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The contribution of this paper is to proposed a simple slot antenna miniaturization method using copper coated FR_4 dielectric material loading technique. The operating frequency for reference antenna and loaded antenna are 2.86GHz and 1.66GHz respectively. As a result, overall size of proposed antenna reduces by a ratio of 41.95%. A
parametric study on various copper coated dielectric materials is presented to better understand the effect of the permittivity on slot antenna miniaturization. The antenna topologies are designed and analyzed using High Frequency Structure simulator (HFSS) tool. The prototype was fabricated and measured, and the measured results show good agreements with the simulated ones. This antenna can be very useful for various wireless communication systems.
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Miniaturized circular patch antennas loaded by helices, which operate as μ-negative (MNG) metamaterials, is reported. Two antennas having different helix parameters have been fabricated. The patch radius for both antennas is 42 mm. The first fabricated antenna shows a resonance at 1.126 GHz, which corresponds to a 40% size reduction. The second antenna has an even better size reduction of 60%. Measured results of return loss and radiation pattern at the subwavelength resonances are compared to these parameters at the conventional resonance of the patch antenna.
In this work, miniaturization of Coplanar waveguide (CPW) fed slot antenna loaded with loop is presented. In addition to that, it is also possible to further reduce the resonant frequency with proper loading of circular loop and cylindrical Dielectric Resonator (DR). The unloaded and loaded resonance frequencies are 4.46 GHz and 2.23 GHz respectively which results in 50% reduction in resonant frequency without effecting radiation characteristics. But, with only loop loading on either end of radiating slot exhibits 19.50% reduction in resonance frequency. We also introduced hollow cylindrical dielectric resonator in loop loading antenna topology in that case we got 29.37% miniaturization in resonant frequency. Also after loading efficiency of loaded antenna structure improves slightly compare to reference antenna.
The design of a miniaturized slot antenna fed by microstrip line is proposed based on loop, slit and strip loading techniques. The antenna topologies considered are different combination of loops, slits and strips on top and bottom of the substrate. It is found that antenna topology with proper combination of slit and loop on top of substrate and strip on bottom of substrate provides 48.01% reduction in resonant frequency unlike only loop or slit on either end of slot antenna fed by coplanar waveguide (CPW). It is also observed that the radiation characteristics of loaded antenna are almost similar to that of unloaded antenna, with low cross polarization and -10 dB bandwidth of miniaturized antennas are also enhanced more than 60 % compare to the unloaded antenna topology in all the three cases.
The microstrip patch antenna (MPA) has been in use and has been studied extensively during the past three decades. This antenna, which consists of a metallic patch printed on a dielectric substrate over a ground plane, offers several advantages including ease of design and fabrication; low profile and planar structure; and ease of integration with circuit elements. The minimum dimension of a conventional MPA is in the order of half a wavelength. In recent years, with the advent of new standards and compact wireless devices, there has been a need to reduce the size of this type of antenna. This study discusses some of the principal techniques that have been reported in the literature to reduce the size of an MPA. These miniaturisation techniques include material loading, reshaping the antenna, shorting and folding, introducing slots and defects in the ground plane and the use of metamaterials. The major features and drawbacks of each of these approaches are highlighted in this study along with their effects on the antenna performance metrics.
The design of a miniaturized slot antenna with slit loading fed by the CPW line is proposed. It is seen that the loading slits can be located only on the feed side without degradation in cross-pol performance, un- like the microstrip-fed case. This releases the ground plane area above the slot for accommodating electronic circuitry and effectively reduces the an- tenna size. In addition, the resonant frequency in this case is reduced by a further 4.60%, compared to the slits on both sides. Another topology of the miniaturized antenna is investigated with the slits replaced by strips of metallization on the reverse side of the substrate, which leaves the ground plane area completely free. A high reduction in the slot resonant frequency is also observed in this case, with a reflector being used to increase the for- ward radiation.
In this paper the design and implementation of a quadrifilar helix antenna is presented where the four arms are 3D printed. The antenna structure is miniaturized by resorting to a combination of two approaches. The first approach is based on loading the tips of the four helical arms with circular conductive disks. The size and location of these elements directly affect the antenna’s operating frequency. The second miniaturization approach is based on incorporating an FR-4 dielectric material in the vacant space between the four arms of the quadrifilar helix. As a result, the length of the antenna is reduced by a ratio of 43%. The quadrifilar helix antenna is also designed on top of a ground plane with an optimized conical shape and topology. The antenna is fabricated partially using 3D printing additive technology, where measurements show great agreement with simulated results.
A size reduction technique of non-planar and planar antennas using a self-resonant topology is highlighted. The antennas considered are the dipole, the monopole and the slot radiator. The dipole below its resonant frequency is known to possess a capacitive reactance. It is shown that the inductive reactance of a loop can be used to match a below-resonant dipole similar to the inductive load offered by a metamaterial shell. The configuration reduces the resonant frequency of the dipole by 26.01%, causing the dipole to almost reach the electrically small limit. Despite the loaded dipole touching the electrically small limit, the antenna needs no matching networks, offers a high efficiency and exhibits a bandwidth better than the unperturbed dipole. The radiation pattern is also seen to be unaffected by the presence of the loops. The concept is also demonstrated for the size-reduction of a monopole and for a planar slot.
In this paper, new methods for further reducing the size and/or increasing the bandwidth (BW) of a class of miniaturized slot antennas are presented. This paper examines techniques such as parasitic coupling and inductive loading to achieve higher BW and further size reduction for this class of miniaturized slot antennas. The overall BW of a proposed double resonant antenna is shown to be increased by more than 94% compared with a single resonant antenna occupying the same area. The behavior of miniaturized slot antennas, loaded with series inductive elements along the radiating section is also examined. The inductive loads are constructed by two balanced short circuited slot lines placed on opposite sides of the radiating slot. These inductive loads can considerably reduce the antenna size at its resonance. Prototypes of a double resonant antenna at 850 MHz and inductively loaded miniaturized antennas at around 1 GHz are designed and tested. Finally the application of both methods in a dual band miniaturized antenna is presented. In all cases measured and simulated results show excellent agreement.
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 Ω line is obtained. For a prototype slot antenna with approximate dimensions of 0.05λ<sub>0</sub>×0.05λ<sub>0</sub> the impedance match is obtained, with a fairly high gain of -3dBi, for a very small ground plane (≈0.20λ<sub>0</sub>). Since there are neither polarization nor mismatch losses, the antenna efficiency is limited only by the dielectric and ohmic losses.
Three methods for the measurement of antenna efficiency are
evaluated: (1) the Wheeler cap method, (2) the radiometric method, and
(3) the directivity/gain method. Each of these methods was used to
measure the efficiency of four different printed antennas (three
microstrip patches with various feeds, and an eight-element series-fed
microstrip array). These methods and the experimental results which were
obtained are discussed
In this paper we study microstrip antenna miniaturization using partial filling of the antenna volume with dielectric materials. An analytical expression is derived for the quality factor of an antenna loaded with a combination of two different materials. This expression can be used to optimize the filling pattern for the design that most efficiently retains the impedance bandwidth after size reduction. Qualitative design rules are given, and a miniaturization example is provided where the antenna performance is compared for different filling patterns. Results given by the analytical model are verified with numerical simulations and experiments. Key words: Microstrip antenna, miniaturization, partial filling, impedance bandwidth, quality factor.