Investigation of circularly polarized loop antennas with a parasitic element for bandwidth enhancement

It is demonstrated that the bandwidth of circular polarization (CP) can be significantly increased when one more parasitic loop is added inside the original loop. A single-loop antenna has only one minimum axial ratio (AR) point while the two-loop antenna can create two minimum AR points. An appropriate combination of the two minimum AR points results in a significant enhancement for the CP bandwidth. A comprehensive study of the new type of broad-band circularly polarized antennas is presented. Several loop configurations, including a circular loop, a rhombic loop, and a dual rhombic loop with a series feed and a parallel feed, are investigated. The AR (/spl les/2 dB) bandwidth of the circular-loop antenna with a parasitic circular loop is found to be 20%, more than three times the AR bandwidth of a single loop. For the rhombic-loop antenna with a parasitic rhombic loop, an AR bandwidth (AR/spl les/2dB) of more than 40% can be achieved by changing the rhombus vertex angle. The AR (/spl les/2 dB) bandwidths of the series-fed and parallel-fed dual rhombic-loop antennas with a parasitic element are 30% and 50%, respectively. A broad-band balun is incorporated into the series-fed dual rhombic-loop antenna for impedance matching. The broad-band CP performance of the loop antennas is verified by experimental results.     

一种CPS馈电的宽带圆极化双菱环天线

提出了一种新型的双菱环形天线,通过在双菱环内添加寄生环来提高天线的圆极化带宽,每个环上槽口的位置决定天线的圆极化特性。双菱环和寄生双菱环分别在低频和高频处产生圆极化波,从而使天线的圆极化带宽增加,3 dB圆极化带宽达到了24.1%,在圆极化频带内增益为10 dB以上。为了测量天线性能,设计了共面带状线到微带线的转换巴伦,因为巴伦和天线在同一个平面内,所以对天线的性能产生了一点影响。     

Investigation of the parasitic loop counterpoise antenna

The radiation field produced by a parasitic loop counterpoise antenna is investigated. This is a new antenna configuration which consists of a small circular loop in the presence of a large parasitic loop and is placed above a circular ground plane or counterpoise. Geometrical theory of diffraction is applied to obtain the theoretical expressions for the far field produced by such an antenna. Within the range of approximation the agreement between theory and experiment has been found to be very good. The introduction of a parasitic loop, in general, reduces the ground plane edge diffraction effects on the far-field patterns and makes the overall pattern in the half-plane above the counterpoise less directional. Possible application of the antenna is also discussed.     

Effects of large parasitic loops on alford-loop counterpoise radiation patterns

The effects of large parasitic loop elements on the radiation patterns of an Alford loop above a circular ground plane are discussed. It has been found that, on properly choosing the parasitic loop parameters, it is possible to reduce the ground-plane edge-diffraction effects considerably without appreciable deterioration of the overall pattern.     

宽带高增益圆极化微带天线与阵列

设计了一副宽带高增益圆极化微带天线,并进行组阵分析。天线中心频率2.6 GHz,通过增加寄生贴片和空气层来提高天线单元的增益和带宽。上下两层介质板上边长不同的切角方形贴片分别激励一个低频与高频的圆极化模,有效地拓宽了轴比带宽。仿真结果表明,反射系数|S11|<-10 dB带宽21.8%,3 dB轴比带宽12.0%,中心频率点增益9.0 dBi。对天线单元进行加工测试,与仿真结果较为吻合。设计了2×4元阵列,并进行了仿真,增益提升至17.5 dBi,3 dB轴比带宽10.4%。     

A circularly polarized slot antenna for high gain applications

A coplanar waveguide fed slot antenna for wideband circular polarization is designed and experimentally validated. The rectangular slot is excited using a stepped feed line terminated on a circular disc shaped tuning stub. To obtain circular polarization, inverted L-shaped strips are attached to the ground plane at the opposite corners while a rectangular slit is cut in the circular disc. The combined bandwidth (3-dB axial ratio and 10 dB impedance matching) achieved is 48% (4.35–7.1 GHz) under simulation and 40% (4.75–7.1 GHz) in measurement. The gain of the antenna is next enhanced by the application of a double layered square loop frequency selective surface. The frequency selective surface is used as a reflector placed beneath the antenna at an optimum distance. An improvement of about 4 dB is seen in the measured peak gain over most of the operating band. Experimental results are presented to characterize the antenna and the frequency selective surface and they are found to be in good agreement with the simulated results.     

LED linearisation for video bandwidth transmission employing a monolithically integrated PIN-PD

Nonlinear distortion and frequency response for light-emitting diodes in analogue video transmission are greatly improved by using a wideband optoelectronic feedback loop employing monolithically integrated PIN photodiodes. Large monitoring efficiency of more than 2% makes it easy to realise this wideband and high-gain feedback loop.     

基于级联式偏置锁相环的低相噪宽带频率合成器*

为提高锁相环的相位噪声性能,本文设计了一种级联式偏置锁相环来实现宽带低相噪频率合成器,通过理论分析得到其相位噪声模型,证明了该技术能够有效地降低锁相环路中鉴相器的噪声基底,并且混频交互调产生的所有杂散可由环路滤波器抑制,从而将窄带高频谱纯度信号扩展为宽带高频谱纯度信号。基于该技术提出了2GHz ~5GHz 的低相噪宽带频率合成器方案,并对其相位噪声指标进行了分析。理论与实验结果表明,相比于传统的小数分频式锁相环方案,该方案的带内相位噪声有明显改善。     

Wideband and compact folded loop antenna

A simple and successful design method that yields a wideband and compact antenna without a ground plane is proposed. The antenna, referred to as the folded loop antenna, can, with the right parameters, achieve wideband characteristics. Calculated and measured results agree well and more than 50% bandwidth (return loss /spl les/-10 dB) is obtained.     

Passive parasitic UWB antenna capable of switched beam‐forming in the WLAN frequency band using an optimal reactance load algorithm

We propose a switched beam‐forming antenna that satisfies not only ultra‐wideband characteristics but also beam‐forming in the WLAN frequency band using an ultra‐wideband antenna and passive parasitic elements applying a broadband optimal reactance load algorithm. We design a power and phase estimation function and an error correction function by re‐analyzing and normalizing all the components of the parasitic array using control system engineering. The proposed antenna is compared with an antenna with a pin diode and reactance load value, respectively. The pin diode is located between the passive parasitic elements and ground plane. An antenna beam can be formed in eight directions according to the pin diode ON (reflector)/OFF (director) state. The antenna with a reactance load value achieves a better VSWR and gain than the antenna with a pin diode. We confirm that a beam is formed in eight directions owing to the RF switch operation, and the measured peak gain is 7 dBi at 2.45 GHz and 10 dBi at 5.8 GHz.     

一种X波段宽带低副瓣微带阵列天线设计

介绍一种新型的x波段宽带低副瓣平面微带阵列天线设计,采用口径耦合馈电的背腔式贴片天线实现了单层微带贴片的宽带工作;采用倒置微带线、低阻传输线、非隔离的T形功分器与双口馈电十字功分器相结合等多种技术手段,弱化了馈电网络的传输损耗、寄生辐射及耦合效应。基于项目需求设计、加工了一套14×14单元天线阵列,测试结果表明,该天线在10．5％的频段内驻波比优于1．5、副瓣电平优于-24．5dB、辐射效率大于55％。     

Circularly-polarised four rhombic loop antennas with high gain and broad beam

A four rhombic loop antenna for circular polarisation is proposed. This antenna has a high gain of about 9.7 dBi and a broad beam of more than 130° half power beam width. Four parasitic loops are added inside the original four loops to increase the axis ratio bandwidth. A broadband balun is incorporated into the antenna for impedance matching. Details of the antenna design and experimental results are presented.     

X波段宽带微带偶极子天线

文中提出一种X波段宽带微带偶极子天线。该天线在偶极子单元的基础上,采用了一个短路探针补偿馈电分布电容,同时增加了一个加载寄生贴片,有效的展宽了带宽。天线的总体尺寸为16mm×24mm,结构紧凑,易于加工和集成,适用于宽带宽角扫描的阵列天线。文中给出了天线的设计参数及不同参数对天线性能的影响。     

Broadband circularly polarized rectangular loop antenna with impedance matching

A broadband circularly polarized rectangular loop antenna is developed. The broadband performance is achieved by adding a pair of parasitic loops inside the rectangular loop. Good impedance matching is obtained by introducing a broadband balun. The proposed rectangular loop has a bandwidth of 46% for axial ratio/spl les/2dB and 50% for VSWR/spl les/2 with a gain of around 8dBi.     

基于均匀圆阵的宽带相干LFM信号定位方法

本文提出一种基于均匀圆阵的宽带相干LFM信号定位方法。首先，算法根据LFM信号在分数阶傅里叶域的能量聚焦性，对接收信号做分数阶傅里叶变换，实现宽带信号的窄带化处理；其次，利用圆阵的虚拟轴向平移形成的相位差构造空间平滑矩阵，完成相干信号的解相干处理；最后，对空间平滑矩阵进行奇异值分解得到相邻阵元接收数据的相位差，结合相位差反演参数估计算法得到二维角度参数估计的闭式解。仿真实验验证了算法对宽带相干LFM信号定位的有效性。     

寄生电感对碳化硅MOSFET开关特性的影响

相比于传统的Si IGBT功率器件而言,碳化硅MOSFET可达到更高的开关频率、更高的工作温度以及更低的功率损耗.然而,快速的暂态过程使开关性能对回路的寄生参数更加敏感.因此,为了评估寄生电感对碳化硅MOSFET开关性能的影响,基于回路电感的概念,将栅极回路寄生电感、功率回路寄生电感以及共源极寄生电感等效成3个集总电感,并且从关断过电压、开通过电流及开关损耗等3个方面,对这3个电感对SiC MOSFET开关性能的影响进行了系统的对比研究.研究表明:共源极寄生电感对开关的影响最大,功率回路寄生电感次之,而栅极回路寄生电感影响最小.最后,基于实验分析结果,为高速开关电路的布局提出了一些值得借鉴的意见.     

A low cost-low loss broadband integration of a CMOS transmitter and its antenna for mm-wave FMCW radar applications

A 60 GHz low-loss wideband interconnection of a CMOS transmitter and its antenna is presented in this paper. The integrated transmitter consists of an all-digital phase-locked loop (ADPLL) IC chip and a U-slot patch antenna connected through wire bonding and compensation matching circuit to operate in the 57–63 GHz frequency band. The system is implemented on a sandwiched printed circuit board (PCB) comprising FR4 to embed the ADPLL and the high-frequency Rogers laminate RO4350B for the antenna and the matching network. The matching circuit is designed in two configurations microstrip and grounded coplanar waveguide (GCPW) to compensate for the wire bond inductance. The capability and sensitivity of these two topologies considering the wire bond geometry variations are compared which points out that GCPW is more robust to wire bonding parasitic effects. Finally, the GCPW matching circuit is fabricated and interconnected to the ADPLL die and its performance is examined using hybrid simulation/measurement data.     

Stacked shorted patch antenna with tilted parasitic radiator

A new compact but wideband patch antenna is presented. Compact dimensions are obtained by using a shorted patch. The antenna bandwidth is increased by using a stacked patch configuration. Further increase in bandwidth is obtained by tilting the parasitic patch. The antenna prototype is fabricated and its input impedance and radiation patterns are measured     

新型强耦合宽带双圆极化阵列天线

空间飞行器由于受到动力和负载的限制, 需要尽可能使搭载的天线轻质小型化.文中提出了一种新型强耦合双圆极化轻质天线.天线单元采用H型缝隙耦合和增加寄生贴片方法, 提高了天线带宽.同时, 通过在辐射贴片、寄生贴片上开圆形槽, 以及金属反射板栅格化的处理, 明显地减轻了天线的质量.采用这种新型天线单元, 设计了8单元的宽带双圆极化阵列天线.仿真结果表明:该阵列天线的中心频率为433 MHz, 左旋和右旋圆极化的相对轴比(Axial Ratio, AR)带宽(AR < 3 dB)分别达到了24.4%和23.2%, 有效实现了小型轻质化宽频带双圆极化阵列天线.     

宽带高增益圆极化天线

设计了一种宽带高增益圆极化天线。天线采用双同轴线激励以及威尔金森功分器和90°相位比较器的馈电网络形式实现了天线的宽带圆极化特性。该馈电网络形式能在较宽的频带范围内保持稳定的幅度和相位。通过在蝶形天线外围引入方形环,增加了天线的有效辐射面积,从而显著提高了天线的增益。测试结果显示,该圆极化天线VSWR<1.5的阻抗带宽达到63.6%,3 dB轴比带宽达到66.7%,且在1.1~1.6 GHz频段范围内,右旋圆极化增益＞9.4 dB。