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A rectangular dipolar patch is proposed for designing a UHF RFID tag antenna that is suitable for metal and dielectric surfaces. The proposed tag antenna has a very compact structure with a dimension of 46 mm × 15 mm × 1.7 mm. It consists of a circular matching loop surrounded by two highly capacitive loading radiating patches, creating an embedded structure that has a very small size. Two L-shaped slot lines are etched in the radiating patches for lengthening the electrical length of the radiating patches. The low-profile dipolar patch is capacitive in nature, and the inclusion of a circular matching loop is an effective way to make the tag antenna inductive to achieve good impedance matching with the microchip. Series of simulations have been performed to evaluate the characteristics of the proposed tag antenna. When measurement is done on dielectrics based on North America regulated Radiated Power (EIRP) of 4 W, the tag antenna is managed to radiate beyond 8.5 m, but it decreases to 2.5 m when being placed on metallic surfaces. A noteworthy fact is that the resonant frequency of the proposed tag antenna is preserved and is not greatly affected by the type of materials attached to it. To our best knowledge, the proposed tag is performing much better than other recently published tags for the same application, with a relatively simpler antenna structure.

The Proposed paper proposing a slotted microstrip patch antenna which is designed and simulated using a high-frequency structure simulator(HFSS) for 5G applications in cellular networks particularly at Ka-band. The frequency ranges for Ka-band is (26-40) GHz. The antenna is designed using a rectangular microstrip patch element with a feed line connected to a patch and source. To increase the gain multiple slots are designed in a patch. The patch and ground are made up of a metal surface and a substrate material act as a dielectric material between them. The Electrical length of antenna is 6.7mm. In this antenna), ROGERSRT/DUROID-5880(tm) is used having the dielectric constant value 2.2. The performance of the proposed design is evaluated based on return loss, VSWR, gain, and radiation pattern.

In this paper a novel design of microstrip patch antenna (MPA), which consists of two radiation patches and a transmission line, is presented to enlarge the frequency ratio (FR). The H-shaped antenna is fully analyzed under two resonant modes via transmission line model. It indicates that the FR among TM 10 and TM 30 can be entirely dominated by the electrical length and impedance ratios between radiating patches and transmission line. The width of the radiation patch is progressively enlarged to move the TM 30 further to TM 10 . The prototype antenna is designed, fabricated, and tested. Experiment results show that the antenna has achieved a maximum FR of 6.52, which ranges from 0. 89GHz to 5. 80GHz, while keeping low-cross polarization and stable radiation pattern.

This paper presents a compact reconfigurable 5G microstrip antenna based on monopole and switchable guide and reflector. The antenna is composed of regular rectangular patches, irregular ground patch and two symmetrical "L" shaped patches. The monopole antenna is constituted by the upper regular patch, and the electrical length of the radiation patch is controlled by four p-i-n diode switches, so as to realized the two different frequency bands of 3.3GHz-3.6GHz and 4.8GHz-5.0GHz in the communication system of 5G operators, and 2.4GHz in the ISM band. Then, the "L" shaped patch connected to the ground patch is controlled by the p-i-n diode switches to realize the free swith between the guide and the reflector. Therefore, the antenna can be reconstructed in six different radiation patterns on the basis of three different frequency bands. The dual-reconfigurable antenna with frequency and radiation pattern has great advantages in miniaturization, multifunctionalization and intelligentization of microwave devices, and has a good development space, suitable for missile satellites, unmanned vehicles, intelligent communications, etc.

In this paper, a new $L$ -band wide beam angle wide-band Vivaldi antenna is presented. To obtain a balance between the miniaturized size, the low-frequency and wide-band operation, as well as the narrow beam angle of the antenna, the structure of the traditional Vivaldi antenna was changed, and the end of the antenna curve slot is rounded to increase the electrical length and reduce the volume. In addition, the edge of the antenna radiation metal is slotted to increase the antenna beam angle. The results show that in the 1.01 GHz-2.37 GHz operating band, the antenna has good impedance matching and the reflection coefficient is lower than −10 dB. The antenna has a large beam angle with the - 1-dB beam angle larger than 50° and the −3-dB beam angle greater than 90°. The antenna measurement results are basically consistent with the simulation results.

This paper scrutinizes the miniaturization of a WLAN 2.45GHz microstrip antenna by adding slots on the radiating patch. Invariably the insertion of slots at edges increases the electrical length of the patch, which in turn shifts the resonating frequency towards the left side. After the shift, by miniaturizing the dimensions of patch antenna the resonating frequency is repeatedly centered at 2.45GHz. The conventional antenna is having dimensions $38\text{mm}\times 50\text{mm}\times 1.6\text{mm}$ . This antenna achieves reflection coefficient, gain, and radiation efficiency of −18.86dB, 2.33dBi, and 63.69%, respectively at 2.45 GHz. The antenna with three slots is having dimensions $8.75\text{mm}\times 31.5\text{mm}\times 1.6\text{mn}$ . This antenna achieves reflection coefficient, gain, and radiation efficiency of −23.11dB, −7.85dBi, and 10.65%, respectively at 2.45 GHz. This work concludes that whenever slots are inserted along the edges of the radiating patch then dimensions can be reduced at a cost of reduced gain and radiation efficiency. The innovated miniaturized antenna alliances with slots permit coordination with Wi-Fi application devices. The proposed antenna is fabricated, and the simulated results are verified. A good agreement is observed between simulation and measurement.

The approach in this book is historical and practical. It covers basic designs in more detail than other microstrip antenna books that tend to skip important electrical properties and implementation aspects of these types of antennas. Examples include: quarter-wave patch, quarter by quarter patch, detailed design method for rectangular circularly polarized patch, the use of the TM11 (linear and broadside CP), TM21 (monopole CP pattern) and TM02 (monopole linear) circular patch modes in designs, dual-band antenna designs which allow for independent dual-band frequencies. Limits on broadband matching are discussed. The appendix contains useful simple matching approaches, design details (gain, matching, sidelobes) of the little-studied omnidirectional microstrip antenna (OMA), limits and properties of common single and dual band Planar Inverted F Antenna (PIFA) antenna designs. The second edition has numerous additions to the earlier text which will make the concepts presented clearer. New cavity model analysis equations of circular polarization bandwidth, axial ratio bandwidth and power fraction bandwidth have been included. The section on omnidirectional microstrip antennas is expanded with further design options and analysis. This is also true of the section on Planar Inverted F (PIFA) antennas. The discovery and description of the fictious resonance mode of a microstrip slot antenna has been added to that section. Appendix A, on microstrip antenna substrates has been expanded to provide more detail on the types of substrate and their composition. This is often neglected in other texts. An appendix on elementary impedance matching techniques has been added as these methods have proven useful in my industrial work.

A novel dual-band antenna and a triple-band monopole antenna were developed and fabricated on an Al2O3 ceramic substrate with a thickness of 0.4 mm. An L-shaped electrode structure with two branches of different lengths was designed for the antenna with two resonant frequencies, and a W-shaped structure with triple branches of different lengths was designed for the antenna with three resonant frequencies. The two antennas had simple structures, and the resonant frequency could be easily adjusted by changing the length of each branch. A stub was added to both antennas at the input microstrip line to control the input impendence, which gave the antennas better radiation (S11) properties. For the L-shaped antenna, the designed dual resonant frequencies were 2.4 and 3.5 GHz and for the W-shaped antenna, the designed triple resonant frequencies were 2.4, 3.5, and 5.7 GHz. The lengths of the radiation lines, the length of the ground plane, and the length between the tuning stub and the two radiation lines were used as design parameters. Different design parameters were changed to determine how this would affect the antennas’ characteristics. We found that the different parameters had large effects on the return loss (S11) value, and that stub length had a large effect on the resonant frequencies and return loss values.

A design approach to a novel wideband circular sector patch antenna is proposed. Design guidelines are laid down based on an approximate 1.5-wavelength, multimode magnetic dipole, and the cavity model. Then, the flared angle of the circular sector patch and the corresponding usable resonant modes for wideband radiation are determined. It is demonstrated that the resonant TM4/3,1 and the TM8/3,1 modes within a 270° circular sector patch radiator can be simultaneously excited, perturbed, and employed to form a wideband unidirectional radiation characteristic with two resonances. Prototype antennas are designed and fabricated to experimentally validate the dual-resonant wideband property on a single-layered substrate. It is further demonstrated that the antenna designed on a 5-mm-thick air substrate exhibits an available radiation bandwidth (ARB) of 14.5%, while the printed one designed on a 2-mm-thick modified Teflon substrate exhibits an ARB of 6.5%. It is evidently validated that the proposed approach can be employed to effectively enhance the operational bandwidth of microstrip patch antennas without increasing antenna profile, inquiring multiple radiators or employing reactance compensation techniques.

The theory of characteristic modes (TCM) for PEC bodies is showing great promise and application in the analysis, design, and placement of antennas. Its use for input impedance estimation, however, is still largely dependent on the idealized delta-gap model. Because TCM depends on all conductors, even feed structures, care must be taken for certain classes of antennas if estimating input impedance; probe-fed microstrip patch antennas (MSAs) are one example. In this paper, two different coaxial probe feed models are developed to estimate the input impedance of thin, arbitrarily shaped, air-dielectric MSAs using TCM. Their accuracy is compared with experimental results for a case study of an L-shaped MSA. Results show the importance of including all metal structures, including feeds, in TCM analyses.

This paper proposes a design for a dual-band microstrip loop antenna with an electromagnetically coupled feed for frequency-insensitive reactance variations. The antenna consists of two microstrip loops that are coupled to each other, and the ratio of the electric and magnetic coupling strengths is adjusted to lower the reactance slope. To demonstrate the suitability of the proposed feeding mechanism, antenna characteristics are measured in a full-anechoic chamber, and its operating principle is interpreted from a circuit standpoint. The results prove that the proposed structure exhibits a frequency-insensitive behavior without a significant gain reduction in the presence of strong mutual coupling.

A wide-boom, microstrip-fed planar bidirectional log-periodic (LP) antenna is proposed and improvements in its impedance match, radiation, and thermal performances are demonstrated. The boom width of each arm is increased by moving its virtual apexes into the other arm while preserving the small flare angle and self-complementarity. This modification widens the ground plane for the microstrip feed line and results in enhanced impedance match and gain. In addition, electrothermal multi physics analysis demonstrates that the wide-boom mitigates hot spots logarithmically developed on LP’s active regions. The impedance and far-field measurements show that the fabricated antenna achieves VSWR ≤ 2 and flat gain around 5 dBi over a decade bandwidth. A non contact thermal imaging system is used to measure temperature response of the antenna under a ~5 W input power over 1.71–1.85 GHz range. The measured temperature images correlate well with the multi physics simulations, therefore validating the conclusions obtained via electrothermal analysis.

A broadband dual circularly polarized (CP) planar monopole antenna is presented in this communication. The antenna is fed by dual orthogonal microstrip lines for polarization diversity. Circular polarization is achieved with a modified ground-plane structure and the isolation between the ports is improved by extending a protruded strip between the feed lines. L-shaped strips (LSSs) and inverted LSSs are designed along the radiating edges of the monopole. The combination of these two strips maximizes the axial ratio (AR) bandwidth, when they are placed $\lambda _{g}$ /4 apart at center frequency of the CP band. This principle is verified by fabricating the prototype on a 1-mm-thick FR4 substrate with 32 mm $\times32$ mm lateral dimension. From the experimental results, it is observed that the 3-dB AR bandwidth of the proposed antenna is 80.7% (3.74–8.8 GHz). The gain, return loss, and port isolation are higher than 1, 10, and 20 dB, respectively, within the CP band.

A semicircle arc projection is introduced to miniaturize the patch in circular patch microstrip antennas. The idea has been inspired from the effectiveness of a cuboid ridge in size reduction of a rectangular patch microstrip antenna. A prototype of the proposed antenna together with a prototype of a conventional circular patch antenna has been fabricated and measured. The two antennas are compared, and the results are presented and discussed. A parametric study is also carried out on the characteristics of the arc projection.

This letter presents a specific design of an ultra-wideband (UWB) microstrip monopole antenna of dimensions 35 × 25 × 1.6 mm3 realised on FR4 substrate. The UWB performance from 3.1 to 16.3 GHz is achieved with return-loss better than 10 dB. To achieve UWB performance, a quarter circular patch with tapered microstrip feed line has been used. This antenna has compact and simple structure suitable for fabrication and integration with microwave integrated circuits (MIC). Effect of varying geometric parameters on return-loss has been studied using Ansoft High Frequency Structure Simulator (HFSS) software. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:225–229, 2017

The applications of wearable medical devices are increasing day by day. They are now becoming an essential part of everyday human life starting from smart watch, smart phone to smart home. The main component of recent technology like the Internet of Things is the wearable devices. Inherently antenna is the essential part for all communicative devices. This paper focuses on antenna design which can be useful for wearable devices. Since they operate in close proximate to the human body, the radiation pattern, frequency of operation and power requirement of the designed antenna must be properly controlled. There are inherently some high frequency hazards of wearable devices which cannot be eliminated and the size of antenna is inversely proportional to frequency. Hence to compensate for these two contradictory requirements fractal designs are introduced, where the antenna can operate at relatively low frequency by essentially increasing the electrical length due to fractal structure. This paper presents the performance analysis or comparison of different iterations of antenna when fractal designs are introduced. The antenna operates around 5.8 GHz, which is a recommended frequency band for wearable devices by Federal Communications Commission (FCC). A high return loss is achieved which in turn indicates a measure of forward power propagation. The antenna is fabricated with FR4 substrate.

A simple dual-band antenna for MICS (402–405 MHz) and GPS (1570–1580 MHz) bands is developed and discussed in this paper. The effective shunt inductance property of shorting pin and effective electrical length property of slot is used on a conventional circular patch antenna (CPA) to reduce the resonant frequency of the modes (TM 11 and TM21). A single shorting pin is placed at the periphery to drop down the resonance frequencies. After that 12 equal rectangular slots are incorporated along the circumference of a 24 mm radius circular patch for further reduction hence, the size of the antenna is reduced by 94.73% in compared to the conventional CPA. The measured impedance bandwidth for MICS and GPS band is about 8.9% (384-420 MHz) and 3.17% (1.55-1.6 GHz) respectively. The simulated 3-dB axial ratio bandwidth is about 6.21% (390-415 MHz) for MICS band and 1.9% (1.56-1.59 GHz) for GPS band. This antenna can be very useful for real-time data transmission and tracking the dynamic location of human body, especially for elderly persons. The 50 mm x 50 mm x 1.6 mm proposed antenna is fabricated and measured to validate the simulated results and it shows good agreement.

A triangular-cavity-cascaded antenna is proposed and analyzed for wideband applications. By alternatively and periodically shorting a metallic plate on its edges with small slices, isosceles-triangular field patterns are generated and cascaded for wideband antenna design. Synchronous electric edge fields which contribute to radiation occupy almost all the areas of both sides of the plate. Compared with a typical microstrip antenna with a rectangular cavity, the triangular-cavity-cascaded antenna is a relatively open structure with less shorting boundary around. As a result, the quality factor is smaller, and the impedance bandwidth is wider. In order to prove the design strategy, a 1-D cascaded antenna with $1 \times 5$ triangular cavities and a 2-D cascaded antenna with $2 \times 5$ triangular cavities are fabricated and tested. Experimental results show that the impedance bandwidths of 1-D and 2-D antennas are 35.66% and 21.43%, while the peak gains are 13.27 and 16.47 dBi, respectively.

A compact 4-channel multiple-input–multiple-output (MIMO) microstrip antenna integrated with inverted U-shaped microstrip resonators and line resonators is presented at 5.25 GHz frequency band (WLAN band). Microstrip resonators have been introduced for reduction of mutual coupling between the closely spaced antenna elements. A distance of 0.5 λ is kept between adjacent patch elements, in order to achieve compactness of the MIMO structure. The simulation results show that the introduction of resonators of electrical length 2 λ g ( λ g = guided wave length) between antenna elements leads to suppression of mutual coupling by 44 dB at resonance frequency between the horizontal antenna elements. If line resonators of optimized length 22.1 mm (0.8 λ g ) are introduced, then each of them suppresses the mutual coupling between the vertical elements by more than 35 dB at resonance. The length, width and distance between two arms of the inverted U-shaped resonator have been optimized to achieve minimum mutual coupling. The antenna with a compact structure based on the design has a peak gain of 10.54 dBi and a band width of 250 MHz. The antennas have been fabricated, measured and a good agreement between simulation and measured results are observed.

A microfluidically reconfigured wideband frequency-tunable liquid-metal monopole antenna is presented. The antenna operation relies on continuous moving of the liquid-metal volume over the capacitively coupled microstrip line feed network with a micropump unit. To maximize the capacitive coupling at the feed point, the antenna is realized by bonding microfluidic channel molds prepared in polydimethylsiloxane (PDMS) polymer with 1-mil-thick liquid crystal polymer (LCP) substrate. The concept is demonstrated through the design and experimentation of a 4:1 frequency-tunable monopole antenna that operates from 1.29 to 5.17 GHz. The presented monopole antenna can also be utilized as an element to form wideband frequency-tunable high-gain antenna apertures without necessitating any additional micropump units. This is accomplished by resorting to strategically meandered or interconnected microfluidic channels. This concept is demonstrated through the design and experimentation of a $4 \times 1$ microfluidically controlled monopole array capable of providing 2:1 frequency tuning range from 2.5 to 5 GHz.

A novel approach to the design of a 1-D CRLH leaky-wave antenna has been proposed in which the frequency range of beam scanning can be adjusted without the change of unit cell’s physical length. The presented antenna is based on a unit cell composed of series capacitor connected in cascade with four sections of transmission lines and two symmetrically located transmission-line stubs. The unique feature of such a unit cell is that the phase constant’s slope vs. frequency and the resulting scanning bandwidth can be adjusted by controlling the characteristic impedance and the electrical length of the open-ended transmission-line stubs while all other parameters are fixed. The theoretical investigation as well as experimental results of the developed antenna operating at 2.5 GHz are shown, proving the correctness of the described design technique.

The design of an electronically steerable wideband planar traveling-wave antenna is presented. The proposed antenna has a very simple structure based on a microstrip line loaded with several radiating elements and phase shifters between them. The phase shifters are based on tunable capacitances, in order to perform a continuous phase shift between the radiating elements and control the main beam direction. The radiating elements are complementary strip slots that have a very broad impedance bandwidth, thus allowing the antenna to have two different modes of operation: maintaining the main lobe direction over a significant bandwidth, 1.71–2.17 GHz, and performing a main beam scanning over this bandwidth with a maximum angle range of $-45^{\circ}$ to 45° at 2 GHz.

compact size low profile microstrip-fed crossed monopole antenna for ultra wideband communication is presented. The impedance bandwidth of a microstrip crossed monopole antenna has increased with a suitable dimension of ground plane and rectangular patch. The aim of this paper is to improved bandwidth and return loss of a Crossed Monopole Microstrip patch antenna and study the effect of antenna and ground dimension length (L), width (W) and substrate parameters relative dielectric constant, substrate thickness on radiation parameters of bandwidth. Low dielectric constant substrates are generally preferred for maximum radiation. The crossed monopole shows the return loss of -10dB over ultra wideband frequency range (3.3 - 13.6 GHz) while maintain the stability in radiation pattern. The simulation software (CST) obtains the effect of the parameter on the performance of the antenna.

Microstrip patches and dielectric resonators (DRs) are two low-profile variants of modern microwave and wireless antennas. However, the DR antenna (DRA) is relatively new and still passing through the stages of development. Both variants are quite similar in terms of performance and characteristics. This article focuses on a meaningful comparative study where we have considered all commonly used feed mechanisms such as coaxial probe, microstrip line, and rectangular aperture for both antennas operating near the same frequency. Circular geometry, i.e., cylindrical DRA (CDRA) and circular microstrip patch antenna (CMPA), have been chosen, and a systematic investigation based on thorough experiments has been executed. Multiple sets of prototypes have been fabricated and measured at 4 GHz. All available data have been furnished and compared, indicating relative advantages and disadvantages. This comparative study should provide qualitative and quantitative instructions to a designer for choosing the right element and corresponding feed based on design requirement and feasibility.

A crossover maintains signal integrity when transmission lines overlap. In this paper, a microstrip patch is used to design the overlapping region thus providing desired isolation and transmission between desired ports. Square and Circular patch configurations for crossovers are analysed using ANSYS HFSS. The basic microstrip patch is further modified by introducing fractals enhancing the electrical length and improving the crossover characteristics.

The cavity model is extended to analyze a dualprobe-feed circular microstrip patch antenna for both differential and single-ended operations. Particular emphasis is given to the impedance characteristics in order to understand the relationship between the differential and single-ended input impedances. It is shown that the differential input resistance is four times of the single-ended input resistance at the resonant frequency of the fundamental mode.

In this paper, a new compact coplanar waveguide (CPW) ultrawideband (UWB) antenna with an electronically tunable notched band is proposed for an overlay onto cognitive radio (CR) systems. The proposed antenna utilized a rectangular microstrip resonator in the bottom layer to create a single notched band and to realize tunability and miniaturization using varactors. The center frequency of the notched band can be electronically tuned by changing the effective electrical length of the microstrip resonator, which is achieved by employing two varactor diodes at the resonator edges. Moreover, the simple biasing of the varactor diodes has a small effect on the antenna performance. Experimental results show that the proposed antenna can selectively have a band notch over a continuous operating band about 1.44 GHz from 4.77 to 6.21 GHz to prevent the interference to the primary users that are operating in this band such as the WLAN (5.15-5.35 GHz; 5.725-5.825 GHz) and the WiMAX (5.25- 5.825 GHz). Good agreement is found between the simulated and the measured data.

New modified 2 × 2 and 3 × 3 series-fed patch antenna arrays with beam-steering capability are designed and fabricated for 28-GHz millimeter-wave applications. In the designs, the patches are connected to each other continuously and in symmetric 2-D format using the high-impedance microstrip lines. In the first design, 3-D beam-scanning range of ± 25° and good radiation and impedance characteristics were attained by using only one phase shifter. In the second one, a new mechanism is introduced to reduce the number of the feed ports and the related phase shifters (from default number 2 N to the reduced number N + 1 in the serial feed (here N = 3) and then the cost, complexity, and size of the design. Here, good scanning performance of a range of ± 20°, acceptable sidelobe level, and gain of 15.6 dB are obtained. These features allow to use additional integrated circuits to improve the gain and performance. A comparison to the conventional array without modification is done. The measured and simulated results and discussions are presented.

A stub-loaded microstrip patch antenna with reconfigurability in both frequency and polarization is presented. Using 12 varactors with two independent voltages, reconfigurability is achieved in a fractional bandwidth of around 40% while allowing selection between circular polarization (CP) with both rotating senses and linear polarization (LP). The design is optimized based on an analytical model, which significantly speeds up the process while yielding reasonably accurate predictions. For illustration of the concept, an antenna is designed, optimized, and manufactured for reconfigurable operation in the 2.4–3.6 GHz frequency range. A good agreement between simulations and measurements is obtained which validates the proposed method. A full reconfigurability is demonstrated in the operation band with the ability to both tune the antenna to a given frequency and select a polarization state among left-hand or right-hand CP or various states of LP.

This communication presents a comprehensive numerical analysis of single microstrip antenna and antennas array in spherically layered media, using the method of moments (MoM). The curvilinear Rao–Wilton–Glisson (CRWG) triangular basis functions are employed to simulate the equivalent current on the antenna surface. First, the dyadic Green’s functions using Debye potential are deduced. Then, their efficient computation procedures are carried out to improve calculation efficiency. Finally, the characteristic basis function method is employed to save memory and calculation time by reducing dimension of the impedance matrix. The results of this study are in good agreement with those of the FEKO software, and they show that the method proposed in this communication is more efficient than FEKO in the analysis process.

A T slit Koch fractal compact MIMO antenna with a microstrip line feed is presented. The proposed fractal increases the electrical length thus reduces the overall dimensions of regular antenna for a specified frequency of operation, creating a miniaturized configuration. The T slit is proposed for isolation enhancement and two identical antenna elements are orthogonally placed with a distance O.2SAo to exhibit polarization diversity and high isolation in a compact planar MIMO antenna. The proposed antenna with 3rd order T slit Koch fractal MIMO antenna operates at 1.lGHz. The antenna has Envelope Correlation Coefficient (ECC) lesser than 0.0002 and diversity gain around 9.9dB. Modeling, simulation and experiments are presented; it confirms that the proposed antenna exhibits high isolation, polarization diversity and well defined radiation performance over the operating frequency band.

Microstrip antennas are widely used in civilian applications such as mobile communications, as well as in military applications, because of their small volume, light weight, and the ease of their mass production. Recently, the total size of wireless systems has been reduced, due to the miniaturization of wireless devices. However, since antenna size is determined by the wavelength of operation, it is difficult to miniaturize this element. In this paper, we describe miniaturization techniques based on structural modification of a microstrip, and antennas based on these modifications. Five miniaturization techniques are discussed: corrugation, perturbation, iris, folded, and high dielectric methods. The corrugation technique creates a grating-type concave-convex structure that bends a conventional planar microstrip antenna. Miniaturization is achieved by increasing the electrical length of the radiating element. The perturbation technique is so called, as a perturbation effect is induced by constructing the end portion of a radiating element with strong electric field energy, in a depressed volume. With the iris technique for antenna miniaturization, a conductor plane or rod is attached inside the antenna, to increase the electrical length. The folded miniaturization technique combines the effects of the corrugation and the perturbation method. Finally, with the high dielectric method, the electrical permittivity of the dielectric is increased, to miniaturize the antenna.

The main objective of this work is to design selective frequency reconfigurable antenna. The reconfigurable antenna is one of important aspect in cognitive radio systems along with sensing antennas. The frequency reconfigurable antenna is designed using microstrip patch antenna having reconfigurable filter. Overall dimension of antenna is 26 mm × 28 mm. Reconfigurable filter consist of PIN diodes as switches. In total four PIN diodes are used at two different places. One above the substrate and other three are incorporated with horizontal slot created in ground plane. By varying the slot length and electrical length of patch using different switching condition, different resonant frequencies achieved without changing the size of the antenna. FR4 epoxy substrate is used having relative permittivity of 4.4+0.088i and 1.6mm thickness. Here, in this proposed antenna twelve reconfigurable frequencies are attained using eight switching condition. The frequency bands of the antenna are varied from 2.76 GHz to 8 GHz. The antenna operates in both single band mode as well as multi band mode by changing the state of the PIN diode. For each case reflection coefficient should maintain less than −10 dB throughout the operating frequency. Antenna analysis is done using software HFSS.

In this paper, a novel design of defected ground circular patch antenna using glass epoxy materials has been presented. The substrate of the intended antenna was prepared of glass epoxy, whereas patch and ground plane are made out of copper. Enhancement in the geometry is done by increasing the electrical length and volume without growing the size of the patch antenna. The simulations were accomplished using Computer Simulation Technology software and the association of measured and simulated results of anticipated antenna has been studied. Experimental and simulated outcome are in outstanding conformity.

Due to the importance that reconfigurable antennas have in modern designs of low-profile antennas, a comprehensive study of the impact of slot parameters on the resonant frequencies of a rectangular microstrip antenna (RMA) has been undertaken and the results have been presented here. The changes exhibited in the first three resonant frequencies were graphed with respect to the changes in the values of the specific slot parameter. The impact of the slot length, width, and the position was thoroughly documented. Following the computational results, a few models were selected for manufacturing and the measurements performed on them showed a good agreement with the computational results.

A reconfigurable microstrip antenna with a circularly polarized (CP) beam-scanning feature is proposed in this paper. Such feature is attained using a novel methodology that effectively tunes the electrical size of a patch antenna. The proposed antenna is a microstrip Yagi-Uda antenna consisting of two square patches. One patch is driven with two orthogonal feeds for CP operation, whereas the other patch is a parasitic one of tunable electrical size for beam scanning. The parasitic patch is loaded with a narrow square slot and four lumped varactors along with their dc biasing network to effectively tune its electrical size. Because the main beam direction is determined by the electrical size of the parasitic patch, electronic beam scanning is allowed by changing the capacitance value through the applied reverse dc biasing voltage. An antenna prototype has been fabricated for experimental validation. Operating at 2.45 GHz, the antenna performance shows a monotonic CP beam scanning that ranges from –36° to 3° with a 0.48–6.64 pF tuning capacitance. The achieved peak value for the realized gain is 8.1 dBic with 2.4-dB variation along the entire scanning range.

In the current study, the authors present a technique to characterise the permittivity and loss tangent of an antenna substrate. In this method, an error function is formulated with measured data and a set of simulation data on the antenna's impedance and bandwidth. Subsequently, a surrogate-based optimisation code is used to intelligently search for the substrate parameters that minimise the error function. The validity of the method is demonstrated by experiments on wearable patch antennas with felt substrates. The results show that the method is effective in retrieving the permittivity and loss tangent of the antenna substrate using the antenna itself as the test fixture. Thus, there is no need to prepare additional resonators or transmission-line fixtures as in conventional substrate characterisation methods.

This article presents the derivation of a closed form expression for input admittance of horizontal electric dipole over an ungrounded substrate using transmission line analogy. The derived expression is then used to calculate reflection coefficient of rectangular and circular printed monopole antenna (PMA) fed by a microstrip line. Analytical result for the reflection coefficient of both rectangular and circular PMA is verified using high frequency structure simulator (HFSS). For circular PMA, analytical, and simulated results are also compared with the measured results available in literature. Effect of the dimension and dielectric material on the antenna bandwidth is also studied and verified by HFSS. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1535–1538, 2015

This paper proposed a compact planar monopole antenna operating at 5 GHz (5.180–5.825 GHz) industrial, scientific and medical (ISM) radio band. The antenna constructed with 20 mm × 12 mm radiating element and 25 mm square of the ground plane in FR4 substrate provided −10 dB bandwidth of 1 GHz (5.4–6.4 GHz). To improve the bandwidth, parasitic elements are added with the monopole antenna. A capacitive feed is also incorporated in the design. It observed that the proposed antenna with parasitic elements provides a larger impedance bandwidth of about 3 GHz (5.1–8.1 GHz), which is three-fold improvements over the one without parasitic patches. The prototype of the antenna that operates at 5.8 GHz frequency range is fabricated and characterized using a near-field measurement system. A good agreement is found between the simulation and measured results.

This letter highlights the potential of inkjet-printing on molded interconnect device technology for the realization of ultrawide band (UWB) antennas. Low-cost thermoplastic acrylonitrile butadiene styrene polycarbonate (ABS-PC) substrate is selected for its promising mechanical and thermal properties. First, electrical characterizations of bare ABS-PC are done using resonance cavity method and then the measurements of S-parameters of two 50 $~\Omega $ -CPW transmission lines, allow the extraction of both relative permittivity and RF losses. Inkjet printing of silver nano ink is used to fabricate those CPW lines on the top of a 2-mm-thick ABS-PC. The measurements show a relative substrate permittivity equal to 2.8 with conductive and dielectric losses of 19.5 dB/m and 2.4 dB/m at 2 GHz, respectively. Then, an UWB antenna based on a half circular disc monopole and a rectangular patch with two steps is designed and realized by inkjet on ABS-PC. This printed antenna provides a good impedance matching over the entire bandwidth of 3 GHz–13 GHz. Radiation pattern is omnidirectionnal in both E and H planes until 5 GHz and is deformed at higher frequencies due to the higher order modes.

New dual band miniaturized planar antennas loaded with 4-cell metamaterial is presented. The structure of the antenna consists of a coplanar waveguide at input, microstrip line, patch, metamaterial loaded substrate under patch, and back conductor. For simpler construction procedure, U-shaped and inverted U-shaped metamaterial loaded substrate under the patch is made in two layers. At the first band, these antennas work as a wideband monopole antenna with about 35% miniaturization compared to the folded monopole antenna, and at the second band as a wideband patch antenna with about 77% miniaturization compared to the conventional patch antenna.

We present a fully inkjet-printed novel wideband planar monopole antenna on thin packaging cardboard available in bulk for low-cost and environmentally-friendly mass manufacturing. We outline the characterization and the dielectric properties of the cardboard that are imperative for the successful design of an antenna on a paper-based substrate. To achieve highly conductive inkjet-printed pattern on the fibrous and porous cardboard, we deposit thin dielectric coating on the cardboard in the same inkjet process. The operation of the antenna is attested through simulations and measurements in the frequency range of 600–1500 MHz, where there are several strong radio signals present for ambient RF energy harvesting.

In this letter, a coplanar waveguide (CPW)-fed multiband bow-tie monopole antenna is proposed. This antenna can be easily designed to meet the requirement of multiple operating frequencies by using the proposed approach. Multiple bent monopoles, which correspond to different operating frequencies, are generated by etching slots of different lengths in a bow-tie patch. The length of each bent monopole is determined under the quarter wavelength resonance condition. Each frequency band can be easily satisfied for the broadband character because the bow-tie patch can be treated as a broadband impedance-matching structure. This study demonstrates a triple-band slotted bow-tie monopole antenna for WLAN/WiMAX/LTE applications with bands of 2.4–2.7 GHz, 3.4–3.7 GHz, and 5.2–5.8 GHz. The size of the proposed antenna fabricated on a 0.8 mm-thick FR4 substrate with a dielectric constant of 4.2 without considering the ground plane size is only $19.5 \times 9.0~\hbox{mm}^{2}$ . The good agreement between the simulation results and the measurement validates the proposed design approach.

A traditional microstrip antenna is capable of exhibiting good dual-band operation via slotting a complementary codirectional split resonant ring (CCSRR) unit on the rectangular radiating patch. Thanks to the advantage of low mutual coupling between the co-directional ring-slots in such a complementary co-directional split resonant ring unit, the antenna's operating frequency band, which originates from the complementary co-directional split resonant ring's resonance, is significantly expanded with the addition of more co-directional ring-slots. Antennas comprised of zero, a single, dual, and triple complementary co-directional split resonant rings were designed, fabricated, measured, and comprehensively compared. According to our investigation, besides operating in their inherent TM100 modes, the proposed antennas have the advantages of providing a lower and much wider operating range than that in the TM100 mode. This is especially more than a 9% impedance bandwidth, even with such a low profile (only 0.0316λ0 in height). More importantly, uniformly good radiation characteristics, including excellent broadside main beams with high polarization purity, and large front-to-back ratios (FTBRs), were achieved in both frequency ranges, on the whole.

As one of the efficient structures for soft body armor, the three-dimensional (3D) woven structure has relatively good properties. In this study, the concept of conformal microstrip antennas integrated into the 3D woven structure is proposed, which is anticipated for application in the modern wireless communication. For comparison, the microstrip antennas with the copper foil patch and copper yarn patch are both fabricated. The return losses of the antennas show that both of the antennas have adequate values with the resonant frequencies in the L band range. The main beam level and the gain of the copper yarn patch antenna are lower than those of the copper foil patch antenna, mainly due to the relatively low electrical conductivity of the patch. Under certain curvatures, the return loss and radiation pattern of the curved antenna are not significantly different from those of the planar one, indicating good conformability of this type of antenna.

In this paper we have investigated printed circular disc monopole antenna, which is basically printed microstrip antenna with etched ground plane for ultra-wideband (UWB) applications. In particular we have simulated circular disc monopole antenna with etched ground plane. Simple rectangular microstrip line is used for feeding the printed monopole antenna and which is having impedance of 50 Ω. This designed circular disc UWB monopole antenna works well for the whole UWB frequency band 3.1---10.6 GHz.

This communication presents antennas that incorporate self-folding polymer substrates that transform planar, two-dimensional structures into three-dimensional antennas when exposed to a light source. Pre-strained polystyrene sheets supporting a patterned copper foil form the light-activated structures. Black ink that is inkjet printed on the polymer substrate selectively absorbs light and controls the shape of the transformation. This approach represents a simple method to reconfigure the shape of an antenna and a hands-free method to assemble 3D antennas from many of the conventional methods that are used to pattern 2D metal foils. We demonstrate and characterize two embodiments that highlight this concept: a monopole antenna that transforms from a conventional microstrip transmission line and a microstrip patch antenna that converts within seconds into a monopole antenna.