A novel approach for miniaturization of slot antennas

With the virtual enforcement of the required boundary condition (BC) at the end of a slot antenna, the area occupied by the resonant antenna can be reduced. To achieve the required virtual BC, the two short circuits at the end of the resonant slot are replaced by some reactive BC, including inductive or capacitive loadings. The application of these loads is shown to reduce the size of the resonant slot antenna for a given resonant frequency without imposing any stringent condition on the impedance matching of the antenna. A procedure for designing this class of slot antennas for any arbitrary size is presented. The procedure is based on an equivalent circuit model for the antenna and its feed structure. The corresponding equivalent circuit parameters are extracted using a full-wave forward model in conjunction with a genetic algorithm optimizer. These parameters are employed to find a proper matching network so that a perfect match to a 50 /spl Omega/ line is obtained. For a prototype slot antenna with approximate dimensions of 0.05/spl lambda//sub 0//spl times/0.05/spl lambda//sub 0/ the impedance match is obtained, with a fairly high gain of -3dBi, for a very small ground plane (/spl ap/0.20/spl lambda//sub 0/). Since there are neither polarization nor mismatch losses, the antenna efficiency is limited only by the dielectric and ohmic losses.     

Electronically tunable magnetic patch antennas with metal magnetic films

AS new type of electronically tunable magnetic patch antennas with metal magnetic films was designed, fabricated, and tested at 2.1 GHz. The magnetic patch antennas showed an enhanced bandwidth of 50% over the non-magnetic patch antennas, a significantly enhanced directivity, and a large tunability of the radiation intensity of 4.23 dB at a low applied magnetic field of ~20 Oe     

A BROADBAND FEEDING TECHNIQUE FOR MICROSTRIP PATCH ANTENNAS

In order to broaden the bandwidth of a microstrip patch antenna,a broadbandtwo-port feedingtechnique based on the principle of reactance compensation is suggested.The principle and some designguidelines are presented;the calculating model of a practical configuration as well as its parameteroptimization is demonstrated,followed by several kinds of test models With their experimental results.It isshown that this technique enables the VSWR bandwidth to be broadened to 2—3 or more times that of aconventional design for both linear and circular polarization operation.     

Wideband patch antennas for mobile communications

This paper describes a new technique for bandwidth enhancement of microstrip patch antennas. An electromagnetically coupled (EMC) feeding structure was employed to increase the bandwidth. L-strip feeding rectangular and triangular patches were simulated and tested. The obtained bandwidth (SWR2) is about 1200 MHz (52%) for the rectangular patch, while that of the triangular one is around 1300 MHz (56%). These results provide evidence that the proposed designs can be used in the DCS, PCS, UMTS, WLAN and IMT-2000 service frequency bands.     

Broadband microstrip patch antennas for MMICs

A broadband microstrip patch antenna well suited for monolithic microwave integrated circuits (MMICs) is presented. The antenna exhibits a measured bandwidth of 35%, low surface wave loss, a high front-to-back ratio, and is fabricated directly on the MMIC substrate material. The predicted and measured input impedances are given along with the measured radiation performance     

Polygonal patch antennas for wireless communications

An effective design of polygonal patch antennas with multifrequency or broad-band operation modes for wireless communications is presented in this paper. It is shown how polygonal patches with suitable features may be obtained after a proper perturbation of conventional rectangular geometries, which inherently present poor bandwidth performances. These perturbed irregular geometries may support multiple resonances and, thus, may present a broad-band or multifrequency operation mode, even employing conventional patch antennas with a single dielectric substrate. These polygonal patches are efficiently analyzed through a numerical code based on the method of moments, with entire domain basis functions that accurately describe the radiation mechanism. After the presentation of the analysis and design techniques, some antenna layouts for modern wireless communication systems will be proposed. Such antennas are designed for both universal mobile telecommunication system and wireless local area network portable equipment with real-life finite ground planes.     

Coplanar waveguide feed for microstrip patch antennas

A coplanar waveguide (CPW) loop is shown to be an effective low VSWR feed for microstrip antennas. The low VSWR transition between the CPW and the antenna is obtained without the use of a matching circuit, and it is relatively insensitive to the position of the antenna and the feed.<>     

Corrugated circular microstrip patch antennas for miniaturisation

New concepts for a corrugated circular microstrip patch antenna (CCMPA), which is moving in the radial direction and works at a frequency of 1.575 GHz (GPS), using linear and circular polarisation for miniaturisation are designed and fabricated. The linearly-polarised antenna has a reduction of 8.08% in patch diameter, a reduction of 21.12% in area and an increase of 1% in bandwidth compared with a circular microstrip patch antenna (CMPA). The radiation patterns of E-and H-plane for a corrugated-type antenna follow the general CMPA and the gain of the linearly-polarised antenna is 6.8 dBd. Also, the circularly-polarised antenna has a gain of 2.8 dBd and an axial ratio of 1.3 dBd at 1.575 GHz     

Wide-band E-shaped patch antennas for wireless communications

This paper presents a novel single-patch wide-band microstrip antenna: the E-shaped patch antenna. Two parallel slots are incorporated into the patch of a microstrip antenna to expand it bandwidth. The wide-band mechanism is explored by investigating the behavior of the currents on the patch. The slot length, width, and position are optimized to achieve a wide bandwidth. The validity of the design concept is demonstrated by two examples with 21.2% and 32.3% bandwidths. Finally, a 30.3% E-shaped patch antenna, resonating at wireless communication frequencies of 1.9 and 2.4 GHz, is designed, fabricated and measured. The radiation pattern and directivity are also presented     

E-shaped patch antennas for high-speed wireless networks

Thin, broad-band, E-shaped microstrip patch antennas (ESPAs), operating in the 5-6 GHz frequency range, are presented. They are intended for high-speed (IEEE 802.11a, 54 Mb/s) wireless computer local area networks (WLAN) and other wireless communication systems. They are suitable for WLAN adaptor cards in the PCMCIA (also known as PC) format, allowing users of current notebook computers to upgrade to this high-speed wireless standard at a low cost. Importantly, our antennas are thin enough to be accommodated in a PCMCIA card of standard 5-mm thickness, without making the antenna end thicker than the card itself. Two different closely spaced antenna pairs are also presented for diversity. A new ESPA configuration with a microstrip feed is presented for easy integration with microwave transceivers. In all cases, within the two IEEE 802.11a WLAN bands (5.15-5.35 GHz and 5.725-5.825 GHz), the reflection coefficient at the antenna input is <-10 dB and in both antenna pairs, mutual coupling between the two antennas is <-20 dB.     

Reconfigurable patch antennas for steerable reflectarray applications

Reconfigurable reflectarrays have been designed with patch elements which can vary the reflected phase by varying the height of the patches. These patches have been designed using a periodic method of moments simulation. Reflectarrays incorporating elements of varying heights have been built and tested. The first design is a 33 element array comprised of stacked patches which operates at 7.31 GHz. The second design is a 120-element dipole array over a ground plane which operates at 5.2 GHz. Microelectrical, mechanical systems actuation technology could be used to implement these designs and a potential concept is suggested.     

Radial EBG cell layout for GPS patch antennas

A novel radial layout for mushroom-like electromagnetic-bandgap (EBG) cells surrounding a printed circularly-polarised patch antenna is proposed. Two radial EBG configurations surrounding a circular patch are compared to a reference patch on a conventional ground plane of the same dimension. The radial shape and displacement of the EBG cells around the patch offers improvements in terms of gain and axial-ratio compared to the reference antenna and is more suitable for circular geometries compared to conventional Cartesian layouts. In particular, the distance between the patch and the surrounding EBG cells is independent of the cell period, which can be arbitrarily chosen, and the overall layout offers footprint reduction.     

A class of broad-band patch microstrip traveling wave antennas

Measured voltage standing-wave ratio (VSWR) and radiation characteristics are presented for a class of antennas consisting of nonuniform arrays of rectangular patches having variable dimensions, and excited by traveling waves on microstrip lines. The results indicate that when properly designed these linearly polarized antennas are capable of providing large bandwidths with regard to input VSWR and radiation properties.     

On the role of substrate loss tangent in the cavity model theory ofmicrostrip patch antennas

The effective loss tangent (δ_eff) plays an important role in the improved cavity model of microstrip patch antennas. It is calculated using an iterative procedure. Results are presented here showing that the final value of δ_eff is quite sensitive to the value chosen at the start of the iterative process, i.e., the substrate loss tangent (tan δ). Since the input impedance depends on δ_eff, it is important to specify the value of tan δ in any comparison with experiment     

Active inverted stripline circular patch antennas for spatial powercombining

An active antenna configuration is proposed for spatial-power-combining applications. The active patch antenna uses an inverted stripline topology to take advantage of several features. These features include avoiding drilling through the circuit substrate to insert the diode and the use of air within the resonant cavity to reduce loss. The inverted substrate serves as a radome for hermetic sealing. The active antenna and housing can be fabricated in modular form for reduced cost and easy replaceability of devices. The active inverted stripline patch antenna exhibits a much cleaner spectrum and greater stability than previously reported active antennas. The fixture serves as a ground plane, heat sink, and support in an active planar array or as a mirror in a quasi-optical power-combining resonator. A single active antenna operating at 9.23 GHz exhibited a 16-MHz locking bandwidth at 30-dB locking gain. Power-combining efficiencies of over 89% have been demonstrated for a four-element square array that maintained injection-locking and power-combining over a 60-MHz bias tuned bandwidth. Similarly, a four-element diamond array showed over 86% combining efficiency and 50-MHz bias tuned bandwidth. Beam steering was demonstrated by varying bias voltage to the individual antenna elements of the square array     

馈电相位可调极化可重构微带贴片天线

设计了一种相位可调的极化可重构微带贴片天线.该天线采用双馈电方式工作,通过改变馈电网络中4个单刀双掷开关的导通状态在两个馈电点形成不同的相位差,从而实现左旋圆极化、右旋圆极化以及线极化之间的切换.实验结果与理论分析和仿真结果相吻合,天线实现了良好的极化重构能力.特别是不同极化状态下,天线工作频率具有良好的一致性.     

一种新型的基于UC-PBG基底的微带天线

提出了一种新的基于平面光子带隙(UC-PBG)结构的微带天线,在基底上开了一个凹槽,天线贴片位于槽的底部,设计天线的工作频率落在光子晶体的禁带之内.通过对该结构进行数值仿真,证实了该设计在抑制表面波,提高增益及效率和改善辐射方向性等方面的有效性.     

A study of the effect of the top patch in rectangular dual patch microstrip antennas

A moment method procedure is used to solve the integral equations describing rectangular dual patch microstrip antennas. After checking the accuracy of the procedure by comparing calculated with measured results, it is used to analyse theoretically the effect of the top patch, especially the variation of the impedance curve and the gain of the configuration with two parameters, the distance between the two patches and the size of the top patch. Finally, a first attempt is made to outline a technique for the determination of these two parameters in order to obtain a maximum bandwidth.     

A new class of electrically small antennas

This paper describes a new class of electrically small antennas, of which the principal advantages are the resistive input impedance, the radiation resistance transformation which may be obtained within the structure, and the variety of shapes which the antennas may take. The antennas incorporate resonant half-wave windings, and a simple transmission line theory is presented by which antenna efficiency and bandwidth may be calculated. Experimental methods and results are described for antennas in the order of 0.01 wavelength in height and 0.05 wavelength in diameter.