高速PCB插损影响因子研究

随着高速电路的传输速率不断提升,电子产品不断微小化、精密化、高速化,使得电路的集成度越来越高。PCB不仅要完成各种原器件的线路连接,更要考虑高密高速带来的信号完整性问题。高速互连中首要的信号完整性问题是传输线损耗,损耗会引起信号上升沿的退化和幅度的衰减,导致严重的信号失真。通过各种仿真软件虽然能够仿真出各影响因子对损耗的理论影响趋势,但实际生产中往往与仿真结果存在一定偏差。文章仅针对参考层厚度、线宽、线距、PCB排版时图形旋转角度及背钻Stub长度对插入损耗的影响进行实验研究,并得出较为准确的设计区间,为高速信号传输的选材及设计优化提供依据,使实际生产结果与理论模拟更为接近。

Fabrication and Numerical Simulation of a MicromachinedContact Cantilever RF-MEMS Switch

This paper reports a contact cantilever MEMS switch. The designed switch has a metal cantilever that acts as an electrostatically activated switch with processing options to achieve dielectric isolation of the controlvoltage path from the signal path. To obtain good material properties,an ANSYS FEA tool is used to optimize the structure. The RF MEMS switch is fabricated via a surface micromachining process. The switch has an actuation voltage of 12V,which is close to the simulated value of 11V. The measured and the HFSS simulated isolations are both higher than - 20dB from 0.05 to 10GHz. The measured insertion loss is less than - 0.9dB, relatively larger than the simulated loss of less than - 0.2dB from 0.05 to 10GHz. This is because a contact resistance introduced due to poor physical contact between the bottom lines and the metal cantilever.

A modulator using RF CMOS T-type attenuator for TH-UWB communications

The insertion loss （IL） of a T-type attenuator is theoretically analyzed. A T-type RF （ radio frequency） CMOS （ complementary metal-oxide-semiconductor ） attenuator is designed as an on-off keying（OOK） modulator in a time-hopping ultra wide-band （TH-UWB）communication with a carrier frequency of 4 GHz. In the topology of the OOK modulator circuit, there are three parts, an oscillator with an oscillating frequency of 4 GHz, a T-type attenuator constructed by RF CMOS transistors, and an output impedance matching network with a L-type LC structure. The modulator is controlled by a time-hopping pulse position modulation（TH-PPM） signal. The envelope of the modulated signal varies with the amplitude of the controlling signal. Meanwhile, an output matching network is also designed to match a 50 Ω load. In 0. 18 μm RF CMOS technology, a modulator is designed and simulated. The implemented modulator chip has 65 mV of the output amplitude at a 50 fl load from a 1.8 V supply, and the return loss （ S11 ） at the output port is less than - 10 dB. The chip size is 0. 7 mm × 0. 8 mm, and the power consumption is 12. 3 mW.

Acoustic Radiation of Damped Cylindrical Shell with Arbitrary Thickness in the Fluid Field

The insertion loss of acoustic radiation of damped cylindrical shell described by 3-D elasticity Navier equations under radial harmonic applied load in fluid is presented. The classical integral transform technique, potential theory and Lamè resolution are used to derive the solutions of Navier equations. The higher precision inversion computation is introduced to solve the linear equations. Comparing with acoustic radiation of one-layer cylindrical shell, the influence of thickness, mass density, dilatational wave loss factor and Young's modulus of damping material and circumferential mode number of the cylindrical shell on the insertion loss is concluded. The theoretical model in the paper can be used to deal with the arbitrary thickness and any frequency of the coated layer in dynamic problem. The conclusions may be of theoretical reference to the application of damping material to noise and vibration control of submarines and underwater pipes.

Design of a Polymer Directional Coupler Electro-Optic Switch with Low Push-Pull Switching Voltage at 1550nm

A polymer directional coupler （DC） electro-optic switch with push-pull electrodes and rib waveguides is designed based on the conformal transforming method, image method, coupled mode theory, and electro-optic modulation theory. Its structure and principle are described, the design and optimization are performed, and the characteristics are analyzed, including the coupling length, switching voltage, output power, insertion loss, and crosstalk. To realize normal switching function,the fabrication tolerance,wavelength shift, and coupling loss between a single mode fiber （SMF） and the waveguide are discussed. Simulation results show that the coupling length is 3082μm; the push-pull switching voltage is 2.14V;and the insertion loss and crosstalk are less than 1.14 and -30dB,respectively. The proposed analytical technique on waveguides and electrodes is proven to be accurate and computationally efficient when compared with the beam propa- gation method （BPM） and the experimental results.

Implementing single-scale wavelet transform processor with magnetostatic surface wave device

When the envelope of the conducting strips for the input transducer of magnetostatic surface wave(MSSW) device is designed according to the wavelet-function envelope,the impulse-response function of the input transducer for MSSW device is equal to the wavelet function,so that single-scale wavelet-transform processor of MSSW type is fabricated.First,according to the envelope function of the wavelet,the length function of the conducting strips is defined,then,the lengths of the conducting strips can be calculated from the length function of the conducting strips,finally,the input transducer can be designed according to the lengths and widths for the conducting strips.The compensation method of the insertion loss for single-scale wavelet trans-form processor of MSSW type is also given in the paper.When the output end of single-scale wavelet transform processor of MSSW type is connected to the amplifier,its insertion loss can be compensated.

Non-blocking four-port optical router based on thermooptic silicon microrings

By using silicon-on-insulator(SOI) platform, 12 channel waveguides, and four parallel-coupling one-microring resonator routing elements, a non-blocking four-port optical router is proposed. Structure design and optimization are performed on the routing elements at 1 550 nm. At drop state with a power consumption of 0 m W, the insertion loss of the drop port is less than 1.12 d B, and the crosstalk between the two output ports is less than-28 d B; at through state with a power consumption of 22 m W, the insertion loss of the through port is less than 0.45 d B, and the crosstalk between the two output ports is below-21 d B. Routing topology and function are demonstrated for the four-port optical router. The router can work at nine non-blocking routing states using the thermo-optic(TO) effect of silicon for tuning the resonance of each switching element. Detailed characterizations are presented, including output spectrum, insertion loss, and crosstalk. According to the analysis on all the data links of the router, the insertion loss is within the range of 0.13—3.36 d B, and the crosstalk is less than-19.46 d B. The router can meet the need of large-scale optical network-on-chip(ONo C).

An Interrogation System Based on Two Semiconductor Optical Amplifiers for Weak Fiber Bragg Gratings

An interrogation system based on two semiconductor optical amplifiers for weak fiber Bragg gratings （FBGs） was proposed. The first semiconductor optical amplifier （SOA） was used to modulate the light, and the second SOA separated the reflected signal from the different FBGs through delayed switching. The proposed system has lower insertion loss and higher spatial resolution, and can interrogate the time- and wavelength-division multiplexed FBG array. Up to 50 FBGs, with a reflectivity of 0.2% and a spatial resolution of 5 m along the optical fiber, were distinguished to demonstrate the interrogation system.