Fiber wavelet filters [and planar waveguide couplers for full-wavelength demultiplexers]

The passive optical networks proposed by Marhic and Siegman to evaluate the discrete Fourier transform (DFT) of a linear array or a pixellated image (parallel input) are redesigned for the discrete wavelet transform or the wavelet packet (WP) decomposition. Using only asymmetric optical couplers, with a suitable power coupling ratio, it is shown that it is possible to optically implement Mallat's pyramidal decomposition scheme with a compactly supported wavelet basis function. The case of a serial input has a larger number of potential applications to optical communications systems or optical computing, and simple passive optical networks are presented that evaluate the DFT or the wavelet transform of a stream of optical digits, by using only Mach-Zehnder interferometers with output asymmetric couplers. In particular, an all-optical implementation of the WP-division demultiplexer for a waveform coded transmission system is given. The proposed networks are full-wavelength demultiplexers, as they split the spectrum of the incoming signal into a set of closed frequency channels; the filters have identical bandwidth and span the whole input spectrum. Using the WP-decomposition method, different subband filtering schemes can be designed, fabricating trees of quadrature mirror filters with the fiber or the integrated optics technology.     

平面左手结构色散与传播特性分析

采用时域有限差分方法研究了一种新型平面结构阵列在左手频带内的后向波传播特性与负折射特性,提出分析二维平面左手结构的新方法:基于单元结构的四端口网络参数进行Bloch分析,得出色散关系和Bloch阻抗;根据色散关系和Bloch阻抗分析相位与能量传播方向的关系,以确定出左右手特性频带.相比于以往单元结构分析方法,本文方法利于单元结构的灵活设计,能较好地考虑分布参数元件色散特性,能简便准确地判断出左右手特性频带,且能用于分析各向异性和有损耗结构.仿真分析结果验证了方法的有效性.     

Systematic design of superprism-based photonic crystal demultiplexers

In this paper, design of photonic crystal demultiplexers based on superprism effect is discussed. Figures of merit for performance of these demultiplexers are defined and a systematic design procedure is presented. We consider different design schemes, based on equal angular separation between channels and equal frequency separation between channels, and find the optimum structures among conventional photonic crystal lattices for each case. Our results provide design solutions for a range of current applications.     

集总参数电磁人工超材料在无线能量传输中的应用

文章在磁共振式无线能量传输系统的基础上,应用磁单负特异材料,设计出一种能够实现磁场聚焦的特异材料平板透镜,并将其应用到谐振式无线能量传输系统之中提高传输效率。     

渐变表面左手介质表面波天线散射特性分析

利用严格的模匹配与多模网络相结合的方法以及阶梯近似和阻抗转移技术分析了不同渐变曲线形状的左手介质表面波天线的反射与辐射特性,着重研究了不同渐变形状对天线反射与辐射特性的影响.从电磁波散射的角度将辐射问题转化为表面波和空间波的传输问题,从而使分析过程得到了极大的简化.分析表明左手介质表面波天线的辐射特性与传统右手情形有很多不同,说明了产生这种不同的原因.所给出的计算结果对左手介质表面波天线的设计有实际参考意义.     

Dispersion characteristics of planar multilayer dielectric structures

Shifts in frequency of the dispersion characteristics of orthogonally polarized modes propagating in planar dielectric structures containing a wave-guiding substrate and layers of low-loss dielectric film are calculated. The influence of the geometric and real-valued parameters of thin semiconductor films located on the surfaces of the substrate or between two substrates on the mode’s phase shifts is studied.     

Impedance characteristics of EMC triangular planar monopoles

The impedance characteristics of triangular planar monopoles, electromagnetically coupled with a probe-driven strip, are investigated experimentally. The 2:1 voltage standing wave ratio bandwidths of up to 50% are obtained     

Impedance characteristics of planar bow-tie-like monopole antennas

The impedance characteristics of planar bow-tie-like monopole antennas have been studied experimentally. The planar bow-tie-like monopole antenna achieves a broad bandwidth, typically of >75%. A modified formula is suggested to accurately evaluate the frequency corresponding to the lower edge of the impedance bandwidth     

Contactless energy transfer using planar printed circuit boardwindings

An energy transfer circuit is proposed which employs a pair of neighbouring printed circuit board windings as a contactless energy transfer device, thereby making it amenable to low-profile designs and suitable for applications in which stringent requirements for height, space and reliability have to be met     

Biaxial characteristics of planar proton exchanged lithium niobatewaveguides

Results of a theoretical and experimental study on proton exchanged lithium niobate (LiNbO₃) planar waveguides are presented. Experimental results are successfully explained by the theoretical model only if the guiding layer is assumed to be anisotropic with biaxial characteristics, this biaxiality being induced by the proton exchange process in the uniaxial lithium niobate substrate     

Frequency response characteristics of the multiport planar ellipticpatch

The Green's function for the elliptic patch is developed using differential operators. This method obtains the Green's function directly, without having to expand over the eigenvalues. The resulting series is highly convergent. From the Green's function, the impedance matrix is formulated for the elliptic patch. Experimental and theoretical results show good agreement     

Effects of crosstalk in demultiplexers for photonicanalog-to-digital converters

Time interleaving of samples digitized by a parallel array of analog-to-digital (A/D) converters provides a means of increasing the sampling rate beyond that possible with a single A/D converter. For time-interleaved photonic A/D converters, optical demultiplexers can be used to advantage. Both time-division and wavelength-division demultiplexers must yield low crosstalk between the parallel output channels in order to yield accurate A/D conversion. An analysis predicts the level and form of the resulting errors. The analytical results compare well with experiment     

Study of the dispersion characteristics of planar chiral lines

This paper analyzes the dispersion characteristics of the fundamental modes of some basic chiral planar transmission lines: microstrip, slot-line, coplanar waveguide (CPW), and a coupled microstrip line, including the possible frequency dependence of the chiral parameters. The dispersion characteristics are computed after finding the zeros of the determinantal equation resulting from the application of the Galerkin method in the spectral domain. Because of the biisotropic nature of the substrate, a 4×4 matrix differential equation has been solved to obtain the spectral dyadic Green's function (SDGF). This function is explicitly obtained in terms of a closed-form 4×4 transition matrix that relates the transverse electromagnetic fields at the upper and lower interface of the chiral substrate. This fact is key to developing fast computer codes since it avoids numerical matrix exponentiations. The numerical results have shown that the chiral nature of the substrate basically adds an additional parameter to control the propagation characteristics of the analyzed lines and, in general, makes the lines more dispersive, showing even resonant-like behavior     

Modal characteristics of bent dual mode planar optical waveguides

Modal characteristics of bent dual-mode planar optical waveguides are obtained. The bending-induced changes in the modal power distribution is found to be quite different for the two modes. Surprisingly, unlike the fundamental mode, bending causes the fractional modal power for the second mode to increase in the inner core-half and to decrease in the outer core-half of the waveguide. Interestingly, this leads to a decrease in effective index of the second mode due to bending at sufficiently high V-values     

Near-field shielding and reflection characteristics of anisotropiclaminated planar composites

A theoretical model is proposed to study the near-field shielding and reflection characteristics of anisotropic laminated planar composites. Specifically, the plane-wave spectral representation is used to express the dipole field and the wave-transmission matrix technique is employed to deal with the transmitted and reflected fields. In this study, numerical results for graphite/epoxy (G/E) and boron/epoxy (B/E) composites are presented to discuss, in detail, the effects of varying the observation distance, number of layers, lamina thickness, fiber conductivity, and fiber orientation pattern. Comparison with the measured results and the previous published ones are also included to confirm the accuracy of this proposed model     

Development of the 75-GHz planar gyrotron with transverse energy extraction

The opportunity of generating ribbon-shaped polyhelical electron beams intended to excite oscillations in the new type of gyrotrons is investigated via particle-in-cell simulation. Its distinctive features are the planar geometry of an interaction space and transverse energy extraction (with respect to the direction of translational motion of a helical electron beam). The electrode configuration has been found in the gyrotron with an operating frequency 75 GHz, where the formed electron beam has a velocity spread of ～10%, the rotational energy fraction is 50%, and the beam profile is weakly distorted. When the voltage is 12 kV and the beam current is 1 A, the electron beam under study is demonstrated to excite the single-mode generation with an efficiency of up to 15% in the gyrotron’s operating space produced by the planar waveguide.     

激光辐照下光电电池的极限能量转化效率研究

采用激光输能技术解决临近空间飞行器的能源供给问题的研究正在广泛开展。为研究激光辐照下的光电电池的极限性能,基于细致平衡理论,分析了激光辐照条件下光电材料禁带宽度与最佳激光波长的关系,得到了光电电池各类输出性能参数的计算方法。通过计算,得到了激光波长、激光功率密度和电池温度对能量转化效率等参数的影响规律。结果表明对于特定材料的光电电池存在最佳的激光波长使其获得极限能量转化效率;激光功率密度的增加可以提高光电电池的能量转化效率,但达到一定数值后提高不再明显;对于电池温度的影响,不同的输出性能参数具有不同的温度系数。     

Cavity coupling structure for planar oscillators showing DR-likereflective characteristics

A new cavity coupling structure has been developed for low-phase noise oscillator applications. Unlike the conventional cavity coupling structures that show absorption at the resonant frequency, the new structure shows high reflection at resonance similar to dielectric resonators, making it suitable for the reflective oscillators. The fabricated cavity resonator showed a loaded Q-factor of 1200 and the X-band oscillator using the new resonator showed phase noise proper-ties of -57 and -83 dBc/Hz at 1 and 10 kHz offset, respectively. This is comparable to the best results of dielectric resonator oscillators using HEMTs at this frequency range     

Chromium etching characteristics using a planar type plasma reactor

The dry etching characteristics of Cr film in the CCl₄/O₂ mixed gas plasma have been investigated with a variety of etching parameters in the planar type reactor with the 13.56 MHz rf power. Moreover the dry etching resistance of EB resists and variation of the feature size on a 12.5 and 15 cm Cr-Mask are described. The etch rate of Cr film depends strongly on the etchant gas composition ratio, the electrode separation and the electrode surface materials. In the cathode coupling mode with a gas pressure of 0.2 Torr, a gas flow rate of CCl₄/O₂ of 0.5, electrode separation of 80 mm and rf power density of 0.38 W/cm², the following results are obtained: (1) The etch rate of Cr film is about 30 nm/min, Paper presented partially at 23rd Annual Electronic Materials Conference, University of California, Santa Barbara, California, June 24, 1981.