Current‐Mode Electronically Tunable Universal Filter Using Only Plus‐Type Current Controlled Conveyors and Grounded Capacitors

In this paper we present a new current‐mode electronically tunable universal filter using only plus‐type current controlled conveyors (CCCII+s) and grounded capacitors. The proposed circuit can simultaneously realize lowpass, bandpass, and highpass filter functions—all at high impedance outputs. The realization of a notch response does not require additional active elements. The circuit enjoys an independent current control of parameters ω₀ and ω₀ / Q. No element matching conditions are imposed. Both its active and passive sensitivities are low.     

基于可调F-P滤波器的光纤光栅传感器阵列查询技术

利用可调 F- P滤波器对四个光纤光栅组成的传感器阵列进行波长扫描 ,借助示波器和探测器对滤波光束的时序分布进行观察 ,实现地址查询。比较波长漂移前后传感阵列的反射谱 ,可用于解调 ,实验结果与预期值基本一致。选用反射率相差悬殊的光栅作传感元 ,有利于增加测量范围     

Tri‐band Microstrip Bandpass Filter Using Dual‐Mode Stepped‐Impedance Resonator

This letter presents a compact dual‐mode tri‐band bandpass filter by using a short‐circuited stub‐loaded stepped‐impedance resonator (SIR) and a short‐circuited stub‐loaded uniform impedance resonator. Also, a hairpin SIR geometry is introduced to miniature the size of this filter while maintaining excellent performance. The use of a short‐circuited stub at the central point of the hairpin SIR can generate two resonant modes in two passbands. Its equivalent circuit structure is analyzed by using the even‐odd mode theory. For demonstration purposes, a tri‐band filter for the applications of the Global Positioning System at 1.57 GHz, Worldwide Interoperability for Microwave Access at 3.5 GHz, and wireless local area networks at 5.2 GHz is designed, fabricated, and measured.     

A Versatile Universal Capacitor‐Grounded Voltage‐Mode Filter Using DVCCs

In this paper, a versatile three‐input five‐output universal capacitor‐grounded voltage‐mode filter is proposed. The circuit employs two differential voltage current conveyors as active elements together with two grounded capacitors and four resistors as passive elements. The proposed configuration can be used as either a single‐input five‐output or three‐input two‐output. Unlike the previously reported works, it can simultaneously realize five different generic filtering signals: lowpass, bandpass, highpass, bandreject, and allpass. It still maintains the following advantages: (i) the employment of all grounded capacitors, (ii) no need to employ inverting‐type input signals, (iii) no need to impose component choice, (iv) orthogonal control of the resonance angular frequency ω_o and the quality factor Q, and (v) low active and passive sensitivity performances.     

基于重构等效啁啾超结构光纤光栅的可调谐微波光子滤波器的仿真研究

提出了一种新型的基于重构等效啁啾(REC)超结构光纤光栅的可调谐微波光子滤波器的结构。根据REC技术, 利用同一块均匀相位掩模板可以灵活地设计制作出具有不同斜率的线性群时延的光纤光栅。作为有限冲击响应(FIR)滤波器的抽头延时单元, 不同光纤光栅之间群时延的差值决定了滤波器的自由频程(FSR)。通过改变可调谐激光器的输出波长来选择不同的抽头间时延差从而达到调谐FSR目的。仿真结果表明, 该滤波器可以实现中心频率从21 GHz到33 GHz的连续可调。事实上, 由于REC技术的灵活性, 在理论上对于任意给定的频段和调谐范围, 这种新型的滤波器结构都能够实现。     

Widely Tunable 1.55‐μm Detuned Dual‐Mode Laser Diode for Compact Continuous‐Wave THz Emitter

We report the use of a widely tunable detuned dual‐mode laser diode (DML) as a compact and portable continuous‐wave THz emitter. The wavelength difference between the two lasing modes of this DML can be tuned from 2.4 nm to 9.3 nm by using integrated microheaters. The power difference between these modes is less than 1 dB, and the side‐mode suppression ratio is greater than 30 dB over the entire tuning range.     

A Dual‐Mode Narrow‐Band Channel Filter and Group‐Delay Equalizer for a Ka‐Band Satellite Transponder

This paper presents the design of a narrow‐band channel filter and its group‐delay equalizer for a Ka‐band satellite transponder. We used an 8th order channel filter for high selectivity with an elliptic‐integral function response and an inline configuration. We designed a 2‐pole, reflection‐type, group‐delay equalizer to compensate for the steep variation of the group‐delay at the output of the channel filter, keeping the thermal stability at ±7 ns of group‐delay variation at the band edges over 15–55 ·C. We devised a new tuning technique using short‐ended dummy cavities and used it for tuning both the filter and equalizer; this removes the necessity of additional tuning after the cavities are assembled. Through measurement, we demonstrate that the group‐delay‐equalized filter meets the equipment requirements and is appropriate for satellite input multiplexers.     

Functional Coating of Porous Silica Microparticles with Native Biomembranes towards Portable Flow‐Through Biochemical Microreactors

In biological cells, various transmembrane enzymes function as highly effective chemical reactors confined in space with characteristic length scales of tens of nanometers to micrometer. However, it is still challenging to quantitatively confine membranes in compact reactor platforms without losing their biochemical functions. Here, a simple and straightforward strategy towards the fabrication of a new flow‐through reactor by the functional coating of porous silica microparticles with sarcoplasmic reticulum membranes is described. After a short incubation, the membranes achieve the homogeneous, full coverage of the particle surface, spanning across pores with the diameter of about 100 nm. By using the underlying pores as cavity reservoirs, transmembrane enzyme (Ca²⁺‐ATPase) in the membrane retains their capability of ATP hydrolysis. This enables us to confine 1.1 m² of native membranes containing a large amount of Ca²⁺‐ATPase (approx. 10 nmol) in a column‐packaged, flow‐through reactor with merely 1.8 mL volume, which cannot be achieved by the reconstitution of proteins in artificial lipid membranes or condensation of membranes in suspensions. The distinct functional levels corresponding to different reaction buffers can be reproduced even after many buffer exchanges over 14 days, confirming the stability and reproducibility of the membrane‐particle hybrid reactors.     

A Novel Dual‐Mode Bandpass Filter Based on a Defected Waveguide Resonator

A novel dual‐mode bandpass filter (BPF) using a dual spiral‐shaped defected ground waveguide (DGW) resonator is proposed in this letter. The dual‐mode characteristic of this filter is achieved by loading a defected T‐shaped stub at the midline of the spiral‐shaped DGW resonator. Also, non‐orthogonal input and output feed‐lines are adopted in the filter. Based on the compact DGW structure, a dual‐mode BPF with central frequency of 1.5 GHz for the global positioning system is designed, fabricated, and measured. Measured results agree well with the predicted response and verify the proposed methodology.     

Low‐Voltage Tunable Pseudo‐Differential Transconductor with High Linearity

A novel tunable transconductor is presented. Input transistors operate in the triode region to achieve programmable voltage‐to‐current conversion. These transistors are kept in the triode region by a novel negative feedback loop which features simplicity, low voltage requirements, and high output resistance. A linearity analysis is carried out which demonstrates how the proposed transconductance tuning scheme leads to high linearity in a wide transconductance range. Measurement results for a 0.5 μm CMOS implementation of the transconductor show a transconductance tuning range of more than a decade (15 μA/V to 165 μA/V) and a total harmonic distortion of ?67 dB at 1 MHz for an input of 1 V_pp and a supply voltage of 1.8 V.     

Resonance wavelength‐tunable microcavities

We describe a microcavity device structure which allows external control of the resonance wavelength of the cavity via alignment of a liquid crystal layer within the cavity. This also allows the study of the spectral and spatial distribution of emission from a single emitter within the microcavity. We have been able to shift the resonance modes of the microcavity by up to 56 nm. The tunability of the microcavity has been used to further investigate the coupling between an emitter and a microcavity. The potential technical applications for this type of device are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

A Novel Log‐Domain First‐Order Multifunction Filter

A new log‐domain first‐order multifunction filter is proposed in this letter. The proposed filter is systematically derived using the state‐space synthesis procedure from a corresponding block diagram. It provides low‐pass (LP), high‐pass (HP), and all‐pass (AP) responses simultaneously for a single input signal. The filter circuit has a very simple structure since it uses only bipolar junction transistors (BJTs) and a grounded capacitor. It can be electronically tuned by changing an external current. The filter has a greater bandwidth due to its inherent current‐mode and log‐domain operations. PSPICE simulations are given to confirm the theoretical analysis.     

High‐Mobility ZnO Thin Film Transistors Based on Solution‐processed Hafnium Oxide Gate Dielectrics

The properties of metal oxides with high dielectric constant (k) are being extensively studied for use as gate dielectric alternatives to silicon dioxide (SiO₂). Despite their attractive properties, these high‐k dielectrics are usually manufactured using costly vacuum‐based techniques. In that respect, recent research has been focused on the development of alternative deposition methods based on solution‐processable metal oxides. Here, the application of the spray pyrolysis (SP) technique for processing high‐quality hafnium oxide (HfO₂) gate dielectrics and their implementation in thin film transistors employing spray‐coated zinc oxide (ZnO) semiconducting channels are reported. The films are studied by means of admittance spectroscopy, atomic force microscopy, X‐ray diffraction, UV–Visible absorption spectroscopy, FTIR, spectroscopic ellipsometry, and field‐effect measurements. Analyses reveal polycrystalline HfO₂ layers of monoclinic structure that exhibit wide band gap (≈5.7 eV), low roughness (≈0.8 nm), high dielectric constant (k ≈ 18.8), and high breakdown voltage (≈2.7 MV/cm). Thin film transistors based on HfO₂/ZnO stacks exhibit excellent electron transport characteristics with low operating voltages (≈6 V), high on/off current modulation ratio (～10⁷) and electron mobility in excess of 40 cm² V^?1 s^?1.     

Self‐Assembly of Tunable Nanocrystal Superlattices Using Poly‐(NIPAM) Spacers

Understanding and controlling 3D nanocrystal self‐assembly is a fundamental challenge in materials science. Assembly enables the unique optical and electronic properties of nanocrystals to be exploited in macroscopic materials, and also opens up the possibility to couple the optical response of nanocrystals to the optical modes of the superlattice. To date, assembly of such nanocrystal superlattices (NCSL) has focussed on fixed, close packed structures with particle separations of just 1–3 nm. To achieve highly crystalline structures with tunable optical response, the nanocrystal interparticle separation needs to be precise and easily variable but >50 nm. Here, we show the preparation of nanocrystal superlattices with spacings of 50–500 nm assembled from gold‐poly‐N‐isopropylacrylamide core‐shell particles and the characterization of their fascinating diffraction behavior by means of UV‐vis spectroscopy. These nanocrystal superlattices exhibit pronounced diffraction in the visible (440‐560 nm) with peak half‐widths of the order of 10 nm. The position of the Bragg peak is simply tuned by adjusting the particle volume fraction. Due to the thermoresponsive nature of the polymer shell, temperature is used to initiate crystallization or melting of the superlattice. Heating and cooling cycles cause highly reversible melting/recrystallization in less than a minute.     

Multi‐harmonic Suppression Band‐Pass Filter for Communication System

For the purpose of decreasing intermodulation distortion, a new multi‐harmonic suppression band‐pass filter based on a microstrip radial stub is studied. Compared with traditional resonator filters, the new filter can suppress the second, third, and even fourth harmonics directly. The dimension of the filter is about 0.3 λ_g0 × 0.13 λ_g0 (λ_g0 is the guiding wavelength at the resonant frequency). Only one gap was introduced, so lower insertion loss can be obtained. Basic agreement between the measured and simulated results has been achieved.