Narrow Results

This paper presented a multiplier-less memcapacitor emulator circuit that is implemented without using a memristor mutator. The proposed circuit is a charge-controlled memcapacitor built with analog blocks. Comparatively, this circuit uses fewer active–passive elements, where all passive elements are grounded. In addition, the most advantageous feature is its tuning which can be done externally by electronic means. Also, the proposed circuit layout has been drawn with minimum metal routing, optimum floor planning, and DRC and LVS checks. The circuit behavior is justified through various simulations in the Cadence Virtuoso-Spectre tool with 180-nm CMOS parameters, and the operating frequency of the proposed circuit is up to 4KHz. In addition, theoretical and simulated results are proven through experimental verification using off-the-shelf IC.

Low-frequency and broadband are the critical challenges in real-life applications. Here, we try to tackle the challenges by proposing a reconfigurable acoustic metasurface (AM) composed of the membrane-type metamaterial (MAM) structure of deep sub-wavelength scale. By employing the external air pumping system into each individual unit cell of the AM, the tension of the membrane can be readily tailored by the system with little interference from other unit cells. Two strategies of the constant pressure method (CPM) and constant volume method (CVM) are reported to design the MAM. And the CVM is adopted as the ultimate design strategy by comparing both methods from aspects of the dimension, operating frequency, and structure complexity. In order to validate the low-frequency and broadband performances of the AM, the Airy-like beams and the acoustic converging based on two identical Airy-like beams are introduced and proof-of-concept simulations are performed with the finite element method. The simulated results agree well with the theoretical predictions. Our design provides the little-interference active design method for the low-frequency and broadband AM to manipulate the wave front, and may have practical engineering applications in areas of the aerospace, high-speed train, marine vessel, and power transmission and transformation project.

Narrow bandwidth and specific incident angle are the main drawbacks in real-life applications for the existed carpet cloaking based on the acoustic metasurface (AM). Here, we tackle to get over the problems by proposing a reprogrammable AM. The unit cell is composed of water sink and filling nozzle. By incorporating an external water pumping system into each individual unit cell, the reflected phase can be readily regulated. Since the pumping process is reversible, the AM is reprogrammable under the control of the water pumping system in the frequency range of 3430–6860Hz. Both the acoustic cloaking and disguising are designed based on the proposed AM. The double security for the target object can be ensured to avoid being detected by combining the two designs. Simulated results with the finite element method indicate that the acoustic cloaking and disguising can work in the broad bandwidth of 66.7% of the central frequency with full-range incident angles from $-90^{\circ }$ to $90^{\circ }$. Our design shows promise for applications in realizing the practical skin cloaking and disguising one step closer.

We propose a single-wavelength-tunable and dual-wavelength-switchable Tm-doped fiber soliton laser with single-walled carbon nanotubes. The laser can deliver single-wavelength mode-locked pulse tunable from 1892 nm to 1924 nm. Dual-wavelength mode-locking operation can also be achieved by increasing pump power and rotating the polarization controller (PC), meanwhile the wavelength can be switched between 1883/1894 nm and 1905/1910 nm. Both the tunable and switchable operations are realized with great ease by solely adjusting the parameters of PC. The proposed Tm-doped fiber laser can operate in two mode-locking states, which is helpful for further understanding of the mode-locking mechanism and useful for practical applications.

Metamaterials (MMs) represent a group of exciting artificial materials that interact with electromagnetic waves in unnatural ways. The motivation behind MM research arises not only from fundamental interest in their unique physical properties but also from the desire of creating smarter materials for advanced technological applications. Despite an abundance of studies on numerous shapes, sizes and operating frequencies, the use of conventional metal-dielectric components makes the post-fabrication physical properties of MMs unalterable. Therefore, the integration of other nonlinear materials is necessary for exploring the functional limits of MMs. In this regard, a mono-layer of carbon, the so-called graphene, with its unique electrical conductivity is identified as a promising candidate. This review discusses the recent progress on tunable graphene-based THz MMs for perfect absorption and electromagnetically-induced transparency effects. A short overview of prospect challenges and tendencies is also given for future development of graphene-integrated MMs towards upcoming smart meta-devices.

Different from the traditional tunable Smith–Purcell (SP) radiation in the graphene-based gratings in the terahertz band, we propose a tunable SP radiation generated from an electron beam passing through a single-layer molybdenum disulfide (MoS₂) based grating in the visible band. The comparison between the simulation and the theoretical results shows good agreement. By varying the Fermi energy of MoS₂ from 0.025 eV to 0.125 eV for the MoS₂-based grating, we can not only control the radiation frequency but also can change the radiation magnitude. The radiation frequency, angle, and magnitude varying with the Fermi energy are also discussed, respectively. These properties would have potential applications in developing tunable visible SP radiation.

In this paper, we introduce an implementation of a CCII-based grounded inductance operating in class AB. In order to get tunable characteristics of the design, a translinear CCII configuration is used as a basic block for its high level of controllability. A frequency characterization of the translinear CCII is done. In order to optimize its static and dynamic characteristics, an algorithmic driven methodology is developed ending to the optimal transistor geometries. The optimized CCII has a current bandwidth of 1.28 GHz and a voltage bandwidth of 5.48 GHz. It is applied in the simulated inductance design. We first consider the conventional topology of the grounded inductance based on the generalized impedance converter principle. Making use of the controllable series parasitic resistance at port X in translinear CCII, we design tunable characteristics of the inductance. The effect of current conveyor's nonidealities has been taken into account. A compensation strategy has been presented. It is based on the insertion of a high active CCII-based negative resistance and a very low passive resistance. The compensation strategy does not affect the inductance tuning process. Simulation results show that the proposed inductance can be tuned in the range [0.025 μH; 15.4 μH]. The simulated inductance has been applied in a fully integrated tunable high frequency band pass filter to illustrate the versatility of the circuit. The filter is electrically tunable by controlling the conveyor's bias current.

In this paper, a new active element namely Dual-X current conveyor differential input transconductance amplifier (DXCCDITA) is proposed. The DXCCDITA is utilized in designing four minimum component fully cascadable all pass filter (APF) structures. The designed all pass filters require only single active element and one/two passive elements for realization thus making them a minimum component implementation. Two among the four presented all pass structures require only a single capacitor for implementation. A scheme for realizing nth order all pass filter is also suggested and a fourth order voltage mode (VM) filter is developed from the proposed scheme. The effect of non-idealities on the proposed all pass filters is also studied. A simple oscillator is also developed using one of the all pass filter structure. The oscillator required only one DXCCDITA, two capacitors and one resistor for implementation. The DXCCDITA is implemented in 0.35$\mu$m TSMC CMOS technology parameters and tested in Tanner EDA. Sufficient numbers of simulations are provided to establish the functionality of all pass structures. The experimental results using commercially available integrated circuits (ICs) are also provided.

In this paper, a new multiple-gated transistor (MGTR) linearization technique is presented. To simultaneously keep linearity and tuning capability of proposed operational transconductance amplifier (OTA), the auxiliary transistors which are employed for $g_{m3}$ cancellation of differential pair (DP) stage are body-driven through a tune-dependent voltage. By this way, the third-order nonlinearity of DP is reduced for a wide range of transconductance values from 5.1 to 35.6$\mu$A/V. The OTA works with 1.2V supply voltage and its power consumption changes between 137.4 and 156$\mu$W at the entire tuning range. For $G_m=17.6$$\mu$A/V ($V_{\mathrm{\text{tune}}}=0.6$V) and for 0.6$Vpp$ input voltage, the simulation results show 6dB reduction in the total harmonic distortion (THD) of proposed OTA when the MGTR linearization technique is used and 15dB reduction when the tune-dependent body driving is also utilized. The proposed OTA is employed in a third-order low-pass Butterworth filter which is tunable from 2 to 18MHz. The in-band IIP3 of filter is 16.9 and 12.4dBm, respectively, for 2 and 18MHz cutoff frequencies while the two-tone input voltage is applied at 1MHz.

Traditional filters usually have low Q and gain values and it is difficult to adjust their center frequencies. Moreover, it is very complicated to analyze their transmission charateristics through conventional methods. Therefore, in this paper, a tunable differential N-path bandpass filter that uses a new adjoint network method to analyze the transmission characteristics of the differential N-path structure is proposed. The filter circuit adopts a novel circuit structure consisting of two differential N-path structures, two transconductance amplifiers and an off-chip transformer. The differential structure eliminates even harmonics, the transconductance amplifier increases the circuit gain and the off-chip transformer acts as a balun, improving the filter’s Q value and achieving impedance matching. Unlike the traditional switching capacitance method used for analyzing the differential circuit structure, the method proposed in this paper does not involve complicated calculus operations. In fact, the method greatly simplifies these complex operations, and the transmission function of the circuit can be obtained through simple algebraic operations. The proposed filter was designed using TSMC 180nm CMOS process. Simulation results for a differential four-path bandpass filter formed under 1.2V supply voltage show that the gain of the filter is greater than 8.5 dB, the center frequency can be adjusted from 0.1GHz to 1GHz, the in-band insertion loss S11 is greater than 10 dB, the out-of-band IIP3 is greater than 10 dBm, the out-of-band rejection is 28 dB and the noise figure is less than 2.2 dB at $f_s=300$MHz.

A gain and bandwidth tunable active-RC multiple-feedback (MFB) fourth-order low-pass filter is presented, which exhibits four different bandwidths of 10, 20, 30 and 40MHz and four different gain settings of 0, 4, 8 and 12dB to meet the requirements of the cellular vehicle-to-everything (C-V2X) standards. The filter uses the cascade of two biquad MFB cells. Gain and bandwidth programmability is achieved by using programmable capacitor and resistor arrays. A logic block is implemented in the filter to adjust the gain transfer function for every tuning option. Also, two-stage miller op-amp topology is chosen to implement biquad MFB cells for minimum complexity and maximum efficiency in low voltage operation. The filter is designed in 65-nm CMOS technology and occupies a 0.181mm² area and it totally consumes 13.41mW from the 1.2V supply voltage. To the best of the author’s knowledge, this work is the first CMOS baseband filter design that includes both gain and bandwidth programmability implemented for C-V2X applications.

We present a review of recent progress in the studies of the nonlinear- and electro-optics of liquid crystals, particularly in their meta-material forms. An analytical expression for the "ultimate" optical nonlinearity of nematic liquid crystals is obtained, and several routes to realizing such optical nonlinearities are discussed. We also describe two approaches for realizing tunable or reconfigurable negative-zero-positive index materials: (1) planar nano-structured frequency selective surfaces [FSS] containing nematic liquid crystals; (2) core-shell nano-spheres randomly distributed in bulk nematic liquid crystal matrix. Such metamaterials can be designed for applications in the visible-infrared, as well as Terahertz and microwave regimes. These liquid crystalline meta-materials are capable of supra-nonlinearities characterized by refractive index changing coefficients of over 1 cm²/watt and microseconds response times.

A novel tunable acceleration-thresholds switch device based on electrostatic force in controlling friction for desired acceleration-thresholds level is developed. Electrostatic forces based on desired friction are used to provide variable acceleration threshold level. The design concept is based on the fact that when acceleration is presented on the proofmass, an induced static friction will exactly cancel the effect of the acceleration. Upon the acceleration level is exceeding the maximum static friction, the proofmass engages movement in the acceleration direction and enter dynamic friction region. A contact pad is designed here to detect the on/off status of the accelerating proofmass. Dynamic simulation model, established by Matlab Simulink solver, indicated that the input signal is given with 10 triangular waves from 0.5g to 5g peak accelerations in 0.1sec duration, and the threshold switch gap is designed in 1 m. When V_C, are equal to 1V, 1.5V, and 1.8V respectively, there are 8 signals (from 1.5g to 5g), 5 signals (from 3g to 5g), and 3 signals (from 4g to 5g) exceeded 1 m threshold switch gap which demonstrated the effectiveness of the present design concept. Experimental results of the tunable acceleration-thresholds switch device will be reported in the near future.

Multiferroic materials and devices have attracted intensified recent interests due to the demonstrated strong magnetoelectric (ME) coupling in new multiferroic materials and devices with unique functionalities and superior performance characteristics. Strong ME coupling has been demonstrated in a variety of multiferroic heterostructures, including bulk magnetic on ferro/piezoelectric multiferroic heterostructures, magnetic film on ferro/piezoelectric slab multiferroic heterostructures, thin film multiferroic heterostructures, etc. Different multiferroic devices have been demonstrated, which include magnetic sensors, energy harvesters, and voltage tunable multiferroic RF/microwave devices which are compact, lightweight, and power efficient. In this progress report, we cover the most recent progress on multiferroic heterostructures and devices with a focus on voltage tunable multiferroic heterostructures and devices with strong converse ME coupling. Recent progress on magnetic-field tunable RF/microwave devices are also covered, including novel non-reciprocal tunable bandpass filters with ultra wideband isolation, compact, low loss and high power handling phase shifters, etc. These novel tunable multiferroic heterostructures and devices and tunable magnetic devices provide great opportunities for next generation reconfigurable RF/microwave communication systems and radars, Spintronics, magnetic field sensing, etc.

The authors have demonstrated a dual-pumped tunable Raman fiber laser. Tuning of the laser is done by adjusting a tunable bandpass filter that yields a range of about 45 nm from 1520 to 1565 nm and with peak power output of over 11 mW. Two 1.2 W fiber lasers at 1455 and 1480 nm pump the laser.