GHz Operating Frequency Research Articles

A Three-Stage Dynamic Comparator for SAR ADC Optimized for Reduced Kickback Noise and Ultra-Low Delay

This paper presents a novel footless single clock-phase three-stage comparator with internally generated regenerative voltage signals for low kickback noise and high speed. The preamplifier and clocked latch topology of dynamic comparators are considered in this brief. The proposed design has been compared by analyzing and optimizing three state-of-the-art comparator designs: Modified StrongARM, Miyahara’s and Three-Stage. These designs are simulated using the 40[Formula: see text]nm CMOS technology process. The area of the proposed comparator is 28.025[Formula: see text][Formula: see text]m2. When simulated in the SPICE-based simulator HSPICE, under typical performance conditions of 0.9[Formula: see text]V supply voltage, 25∘C, 1 GHz operational frequency, typical process corner (tt), and 1[Formula: see text]mV differential voltage, the proposed comparator produces the best post-layout results, with a minimum delay of 59.9[Formula: see text]ps from meta-stability analysis, energy per comparison of 0.175[Formula: see text]pJ/comparison and a kickback noise of 44.55 [Formula: see text]A. The proposed design also shows a significant improvement in the measured performance parameters over the other state-of-the-art dynamic comparators that have been discussed in this brief. The obtained results show that the proposed comparator is appropriate for 12-bit Successive Approximation Resister Analog-to-Digital Converters (SAR-ADCs) in IoT applications.

Phase shifter intelligent reflective surface design for 2.4 GHz

In this study, an intelligent reflective surface (IRS) design consisting of a 3x4 patch surface that intentionally changes the phase angles of incoming signals for the 2.4 GHz operating frequency is presented. In the design of this IRS, FR-4 is chosen as the dielectric material, and copper is used to create both the reflecting elements and the ground plane. Phase shifting characteristic is achieved by using varactor diodes on the designed two-dimensional surface. In order to test the behaviour of the IRS, a horn antenna is also designed to be used as a source with the ANSYS HFSS (v21) program. The obtained results are presented in terms of return loss and gain values of the IRS. The results of the simulations reveal that the phase angles of the incoming signals can be adjusted as expected by changing the capacity values of the varactor diodes modelled by their equivalent circuits on the IRS.

Antena Dwi Port Dwi Pengutuban Bulat terinspirasi Bahan Meta untuk Sistem Komunikasi Satelit Kecil

This paper presents a dual circular polarized C-band patch antenna for a small satellite communication system The antenna consists of two different annular patch structure with three split ring resonators. The antenna is designed considering space environment and the smallest form of satellite structure. The antenna is fabricated space qualified substrate material Rogers 5880 with overall dimension of 85.22× 48.59 × 1.575 mm3. The antenna achieves circular polarization at 5.1 GHz and 5.2 GHz frequency for port 2 and port 1, respectively. The split ring resonator structures contribute to enhance antenna gain and axial beamwidth. Realized gain of 7.29 dB and 7.33 dB are achieved at 5.1 GHz and 5.2 GHz operating frequency with 3dB axial beamwidth of 170 ̊ and 153 ̊ , respectively. Antenna size and performance show that the antenna can be a potential candidate for smooth operation of small satellite communication system.

A Novel Dual-Band Circularly Polarized Wearable Antenna.

A circularly polarized wearable antenna operating in the 2.45/5.8 GHz ISM dual bands is proposed, which consists of a coplanar waveguide-fed rectangular monopole antenna and two parasitic branches. The monopole rectangular radiation patch can generate 2.45 and 7 GHz frequency bands and has linear polarization characteristics. By adding L-shaped parasitic branches and L-like grounded branches on both sides of the monopole, the 7 GHz operating frequency band can be moved to the 5.8 GHz frequency band, and circular polarization characteristics can be achieved in both the 2.45 and 5.8 GHz frequency bands. The size of the antenna is 48.7 mm × 42.1 mm × 1.016 mm. The simulated -10 dB impedance bandwidths of the antenna are 1.8-2.66 GHz and 5.48-6.98 GHz, respectively. The 3 dB axial ratio bandwidths are 2.34-2.67 GHz and 5.58-6.39 GHz, respectively, and it has dual-band circular polarization characteristics. In addition, the radiation characteristics of the antenna and its safety performance near the human body were analyzed. The antenna prototype has been constructed, and the measurement and simulation results have good consistency. The proposed antenna is suitable for application in wearable devices.

Multi-Objective Optimization for Rapid Identification of Novel Compound Metals for Interconnect Applications.

Interconnect materials play the critical role of routing energy and information in integrated circuits. However, established bulk conductors, such as copper, perform poorly when scaled down beyond 10 nm, limiting the scalability of logic devices. Here, a multi-objective search is developed, combined with first-principles calculations, to rapidly screen over 15,000 materials and discover new interconnect candidates. This approach simultaneously optimizes the bulk electronic conductivity, surface scattering time, and chemical stability using physically motivated surrogate properties accessible from materials databases. Promising local interconnects are identified that have the potential to outperform ruthenium, the current state-of-the-art post-Cu material, and also semi-global interconnects with potentially large skin depths at the GHz operation frequency. The approach is validated on one of the identified candidates, CoPt, using both ab initio and experimental transport studies, showcasing its potential to supplant Ru and Cu for future localinterconnects.

Synthesis and fabrication of proto-type microstrip patch antenna by using microwave dielectric ceramic nanocomposite material for C-band application

The microwave dielectric properties of Zn(1-x)TixAl2O4 (ZTA) ceramic nanomaterials were investigated with a focus towards their use as wireless antennas. The ZTA nanoparticles were prepared using the sol-gel technique at 700 °C for one hour. The inclusion of titanium decreased the nanomaterials' crystallite size and surface shape, which influenced their dielectric permittivity (εr). Based on the tested material and microwave antenna theory, ZTA was used to fabricate wireless patch antennas, which were then examined using a PNA series network analyzer. The measured results reveal that the return loss and impedance bandwidths of the antenna were −44.83 dB simulated and −34.88 dB measured, and 240 MHz for simulated and 220 MHz for measured, respectively. At 5.1 GHz operating frequency, the Zn0.94Ti0.06Al2O4-based patch antenna demonstrated an exceptional combination of return loss (-34.88 dB), compact size (9.3× 6.3 mm2), and broad bandwidth (220 MHz) as well as VSWR<2. Ultimately, the fabricated antenna showcases a gain of 4.24 decibels and a directivity of 5.97 decibels.

CMOS Voltage-Controlled Oscillator with Complementary and Adaptive Overdrive Voltage Control Structures

This paper displays a voltage-controlled oscillator (VCO) with high performance implemented in 0.18 µm CMOS. The proposed CMOS VCO adopts a current-reused method, analog coarse and fine tuning mechanisms, and an adaptive overdrive voltage control structure to increase the overall performance, such as the power dissipation, phase noise, and tuning range, and has a robust start-up condition. The current-reused complementary structure with higher transistor transconductances is to save power consumption; the analog coarse and fine tuning mechanisms are to effectively widen the tuning range; and the adaptive overdrive voltage control technique is to change the transconductances of the transistors to improve power consumption by reasonably biasing the gate and body terminals in a class-AB mode to adjust the threshold voltage of the NMOS transistors. The proposed CMOS VCO adopts the class-AB mode to improve the overall performance and the start-up condition. The figure-of-merit (FOM) and FOM with tuning range (FOMT) are used in evaluating the CMOS VCO performance. The measured phase noise at 1 MHz and 10 MHz offsets is –130.34 dBc/Hz and –150.96 dBc/Hz at the 3.38 GHz operating frequency, respectively. The proposed CMOS VCO has a tuning range between 2.85 and 3.62 GHz corresponding to 23.8% for the fifth-generation (5G) wireless communication applications. The proposed CMOS VCO core using a 1.4-V supply consumes 7.5 mW DC power. The FOMs and FOMTs at 1- and 10-MHz offsets are −192.2, −192.8, −199.7, and −200.3 dBc/Hz, respectively, from the 3.38 GHz output frequency.

WiFOG: Integrating deep learning and hybrid feature selection for accurate freezing of gait detection

This study investigates the feasibility of utilizing non-invasive WiFi sensing using the 4.8 GHz operating frequency band of the 5 G spectrum, which is suitable for Internet of Things applications. We propose WiFOG: a WiFi CSI system for detecting FOG in PD leveraging deep learning and wireless channel characteristics collected by wireless devices such as a radio frequency signal generator, a network interface card, and dipole antennas. The raw data for several activities, including sitting, slow-walking, fast-walking, voluntary stopping, and FOG episodes, is collected. Regress feature engineering is performed in which discrete wavelet transforms is used for signal denoising and Hilbert-Huang transforms for feature extraction. Further, we propose hybrid feature selection techniques based on whale optimization, recursive feature elimination, and select form models for dimensionality reduction. Moreover, we propose a deep-gated recurrent network (DGRU) for activity classification and FOG detection and compared the results with the state-of-the-art approaches in the existing work. The results show our proposed scheme surpasses existing FOG detection with a total improvement of approximately 4% in accuracy and a 29% reduction in training time.

Amplitude Control Loop to Compensate for I/Q Mismatch in an Accurate Quadrature LC Oscillator

In this paper, a novel parallel-coupled quadrature LC oscillator (PC-QO) is presented that can automatically eliminate imbalances of output phase and amplitude resulting from mismatches in the LC tanks. The method of using unequal coupling factors in a parallel-coupled quadrature oscillator is the base of this design; canceling the phase and amplitude errors takes place by tuning the imbalanced coupling factor using tuneable tail currents. First, the proposed circuit senses the amplitude error and then adjusts the coupling factors according to the situation. We show that using the inversely proportional coupling factors can eliminate the phase and amplitude error simultaneously. In other words, this design uses the amplitude control loop to cancel the phase and amplitude error. The circuit has been simulated using TSMC 0.18 CMOS practical model to confirm the high accuracy of the analysis and capability of the canceling [Formula: see text]/[Formula: see text] mismatch technique. The simulation results show that the phase noise of the proposed quadrature voltage controlled oscillator (QVCO) is −123.9 dBc/Hz at 1[Formula: see text]MHz offset from 4.4[Formula: see text]GHz operation frequency. The total power consumption of the QVCO is 3.4[Formula: see text]mW.

Catalytic efficiency of encapsulated coupled doped Zn-Ni TiO2 nanocatalyst for the removal of organic pollutants and free radical assay

ABSTRACT In this study, encapsulation of polymer polyvinylpyrrolidone and plant Tinospora cordifolia was done in coupled doped zinc-nickel titanium dioxide (TiO2) nanoparticles (Zn-Ni TDNPs) via using microwave-assisted method with 2.45 GHz operating frequency and power of 700 Watts for about 120 s. The catalytic efficiency of encapsulated TDNPs was analysed through photocatalytic activity against methyl orange (MO) and methylene blue (MB) dyes, which are considered aquatic pollutants released by textiles dyes. Also, these encapsulated TDNPs were installed in scavenging activity to eliminate the free radicals 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Various physicochemical properties of the encapsulated TDNPs were analysed using different characterisation techniques. The encapsulated TDNPs had a tetragonal crystal lattice structure, with an average particle size ranging from 68 to 83 nm and spheroidal morphology. The bandgap of the encapsulated coupled doped Zn-Ni TDNPs was found to be between 3.48 and 3.55 eV. Under UV radiation, the photocatalytic activity against MO and MB dyes increased with an increase in TDNPs catalyst dosage, and in rare cases, the rate of degradation reached up to 98% for both dyes. Additionally, the encapsulated coupled doped Zn-Ni TDNPs demonstrated antioxidant activity of up to 89% against the DPPH assay.

A low phase noise quadrature VCO using super‐harmonic coupling technique in 65‐nm CMOS technology

SummaryThis paper presents a new low phase noise (PN) quadrature voltage controller oscillator (QVCO), which includes four class C LC‐VCOs oscillated at 13 GHz operating frequency with 45‐degree phase differences from each other. By combining the second harmonics (super‐harmonic) of the LC‐VCOs, the quadrature outputs with low PN at 26 GHz are generated. To assess the performance of the proposed QVCO, post‐layout simulations are performed in 65‐nm CMOS technology with a 0.6 V supply voltage. The post‐layout results represent that the proposed circuit has 26 GHz quadrature outputs with the PN of −116.4 at 1 MHz offset frequency. Also, the proposed QVCO occupies an area of 0.366 mm2 and consumes 10.4 mW of power. Therefore, the proposed QVCO is a good candidate for 5G applications.

A Co-Linearly Polarized Shared Radiator-Based Full-Duplex Antenna With High Tx-Rx Isolation Using vias and Stub Resonator

In this paper, a co-linearly polarized shared radiator (SR) based in-band full-duplex (FD) microstrip antenna with high Tx-Rx isolation is proposed. The Tx and Rx terminals of the proposed FD antenna are designed on a single patch, where a series of vias are loaded in the central line of the patch followed by two L-shaped stubs at either end, which leads to high Tx-Rx isolation (≈60 dB). The via loading makes the Tx and Rx antennas individually operate in TM0,1/2 mode. The proposed SR-FD antenna demonstrates Tx-Rx isolation of 60.8 dB at 5.9 GHz operating frequency. Both Tx and Rx terminals of the FD antenna exhibit identical radiation property with peak realized gain of 6.65 dBi and co-to-cross polarization isolation >18 dB. The working mechanism of the proposed FD antenna is explained by both EM and circuit simulation, as well as verified with measurements on the fabricated prototype. The proposed SR-FD antenna has the merits of being planar, reduced footprint, simple feeding mechanism, and desired isolation bandwidth for IEEE 802.11p which renders it suitable for V2X-ITS application.

Characteristic-Mode-Analysis-Based Compact Vase-Shaped Two-Element UWB MIMO Antenna Using a Unique DGS for Wireless Communication

The modern electronic device antenna poses challenges regarding broader bandwidth and isolation due to its multiple features and seamless user experience. A compact vase-shaped two-port ultrawideband (UWB) antenna is presented in this work. A circular monopole antenna is modified by embedding the multiple curved segments onto the radiator and rectangular slotted ground plane to develop impedance matching in the broader bandwidth from 4 to 12.1 GHz. The UWB monopole antenna is recreated horizontally with a separation of less than a quarter wavelength of 0.13 λ (λ computed at 4 GHz) to create a UWB multiple input and multiple output (MIMO) antenna with a geometry of 20 × 29 × 1.6 mm3. The isolation in the UWB MIMO antenna is enhanced by inserting an inverted pendulum-shaped parasitic element on the ground plane. This modified ground plane acts as a decoupling structure and provides isolation below 21 dB across the 5–13.5 GHz operating frequency. The proposed UWB MIMO antenna’s significant modes and their contribution to antenna radiation are analyzed by characteristic mode analysis. Further, the proposed antenna is investigated for MIMO diversity features, and its values are found to be ECC &lt; 0.002, DG ≈ 10 dB, TARC &lt; −10 dB, CCL &lt; 0.3 bps/Hz, and MEG &lt; −3 dB. The proposed antenna’s time domain characteristics in different antenna orientations show a group delay of less than 1 ns and a fidelity factor larger than 0.9.

Low-loss flexible terahertz photonic crystal fiber

This paper presents a hybrid porous-core flexible photonic crystal fiber (PCF), which has the potential for low-loss guidance of broadband terahertz (THz) waves at low THz bands. Here, the cyclic olefin polymer TOPAS is used for the main material to increase the flexibility of PCF. The central hybrid porous-core area contains a circular and hexagonal design, which reduces the loss of PCF. Simulation results show that the proposed fiber has a very low confinement loss of 3.47 × 10 − 6 dB / cm at 500 GHz operating frequency. The bending loss at a bending radius of 1 cm is as low as 3.2 × 10 − 4 dB / cm. The negligible modal loss facilitates the flexible application to THz systems. Moreover, the fabrication of the proposed PCF design is compatible with widely used methods and technologies, including stacking and drawing, extrusion and drilling. This newly proposed hybrid design of the porous-core region can be considered as an improved version in the research of THz porous-core waveguides.

A duty cycle corrector with dual loop low pass filter for low jitter and fast correction time

In this paper, a duty cycle corrector (DCC) with a dual loop low pass filter (DLLPF) has been proposed to improve correction time and noise characteristics. It shows that the correction time is 4.25 times faster and the fluctuation is 7.86 times lower compared to a conventional DCC with a typical low pass filter. The proposed DCC has been fabricated in a 0.18-μm CMOS technology with a supply voltage of 1.8 V within area of 0.03 mm2. The experimental results show that the operation range is from 800 MHz to 1.6 GHz for input duty cycle variation within 25 % and 75 %. At the 1.6 GHz operating frequency, the measured root-mean-square and peak-to-peak jitters are 1.66 ps and 12.69 ps, respectively.

On the Performance of a Miniaturized Reactive Loaded Monopole Antenna for Ex Vivo Catheter Applications

In this paper, we propose a miniaturized series L-C loaded monopole antenna for catheter application in microwave ablation systems. Initially, a quarter wavelength long monopole antenna (Design1), having length 30 mm (≈ 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> represents the free-space wavelength at 2.4 GHz operating frequency) using series LC loading concept is designed. The initial design is further extended to a miniaturized version (Design2) having length 5 mm (≈ 0.04λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), showing nearly 83% size reduction compared to its former.Both the antennas are designed and simulated by immersing inside high permittivity egg white phantom (ϵ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>r</i></sub> = 63.84). Antenna Design 1 and 2 exhibit good impedance matching ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < –12 dB) at and around the operating frequency with uniform monopolar radiation pattern having co-to-cross isolation of nearly 30-35 dB. Further, the in-phantom Specific Absorption Rate (SAR) values for both antennas are evaluated using simulation and verified with the measured SAR values such as 22 W/kg and 19.6 W/kg for Design1 and 2 respectively, using an in-house experimental setup. Moreover, the microwave ablation property of the proposed antennas is studied using simulated transient thermal gradient which translates to ablation zone formation. Here, Design 2 shows the advantage of having a low invasive diameter of 1.5 mm and near unity aspect ratio (AR) for the ablation zone as compared to Design1.

An S-Band Microstrip Patch Antenna Design and Simulation for Wireless Communication Systems

In this paper, a 3.5 GHz microstrip patch antenna for the future of wireless communication is designed and studied. As a substrate, Rogers RT/Duroid5880 is utilized. This material has a thickness of 0.077mm and a dielectric loss of 2.2. The proposed antenna layout is simulated using the CST studio suite of software programs. This research aimed to achieve a lower return loss, higher gain, lower VSWR, directivity, and improved efficiency. The simulation revealed that the return loss, gain, VSWR, and directivity were correspondingly -13.772 dB, 7.55 dB, 1.5152, and 8.43dBi. The efficiency was 89.56%. This antenna has been developed and assessed for use in various wireless communication applications with a 3.5 GHz operating frequency, which is used as a reference antenna in communication satellites, weather radar, surface ship radar, wireless LAN-802.11b and 802.11g, multimedia applications in mobile TV and satellite radio, optical communications at 1460 to 1530 nm wavelength, and is utilized for other wireless fidelity applications.

Principle and performance analysis of low-power, high-speed, low-noise comparators

This paper studies three different structures proposed in recent years and discusses their advantages and properties respectively. A modified strong-arm latch voltage comparator is adapted to 3GHz operating frequency through additional current paths in the pre-amplifier. A latch-type comparator with a dynamic-biased pre-amplifier (DA) greatly reduces energy and improves noise performance through the stabilization of the input common-mode voltage. An FIA comparator further reduces energy and noise and greatly enhances the delay performance and the robustness of the comparator against different input common-mode voltage.

Selection of Suitable Dielectric Substrate for Miniaturization of Microstrip Patch Antenna Using DGS Fractals

Background: Antennas size reduction with good performance characteristics is an essential part of designing a microstrip patch antenna (MPA) to select a suitable dielectric substrate. Methods: A conventional MPA is designed at 10GHz frequency, and later Minkowski fractal (1st iteration) defected ground structure (DGS) technique is applied for size reduction. The design is made to keep the radiation and reflection characteristics in contention. Results: A miniaturized MPA with 11% size reduction has been simulated using HFSS. The simulation results show the realization and selection of the substrate materials in the design process. Here, five different substrates are judiciously implemented and later compared. The comparison is made based on return loss, bandwidth, impedance, gain and efficiency Conclusion: We found a miniaturized MPA using the proposed first iteration of Minkowski fractal DGS. This MPA is suitable for X-band satellite communication and may be applied in government institutions, civil, military, monitoring weather, air traffic, defence tracking, maritime vessel traffic, etc., due to conformal and planar shape with reduced electrical length at 10GHz operating frequency

Metasurface Radome to Achieve a Wideband High Gain, Low RCS, and Low SLL Antenna

A Phase- and amplitude-adjustable metasurface radome (PAMR) is proposed to achieve a wideband high gain and low radar cross-section (RCS) antenna with arbitrary sidelobe levels (AS-PGMA) at a 9.8 GHz operating frequency. The proposed PAMR is a special multilayer phase gradient metasurface lens whose amplitude distribution is modified based on the Dolph-Tschebyscheff technique. The AS-PGMA simulation results indicate that a high gain, low RCS, and low sidelobe level (SLL) antenna can be achieved over a broad impedance frequency bandwidth of 9.25–10.1 GHz with in-band average values of 17 dB, −7.5dBsm, −20 dB/−27 dB for gain, RCS, and E-/H-plane SLL, which are measured at 9.8 GHz as 17.4 dB, −9dBsm, and −23.02 dB/−27.91 dB, respectively. Additionally, a novel analytical method for calculating the RCS of the proposed PAMR and AS-PGMA is described and verified by measurement and simulation findings. Measurement results show that the E-/H-plane SLL of the AS-PGMA is improved by 12.2 dB/5.1 dB at the operating frequency, respectively, while its gain and RCS reduction are reduced by 1.6 and 2.1 dB, respectively. Moreover, RCS of the AS-PGMA is reduced over an ultrawide bandwidth of 1–20 GHz for orthogonal polarizations. The analysis, simulations, and measurements are all in good agreement.