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Showing papers in "Iet Microwaves Antennas & Propagation in 2015"


Journal ArticleDOI
TL;DR: This study discusses some of the principal techniques that have been reported in the literature to reduce the size of an MPA, which consist of a metallic patch printed on a dielectric substrate over a ground plane and the use of metamaterials.
Abstract: 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.

89 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented an effective method to model, analyse and design graphene metasurface-based terahertz (THz) absorbers using equivalent circuit model approach.
Abstract: This study presents an effective method to model, analyse and design graphene metasurface-based terahertz (THz) absorbers using equivalent circuit model approach. Broadband and tunable absorbers consisting of graphene metasurface and metal-backed dielectric layer have been designed based on the formulas derived from this approach and verified by full-wave electromagnetic simulation. By properly constructing the graphene metasurface, broadband absorption over 70% fraction bandwidth has been achieved, showing that graphene can provide a wideband absorption in the low THz spectrum. Furthermore, tunability of the graphene metasurface has also been investigated. It is demonstrated that the absorption peak frequencies can be tuned while maintaining the peak absorption unchanged, which is highly desirable for THz sensing applications.

87 citations


Journal ArticleDOI
TL;DR: In this paper, a compact multiple-input multiple-output (MIMO) antenna with a small size of 26 × 55 mm 2 and low correlation has been proposed for the ultra-wideband (UWB) applications operating over a frequency range of 3.1-12.3 GHz at �10 dB.
Abstract: A compact multiple-input multiple-output (MIMO) antenna with a small size of 26 × 55 mm 2 and low correlation has been proposed for the ultra-wide-band (UWB) applications operating over a frequency range of 3.1-12.3 GHz at �10 dB. The MIMO antenna consists of two identical elements each of which has a planar radiator with microstrip-fed over half- sized ground plane. The antenna elements are placed orthogonally to achieve a good isolation between the two input ports. The antenna's characteristics such as the bandwidth, isolation, radiation pattern, peak gain and surface current distributions have been investigated. Moreover, diversity performance in terms of envelope correlation coefficient and mean effective gain has been analysed. Furthermore, a parametric study has been carried out to provide more design information. An arrangement with quad-elements has been designed for MIMO operations, as well. The simulation and measurement results show that the proposed antenna has an impedance bandwidth larger than the frequency range of UWB with low correlation and high diversity performance. The proposed MIMO antenna has been compared in detail with the previous works reported elsewhere in terms of antenna size, geometric complexity, bandwidth, mutual coupling and use of additional structure to obtain more isolation. From this point of views, the antenna is more preferable than other suggestions.

76 citations


Journal ArticleDOI
TL;DR: In this article, a compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492-1.518 GHz) is presented, where two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation.
Abstract: A compact circularly polarised (CP) microstrip antenna for mobile satellite communication band of India (1.492-1.518 GHz) is presented. Two asymmetric length rectangular shape slots, perpendicular to each other are printed on the circular patch for realisation of CP radiation. To improve the performance parameters of patch antenna such as axial ratio (AR) bandwidth, return loss bandwidth, radiation efficiency and so on a new technique of combination of fractal theory and defected ground structure (DGS) is proposed for the first time in design of CP antennas. 44.74% size reduction in patch size, enhancements of 62.73% in AR bandwidth, 70.74% in return loss bandwidth and 4.03% in radiation efficiency is achieved as compared with conventional patch antenna, after incorporation of Koch curve fractal DGS in the ground plane. The performance of the developed antenna has been compared with other available L-band planar antennas in the literature, and it is found that the developed structure is better one in many aspects. Laboratory prototype of the antenna is fabricated and experimentally measured for cross verifying the simulated results.

71 citations


Journal ArticleDOI
TL;DR: In this article, a tapered-slot ultra wideband (UWB) band-notched wearable antenna is presented, which covers the whole UWB frequency spectrum of 7.5 GHz ranging from 3.1 to 10.6 GHz.
Abstract: Design of a tapered-slot ultra wideband (UWB) band-notched wearable antenna is presented in this study. The antenna operation covers the whole UWB frequency spectrum of 7.5 GHz ranging from 3.1 to 10.6 GHz, while rejecting the wireless local area network operation at 5.25 GHz band. The performance of the antenna is analysed through simulations and validated through measurements. The antenna makes use of ultra-thin liquid crystal polymer (LCP) substrate. The presented return loss and radiation pattern results show that the antenna offers excellent performance in the UWB frequency band in free space. Use of the LCP substrate makes the antenna to efficiently mitigate the bending effects. Moreover, the antenna performs well in on-body configurations and its working is little affected in adversely hot and humid weather conditions. Furthermore, it offers good on-body communication link and pulse fidelity. These features make the proposed antenna design a well-suited choice for hand-held and wearable UWB applications.

63 citations


Journal ArticleDOI
TL;DR: In this article, a radiation pattern reconfigurable antenna designed using metasurface (MS) is proposed, which is composed of a planar semi-circular MS placed directly atop of the planar circular patch antenna with a diameter of 70 mm.
Abstract: A radiation pattern reconfigurable antenna designed using metasurface (MS) is proposed in this study. The pattern reconfigurable metasurfaced (PaRMS) antenna is composed of a planar semi-circular MS placed directly atop of a planar circular patch antenna with a diameter of 70 mm (1.2 λ 0 ), making it compact and low profile. The main-beam direction of the antenna has an angle of 32° from the boresight direction. By rotating the MS around the centre of the patch antenna, the antenna beam can be steered continuously. The PaRMS antenna is studied and designed to operate at around 5.5 GHz. To verify the results of simulation, the PaRMS antenna is fabricated and measured. Results show that the antenna has an operating bandwidth from 5.4 to 5.6 GHz and measured peak realised gain of 7.2 dBi.

57 citations


Journal ArticleDOI
TL;DR: In this paper, a broadband metamaterial absorber with octave bandwidth for practical applications is presented, which consists of simple geometrical patches placed diagonally on the top surface of the structure and exhibits broadband absorption response of 8.30 GHz from 6.86 to 15.16 GHz covering the entire X-band with more than 90% absorptivity.
Abstract: In this study, a broadband metamaterial absorber is presented with octave bandwidth for practical applications. The unit-cell of proposed absorber structure consists of simple geometrical patches placed diagonally on the top surface of the structure. The proposed structure exhibits broadband absorption response of 8.30 GHz from 6.86 to 15.16 GHz covering the entire X-band with more than 90% absorptivity. Three distinct absorption peaks at 7.24, 10.18 and 14.32 GHz have been observed in the absorption spectra. The roles of the geometrical parameters have been investigated to explain the principle of absorption. The structure is studied under oblique incidence for both transverse electric and transverse magnetic polarisations, where the broadband response holds good up to 45° incident angles in both the cases. Owing to the two-fold symmetry, the structure is sensitive to polarisation of the incident field exhibiting maximum absorption at 0° and 90° with no absorption taking place at 45° angle of polarisation. The structure is fabricated and the experimental results are in good agreement with the simulated responses. The proposed structure is very thin (~ λ /8.5 with respect to the centre frequency of the bandwidth) compared with the commercially available microwave absorbers.

54 citations


Journal ArticleDOI
TL;DR: In this paper, an all-textile higher-order mode circular patch antenna for on-body to onbody communications is proposed, which consists of a coaxially center-fed circular patch with two shorting vias to generate the TM 21 resonance mode for a monopole-like radiation characteristic.
Abstract: An all-textile higher order mode circular patch antenna for on-body to on-body communications is proposed. The proposed antenna is compact in size and consists of a coaxially centre-fed circular patch with two shorting vias to generate the TM 21 higher order resonance mode for a monopole-like radiation characteristic. The antenna is fabricated by using a conductive textile, conductive thread and a felt substrate. The bandwidth can fully cover the 2.45 GHz ISM band while achieving a low-profile configuration. The effects of antenna deformation because of bending and the human body are analysed when the antenna is placed on a two-thirds muscle-equivalent phantom and a full-scale human model. The performance of the antenna is minimally affected by antenna deformation and the human body because of the TM 21 higher order mode excitation and its monopole-like radiation pattern.

54 citations


Journal ArticleDOI
TL;DR: In this paper, a compact microstrip dual-band in-phase filtering power divider is presented to improve the frequency selectivity, a source-load cross coupling is introduced by placing input and output coupling lines closely.
Abstract: A compact microstrip dual-band in-phase filtering power divider is presented in this study The integrated two stub-loaded resonators are applied to realise the dual-band filtering response and compact size Based on the even–odd-mode analysis, an analytical model of the proposed power divider structure is presented To improve the frequency selectivity, a source-load cross coupling is introduced by placing input and output coupling lines closely A prototype of the dual-band in-phase filtering power divider centred at 35 and 5 GHz with 3 dB fractional bandwidth of 74 and 42% is designed, fabricated and measured The size of the fabricated power divider is 027λ g × 035 λ g The simulated and measured results are presented and show good agreement

52 citations


Journal ArticleDOI
TL;DR: In this paper, split ring resonators (SRR) have been used to provide a resonance close the resonance of the monopole antennas and the results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced.
Abstract: New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The results illustrate that by loading the conventional monopole antennas with an asymmetrical meander lines SRR, a lower resonance frequency mode can be excited. The dimensions of the SRR have been selected to provide a resonance close the resonance of the monopole antennas. The results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced. The length and width of the antennas are 25 × 10 − 2 λ 0 × 11 × 10 − 2 λ 0 and 25 × 10 − 2 λ 0 × 21 × 10 − 2 λ 0 at 4 GHz for monopole antennas, and 29 × 10 − 2 λ 0 × 21 × 10 − 2 λ 0 at 2.9 GHz for both monopole antennas loaded with SRR. For antennas without SRR loading, maximum of measured gains and efficiencies are 3.6 dBi and 78.5% for F-antenna, and 3.9 dBi and 80.2% for T-antenna, hence they appear at 5 GHz. For antennas with SRR loading, these parameters are 4 dBi and 81.2% for F-antenna, and 4.4 dBi and ∼83% for T-antenna, which appeared at 6 GHz. By implementing the meander lines SRR as a matching load on the monopole antennas, the resulted antennas cover the measured frequency bandwidths of 2.9–6.41 GHz and 2.6–6.6 GHz (75.4 and ∼87% fractional bandwidths), which are ∼2.4 and 2.11 times more than monopole antennas with an approximately same in size.

51 citations


Journal ArticleDOI
TL;DR: In this paper, a new compact multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna array is presented, which consists of two monopoles placed side by side at a distance of 4 mm.
Abstract: A new compact multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna array is presented. The antenna array initially consisted of two monopoles placed side by side at a distance of 4 mm. A strong mutual coupling was observed so the design was modified by rotating the second radiator at 90° at a distance of 1 mm. Wideband isolation is achieved by exploiting polarisation diversity of antenna elements. Simulation in HFSS and printed prototype results validate the high isolation, over 21 dB on the entire 2.5–12 GHz frequency range. A prototype was fabricated on a low loss substrate of Rogers TMM4 measuring 23 × 39.8 mm2. To evaluate the diversity performance, the envelope correlation coefficient was calculated resulting below −20 dB, thus ensuring good diversity performance. The compactness of the proposed UWB-MIMO design is finally compared against alternative solutions already present in the literature.

Journal ArticleDOI
TL;DR: In this paper, the effects of the dielectric layer between the water and the ground plane are studied and the results show that this layer has a crucial effect on the antenna resonant frequency and radiation efficiency.
Abstract: Water antennas are a special type of antennas and have attracted limited attention so far. In this study, a monopole water antenna with a dielectric layer is chosen as an example to study some less obvious characteristics of the water antenna. The resonant frequency, radiation efficiency and fractional bandwidth are of particular interest. Firstly, the effects of the dielectric layer between the water and the ground plane are studied. The results show that this layer has a crucial effect on the antenna resonant frequency and radiation efficiency. Secondly, the water with different conductivity is investigated. With different conductivity, the antenna may be regarded as a dielectric resonant antenna, a conducting antenna or their combination. Thirdly, a water antenna with a supporting structure is fabricated for validation. Measurements are conducted in an anechoic chamber and a reverberation chamber to evaluate its performance as a function of various parameters. Finally, the water temperature electromagnetic characteristics are investigated. Good agreements are achieved between the simulation and measurement results. It is shown that this type of antenna shows better performance than the conventional antenna in aspects such as broadband, cost, reconfigurability, transparency and it can be a promising candidate for a range of applications.

Journal ArticleDOI
TL;DR: In this article, a metamaterial-based antenna using the concept of composite right-left-handed transmission lines is presented, where the radiation cells layouts are based on L/F-shaped slits, so these slits are engraved on the radiation patches for establishing a seriescapacitor effect.
Abstract: This study presents a metamaterial-based antenna using the concept of composite right–left-handed transmission-lines. The radiation-cells layouts are based on L/F-shaped slits, so these slits are engraved on the radiation-patches for establishing a series-capacitor effect. Moreover, the radiation cells including the spirals and via-holes for the shunt-inductors implementation. By cascading the proper number of cells, the desired antennas for very/ultra-high frequency-bands are designed. The first-antenna with four L-shaped cells isconstructed on the Rogers_RO4003 substrate with thickness of 0.8 mm, so that each of cells occupies the size of 2.3 mm × 4.9 mm. This antenna covers the experimental-bandwidth of 0.2–1.8 GHz, which corresponds to 160% feasible-bandwidth. This antenna resonates at frequencies of 600–850–1200–1550 MHz, so highest gain and efficiency, happened at 1550 MHz, are 3.4 dBi and 88%. For improving the antenna performances, the second-antenna is modelled with one-cell more than first-antenna and with changing in the slit configuration to F-shape and increasing in the same substrate thickness to 1.6 mm. F-shaped antenna has size of 14.5 mm × 4.4 mm × 1.6 mm, covering a measured-bandwidth of 0.11–2.1 GHz with five resonance frequencies at 450–725–1150–1670–1900 MHz, which corresponds to 180.1% practical-bandwidth. Maximum of the measured gain and efficiency of antenna are 4.5 dBi and 95%, which occur at 1900 MHz.

Journal ArticleDOI
TL;DR: In this study, a far-field power pattern separation approach is proposed for the synthesis of directional modulation (DM) transmitter arrays and it is demonstrated how multi-beam DM transmitters can be synthesised via this approach.
Abstract: In this study, a far-field power pattern separation approach is proposed for the synthesis of directional modulation (DM) transmitter arrays. Separation into information patterns and interference patterns is enabled by far-field pattern null steering. Compared with other DM synthesis methods, for example, bit error rate-driven DM optimisation and orthogonal vector injection, the approach developed in this study facilitates manipulation of artificial interference spatial distributions. With such capability more interference power can be projected into those spatial directions most vulnerable to eavesdropping, that is, the information side lobes. In such a fashion, information leaked through radiation side lobes can be effectively mitigated in a transmitter power efficient manner. Furthermore, for the first time, the authors demonstrate how multi-beam DM transmitters can be synthesised via this approach.

Journal ArticleDOI
TL;DR: In this paper, an efficient near-field imaging system using miniaturized bowtie antennas is proposed for the 3D detection of breast tumours using radar-based set-up in the frequency range of 1.2-7 GHz.
Abstract: In this study, an efficient near-field imaging system using miniaturised bowtie antennas is proposed for the three-dimensional (3D) detection of breast tumours. To ensure good penetration and high resolution, a novel compact bowtie antenna is developed. The antenna features a high fractional bandwidth covering both low and high frequencies, while still small in size. A hemispherical array of 16 compact bowtie antennas is built and following a multistatic scenario, scattered signals from two breast phantoms with one and two embedded tumours inside are recorded. The radar-based set-up operates in the frequency range of 1.2–7 GHz. It is shown that the imaging system can successfully detect the tumour phantoms in 3D space.

Journal ArticleDOI
TL;DR: In this article, a printed elliptical nested fractal (planar) antenna for multiband operation is proposed, which is intended to function as the receptor element in radio-frequency energy harvesting applications.
Abstract: This study presents the design, optimisation, simulation and fabrication of a novel printed elliptical nested fractal (planar) antenna for multiband operation. The proposed antenna is intended to function as the receptor element in radio-frequency energy harvesting applications. The simple microstrip structure and the compact size of the antenna ease its fabrication and allow it to be integrated with other electronic circuitry. It consists of nested elliptical structures fed by 50 Ω microstrip line with complementary elliptical ground along with rectangular ground plane. The added Hilbert structures at both sides of the antenna feeding line on the top layer enhance its performance to operate in multi-frequency bands. This antenna exhibits good radiation and reflection characteristics at 910 MHz (global system of mobile (GSM 900)), 2.4 GHz (Bluetooth/wireless local area network), 3.2 GHz (Radiolocation, third generation (3G)), 3.8 GHz (for long-term evolution, 4G) and additional 5 GHz band (wireless fidelity signals). The overall dimension of antenna is 41 mm (width) × 44 mm (length) × 1.778 mm (thickness). To the best knowledge of the authors, this is the widest bandwidth antenna to be developed at these small dimensions covering major standards from 900 MHz up to 6 GHz for electromagnetic energy harvesting applications.

Journal ArticleDOI
TL;DR: In this paper, a transparent microstrip antenna with fluorine-doped tin oxide (FTO or SnO2:F) patch was used to reduce the conductor loss of the antenna and ameliorate antenna efficiency.
Abstract: Transparent microstrip antenna with fluorine-doped tin oxide (FTO or SnO2:F) patch is studied here. The authors make use of spray pyrolysis technique to deposit FTO transparent patch on a Pyrex glass substrate. The deposited FTO patches show high optical transmittance (about 80–90%) and low electrical surface resistance (as low as 7 Ω/□). Two transparent microstrip patch antennas (with conventional conductor as ground plane), which are fed by proximity coupling at 2.5 and 5 GHz resonance frequencies, are fabricated and their radiation properties are presented and compared with copper patch antenna counterparts. In order to reduce the conductor loss of the antenna and ameliorate antenna efficiency, thick substrates should be used. The 2.5 GHz antenna shows low efficiency and significant loss in transparent layer but the 5 GHz one shows 3.63 dBi maximum gain and only ∼0.83 dB degradation in comparison with the copper patch antenna.

Journal ArticleDOI
TL;DR: In this paper, a coplanar waveguide-fed monopole is loaded with a split-ring resonator and an inter-digital capacitor to achieve miniaturization and quad-band operation.
Abstract: In this study, a novel four-element multiple-input–multiple-output (MIMO) antenna having quad-band characteristics is proposed. A coplanar waveguide-fed monopole is loaded with a split-ring resonator and an inter-digital capacitor to achieve miniaturisation and quad-band operation. These quad-band elements are arranged properly to implement a four-element MIMO configuration which provides both spatial and pattern diversities. The achieved isolation performance is better than 20 dB. Measurement results confirm that the proposed MIMO antenna operates at 1.95, 2.39, 2.64 and 3.27 GHz with impedance bandwidths of 2.66, 6.57, 8.8 and 4.09%, respectively. The proposed antenna exhibits quasi-monopolar radiation pattern and measured envelope correlation coefficient <0.01 is obtained in all the operating bands. The proposed antenna can be useful for MIMO applications in global system of mobile/Bluetooth/wireless local area network/worldwide interoperability for microwave access operating bands.

Journal ArticleDOI
TL;DR: In this paper, the authors presented the design of switching techniques for dual-notched ultra-wideband antenna using switched defected microstrip structure band stop filter inserted in the microstrip feed line and a switched meandered slot etched in the radiation patch.
Abstract: This study presents the design of switching techniques for dual-notched ultra-wideband antenna. The dual band-notched frequencies are achieved by using switched defected microstrip structure band stop filter inserted in the microstrip feed line and a switched meandered slot etched in the radiation patch. The switching reconfiguration is accomplished by combining the two ideal switches to introduce a notch filter response to prevent the interference to the primary users operating in the middle and upper WiMAX wireless local area network bands. The proposed structure has four modes by controlling the two switches on and off. The proposed antenna has good matched impedance from 2.5 to 12 GHz with two notched bands from 3.3 to 3.8 GHz (middle WiMAX applications) and from 5.1 to 5.9 GHz (upper WiMAX applications). The antenna is fabricated and tested. Good agreement is achieved between the simulated and measured results.

Journal ArticleDOI
TL;DR: In this paper, a dual-reverse-arrow fractal (DRAF) was proposed to reduce the size of an equilateral-triangular patch antenna by combining two dual Koch fractals.
Abstract: A novel geometry called the dual-reverse-arrow fractal (DRAF) is introduced, which is the combination of two dual Koch fractals It is implemented on an equilateral-triangular patch antenna This structure has smaller dimensions compared to the rectangular structure and has wide applications in arrays to reduce their size Furthermore, the use of triangular elements in array leads to the decrease of side-lobe levels Four cases of the triangular patch are compared to show that the presented fractal geometry is effective in the miniaturisation of patch antenna and decreasing its resonance frequency, while the antenna bandwidth and efficiency are kept constant To increase the antenna efficiency, an air space is placed under the patch Finally, a portion of the corner of fractal triangle is cut to generate circular polarisation by proper positioning of the feed points The proposed DRAF antenna achieved 40% reduction in size compared to the similar triangular antenna The proposed DRAF geometry has potential applications in various radiating systems and microwave devices

Journal ArticleDOI
TL;DR: In this paper, a printed monopole ultra-wideband antenna with reduced ground plane effect is presented, where the ground plane dependence of the antenna is reduced by cutting a slot in the radiator, and then introducing a strip in the slot, to reduce the current distribution on the groundplane at a desired frequency.
Abstract: A printed monopole ultra-wideband antenna with reduced ground plane effect is presented The ground plane dependence of the antenna is reduced by cutting a slot in the radiator, and then introducing a strip in the slot, to reduce the current distribution on the ground plane at a desired frequency At this frequency, the impedance performance of the antenna is mainly affected by the monopole radiator, thus reducing the effect of the ground plane on the antenna Measurement results confirm that this approach works well and also show good far-field properties of the antenna The antenna is printed on a small FR4 substrate with an area of 25 mm2; it achieves an impedance bandwidth of 36 to over 11 GHz, and broadband ground plane effect suppression around the design frequency of 5 GHz

Journal ArticleDOI
TL;DR: In this article, a hybrid modeling approach based on geometrical and physical optics is adopted in order to efficiently analyse the multiple wave reflections occurring within the lens and to evaluate the relevant impact on the radiation properties of the antenna under analysis.
Abstract: A novel class of supershaped dielectric lens antennas, whose geometry is described by the three-dimensional (3D) Gielis' formula, is introduced and analysed. To this end, a hybrid modelling approach based on geometrical and physical optics is adopted in order to efficiently analyse the multiple wave reflections occurring within the lens and to evaluate the relevant impact on the radiation properties of the antenna under analysis. The developed modelling procedure has been validated by comparison with numerical results already reported in the literature and, afterwards, applied to the electromagnetic characterisation of Gielis' dielectric lens antennas with shaped radiation pattern. Furthermore, a dedicated optimisation algorithm based on quantum particle swarm optimisation has been developed for the synthesis of 3D supershaped lens antennas with single feed, as well as with beamforming capabilities.

Journal ArticleDOI
TL;DR: A compact, novel multi-mode, multi-band frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system, integrated with ultra-wideband (UWB) sensing antenna, is presented and can be used as a complete antenna platform for cognitive radio applications.
Abstract: A compact, novel multi-mode, multi-band frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system, integrated with ultra-wideband (UWB) sensing antenna, is presented. The developed model can be used as a complete antenna platform for cognitive radio applications. The antenna system is developed on a single substrate area of dimensions 65 × 120 mm 2 . The proposed sensing antenna is used to cover a wide range of frequency bands from 710 to 3600 MHz. The frequency reconfigurable dual-element MIMO antenna is integrated with P-type, intrinsic, N-type (PIN) diodes for frequency agility. Different modes of selection are used for the MIMO antenna system reconfigurability to support different wireless system standards. The proposed MIMO antenna configuration is used to cover various frequency bands from 755 to 3450 MHz. The complete system comprising the multi-band reconfigurable MIMO antennas and UWB sensing antenna for cognitive radio applications is proposed with a compact form factor.

Journal ArticleDOI
TL;DR: In this article, the authors introduce a methodology for low-cost simulation-driven design optimisation of highly miniaturised branch-line couplers (BLCs). The first stage of their design approach exploits fast concurrent optimization of geometrically dependent, but electromagnetically isolated cells that constitute a BLC.
Abstract: In this study, the authors introduce a methodology for low-cost simulation-driven design optimisation of highly miniaturised branch-line couplers (BLCs). The first stage of their design approach exploits fast concurrent optimisation of geometrically dependent, but electromagnetically isolated cells that constitute a BLC. The cross-coupling effects between the cells are taken into account in the second stage, where a surrogate-assisted fine-tuning procedure is executed. The tuning process is based on space-mapping-enhanced low-fidelity model of the entire BLC. The latter is constructed by cascading local response surface approximations (RSAs) of the BLC building blocks. The efficiency of their technique is demonstrated through the design of two compact BLCs. A considerable scale of miniaturisation has been achieved in both cases (83.7 and 87.4%, respectively), at the computational cost corresponding to a few EM simulations of the respective BLC. Comparison of numerical results with several surrogate-based design approaches as well as an experimental verification of the final designs are also provided.

Journal ArticleDOI
TL;DR: In this paper, a compact bandpass filter (BPF) with dual band-notch function for ultra wideband (UWB) applications is presented and discussed, where defected ground structure is used in order to improve the out-of-band performance of the filter.
Abstract: The procedure of attaining a compact bandpass filter (BPF) with dual band-notch function for ultra-wideband (UWB) applications is presented and discussed. In the proposed BPF, defected ground structure is used in order to improve the out-of-band performance of the filter. Also, four short-circuited bent stubs are employed in order to improve the selectivity of the filter at its cutoff frequencies. Dual band-notch function is added to the performance of the filter by coupling two short-circuited inverted T-shaped stubs to the filter main resonator. The fabricated filter satisfies well the demands of the Federal Communications Committee with two narrow band-notch functions at 5.5 and 8 GHz, which eliminates the interference of the UWB system with wireless local area network (WLAN) and satellite communication systems, respectively. The improved upper stop-band of the proposed filter with more than 20 dB attenuation level extends up to 20 GHz.

Journal ArticleDOI
TL;DR: In this paper, a compact ultra-wideband (UWB) bandpass filter with sharp rolloff, improved out-of-band performance and dual-band notch operation is presented and its design procedure is discussed.
Abstract: In this study, a compact ultra-wideband (UWB) bandpass filter (BPF) with sharp roll-off, improved out-of-band performance and dual-band-notch operation is presented and its design procedure is discussed. In the proposed structure, in order to reject the unwanted harmonic pass bands, a pair of modified cross-shaped coupled lines (CCLs) is implemented along the ports of the filter. Moreover, a pair of half-circle-shaped stubs and a stepped-impedance stub are loaded on the main resonator in order to obtain additional transmission zeros (TZs) which are controllable separately. Implementation of the CCLs and the stub loaded resonator (SLR) reduce the total size of the presented microstrip BPF. Besides, by extending and folding the upper coupled line of each CCLs and also through an open stub which is protruded inside a slot on the main resonator, dual-band-notch operation is added to the performance of the presented filter. The fabricated prototype has a small size and is capable to cover frequency band of 2.8–10.69 GHz with two band-notch functions at 4.9–5.4 and 7.83–8.25 GHz which suppresses the interference between UWB spectrum with wireless local area network (WLAN) and satellite communication frequency bands, respectively. The proposed filter has a compact size while showing good return loss and insertion loss characteristic in the frequency band of interest.

Journal ArticleDOI
TL;DR: In this paper, a coupled line doublet structure is proposed to improve the reflection coefficients of a quarter-wavelength transmission line between the input and through ports of the coupled line section.
Abstract: This study presents a novel approach to the design and implementation of transmission-type negative group delay (NGD) networks based on a coupled line doublet structure. To improve the reflection coefficients, a quarter-wavelength transmission line is connected between the input and through ports of a coupled line section. For the doublet structure, two coupled line sections are arranged in a symmetrical manner by connecting them back-to-back with the help of the quarter- wavelength through line. For the experimental demonstration, two planar NGD networks (unmatched and matched doublet NGD networks) are designed, simulated and measured at a centre frequency of 2.14 GHz. From the measurement, a group delay (GD) of −5.66 ns and signal attenuation (SA) of 18.78 dB were obtained in the case of an unmatched NGD network. Similarly, for the matched NGD case, a GD of −6.33 ns, SA of 20.69 dB and input/output return losses >29 dB were obtained at the centre frequency.

Journal ArticleDOI
TL;DR: In this paper, a beam steering array antenna composed of a broadband circularly polarised square slot antenna and a novel, Butler matrix feed network designed with a proposed broadband branch-line coupler is introduced.
Abstract: Among the other features, multiple beam antennas have the advantage of reduced multi-path fading and co-channel interference. Because of the outstanding features of the Butler matrices, they have been proposed extensively in recent years as feed networks of the antenna array applications such as broadband and circular polarisation. In this study, a beam steering array antenna composed of a broadband circularly polarised square slot antenna and a novel, Butler matrix feed network designed with a proposed broadband branch-line coupler is introduced. The results show that a compact and its improvements are discussed. In this study, a broadband double box coupler with impedance bandwidth over 5-7.4 GHz frequency and the phase error less than 3° is employed. Also the measured impedance bandwidth of the proposed beam steering array antenna is 39% (from 4.7 to 7 GHz). The minimum 3 dB axial ratio bandwidth between ports, support 4.55-6.7 GHz frequency range. The measured peak gain of the proposed array antenna is 10.1 dBic that could scan solid angle ~25 steradian.

Journal ArticleDOI
TL;DR: In this paper, a reconfigurable planar inverted-F antenna with a parasitic strip line for a hepta-band wireless wide area network (WWAN)/long term evolution (LTE) mobile handset is proposed.
Abstract: In this study, a reconfigurable planar inverted-F antenna (PIFA) with a parasitic strip line for a hepta-band wireless wide area network (WWAN)/long term evolution (LTE) mobile handset is proposed. The PIN diode is located between the end of the parasitic strip line and the protruded ground plane. Depending on the on/off-state of the PIN diode, the degree of coupling between the conventional PIFA and the parasitic line is controlled and the fundamental resonant frequency of the proposed antenna is adjusted. As a result, the fundamental resonant frequencies cover the (global system for mobile communication) GSM850 (824–894 MHz) and GSM900 (880–960 MHz) bands. By the parasitic strip line extended from the protruded ground plane, impedance matching at the higher-order modes (f 2 and f 3) is improved and the fourth resonant frequency f 4 is remarkably decreased. The high band of the antenna is formed by combining these three higher-order modes to cover the GSM1800 (1710–1880 MHz), GSM1900 (1850–1990 MHz), universal mobile telecommunication system (UMTS) (1920–2170 MHz), LTE2300 (2305–2400 MHz) and LTE2500 (2500–2690 MHz) bands.

Journal ArticleDOI
TL;DR: In this article, a comprehensive study of miniaturized broadband microstrip patch antennas for ultra-wideband applications is presented, which is composed of a folded-patch feed, a symmetric E-shaped edge, a U-shaped-slot patch and shorting pins.
Abstract: In this paper, a comprehensive study of miniaturised broadband microstrip patch antennas for ultra-wideband applications is presented. At first, design and analysis of a compact wideband basic antenna which is composed of a folded-patch feed, a symmetric E-shaped edge, a U-shaped-slot patch and shorting pins are studied and investigated. The measured −10 dB impedance bandwidth of the proposed basic antenna is about 92% in the frequency range 3.94–10.65 GHz. To explicitly demonstrate the mechanism of the bandwidth enhancement method, the equivalent transmission line model of the basic antenna is exhibited. This model contributes the effect of different parts used in the basic antenna structure in order to predict the broadband behaviour of it. Moreover, with the use of a V-shaped slot instead of the U-shaped slot on the patch, an improved antenna with a wider bandwidth in order to cover the frequency range from 4 to 14.4 GHz is obtained. This improved design introduces comparatively a simpler structure with considerable size reduction and an enhancement of 21% in impedance bandwidth compared with the basic antenna. Experimental investigations and detailed simulations based on the parametric study are performed to describe and optimise the broadband performance of the proposed designs.