed 1.23 dB in the operating frequency range from 1 to 4 GHz, theoutput signal power at a high input power level (f = 1 GHz; Rvh = 25 dBm) does not exceed12 dBm. The protective device is recommended to be used in the input circuits of communicationreceivers, navigation, radar and electronic warfare.

Accuracy and Agreement of FDTD, FEM and Wave Matrix Methods for the Electromagnetic Simulation of Waveguide Polarizers

Waveguide devices of polarization processing are key elements of modern dual-polarized antenna systems. Such antenna systems carry out polarization transformation and separation of signals with orthogonal polarizations in satellite communications and radar appliances. Well-known electrodynamic methods are used to simulate performance of such devices. This paper investigates the accuracy and mutual matching of wave matrix method with FDTD and FEM. The wave matrix method is based on the theory of scattering and transmission matrices. The main electromagnetic characteristics of a polarizer were obtained through the elements of these matrices. The main characteristics of a polarizer were compared. They include phase difference of orthogonal polarizations, level of voltage standing wave, ellipticity coefficient and level of cross-polarization isolation. Comparison of electromagnetic characteristics was carried out at the example of a waveguide iris polarizer for the operating frequency range from 13.0 to 14.4 GHz. In addition, the process of optimization of electromagnetic characteristics was carried out by changing the geometric dimensions of a polarizer. Calculated by different theoretical methods characteristics were compared and analyzed. Results, which were obtained by considered methods, are in good agreement

Acoustic travelling wave separation in the time domain using electronic time delay circuits and leaky recursion

Acoustic travelling plane wave separation is implemented in the time domain from the sound pressure signals of two closely spaced microphones using analog electronic circuits based on a leaky recursion formulation. The sound pressure and acoustic particle velocity signals at the midpoint between the microphones are estimated from delayed recursive expressions modified for stability by introducing mild loss recursion. The forward and backward travelling wave components are obtained electronically by simple linear combinations of the sound pressure and particle velocity signals. Two travelling wave separation circuits (TWSC) were designed, built, and evaluated from measurements in an acoustic test tube apparatus in the operational frequency range from 710 to 5,680 Hz. The two designs differ in the use of first- or second-order time delay electronic circuits, with performance of the first-order circuit degrading with increasing frequency. Experimental results for the second-order circuit show a travelling wave separation error of -30.4 dB in the operational frequency range, a travelling wave amplitude accuracy within ±0.1 dB in most of the frequency range, with an implementation that offers operation in real-time with low latency, and resilience to unknown initial conditions or similar errors during operation, with typical transient relaxation times of 2 ms, that can be made lower at the expense of reduced accuracy.

A 20.7–43.8-GHz Low Power Reconfigurable ×2/× 3 Frequency Multiplier for Multiple 5G-mm-Wave Bands

A reconfigurable injection-locked frequency multiplier (RE-ILFM) with both frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 2$ </tex-math></inline-formula> doubler mode (DM) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 3$ </tex-math></inline-formula> tripler mode (TM) is proposed to increase both the operation frequency range and power efficiency. The proposed wideband RE-ILFM has common input and output ports by switching the working DM and TM without any calibration. For TM, harmonic suppression technology (HST) composed of notch filtering and transformer injection-coupling network is presented to optimize the harmonic rejection. For DM, an injection device composed of push-push pair operates in class-C to reduce power consumption and improve second-order harmonic current. Moreover, the concept of a dual core with multiple tanks is first introduced into ILFM, which can effectively improve the magnitude of output signal compared with traditional methods. The proposed RE-ILFM is designed and fabricated in a 55-nm CMOS process. The measurement results show that under a 0-dBm differential injection power, the RE-ILFM can achieve the bandwidth from 20.7 to 43.8 GHz, i.e., 71.6% with a good harmonic rejection of better than 27-dB using HST. From 22 to 30 GHz and 35.4 to 42 GHz for 28 and 39-GHz mm-wave fifth-generation bands, the RE-ILFM can achieve a differential output power of −5.9 to −14.06 dBm and −9.38 to −13.48 dBm with a low power consumption of 12 and 9.6 mW, respectively. The measured phase noise degradation is around 9.5 and 6 dB, which is close to the theoretical value.

Analytical Investigation of Sound Radiation from Functionally Graded Thin Plates Based on Elemental Radiator Approach and Physical Neutral Surface

This paper analyzes the sound radiation behavior of a clamped thin, functionally graded material plate using the classical plate theory and Rayleigh Integral with the elemental radiator approach. The material properties of the plate are assumed to vary according to the power-law distribution of the constituent materials in the transverse direction. The functionally graded material is modeled using a physical neutral surface instead of a geometric middle surface. The effects of the power-law index, elastic modulus ratio, different constituent materials, and damping loss factor on the sound radiation of functionally graded plate are analyzed. It was found that, for the considered plate, the power-law index significantly influences sound power level and radiation efficiency. There exists a critical value of the power-law index for which the corresponding peak of sound power level is minimum. In a wide operating frequency range, approximately 500–1500 Hz, this research suggests that the radiation efficiency is lower for the power-law index equal to 0 and 1. However, for very low frequencies (less than 250 Hz), the power-law index does not affect radiation efficiency significantly. Further, as the modulus ratio increases, the sound power peak decreases for a given power-law index. For the given material constituents of the functionally graded plate, the different values of damping loss factors do not significantly influence radiation efficiency. However, the selection of material constituents affects the radiation efficiency peak.

Design and Analysis of CMOS Dynamic Comparator for High-Speed Low-Power Applications Using Charge Sharing Technique

Analog–digital converters (ADCs) are electronic circuits that convert continuous time signals into digital signals (binary data) for analyzing, estimation, and transmission. Transceivers use ADC in the baseband stage of receiver to convert the analog signals to digital form for further signal processing. At high-frequency applications, like millimeter wave applications, the ADC consumes more power due to the high sampling rate with respect to the increased bandwidth. In this article, a novel dynamic comparator is presented with delay and power analysis for the design. The expression is derived for all operational regions of the transistor. The new design is proposed for low-power consumption and reduced delay of the circuit. The novel design overcomes the drawbacks of the less operating frequency range, high latency, and more power dissipation of existing comparator designs. The proposed low-power dynamic comparator is simulated with 45 nm CMOS technology that provides total power dissipation of 33.92 µW, delay of 19.71 ps, and energy per conversion of 0.19 fJ/conv. with a supply voltage of 1 V.

Design of a Compact UWB-MIMO Antenna with Isolation Enhancement through Extended Elliptical Ground Plane

This paper deals with the design of a Multiple Input Multiple Output (MIMO) antenna for UWB applications. It is composed of two identical radiating elements (parallel monopoles) symmetrically arranged on a FR-4 substrate. The monopoles are closely spaced (about 0.2 Lambda, center to center). A decoupling mechanism based on vertical extension of the Ground plane with elliptical edges (stub) allows to achieve high isolation (&gt;20 dB). Further, the designed system presents good diversity performance, as the obtained Envelope Correlation Coefficient is less than 0.01. The antenna array is compact (36x30 mm2), with ultra-wide operating frequency range (2.6 to 10.8 GHz). Simulations and measurements demonstrate good agreement. The obtained results make the proposed structure a good candidate for any UWB applications and modern wireless communications systems thanks to its wide frequency band, compactness and performance.

A Wideband High-Gain Microstrip Array Antenna Integrated with Frequency-Selective Surface for Sub-6 GHz 5G Applications.

This paper presents a wideband and high-gain rectangular microstrip array antenna with a new frequency-selective surface (FSS) designed as a reflector for the sub-6 5G applications. The proposed antenna is designed to meet the US Federal Communications Commission (FCC) standard for 5G in the mid-band (3.5–5 GHz) applications. The designed antenna configuration consists of 1 × 4 rectangular microstrip array antenna with an FSS reflector to produce a semi-stable high radiation gain. The modeled FSS delivered a wide stopband transmission coefficient from 3.3 to 5.6 GHz and promised a linearly declining phase over the mid-band frequencies. An equivalent circuit (EC) model is additionally performed to verify the transmission coefficient of the proposed FSS structure for wideband signal propagation. A low-cost FR-4 substrate material was used to fabricate the antenna prototype. The proposed wideband array antenna with an FSS reflector attained a bandwidth of 2.3 GHz within the operating frequency range of 3.5–5.8 GHz, with a fractional bandwidth of 51.12%. A high gain of 12.4 dBi was obtained at 4.1 GHz with an improvement of 4.4 dBi compared to the antenna alone. The gain variation was only 1.0 dBi during the entire mid-band. The total dimension of the fabricated antenna prototype is 10.32 λo × 4.25 λo ×1.295 λo at a resonance frequency of 4.5 GHz. These results make the presented antenna appropriate for 5G sub-6 GHz applications.

Sub-6 GHz band massive MIMO antenna system for variable deployment scenarios in 5G base stations

A compact massive multi input multi output (MIMO) antenna system with 1 × 4 (sector) subarray configuration operating at sub-6 GHz range for 5th generation (5G) base stations has been designed and analysed in various geometries (rectangular, triangular, and hexagonal). The capacity of the system can be increased by more than 10 times whereas the energy efficiency can be increased 100 times using the massive MIMO system (Larsson et al. in IEEE Commun Mag 52(2):186–195, 2014). A maximum of 5 sectors has been used, with each sector comprising of 1 × 4 subarray elements. Each sector consists of three layers, in which 1 × 4 patches are located on its top layer whereas it’s feeding network and ground plane are placed at the bottom layer and middle layer respectively. The entire system can operate in two modes, individual port operation and massive MIMO array operation with beam steering capabilities. The measured bandwidth of the system is 140 MHz that covers the frequencies from 3.36 to 3.50 GHz in sub-6 GHz band. The overall dimension of a unit subarray in terms of length, width and height is 280.5 × 56.1 × 2 mm3. The gain of an individual port is found to be 12.77 dBi and the overall gain of a single panel with 5 sectors arranged in rectangular form is 19.73 dBi. Mutual coupling among all the ports has been kept less than − 16 dB. The operating frequency range of the antenna array system is chosen in the range of 3.3–3.8 GHz, as this band has been allocated and targeted across the globe to enable 5G in Sub-6 GHz band.

Optimization for piezoelectric energy harvesters with self-coupled structure: A double kill in bandwidth and power

Vibration energy harvesting is promising to supply power autonomy for many electronic devices. This paper proposes a novel nonlinear piezoelectric energy harvester with a two-degree-of-freedom self-coupled structure. The operating frequency range and the power output of the new harvester is enhanced simultaneously compared with the conventional stopper-based nonlinear energy harvester. The dynamic model of the self-coupled structure is established, and then the bucket hat-like elastic potential energy function of the structure is obtained, which accounts for the superior performance of the harvester. Moreover, an optimization methodology for developing the nonlinear piezoelectric energy harvester was proposed. The conventional and novel energy harvesters were designed, optimized, and fabricated. Experimental results indicate that the maximum output power of the novel energy harvester can be enhanced to 3.54 times of that of the conventional energy harvester with a stopper structure. Besides, the working bandwidth is broadened from 4.7 Hz to 5.2 Hz. It is expected that this work is devoted to the future improvement of vibration energy harvesters in practical applications.

Single-Layer Planar Monopole Antenna-Based Artificial Magnetic Conductor (AMC)

In this paper, a coplanar waveguide (CPW)-fed patch antenna is fabricated on a layer of metasurface to increase gain. The antenna is fabrication on Roger substrate with a thickness of 0.25 mm, with the overall dimension of the proposed design being 45 × 30 × 0.25 mm3. The size of the patch antenna is 24 × 14 × 0.25 mm3, and the AMC unit cell is 22 × 22 × 0.25 mm3. This metasurface is designed based on the split-ring resonator unit cells forming an array of the artificial magnetic conductor (AMC). Meanwhile, the antenna operation on 3.5 GHz is enabled by etching a split-ring resonator slot on the ground plane with a small gap to enhance antenna gain and improve impedance bandwidth when integrated with a metasurface. This simulation planer monopole antenna is applied for 5G application. The experimenter test is applied for the antenna performance in terms of return loss, gain, and radiation patterns. The operating frequency range with and without MTM is from 3.41 to 3.68 GHz (270 MHz) and 3.37 to 3.55 GHz (180 MHz), respectively, with gain improvements of about 2.7 dB (without MTM) to 6.0 dB (with MTM) at 3.5 GHz. The maximum improvement of the gain is about 42% when integrated with the AMC. The AMC has solved several issues to overcome the typical limitation in conventional antenna design. A circuit model is also proposed to simplify the estimation of the performance of this antenna at the desired frequency band. The proposed design is simulated by CST microwave studio. Finally, the antenna is fabricated and measured. Result comparison between simulations and measurements indicates a good agreement between them.

High Gain Compact UWB Antenna for Ground Penetrating Radar Detection and Soil Inspection.

An ultrawide bandwidth (UWB) antenna for ground-penetrating radar (GPR) applications is designed to check soil moisture and provide good-quality images of metallic targets hidden in the soil. GPR is a promising technology for detecting and identifying buried objects, such as landmines, and investigating soil in terms of moisture content and contamination. A paddle-shaped microstrip antenna is created by cutting a rectangular patch at one of its diametrical edges fed by the coplanar waveguide technique. The antenna is loaded by stubs, shorting pins, and a split-ring resonator (SRR) metamaterial structure to increase the antenna’s gain and enhance the bandwidth (BW) towards both the lower and higher end of the working BW. The antenna’s performance in soil inspection is studied in terms of the operating frequency range, different types of soil, different distances (e.g., 50 cm) between the antenna arrays and soil, S-parameters, and gain. Following this, the antenna’s ability to find a metallic target in the soil is tested, considering different array numbers, multi-targets, and locations. The antenna is designed on a thin layer of economic polytetrafluoroethylene (PTFE) substrate with dimensions 50 × 39 × 0.508 mm3 and works in the frequency range 1.9–9.2 GHz. In addition, two more resonances at 0.9 and 1.8 GHz are also achieved; hence, the antenna works for more than two application bands, such as the ISM- and L-bands. The measurement results validated excellent agreement with the simulated results. Furthermore, the recommended antenna offering a high gain of about 10.8 dBi and maximum efficiency above 97% proved able to discriminate between hidden objects and even recognize their shapes. Moreover, the reconstructed images show that the antenna can detect an object in the soil at any location.