Analysis and Design of a Quadrature Down-Conversion Mixer for UHF RFID Readers

A quadrature mixer with a shared transconductor stage is analyzed,including voltage conversion gain, linearity, noise figure, and image rejection. The analysis indicates it has better performance than a conventional Gilbert mixer pair in commutating mode. A quadrature down-conversion mixer based on this topology is designed and optimized for an ultra high frequency RFID reader. Operating in the 915MHz ISM band, the presented quadrature mixer measures a conversion gain of 12.5dB,an IIP3 of 10dBm, an IIP2 of 58dBm, and an SSB noise figure of 17.6riB. The chip was fabricated in a 0. 18μm 1P6M RF CMOS process and consumes only 3mA of current from a 1.8V power supply.

A Wide-Band High-Linearity Down-Conversion Mixer for Cable Receptions

We analyze a wide-band,high-linearity down-conversion mixer for cable receptions that is implemented in 0. 35μm SiGe BiCMOS technology. The bandwidth of the RF （radio frequency） input covers the range from 1 to 1.8GHz. The measured input power at the - 1dB compression point of the mixer reaches ＋ 14.23dBm. The highest voltage conversion gain is 8. 31dB, while the lowest noise figure is 19.4dB. The power consumed is 54mW with a 5V supply. The test result of the down-conversion mixer is outlined.

A CMOS high-IF down-conversion mixer for WLAN 802.11a applications

A low noise, high conversion gain down-conversion mixer for WLAN 802.11a applications, which adopts the high intermediate frequency （IF） topology, is presented. The input radio frequency （RF）band, local oscillator（LO）frequency band and output IF are 5.15 to 5.35, 4.15 to 4.35 and 1 GHz, respectively. Source resistive degeneration technique and pseudo-differential Gilbert topology are used to achieve high linearity, and, current bleeding technique and LC resonant loads are used to acquire a low noise figure. In addition, the mixer adopts a common-source transistor pair cross-stacked with a source follow pair（CSSF）circuit as an output buffer to enhance the mixer＇s conversion gain but not deteriorate the other performances. The mixer is implemented in 0.18 μm RF CMOS（complementary metal oxide semiconductor transistor）technology and the chip area of the mixer including all bonding pads is 580 μm×1 185 μm. The measured results show that under a 1.8 V supply, the conversion gain is 10.1 dB; the input 1 dB compression point and the input-referred third-order intercept point are-3.5 and 5.3 dBm, respectively; the single side band （SSB）noise figure （NF）is 8.65 dB, and the core current consumption is 3.8 mA.

An Implementation of a CMOS Down-Conversion Mixer for GSM1900 Receivers

A 1.9GHz down-conversion CMOS mixer with a novel folded Gilbert cell,intended for use in GSM1900 （PCS1900） low-IF receivers,is fabricated in a RF 0.18μm CMOS process. The prototype demonstrates good performance at an intermediate frequency of 100kHz. It achieves a conversion gain of 6dB, SSB noise figure of 18. 5dB （1MHz IF） ,and IIP3 11.5dBm while consuming a 7mA current from a 3.3V power supply.

Folded down-conversion mixer for a 60 GHz receiver architecture in 65-nm CMOS technology

We present the design of a folded down-conversion mixer which is incorporated at the final down-conversion stage of a 60 GHz receiver. The mixer employs an ac-coupled current reuse transconductance stage. It performs well under low supply voltages, and is less sensitive to temperature variations and process spread. The mixer operates at an input radio frequency(RF) band ranging from 10.25 to 13.75 GHz, with a fixed local oscillator(LO) frequency of 12 GHz, which down-converts the RF band to an intermediate frequency(IF) band ranging from dc to 1.75 GHz. The mixer is designed in a 65 nm low power(LP) CMOS process with an active chip area of only 0.0179 mm2. At a nominal supply voltage of 1.2 V and an IF of 10 MHz, a maximum voltage conversion gain(VCG) of 9.8 d B, a double sideband noise figure(DSB-NF) of 11.6 d B, and a linearity in terms of input 1 d B compression point(Pin,1d B) of-13 d Bm are measured. The mixer draws a current of 5 m A from a 1.2 V supply dissipating a power of only 6 m W.

基于Hessian局部线性嵌入和MLP-Mixer的液体火箭发动机涡轮泵轻量化故障诊断框架

作为液体火箭发动机推进剂输送系统的关键部件,涡轮泵的运行状态直接影响着整个运载系统的性能,然而,现有的故障诊断方法往往面临特性参数选择片面及计算复杂度高等问题。针对上述局限,提出了面向涡轮泵的轻量化故障诊断框架。所提方法利用Hessian局部线性嵌入算法对信号时域、频域及时频特征进行降维,并引入一种轻量化的深度学习模型MLP-Mixer作为分类器,进而实现不同故障状态的辨识。采用某型号涡轮泵试车数据验证了所提方法的有效性,结果表明,该方法能够在保障诊断精度的同时有效降低计算复杂度,提高诊断效率。

Quantum frequency down-conversion of single photons at 1552 nm from single InAs quantum dot

Near-infrared single photon sources in telecommunication bands, especially at 1550 nm, are required for long-distance quantum communication. Here a down-conversion quantum interface is implemented, where the single photons emitted from single In As quantum dot at 864 nm is down converted to 1552 nm by using a fiber-coupled periodically poled lithium niobate（PPLN） waveguide and a 1.95 μmm pump laser, and the frequency conversion efficiency is ~40%. The singlephoton purity of quantum dot emission is preserved during the down-conversion process, i.e., g^（（2））（0）, only 0.22 at 1552 nm.This present technique advances the Ⅲ-Ⅴ semiconductor quantum dots as a promising platform for long-distance quantum communication.

Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric downconversion in the periodically-poled lithium niobate on insulator(LNOI)waveguide.We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum,such as narrowing,broadening,and splitting.We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth.Our study may promote the development of on-chip photon sources in the LNOI platform,as well as opens up a way to engineer photon frequency state.

Time Evolution and Squeezing of Degenerate and Non-degenerate Coupled Parametric Down-Conversion with Driving Term

By properly selecting the time-dependent unitary transformation for the linear combination of the number operators, we construct a time-dependent invariant and derive the corresponding auxiliary equations for the degenerate and non-degenerate coupled parametric down-conversion system with driving term. By means of this invariant and the Lewis-Riesenfeld quantum invariant theory, we obtain closed formulae of the quantum state and the evolution operator of the system. We show that the time evolution of the quantum system directly leads to production of various generalized one- and two-mode combination squeezed states, and the squeezed effect is independent of the driving term of the Hamiltonian. In some special cases, the current solution can reduce to the results of the previous works.

Parametric down-conversion with local operation and two-way classical communication

The decoy-state quantum key distribution protocol suggested by Adachi et al. （Phys. Rev. Lett 99 180503 （2007）） is proven to be secure and feasible with current techniques. It owns two attractive merits, i.e., its longer secure transmission distance and more convenient operation design. In this paper, we first improve the protocol with the aid of local operation and two-way classical communication （2-LOCC）. After our modifications, the secure transmission distance is increased by about 20 km, which will make the protocol more practicable.

Design of Software-Defined Down-Conversion and Up-Conversion: An Overview

In recent years, much attention has been paid to software-defined radio （SDR） technologies for multimode wireless systems SDR can be defined as a radio communication system that uses software to modulate and demodulate radio signals. This article describes concepts, theory, and design principles for SDR down-conversion and up-conversion. Design issues in SDR down-conversion are discussed, and two different architectures, super-heterodyne and direct-conversion, are proposed. Design issues in SDR up-conversion are also discussed, and trade-offs in the design of filters, mixers, NCO, DAC, and signal processing are highlighted.

Intracavity Spontaneous Parametric Down-Conversion in Bragg Reflection Waveguide Edge Emitting Diode

A four-wavelength Bragg reflection waveguide edge emitting diode based on intracavity spontaneous parametric down-conversion and four-wave mixing （FWM） processes is made. The structure and its tuning characteris- tic are designed by the aid of FDTD mode solution. The laser structure is grown by molecular beam epitaxy and processed to laser diode through the semiconductor manufacturing technology. Fourier transform infrared spectroscopy is applied to record wavelength information. Pump around 1.071 μm, signal around 1.77μm, idler around 2.71 μm and FWM signal around 1.35μm are observed at an injection current of 560mA. The influ- ences of temperature, carrier density and pump wavelength on tuning characteristic are shown numerically and experimentally.

Simple and practical method of characterizing the parametric down-conversion source

Parametric down-conversion（PDC） sources play an important role in quantum information processing, therefore characterizing their properties is necessary. Here we present a statistical model to assess the properties of the PDC source with certain distribution, such as the brightness and photon channel transmissions, we only need to measure the singles and coincidences counts in a few seconds. Furthermore, we validate the model by applying it to a PDC source generating highly non-degenerate photon pairs. The results of the experiment indicate that our method is more simple, efficient, and less time consuming.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Optimal Design and Experimental Study of Tightly Coupled SCR Mixers for Diesel Engines

Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.

Terahertz high-sensitivity SIS mixer based on Nb–AlN–NbN hybrid superconducting tunnel junctions

The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.

Fuzzy Comprehensive Analysis of Static Mixers Used for Selective Catalytic Reduction in Diesel Engines

The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.

Experimental and numerical investigations on micromixing performance of multi-orifice cross-flow jet mixers

Multi-orifice cross-flow jet mixers(MOCJMs)are used in various industrial applications due to their excellent mixing efficiency,but few studies have focused on the micromixing performance of MOCJMs.Herein,the flow characteristics and micromixing performance inside the MOCJM were investigated using experiments and computational fluid dynamics(CFD)simulations based on the Villermaux/Dushman system and the finite-rate/modified eddy-dissipation model.The optimal A value was correlated with the characteristic parameters of MOCJMs to develop a CFD calculation method applicable to the study of the micromixing performance of the MOCJMs.Then the micromixing efficiency was evaluated using the segregation index XS,and the effects of operational and geometric parameters such as mixing flow Reynolds number(ReM),flow ratio(RF),total jet area(ST),the number of jet orifices(n),and outlet configuration on the micromixing efficiency were investigated.It was found that the intensive turbulent region generated by interactions between jets,as well as between jets and crossflows,facilitated rapid reactions.XS decreased with increasing ReM and decreasing RF.Furthermore,MOCJMs with lower ST,four jet orifices,and the narrower outlet configuration demonstrated a better micromixing efficiency.This study contributes to a deeper understanding of the micromixing performance of MOCJMs and provides valuable guidance for their design,optimization,and industrial application.

NUMERICAL INVESTIGATION OF AERODYNAMIC AND MIXING CHARACTERISTICS OF SCARFED LOBED MIXER FOR TURBOFAN ENGINE EXHAUST SYSTEM

The flow field and aerodynamic performances for the scarfed lobed forced mixer are studied based on a computational fluid dynamics（CFD） technique. A series of computations are conducted to obtain the effects of the bypass ratio and the scarf angle on the mixing performance for the scarfed lobed mixer. Results show that the scarfed lobed mixer is reduced in the system weight. Meanwhile, aerodynamic performances are slightly improved compared with the normal lobed mixer. Two reasons for causing the mixing enhancement between the core and the bypass flow are as follows： （1） The stream-wise vortices shed from the training edge of the half/full scarfed lobed mixer earlier is enhanced by about 25%. （2） The mixing augmentation is also associated with the increase of the interface length caused by scarfing. The thermal mixing efficiency is enhanced with the increase of the bypass ratio and the scarfing angle. The scarfed lobed mixer design has no negative effects on the pressure loss. The total pressure recovery coefficient reaches above 0. 935 in various bypass ratios and scarfed angles. As the bypass ratio increases, the total pressure recovery coefficient also increases for the scarfed lobed mixer.

Low Voltage CMOS Gilbert Mixers for Bluetooth Transceiver

Based on the analyses of the reported Gilbert mixers operating at low supply vol tage,a down-conversion mixer and an up-conversion mixer for 2.4GHz bluetooth transceiver are presented with the modified low voltage design techniques,respe ctively.Feedback and current mirror techniques suitable for low voltage operatio n are used to improve the linearity of the up-conversion mixer,and folded-casc ode output stage is adopted to optimize the noise and conversion gain of the dow n-conversion mixer operating at low voltage.Based on 0.35μm CMOS technology,s imulations are performed with 2V supply voltage.The results show that 20dBm thir d-order intercept point (IIP3),87mV output signal amplitude are achieved for up -conversion mixer with about 3mA current;while 20dB conversion gain (CG),6.5nV /Hz input-referred noise,4.4dBm IIP3 are obtained for down-conversion mixer with about 3.5mA current.