Unidirectionality in dispersive SAW transducers

Low loss SAW filters can be built making use of unidirectionality and selfmatching of dispersive transducers. The origin of unidirectionality lies in internal reflections between electrodes. The calculated loss level may be as low as 0.08 dB in down chirp double dispersive IDT filters     

Narrow-aperture chirp transducers for SAW convolvers

Narrow-aperture SAW beams can be generated efficiently using chirp transducers, thus avoiding the need for beam compression in convolvers. The transducers can be designed such as to compensate for phase errors due to dispersive SAW propagation. Experimental confirmation was obtained using convolvers with 120 MHz bandwidth and 16 ?s interaction length, and a bilinearity factor of ?65 dBm was achieved.     

Applications of edge-bonded transducers to SAW components

Various applications of the EBT to acoustic devices are reported. First we describe the operation of these transducers in the case of Rayleigh waves. Then we report the results we have obtained in the fabrication of: 1) a piezo-MOSFET programmable filter with a bit rate reaching 50 MHz; 2) a Love wave-dispersive delay line with a 240 compression ratio; 3) a fused silica reflective array compressor exhibiting a 30-µs dispersion over a 60-MHz bandwidth around 100 MHz and a 24-dB total insertion loss.     

Narrow-aperture SAW filter with both transducers finger-length-weighted

A 2.5 ?-aperture SAW filter has been designed and tested. The single-mode nature of the waveguiding filter allows finger-length-weighting to be distributed between input and output transducers according to a simple procedure. The resulting filter has a stopband rejection in excess of 50 dB.     

High-performance SAW convolver using 3-phase unidirectional transducers

The development of a new SAW convolver with a bandwidth 45 MHz, interaction time 12 ?s and which employs 3-phase unidirectional transducers is discussed. The resulting device has high efficiency (?58 dBm) and displays good self-convolution suppression. Only single-stage fabrication is required.     

Low-loss low-ripple SAW filters using three bidirectional centrosymmetric transducers

Low-loss, low-ripple and high out-of-band rejection SAW filters have been constructed using a three transducer configuration with symmetric/antisymmetric end transducers. The filter on 128°-cut LiNbO3 has an insertion loss of 5.2 dB, a passband ripple of 0.3 dB (peak to peak) and an out-of-band rejection of 55 dB.     

Combination of generalized admittance matrices in the form of poleexpansions

This paper describes a novel algorithm for the determination of the wide-band mathematical model of a waveguide component, segmented into elementary blocks of known characteristics. Starting from the Y-matrices of the blocks, given in the form of pole expansions in the frequency domain, the algorithm yields the overall Y-matrix in the same form. Therefore, it can be applied iteratively to find the pole expansion of the Y-matrix of larger and larger waveguide structures. The algorithm is particularly useful if the Y-matrix of the blocks are obtained by the boundary-integral-resonant-mode-expansion (BI-RME) method, which yields the Y-parameters just in the desired form. Two examples show that the joint use of the BI-RME method and of the algorithm described in this paper results in a very accurate and fast numerical code, well-suited for the wide-band modeling of complex waveguide structures     

Scattering and transmission matrices of an inhomogeneous layer

Numerical algorithms for determining the elements of the transmission matrix of an inhomogeneous magnetodielectric layer based on the integration by the expansion method are proposed. A method of successive smooth disturbances for solving the problem of diffraction by an inhomogeneous layer whose permittivity depends on the field amplitude is proposed. For simple cases, explicit forms of matrices and numerical results for a quasi-periodic structure are given.     

声表面波器件中非同步区域体波散射的抑制

用有限元/边界元法(FEM/BEM)研究了表面波器件中非同步区域中体波散射引起的损耗。以典型的hiccup单端对谐振器作参考结构,用结构参数缓慢变化的间隙取代其中间的自由间隙。研究发现,改变间隙参数可在保持谐振频率不变的同时,提高谐振器的品质因数值。对分布间隙和风琴间隙两种间隙结构进行对比,结果表明,前者优于后者。将传统DMS滤波器中的金属化间隙以分布间隙取代,可找到一个优化的分布间隙结构,使插损提高0.3 dB。     

On the properties of the product of the impedance and admittance matrices of three-conductor transmission lines

The purpose of this letter is to show that the product of the impedance and admittance matrices of three-conductor transmission lines is never in the form [aa,b0] or [aa,0b] when s = jω The significance of this result is discussed.     

1.03 GHz operation of a low-loss SAW filter using 3-phase unidirectional transducers with thin dielectric layered feed electrodes

Successful working of a 3-phase unidirectional transducer (TPUDT) SAW filter at 1.03 GHz, without using any airgap crossovers, is reported in the letter. A thin-film capacitance existing between the feed electrodes of the transducers is used to advantage, as an essential element of the required phaseshifting network. The minimum insertion loss is found to be 2.0 dB. The filter is believed to have wide applications in the present and future communication systems requiring low-loss bandpass filtering.     

Small-signal admittance of BARITT diodes

Small-signal admittance and phasor diagrams for metal-semiconductor-metal microwave oscillator diodes (BARITT diodes) were calculated by taking previously neglected carrier diffusion and field dependence of carrier velocity into account. It was shown that the microwave performance greatly degrades with an increase of dc current density and of oscillation frequency.     

Interdigital sensors and transducers

This review paper focuses on interdigital electrodes-a geometric structure encountered in a wide variety of sensor and transducer designs. Physical and chemical principles behind the operation of these devices vary so much across different fields of science and technology that the common features present in all devices are often overlooked. This paper attempts to bring under one umbrella capacitive, inductive, dielectric, piezoacoustic, chemical, biological, and microelectromechanical interdigital sensors and transducers. The paper also provides historical perspective, discusses fabrication techniques, modeling of sensor parameters, application examples, and directions of future research.     

Generalized admittance matrix models of OTRAs and COAs

This paper proposes new admittance matrix models to approach the behavior of fully-differential Operational Transresistance Amplifiers (OTRAs) and Current Operational Amplifiers (COAs). The infinity-variables method is used in order to derive the new generalized models. As a consequence, standard nodal analysis being improved to compute fully-symbolic small-signal characteristics of fully-differential analog circuits.     

Calculation of p-type GaAs IMPATT admittance

The unequal ionization rates reported for holes and electrons in GaAs have been used to calculate the small-signal admittance for a complimentary p-type IMPATT diode. For the uniformly doped n and p device structures considered, the p-type structure is found to have significantly increased negative conductance.     

Small-signal admittance of a Gunn-effect device

A small-signal equivalent circuit of a Gunn-effect device is deduced from a simple model. Preliminary measurements substantiate this equivalent circuit. The results are used to calculate the small-signal admittance of a 1?cm GaAs Gunn-effect device at 10 Gc/s.     

声表面波的衍射分析

从声表面波(SAW)满足的标量波动方程出发,根据傅里叶变换分析了各向异性晶体中SAW衍射场分布,在此基础上利用数值积分的方法计算出了衍射场分布的理论曲线。实验上进行了验证,二者分布基本一致。