Sharif Digital Repository

A new low-power current reuse topology is proposed for the GPS receiver's RF front-end that combines the higher conversion gain and suppressed noise figure characteristics of cascade structures with the low power consumption of stacked architectures. The presented circuit, called 1.5-stage LMV cell, consists of LNA, Mixer and VCO (LMV) in such a formation that boosts LNA gain and suppresses mixer's noise figure by cascading the two stages while reusing their currents in the two stacked quadrature VCOs and placing the mixer's upper tree switches at the vicinity of on-off regions. The circuit is designed and its layout is generated in TSMC 0.18μm CMOS technology. Post-layout simulations using... 

A new ultra wideband (UWB) pulse generator covering a-10 dB bandwidth of 2.4-4.6 GHz with a tunable center frequency of 5-5.6 GHz to mitigate coexistence issues of impulse radio UWB (IR-UWB) systems and IEEE802.11.a WLAN or other narrowband (NB) systems in 90 nm-CMOS technology is proposed. The UWB pulse is generated based on frequency up-conversion of the first derivative of the Gaussian pulse, which creates an adjustable null in the frequency spectrum. Simulation results show that employing the proposed pulse generator mitigates the mutual interference between UWB and WLAN systems, significantly. The proposed transmitter consists of a low frequency signal generator, an LC oscillator and a... 

A compact low power circuit for implementation of a direct conversion OQPSK modulator is proposed. The circuit consists of a digital to analog converter, a low pass filter and an up-converter mixer. By embedding these three blocks, the circuit performance is enhanced and the total power consumption is reduced. The mixer is designed base on a Gilbert cell with on chip inductor loads. Instead of transconductance transistors of Gilbert cell, a fully deferential current mode DAC is used and proficiently a low pass filter is embedded between them and therefore the linearity of total system is improved. All of circuits are designed based on 0.18 μm CMOS technology with a single 1.8 volt power... 

In most of the microfluidic applications, it is necessary to have a mixed fluid from the beginning, but in microchannels, due to facing with low Reynolds flows, the fluids flow in the channel by the laminar regimes. Hence the mixing process is a challenging problem and researchers are trying to present fast and reliable micromixers. In this paper, using Ionic Polymer-Metal Composites (IPMCs), an active micromixer has been designed. To investigate the appropriateness of IPMC, using experimental and simulation tests, we show that the IPMC actuator is a potential candidate as an active element of microfluidic micromixers  

This article presents the theory and implementation of a quadrature and differential RF front-end receiver. Combining balun, low-noise amplifier (LNA), mixer, and oscillator in a single stage, the proposed circuit, named the Blixator, is well suited for low-power applications. The baseband's transimpedance amplifier (TIA) also shares part of its dc current with the Blixator cell, resulting in sub-milliwatt power consumption. To avoid additional power and area by quadrature LO generation, the I/Q signals are generated at RF, employing the inductors already required for providing the dc current path of the LNA transistors. The expressions for gain, noise figure (NF), and phase noise of the... 

Both nonlinear rheology and finite EDL thickness effects on the mixing process in an electroosmotically actuated Y-sensor are being investigated in this paper, utilizing a depthwise averaging method based on the Taylor dispersion theory. The fluid rheological behavior is assumed to obey the power-law viscosity model. Analytical solutions are obtained assuming a large channel width to depth ratio for which a 1-D profile can efficiently describe the velocity distribution. Full numerical simulations are also performed to determine the applicability range of the analytical model, revealing that it is able to provide accurate results for channel aspect ratios of ten and higher and quite... 

This paper presents a broadband low-loss quadrature-hybrid-based network that enhances the phase and the amplitude matching of quadrature signals. The performance of this network is investigated, and a detailed theoretical analysis is provided. Several stages of this network can be cascaded to generate broadband balanced quadrature signals. Each stage has a loss of 0.5 dB and enhances the image rejection ratio (IRR) by approximately 8 dB. Compared with the conventional polyphase quadrature signal generation methods, the proposed network enables lower insertion loss, wider bandwidth, and reduced sensitivity to process variations. To verify the theoretical analyses, two proof-of-concept... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

In this paper, a new formulation based on conversion matrix method is proposed to analyze near-the-carrier local ocillator (LO) noise down conversion to IF in microwave mixers. This method could be easily applied to analyze LO noise down conversion in any type of mixer. Practical results of this method have been compared with the envelope method and measurement results. It is shown that despite the conventional AM noise suppression in balanced mixers, the near-the-carrier LO noise suppression does not occur necessarily at the center frequency of hybrid in balanced mixers. AM noise suppression values are predicted precisely. © 2006 IEEE  

Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

Generally speaking, most micro-fluidic mixing systems are limited to the low Reynolds number regime in which diffusion dominates convection, and consequently the mixing process tends to be slow and it takes a relatively long time to have two fluids completely mixed. Therefore, rapid mixing is essential in micro-fluidic systems. In order to hasten the mixing process in micro scale, in this study we come up with a novel scheme for a two dimensional micro-fluidic mixer which encompasses three pairs of electrodes, one pair embedded in the mixing chamber and two pairs located in the micro-channels before and after the mixing chamber. The width of the middle pair is assumed to be twice of the... 

A terahertz modulator based on the Type-II superconductor flux flow oscillator has been proposed. Analytical calculations are presented and the effects of intrinsic and extrinsic parameters such as disorder strength of crystal, penetration depth, frequency, and amplitude of the modulated current on the radiation power spectrum have been studied. The proposed structure also exhibits a mixer-like behavior, in the sense that its output harmonics range from the washboard frequency up to the superconductor gap frequency, so the input signal is practically mixed with the washboard frequency and its harmonics. The modulation index for each harmonic of this modulator has also been investigated. This... 

In the case that phased array systems are not capable of attenuating interferences, Radio Frequency (RF) front-ends and Analog Digital Converters (ADCs) with a large dynamic range are required to avoid saturation of the receiver. This leads to a higher power consumption. In this paper, employing N-path circuits in Mixer-First receivers, a novel method is introduced in which spatial and frequency blockers are eliminated right before entering the system on the antennas input. In fact using this technique, adjustable spatial notch filter and band-pass frequency filter are implemented to suppress spatial and frequency interferences. The proposed method enhances the robustness and effectiveness... 

The present study is concerned with the computational fluid dynamics (CFD) simulation of turbulent dispersion of immiscible liquids, namely, water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software. To study the droplet size distribution (DSD), the Eulerian formulation incorporating a population balance model (PBM) was employed. For the Eulerian–Lagrangian approach, a discrete phase model (DPM) in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution (RTD) of droplets. In both approaches, a shear stress transport (SST)... 

The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD, with Reynolds numbers ranging from 20 to 160. The performance of the new mixer is compared with those of Kenics, SMX, and Komax static mixers. The pressure drop ratio (Z-factor), coefficient of variation (CoV), and extensional efficiency (α) features have been used to evaluate power consumption, distributive mixing, and dispersive mixing performances, respectively, in all mixers. The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation. CFD results are consistent with measured data and those obtained by... 

Separation and lysis of RBCs play an important role in diagnosis of different diseases. Although they have been partially studied in several researches, a comprehensive study on integrating both separation and lysis units on a single chip has been seen rarely in the literature. Also, the factors related to the chemical lysis process have not been investigated in detail. In this study, we introduce a novel microfluidic channel design for sequential RBC's separation and lysis. For the separation part, an active method with an electric field was applied to the cells. Besides, a novel mixer was designed for mixing the cell solution and lysis reagent. In the lysis section, we used a mathematical... 

Separation of circulating tumor cells (CTCs) from blood samples and subsequent DNA extraction from these cells play a crucial role in cancer research and drug discovery. Microfluidics is a versatile technology that has been applied to create niche solutions to biomedical applications, such as cell separation and mixing, droplet generation, bioprinting, and organs on a chip. Centrifugal microfluidic biochips created on compact disks show great potential in processing biological samples for point of care diagnostics. This study investigates the design and numerical simulation of an integrated microfluidic device, including a cell separation unit for isolating CTCs from a blood sample and a... 

The mixer geometry has substantial effect on mixing performance of different micro/nanomixers. Despite past numerous studies dedicated to mixing of liquid flow streams, there are less efforts to investigate the geometry effects on gas mixing performances. In this work, we focus on gas-gas mixing through different micro/nanoscale mixers under slip and transitional flow regimes. We use the direct simulation Monte Carlo (DSMC) method to provide accurate and reliable results in such flow regimes. To extend our study, we implement different geometrical parameters in our consideration including the mixer size, the impact angle between two incoming gas streams, and the contraction height located in... 

In this paper a self-oscillating mixer is presented fundamental signal generated by the oscillator subcircuit in the mixing process. The oscillator core consumes 3mA of current from a 1.8 V DC supply and results in an output power of -0.867 dBm per oscillator, and a measured phase noise of -91, -102 and -108 dBc/Hz at 100 KHz, 600 KHz and 1 MHz from the carrier, respectively. In the mixing process the proposed mixer achieved IIP3 of 0 dBm with conversation gain of 1.93 dB. The circuit was designed and simulated in 0.18-μm CMOS technology by ADS2010