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In the mm-wave frequency band, the rectifier’s sensitivity is the bottleneck of a wireless-powered IoT transponder’s distance. At a meter’s distance, the received power is weak, and transistors in a front end of a wireless power receiver operate in the weak inversion region. This article presents a mathematical analysis of the mm-wave multi-stage rectifier in the low-power region. A design methodology of a 57–64-GHz fully integrated eight-stage rectifier with a bulk-drain connection in 40-nm CMOS technology is presented. Parasitic effects on a multi-stage rectifier are analyzed. Based on the analysis, an intrinsic threshold voltage modulation is applied to improve the sensitivity. A tree-type power splitter is also proposed for the RF power signal’s phase balance. With this method, the RF signal arrives at each stage with an equal phase, and its suppression at the output is improved by 16 dB. This mm-wave rectifier achieves −7.1-dBm input sensitivity at 57 GHz with 1-V dc output voltage. The overall sensitivity from 57 to 64 GHz is better than −4.5 dBm. Compared to other mm-wave silicon-based rectifier state of the arts, the proposed mm-wave rectifier achieves better sensitivity while maintaining a compact size. [ABSTRACT FROM AUTHOR]

The research on bidirectional human-machine interface (BHMI) is of great significance, which can realize the interaction between human and machine. As the traditional Human-Machine Interface (HMI) device is limited by its wired connection and unidirectional functionality, this paper intends to develop a wireless wearable solution for BHMI with gesture recognition and vibration feedback. Compact design and wireless connection improve the flexibility and wearability of bidirectional interface node (BIN). By establishing a Distributed Wireless Sensor Network (DWSN), the proposed system allows up to 8 BINs to detect muscle activities simultaneously and control each Linear Resonant Actuator (LRA) independently. The data transmission throughput of the proposed system can be reduced by transmitting signal features instead of raw signals. With a sample rate of 2000 Hz and a resolution of 12 bits, BIN can achieve 94.48%±4.56% classification accuracy of six gestures. To evaluate the performance of the system’s bidirectional functionality, virtual control experiment was carried out. The experimental results show that the completion rate of the virtual control experiment reached 87% within 3.5s with vibration feedback. Overall, the outcomes of this study have great potential to promote the practical applications of bidirectional human-machine interaction, including rehabilitation therapy, fatigue prevention, virtual reality/augmented reality (VR/AR), and sensorimotor control of artificial devices. [ABSTRACT FROM AUTHOR]

This brief presents a resistor-based CMOS temperature sensor with a duty-cycle-modulated output. A dynamic-biased resistive analog front-end (AFE) is proposed to generate voltages with positive and negative temperature dependencies. The voltages are then converted into a digital-friendly duty-cycle-modulated output, which can be proceeded by digital systems directly. Fabricated in a standard 0.13- $\mu \text{m}$ CMOS process, this sensor occupies a silicon area of 0.025 mm2 and can operate with a supply voltage as low as 0.8 V. It has a measured inaccuracy of ±0.85 °C ($3\sigma $) from −40 °C to 85 °C after a two-point calibration. Measured at room temperature, it shows a resolution of 0.226 °C in a 0.25-ms conversion time while dissipating 12.5 $\mu \text{W}$. [ABSTRACT FROM AUTHOR]

The “magnetic window” is considered to be an effective technique for alleviating a vehicle’s atmospheric reentry blackout, whereas the dynamic variation characteristic of the plasma sheath is critical for the vehicle’s communication. In this article, the effects of dynamic plasma sheath on electromagnetic wave propagation and the bit error rate (BER) of two typical modulation signals under an external magnetic field are investigated. First, the hybrid matrix method is used to calculate the transmission coefficients of right-handed circularly polarized (RHCP) waves with different magnetic fields and plasma electron density fluctuation. Then, the average BER of two typical modulations signals, namely M-ary phase-shift keying (MPSK) and noncoherent M-ary frequency shift keying modulation (NC-MFSK) is numerically simulated based on the magnetized plasma sheath channel response. The results show that the magnitude in dB scale and phase of the RHCP transmission coefficient follow Gaussian distribution when the probability density function of the electron density is a Gaussian distribution. The BER performance of binary phase-shift keying (BPSK) and NC-MFSK is relevant to the incident wave frequency, the plasma stopband, and the intensity of electron density variation. Owing to the insensitivity of phase jitter, the NC-8FSK has a better performance than BPSK, followed by NC-4FSK and NC-2FSK. [ABSTRACT FROM AUTHOR]

This article presents a leakage-based digital temperature sensor with reduced supply sensitivity for on-chip thermal management. The sensor, featured with a novel supply sensitivity suppression mechanism, performs the temperature-to-frequency conversion by a leakage-dominated ring oscillator (LDRO) with exponential temperature dependence. Thanks to the proposed robust and reconfigurable Schmitt-trigger-based delay cell, both NMOS and PMOS leakage-based sensors can be evaluated in a single design. Fabricated in a standard 55-nm CMOS digital process, the proposed digital temperature sensor occupies a silicon area of only 1770 $\mu \text{m}^{2}$ and can operate under a supply ranging from 0.8 to 1.3 V, with the supply sensitivities of 2.53–5.22 °C/V and 2.84–5.76 °C/V in two working modes at room temperature, respectively. Measurement results show that the sensor achieves an inaccuracy of ±0.70 °C (3 $\sigma $) from −40 °C to 125 °C after two-point calibration. [ABSTRACT FROM AUTHOR]

In this brief, an analytical model for the reliability-oriented design of injection-locked frequency divider (ILFD) is proposed. It is able to provide a clear evaluation of startup condition in the ring oscillator (RO)-based ILFD, which has not been clearly defined with the conventional zero-pole theory. A new startup condition analysis is presented and applied in designing an ILFD to achieve a reasonable compromise between a robust startup condition and a wide locking range. To verify this theory, a prototype is fabricated using a standard 0.18- ${\mu \text {m}}$ CMOS process, maintaining a reliable startup over potential variations of manufacturing or working conditions. The experimental results at industrial temperature ranges under different supply voltages suggest that the proposed divider is able to work robustly from 0.19 to 1.24 GHz with a maximum power consumption of 0.246 mW from a 1.2-V supply, while occupying a silicon area less than $20\times 30\,\,{\mu \text {m}^{2}}$. [ABSTRACT FROM AUTHOR]

This brief presents a bipolar junction transistor (BJT)-based CMOS temperature sensor without trimming. A current-mode readout scheme with dynamic current gain compensation is proposed to reduce the error caused by the low current gain $\beta $ of the substrate BJT in nanometer CMOS technologies. Combining this readout scheme with techniques, such as chopping and dynamic element matching (DEM), the sensor achieves a high untrimmed accuracy for auto-calibration in thermal management applications. Fabricated in a standard digital 55-nm CMOS process, the sensor shows a measured inaccuracy within ±1.7 °C ($3\sigma $) from −40 °C to 125 °C without calibration. It occupies a die area of 0.0146 mm2 and has a power consumption of $37~\rm \mu \text{W}$ with an adjustable resolution from 12 to 15 bit and a conversion time of 4.1–32.8 ms. [ABSTRACT FROM AUTHOR]

In this paper, a 3-D stochastic finite-difference time-domain algorithm is developed for simulating wave propagation in isotropic cold plasma medium by using the bilinear transform (BT) technique. The proposed algorithm has a simple formulation and is very easy to apply to isotropic dispersive material. It efficiently calculates the mean value and standard deviation of electromagnetic field components caused by the variability or uncertainty of the plasma’s electron density and collision frequency. The stretched coordinate perfectly matched layer (SC-PML) with a complex-frequency-shifted factor is implemented as the absorbing boundary condition, and the BT technique is also incorporated into the SC-PML. Numerical examples are shown to demonstrate the accuracy and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

An efficient stochastic finite-difference time-domain (S-FDTD) with weighted Laguerre polynomials algorithm is presented for calculating the standard deviation of the electromagnetic fields caused by the variability or uncertainty of the isotropic cold plasma materials in a single run. Compared with the conventional S-FDTD method, the proposed algorithm uses an implicit marching-on-in-degree scheme, which improves the computational speed significantly. The perfectly matched layer with complex-frequency-shifted factor is implemented via formulation in the stretched-coordinate system. Numerical examples demonstrate the accuracy and effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

A stochastic finite-difference time domain (S-FDTD) combined with the piecewise linear recursive convolution method is applied to model wave propagation in unmagnetized plasma with random plasma frequency. The stretched-coordinate perfectly matched layer implementation of the S-FDTD method is also presented. The accuracy and efficiency of the proposed algorithm are validated by numerical examples. [ABSTRACT FROM AUTHOR]

We previously developed a tri-diagonalized finite-difference time-domain (FDTD) algorithm based on the weighted Laguerre polynomials (WLPs) for modeling wave propagation in magnetized plasma. The algorithm demonstrated dramatic CPU time reduction in comparison with the original WLP-FDTD algorithm. However, a splitting error was caused owing to the additional perturbation term. In this paper, an iterative scheme is introduced to the tri-diagonalized WLP-FDTD algorithm to further reduce the splitting error. Numerical example shows the accuracy and effectiveness of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

Localization of light is usually achieved by external mechanisms, such as metallic reflection, photonic bandgap, and total internal reflections. Here, we propose a new concept about localization of electromagnetic waves, named self-trapped state. We design an ordinary photonic crystal waveguide with two array rods made of magneto-optical media on its two sides. The waveguide modes form a self-trapped band in which electromagnetic waves are trapped. The trapping does not rely on the external mechanisms; instead, it comes from band’s own properties. Based on the self-trapped band, the virtual reflection walls and semi-opening cavity can be achieved. The semi-opening cavity has some unique advantages compared with ordinary cavities, e.g., electromagnetic field in it can be either trapped or released; its position and the field amplification in it are tunable. Our study opens a new research door for the combining of magneto-optical materials and photonic crystals. [ABSTRACT FROM AUTHOR]

We present an unconditionally stable weighted Laguerre polynomials (WLPs)-based finite-difference time-domain (FDTD) algorithm for modeling wave propagation in isotropic cold plasma. The plasma effects contributed by electrons and collisions are modeled by current density vectors collocated with the electric field components. The factorization-splitting scheme is employed to translate the large sparse matrix equation in the conventional WLP-FDTD algorithm into two and six tri-diagonal ones for 2-D and 3-D problems, respectively. This procedure significantly improves the efficiency of the WLP-FDTD algorithm in terms of computational expenses. The stretched-coordinate perfectly matched layer with a complex-frequency-shifted factor is implemented as the absorbing boundary condition. The accuracy and efficiency of the proposed algorithm are validated by numerical examples. [ABSTRACT FROM PUBLISHER]

A unidirectional waveguide plays the key role in optical communication system. The unidirectional edge modes in two-dimensional magneto-optical photonic crystals have a unique feature because they are robust against imperfections or disruptions along the edge, but they can hardly form an optical beam. In order to obtain a unidirectional air waveguide, we have studied the coupling effect of two unidirectional edge modes basing on band calculations and numerical simulations. With a waveguide width of 1.5a, an ideal unidirectional air waveguide is achieved. The unidirectional air waveguide has great performance because of its broad working bandwidth, high extinction ratio, single-mode feature, and air waveguide configuration. It has an advantage over the unidirectional edge waveguide because it can focus the wave energy and form a one-way beam. An analytical analysis is also given for the results. [ABSTRACT FROM PUBLISHER]

An unconditionally stable stochastic finite-difference time-domain (S-FDTD) with weighted Laguerre polynomials algorithm is proposed to model wave propagation in isotropic cold plasma random media. The mean value and the variance of field components as caused by the variability or uncertainty of electrons and collisions of the plasma are calculated by a single run. In addition, the perfectly matched layer is implemented via formulation in the stretched-coordinate system. Numerical example validates the accuracy and efficiency of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In this letter, an efficient implementation of the iterative unconditionally stable finite-difference time domain (FDTD) based on weighted Laguerre polynomials (WLPs) algorithm is presented for isotropic cold plasma. The iterative scheme is employed to reduce the splitting error in WLP-FDTD with factorization-splitting procedure. Meanwhile, a stretched-coordinate perfectly matched layer with a complex-frequency-shifted factor is used as the absorbing boundary condition. Numerical example demonstrates the accuracy and efficiency of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

In this letter, a stretched coordinate (SC) perfectly matched layer (PML) is presented for the iterative finite-difference time-domain (FDTD) method based on weighted Laguerre polynomials (WLPs). By applying the iterative scheme, the splitting error in WLP-FDTD is reduced. The SC-PML can be easily combined with a complex-frequency-shifted factor to improve the performance for low frequency and evanescent wave absorption. Numerical example demonstrates the accuracy and effectiveness of the proposed algorithm. [ABSTRACT FROM PUBLISHER]

We have developed a model of frequency modulated distributed feedback laser with intracavity phase modulator and have shown that it can operate in two different regimes, only one of which has good frequency-modulated (FM) response. We have identified the combination of the laser parameters that forces laser to operate in high FM efficiency regime. The results of our initial experiments support these conclusions. [ABSTRACT FROM AUTHOR]

A stretched-coordinate (SC) based perfectly matched layer (PML) is presented for the weighted Laguerre polynomial finite-difference time-domain (WLP-FDTD) method. Compared to the split-field PML, the new SC-PML is easy to combine with a complex-frequency-shifted (CFS) factor to improve the PML efficiency. The proposed SC-PML is also background material independent. Numerical examples show the effectiveness of the proposed algorithm. [ABSTRACT FROM PUBLISHER]