Wide Bandwidth Range Research Articles

Improvement of Servo-Type Jerk Sensor and Its Performance Evaluation

This paper proposes the servo-type jerk sensor for horizontal direction. In the previous research, the servo-type jerk sensor for vertical direction has realized and applied to the anti-vibration apparatus. This paper shows the improvement of the jerk sensor performance by reexamining the servo mechanism. The authors show the desired parameters of the jerk sensor necessary to realize Butterworth filter characteristics and the parameter adjustment methods to realize the desired parameters. By applying the proposed parameter adjustment methods, the proposed jerk sensor achieves the following characteristics; wide range of frequency bandwidth and high sensitivity. The authors also show the feasibility of improving the sensitivity of the proposed jerk sensor by replacing the internal position sensor for the high sensitivity sensor, such as the LASER displacement sensor. Finally, two experimental results show the applicability of feedback controls for a linear slider system and a pneumatic stage system.

Isolation Improvement in UWB-MIMO Antenna System Using Slotted Stub

Multiple-input multiple-output (MIMO) scheme refers to the technology where more than one antenna is used for transmitting and receiving the information packets. It enhances the channel capacity without more power. The available space in the modern compact devices is limited and MIMO antenna elements need to be placed closely. The closely spaced antennas undergo an undesirable coupling, which deteriorates the antenna parameters. In this paper, an ultra wide-band (UWB) MIMO antenna system with an improved isolation is presented. The system has a wide bandwidth range from 2–13.7 GHz. The antenna elements are closely placed with an edge to edge distance of 3 mm. In addition to the UWB attribute of the system, the mutual coupling between the antennas is reduced by using slotted stub. The isolation is improved and is below −20 dB within the whole operating range. By introducing the decoupling network, the key performance parameters of the antenna are not affected. The system is designed on an inexpensive and easily available FR-4 substrate. To better understand the working of the proposed system, the equivalent circuit model is also presented. To model the proposed system accurately, different radiating modes and inter-mode coupling is considered and modeled. The EM model, circuit model, and the measured results are in good agreement. Different key performance parameters of the system and the antenna element such as envelope correlation coefficient (ECC), diversity gain, channel capcity loss (CCL) gain, radiation patterns, surface currents, and scattering parameters are presented. State-of-the-art comparison with the recent literature shows that the proposed antenna has minimal dimensions, a large bandwidth, an adequate gain value and a high isolation. It is worth noticeable that the proposed antenna has high isolation even the patches has low edge-to-edge gap (3 mm). Based on its good performance and compact dimensions, the proposed antenna is a suitable choice for high throughput compact UWB transceivers.

DTMOS Based High Bandwidth Four-Quadrant Analog Multiplier

Analog multiplication circuits are very important block structures which are widely used in analog signal applications. In analog multiplication circuits, low power consumption is expected with wide bandwidth, low nonlinearity and high input range according to supply voltage. In this study, folded Gilbert cell structure was resized using dynamic threshold MOS (DTMOS) transistors and low power consumption and high bandwidth have been obtained. In improver, the bandwidth was obtained at values of 3.63 GHz, temperature variation, total harmonic distortion and intermodulation products of the proposed multiplier were examined. Monte Carlo analysis was performed and error analysis of the dimensioning of the circuit was examined. In summation to the high bandwidth, a low power consumption of 44.5 µW has been achieved and the supply voltage of 0.2 V has been achieved to operate in full-scale input range.

Reduction of UWB Far-End Crosstalk in Microwave and Millimeter-Wave Band of Parallel Periodically Loaded Transmission Lines With Discontinuous Structured Guard Lines

A novel method is proposed to reduce the ultra-wideband (UWB) far-end crosstalk (FEXT) of the parallel microstrips (MSs), in which subwavelength periodically loaded transmission lines (PLTLs) with discontinuous structured guard lines (DSGLs) are appropriately used. The motivation is to innovate a structure to eliminate the FEXT for devices in microwave and millimeter-wave band. In the scheme, the single PLTL has enhanced self-inductance, and the PLTL pairs with interline DSGLs can realize added mutual capacitance and slightly changed mutual inductance, comparing with the conventional MS pairs. Therefore, the equalization of capacitive coupling ratio and the inductive coupling ratio is realized, which dramatically reduce the FEXT in a wide bandwidth range. The lumped parameters are extracted for mechanism validation, then several MS circuits are designed on FR-4 PCB by full-wave simulation. The comparisons with the previous methods indicate that the best cancellation of the FEXT is achieved by the proposed method. To demonstrate the design strategies, MS circuits operating from DC to 40 GHz are designed using the above proposed method and further fabricated on Al2O3 ceramic board of 0.127-mm thickness. The measured results reveal that more than 35-dB FEXT suppression is obtained from DC to Ka-band, indicating the validity of the proposed method.

A Compact High-Efficiency Broadband Rectifier With a Wide Dynamic Range of Input Power for Energy Harvesting

In this letter, a compact high-efficiency broadband microwave rectifier with an extended range of input power is proposed for energy harvesting. In the proposed structure, a novel broadband impedance-matching network is employed to reach high radio frequency (RF) to dc conversion efficiency. The reduction in mismatching loss over a wide bandwidth and input power range is achieved by impedance transformation from three segments of microstrip lines, which leads to a compact design to realize broadband impedance matching. A theoretical analysis and simulations of the proposed rectifier are presented. For validation, a broadband rectifier operating between 2.1 and 3.3 GHz is implemented and tested. The proposed rectifier shows a bandwidth of 44.4% for efficiency over 70% at an input power of 14 dBm. The measured efficiency remains above 50% from 2 to 3.3 GHz with an input power from 4 to 16 dBm. Moreover, the proposed rectifier has a compact size of 31 mm $\times18$ mm.

High-resolution optoacoustic imaging of tissue responses to vascular-targeted therapies.

The monitoring of vascular-targeted therapies via magnetic resonance imaging, computed omography or ultrasound is limited by their insufficient spatial resolution. By taking advantage of the intrinsic optical properties of haemoglobin, here we show that raster-scanning optoacoustic mesoscopy (RSOM) provides high-resolution images of the tumour vasculature and of the surrounding tissue, and that the detection of a wide range of ultrasound bandwidths enables the distinction of vessels of differing size, allowing for detailed insights into vascular responses to vascular-targeted therapy. By using RSOM to examine the responses to vascular-targeted photodynamic therapy in mice with subcutaneous xenografts, we observed a significant and immediate occlusion of the tumour vessels, followed by haemorrhage within the tissue and the eventual collapse of the entire vasculature. By using dual-wavelength RSOM, which distinguishes oxyhaemoglobin from deoxyhaemoglobin, we observed an increase in oxygenation of the entire tumour volume immediately after the application of the therapy, and a second wave of oxygen reperfusion approximately 24 h thereafter. We also show that RSOM allows for the quantification of differences in neo-angiogenesis that predict treatment efficacy.

Tunable bandpass filter with wide tuning range of center frequency and bandwidth based on circular SIW

This paper presents a circular substrate integrated waveguide (SIW) bandpass filter (BPF) with wide tuning range of center frequency and bandwidth (BW). For designing such a filter, lumped varactors loaded at two metal posts are utilized to adjust the center frequency, and the bandwidth is tuned by varactors mounted between two SIW cavities. One transmission zero (TZ) can be located at the lower or upper stopband by controlling the mixed coupling between two resonators. The external coupling is changed by using two lumped varactors mounted between feedlines and resonators. Eventually, the BPF with tunable center frequency and bandwidth is designed, fabricated and measured. Measured results indicate the center frequency is tuned from 1.48 to 2.61 GHz (up to 55.3%) while maintaining a 3-dB absolute BW of 31 ± 2 MHz, and the 3-dB bandwidth is tuned from 29 to 250 MHz (up to 8.6). Insertion loss from 1.8 to 4.8 dB is observed within the wide tuning range.

Reconfigurable BPF With Constant Center Frequency and Wide Tuning Range of Bandwidth

A reconfigurable bandpass filter (BPF) with constant centre frequency and wide tuning range of bandwidth is presented. The proposed filter is based on the novel configuration of two modified asymmetrical $\pi $ -sections with folded shorted stubs loaded on a ring resonator. The novel topology allows the implementation of three reconfigurable passband states. A detailed theoretical analysis for calculating the transmission zeros using ABCD parameters is shown, and the design approach of implementing the random offset–x-, asymmetrical $\pi $ -sections with the folded stubs to get the bandwidth reconfigurability is thoroughly explained. PIN diodes are utilized as switching elements to achieve narrowband/mediumband/wideband response. The measured results indicate an absolute bandwidth tuning range of 1.3 GHz, whereas the −3 dB fractional bandwidth (FBW) can be varied from 37% to 92% while the centre frequency remains constant at 2.4 GHz. The fabricated prototype reconfigurable BPF demonstrates one of the widest 3-dB FBW tuning ranges and one of the highest absolute tuning ranges with a sharp-skirt characteristic. It has also more than 20 dB attenuation in the upper stopband which is extended to 2.7 times the centre frequency.

Current Measurement With 3-D Coreless TMR Sensor Array for Inclined Conductor

Magnetic sensor arrays have been widely used in current measurement, due to their advantages of small size, low power consumption, high sensitivity, wide bandwidth, and large dynamic range. However, they all assume that the conductor is perpendicular to the plane of the sensor array and the error introduced by un-perpendicularity has not been eliminated until now. In this paper, a 3-D tunnel magnetoresistance (TMR) sensor array scheme with its correction algorithm for eccentric, inclined current-carrying conductor is proposed. The simulation comparison of the relative error caused by the inclined angle between 1-D, 2-D, and 3-D TMR sensor arrays is performed, where the maximum errors are 25%, 20.5%, and 1.39%. It is obvious that the correction algorithm of 3-D TMR sensor array can significantly improve the accuracy. Four 3-D TMR sensors are used in the experimental prototype to verify the accuracy and reliability of the correction algorithm.

Generating the polarization-controllable THz radiations by incommensurate two-color femtosecond laser fields

We propose and demonstrate theoretically an effective way to generate polarization-controllable terahertz (THz) emission from the gaseous plasma. Compared to the previously used ω + 2ω two-color field, we show that the wavelength for the second pump laser pulse in the combination field, which is composed of a circularly polarized laser field and a linear laser pulse, is a key factor for controlling the polarization of emitted THz waves. By choosing an appropriate laser wavelength, intense linearly, elliptically, and circularly polarized THz radiation can be generated in a wide bandwidth range. Our simulations also show that for such an incommensurate two-color femtosecond laser field, its intensity ratio and phase delay between two components can also be used to control the polarization degree and direction of THz radiation. By utilizing the present laser technologies, our scheme can be implemented in the experiment.

Iterative smoothing filtering schemes by using clipping noise‐assisted signals for PAPR reduction in OFDM‐based carrier aggregation systems

Aggregating a lot of subcarriers will generate high peak-to-average power ratio (PAPR) which makes the overall system performance degradation. Among the existing PAPR reduction methods for orthogonal frequency-division multiplexing (OFDM)-based systems, iterative clipping and filtering (ICF) may be easy to implement, but ICF may cause signal distortion, so that the system cannot approximate the processed signals to the original signals which degrades error rates at receivers. Here, the authors proposed a new method based on ICF with smoothed clipping signals, and find the optimised filter to achieve the minimum error vector magnitude and efficiently reduce PAPR. Owing to the lack of a wide range of continuous bandwidth, the Third Generation Partnership Project proposed carrier aggregation (CA) technology in LTE-advanced systems. CA can aggregate many contiguous or non-contiguous fragment spectrums for supporting larger bandwidth and higher peak data rate. Here, the authors also evaluate the developed PAPR reduction scheme for the use in CA scenarios. The efficacy of the proposed scheme is demonstrated in the simulation results.

The application of the principle of wave superposition in ultrasonic measurement of lubricant film thickness

The principle of resonance is often applied in the ultrasonic measurement of the thickness of lubricant films. The information data relating to the thickness of the lubricant film involves the acquisition of the resonance frequency of a continuous wave with the application of a continuum model. However, ultrasonic signals are often times, generated by piezoelectric elements but these exhibit some variations from the continuous wave because they are dispersed pulses that have a wide range of frequency bandwidths. In this paper, the authors have applied the principle of wave superposition for the measurement of lubricant film thickness. This principle exhibits the capability to generate the resonant mechanisms of the pulse waves. The implemented theoretical analysis in this research work, depicted that the principle of wave superposition may demonstrate more applicability than the continuum model under the condition of the partial inclusion of the reflected pulse waves. The application of this principle facilitated the analysis of the resonant mechanisms of the pulse wave from the phase variations of the reflected echoes. It followed the further investigations into the influence of both the number of the reflected echoes and the materials of the solid layers on the film resonance method. The results of these investigations were validated using experimental results.

Filtering balanced-to-single-ended power dividing network

In this article, the filtering balanced-to-single-ended power dividing networks are proposed. Except the fundamental functions of differential-mode transmission, common-mode suppression, and out-of-phase single-ended output ports with isolation, the proposed designs show the advantages of wide controllable range of differential-mode bandwidth, multiple transmission zeros (TZs), and wide bandwidth for high out-of-band suppression. The frequencies of TZs, bandwidth, isolation, and common-mode suppression can be controlled by the parameters. For demonstration, three prototypes (Deigns I, II, and III) with two, four, or six TZs are implemented. The measured results show that design I (II and III) has an insertion loss of 0.38 dB (0.7 dB and 0.8 dB), an operating bandwidth of 12.5% (7.5% and 6.9%), and a bandwidth for 30-dB out-of-band suppression of 0.06f0 (0.09f0 and 0.14f0). The isolation and common-mode suppression inside the passbands of the three prototypes are all larger than 17 and 38 dB, respectively.

Broadband Plasmon Resonance Enhanced Third-Order Optical Nonlinearity in Refractory Titanium Nitride Nanostructures

Ultrafast control of light by light at the nanoscale may enable numerous long-awaited applications in nanophotonics. However, traditional plasmonic materials suffer from low optical thresholds that limit their usages. Titanium nitride has shown superior properties such as thermal stability, low cost, and a CMOS-compatible fabrication process. Even though titanium nitride is a prominent alternative plasmonic material, little is known about its optical nonlinearities and underlying mechanisms. Specifically, the third-order nonlinearity results in modifications of the refractive index, allowing all-optical modulation and switching functionalities. Here, we experimentally obtained the third-order optical susceptibility of the titanium nitride nanoparticles in an unprecedented wide bandwidth range and compared it to those of traditional materials. The experiments show a much broader nonlinear enhancement compared to gold and silver nanoparticles. This work demonstrates that titanium nitride is a valid alternat...

Experimental study of performance enhanced IM/DD transmissions based on constellation switching.

In this work, we experimentally investigate the performance improvement in IM/DD systems using constellation switching (CS), which is simple to implement with a reasonably low complexity. By encoding extra bits on the selection of a PAM constellation pattern from a set of constellations, a lower symbol rate can be used to achieve the same system bit rate compared with standard PAM systems based on a single constellation pattern. In our experiments with bandwidth limited components, including a 14 GHz bandwidth digital-to-analog converter (DAC), we demonstrate that the CS signals can improve the receiver sensitivity. In particular, in the 112 Gbit/s PAM4 case, the required receiver power was reduced by 0.8 dB and 1.1 dB using the CS at the HD FEC threshold of BER = 4 × 10-3 in the back-to-back (B2B) and 3 km fiber transmission, respectively. Similarly, in the 84 Gbit/s two-dimension (2D) PAM4 case, the required receiver power was reduced by 1.05 dB and 3.5 dB at the HD FEC threshold of BER = 4 × 10-3 in the back-to-back (B2B) and 5 km fiber transmission, respectively. Moreover, we show by simulations that the improved performance of using the CS signals is also observed over a wide range of transmitter bandwidth, further indicating the merits of using the CS in IM/DD PAM transmissions.

Near-infrared absorbers based on the heterostructures of two-dimensional materials.

Although the conductance and dielectric function of graphene can be tuned by applying external voltage, the tunability is less than 3%. Hybridizing graphene with other two-dimensional transition metal dichalcogenides (TMDs) can improve the adjustability and tunability of the optical properties of graphene-based structures at near-infrared frequencies. In this paper, we theoretically compute the dielectric function of graphene-MoTe2-graphene and graphene-MoTe2-graphene heterostructures utilizing the quantum electrostatic heterostructure (QEH) model, which is an ab-initio method. Utilizing the QEH results, we propose a hyper crystal (HC) absorber at near-infrared frequencies. Hence, we use the transfer matrix method to investigate our proposed absorber analytically. Moreover, we simulate the graphene-TMD-graphene (G-TMD-G) absorbers by the numerical finite difference time domain method. The results of the numerical solution are consistent with those of the analytical method. Due to the dependency of the Fermi level of graphene on the direct bandgap of the TMDs, the dielectric function of the G-TMD-G heterostructure can be tuned and enhanced further by changing the number of TMD layers. Finally, we demonstrate that the full absorption of the heterostructures can be achieved at different frequencies for transverse magnetic polarization. Since the thicknesses of the layers in the HC are lower than the wavelength of the light, no diffracted bands are ubiquitous, and the absorption can be observed for a wide range of incidence angles and bandwidths at near-infrared frequencies. Because of utilizing graphene-based HCs, in addition to the feasibility of design compared to the complex metasurfaces, the absorption bandwidth is significant for a wide range of incidence angles. This kind of HC absorber can be used in the design of sensitive optical devices, such as tunable filters, detectors, and photovoltaic applications.

Development and Performance Enhancement of MEMS Helix Antenna for THz Applications using 3D HFSS-based Efficient Electromagnetic Optimization

Interest of Micro-Electromechanical System (MEMS) antennas in Terahertz (THz) applications has rapidly expanded in recent years due to the advent of accurate Computer Aided Design (CAD) tools. The very special needs of newly proposed MEMS antennas, especially with a wide bandwidth range, require advanced optimization procedures of enhancing already established designs. This paper provides a compact design of a wideband MEMS helix antenna optimized using tree-dimensional High Frequency Structure Simulator (3D-HFSS) based on Quasi-Newton (Q-N) and Sequential Non Linear Programming (SNLP) techniques to modify the antenna structure with a high accuracy for the selective band of frequencies by training the samples and minimizing the error from Finite Element Method- (FEM) based simulation tool. The helix antenna is presented using MEMS technology and shows high performance demonstrated by very low return losses of less than -20 to -65 dB for a wide range of frequencies from 2.5 to 5 THz. High antenna geometry precision and efficient performance are finally achieved by rectifying and synthesizing various tunable parameters embedded in silicon substrate including both helix form and feeding line parameters.

Light Stops at Exceptional Points.

Almost twenty years ago, light was slowed down to less than 10^{-7} of its vacuum speed in a cloud of ultracold atoms of sodium. Upon a sudden turn-off of the coupling laser, a slow light pulse can be imprinted on cold atoms such that it can be read out and converted into a photon again. In this process, the light is stopped by absorbing it and storing its shape within the atomic ensemble. Alternatively, the light can be stopped at the band edge in photonic-crystal waveguides, where the group speed vanishes. Here, we extend the phenomenon of stopped light to the new field of parity-time (PT) symmetric systems. We show that zero group speed in PT symmetric optical waveguides can be achieved if the system is prepared at an exceptional point, where two optical modes coalesce. This effect can be tuned for optical pulses in a wide range of frequencies and bandwidths, as we demonstrate in a system of coupled waveguides with gain and loss.

Transient Response Characteristics of Linear Systems Subjected to Non-Gaussian Random Excitation with a Wide Range of Bandwidth

Transient Response Characteristics of Linear Systems Subjected to Non-Gaussian Random Excitation with a Wide Range of Bandwidth

Aggregation-Driven Controllable Plasmonic Transition of Silica-Coated Gold Nanoparticles with Temperature-Dependent Polymer-Nanoparticle Interactions for Potential Applications in Optoelectronic Devices.

Localized surface plasmon resonance (LSPR) effect relies on the shape, size, and dispersion state of metal nanoparticles and can potentially be employed in many applications such as chemical/biological sensor, optoelectronics, and photocatalyst. While complicated synthetic approaches changing shape and size of nanoparticles can control the intrinsic LSPR effect, here we show that controlling interparticle interactions with silica-coated gold nanoparticles (Au@SiO2 NPs) is a powerful approach, permitting wide range of optical bandwidth of gold nanoparticles with great stability. The interparticle interactions of Au@SiO2 NPs are controlled through concentration-, temperature-, and time-dependent polymer-induced interactions. The polymer-induced interactions modulate the state of particle dispersion, resulting an effective plasmonic shift by more than 200 nm. We further explore the microstructure of particle aggregation and explain mechanisms of plasmonic shift based on the results of small-angle X-ray scattering (SAXS) and discrete dipole approximation (DDA) calculation. We show that an effective control of LSPR behavior is now available through trapped aggregation of Au@SiO2 NPs with temperature variation. We anticipate that the suggested strategy can be employed in many practical applications such as optical bioimaging and optoelectronic devices.