基于奇偶模分析法的微波带状线定向耦合器设计

基于奇偶模分析法分析了从一节至多节的耦合器设计公式,并以此设计了1 ～2 GHz的多节交错级联3 dB带状线定向耦合器.采用HFSS对所建立的耦合器模型进行了仿真.仿真结果表明,该带状线耦合器在通带内的传输损耗、反射系数、输出隔离度均在-20 dB以下,直通耦合平坦度在±0.4 dB以内,输入输出驻波比小于1.2.该方法为同类宽带强耦合度的耦合器的研究提供了一定的参考价值.     

Ka波段MEMS共面定向耦合器的模型研究

本文提出一种基于GaAs MMIC技术的Ka波段MEMS定向耦合器结构,并基于微波网络理论对其建立集总S参数模型,从而实现超宽频带的耦合应用.该耦合器在结构上采用全共面传输线形式以易串并联其他元器件,并采用MEMS空气桥以实现地线互连,而无需片外键合线.在模型上,首先对MEMS共面定向耦合器进行各部件结构划分,并提取出相应等效电路模型,其次利用微波级联理论对各部件进行级联,可解出其整体的S参数.利用该模型分析与优化耦合器的关键尺寸参数,优化后MEMS共面定向耦合器在Ka波段S11小于-20 dB、S21在-0.84 dB～-0.89 dB之间、S31在-10.5 dB～-11.3 dB之间、S41小于-25 dB.利用HFSS软件对在该尺寸结构下定向耦合器进行仿真,在Ka波段其S11小于-25 dB、S21在-0.70 dB～-0.79 dB之间、S31在-9.4 dB～-11.5 dB之间、S41小于-25 dB.通过比较发现数学解析模型和HFSS仿真结果显示了较好的吻合,在Ka波段中心频率处S参数误差小于20％,从而验证了解析模型的合理性和有效性.此外,该Ka波段MEMS定向耦合器的设计和模型可作为研究该类MEMS器件的参考.     

宽带带状线定向耦合器的设计

多阶1/4波长滤波器理论为宽带定向耦合器的研究提供了依据,利用该方法设计了应用频段为2~6 GHz的多节3 d B的交错耦合带状线定向耦合器,并利用电磁仿真软件HFSS进行仿真。仿真结果表明,该带状线耦合器具有良好的方向性、较高的耦合度和较低的插损,从而为这类宽带强耦合度耦合器的研究提供了一定的参考价值。     

一种噪声优化的900MHz低噪声放大器设计

设计了一种900MHz的低噪声放大器,采用新的优化方法,同时获得了功率匹配和噪声匹配,在工作电流3．4mA时,得到了0．2dB的噪声系数,20dB的增益以及良好的隔离度和线性度。     

基于PIN管的大功率射频开关研制

随着通信系统发射功率的增加,以及工作频率的提高,高功率容量,高隔离,低插损,短响应时间的射频开关尤其重要。文章简要介绍了PIN管单刀双掷射频开关的原理,对高功率容量下PIN二极管的应用关键进行了详细分析,设计了一个工作于200MHz～500MHz,差损小于0.7dB,隔离度大于70dB,驻波比小一地1.5,功率容量100W,开关速度小于20μs的一分四射频开关。     

一种窄波束测控装备车船摇隔离方法

针对车载/船载状态下的窄波束测控装备的“动中测”测控需求,提出一种“位置环+车船摇前馈补偿+陀螺稳定环”的车船摇隔离方法,并对该方法的船摇隔离度和车摇隔离度分别进行仿真分析,仿真结果表明,采用该方法时,船摇隔离度能达到50 dB以上,车摇隔离度能达到20 dB以上;利用该方法对船摇条件下的高速运动目标跟踪性能进行仿真,仿真结果表明,跟踪误差满足窄波束测控装备的跟踪要求。     

光波导加速度传感器中3dB耦合器设计

光波导加速度传感器是一种实用型加速度传感器,目前广泛应用制备光学加速度计的迈克尔逊、马赫—曾德等干涉仪的核心部件都包含3 dB耦合器。3 dB耦合器的设计对光波导加速度传感器的检测精度尤为重要。介绍了所设计的光波导加速度传感器的工作原理,设计了3 dB耦合器波导的结构和参数,并用光学模拟软件OptiBPM对3 dB耦合器进行模拟。结果表明:所设计的3dB耦合器具有良好性能,符合设计要求。     

周期性慢波结构的微带线威尔金森功分器

采用周期性慢波结构加载的开路传输线代替传统的四分之一波长阻抗变换器,设计一种小型化且适用于高频的Wilkinson功分器,有效改善了传统Wilkinson功分器尺寸大且高频时容易出现色散的问题。最后基于FR4基板,设计应用于900 MHz的Wilkinson功分器,测量结果显示,三个端口匹配良好,S11约为-20.58 dB,S22约为-23.62 dB,S21约为-3.28 dB,输出端口的隔离度约为-33.3 dB,仿真结果和测量结果趋势吻合,验证了该方法的可行性。     

串联电容式RF MEMS开关设计与制造研究

介绍了一种串联电容式RF MEMS开关的设计与制造。所设计的串联电容式RF MEMS开关利用薄膜淀积中产生的内应力使MEMS桥膜向上发生翘曲,从而提高所设计的开关的隔离度,克服了串联电容式RF MEMS开关通常只有在1GHz以下才能获得较高隔离度的缺点。其工艺与并联电容式RF MEMS开关完全相同,解决了并联电容式RF MEMS开关不能应用于低频段(<10GHz)的问题。其插入损耗为-0.88dB@3GHz,在6GHz以上,插入损耗为-0.5dB;隔离度为-33.5dB@900MHz、-24dB@3GH和-20dB@5GHz,适合于3~5GHz频段的应用。     

一种双田字型太赫兹波导定向耦合器的设计方法

基于分支线耦合原理,设计了一个双"田"字型的太赫兹波导定向耦合器。在分支线靠近中间部位插入一条横向贯穿三分支线的横线,用同样的方法形成两分支线,可以有效提高带宽。分支线底部即在靠近波导宽边的地方进行了加粗,目的是增加分支线的应力,提高加工的可行性。使用电磁仿真软件HFSS对该耦合器进行分析和优化,结果显示,该耦合器在313~383 GHz频带内耦合度为6.3±0.2 d B,且耦合度具有较好的平坦性,接近于一条直线,隔离度小于-20 d B,平均插入损耗为0.6 d B,接近于0 d B,每个端口的回波损耗小于-20 d B。     

Design of filtering directional coupler with improved performance

This letter presents a filtering directional coupler (FDC) with enhanced coupling and high directivity simultaneously. The proposed FDC is composed of a pair of coupled lines instead transmission line of a directional coupler. This coupled lines resonator increases the design parameters by which even/odd mode phase velocity can be compensated to improve the directivity and coupling level. The coupling enhancement can be explained by analyzing the even mode and odd mode circuit of the proposed coupler. A prototype of the proposed coupler is designed which provides a high directivity of 44 dB for 6 dB coupling level at 1 GHz frequency. The proposed coupler is designed, fabricated, and tested.     

Design of X‐band Moreno cross‐guide coupler based on superformula curves

This article deals with the design of Moreno cross‐guide couplers based on supershapes for X‐band applications. Crossed‐waveguide couplers are mainly used due to their compact structures. In these couplers, cross‐aperture structures are usually employed to offer flat coupling and high isolation. In the present article, the possible shapes for apertures and metal inserts that can be derived by the superfomula curves are explored and the effects of variations of superformula parameters are investigated on the performance of Moreno coupler. Finally, the proposed Moreno coupler is validated through fabrication and measurement. The experimental validation shows an excellent agreement with the simulated results. In the frequency range from 8 to 12.5 GHz, the measured coupling value changes from 18.8 to 20.8 dB and the directivity is better than 38 dB and 29 dB from 8 to 11 GHz and 11 to 12.5 GHz, respectively. The results are valuable for the design and evaluation of broadband high directive waveguide couplers.     

Investigation of parasitic elements for coupling reduction in multiantenna hand‐set devices

This article investigates parasitic radiating structures for coupling reduction between two 900MHz planar inverted‐F antennas (PIFAs) in a hand‐held device. Measurement of the initial prototype shows that a maximum isolation enhancement of more than 8 dB is achieved with a single parasitic element. This is followed by optimization of the parasitic structure for compactness, improved bandwidth, and tuning capability. First, different techniques for miniaturization are employed to obtain 60% less footprint with a 22 mm x 15 mm meandered parasitic element. Second, it is demonstrated that the isolation bandwidth can be increased by employing several parasitic radiators with different lengths. Finally, it is presented that the operation of a handheld device, as well as the coupling reduction technique, is compromised in proximity to the human body. For the first time, a miniaturized electronically tunable parasitic radiating element is designed to compensate for the detuning of the coupling reduction technique and adjusting its resonance to achieve maximum isolation between two handset PIFAs. Measurements of the fabricated prototype show 810–960 MHz tuning range. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:1–10, 2014.     

High isolation,proximity‐fed monostatic patch antennas with integrated self‐interference cancellation‐taps for ISM band full duplex applications

This work presents two dual polarized proximity‐fed monostatic patch antennas with improved interport isolation for 2.4 GHz industrial, scientific and medical band same frequency full duplex wireless applications. The presented antennas achieves the high interport decoupling through intrinsic isolation of the polarization diversity in conjunction with a simple single‐tap and two‐taps self‐interference cancellation (SIC) topologies. The polarization diversity isolation is achieved through two perpendicular microstrip feeds for proximity feeding to excite orthogonal polarization mode for transmit (T_x) and receive (R_x) modes. The prototype for proposed antenna with integrated single‐tap and two‐taps SIC circuit is tested to record its interport isolation, impedance bandwidths and gains for both T_x and R_x ports. The implemented antenna with single‐tap SIC circuit demonstrates 10 dB return‐loss bandwidth of ≥100 MHz for both T_x and R_x ports. The measured isolation exceeds 40 dB over the 40 MHz bandwidth. Moreover, the recorded peak isolation is better than 74 dB for implemented antenna prototype. Furthermore, the 40 MHz bandwidth with 40 dB isolation can be tuned with the help of SIC‐tap as demonstrated through the experimental results. The measured gain levels are around 4.6 dBi for both T_x and R_x port. The same antenna structure with integrated two‐taps SIC topology features better than 55 dB isolation within 10 dB return loss bandwidth of 100 MHz. The peak isolation exceeds 97 dB and isolation levels are better than 60 and 80 dB over 50 and 20 MHz bandwidths, respectively, for presented antenna with two‐taps SIC configuration. The compact antenna offers comparatively wider impedance and isolation bandwidth with improved SIC levels compared to previous designs.     

Gain and isolation enhancement of patch antenna using L‐slotted mushroom electromagnetic bandgap

In this paper, the application of the L‐slotted mushroom electromagnetic bandgap (LMEBG) structure to patch antenna and antenna array is investigated. A coaxial fed patch antenna and antenna array are designed at 5.8 GHz, center frequency for ISM band (5.725‐5.875 GHz). Two layers of LMEBG are placed around the patch to achieve a gain enhancement of 1.9 dB. Measured results show a bandwidth enhancement of 300 MHz with an additional resonant frequency at 5.6 GHz with 4.5 dB of gain. A 5 × 2 array of LMEBG is used to achieve a 2 dB mutual coupling reduction and 2 dB gain enhancement for a two‐element H‐coupled patch antenna array.     

Multiband multiple‐input multiple‐output antenna with high isolation for future 5G smartphone applications

A multiband high‐isolation multiple‐input multiple‐output (MIMO) antenna using balanced mode and coupled neutralization line (NL) is presented in this article. The balanced modes of dipole and loop antennas, which leads to good isolation intrinsically are used for the 8 × 8 MIMO in the LTE bands 42 (3400‐3600 MHz)/Chinese 5G band (3300‐3400 and 3400‐3600 MHz). The unbalanced mode of loop antennas, which optimized by decoupling structure are designed for the 4 × 4 MIMO in the LTE band 40 (2300‐2400 MHz). Therefore, the eight‐antenna array is formed by four dipole elements and four loop elements. The simulated and measured results show that the proposed antenna can cover 2300 to 2400 and 3300 to 3600 MHz, with reflection coefficient better than ?6 dB and isolation higher than 15 dB. Good radiation performance and low envelope correlation coefficient can also be obtained. Specific absorption rate of user's hand is also discussed in this article.     

Isolation enhancement of rectangular dielectric resonator antennas using wideband double slit complementary split ring resonators

A wideband epsilon‐negative structure is employed as one‐layer and two‐layer isolators to reduce mutual coupling in multiple‐input multiple‐output systems composed of two E‐coupled rectangular dielectric resonator antennas. The proposed unit cell with ?15 dB bandwidth for S₂₁ extending from 1970 to 3317 MHz, is a double slit complementary split ring resonator etched on the ground plane of a stripline. Each layer is composed of a 2 × 3 array of the suggested unit cell. Reduction in isolation of more than 11 dB for the one‐layer case and higher than 20 dB for the two‐layer case are measured within the frequency range of 2.604 to 2.64 GHz which includes WiMAX. The highest isolation level of 36 dB is realized at 2.868 GHz. The impedance matching, gain, radiation efficiency, and envelope correlation are improved compared to the original case. A prototype is designed, fabricated, and tested. Simulation data and measurement results are in good agreement.     

A miniature coupled‐line‐based 3‐dB directional coupler using GaAs PHEMT process

A novel complementary‐conducting‐strip (CCS) coupled‐line (CL) design is proposed to achieve compact size by applying two‐dimensional layout and standard gallium‐arsenide (GaAs) thin‐film technology. To obtain high coupling and satisfy the design rules of GaAs process, mixed‐couple mechanism with edge and broadside coupling are also used. A CCS CL‐based Ka‐band 3‐dB directional coupler is fabricated using WIN 0.15‐μm GaAs pseudomorphic high electron mobility transistor technology. Experimental results show that the proposed directional coupler can cover the entire Ka‐band (26–40 GHz) with through and coupling of approximately 3.7 ± 0.25 dB, and isolation of better than 13 dB. In addition, the phase difference between the two output ports is approximately 90° ± 5°. The occupied area of the prototype (without I/O networks) is only 220 × 220 μm². © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:21–26, 2016.