Modern Physics Letters B

Phase Locked Loop (PLL) circuit plays an important part in electronic communication system in providing high-frequency clock, recovering the clock from data signal and so on. The performance of PLL affects the whole system. As the frequency of PLL increases, designing a PLL circuit with lower jitter and phase noise becomes a big challenge. To suppress the phase noise, the optimization of Voltage Controlled Oscillator (VCO) is very important. As the power supply voltage degrades, the VCO becomes more sensitive to supply noise. In this work, a three-stage feedforward ring VCO (FRVCO) is designed and analyzed to increase the output frequency. A novel supply-noise sensing (SNS) circuit is proposed to suppress the supply noise’s influence on output frequency. Based on these, a 1.2 V 2 GHz PLL circuit is implemented in 110 nm CMOS process. The phase noise of this CMOS charge pump (CP) PLL is 117 dBc/Hz@1 MHz from test results which proves it works successfully in suppressing phase noise.

A 2.5 Gbps transimpedance amplifier (TIA) with the feedback resistance self-adaptively adjusted is designed for the application of optical receivers in passive optical network and implemented in Global Foundries (GF) 0.18 $\mu$m CMOS standard process. The main structure of the circuit consists of an improved three-stage current multiplexing push-pull inverter. With the diode-connected-transistor placed at each end of the inverter, the extra pole will be pulled away in order to increase the stability of the loop system. The feedback resistance of TIA is connected in parallel with the NMOS transistor, and the gate voltage of the tube is adjusted automatically to control the resistance value of this parallel structure in order to overcome the defect of the inverter which will work in the linear region on the condition of excessive optical power. A low-dropout linear regulator (LDO) is adopted from the power supply to the TIA to isolate power supply noise. The measured results demonstrate that the fabricated TIA with a photodetector capacitance of 3.2 pF has a transimpedance gain of 41.64 dB$\mathrm{\Omega }$ with a current signal frequency of 2.5 Gbit/s, and a −3 dB bandwidth of 2.35 GHz. The average input-referred noise current spectral density within the bandwidth is185 pA/Hz${}^{1/2}$, signal rise time is 195 ps, fall time is 227 ps, eye diagram height is 28 mV, optical sensitivity is −30.6 dBm, and power consumption is only 52 mW at 3.3 V power supply voltage, the chip area is $0.22\times 0.3$ mm².

Traditional mechanical keys are gradually replaced with touch keys. Capacitive touch keys have advantages in achieving higher sensitivity with a longer service life and lower cost. Hence, the capacitive touch key technology is widely used in consumer electronic products. In use of household electric appliances, such as electric kettle, induction cooker and exhaust hood, sometimes the water vapor would condense into visible moisture or even the water would splash out of the pot when overheated, which may lead to a falsely trigger of touch key. So, waterproof becomes a big challenge in household electric appliances. This paper analyzes how water affects capacitive touch key and proposes a waterproof capacitive touch key sensor interface circuit to overcome the challenge. Sensing of touch key capacitor would be influenced only when water covers more than two touch keys. Compensating channels working in certain strategy are used to decrease the influence of water. For the same water capacitor, the bigger threshold voltage, the bigger change of the counting number. A much smaller threshold voltage is better to further weak the effect of water. The circuit is implemented in a standard 110 nm CMOS process. The measured results show that the touch Signal to Noise and Water Disturb Ration (SNWDR) is 20.7 dB which proves that the proposed waterproof capacitive touch key sensor interface circuit is effective against water splash.

Electrokinetics is a good fluid control tool in microfluidics and usually microelectrodes play important roles in such approach such as generating a desired electric field. Though the fabrication of two-dimensional (2D) microelectrodes has been relatively mature, they cannot generate uniform electric field in space. Three-dimensional (3D) microelectrodes developed more recently may solve the problem, however the fabrication process is usually complicated and requires micro-alignment platform. Non-toxic liquid metal is a good material for making electrodes that has been introduced into microfluidics. It can be injected directly into a microchannel to form an electrode, but its special physical properties make the injection process complex and difficult to control. In this study, we investigated an optimized manufacturing method of liquid metal microelectrode in a microchip by numerical analysis and experimental study. High quality microelectrodes on morphology and stability were successfully fabricated. A fluorescent enrichment experiment was performed using the developed microelectrode in a microfluidic chip. The result shows that the optimized fabrication method of microelectrode in this study provides a promising way for high quality and good performance liquid metal microelectrode formation, and paves the way for its versatile applications.

In order to improve the measurement accuracy of the step height measuring instrument, a semiconductor process was used to prepare the step height standard for calibrating the instrument. Aiming at the problem of deviation in the white light interferometer measuring step height standard, the cause of the measurement deviation was theoretically analyzed, combining the optical theory and the principle of instrument. In addition, referring to the semiconductor sputtering process, a method of sputtering metal layer on the surface of the step structure was proposed, and a set of universal step height standards with a nominal value of $20\sim 1000$ nm were developed for the step height measuring instrument. Finally, the step height standards with the sputtered metal layer were compared and measured, using the white light interferometer and nanometer measuring machine (NMM). The measurement error of the white light interferometer can be effectively controlled within 1%, which is beneficial to verify the measurement capability of the step height measuring instrument.

Portable and ultra-sensitive film bulk acoustic resonator (FBAR) is a promising device to satisfy the requirement of detecting gas and biological molecule. In this work, a novel sensing device was developed to achieve ultrahigh sensitivity, by coupling polymer micropillars with a FBAR substrate to form a two-degrees-of-freedom resonance system (FBAR-micropillars). We systematically investigated the effects of micropillar structure on the characteristics of FBAR-micropillars device by finite element method (FEM). It was found that the resonant frequency shift increased with increasing the height of micropillars (h) within a certain range, and the FBAR-micropillars device displayed nonlinear frequency response, which was opposite to the linear response of conventional FBAR devices. In addition, a positive resonant frequency shift was captured near the “coupled resonant point” of the FBAR-micropillars device. The geometric parameters of micropillars, including micropillar diameter and micropillar spacing could also cause a change of Q-factor and mass sensitivity. The optimized design of the proposed device achieved a threefold improvement in sensitivity relative to conventional FBAR without pillars, suggesting a feasible method to improve the mass sensitivity of acoustic resonators.

The development of micromanipulation technology has an important impact on the research in the microfield, which mainly focuses on the preparation and assembly of microcomponents, in which the microcomponent picking technology is used. The existing picking methods mainly use manipulation tools to clamp or adsorb components, which may destroy or fail to pick objects in the process of manipulation, and the efficiency is relatively low. In order to solve the problems in the existing manipulation methods, a new metal microcomponent picking method based on electrochemistry is proposed, which mainly uses the electrochemical principle to produce metal deposition, connect the manipulation tool and the object, and indirectly control the object by moving the manipulation tool. In this paper, the simulation software ABAQUS is used to pick up the microcopper wires with the length of 100, 200 and 300 $\mu$m by using a pipette with a nozzle diameter of 15 $\mu$m. The force curve between the tool and the object during the manipulation process is obtained. The feasibility of the method is verified by theoretical analysis and simulation experiments.

Printing orderly patterns on the insulating collector is the key for the development and application of flexible electronics. However, electrospinning on the insulating collector still has the problem of unstable jet due to the charge accumulation. The alternating current (AC)-induced electrohydrodynamic direct-writing (EDW) technology is a good way to decrease the interferences of charge repulsion, which is beneficial to printing orderly micro/nanostructures on the insulating collector. In this work, the sinusoidal AC-induced EDW is used to enhance the stability of charged jet and the deposition behaviors under AC electric field are also studied. The reciprocation transferring of charges induced by the AC electric field decreased the density of the accumulating charges on the insulating collector. The effect of AC electric field parameters on the direct-written micro/nanostructures are investigated to optimize the printing process. As the voltage peak increases, the fiber deposition bandwidth shows a trend of decreasing first and then increasing. Increasing the voltage frequency appropriately is beneficial to decrease the bandwidth of fiber deposition and to increase the stability of the jet. By improving the stability and controllability of the jet printing process, precise micro/nanopatterns can be direct-written on the insulating collector. This research provides a good foundation for expanding the application fields of EDW.

The nonlinear vibration of axially moving nanobeams at the microscale exhibits remarkable scale effects. A model of an axially moving nanobeam is established based on non-local strain gradient theory and considering two scale effects. The discrete equation of a non-autonomous planar system is obtained using the Galerkin method. The response characteristics of the system are determined using phase diagrams and Poincaré sections, and the effects of the scale parameters on the form of the motion are analyzed. The results show that as the non-local parameter and the material characteristic length parameter vary, the system undergoes multiple forms of motion, including periodic, period-doubling and chaotic motions. Two routes to chaos — period-doubling bifurcation and intermittent chaos — are identified in the variation ranges of the two scale parameters.

In this study, a tracing method for a scanning electron microscope was developed based on a heterodyne interferometer, which can directly trace the measured values to the laser wavelength and then to the internationally defined meter length reference. In this method, a sample scanning motion is introduced, and the measuring mirror of the interferometer is fixed on the sample stage. The movement and displacement of the sample stage is recorded by the laser interferometer displacement measurement system, which synchronously collects the secondary electrons or backscattered electron signals excited on the sample surface. The feature size of the sample is measured, and the value can be traced directly to the international unit of length using the frequency-stabilized laser reference, which proves that the proposed method is an absolute measurement method. This study analyzed the specific technology implementation methods and experimental results, including positioning control of the displacement system and its measurement and control during the measurement process. Measurement uncertainty budgets are also discussed. Experimental measurements were carried out and their accuracy was verified. Results showed that this method could effectively obtain the performance parameters of the feature size intuitively and significantly improve the measurement accuracy.

The complexity of System on Chip (SoC) is increasing with the scale of ICs, and Network on Chip (NoC) has become one of the most important solutions for SoC communication. As a significant point of NoC, research of routers and routing algorithms is receiving more and more attention from researchers and research institutes. This paper proposes a high-speed router on-chip router, which adopts wormhole switching mechanism, output queuing caching strategy, Credit-based flow control mechanism and Round-Robin arbitration mechanism, and the entire operation of the router is a two-stage flow. The selection of adaptive and deterministic routing algorithms can be done automatically, and finally, the performance parameters are evaluated.

In this paper, a bi-directional friction linear micro-motor (BFLM) driven by a set of micro-actuators was introduced and analyzed. The BFLM was fabricated using PolyMUMPs process. The impact dynamics model for the BFLM was established, and its motion equation was also derived that takes into account the friction and contact. The relative motion between the driving head and the slider, as well as forward or backward movement of the slider were analyzed in detail. The forward and backward movement displacement of the slider was measured, and the experimental results were in good agreement with theoretical predictions. The theoretical results show that the motion direction of the slider can be changed by controllable driving frequency to the BFLM. It was feasible to use a set of actuators to drive the slider in bi-directional motion.