Design and Simulation of a Novel Micromachined Frequency Reconfigurable Microstrip Patch Antenna

In this paper, a novel model of a frequency reconfigurable microstrip patch antenna based on MEMS (microelectromechanical system) technology is introduced. Fabrication process of the proposed antenna is comprised of bulk and surface micromachining. Patch of the antenna is deposited over a silicon platform. The platform is created by structuring the silicon membrane which is formed through bulk micromachining of a silicon chip. The patch and the platform beneath it are discretized to facilitate their vertical displacement over underside air gap. Thermal actuation is used as driving mechanism. Operational mechanism of the antenna is such that by downward relocation of the patch, its resonant frequency shifts downward. Thermal actuators are connected to the platform and applying voltage to them cause downward shift in resonant frequency of the antenna. FEM (finite element method) simulations confirm mechanical and microwave performances of the antenna which are investigated by theoretical analyses. From mechanical point of view, antenna has tolerable mechanical stability and microwave point of view indicates that return losses are good (below $-$ 10 dB) and radiation patterns are very close to each other with reasonable gains. Moreover VSWR is less than 2 throughout the frequency tuning range. In the proposed antenna by applying a CMOS compatible voltage in the range of 0–4.5 V to each thermal actuator, the resonant frequency of the antenna shifts from 17.37 GHz in up-sate position to 15.07 GHz in down-state position. As a result of this frequency shift, a frequency tuning range of 2.3 GHz with bandwidths of 3.9 % in up-state and 1.4 % in down-state positions is achieved.     

一种L、S波段微机械压控振荡器

报道了一种中心频率为2GHz的电感电容(LC)压控振荡器,其谐振回路由微机械可变电容和键合线电感构成。微机械可变电容采用与集成电路兼容的表面微机械工艺制造,在2GHz时其Q值约为32.6,当调节电压从0V增大到12V时,电容量变化范围为25%。通过键合技术将微机械可变电容与有源电路集成在一起,制备了MEMSVCO器件,测试结果表明,载波频率为2.004GHz时,VCO的单边带相位噪声为-103.5dBc/Hz@100kHz,输出功率为12.51dBm。调频范围约为4.8%。     

Electrically tunable rectangular microstrip antenna

The tunable microstrip patch antenna using electrostatic force is presented. The antenna was patterned on the top side of a (poly-ethylene terephthalte) film. When a DC bias voltage is applied between the flexible patch and the fixed ground plane, the flexible patch bends downwards towards the fixed ground plane owing to the electrostatic force of attraction. The bending of the flexible patch decreases the air-gap, and consequently the effective permittivity of the antenna is increased. By increasing effective permittivity, the resonant frequency is shifted downwards. For the tunable microstrip patch antennas of 6, 8 and 10 GHz at DC bias 150 V, the measured tuning ranges were 217.04, 242.58 and 365.63 MHz, respectively.     

具有陷波功能的超宽带缝隙天线的设计与研究

提出了一种具有陷波功能与分形调谐支节的新型超宽带缝隙天线.该天线的结构类似于一般的微带缝隙天线,通过采用分形调谐支节引入半波长谐振结构,使得该天线不仅具备了超宽带缝隙天线的优点,还具备灵活可调的陷波功能.通过计算、测量和尺度放大实验,充分考察了天线的频域特性.实验结果表明该天线的工作频带为2.66～10.76 GHz,在4.95～5.85 GHz频段上具有陷波功能,同时具有相对稳定的辐射方向性和近似的全向特性.该研究对设计小型超宽带天线具有一定的价值.     

Frequency notched ultra-wideband microstrip slot antenna with fractal tuning stub

A frequency notched ultra-wideband (UWB) microstrip slot antenna with a fractal tuning stub is proposed. The antenna is similar to a conventional microstrip slot antenna, and by introducing a fractal tuning stub, frequency notched function is achieved. The antenna was studied experimentally regarding impedance bandwidth, radiation patterns and gain. The operation bandwidth of the antenna is from 2.66 to 10.76 GHz, in which a frequency notched band from 4.95 to 5.85 GHz was achieved, along with good radiation performance over the entire frequency range.     

Frequency notched printed slot antenna with parasitic open-circuit stub

A new frequency notched ultra-wideband microstrip slot antenna with a parasitic tuning stub is proposed. The antenna is similar in configuration to a conventional microstrip slot antenna; by introducing a parasitic open-circuit tuning stub, flexible frequency notched function is achieved. Several properties of the antenna, such as frequency notched function, antenna transfer function and gain, have been investigated. As is reported, the operation bandwidth of the antenna is 2.91-11.16 GHz, in which a frequency notched band of 5.10-5.85 GHz has been achieved. Furthermore, good ultra-wideband linear transmission performance over the entire operation frequency range has also been achieved.     

低RCS栅格微带天线研究

研究了栅格微带天线在微带天线RCS减缩中的应用。分析了栅格线宽度、栅格线间距、栅格化方式等参数对天线的谐振频率、增益的影响。设计了一副具有低RCS特性的栅格微带天线,与谐振在同频率的微带贴片天线相比,天线的增益仅降低0. 6dBi,而天线在2~10GHz频带内的平均RCS降低4dBsm。     

Shorting pin loaded dual-band compact rectangular microstrip antenna

Theoretical and experimental investigations carried out on shorted microstrip patch antenna for dual band operation. The investigations were carried out by varying the shorting-pin position from the edge to the centre of the patch; such an antenna provides a frequency tunability range from 0.88?GHz to 1.08?GHz for first resonance and from 2.20?GHz to 2.59?GHz for second resonance. A frequency ratio of about 2.91 to 2.2 for the two operating frequencies is observed. When the shorting-pin position is close to centre or at the centre of the patch, a single resonant frequency is observed. It is also observed that the resonant frequency of the antenna heavily depends upon the thickness of the substrate, dielectric constant of the substrate and radius of the shorting-pin.     

一种S波段宽带微带贴片天线阵列的设计

介绍了一种宽带微带贴片天线单元及2元阵列的设计方法,天线工作的中心频率为rl_5OHz（S波段）。天线单元设计中采用口径耦合理论和层叠贴片天线结构,有效增大了天线的阻抗带宽。仿真结果表明该天线阵列实际增益达到11．9dB;在2．27～2．78GHz频率范围内端口驻波比小于2,相对带宽为20．4％;交叉极化电平为-31dB,证明该天线阵具有宽频带、低交叉极化等优良性能。     

基于BST可变电容的电调微带天线研究

采用BaxSr1–xTiO3(BST)可变电容作为调谐元件研制了一种工作频率可调的电调谐微带天线。该天线通过利用单片机控制电源单元输出不同的偏置电压来改变BST可变电容的电容大小,进而实现工作频点的调整。结果表明,当电源输出偏压在0-52 V变化时,该微带天线的工作频点可在1.47-1.61 GHz调节,回波损耗低于–15 dB。     

Square-ring microstrip antenna with a cross strip for compactcircular polarization operation

A novel design of square-ring microstrip antenna with a cross strip for achieving compact circular polarization (CP) operation is proposed and experimentally studied. The cross strip can be placed in the centerlines or diagonals of the square-ring patch. Either design can make its excited fundamental mode patch surface current path much longer than that in a conventional square microstrip antenna with same antenna size. By incorporating a small tuning stub for splitting the fundamental mode into two near-degenerate resonant modes with equal amplitudes and 90° phase-difference compact CP operation for the proposed design can he obtained     

Double MOS Loaded Circular Microstrip Antenna with Airgap for Mobile Communication

A novel model of a wide frequency range double MOS loaded circular microstrip patch antenna with airgap between ground plane and substrate is proposed. In this structure two metal oxide semiconductor (MOS) devices are loaded on the patch to enhance the operating frequency range of antenna. To investigate the antenna, different parameters such as resonance frequency, input impedance, frequency agility, VSWR, radiation pattern etc. are calculated and simulated. The resonant frequency of proposed 10 mm radius patch is upward shifted from 5.2 to 6.8 GHz using 1 mm airgap and by loading MOS, antenna can be tuned down to 1.27 GHz operating frequency, which leads to compactness and tunability of antenna. Proposed antenna can be tuned between 1.27 and 6.8 GHz frequency of operation which makes the antenna highly suitable for wide frequency range of mobile communication. The proposed double MOS loaded antenna possessed 82.94 % frequency agility. The antenna is worth for GPS, WLAN, UMTS, and WiMAX operations.     

Bandwidth enhancement of a microstrip-line-fed printed wide-slotantenna

Printed wide-slot antennas fed by a microstrip line with a fork-like tuning stub for bandwidth enhancement are proposed and experimentally investigated. Both the impedance and radiation characteristics of this antenna are studied. Experimental results indicate that a 1:1.5 VSWR bandwidth of 1 GHz is achieved at operating frequencies around 2 GHz, which is nearly ten times that of a conventional microstrip-line-fed printed wide-slot antenna. It also achieved a 2-dB gain bandwidth of at least 0.5 GHz     

一种新型的具有带阻特性的超宽带微带天线

设计制作了一种新型的具有带阻特性的超宽带微带天线。天线采用50Ω共面波导馈电结构,辐射单元采用圆形金属贴片,在圆形贴片上开一个倒U形槽,实现了天线的带阻特性。测试结果表明:在频率段2.8-12.0 GHz内(除5.00-5.95 GHz外)天线驻波比小于2,且天线具有近似全向辐射的特性;而天线在频率段5.00-5.95 GHz内形成了阻带,从而有效阻隔了WLAN(5.150-5.825 GHz)频率段。该天线具有尺寸小,易于与微波电路集成等优点,可以用于超宽带系统。     

Planar circular loop antennas with self-biased magnetic film loading

A circular loop antenna with self-biased magnetic film loading at 1.7 GHz is presented. The proposed circular loop antenna is realised by cascading a microstrip loop and a tuning stub. Self-biased NiCo-ferrite magnetic films were used to tune the working frequency of the loop antenna. Three different cases of antennas with films loading were designed and analysed. Antennas with self-biased magnetic films loading working at 1.7 GHz with a tuning range of 50-400% of the antenna bandwidth were achieved.     

Dual-band reactively loaded microstrip antenna

A previously derived theory is applied to a microstrip antenna with a reactive load to produce a dual-band radiator. A model consisting of a rectangular patch radiator loaded with a variable length short-circuited coaxial stub was investigated experimentally. Comparisons of theoretical predictions and experimental data are made for the impedance and resonant frequencies as a function of the position of the load, the length of the stub, and the characteristic impedance of the stub.     

C-shaped slot loaded reconfigurable microstrip antenna

A new electronically reconfigurable dual frequency microstrip patch antenna with highly simplified varactor tuning circuitry is presented. The proposed design allows relatively independent selection of the two operating frequencies. Tuning ranges of 7.1 and 4.1% are realised for the two resonant frequencies without the use of any matching circuits.     

一种具有双阻带特性的超宽带单极子天线设计

为克服无线通信中系统间的相互干扰,采用频带抑制技术设计了一种具有双阻带特性的超宽带单极子天线。首先采用共面波导进行馈电,辐射贴片和共面波导均为阶梯结构,使其在2.9～12GHz频带内电压驻波比小于2;其次在辐射贴片上分别引入C形和倒U形槽谐振结构,使其在3.3～3.9GHz和5.1～5.9GHz的频带内电压驻波比大于2;最后通过仿真与测量,验证该天线实现了良好的频带抑制功能。     

Design and Analysis of Triple-Band Rectangular Microstrip Antenna Loaded with Notches and Slots for Wireless Applications

In this paper, a rectangular triple-band microstrip antenna has been designed for Bluetooth application by successively loading notches and slots of different dimension in radiating patch. The conventional microstrip antenna suffers with narrow impedance bandwidth. The current work affords an alternate option to enhance the bandwidth of antenna that resonates in triple-band operation. Initially, the antenna is resonating in single-band but after loading slots, the bandwidth of microstrip antenna has been obtained 1.97% (lower band), 10.35% (middle band) and 33.16% (upper band) resonating in triple-band with three resonant frequency at 1.422 GHz (lower resonant frequency), 1.791 GHz (middle resonant frequency) and 2.467 GHz (higher resonant frequency). The suggested antenna has upper frequency band in the range of 2.045–2.858 GHz resonating at 2.467 GHz frequency and it is appropriate for Bluetooth applications (2.40–2.48 GHz) and both lower band useful for other wireless (L-band) applications. The return loss of upper band is ??34.52 dB at 2.467 GHz. The suggested microstrip antenna is directly fed by 50 ohm microstrip line feed. The suggested antenna has been designed, simulated and analyzed by IE3D simulation software.

     

Microwave characteristics of liquid-crystal tunable capacitors

This letter investigates the microwave characteristics of the liquid crystal tunable capacitors for the first time. With the dielectric anisotropy properties, the liquid crystal capacitors present very different characteristics compared to the semiconductor or MEMS tunable capacitors. A quality factor of 310 with a control voltage of 5 V was achieved at 4 GHz. A tuning range of 25.3% for the control voltages from 0 to 5 V was obtained at 5 GHz. The results demonstrate the potential applications of liquid crystals as dielectric materials for capacitors with high quality factors and wide tuning ranges at high frequencies, particularly suitable for the future flexible electronics with transparent substrates.