Investigation of wide-band microstrip slot antenna

This paper presents the simulation and experimental investigations of a printed microstrip slot antenna. It is a quarter wavelength monopole slot cut in the finite ground plane edge, and fed electromagnetically by a microstrip transmission line. It provides a wide impedance bandwidth adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and location of the slot in the ground plane, and feed and ground plane dimensions. The ground plane is small, 50 mm/spl times/80 mm, and is about the size of a typical PC wireless card. At the center frequency of 3.00 GHz, its width of 50 mm is about /spl lambda//2 and influences the slot impedance and bandwidth significantly. An impedance bandwidth (S/sub 11/=-10 dB) of up to about 60% is achieved by individually optimizing its parameters. The simulation results are confirmed experimentally. A dual complementary slot antenna configuration is also investigated for the polarization diversity.     

Multi-band modified fork-shaped microstrip monopole antenna with ground plane including dual-triangle portion

A modified fork-shaped microstrip monopole antenna with the ground plane including a dual-triangle portion is studied experimentally to obtain a large bandwidth and a multi-band characteristic. In this case, the ground plane including a dual-triangle portion leads to improving the impedance matching for a lower band. Although the use of a high relative permittivity (/spl epsiv//sub r/=4.3) substrate usually restricts the operation bandwidth, the radiation resistance also was a low value. The 2.0 VSWR impedance bandwidth is 29.8% (731-987 MHz) for a lower band, and 90.2% (1498-3080 MHz) for a higher band operation. This single-layer microstrip monopole antenna also retains a low and a thin profile characteristic.     

Small dual C-slot printed antenna

A novel shorted dual C-slot printed antenna is presented. The antenna consists of two C-shaped slots embedded within the shorted patch antenna to maximise the current path of the antenna. A 10 dB return loss bandwidth of 5.4% has been achieved. The overall dimension of the antenna is 0.11/spl lambda//sub 0//spl times/0.074/spl lambda//sub 0//spl times/0.074/spl lambda//sub 0/ and is suitable for application where limited space is a premium. Importantly, the antenna is easy to develop.     

2 GHz electromagnetic crystal reflector antenna

The radiation pattern of a monopole antenna with a small electromagnetic crystal (EMXT) reflector was investigated. High frequency structure simulations predict a considerable amount of near-field shielding with undisturbed antenna impedance matching when a perfect magnetic conductor reflector is positioned near the monopole. The pattern distortion created by the reflector gradually decreases, reaching a minimum in the far field. Experimental results show the monopole with an EMXT reflector, /spl lambda//sub 0//4/spl times//spl lambda//sub 0//2 in size, produces a radiation pattern with a front-to-back ratio of 10.8 and 5.7 dB in the near and far fields, respectively.     

Switched parasitic antenna on a finite ground plane with conductive sleeve

A switched parasitic monopole antenna on a finite ground structure with a conductive sleeve attached to a small, circular ground plane controls the vertical radiation direction. The antenna was designed using a genetic algorithm and finite element (FEM) solver. At 1.575 GHz, the constructed antenna exhibited a front to back ratio of 10.7 dB and gain of 6.4 dBi with no elevation from the horizontal. The switched parasitic nature of the antenna allowed it to steer a directional beam through 5 locations in the azimuth. Incremented from 0/spl lambda/ to 0.45/spl lambda/, the sleeve was observed to linearly depress the main lobe elevation with little influence on other antenna characteristics such as gain and S/sub 11/.     

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.     

Composite right/left-handed transmission line based compact resonant antennas for RF module integration

Several electrically small resonant antennas employing the composite right/left-handed transmission line (CRLH-TL) are presented for integration with portable RF modules. The proposed antenna designs are based on the unique property of anti-parallel phase and group velocity of the CRLH-TL at its fundamental mode. In this mode, the propagation constant increases as the frequency decreases, therefore, a small guided wavelength can be obtained at a lower frequency to provide the small /spl lambda//sub g//2 resonant length used to realize a compact antenna design. Furthermore, the physical size and the operational frequency of the antenna depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL, including series inductance, series capacitance, shunt inductance and shunt capacitance. Optimization of these parameters as well as miniaturization techniques of the physical size of unit cell is investigated. A four unit-cell resonant antenna is designed and tested at 1.06 GHz. The length, width and height of the proposed antenna are 1/19/spl lambda//sub 0/, 1/23/spl lambda//sub 0/ and 1/83/spl lambda//sub 0/, respectively. In addition, a compact antenna using a 2-D three by three mushroom like unit cell arrangement is developed at 1.17 GHz, showing that an increased gain of 0.6 dB and higher radiation efficiency can be achieved over the first prototype antenna. The same design is applied in the development of a circularly polarized antenna operating at 2.46 GHz. A 116/spl deg/ beamwidth with axial ratio better than 3 dB is observed. The physical size of the proposed mushroom type small antenna and the circularly polarized antenna is 1/14/spl lambda//sub 0/ by 1/14/spl lambda//sub 0/ by 1/39/spl lambda//sub 0/ and 1/10/spl lambda//sub 0/ by 1/10/spl lambda//sub 0/ by 1/36/spl lambda//sub 0/, respectively.     

Three orthogonal polarisation DRA-monopole ensemble

A dual feed HE/sub 11/spl delta// mode dielectric resonator antenna (DRA) loaded monopole antenna ensemble is described. The two antennas were unaffected by co-location, having coupling less than -25 dB at 2.33 GHz, making the ensemble capable of radiating all three orthogonal linear polarisations. The dielectric resonator antenna had an input impedance bandwidth of 1.9%, while the monopole gave 56%. This small volume ensemble antenna is suitable for mobile communications terminals.     

Printed annular monopole antenna for ultra-wideband applications

A novel printed monopole antenna for ultra-wideband applications is introduced, which consists of an annular monopole patch and a trapeziform ground plane with a tapered CPW feeder in the middle. The simulated and experimental results demonstrate that this antenna achieves a ratio impedance bandwidth of more than 10:1 for VSWR/spl les/2, and exhibits the nearly omnidirectional radiation pattern with a simple structure.     

Development and analysis of a folded shorted-patch antenna with reduced size

The length of a wall-shorted rectangular patch antenna can be reduced from /spl sim//spl lambda//sub 0//4 to /spl sim//spl lambda//sub 0//8 by a simple folding operation, which results in a stacked shorted-patch (S-P) structure with a resonant frequency that can be controlled by modifying the distance between the stacked (lower and upper) shorted-patches. A theoretical analysis based on a simple transmission-line model is presented and compared with numerical simulations, showing good agreement if the height of the folded patch is much smaller than the patch length. The physical insight of the variation of the resonant frequency for this reduced-size antenna can be understood by considering the antenna as a shorted patch loaded with a capacitor. An experimental verification is carried out for a 15 mm/spl times/15 mm/spl times/6 mm folded S-P antenna prototype designed for the 2.4 GHz ISM band that can achieve a 10-dB return loss bandwidth of 4% and results in a nearly omni-directional radiation pattern.     

Design of an efficient miniaturized UHF planar antenna

The design aspects and the measured results of a novel miniaturized planar antenna are described. Such architectural antenna design is of great importance in mobile military communications where low visibility and high mobility are required. Slot radiating elements, having a planar geometry and capable of transmitting vertical polarization when placed nearly horizontal, are appropriate for the applications at hand. Slot antennas also have another useful property, so far as impedance matching is concerned. Basically, slot dipoles can easily be excited by a microstrip line and can be matched to arbitrary line impedances simply by moving the feed point along the slot. Antenna miniaturization can be achieved by using a high permittivity or permeability substrate and superstrate materials and/or using an appropriate antenna topology. We demonstrate miniaturization by designing an appropriate geometry for a resonant narrow slot antenna. A very efficient radiating element that occupies an area as small as 0.12/spl lambda//sub 0//spl times/0.12/spl lambda//sub 0/ is designed and tested. Simulation results, as well as the measured input impedance and radiation patterns of this antenna, are presented. This structure shows a measured gain of 0.5 dBi on FR4 substrate, which has a loss-tangent of the order of 0.01. Also, the effect of finite ground plane size on gain and resonant frequency is investigated experimentally.     

Compact CPW-fed monopole antenna for 5 GHz wireless application

A compact and simple coplanar waveguide (CPW)-fed monopole antenna for 5 GHz wireless communication is proposed. By properly adjusting the lengths of both the monopole strip and the inverted L-shaped ground, the designed antenna, with, including ground plane, only 9/spl times/9.5 mm/sup 2/, can operate at the desired 5.2 or 5.8 GHz band. The electromagnetic coupling effect between the radiating strip and the ground on excitation of the resonant mode has been studied. Prototypes of the proposed antenna have been constructed and experimentally studied. Measured results show a -10 dB impedance bandwidth and an average antenna gain of 400 MHz and >6 dBi, respectively.     

Printed figure-of-eight wire antenna for circular polarization

A new printed wire antenna with circular polarization properties is presented. The geometry of the printed wire which takes the form of a figure-of-eight has a total length of 1.3/spl lambda//sub o/ and serves as a nonresonant traveling-wave antenna. It is shown that a 3-dB axial ratio bandwidth of 15% can be achieved. The half-power and 3-dB axial ratio beamwidth is approximately /spl plusmn/45/spl deg/, while its gain is of the order of 6.5 dB.     

Investigations on miniaturized endfire vertically polarized quasi-fractal log-periodic zigzag antenna

This paper presents the investigations on a miniaturized vertically polarized traveling wave antenna for operation in the high frequency band (3-6 MHz), with a specific requirement of keeping its height near 1/8th of a wavelength. The antenna is desired to have a good endfire gain and front to back ratio, and small radiation levels in the vertical direction at broadside angle. A log-periodic Zigzag antenna (LPZA) has acceptable performance in both gain and polarization. Its height however is large, at about one wavelength (1/spl lambda//sub L/). The concept of fractal antenna is employed in this antenna to achieve the necessary height reduction to /spl lambda//sub L//8, while keeping its radiation characteristics nearly constant. Both single and dual arm quasifractal log-periodic zigzag antenna (QFLPZA) configurations are investigated, with a maximum antenna height of only 1/8th of a wavelength, showing the desired radiation characteristics, and a wide impedance bandwidth of 67%. This type of antenna may find applications in surveillance radar.     

Broadband CPW-fed folded-slot monopole antenna for 5.8 GHz RFID application

A folded slot is introduced to expand the impedance bandwidth and miniaturise the size of a coplanar waveguide (CPW)-fed patch monopole antenna for radio frequency identification (RFID) applications. The designed antenna, which, including ground plane, is only 13 mm in height and 11 mm in width, can operate at the 5.8 GHz band with measured impedance bandwidth and average antenna gain of 30% and /spl ges/5 dBi, respectively, and also conical radiation patterns. These properties make the antenna suitable for RFID tags.     

A miniature UWB planar monopole antenna with 5-GHz band-rejection filter and the time-domain characteristics

A planar monopole antenna with a staircase shape and small volume (25/spl times/26/spl times/1 mm/sup 3/) is proposed in this paper. With the use of a half-bowtie radiating element, the staircase-shape, and a modified ground plane structure, the proposed antenna has a very wide impedance bandwidth measured at about 11.6 GHz (2.9-14.5 GHz, bandwidth ratio about 1:5) below VSWR 2 including the WLAN band notched in the vicinity of 5 GHz. An omnidirectional radiation pattern is obtained. The group delay which is an indication of linearity between two proposed antennas is less than 1 ns. The electrical characteristics in terms of frequency and time domains and physical ones of the proposed antenna make it attractive for use in ultrawideband (UWB) systems.     

CLIP antenna for wireless bluetooth applications

In this paper, a novel design for a coplanar waveguide antenna is developed that consists of two U-shaped slots. The antenna is named CLIP. The antenna was designed for a central frequency of 2.4 GHz, with an input impedance of 50 /spl Omega/. The antenna dimensions represent a 72% size reduction compared to a conventional microstrip rectangular-patch antenna. The measured antenna bandwidth was about 11%, while its gain was about 17 dB. These values are fairly acceptable in all wireless communication systems. The antenna configuration has a bidirectional radiation pattern, while a unidirectional radiation pattern was achieved by using a /spl lambda//sub 0//4 reflector with a metal plate. A 2/spl times/2 multi-element sub array was implemented to widen the application area. The mutual coupling between adjacent elements was low. Orthogonal-plane coupling between adjacent elements was introduced to increase the reduction in the mutual coupling. The mutual coupling level was reduced to less than -23 dB in all coupling planes. The CLIP antenna element and arrays were fabricated. Experimental measurements showed very good performance, which agreed well with simulation results.     

Broadband planar antenna with parasitic radiator

A novel kind of planar monopole broadband antenna with a parasitic radiator is presented. Measurements show that the bandwidth of the monopole antenna has been considerably improved with a parasitic element earthed with a matching inductor. The achieved impedance bandwidth reaches over 85% for VSWR/spl les/2, and the measured radiation patterns have little distortion when the frequency changes. The impedance bandwidth parameters are compared for different dimensions of ground planes     

Uniplanar compact wideband bandstop filter

A uniplanar wideband bandstop filter is proposed using two bent open-end stubs. The proposed filter consists of the bent connecting line of /spl lambda//sub g//2 between two bent /spl lambda//sub g//4 stubs, which results in wideband design with a rejection bandwidth of 90% at 2.05 GHz. Further, the connecting line and stubs have the same characteristic impedance. The proposed filter compared to the conventional one is also more compact. The area of the novel filter is (/spl lambda//sub g//4)/sup 2/ at the center frequency of the stopband, while the area of the filter realized using the nonbent stubs and connecting line is 2(/spl lambda//sub g//4)/sup 2/ for the same stopband characteristics.