dB BW Research Articles

All-Around Electromagnetic Wave Absorber Based on Ni-Zn Ferrite.

Exploring a convenient, scalable, yet effective broadband electromagnetic wave absorber (EMA) in the gigahertz (GHz) region is of high interest today to quench its expanding demand. Ni-Zn ferrite is considered as a potential EMA; however, their performance study as a scalable effective millimeter-length absorber is still limited. Herein, we investigated EM wave attenuation properties of Ni0.5Zn0.5Fe2O4 (NZF) samples substituting Mn ion in place of Fe3+ as well as Zn2+ within a widely used frequency range of 0.1-9 GHz. Through composition optimization, Ni0.5Zn0.4Mn0.1Fe2O4 (NZM0.1F) EMA demonstrates excellent microwave absorption performance accompanied by simultaneous maximum reflection loss (RL) of -50.2 dB and wide BW of 6.8 GHz (with RL < -10 dB, i.e., attenuation >90%) at an optimum thickness of 6 mm. Moreover, the attenuation constant significantly increases from ∼217 to 301 Np/m with Mn doping. The key contribution arises from magnetic-dielectric properties synergy along with enhanced dielectric and magnetic losses owing to cation chemistry and site occupation in spinel NZF. In addition, porosity is induced in the system by a controlled two-step heat treatment process that promotes total loss with multiple internal reflections of the EM wave. Furthermore, RL is simulated by varying incident EM wave angles for the NZM0.1F sample displaying its angle insensitivity up to 50°. Our results reveal NZM0.1F as a futuristic environment-friendly microwave absorber material that is suitable for practical high-frequency applications.

A U-band cascaded quadruplet quartz glass SIW filter based on double row vias coupling window

A U-band Substrate Integrated Waveguide (SIW) Cascaded Quadruplet (CQ) filter is designed based on low-cost quartz glass planar integrated circuits process with limited depth-to-diameter ratio and via spacing, which challenge the control accuracy of coupling coefficients. To address this issue, a double-row vias coupling structure control strategy is proposed to enhance the precision of coupling coefficient control. Cascaded quadruplet topology based on the proposed coupling structure with asymmetric coupling window is designed to improve the passband selectivity and harmonic suppression. The filter exhibits −3dB relative bandwidth of 4.6 % (1.94 GHz) at a central frequency of 42.2 GHz, insertion loss of 4.2 dB and rectangular coefficient (−20 dB BW/−3dB BW) of 1.47.

Li-Ion Cell in Operando Monitoring and Prognostication Using CMUT Devices

Capacitive micromachined ultrasonic transducer (CMUT) devices are ideal solutions for in operando battery monitoring applications especially for consumer electronics. Their minute size (2mm x 1mm x 0.5mm) allows direct placement on the battery without affecting the form factor of the device, the volume production techniques used for their manufacture allow for a very low-cost device, and they can be easily integrated with front-end integrated circuits either in a single device or in a discrete multichip form. Together with industry partners we have developed CMUT devices that we use to continuously monitor the behavior of a battery while it is cycling.For this work we used CMUTs (close-up shown in Fig. 1(a)) developed to operate with a low bias voltage (less than 30 V) which reduces the complexity of the driving hardware. The impulse response and its frequency content are shown in Fig. 1(b). In collapse mode, the peak frequency is 4.0 MHz and the one-way –3 dB BW is 76%, which allows flexibility in setting the drive conditions to interrogate the battery. Our testing also shows that the CMUTs show good device-to-device uniformity and they have a very stable performance in variable temperature environments (e.g. 0℃ - 60℃ ).The cell is interrogated in pulse-echo mode. The CMUT is excited by a wide-band unipolar pulse and the returned analog signal is filtered and amplified. The signal is then digitized and processed to extract features that allow us to quantify the state of the battery. Figure 1(c) depicts such signal features change under baseline cell cycling conditions (three cycles at a charge rate of C/4). These changes are the result of mechanical material property changes in the cell e.g., electrode stiffness and density [1] which directly affect the acoustic wave propagation inside the cell. Figure 1(d) depicts signal feature change due cell overcharge (red line). Ultrasound is especially sensitive to gas generation which occurs as the cell voltage extends beyond normal operating range [2]. Signal features provide early warning notice that cell is outside of normal operating conditions.Figure 1. a) Close-up image of CMUT device. b) CMUT impulse response and corresponding frequency content. c) Signal features (RMS and Time of Flight (ToF)) and thickness change during C/4 charge and discharge. d) Signal features during cell constant current overcharge. Cell overcharged after 4.4V (red line). Chang, W. et al. Measuring effective stiffness of Li-ion batteries via acoustic signal processing. Mater. Chem. A 8, 16624–16635 (2020).Appleberry, M. C. et al. Avoiding thermal runaway in lithium-ion batteries using ultrasound detection of early failure mechanisms. Journal of Power Sources 535, 231423 (2022). Figure 1

Design and performance evaluation of a novel metamaterial broadband THz filter for 6G applications

Terahertz (THz) radiation, which has applications in the imaging of objects, non-destructive testing, satellite communication, medical diagnostics, and biosensing, has generated a great deal of attention due to its remarkable properties. This paper proposes a novel broadband filter for THz applications. The main idea is to overcome the insertion loss and bandwidth issues by modeling a frequency-domain finite difference method and guided-mode resonance (GMR). The optimal design scheme of the wideband pass filter based on the circular resonant ring is discussed by comparing the transmission parameters under various parameters. This scheme overcomes the restriction of the narrow passband bandwidth of the prior THz filters and achieves approximately 3 dB bandwidth of 0.54 THz. The proposed THz filter paper also has the advantages of a straightforward structure, low processing costs, and ease of conformal with other structures, and it can be used for stealth fighters, new communication technology, and precise instruments. In addition, when compared to existing models, the suggested filter offers higher 3 dB BW operation, increased transmittance, low insertion loss, and stable performance at various oblique angles.

Vertical Architecture Solution-Processed Quantum Dot Photodetectors with Amorphous Selenium Hole Transport Layer

Colloidal quantum dots (CQDs) provide wide spectral tunability and high absorption coefficients owing to quantum confinement and large oscillator strengths, which along with solution processability, allow a facile, low-cost, and room-temperature deposition technique for the fabrication of photonic devices. However, many solution-processed CQD photodetector devices demonstrate low specific-detectivity and slow temporal response. To achieve improved photodetector characteristics, limiting carrier recombination and enhancing photogenerated carrier separation are crucial. In this study, we develop and present an alternate vertical-stack photodetector wherein we use a solution-processed quantum dot photoconversion layer coupled to an amorphous selenium (a-Se) wide-bandgap charge transport layer that is capable of exhibiting single-carrier hole impact ionization and is compatible with active-matrix readout circuitry. This a-Se chalcogenide transport layer enables the fabrication of high-performance and reliable solution-processed quantum dot photodetectors, with enhanced charge extraction capabilities, high specific detectivity (D* ∼ 0.5–5 × 1012 Jones), fast 3 dB electrical bandwidth (3 dB BW ∼ 22 MHz), low dark current density (JD ∼ 5–10 pA/cm2), low noise current (in ∼ 20–25 fW/Hz1/2), and high linear dynamic range (LDR ∼ 130–150 dB) across the measured visible electromagnetic spectrum (∼405–656 nm).

800 Gbit/s transmission over 1 km single-mode fiber using a four-channel silicon photonic transmitter

We demonstrate the optical transmission of an 800 Gbit/s ( 4 × 200 Gbit / s ) pulse amplitude modulation-4 (PAM-4) signal and a 480 Gbit/s ( 4 × 120 Gbit / s ) on–off-keying (OOK) signal by using a high-bandwidth (BW) silicon photonic (SiP) transmitter with the aid of digital signal processing (DSP). In this transmitter, a four-channel SiP modulator chip is co-packaged with a four-channel driver chip, with a measured 3 dB BW of 40 GHz. DSP is applied in both the transmitter and receiver sides for pre-/post-compensation and bit error rate (BER) calculation. Back-to-back (B2B) BERs of the PAM-4 signal and OOK signal are first measured for each channel of the transmitter with respect to a variety of data rates. Similar BER performance of four channels shows good uniformity of the transmitter between different channels. The BER penalty of the PAM-4 and OOK signals for 500 m and 1 km standard single-mode fiber (SSMF) transmission is then experimentally tested by using one channel of the transmitter. For a 200 Gbit/s PAM-4 signal, the BER is below the hard-decision forward error correction (HD-FEC) threshold for B2B and below the soft-decision FEC (SD-FEC) threshold after 1 km transmission. For a 120 Gbit/s OOK signal, the BER is below SD-FEC threshold for B2B. After 500 m and 1 km transmission, the data rate of the OOK signal shrinks to 119 Gbit/s and 118 Gbit/s with the SD-FEC threshold, respectively. Finally, the 800 Gbit/s PAM-4 signal with 1 km transmission is achieved with the BER of all four channels below the SD-FEC threshold.

A compact, highly stable spectral shearing interferometer to accurately reconstruct ultrafast laser fields

This paper presents a compact design for spectral shearing interferometry to reconstruct an ultrafast electric-field (SPIDER) with a high signal-to-noise ratio (SNR) and stability. Compared experimentally with the traditional SPIDER based on a Michelson interferometer (MI), this design can improve the SNR by a factor of 3.7 in a 25 dB BW region. Using the material dispersions of 6 mm BK7 plates as a target, the phase errors between the measured and theoretical values are less than 2.6 mrad, which is improved by a factor of ~4 from 10.3 mrad measured with the MI-based version. Even for a 1 mm fused silica plate, the measured phase errors are less than 2.1 mrad from the calculated values. Using this design for a 3-day test of our ultrashort pulse laser system, the variation in the output pulse width from the first to the third day is only 1.5%. We attribute this excellent performance to the common-path and all-transmission design of the test pulse pair, giving the design superior capacity against external disturbances. Our design can also work with the two-step phase-shift (TSPS) method to improve its measurement of the plulses with complex temporal/spectral structures.

Wideband bandstop filter using L-shaped and Quad mode resonator for C and X band application

ABSTRACTA wideband bandstop filter (BSF) with a very extensive stop band from 3.52 GHz to 12.38 GHz and a compact size of 7.4 mm × 15 mm (0.27λg × 0.54 λg) for C and X band applications is proposed in this letter. λg is the guided wave length of 50Ω transmission line at center frequency of 8 GHz. Proposed filter has −20 dB fractional bandwidth of 110% with roll-off factor (ratio of 3 dB BW to 20 dB BW) of 0.144. Harmonics suppression is below −20 dB is up to 2f0 (f0 is center frequency). Proposed filter consists of two types of resonator, one Quad mode resonator and other L-shaped resonator. Transmission zero frequency is verified with the help of scattering parameters and transmission line model. The simulated and measured results are in total concurrence with each other.

Performance Investigation of FinFET-Based MO-CCII and its Applications: Resistor-Less Multi-Function Bi-Quadratic Filter and Balanced Modulator

This paper presents an optimal design of a high-performance multi-output second-generation current conveyor (MO-CCII) based on 20[Formula: see text]nm Fin-Shaped Field Effect Transistor (FinFETs). Proposed MO-CCII has very low port X impedance and very high port Y impedance. The performance of the CCII has been thoroughly investigated in terms of DC, AC and transient characteristics of terminal voltages and branch currents and frequency response of port impedances. CCII shows the excellent high-frequency response of voltage as well as current transfer gains. The 3[Formula: see text]dB BW of voltage and current transfer gains are 11.2[Formula: see text]GHz and 11[Formula: see text]GHz, respectively. CCII provides excellent performance over its CMOS counterpart. Also, a resistor-less multi-function bi-quadratic filter is proposed. The filter depends on two CCIIs, a capacitor and does not require any resistors. It has three inputs and one output and realizes low-pass, high-pass and band-pass filters from a similar setup. FinFETs in the linear region are utilized as variable resistor to control filter properties. Nevertheless, the proposed filter has two floating capacitors which can be effortlessly realized in these days’ integrated circuit advancements. Also, a balanced modulator is proposed utilizing the proposed FinFET-based CCII and FinFET transistors only. Balanced modulator’s frequency of operation obtained is in GHz range.

Optical Fiber Amplifiers: Optimization and PerformanceEvaluation

This work demonstrates the simulation of two different types of optical fiber amplifiers (OFA) utilizing OptiSystem–10, namely, 3 m length of erbium doped fiber amplifier (EDFA) and 7 km length of Raman fiber amplifier (RFA). The counter-pumped architecture is adopted for both proposed optical amplifiers. The optimum pump power (OPP) for each amplifier determines in which the longest 3–dB flat gain bandwidth (3–dB BW), reasonable average gain level (Gav), proper average noise figure (NFav) and lower gain variation (Gvar) were achieved. The EDFA shows best performance at conventional band (C–band) within the pump power of 30 mW.While the better performance is observed at long band (L–band) within the pump power of 600 mW for the RFA.

A Two Concentric Slot Loop Based Connected Array MIMO Antenna System for 4G/5G Terminals

In this paper, an integrated design with a multiple-input multiple-output (MIMO) antenna system for fourth generation (4G) and fifth generation (5G) applications is presented. The proposed design contains a two-element slot-based MIMO antenna system for 4G and a connected antenna array (CAA)-based two-element MIMO antenna system for a potential 5G band. Two rectangular loops are etched on the periphery of the ground plane. The top and bottom portions of the thin loops act as the two 4G MIMO antennas, while parts of their sides are acting as 5G arrays. The antenna system is fabricated on a commercially available Roger 4350 substrate with $\epsilon _{r}$ equal to 3.5, while the dimensions of the board are $100\times 60 \times 0.76$ mm3 representing a typical smart phone back plane size. The integrated antenna system covers multibands at 4G with a combined bandwidth of 1.565 GHz (−6 dB BW) in addition to the band between 16.50 and 17.80 GHz for 5G. The design is planar, low profile, simple, and compact in structure making suitable for wireless handheld devices and mobile terminals. The measured gain at 3.46 GHz was at least 2.22 dBi and at 17 GHz was 8 dBi for the 4G and 5G MIMO antenna systems, respectively. The envelope correlation coefficient was also calculated from the measured 3-D patterns and showed good MIMO performance. This is the first integrated 4G/5G MIMO antenna system with below 6 GHz and above 10-GHz covered bands using CAA.

A Half-mode Substrate-Integrated Filter With Tunable Center Frequency and Reconfigurable Bandwidth

This letter presents a half-mode substrate integrated cavity bandpass filter with both continuous center frequency and 3 dB bandwidth tuning capabilities. The filter adopts a superposed two layers PCB with lumped varactors loading the central resonator to tune the center frequency. The first-invented semicircular metal sheet on the center rod not only reduces the filter size given a certain resonant frequency significantly by increasing the capacitance between the semicircular metal and the upper ground metal but also facilitates fine frequency tuning by using appropriate varactor $C_{\mathrm{tune}}$ . Surface mount varactors between two resonators change the inter-resonator coupling to adjust the 3 dB BW. Another varactor on the feed line can be used to adjust the external coupling. This filter demonstrates a BW range of 75–130 MHz around 1.5 GHz, a 3 dB BW range of 46–130 MHz around 1.3 GHz and a 3 dB BW range of 55–90 MHz around 1.11 GHz with 10 dB minimum return loss. Insertion loss ranging from 2.262 dB to 7 dB have been obtained.

Passive Front End for LTE TDD Transceiver

In this paper, a passive front end for a 3GPP Long Term Evolution (LTE) TDD transceiver comprising a microstrip antenna and filter is presented. The proposed antenna and filter operates in the LTE band 36 (TDD) which extends from 1930MHz to 1990MHz. A patch antenna and Hairpin filter is fabricated with a total area of 43x36mm for the antenna and 38.6x32.16mm for the filter. The proposed devices are fabricated using FR-4 material substrate and the measuring results show good agreement with the simulation results. The fabricated antenna has 2.67dBi directivity, 1.242dB gain, a minimum return loss of -31.85dB at resonant frequency 1950MHz and 150.3 MHz bandwidth at 6dB return loss, while the filter has -3dB BW of 90MHZ, a center frequency of 1950MHz and a fractional bandwidth of 4.615%.

A W-band CMOS Receiver Chipset for Millimeter-Wave Radiometer Systems

This paper presents a W-band receiver chipset for passive millimeter-wave imaging in a 65 nm standard CMOS technology. The system comprises a direct-conversion receiver front-end with injection-locked tripler and a companion analog back-end for Dicke radiometer. The receiver design addresses the high 1/f noise issue in the advanced CMOS technology. An LO generation scheme using a frequency tripler is proposed to lower the PLL frequency, making it suitable for use in multi-pixel systems. In addition, the noise performance of the receiver is further improved by optimum biasing of transistors of the detector in moderate inversion region to achieve the highest responsivity and lowest NEP. The front-end chipset exhibits a measured peak gain of 35 dB, -3 dB BW of 12 GHz, NF of 8.9 dB, while consuming 94 mW. The baseband chipset has a measured peak responsivity (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</sub> ) of 6 KV/W and a noise equivalent power (NEP) of 8.54 pW/Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> . The two chipsets integrated on-board achieve a total responsivity of 16 MV/W and a calculated Dicke NETD of 1K with a 30 ms integration time.

Demonstration of a Tunable Microwave-Photonic Notch Filter Using Low-Loss Silicon Ring Resonators

We present a fully tunable multistage narrowband optical pole-zero notch filter that is fabricated in a silicon complementary metal oxide semiconductor (CMOS) foundry. The filter allows for the reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously. It is constructed using a Mach-Zehnder interferometer (MZI) with cascaded tunable all-pass filter (APF) ring resonators in its arms. Measured filter nulling response exhibits ultranarrow notch 3 dB BW of 0.6350 GHz, and nulling depth of 33 dB. This filter is compact and integrated in an area of 1.75 mm2. Using this device, a novel method to cancel undesired bands of 3 dB bandwidth of < 910 MHz in microwave-photonic systems is demonstrated. The ultranarrow filter response properties have been realized based on our developed low-propagation loss silicon channel waveguide and tunable ring-resonator designs. Experimentally, they yielded a loss of 0.25 dB/cm and 0.18 dB/round trip, respectively.

AN INDUCTIVE SELF-COMPLEMENTARY HILBERT-CURVE ANTENN FOR UHF RFID BROADBAND AND CIRCULAR POLARIZATION TAGS

A novel fractal tag antenna constructed with Hilbertcurve and self-complementary configuration is proposed for UHF RFID applications. The main aim of this paper is to merge the meander line and meandered-slot structure of the RFID tag antenna in order to obtain a good performance of compact, broadband, circular polarization and conjugate impedance matching. The tunable inductive and broadband (−10 dB BW = 115 MHz) characteristics Corresponding author: J. C. Liu (jichyun@cyu.edu.tw).

CMOS CCII– based on modified dual output-OTA for high frequency applications

A negative CMOS second generation current conveyor (CMOS CCII–) based on modified dual output CMOS folded cascode operational transconductance amplifier (CMOS DO-OTA) is presented. The proposed folded cascode CMOS DO-OTA with attractive features for high frequency operation such as high output impedance, wide bandwidth, high slew rate, with low power consumption is used in the realisation. The proposed CMOS DO-OTA and CMOS CCII– with high performance parameters can be used in many high frequency applications. The proposed CMOS CCII– achieves 1.37 GHz (−3 dB BW), 1.8 ns settling time, 48 V/μs slew rate, and low power consumption around 3.25 mW for ±2.5 V supply. P-Spice simulation results are included for 0.5 μm MIETEC CMOS technology.

A monolithic (Si) massively broadband non-reverberant monopole

A novel monolithic implementation of a Wu–King profiled antenna intended for use in critical time-domain/UWB/imaging applications is presented. The simulated device was fabricated on a high-resistivity Si substrate on top of which a layer of GaAs is grown, segmented and patterned to serve as the radiating element. The device's measured return loss indicates a −10 dB BW > 50 GHz and time-domain measurements using a 500 pS input pulse prove that the device is practically non-reverberant in air.

Improved scatterer size estimation from ultrasound backscatter using coded excitation and pulse compression

Scatterer size estimation from ultrasound backscatter has been used to improve the detection and classification of cancer. Estimates of scatterer size from tissues come from ultrasound backscattered signals that often have low signal-to-noise ratio (SNR). Coded excitation was explored as a means to increase the SNR of signals used in scatterer size estimation. The normalized backscatter coefficient was measured from tissue mimicking phantoms containing glass beads. The diameters of the glass beads were estimated by fitting the normalized backscatter coefficient to models for scattering from spheres [J. Acoust. Soc. Am. 23, 405–418 (1951)]. Two weakly-focused, single-element transducers (f0=5 MHz, −6 dB BW=4.2 MHz, f/3, and f0=10 MHz, −6 dB BW=9.1 MHz, f/4) were used in the measurements. For coded excitation, a linear FM chirp with a time bandwidth product of 40 was used. Three phantoms with average glass bead diameters of 30, 45, and 82 μm were scanned. Preliminary results indicated that estimate bias was reduced versus penetration depth for the coded excitation compared to conventional pulsing. In addition, estimate variance using the coded excitation technique was reduced because the SNR was increased. [Work supported by start-up funds from the University of Illinois at Urbana-Champaign.]