Multilayer resonators and a bandpass filter fabricated from a novel low-temperature co-fired ceramic

The main objective of this study was to make components from a novel low-loss, low-temperature Co-fired ceramic (LTCC) dielectric, which was also compatible with a high-conductivity silver paste. The multilayer-component fabrication procedure is presented together with a composition for a tape-casting slurry, choice of conductor paste, and LTCC process parameters. A good Q factor, >100 at 2 GHz, using the novel material system has been achieved for λ/2 resonators operating in the frequency range 1.7–3.7 GHz. An excellent frequency response for a 2 GHz bandpass filter has also been achieved; the insertion losses in the passband were less than −2 dB (bandwidth 60 MHz) and the attenuation more than 25 dB in the stopband located 190 MHz higher.     

Quantification of the 3D microstructure of SC surfaces

This study presents the development of an ImageJ plugin for surface characterization. Based on gradient analysis, parameters, such as the gradient magnitude, orientation, mean resultant vector and surface area are derived. A comparative study of supercalendered (SC) papers was performed to verify the surface representations yielded by a laser profilometer. The surface representations of samples covered with carbon and gold were compared to untreated samples. The results confirm the suitability of gold coating for reducing the artefacts encountered on laser profilometry surface representations of paper. In addition, a complete scanning electron microscopy analysis is performed on the assessed samples to quantify the surface fraction covered by mineral fillers and to reveal the true 3D microstructure of SC surfaces. The influence of filler coverage and filler type on the gloss level of commercial SC papers is evaluated. The relationship between the surface topography, gloss and PPS roughness for a series of commercial SC papers is established.     

Optimal transmissions for space-time coded OFDM UWB systems

1 Introduction Recently, the high rate short range wireless personal area network (WPAN) is considered. When the inverse of the sampling rate is significantly shorter than the total delay spread, as is the case for most UWB communication systems, OFDM systems are more attractive than a single-carrier system. The multi-band OFDM physical layer proposal has been adopt by IEEE 802.15.3a Task Group[1]。 Combing STC and OFDM have the properties to achieve high data rate and mitigate int…     

一种新型超宽带单极子缝隙天线设计与仿真

提出了一种新型超宽带单极子缝隙天线,该天线包含一个类似于单极子天线的缝隙和叉状共面波导馈电结构,蚀刻在FR4-PCB板上,尺寸为26 mm×26 mm×1.4 mm。该天线采用HFSS13.0软件进行仿真,并对天线模型参数进行优化。结果表明:该天线具有良好的阻抗匹配和方向图特性,频带宽度为2.53~19.30 GHz(S11≤–10 d B),相对带宽达到154%,满足超宽带天线要求。     

多用户全光超宽带射频信号发生器设计

在研究能加倍提高数据传输速率的混合调制技术基础上,提出了可重构多用户超宽带射频信号产生方案,灵活地产生一至四阶的高斯导数型的超宽带射频信号,该信号波长稳定、可调范围大、频率啁啾较低、色散容忍度高,无色散补偿情况下在单模光纤中传输75km后波形失真很小。     

吸收型准高斯带通滤波器的研制

在数字及高速率信号传输系统中,经常采用Bessel或Gaussian函数滤波器,该类滤波器只有在中心频率(带通滤波器)或DC处(低通滤波器)才有良好的匹配特性,在其他频点都有很大的反射,在微波电路的级联中会产生杂波和干扰。为了解决该问题,设计了一种在通带和阻带内都有很小反射的滤波器,即吸收型(匹配型)准高斯类带通滤波器。介绍了其设计过程及方法,并设计了一种中心频率为100 MHz的吸收型准高斯带通滤波器,给出了仿真结果和实测曲线,实测结果与仿真结果吻合得很好。     

基于多采样率的频域倍频程研究

传统倍频程分析采用带通滤波器组算法实现,带通滤波器组算法仅能满足国家标准要求,并且用于分析分数阶倍频程时,滤波器组的数量及计算量成倍增长。提出了一种基于多采样率在频域分析倍频程及分数阶倍频程的算法。该算法首先对信号按通道重采样,并利用FFT转换到频域计算信号的倍频程及分数阶倍频程谱。仿真验证了算法的正确性,并与带通滤波器组算法做了比较。仿真及对比结果表明,相比于带通滤波器组算法,该算法能提供更好的谱分辨率,并且对于分数阶倍频程,该算法计算量明显少于滤波器组算法计算量。     

基于锁相环的Chirp超宽带信号源的设计与实现

在传统的模拟法产生Chirp超宽带信号的基础上,提出了一种基于锁相环（PLL）法的Chirp超宽带信号源设计方案。与传统的模拟方法相比,该方法产生的Chirp超宽带信号载频稳定性高,能够达到参考信号的频率稳定度。从理论上分析了该方法的可行性,并用相应的硬件电路实现了基于PLL的Chirp超宽带信号源。实验结果表明,该方法设计出的Chirp超宽带信号源具有易实现,稳定度高,灵活性和实用性强等优点。     

接地金属化孔对交指带通滤波器频响的影响分析

用微带线结构实现有接地端的交指带通滤波器时,接地金属化孔的寄生电感效应将影响带通滤波器的幅频特性。寄生电感的大小可由经验公式近似计算,借助于三维电磁场仿真软件,可以计算出当接地金属化孔的排列方式不同时,由寄生电感引起的带通滤波器中心频率偏移量也不同。接地金属化孔排列引起的寄生电感越小,带通滤波器的中心频率越接近于理论值,因此在设计有接地金属化孔的交指带通滤波器时,需根据所选用的金属化孔排列结构修正滤波器中心频率的偏移。     

一种适用于中频接收机的具有75dB动态范围的100MHz带通$\Sigma \Delta$调制器

本文介绍了一款适用于中频接收机的四阶开关电容带通$\Sigma \Delta$调制器,采样频率为100MHz。为优化谐振器的性能,文中提出了考虑运算放大器非理想特性后谐振器的传输函数。本文设计的调制器采用0.13-um标准CMOS工艺,在25MHz附近200KHz信号带宽内测得的SNDR和DR分别为68dB和75dB。调制器工作在1.2V电源电压下,总功耗为8.2mW。