A 24 GHz highly-linear upconversion mixer, based on a duplex transconductance path (DTP), is proposed for automotive short-range radar sensor applications using the 65-nm CMOS process. A mixer with an enhanced transconductance stage consisting of a DTP is presented to improve linearity. The main transconductance path (MTP) of the DTP includes a common source (CS) amplifier, while the secondary transconductance path (STP) of the DTP is implemented as an improved cross-quad transconductor (ICQT). Two inductors with a bypass capacitor are connected at the common nodes of the transconductance stage and switching stage of the mixer, which acts as a resonator and helps to improve the gain and isolation of the designed mixer. According to the measured results, at 24 GHz the proposed mixer shows that the linearity of output 1-dB compression point (OP1dB) is 3.9 dBm. And the input 1-dB compression point (IP1dB) is 0.9 dBm. Moreover, a maximum conversion gain (CG) of 2.49 dB and a noise figure (NF) of 3.9 dB is achieved in the designed mixer. When the supply voltage is 1.2 V, the power dissipation of the mixer is 3.24 mW. The mixer chip occupies an area of 0.42 mm2.
The results of colossal magnetoresistance (CMR) properties of La0.83Sr0.17Mn1.21O3 (LSMO) films grown by pulsed injection MOCVD technique onto various substrates are presented. The films with thicknesses of 360 nm and 60 nm grown on AT-cut single crystal quartz, polycrystalline Al2O3, and amorphous Si/SiO2 substrates were nanostructured with column-shaped crystallites spread perpendicular to the film plane. It was found that morphology, microstructure, and magnetoresistive properties of the films strongly depend on the substrate used. The low-field MR at low temperatures (25 K) showed twice higher values (−31% at 0.7 T) for LSMO/quartz in comparison to films grown on the other substrates (−15%). This value is high in comparison to results published in literature for manganite films prepared without additional insulating oxides. The high-field MR measured up to 20 T at 80 K was also the highest for LSMO/quartz films (−56%) and demonstrated the highest sensitivity S = 0.28 V/T at B = 0.25 T (voltage supply 2.5 V), which is promising for magnetic sensor applications. It was demonstrated that Mn excess Mn/(La + Sr) = 1.21 increases the metal-insulator transition temperature of the films up to 285 K, allowing the increase in the operation temperature of magnetic sensors up to 363 K. These results allow us to fabricate CMR sensors with predetermined parameters in a wide range of magnetic fields and temperatures.
AbstractThe wireless power transfer (WPT) system has been widely used in various fields such as household appliances, electric vehicle charging and sensor applications. A frequency reconfigurable magnetic resonant coupling wireless power transfer (MRCWPT) system with dynamically enhanced efficiency by using the frequency reconfigurable metamaterial is proposed in this paper. The reconfigurability is achieved by adjusting the capacitance value of the adjustable capacitor connected in the coil of the system. Finite element simulation results have shown that the frequency reconfigurable electromagnetic metamaterial can manipulate the direction of the electromagnetic field of the system due to its abnormal effective permeability. The ultra-thin frequency reconfigurable metamaterial is designed at different working frequencies of 14.1 MHz, 15 MHz, 16.2 MHz, 17.5 MHz, 19.3 MHz, 21.7 MHz and 25 MHz to enhance the magnetic field and power transfer efficiency (PTE) of the system. Frequency reconfigurable mechanism of the system with the frequency reconfigurable metamaterial is derived by the equivalent circuit theory. Finally, further measurement which verifies the simulation by reasonable agreement is carried out. PTE of the system by adding the metamaterial are 59%, 73%, 67%, 66%, 65%, 60% and 58% at different working frequencies. PTE of the system with and without the metamaterial is 72% and 49% at the distance of 120 mm and the frequency of 15 MHz, respectively.
Copper nanofilms are extensively used in the field of material science research. Nanoparticles and nanostructures of copper have various utilities in the field of photocatalytic and sensor applications. The transition metal nanoparticles and nanostructures supply plenty free electrons which drastically enhances the optical and electrical properties compared to bulk material. Here, copper thin films have been deposited on glass slides and silicon substrates using an indigenously developed DC magnetron sputtering system. These depositions have been carried out at three different time spans keeping the magnetron discharge current, working vacuum and target to substrate distance unaltered. The objective of this work is to study the crystalline structure and measure the thickness of the copper nanofilm deposited at three different times. The synthesized films were characterized by using X-Ray Fluorescence (XRF), X-Ray Diffractometer (XRD) and Secondary Ion Mass Spectrometer (SIMS). Characteristic peaks of copper (111) along with Cu2O (110), (220) and (111) were obtained from the XRD pattern. The average grain size of the deposited films has been calculated using Debye-Scherrer equation. The film thickness ranging from 80-160 nm for various time spans were measured from depth profile analysis using SIMS data.
<p>In this study, we used a natural resource, yarosite minerals, as a Fe<sub>2</sub>O<sub>3</sub> precursor. Yarosite minerals were used for the synthesis of LaFeO<sub>3</sub>/Fe<sub>2</sub>O<sub>3</sub> doped with ZnO via a co-precipitation method using ammonium hydroxide, which produced a light brown powder. Then, an ethanol gas sensor was prepared using a screen-printing technique and characterized using gas chamber tools at 100,200, and 300 ppm of ethanol gas to investigate the sensor's performance. Several factors that substantiate electrical properties such as crystal and morphological structures were also studied using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), respectively. The crystallite size decreased from about 61.4 nm to 28.8 nm after 0.5 mol% ZnO was added. The SEM characterization images informed that the modified LaFeO<sub>3</sub> was relatively the same but not uniform. Lastly, the sensor's electrical properties exhibited a high response of about 257% to 309% at an operating temperature that decreased from 205 ℃ to 180 ℃. This finding showed that these natural resources have the potential to be applied in the development of ethanol gas sensors in the future. Hence, yarosite minerals can be considered a good natural resource that can be further explored to produce an ethanol gas sensor with more sensitive response. In addition, this method reduces the cost of material purchase.</p>
Soft conductors show great promise in multifunctional sensor applications. However, both electronically and ionically conductive materials are often vulnerable during large deformation or at low temperatures, leading to reduced sensitivity,...