Circularly polarized patch antenna with simultaneously wide frequency tuning range and high gain performance

A tunable circularly polarized square patch antenna with parasitic elements is designed for a wide frequency tuning range and high gain characteristics. The proposed antenna is constructed by one main patch and four semi-elliptic parasitic units. By loading four varactor diodes and adjusting their capacitance values, the tunable feature is performed to reallocate the corresponding working frequency. Moreover, the diagonal corners of the antenna are cut and loaded with varactor diodes, which provide the appropriate perturbation between the two orthogonality modes of the antenna, so as to ensure the circular polarization characteristic in the entire operating tuning band. The experimental results demonstrate that the reflection coefficient and axial ratio are less than −13 dB and 3 dB, respectively. The proposed antenna features a relatively wide continuously tuning range of 24% within 1.9-2.3 GHz and a stable gain of over 7 dBi with a radiation efficiency of above 85%.     

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.     

一种双频左/右旋圆极化可重构环形缝隙微带天线

设计了一种频率比为1.9的双频左/右旋圆极化可重构环形缝隙微带天线,其在高频段和低频段分别工作于线极化和圆极化状态。在该天线中,环形缝隙和相互正交的四个缝隙臂将接地面分为五部分,缝隙臂上跨接两对PIN二极管开关和隔直电容。通过二极管开关的控制,天线在低频频率上可实现左/右旋圆极化的切换,在高频频率上则可保持其线极化性能不变。实验结果表明,天线在1.6 GHz的低频段上具有12.5%的3 dB轴比带宽,在3.06 GHz的高频段上其–10 dB阻抗绝对带宽为100 MHz,成线极化状态,辐射方向图近似不变。     

高功率双层径向线螺旋阵列天线理论分析与数值模拟

研究了一种高功率双层径向线螺旋阵列天线.论文首先介绍该阵列天线的工作原理,然后从工作原理出发,设计中心频率为4.0 GHz的高功率双层径向线螺旋阵列天线,提出并研究了螺旋单元天线的磁耦合馈电,最后用有限元算法软件对阵列天线进行了数值模拟.模拟结果表明:该口径为320mm的天线在中心频率上可获得21.13dBi的增益,口径效率可达72.3％,在-12°≤θ≤12°的范围内轴向轴比值小于1.55;在3.8GHz~4.2GHz的频率范围内增益大于20.68dBi,口径效率大于69%,天线轴向轴比值小于1.7.     

基于北斗卫星导航系统的一种圆极化微带天线

介绍一种用于北斗卫星导航系统的圆极化微带天线。该天线的主辐射器由开槽的圆形贴片构成,采用单点的同轴馈电,设计的中心工作频率为2．492GHz。仿真结果显示,调节圆形贴片中开槽的长度,可以分离出简并模,激励两个正交的模式,当两个分量相位为90deg,可以实现圆极化。实际测试中,｜S11｜于-10dB的阻抗带宽为0．09GHz,3dB轴比带宽为0．033GHz,与仿真结果基本吻合。     

Design of ultra wideband trapezoidal shape slot antenna with circular polarization

A CPW-feed printed slot antenna with circular polarization characteristics is presented in this paper. The basic structure of the antenna is a rectangular slot excited by a 50 Ω CPW line terminated on a trapezoidal shaped tuning stub. Perturbations in the form of circular stubs are applied in the slot to realize circular polarization. The measured impedance bandwidth (S₁₁ < −10 dB) for the initial design is 4.4 GHz (from 2.2 GHz to 6.6 GHz) while the 3-dB axial ratio bandwidth is 1.77 GHz (from 4 GHz to 5.77 GHz) which is 36.23% at the center frequency of 4.88 GHz. The basic structure of the antenna was further modified to enhance the impedance bandwidth to reach well beyond 12 GHz while increasing the ARBW to 44.3% (from 4.3 GHz to 6.75 GHz). The proposed antenna in its final version has a measured peak gain of about 5 dB throughout the useful band and nearly stable radiation pattern.     

一种基于自偏置技术的低抖动锁相环

设计了一种环路带宽与输入频率的比值固定的自偏置锁相环。对VCO延迟单元进行改进,降低了抖动。采用SMIC 65 nm CMOS工艺,在1.2 V的工作电压下对锁相环进行仿真,输出频率范围为0.5~3.125 GHz。仿真结果表明,在输出频率1.875 GHz处的峰峰值抖动为8.7 ps,电路的核心功耗为45 mW,相位噪声为-79.7 dBc/Hz。     

Compact oscillating slot loop antenna with conductor backing

An oscillating slot loop antenna working at 4.02 GHz is realised with a low cost GaAs MESFET. A conductor backing is used to obtain a unidirectional radiation pattern     

一个自调谐,自适应的1.9GHz分数/整数频率综合器

本文提出了一个具有自调谐,自适应功能的1.9GHz的分数/整数锁相环频率综合器.该频率综合器采用模拟调谐和数字调谐相结合的技术来提高相位噪声性能.自适应环路被用来实现带宽自动调整,可以缩短环路的建立时间.通过打开或者关断 ΣΔ 调制器的输出来实现分数和整数分频两种工作模式,仅用一个可编程计数器实现吞脉冲分频器的功能.采用偏置滤波技术以及差分电感,在片压控振荡器具有很低的相位噪声;通过采用开关电容阵列,该压控振荡器可以工作在1.7GHz~2.1GHz的调谐范围.该频率综合器采用0.18 μ m,1.8V SMIC CMOS工艺实现.SpectreVerilog仿真表明:该频率综合器的环路带宽约为100kHz,在600kHz处的相位噪声优于-123dBc/Hz,具有小于15 μ s的锁定时间.     

Frequency Tunable Microstrip Patch Antenna Using RF MEMS Technology

A novel reconfigurable microstrip patch antenna is presented that is monolithically integrated with RF microelectromechanical systems (MEMS) capacitors for tuning the resonant frequency. Reconfigurability of the operating frequency of the microstrip patch antenna is achieved by loading it with a coplanar waveguide (CPW) stub on which variable MEMS capacitors are placed periodically. MEMS capacitors are implemented with surface micromachining technology, where a 1-mum thick aluminum structural layer is placed on a glass substrate with a capacitive gap of 1.5 mum. MEMS capacitors are electrostatically actuated with a low tuning voltage in the range of 0-11.9 V. The antenna resonant frequency can continuously be shifted from 16.05 GHz down to 15.75 GHz as the actuation voltage is increased from 0 to 11.9 V. These measurement results are in good agreement with the simulation results obtained with Ansoft HFSS. The radiation pattern is not affected from the bias voltage. This is the first monolithic frequency tunable microstrip patch antenna where a CPW stub loaded with MEMS capacitors is used as a variable load operating at low dc voltages     

Far field of large circular loop antennas: Theoretical and experimental results

Far field patterns of large circular loop antennas of circumferences up to two and one-half wavelengths were calculated using Storer's theory for the current distribution on the antenna. To verify the theory, radiation pattern measurements were made at 3 GHz; the experimental results are in good qualitative agreement with theory.     

Macro-micro frequency tuning antenna for reconfigurable wireless communication systems

A small-sized (radiator sime10times8 mm) microstrip monopole antenna for reconfigurable macro-micro frequency tuning is presented. The proposed antenna operates in WiBro (2.3-2.4 GHz) and WLAN 802.11a/b (2.4-2.48 GHz/5.15-5.35 GHz) service bands with a constant antenna gain. Two frequency tuning diodes, a pin diode and a varactor, are incorporated into a meander type radiator. The pin diode is used for frequency switching (macro-tuning) between 2 GHz band and 5 GHz band. In addition, the varactor is used for frequency tuning (micro-tuning) within wireless service bands (2.3-2.48 GHz and 5.15-5.35 GHz) to produce constant antenna gain     

A Miniature Quadrifilar Helix Antenna for Global Positioning Satellite Reception

The design is described of a very compact quadrifilar helix antenna. A hollow ceramic rod is used as a dielectric load to reduce antenna size, which is only 2.7% of an air-loaded quadrifilar helix antenna. A simple equivalent circuit is established for the proposed quadrifilar helix antenna to demonstrate impedance characteristics. A self-phasing method for achieving circular polarization is also proposed. This method is convenient for tuning circular polarization. Additionally, a compact matching structure is designed to match the proposed antenna, which only utilizes short transmission-line sections and one capacitor. For experiments, the proposed antenna is designed at 1.575 GHz such that it can be utilized for global position system. Measurement and simulation results agree. A hemispherical pattern with a beamwidth of 150 $^{circ}$ is measured. This circular-polarized pattern with a wide beamwidth is feasible for mobile applications.      

Metamaterial inspired quad band circularly polarized antenna for WLAN/ISM/Bluetooth/WiMAX and satellite communication applications

A CPW fed metamaterial inspired Quadband circularly polarized antenna is presented in this article. The proposed antenna consists of defected ground structure with a radiating stub, which is at opposite side of the feedline. A waveguide mode of analysis is carried out for split ring resonator (SRR) and complimentary split ring resonator (CSRR) to enhance the properties of metamaterials. The proposed antenna analysis is taken iteration wise and used FR-4 Material as the substrate material with Ɛ_r = 4.4 and analysed using ANSYS electromagnetic desktop. The designed antenna projecting the peak gain of 4.8 dB and it is working in the application bands of WLAN/ISM/Bluetooth at 2.4 GHz, 5.8 GHz and 3.35 WiMAX band, X-band downlink satellite communication system (7.25–7.75 GHz) and ITU band (8–8.5 GHz) with fractional bandwidth of about 70%. Proposed antenna exhibits circular polarization at 2.39–2.55 GHz, 3.05–3.1 GHz, 4–5 GHz and 6.3–6.64 GHz respectively. To know the signal integrity of the antenna, time domain analysis is carried out for identical antennas in two conditions (face to face and side by side) with the help of CST microwave studio. The designed antenna showing excellent correlation in measurements with respect to simulation results.     

Circularly polarized twisted loop antenna

A novel wire-loop antenna is introduced for circular polarization. By introducing a small gap at the middle of two nonradiating sides of a one-wavelength square wire loop, a 90/spl deg/ time-phase difference between the currents on the other two radiating sides can be achieved. Then by twisting the square loop to make the radiating sides orthogonal the necessary conditions are satisfied for circularly polarized radiation. The antenna yields nearly ideally circular polarization at broadside as well as excellent input impedance properties near the design frequency. The radiation pattern has a broad beamwidth and good rotational symmetry about the axis. For a demonstrator operating at 1 GHz, a 3-dB axial ratio was maintained over /spl plusmn/30/spl deg/. The mechanism of circular polarization is analyzed based on numerical simulation. Experimental results are presented to verify the theoretical predictions made.     

Determination of reactance loading for circularly polarized circular loop antennas with a uniform traveling-wave current distribution

A simple theory is presented to predict the lumped reactance loading for circularly polarized circular loop antennas with a uniform traveling-wave current distribution. The reactive load is located on a circular wire loop of one-wavelength circumference at a position of 45/spl deg/ away from the feed point. To achieve a uniform traveling-wave current distribution, the loading reactance and the input impedances of the loaded and unloaded loop antennas need to satisfy certain conditions. First, the input resistance and the input reactance of the unloaded loop antenna should have the same absolute value. Second, the input impedance of the loaded loop must be purely resistive and its value needs to be two times of the input resistance of the unloaded loop. Third, the loading reactance should be chosen to be two times in value and opposite in sense of the input reactance of the unloaded loop. These conditions can be approximately met when the circular loop is placed above a ground plane. The loading reactance is determined from the input impedance of the unloaded loop and is optimized for an optimal performance of circular polarization. It is found that the reactive load must be capacitive and its value depends on the height of the loop above the ground plane and the thickness of the wire. The characteristics of the circular polarization and the input impedance of the capacitance-loaded circular loop antennas are investigated. An experimental example is presented to verify the theoretical prediction.     

一种高隔离度的双倒L形双频MIMO天线设计

研究了一种微带线馈电的双倒L形双频MIMO印刷天线结构,通过在倒L单极子结构上加载一条倒L形地板枝节,实现了天线的双频特性;通过在天线单元之间加载一条T形去耦枝节,有效提高了天线单元之间的隔离度。实验结果表明,天线在S11≤-10 dB时,工作频段分别为2.39~2.53 GHz和4.92~6.15 GHz,相对带宽分别为5.7%和22.2%,工作频段内隔离度均大于18 dB。此外,天线整体辐射特性较好,结构简单并易于制作,可应用于WLAN无线通信系统。     

Isolation enhancement for dual‐band MIMO antenna system using multiple slots loading technique

In this paper, a novel multiple slot loading technique is studied in detail for the isolation enhancement of the dual‐band MIMO antenna system. The proposed MIMO antenna design consists of the microstrip patch loaded with T‐shaped slots parallel to the non‐radiating edge of the patch. The frequency tuning could be achieved by varying the length of the T‐shape slot arm. The proposed MIMO antenna system is optimised for operation in WLAN and WiMAX applications. The isolation enhancement is achieved by providing simple multiple slots loaded in the ground plane between radiating elements. The length of the slots is λ/4 . The system is fabricated and tested using a vector network analyser and anechoic chamber. The reduction in mutual coupling up to ?29.16 dB and ?24.09 dB for the 2.4 GHz and 3.4 GHz, respectively, is achieved. The bandwidths are 62.3 MHz (3.33–3.39 GHz) and 55.5 MHz (2.37–2.42 GHz), respectively. The total gain obtained in this case is 1.8 dBi at 2.4 GHz and 1.2 dBi at 3.4 GHz, respectively. The dimensions of the proposed designed antenna are 70 mm × 60 mm × 1.6 mm. The results were also verified through mutual coupling parameters like envelope correlation coefficient (ECC) and channel capacity loss (CCL) at the desired frequencies.     

Dual-band polarization and frequency reconfigurable antenna using double layer metasurface

In this paper, a polarization and frequency reconfigurable antenna with double layer metasurface, responsible for frequency and polarization reconfiguration respectively, is proposed. This antenna could operate in linear polarization in 4 GHz and circular polarization in 5 GHz band. By rotating the frequency reconfiguration metasurface, the linear polarization (LP) operating frequency can be continuously changed from 4 GHz to 4.35 GHz (8.4%) with circular polarization operating frequency around 5 GHz unchanged. Moreover, polarization of the whole antenna at 5 GHz can be reconfigured to linear polarization (LP), right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) by rotating polarization reconfiguration metasurface, the 3 dB axial ratio bandwidth is 5.0–5.2 GHz (4%). In all states, gain of the antenna achieves 5 dBi.     

一种新型波束可控的口径耦合天线

设计一种基于人工电磁结构（AMC）的新型口径耦合天线。对加载了AMC 结构的口径耦合天线进行仿真。 根据仿真结果,天线的工作频率为5.5GHz,辐射的波束指向21°时增益为6.4dB。文中对天线的参数进行分析,波束 的偏移角度与AMC 结构的有关。将AMC 结构变为一排,天线波束可以指向11°。根据天线单元构造1×2 的子阵, 阵列天线具有更高的增益和带宽,并可以有波束的偏移。 天线子阵工作在5.5GHz 时天线的波束指向为26°,增益 8.47dB。