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991.
《Microelectronics Journal》2015,46(6):415-421
A 5 GHz LC VCO (voltage-controlled oscillator) with automatic amplitude control (AAC) and automatic frequency-band selection (AFBS) for 2.4 GHz ZigBee transceivers is presented. Instead of continuous feedback loop, an alternative amplitude calibration scheme is proposed in this paper to alleviate the deficiencies inherent in the conventional approach. It helps to keep the VCO at optimum amplitude to avoid saturation of the cross-coupled transistors and therefore stabilizes the phase noise performance over process, voltage and temperature variations. For the ZigBee application with 16 frequency channels, a coarse tuning loop is added in this work to implement the frequency-band selection using the AFBS mechanism. The VCO core and the digital AAC, AFBS modules have been fully integrated in a 2.4 GHz ZigBee transceiver which was fabricated in a 0.18 μm RF-CMOS technology. The current consumption is 4.7 mA at 4.85 GHz with 1.8 V power supply and a chip area of about 0.285 mm2 is occupied. The VCO is capable of operating from 4.67 GHz to 5.18 GHz and the measured phase-noise level is –120 dBc/Hz at 1 MHz offset from a 4.85 GHz carrier. The tuning sensitivity KVCO of the VCO is about 78 MHz/V with 0.9 V control voltage. 相似文献
992.
《Microelectronics Journal》2015,46(10):988-995
A 10-bit 300-MS/s asynchronous SAR ADC in 65 nm CMOS is presented in this paper. To achieve low power, binary-weighed capacitive DAC is employed without any digital correction or calibration. Consequently, settling time for the capacitive DAC would be a dominant limiting factor for the ADC operating speed. A novel architecture is proposed to optimize the settling time for the capacitive DAC, which depends merely on the on-resistance of switches and the capacitance of unit capacitor and irrelevant to the resolution. Therefore, high-speed high-resolution SAR ADC is possible. What is deserved to highlight is that the architecture improves the ADC performance at a fraction of the cost, with only some capacitors and control logic added. Post-layout simulation has been made for the SAR ADC. At a 1.2-V supply voltage and a sampling rate of 300 MS/s, it consumes 1.27 mW and achieves an SNDR of 60 dB, an SFDR of 67.5 dB, with the Nyquist input. The SAR ADC occupies a core area of 450×380 μm2. 相似文献
993.
《Microelectronics Journal》2015,46(11):1039-1045
A new CMOS differential current-mode AGC on the division operation based is presented. The operation principle consists in detection of both positive and negative envelopes of the differential input signal cycles, respectively. The output signal with constant magnitude is obtained by dividing the differential input signal to the difference between the positive and negative detected envelopes. The new current-mode architecture of the proposed AGC (composed only by an envelope detector and a divider stage) diminishes significantly the settling time, the circuit complexity and the power consumption. The circuit yields an input dynamic range of 15 dB and provides a constant magnitude output signal in the frequency range from 10 MHz to 70 MHz. The current consumption is 5 mA from a single 3.3 V supply voltage. The simulations performed in 0.13 µm CMOS process confirm the theoretically obtained results. 相似文献
994.
《Microelectronics Journal》2015,46(10):970-980
Traditional digital controls mostly use digital–analog converters to convert input and output voltages into digital coding to achieve control. This paper proposes the use of two digital ramps with two different frequencies to replace a digital–analog converter. This approach can produce seven bit resolution for the DPMW signal. In addition, we use an all-digital DLL phase correction concept to further enhance the resolution of the DPWM signal by an additional three bits, resulting in 10-bit DPWM signal resolution. The proposed circuit uses 0.35 μm CMOS processes, with a core area of 0.987 mm2, a system switching frequency of 500 KHz, an input voltage range of 3.3–4.2 V, and an output voltage range of 5 V. Output voltage measurement accuracy reaches 99%, while the system reaches efficiency of 91% with output loads of up to 500 mA. 相似文献
995.
《Microelectronics Reliability》2015,55(6):937-944
In this paper, the development and reliability of a platinum-based microheater with low power consumption are demonstrated. The microheater is fabricated on a thin SiO2 bridge-type suspended membrane supported by four arms. The structure consists of a 0.6 μm-thick SiO2 membrane of size 50 μm × 50 μm over which a platinum resistor is laid out. The simulation of the structure was carried out using MEMS-CAD Tool COVENTORWARE. The platinum resistor of 31.0 Ω is fabricated on SiO2 membrane using lift-off technique. The bulk micromachining technique is used to create the suspended SiO2 membrane. The temperature coefficient of resistance (TCR) of platinum used for temperature estimation of the hotplate is measured and found to be 2.2 × 10−3/°C. The test results indicate that the microhotplate consumes only 11.8 mW when heated up to 400 °C. For reliability testing, the hotplate is continuously operated at higher temperatures. It was found that at 404 °C, 508 °C and 595 °C, the microhotplate continuously operated up to 16.5 h, 4.3 h and 4 min respectively without degrading its performance. It can sustain at least 53 cycles pulse-mode of operation at 540 °C with ultra-low resistance and temperature drifts. The structure has maximum current capability of 19.06 mA and it can also sustain the ultrasonic vibration at least for 30 min without any damage. 相似文献
996.
Tarek Abu‐Husein Swen Schuster Martin Kind Tobias Santowski Adrian Wiesner Ryan Chiechi Egbert Zojer Andreas Terfort Michael Zharnikov 《Advanced functional materials》2015,25(25):3943-3957
Using a representative model system, here electronic and structural properties of aromatic self‐assembled monolayers (SAMs) are described that contain an embedded, dipolar group. As polar unit, pyrimidine is used, with its orientation in the molecular backbone and, consequently, the direction of the embedded dipole moment being varied. The electronic and structural properties of these embedded‐dipole SAMs are thoroughly analyzed using a number of complementary characterization techniques combined with quantum‐mechanical modeling. It is shown that such mid‐chain‐substituted monolayers are highly interesting from both fundamental and application viewpoints, as the dipolar groups are found to induce a potential discontinuity inside the monolayer, electrostatically shifting the core‐level energies in the regions above and below the dipoles relative to one another. These SAMs also allow for tuning the substrate work function in a controlled manner independent of the docking chemistry and, most importantly, without modifying the SAM‐ambient interface. 相似文献
997.
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1000.
介绍了供自动气象站用的小功率太阳能电源控制系统,能够在检测电池及太阳能特性的基础上,及时调整充电电压及电流来确定优化的充电策略,以充分利用太阳能。同时系统具有信息存储、实时监测和显示等特点,实现锂电池的快速充电。论文分析了系统的构成、工作原理和工作效率,实验表明,其发电量的利用效率最高可达95%,系统能够满足自动气象站的用电需求。 相似文献