Long resonator micromachined tunable GaAs-AlAs Fabry-Perot filter

We present novel concepts for tunable optical filters. Long resonant cavities of about 30-/spl mu/m length have been realized with two-chip designs. GaAs technology has been applied to filters that are designed for the use in dense wavelength-division multiplexing (WDM) at wavelengths around 1550 nm. A finesse of 46.7, a full-width at half-maximum (FWHM) of 1.2 nm and electrostatic tuning over a range of 103 nm with an applied voltage of 35 V has been achieved. An alternative tuning concept that allows to tune the resonator length 4 /spl mu/m by heating Ni-Cr resistors placed on the suspending beams of a membrane with an applied voltage of 2.7 V has been realized.     

A two-pole tunable filter with constant fractional-bandwidth characteristics

In this paper, a tunable filter with constant fractional bandwidth is designed and fabricated on ε_r = 2.2, h = 0.508 mm duroid substrates. A new mixed electrical and magnetic coupling scheme is introduced by this structure to achieve an overall constant coupling coefficient during the tuning range, which can meet the requirement of constant fractional bandwidth. A detailed analysis on the external quality (Q_ext) and coupling coefficient is presented. Two-chip capacitors (C_M = 1 pF), using radio frequency (RF) and microwave capacitors, were used to enhance Q_ext. The Q_ext (22 ± 3) shows a relatively small variation over the entire tuning range. The tunable constant fractional-bandwidth filter shows a tuning range of 1.28–1.86 GHz, a 3-dB bandwidth of 5.3 ± 0.6% and an insertion loss of 5.11–2.69 dB. The measured and simulation results are in a good agreement.     

Uniplanar EBG structure with improved compact and wideband characteristics

In recent years, there has been growing interest in investigating electromagnetic bandgap (EBG) structures, and diverse kinds of EBG structures have been suggested for applications of microwave circuits and antennas [1?7]. To make EBG more suitable for actual applications, much effort has been devoted to realise compact size for the EBG structure. Uniplanar compact EBG (UC-EBG), as a successful compact EBG structure introduced by F. Yang et al., has been exclusively investigated because of the easy fabrication, low cost and compatibility with standard planar circuit technology [5?7].     

Switched-capacitor resonator structure with improved performance

A novel switched-capacitor resonator circuit is proposed. Its centre frequency is insensitive to the finite bandwidth and gain of the opamps used     

Compact UWB bandpass filter with improved upper-stopband performance

a compact microstrip-line ultra-wideband (UWB) bandpass filter (BPF) using aperture-backed interdigital coupled lines and a stub-loaded folded stepped-impedance resonator (SLFSIR) is presented. in the design, the first four resonant frequencies of this SLFSIR are properly adjusted to be placed evenly within the UWB while the fifth resonant frequency is raised above 16.0 GHz to improve upper-stopband performance. furthermore, the aperture-backed interdigital coupled lines can create a transmission zero to cancel the fifth resonant mode of the SLFSIR to make a wider upper-stopband as well as raising the coupling degree to relax the tight line spacing. after optimisation of this filter, good UWB bandpass behaviour is theoretically realised and experimentally confirmed.     

Initialization for improved IIR filter performance

A new method for initializing the memory registers of infinite impulse response (IIR) filters is introduced. In addition to providing improved performance as compared to other methods of initialization, this method is unique in that it makes no prior assumptions regarding the input-signal content. Therefore, the method applies equally well to a variety of IIR filter designs and applications. The method is best suited for signal processing applications in which `batch' processing of the data is used. However, sequential processing, can be accommodated when delays at the beginning of a processing segment can be tolerated     

二阶有源低通滤波器设计与仿真研究

介绍了利用子系统的级联、反馈及电路仿真手段设计有源二阶滤波器简便方法。给出了电路参数选取的技巧。对反馈电路的接入点选择;系统传递函数的计算与验证都给出了详细的分析。仿真实验证明,通过调试可变电阻值,可以得到性能优良的二阶滤波器。     

Direct-coupled resonator filters with improved selectivity

A method is outlined whereby a narrow-band direct-coupled resonator filter may be derived from an elliptic-function low-pass prototype. The construction and performance of a three-resonator waveguide cavity filter designed on this basis is described.     

带有环形谐振器的T形光子晶体滤波器

提出了一种带有环形谐振器的T形光子晶体滤波器,利用时域有限差分法研究了滤波器传输特性,分析了光子晶体结构参数对其传输特性影响。结果表明：该结构具有可调性开关波长、传输率高及频带宽的特点,在光子晶体集成制作、光通信器件制作等方面具有潜在的应用价值。     

All-fiber compound ring resonator with a ring filter

The new all-fiber compound ring resonator has two rings: a primary one that serves as a resonator, and a secondary one that serves as a filter. The main contribution of this resonator is to increase the free spectral range by choosing the fiber lengths in the compound ring cavity. This resonator with a large free spectral range can be readily used as a doped fiber laser. The optimum resonant conditions of the resonator are discussed by using an equivalent model and by the transfer matrix method. The frequency responses of the output and of the circulating intensities are given. Mode suppression by the vernier effect is demonstrated. Comparison with a fiber Fox-Smith resonator is also presented     

Design and fabrication of GaAs-GaAlAs micromachined tunable filter with thermal strain control

In this paper, we present the design and fabrication of a novel GaAlAs-GaAs micromachined vertical cavity filter with a thermal strain control layer for wide wavelength tuning. The integration of a thermal strain control layer and heating element enables wavelength tuning induced by heating. The proposed tunable filter under thermal tuning operation provides us large tuning range over conventional micromachined tunable filters using electrostatic force. The calculated result shows a possibility of large continuous tuning range of over 100 nm. We fabricated a micromachined GaAlAs-GaAs vertical cavity filter with a strain control layer. The temperature dependence of the filter can be freely controlled either with temperature insensitive operation or with an enhanced temperature dependence, which depends on the thickness of the thermal strain control layer. We demonstrate a thermal wavelength tuning of 53 nm with a low tuning voltage of 6.1 V for the first time.     

Compact UWB PCML bandpass filter with L- and C-shaped resonator

A novel ultra-wideband (UWB) bandpass filter with four resonant modes is proposed based on a parallel coupled microstrip line (PCML) with L- and C-shaped resonators. The coupling factor of the PCML structure depends on the impedance of the feeding network. The PCML coupling factor can be enhanced by using a feeding network with smaller characteristic impedance. With an L-shaped feeding network and C-shaped middle microstrip line a non-uniform resonator is constructed with the first two resonant modes falling within the UWB. The other two resonant modes within the UWB can be obtained by adjusting the width of both the L- and C-shaped resonators. Overall the designed filter exhibits good UWB passband behaviour with insertion loss < -0.2 dB and group delay < 0.15 ns.     

UHF double dielectric resonator filter with linearised tuning range

A UHF double dielectric resonator filter operating in the TE_01δ mode has been constructed with a high Q, wide (14%) and reasonably linear tuning range. This has been achieved by varying the gap between the resonators, and using the influence of the end wall on the movable resonator. The experimental device is readily scaleable to the cellular radio wave bands     

Ultrashort optical pulse transmission characteristics of verticallycoupled microring resonator add/drop filter

The ultrashort optical pulse transmission characteristics of a vertically coupled microring resonator (VCMRR) filter were measured at 1.55 μm wavelength, and the transmission capacity per channel was evaluated. The pulsewidth at the output was measured to be 3.4 ps, when 1.2 ps input pulse with a sech pulse shape from a fiber laser was incident on the microring resonator filter with a fullwidth at half-maximum (FWHM) of 0.75 nm (94 GHz). From this result, the maximum transmission capacity of the filter was estimated to be approximately 50 Gb/s. The pulse broadening through the filter was theoretically analyzed, and it was confirmed that the pulse broadening evaluated from the bandwidth of the filter spectrum response were in good agreement with the measured results     

Periodic stepped-impedance ring resonator (PSIRR) bandpass filter with a miniaturized area and desirable upper stopband characteristics

A periodic stepped-impedance ring resonator (PSIRR) is proposed to design dual-mode bandpass filters with a miniaturized area and desirable upper stopband characteristics. Design parameters of a PSIRR include impedance ratio R of the hi-Z to low-Z sections, their lengths, and number of impedance steps 2N. The resonant characteristics of PSIRRs with various N and R values are investigated by both the transmission-line theory and electromagnetic simulation. Proper choice of the above parameters leads to an optimal reduction of circuit area and extension of upper rejection bandwidth. Two extra transmission zeros exist in the upper stopband and are tunable via changing the arm lengths of the line-to-ring coupling structure. Realized by the standard microstrip technology, the dual-mode PSIRR bandpass filter has not only the first spurious response at higher than 3.7/spl times/ the passband frequency, but also an area reduction of better than 60% against a conventional ring filter. Experimental results of several fabricated circuits validate the analysis and theoretical prediction.     

DGS resonator with interdigital capacitor and application to bandpass filter design

A novel defected ground structure (DGS) microstrip resonator is proposed. The proposed DGS resonator has the resonant and anti-resonant characteristic that is very similar to those of a surface acoustic wave resonator or a film bulk acoustic resonator (FBAR). To confirm the validity of the proposed resonator, bandpass filters were designed and implemented using series and parallel resonators.     

带电磁带隙结构微带天线的时域溅射特性研究

在微带天线上加电磁带隙(Electromagnetic Band Gap,EBG)结构,能够有效减小天线工作频带内的雷达散射截面(Radar Cross Section,RCS),目标识别比较困难.利用时域散射波形特性,与频率RCS相结合,实现低RCS目标的测量.采用并行时域有限差分(Finite-Difference Time-Domain,FDTD)对带EBG结构的微带天线的时域溅射特性进行了研究,分析了其时域散射波形形成机理,研究了其双站时域散射特性以及频域RCS的变化规律.从而得出,带有EBG结构的天线虽然具有较低的频域RCS,"隐身"特性较好,但是其时域散射波形开始部分场值的幅度很大,需要经过一段时间场值稳定后才能呈现出低散射特性,本文把这种特性叫做时域溅射特性.     

EBG对圆波导介质棒相控阵扫描特性的改善

将电磁带隙(EBG)结构应用到圆波导介质棒相控阵列中,利用EBG结构所具有的表面波带隙特性有效消除了相控阵中的扫描盲区.比较了无限阵列的扫描特性和有限阵列中心单元方向图在EBG加载前后的变化.仿真分析表明,以EBG结构作为圆波导介质棒相控阵的地平面,能有效消除扫描盲区,扩展扫描范围.     

高品质因子聚合物可重构微环谐振腔滤波器

以聚合物ZPU-44和聚砜(PSU,polysulfone risi n)分别作为波导包层和芯层材料,采用倒脊形波导结构,设计并 优化了聚合物可重构微环谐振腔滤波器的波导截面参数、弯曲半径、耦合区波导长度和间距 以及调谐电极 等结构参数,分析了其谐振滤波特性。采用传统的微加工工艺制备了聚合物可重构微环谐振 腔滤波器并进 行了测试。结果表明,其在通信波段1550nm附 近的自由光谱范围(FSR)为0.15nm,3dB带宽约为0.0235nm, 品质因子Q达6.60×10⁴,在0~ 4V电压范围内实现了0.5~12.95dB消光比的调谐,且 谐振波长调谐一 个FSR的电压为4.75V,与理论设计基本 相 符。本文的聚合物可重构微环谐振腔滤波器可用于集成波导可调谐光延时线和可调谐滤波。     

A compact open-loop resonator filter with a wide stopband response

This paper presents a new class of microstrip slow-wave open-loop resonator filter with reduced size and improved stopband characteristics. A comprehensive treatment of both resonator ends loaded with triangular and rectangular shapes is described, leading to the invention of a microstrip slow-wave open-loop resonator. A four-resonator bandpass filter is designed at the operating frequency about 2 GHz, bandwidth of 60 MHz. The size of the slow-wave open-loop resonator is optimized from the standpoint of the unloaded Q-factor. The proposed filter is not only compact size due to the slow-wave effect but also has a wider upper stopband resulting from the dispersion effect. The filter design of this type will be described in detail. The experimental results are demonstrated and discussed.