Optimum field theory design of broad-band E-plane branchguide phase shifters and 180° couplers

Optimum rectangular waveguide E-plane branch guide phase shifters and 180° branch guide couplers are designed with the rigorous method of field expansion into normalized eigenmodes. The design includes both the higher order mode interaction between the step discontinuities and the finite step and branch heights. The phase shifter design applies the Schiffman principle to branch guide couplers where two ports are short-circuited. The 180° coupler design combines the advantage of the broadband potential of multiple-branch couplers with the low-insertion-loss qualities of E-plane stub-loaded phase shifters. A computer-optimized phase shifter prototype for the waveguide Ku-band (12-18 GHz) shows a 90°±1° differential phase shift with reference to an empty waveguide within about 23% bandwidth. Five-branch three-stub coupler prototypes, designed for 3±0.2 dB coupling, for the waveguide Ku- and Ka-bands (26-40 GHz) achieve a 180°±1° differential phase shift at the output ports within about 19% bandwidth, as well as more than 30 dB isolation and return loss. The theory is verified by measured results     

Substrate integrated waveguide (SIW) linear phase filter

A planar four-pole linear phase filter centered at 10GHz based on substrate integrated waveguide (SIW) is proposed. The filter is composed of four side-by-side horizontally oriented SIW cavities, which are coupled in turn by evanescent waveguide sections with three direct coupling and one cross coupling between the first and fourth SIW cavities. The SIW cavities are fed by microstrips through coupling slots. A curve-fitting technique is adopted to improve the efficiency of the design process. The measured results are presented and compared with the results simulated by a high-frequency structure simulator. Good agreement between the simulated and measured results is observed.     

Wideband two-layer SIW coupler: design and experiment

An original wideband two-layer substrate integrated waveguide directional coupler is presented. The structure provides attractive features including a flexible design with a wideband coupling and independent control of the transmission phase for arbitrary coupling levels. Characteristics of 18 dB isolation and 90 phase shift between direct and coupled ports are experimentally validated over 16 bandwidth.     

双层基片集成波导双通带滤波器设计

根据频率变换法的双通带滤波器综合理论,采用矩形基片集成波导谐振腔作为基本谐振单元,通过谐振器之间直接耦合设计了一种双层结构的双通带基片集成波导滤波器,利用Ansoft HFSS建立滤波器模型并进行全波仿真。仿真结果表明,两个通带内回波损耗均大于20 dB,插入损耗小于0.5 dB,通带之间的阻带衰减特性良好,同时其尺寸压缩了约50%,较好地实现了滤波器的小型化,满足了工程需要的技术指标。     

一种结构紧凑的毫米波波导滤波器的设计

提出了一种新颖的毫米波波导滤波器的设计方法,以常用的H面膜片波导滤波器为基础,配合并不常用的基于磁耦合原理的波导同轴转换,从波导短路端面引入E面耦合环,使输入输出方向在一条直线上,并将两者做一体化设计,在保证良好性能指标的情况下,结构设计更为紧凑,体积更小。该设计保证了在星载或机载设备上空间结构受限的情况下,器件安装与电缆连接的便利。借助HFSS全波电磁场仿真,成功地运用在中心频率30GHz毫米波波导带通滤波器的设计上,使设计方法更为简便实用。     

基于消失模耦合的脊波导滤波器设计方法

针对传统脊波导滤波器设计中没有考虑耦合结构频率特性导致设计精度不高的问题,文中提出了一种基于消失模耦合的脊波导滤波器设计方法。该方法将工作于消失模状态下的矩形波导结构等效为频变阻抗变换器模型,通过等效电路变换将耦合结构的频变特性影响转换为对传输线谐振腔电抗斜率参数的影响,采用逐级仿真策略确定滤波器结构尺寸,避免了耗时的全波仿真优化。最后,通过一个4阶切比雪夫特性的脊波导滤波器设计实例进行验证。全波仿真结果显示了与理论设计相同的通带内等波纹特性,验证了所提方法的有效性。     

任意波长间隔的光纤光栅梳状滤波器设计与实现

采样啁啾光纤光栅理论是实现超高信道数梳状滤波器的理想方案,但是一个啁啾模板只能实现特定波长间隔的光梳状滤波器。提出一种利用光纤布拉格光栅(FBG)直流相移实现任意波长间隔梳状滤波器方法。该方法只需一个啁啾模板与亚微米精度的位移台,在灵活性、简单性和制作成本方面有明显优势。仿真和实验表明FBG直流折射率调制可以引入任意的相位偏移。利用该方法实现了波长间隔为100,50,40GHz的梳状滤波器。最后分析了直流相移光栅长度与相位误差对滤波器边带抑制度的影响。     

一种磁耦合激励的圆极化滤波天线

提出了一种磁耦合激励的圆极化滤波天线。该天线采用磁耦合技术,实现了TEM模到TE10模的小型化转换,再经过矩形到圆波导的过渡,结合圆极化片的调节,获得向自由空间高效率转换的圆极化电磁波。在介质矩形波导中,引入了4个尺寸不同的耦合探针,通过对这些探针尺寸的调节,可以产生谐振和非谐振模式,获得期望的谐振频率、传输零点、滤波极点和谐振器间的耦合系数等,最终实现良好带外抑制的低频滤波天线性能。实测结果充分验证了设计的合理性。该设计思路对其他多级滤波天线也同样具有借鉴意义。     

Full-wave design and realization of multicoupled dual-mode circularwaveguide filters

A new full-wave method for the design and realization of dual-mode circular waveguide filters is presented. The rigorous CAD is a combination of the mode-matching and the finite-element techniques, which permits obtaining the Generalized Scattering Matrix for all the blocks that compose the structure (rectangular slots, cross-irises, and screws). The finite thickness of the irises, the higher order mode interaction, as well as the coupling and tuning screws are rigorously taken into account. A systematic design process for the different elements is described. A full prediction of resonant out-of-band spurious modes is accomplished prior to the filter construction. Special attention is devoted to the circuital model in order to save a great deal of computational effort in the final adjustment. A four-pole elliptic circular waveguide cavity filter has been designed and constructed. The experimental filter results show excellent agreement with theory     

Design and Modeling of a Nanomechanical Sensor Using Silicon Photonic Crystals

Conventionally a line defect in the photonic crystal (PhC) is used to create a waveguide for light propagation through the PhC. A PhC based filter is designed by introducing micro-cavities within the line defect so as to form the resonant bandgap structure for PhC. Such a PhC waveguide (PhCWG) filter shows sharp resonant peak in output wavelength spectrum. We proposed a suspended silicon bridge structure comprising this PhCWG filter structure. Since the output resonant wavelength is sensitive to the shape of air holes and defect length of the micro-cavity. Shift of the output resonant wavelength is observed for suspended PhCWG beam structure under particular force loading. In other words, the induced strain modifies the shape of air holes and the spacing among them. Such an effect leads to shift of resonant wavelength. Under optical detection limitation of 0.1 nm for resonant wavelength shift, the sensing capability of this nanomechanical sensor is derived as that vertical deformation is 20-25 nm at the center and the smallest strain is 0.005% for defect length. This innovative design conceptualizes a new application area for PhCs, i.e., the nanometer-scale physical sensors for strains and forces.     

基于新型优化窗的多维全相位数字滤波器设计

提出一种通用的多维全相位数字滤波器的设计方法.基于一维原型全相位数字滤波器(APDF),通过多维抽取变换,设计出具有任意平行六面体通带的多维APDF,并保持奈奎斯特约束特性和零相位特性.利用一种新型优化窗函数设计了性能优异的一维加窗APDF,将其作为一维原型滤波器,生成了不可分离的多维加窗APDF.实例表明,在滤波器长...     

Design flexibility of an open-loop resonator filter using similarity transformation of coupling matrix

In this letter, the design flexibility of an elliptic-response open-loop resonator filter is achieved through similarity transformation of the coupling matrix. To verify the proposed method, a compact four-pole elliptic-response bandpass filter is designed using the conventional structure with open-loop resonators. Designed filter has the resonators with very narrow spacing for the required coupling coefficient and it is impossible to implement a filter with wider fractional bandwidth. Two possible configurations to overcome this problem are presented through similarity transformation of the coupling matrix. From this design flexibility, a filter with wider fractional bandwidth is designed with realizable design parameters.     

A high quality factor photonic crystal channel-drop filter with a linear gradient microcavity

We design a channel-drop filter (CDF) with a linear gradient microcavity in a two-dimensional (2D) photonic crystal (PC). The model of three-port CDF with reflector is used to achieve high quality factor (Q-factor) and 100% channel-drop efficiency. The research indicates that adjusting the distance between reference plane and reflector can simultaneously influence the Q-factor due to coupling to a bus waveguide and the phase retardation occurring in the round trip between a microcavity and a reflector. The calculation results of 2D finite-difference time-domain (FDTD) method show that the designed filter can achieve the drop efficiency of 96.7% and ultra-high Q-factor with an ultra-small modal volume.     

Nonuniform Waveguide High-Pass Filters with Extremely Steep Cutoff

The design of a tapered waveguide high-pass filter with very steep cutoff characteristics near the cutoff frequency and very low reflections for frequencies beyond the cutoff is studied on the basis of nonuniform or inhomogeneous transmission line theory. The complex input reflection coefficient due to the presence of a section of nonuniform waveguide is obtained through a new approach by formulating the problem in terms of a pair of coupled differential equations of forward wave and reflected wave with varying propagation constants and nonuniform coupling coefficients. The solution of the reflection coefficient appears in the form of an infinite series of integrals and can be reduced, for the case of very gentle tapering to the simple form of fourier integral previously obtained by others. The general solution thus obtained is valid even if 1) the tapering along the waveguide is not gradual, and 2) the tapered section is terminated in an arbitrary impedance. It is shown that among many illustrated simple trial functions of impedance variation along the taper, the exponential function raised to cosine square yields reflection characteristics with the steepest rise near the cutoff and the lowest reflections for all frequencies beyond the cutoff. The steep rise near cutoff frequency is phenomenal, since, for example, at the nominal cutoff of 55 kMc the reflection reduces to about -50 db within 0.18 kMc, i.e., the transition region from the stop band to pass band at -50 db reflection is only about 0.33 per cent of cutoff. The same design procedure for the high-pass filter can be used for waveguide transitions of extremely wide band and very low reflections.     

基于非谐振节点的盒型拓扑结构基片集成波导滤波器设计

针对微波带通滤波器小型化、高性能的应用需求,提出使用单模和双模基片集成波导谐振器相结合设计广义切比雪夫带通滤波器.该结构可实现盒型拓扑结构,并且双模基片集成波导谐振器中的主模TE₁₀₁作为非谐振节点提供一条额外的交叉耦合路径,并能增加一个有限的传输零点;该结构不需要传统负耦合结构就能实现两个有限传输零点,并且该传输零点可以位于通带上方或下方,具有设计灵活的特点.为了进一步提高滤波器的选择性,研究了在四阶滤波器上蚀刻互补开环谐振器设计拓展的盒型拓扑结构滤波器,并实现五阶滤波功能三个有限传输零点.为了验证结构的合理性,设计了两款中心频率为10GHz的对称和非对称响应的四阶滤波器、一款中心频率为5.8GHz的五阶滤波器,并给出相应的含非谐振节点的盒型拓扑结构耦合矩阵进行验证,最后进行加工和测试.耦合矩阵响应、仿真和测试结果一致性较好,表明了该结构设计高性能滤波器的可行性.     

Modeling ferrimagnetic resonators

The impedance matrix for an arbitrary n-port ferrimagnetic resonator is derived by applying Poynting's theorem to a region of space surrounding the resonator. Simplifications to the impedance matrix for low-loss (Q>≈100) ferrite material make it possible to obtain an equivalent circuit model for the resonator, which can be used with most computer-based circuit simulation programs. The circuit model for the general-case polymodal ferrimagnetic resonator consists of a network of single-pole resonators, each of which has a possible non-frequency-dependent, nonreciprocal phase shift. The components of the circuit model are described in terms of the properties of the ferrite material, and the coupling strength of the microwave circuit to the magnetostatic modes of the ferrimagnet. The method is demonstrated in three simple examples, including a one- and two-port loop coupled filter, and a ferrimagnet in a waveguide     

超宽带带通滤波器设计与实现

通过对传统滤波器预畸设计法进行改进,得到一种新型的带通滤波器设计公式,它克服了在采用电容耦合或电感耦合带宽过窄及线性相位的问题.使用此方法设计了一个超宽带线性相位带通滤波器,并通过实验仿真证明其可行性.     

声光可调谐滤波器（AOTF）之模分离器的研究及设计

声光可调谐滤波器的设计关键是它的各个模块,包括光波导、模分离器、声波导和叉指换能器的参数设计。采用BPM方法计算了模分离器中对称模和非对称模的相位差,得到了TE模具有100%的转换率,而TM模的转换率为0时所对应的中央耦合部分长度Lc和分叉角θ之间的关系曲线。从该曲线可以得到同时满足TE模叉通和TM模直通条件的Lc和θ。最后,再次利用BPM这一工具,对所设计的模分离器进行了性能分析。     

Ku波段交叉耦合波导滤波器的精确设计

针对软件优化法设计交叉耦合波导滤波器的耗时性,利用矩形波导设计了Ku波段折叠型交叉耦合滤波器。采用S参数的多项式综合和矩阵消零的方法提取耦合矩阵,设计过程将全波建模和电路模型分析相结合,利用微波CAD软件HFSS分步骤对每个谐振单元及耦合结构进行仿真,以确定其尺寸,避免了对滤波器的软件优化,所得仿真结果与理论值吻合较好。     

基于L型槽结构的小型化SIW滤波器

为了解决传统基片集成波导(SIW)滤波器在通信电路中占用空间较大的问题,提出一种新型的开槽方法实现了小型化SIW滤波器.通过在四分之一模基片集成波导(QMSIW)谐振腔的顶层金属板上蚀刻L型谐振槽,利用开槽扰动的模移技术原理,使QMSIW腔的谐振基模被移动到低频处.基于此,设计了一款中心频率为2.6 GHz,相对带宽为...