双波段射频功率放大器理论与设计

提出了一种新型的双频阻抗变换器结构,该阻抗变换器采用T 型与装型结构相结合的方式,经理论推导和仿真优化,设计的双频阻抗变换器可实现任意两个频率上的任意两个不同复数阻抗到实数阻抗的变换。采用双频偏置电路,实现了在两个工作频率下的扼流,最终设计了一款可同时应用于TD-LTE 和GSM 网络的双波段射频功率放大器。相比于其它的多模多频带功率放大器,该双频阻抗变换器理论推导过程简单,容易实现,并可实现68%以上的功率附加效率,同时具有高输出增益和高平坦度的特点,整体电路结构简单。     

一种基于MBE的快速基音搜索算法研究

多带激励声码器(MBE)是目前理想的语音编码方案之一，他的核心参数是基音周期，分析过程采用ABS方法，提高了语音参数提取的准确性，可在噪声环境中合成出自然度和可懂度很高的语音。针对其基音搜索算法计算量过大的缺点，首先提出了一种新颖的中心偏离函数计算法，该方法先对原始语音进行傅里叶变换得到原始语音谱，再针对各个基音候选值确定其相应于原始语音谱的予带划分，通过对比每个划分的中心偏离量，可以确定最佳基音周期；其次设计了一种简单有效的倍频消除算法，通过简单的循环计算，可以消除倍频现象；仿真结果表明，这两种方法的结合不仅大大降低了原算法的计算量，而且保持了他精度高的优点。     

Figure of merit for narrowband,wideband and multiband LNAs

In software defined radio, the same radio front end is used to accommodate different wireless standards operating in different frequency bands. The use of wideband or multiband low noise amplifiers (LNAs) is mandatory in such situations. There are several figures of merit (FoMs) proposed for narrowband LNAs. These FoMs are modified for wideband/multiband LNAs just by the inclusion of 3?dB bandwidth, and designers tend to use the one that favours their own design. In this article, a review of the existing FoMs for narrowband LNAs is presented. Based on this analysis, we propose two different FoMs for fair comparison of improvement in LNA parameters due to complementary metal oxide semiconductor (CMOS) technology advancement and circuit optimisation (irrespective of transistor technology), separately. The empirical technology scaling factor for gain, noise figure (NF), f _T and linearity is used to differentiate between these FoMs for different types of LNAs.     

基于空时编码和优化多带复小波的MC-CDMA系统及性能

提出一种基于多带复小波和空时编码的多载波CDMA系统,研究了其在瑞利衰落信道下的误比特性能。理论分析和仿真结果表明该系统要明显优于通常MC-CDMA系统,具有与采用循环前缀(CP)的MC-CDMA相比较的优势,而且能够克服通常MC-CDMA系统插入CP所带来能量的减少和频谱效率的降低。同时空时编码技术的应用,显著增强了系统抗多径干扰和多址干扰的能力,进一步提高了系统性能。     

一种应用于车载通信的多频段全向天线

文中设计了一种应用于车载通信的多频段全向天线。该天线由印制于FR4 介质基板正反两面的金 属贴片组成,通过在主辐射贴片上端加载弯折枝节、在侧边加载边缘谐振单元、在背面加载电耦合电感电容(ELC)谐 振单元实现了其多频段特性;在主辐射贴片上蚀刻C 形槽拓宽了天线的中频带宽;天线的尺寸为58 mm×42 mm× 1. 6 mm。测试结果表明:S11≤-10 dB 的阻抗带宽为0. 82~0. 96 GHz、1. 7~2. 69 GHz、3. 34~3. 66 GHz、4. 81~4. 97 GHz, 覆盖了2G、3G、4G、5G 等频段。该天线具有小尺寸、宽频带以及全向性好等优点,可以应用于车载通信或其它移动 通信场景。     

超宽带太赫兹调频连续波成像技术

太赫兹调频连续波成像技术具有高功率、小型化、低成本、三维成像等特点,在太赫兹无损检测领域受到了广泛关注。然而由于微波及太赫兹器件限制,太赫兹信号带宽难以做大,从而制约了成像的距离向分辨力。虽然高载频可实现较大宽带,但伴随的低穿透性和低功率会限制太赫兹调频连续波成像系统的应用场景。因此,聚焦于太赫兹波无损检测领域,提出一种时分频分复用的114～500 GHz超宽带太赫兹信号的产生方式,基于多频段共孔径准光设计,实现超带宽信号的共孔径,频率可扩展至1.1 THz。提出一种频段融合算法,实现了超宽带信号的有效融合,距离分辨力提升至460μm,通过人工设计的多层复合材料验证了系统及算法的有效性,并得到封装集成电路(IC)芯片的高分辨三维成像结果。     

A novel linear and planar multiband fractal-shaped antenna arrays with low sidelobes

Fractal antenna arrays are usually used to tune multiband frequencies. However, these types of iteratively constructed antennas are associated with undesirable high sidelobe levels and low directivities. In this paper, an optimization procedure based on the genetic algorithm is used to find the optimal weights of the array elements such that the corresponding array patterns have low sidelobe levels and good directivity. Moreover, the fractal nature in the proposed arrays is maintained regardless of the optimized weights. Thus, the proposed fractal-shaped array maintains its capability in performing multiband frequency operation. These good radiation features make the proposed fractal-shaped array more appropriate for the current and future wireless communication applications. Simulation results confirm the superiority of the presented linear and planar fractal-shaped array structures with compared to the conventional fractal cantor linear array and the standard Sierpinski carpet planar array. For the proposed fractal cantor linear array, the sidelobe level has been reduced to more than −20 dB at different operating frequencies, and the directivity has been improved by more than 8 dB, while the modified Sierpinski carpet planar array has achieved −30 dB depressions in the sidelobe level and 6 dB improvement in the directivity.     

Reverse-Link Capacity of Multiband Overlaid DS-CDMA Systems

In the future deployment of wideband DS-CDMA mobile communication systems, spectrum overlay among sub-bands with different bandwidths is probably inevitable. In this paper we present an approach to estimate the reverse-link capacity of overlaid multiband DS-CDMA systems in terms of the maximum number of users in each sub-band. We will derive the general capacity formula, and present a decomposition method for the capacity analysis to reduce the computational complexity. Based on this decomposition method the conditions for maximum bandwidth utilization are obtained. These results are then extended to account for realistic constraints such as the maximum received power and imperfect power control.     

多频带信号压缩采样的回溯SOMP重构方法

针对多频带信号在调制宽带转换器（Modulated Wideband Converter,MWC）系统下的压缩采样,提出了一种基于回溯思想的多频带信号SOMP（Simultaneous Orthogonal Matching Pursuit）重构算法,该方法利用回溯思想和最小均方准则进行信号支撑频带搜索,从而重构源信号。相比传统方法,该算法不需要已知信号载频信息,且算法复杂度低,正确重构概率高。通过对实际中不同多频带信号MWC采样系统下的仿真实验表明,该方法具有良好的适用性。     

Small Internal Antenna Using Multiband,Wideband, and High‐Isolation MIMO Techniques

In this paper, a small internal antenna for a mobile handset is presented using multiband, wideband, and high‐isolation multiple‐input multiple‐output techniques. The proposed antenna consists of three planar inverted‐F antennas (PIFAs) that operate in the global system for mobile communication (GSM900), the digital communication system (DCS), the personal communication system (PCS), the universal mobile telecommunication system (UMTS), and wireless local area network (WLAN) bands with a physical size of 40 mm × 10 mm × 10 mm. A resonator attached to the folded PIFA creates dual resonances, achieving a wide bandwidth of approximately 460 MHz, covering the DCS, PCS, and UMTS bands; a meander shorting line is used to improve impedance matching. Additionally, a modified neutralization link is embedded between diversity antennas to enhance isolation, which results in a 6‐dB improvement in the isolation and less than 0.1 in the envelope correlation coefficient evaluated from the far‐field radiation patterns. Simulation and measurements demonstrate very similar results for S‐parameters and radiation patterns. Peak gains show 3.73 dBi, 3.77 dBi, 3.28 dBi, 2.15 dBi, and 5.86 dBi, and antenna efficiencies show 56.15%, 72.15%, 68.59%, 52.92%, and 82.93% for GSM900, DCS, PCS, UMTS, and WLAN bands, respectively.