A 2.4-GHz Low-Power Low-IF Receiver and Direct-Conversion Transmitter in 0.18-μm CMOS for IEEE 802.15.4 WPAN Applications

In this paper, a low-power low-IF receiver and a direct-conversion transmitter (DCT) suitable for the IEEE standard 802.15.4 radio system at the 2.4-GHz band are presented in 0.18-mum deep n-well CMOS technology. By using vertical NPN (V-NPN) bipolar junction transistors in the baseband analog circuits of the low-IF receiver, the image rejection performance is improved and the power consumption is reduced. In addition, by applying the V-NPN current mirrored technique in a DCT, the carrier leakage is reduced and the linearity performance is improved. The receiver has 10 dB of noise figure, -15 dBm of third-order input intercept point, and 35 dBc of image rejection. The transmitter has more than -2 dBm of transmit output power, -35 dBc of local oscillator leakage, and -46 dBc of the transmit third harmonic component. The receiver and transmitter dissipate 6 and 9 mA from a 1.8-V supply, respectively     

Reconstruction of conductivity and current density images using only one component of magnetic field measurements

Magnetic resonance current density imaging (MRCDI) is to provide current density images of a subject using a magnetic resonance imaging (MRI) scanner with a current injection apparatus. The injection current generates a magnetic field that we can measure from MR phase images. We obtain internal current density images from the measured magnetic flux densities via Ampere's law. However, we must rotate the subject to acquire all of the three components of the induced magnetic flux density. This subject rotation is impractical in clinical MRI scanners when the subject is a human body. In this paper, we propose a way to eliminate the requirement of subject rotation by careful mathematical analysis of the MRCDI problem. In our new MRCDI technique, we need to measure only one component of the induced magnetic flux density and reconstruct both cross-sectional conductivity and current density images without any subject rotation.     

Multi-phased VSG CDMA with level clipping for high-rate transmission systems

In this letter, a multi-phased CDMA system employing a variable spreading gain (VSG) approach is proposed for high-rate applications, based on four algorithms for selecting a multi-code set. From simulation results, in addition to simple receiver structure thanks to level clipping, the multi-phased VSG CDMA system provides an high bit rate transmission, while maintaining an acceptable performance degradation.     

Biodegradable Thin Metal Foils and Spin‐On Glass Materials for Transient Electronics

Biodegradable substrates and encapsulating materials play critical roles in the development of an emerging class of semiconductor technology, generally referred as “transient electronics”, whose key characteristic is an ability to dissolve completely, in a controlled manner, upon immersion in ground water or biofluids. The results presented here introduce the use of thin foils of Mo, Fe, W, or Zn as biodegradable substrates and silicate spin‐on‐glass (SOG) materials as insulating and encapsulating layers, with demonstrations of transient active (diode and transistor) and passive (capacitor and inductor) electronic components. Complete measurements of electrical characteristics demonstrate that the device performance can reach levels comparable to those possible with conventional, nontransient materials. Dissolution kinetics of the foils and cytotoxicity tests of the SOG yield information relevant to use in transient electronics for temporary biomedical implants, resorbable environmental monitors, and reduced waste consumer electronics.     

Metal Organic Framework-MXene Nanoarchitecture for Fast Responsive and Ultra-Stable Electro-Ionic Artificial Muscles

Electro-ionic soft actuators, capable of continuous deformations replacing non-compliant rigid mechanical components, attract increasing interest in the field of next-generation metaverse interfaces and soft robotics. Here, a novel MXene (Ti₃C₂T_x) electrode anchoring manganese-based 1,3,5-benzenetricarboxylate metal-organic framework (MnBTC) for ultrastable electro-ionic artificial muscles is reported. By a facile supramolecular self-assembly, the Ti₃C₂T_x-MnBTC hybrid nanoarchitecture forms coordinate bond, hydrogen bond, and hydrophilic interaction with the conducting polymer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), resulting in a mechanically flexible and electro-ionically active electrode. The superior electrical and electrochemical performances of the electrode stem from the synergistic effects between intrinsically hierarchical nanoarchitecture of MnBTC and rapid electron transport behavior of Mxene, leading to fast diffusion and accommodation of ions in the ion-exchangeable membrane. The developed artificial muscle based on Ti₃C₂T_x-MnBTC is found to exhibit high bending displacement (12.5 mm) and ultrafast response time (0.77 s) under a low driving voltage (0.5 V), along with wide frequency response (0.1–10 Hz) and exceptional stability (98% retention at 43,200 s) without any distortion of actuation performance. Furthermore, the designed electro-active artificial muscle is successfully used to demonstrate mimicry of eye motions including eyelid blinking and eyeball movement in a doll.     

Highly Stretchable and Wearable Thermotherapy Pad with Micropatterned Thermochromic Display Based on Ag Nanowire–Single‐Walled Carbon Nanotube Composite

Due to the increasing interest in wearable devices, flexible and stretchable film heaters have been widely studied, as alternatives to heaters with conventional rigid shapes. Herein, a highly stretchable film heater (SFH) based on the silver nanowire (Ag NW)–single‐walled carbon nanotube composite with a thermochromic display on a polydimethylsiloxane (PDMS) substrate is successfully fabricated. The SFH shows excellent electrical conductivity, high mechanical stretchability, and outstanding reliability, with no significant degradation after 10 000 stretching cycles under tensile strain. The SFH can be heated to the target temperature (≈60 °C) within 30 s at a low applied voltage. In addition, a thermochromic display is fabricated to help prevent the risk of low‐temperature burns. Red (R), green (G), and blue (B) thermochromic microparticles (TMPs) are synthesized using drop‐based microfluidic technology. The TMPs show RGB colors at room temperature but change to a white color above a certain temperature. The TMPs are arrayed into a PDMS stencil on the basis of their particle sizes using the rubbing technique. The micropatterned thermochromic display, which functions as a visual alarm, combined with the SFH can pave the way for the development of thermotherapy pads for next‐generation wearable devices in the medical field.     

Highly Power‐Efficient Rack‐Level DC Power Architecture Combined with Node‐Level DC UPS

This letter presents a highly efficient rack‐level DC power architecture combined with a node‐level DC uninterruptible power supply (UPS). The proposed system can provide almost the equivalent power efficiency of a high‐voltage DC data center without any change in the existing power infrastructure. The node‐level DC UPS combined with a power distribution board provides high power efficiency as well as lower UPS installation costs. Implemented on a rack, the entire power system can be monitored through a network.     

3‐Level Envelope Delta‐Sigma Modulation RF Signal Generator for High‐Efficiency Transmitters

This paper presents a 0.13 μm CMOS 3‐level envelope delta‐sigma modulation (EDSM) RF signal generator, which synthesizes a 2.6 GHz‐centered fully symmetrical 3‐level EDSM signal for high‐efficiency power amplifier architectures. It consists of an I‐Q phase modulator, a Class B wideband buffer, an up‐conversion mixer, a D2S, and a Class AB wideband drive amplifier. To preserve fast phase transition in the 3‐state envelope level, the wideband buffer has an RLC load and the driver amplifier uses a second‐order BPF as its load to provide enough bandwidth. To achieve an accurate 3‐state envelope level in the up‐mixer output, the LO bias level is optimized. The I‐Q phase modulator adopts a modified quadrature passive mixer topology and mitigates the I‐Q crosstalk problem using a 50% duty cycle in LO clocks. The fabricated chip provides an average output power of –1.5 dBm and an error vector magnitude (EVM) of 3.89% for 3GPP LTE 64 QAM input signals with a channel bandwidth of 10/20 MHz, as well as consuming 60 mW for both channels from a 1.2 V/2.5 V supply voltage.     

Routing Protocol for Heterogeneous Hierarchical Wireless Multimedia Sensor Networks

Recently, wireless multimedia sensor networks (WMSNs) have emerged as one of the most important technologies, driven by the development of powerful multimedia device such as CMOS. WMSNs require several factors such as resource constraints, specific QoS, high bandwidth and so on. In this paper, we propose a hierarchical heterogeneous network model based routing protocol for WMSNs. In our proposal, proposed network model is classified into monitoring class, delivery class and aggregation class. Also we define two kinds of the routing path in order to ensure bandwidth and QoS. In simulation results, we illustrate the performance of our proposal.