Showing papers in "Iet Microwaves Antennas & Propagation in 2011"

Review of substrate-integrated waveguide circuits and antennas

Abstract: Substrate-integrated waveguide (SIW) technology represents an emerging and very promising candidate for the development of circuits and components operating in the microwave and millimetre-wave region. SIW structures are generally fabricated by using two rows of conducting cylinders or slots embedded in a dielectric substrate that connects two parallel metal plates, and permit the implementation of classical rectangular waveguide components in planar form, along with printed circuitry, active devices and antennas. This study aims to provide an overview of the recent advances in the modelling, design and technological implementation of SIW structures and components.

Design and experimental verification of ridge gap waveguide in bed of nails for parallel-plate mode suppression

Abstract: This study describes the design and experimental verification of the ridge gap waveguide, appearing in the gap between parallel metal plates. One of the plates has a texture in the form of a wave-guiding metal ridge surrounded by metal posts. The latter posts, referred to as a pin surface or bed of nails, are designed to give a stopband for the normal parallel-plate modes between 10 and 23 GHz. The hardware demonstrator includes two 90 bends and two capacitive coupled coaxial transitions enabling measurements with a vector network analyser (VNA). The measured results verify the large bandwidth and low losses of the quasi-transverse electromagnetic (TEM) mode propagating along the guiding ridge, and that 90 bends can be designed in the same way as for microstrip lines. The demonstrator is designed for use around 15 GHz. Still, the ridge gap waveguide is more advantageous for frequencies above 30 GHz, because it can be realised entirely from metal using milling or moulding, and there are no requirements for conducting joints between the two plates that otherwise is a problem when realising conventional hollow waveguides.

Numerical studies of bandwidth of parallel-plate cut-off realised by a bed of nails, corrugations and mushroom-type electromagnetic bandgap for use in gap waveguides

Abstract: Recently it has been shown that so-called gap waveguides can be generated in the gap between parallel metal plates The gap waveguides are formed by metal ridges or strips along which local waves propagate, and parallel plate modes are prohibited from propagating by providing one of the surfaces with a texture that generates an artificial magnetic conductor (AMC) or an electromagnetic bandgap (EBG) surface on both sides of the ridges or strips The bandwidth of the gap waveguide is determined by the cut-off bandwidth of a parallel-plate waveguide where one surface has such a texture (and no ridges or strips) This paper studies the bandwidths (or stop bands) of such parallel-plate cut-offs when the AMC or EBG is realised by a metal pin surface, corrugations or a mushroom surface It is shown that cut-off bandwidths of up to 4:1 are potentially available, and thereby similar bandwidths should be achievable also for gap waveguides

Dual-band matching technique based on dual-characteristic impedance transformers for dual-band power amplifiers design

Abstract: This study demonstrates a novel matching network synthesis technique that matches any arbitrary reflection coefficient seen by the active device at two uncorrelated frequencies to the standard 50 load The proposed matching network is fully transmission line based and, hence, can be used in high-power applications at higher frequencies Unlike previously reported dual-band matching techniques, this work proposes and discusses various ways to achieve realisable solutions for arbitrary frequency ratios that account for fabrication limitations The proposed synthesis approach is validated with the design and fabrication of a 10 W gallium nitride (GaN)-based class-AB amplifier for code division multiple access and Worldwide Interoperability for Microwave Access applications at 1960 and 3500 MHz The amplifier has 598 and 551 drain efficiencies at saturation in the first and second bands, respectively

Genetic algorithm (GA)-enhanced almost difference set (ADS)-based approach for array thinning

Abstract: This study proposes a genetic algorithm (GA)-enhanced almost difference set (ADS)-based methodology to design thinned linear arrays with low-peak sidelobe levels (PSLs). The method allows one to overcome the limitations of the standard ADS approach in terms of flexibility and performances. The numerical validation, carried out in the far-field and for narrow-band signals, points out that with affordable computational efforts it is possible to design array arrangements that outperform standard ADS-based designs as well as standard GA approaches.

Mutual coupling suppression in microstrip array using defected ground structure

Abstract: A defected ground structure (DGS) is used to suppress mutual coupling between elements in a microstrip array and eliminate the scan blindness in an infinite phased array. Two kinds of DGSs, namely back-to-back U-shaped and dumbbell-shaped DGSs, are analysed and compared. The analysis indicates that the back-to-back U-shaped DGS is better at suppressing propagation of surface waves in microstrip substrate. A two-element microstrip array with back-to-back U-shaped DGS is designed and the array characteristics against different element distances are studied. The results show that the degree of the mutual coupling suppression is increased when the element distance is reduced. However, compared with the traditional array, a higher gain and lower side lobes are obtained when a larger element spacing is selected. The scan blindness of an infinite microstrip phased array in E-plane is studied by simulation, and the calculation demonstrates that the scan blindness can be eliminated by applying a back-to-back U-shaped DGS to the infinite phased array.

Flexible ultra-wideband polarisation diversity antenna with band-notch function

Abstract: A CPW-fed polarisation diversity monopole antenna on a flexible PET film for ultra-wideband (UWB) systems is proposed. The antenna consists of two heptagonal monopoles that are orthogonally and symmetrically aligned to have extended ground planes. The antenna is able to cover the entire UWB bandwidth from 3.1 to 10.6 GHz and shows a good isolation of less than 20 dB at each port over the entire UWB bandwidth. Also, it has a band-notch function to avoid overlap with the 5 GHz wireless local area network band. It can be easily mounted on a conformal shape, because it is fabricated on a PET film that is flexible enough to be mounted on a curved surface. Both the time-domain and frequency-domain characteristics of the antenna have been investigated by using the normalised antenna transfer function. From the results, it is observed that the proposed antenna can support polarisation diversity for UWB communications.

Synthesis of multiple output coupled resonator circuits using coupling matrix optimisation

Abstract: Coupled resonator circuits are the basis for the design of many bandpass microwave filters. Design techniques used for two-port coupled resonator circuits are extended here to multiple output circuits such as power dividers and diplexers. The design approach is based on synthesis of coupling matrix for multiple coupled resonators with multiple outputs using gradient-based optimisation. It allows the synthesis of power dividers with arbitrary power division, as well as diplexers and multiplexers with novel topologies. Since there is no need to use separate energy distribution networks such as circulators, manifolds or other junctions, the components can be miniaturised. An X-band unequal power divider and diplexer have been designed and realised using waveguide cavity resonators to confirm the new design methodology.

Hybrid ultrawideband dielectric resonator antenna and band-notched designs

Abstract: A novel dielectric resonator antenna (DRA) is proposed for ultrawideband (UWB) applications, where a simple rectangular dielectric resonator is excited by a bevel-shaped patch connected to a coplanar waveguide (CPW) feeding line. It is found that the bandwidth of the resonant modes can be expanded by using a CPW-fed ground and bevel-shaped patch, and thus a UWB performance can be achieved. Experimental and numerical results were carried out, showing a good agreement. The measured results demonstrate that the proposed DRA achieves an impedance bandwidth more than 3:1, covering the frequency range from 3.1 to 10.6 GHz, which is suitable for UWB applications. Furthermore, to minimise the potential interferences between the UWB system and narrowband systems, such as world interpretability for microwave access and WLAN, UWB DRAs with single band-notched and dual band-notched characteristics were designed, fabricated and measured. The measurement results show good performances in terms of VSWR, antenna gain and radiation pattern. With these features, the proposed antennas are expected to be good candidates in various UWB systems.

Design and fabrication of ultra-low cost radio frequency identification antennas and tags exploiting paper substrates and inkjet printing technology

Abstract: This work deals with the design and fabrication of antennas for radio frequency identification (RFID) tag devices operating in the low microwave frequency range. Paper substrate material and inkjet printing process have been used to guarantee mechanical flexibility and ultra-low production costs of the antenna. A new antenna design methodology has been developed with the purpose to minimise the amount of both substrate material and conductive ink. The first goal is achieved by reducing, for a given frequency, the antenna size. The second goal, instead, is pursued by studying the surface current density distribution along the antenna and removing the metal material where such a current density is negligible. The above methodology has been applied to several antennas designs ranging from a windshield sticker tag to an RFID-SAW antenna. Moreover a 3.5 GHz crossed-dipole tag, based on the frequency-doubling mechanism, is reported along with a possible modification to enable wireless sensing. The experimental characterisation of these prototypes validates the proposed design methodology opening, in the mean time, the possibility for ultra-low cost mass production of RFID tag devices based on paper materials.

Ultra-wideband statistical propagation channel model for implant sensors in the human chest

Abstract: Implant medical wireless sensors for monitoring physiological parameters, automatic drug provision, and so on represent a new promising healthcare technology. Inherent characteristics of ultra-wideband (UWB) radio make this technology highly suitable for the wireless interface of implant sensors. A communication channel model is essential for developing these wireless systems. However, there are currently few models describing the radio propagation inside the human body. To address this problem, a statistical model is presented for UWB propagation channels inside the human chest in the 1-6 GHz frequency range. The proposed statistical model is developed from numerical simulations using a heterogeneous anatomical model that includes the frequency-dependent dielectric properties of different human tissues. Mathematical formulas for the computation of path loss, scattering and the statistical implementation of the channel impulse response at different depths inside the chest are described. Two typical depths for implanted sensors in the chest, namely 20 and 80 mm are analysed in detail. Average path loss of approximately 20 and 50 dB is observed in each case, respectively. Moreover, the channel exhibits little time dispersion with a root-mean-square delay spread below 1 ns in both cases. These results aim at facilitating the tasks associated with the design of in-body medical communication systems.

Reconfigurable front-end antennas for cognitive radio applications

Abstract: This study presents new antenna schemes suitable for cognitive radio communications. The antenna structures consist of a ultra wide band (UWB) sensing antenna, and a frequency reconfigurable communicating antenna both incorporated into the same substrate. Two different techniques to achieve the required frequency agility are proposed. The first one is based on a rotational motion of the radiating patch whereas the second is based on optical switching. The importance of these techniques is that no bias lines are needed as is seen in the case of RF MEMs, PIN diodes and lumped elements. Prototype antennas were fabricated and a good agreement was observed between the simulated and the measured data.

Design of a salisbury screen absorber using frequency selective surfaces to improve bandwidth and angular stability performance

Abstract: A new design method that greatly enhances the reflectivity bandwidth and angular stability beyond what is possible with a simple Salisbury screen is described. The performance improvement is obtained from a frequency selective surface (FSS) which is sandwiched between the outermost 377 Ω/square resistive sheet and the ground plane. This is designed to generate additional reflection nulls at two predetermined frequencies by selecting the size of the two unequal length printed dipoles in each unit cell. A multiband Salisbury screen is realised by adjusting the reflection phase of the FSS to position one null above and the other below the inherent absorption band of the structure. Alternatively by incorporating resistive elements midway on the dipoles, it is shown that the three absorption bands can be merged to create a structure with a -10 dB reflectivity bandwidth which is 52% larger and relatively insensitive to incident angle compared to a classical Salisbury screen having the same thickness. CST Microwave Studio was used to optimise the reflectivity performance and simulate the radar backscatter from the structure. The numerical results are shown to be in close agreement with bistatic measurements for incident angles up to 40° over the frequency range 5.4-18 GHz.

Multivariate gamma-gamma distribution with exponential correlation and its applications in radio frequency and optical wireless communications

Abstract: In this study, the multivariate gamma-gamma (G-G) distribution with exponential correlation is introduced and studied. Rapidly convergent infinite series representations are derived for the joint G-G probability density, cumulative distribution and moment generating functions. Based on these formulas, the performance of radio frequency wireless systems with diversity reception in the presence of composite multipath and shadow fading is analysed. Furthermore, the performance of single-input-multiple-output free space optical communication systems impaired by atmospheric turbulence is investigated. The correctness of the proposed analysis is demonstrated through various numerically evaluated results compared with equivalent computer simulation ones.

Multiband-integrated antenna/artificial magnetic conductor

Abstract: An artificial magnetic conductor (AMC)-based multiband low-profile antenna for vehicle applications is designed, simulated and measured in this study. The AMC is a simple dual band structure, constructed on a 3.2 mm-thick FR-4 (e r =4.4) board, with the reflection phase and surface wave bandgaps in the 2.0 and 5.8 GHz ranges. A wideband printed circular disc monopole antenna uses this dual-band AMC as a ground plane resulting in a low-profile, multiband and platform-tolerant antenna system. The operating frequency bands covered are GPS (1.57542 GHz), DCS (1.710-1.880 GHz), PCS (1.850-1.990 GHz), UMTS (1.925-2.175 GHz), WLAN (2.4-2.485 GHz), WiFi (5.15-5.825 GHz) and V2X (5.76-5.84 GHz) using a -10 dB reflection coefficient criterion. It is demonstrated that the antenna gain increases significantly when the AMC is used over a large metal ground plane for the antenna.

Design of non-uniform circular antenna arrays using biogeography-based optimisation

Abstract: Biogeography-based optimisation (BBO) is employed for the optimisation of non-uniform circular antenna arrays. In BBO, the problem solutions are represented as islands and the sharing of features between solutions corresponds to immigration and emigration between the islands. The scheme of BBO is employed to find out an optimal set of weights and antenna element separations to provide a radiation pattern with maximum side lobe level (SLL) reduction with the constraint of a fixed major lobe beam width. The capability of BBO is demonstrated by taking different sizes of antennas. The results show that the design of non-uniform circular antenna arrays using the BBO algorithm offers a SLL reduction better than that obtained using genetic algorithms, particle swarm optimisation and simulated annealing.

Micromachined W-band waveguide and filter with two embedded H-plane bends

Abstract: A micromachined W-band through waveguide together with a passband filter embedded with a pair of H-plane bends is presented here. The novel design of the bend enabled direct and accurate connection between the micromachined circuit and standard waveguide flanges. The devices were fabricated using thick SU-8 photoresist technology. They were constructed with six gold- or silver-coated SU-8 layers, each of a thickness of 0.635 mm. These layers were then bonded on top of each other to form the waveguide and filter. A measured average insertion loss of 0.5 dB or 0.0278 dB/mm has been achieved by the 18 mm long through waveguide, and the return loss is better than 18.8 dB in the whole W-band. The asymmetrical capacitive irises coupled filter shows a -3 dB bandwidth of 8.61 GHz at a central frequency of 88.47 GHz. The passband insertion loss was measured to be between 0.97 and 1.1 dB and reflection loss is better than 15 dB. This performance demonstrates the potential of employing this micromachining and multi-layered technique to fabricate millimetre and submillimetre waveguide components.

Compact metamaterial zeroth-order resonator bandpass filter for a UHF band and its stopband improvement by transmission zeros

Abstract: A microstrip bandpass filter for a UHF 900 MHz band is significantly miniaturised and its performance is enhanced using metamaterial (MTM) zeroth order resonator (ZOR) characteristics. Firstly, the authors propose that each of the resonators for a bandpass filter is implemented by a one-cell ZOR, and the coupling between neighbouring different ZORs is controlled to meet the primary goal on the bandpass filtering in the form of a sequential coupling mechanism. Secondly, this MTM ZOR filter is suggested to have transmission zeros (TZs) owing to source load coupling to improve the isolation from other wireless communication bands. The first and second proposed filters are less than one-sixth of the conventional filters in terms of size, and they present lower insertion loss and return loss in the passband and higher isolation in the stopband owing to the TZs, as verified by simulation and measurement. In addition, the MTM properties are verified with a dispersion diagram and the no-phase variation electric field distribution over the ZOR by a 3D EM simulation.

Mutual coupling suppression in closely spaced antennas

Abstract: A technique to significantly reduce the mutual coupling between closely spaced antennas operating at the same frequency band is presented. The method comprises the use of two ground-plane side walls that are erected vertically next to adjacent antennas. The side walls are defected with a lattice pattern of slots to form a defected wall structure (DWS). In addition, the adjacent antennas sharing a common ground plane are separated with a pair of slits in the ground plane. This technique implemented on closely packed antenna suppresses surface waves in the antenna's operation band and can provide isolation of 56'dB, which was achieved with a DWS loaded with mushroom-shape slots separating two microstrip patch antennas. In this case, the inter-antenna spacing (centre to centre) is 0.272' o and ground-plane size is 0.606 × 0.370 × o 2 . Also investigated is the number of DWS slot loadings on isolation between adjacent antennas. Furthermore, the proposed technique is shown to substantially reduce mutual coupling between planar inverted-F antennas (PIFAs) and monopoles. The measured results validate the proposed technique and vindicate the simulation results.

Design and realisation of an electrically small Huygens source for circular polarisation

Abstract: The authors study the possibilities of realising circularly polarised Huygens source antennas combining electric and magnetic dipoles. The required combinations of dipoles are first studied analytically. Radiating elements comprising both electric and magnetic dipoles in a single element, namely, chiral particles, are then chosen as a way to realise the required dipole radiators. The use of elements that have equally strong electric and magnetic dipoles in a single element greatly simplifies the realisation and feeding of these antennas. The designed antennas are studied numerically and finally the radiation properties of the antennas are verified with measurements. The numerical and experimental results confirm that the antennas have radiation characteristics similar to a Huygens source.

Experimental studies on antenna miniaturisation using magneto-dielectric and dielectric materials

Abstract: Dielectric or magneto-dielectric materials can be used to miniaturise antennas, but there are many important parameters that must be considered when selecting which material to use. The authors discuss these figures of merit and a rigorous method to compare antennas with different material fillings. A meandered planar inverted-F antenna (PIFA) loaded with magneto-dielectric and dielectric materials is presented as an example antenna for testing. The magneto-dielectric material used is composed of mylar substrate and Fe–SiO2 sheets. Measurement results for the permeability of the material are presented. The radiation mechanism of the meandered PIFA is studied, and the proper position for dielectric and magneto-dielectric filling is discussed and identified. Miniaturisation by commercial dielectric and the presented magneto-dielectric fillings is measured and compared at the same resonance frequency using the radiation quality factor as the figure of merit. It is seen, that the antenna can benefit from the magneto-dielectric filling material in terms of the radiation quality factor only if the placement of the antenna filling is carefully selected.

Sparse multiple-input multiple-output arrays for high-resolution near-field ultra-wideband imaging

Abstract: This study investigates the utilisation of a multiple-input multiple-output (MIMO) array technique for high-resolution near-field ultra-wideband (UWB) imaging. Using this technique, a classical array can be replaced with an MIMO array with a similar resolution and beam pattern but using a smaller number of elements. A deterministic approach to factorise a desired effective array topology into topologies of transmit and receive sub-arrays is suggested. Based on it, an MIMO array design procedure is proposed. A few examples of linear array topologies are suggested and their performances in the near-field are compared for different values of the operational bandwidth. The experimental results verify the correctness and effectiveness of the proposed design procedure for UWB near-field imaging.

Application of fractal binary tree slot to design and construct a dual band-notch CPW-ground-fed ultra-wide band antenna

Abstract: A compact dual band-notch ultra-wide band (UWB) antenna with a co-planar waveguide (CPW)-ground-feed is presented. A desired band-notch antenna is achieved by etching a narrowband dual resonance fractal binary tree into the radiating element of an existing UWB antenna. The new antenna reduces interference from UWB in the wireless local area network (WLAN) bands by attenuation of the measured return. The built prototypes have a compact size of 16×22 mm2 including the ground plane. This miniature size also delivers advantageous radiation patterns with good mono-polar characteristics across the UWB band. For this design the gain is attenuated within the desired WLAN bands. The maximum suppression obtained for the stops at 5.65 and 9.9 GHz are −13.1 and 7.2 dB, respectively.

Fractal unit cells of increased phasing range and low slopes for single-layer microstrip reflectarrays

Abstract: This study reports investigations into phase characteristics of a unit cell of a single-layer microstrip reflectarray exploiting fractal geometries. The aim is to have the phase range larger than 360° accompanied by a smaller slope of the reflected wave phase as a function of the elements' size. These are required to achieve a wide operational bandwidth and a smaller sensitivity to manufacturing errors. To achieve this goal, multi-resonance fractal elements are investigated. It is shown that sliced patches of square and circular shapes as well as multiple rings printed on a thick substrate can offer slower phase slopes while maintaining phase ranges exceeding 360°. The achieved ranges and slopes of these elements are comparable with those of double-stacked patches printed on the equivalent low permittivity dielectric substrate. Choosing suitable dimensions and scaling factors of these elements, the phase characteristic can be made approximately a linear function of their size.

Miniature microstrip-fed ultra-wideband printed monopole antenna with a partial ground plane structure

Abstract: A new microstrip-fed planar monopole antenna is presented for ultra-wideband (UWB) communication systems. The antenna structure consists of a dome-topped, bowl-shaped patch with a truncated ground plane structure. The ground plane is predominately tapered and includes a notch below the feed-line in the vicinity of the patch. The effects of dimensional parameters on the performance of the antenna have been investigated through a parametric study. Current density distribution on the antenna was also computed to gain a better insight of its behaviour. The antenna performance is validated through measurement, including its radiation patterns. The measured impedance bandwidth of the proposed antenna for |S 11 ||| |10|dB is 10.35|GHz (2.65|13.0|GHz), constituting 132| impedance bandwidth. The fabricated antenna has a compact size of 18|20|1.6|mm 3 . Additional features that make the antenna a suitable candidate for UWB systems are its simple configuration, compactness and low fabrication cost.

Constrained parameter extraction for microwave design optimisation using implicit space mapping

Abstract: To date, space mapping remains one of the most efficient design optimisation methodologies in microwave engineering. Still, its performance depends on the underlying surrogate model, in particular, its approximation and generalisation capabilities. By proper selection of the space mapping transformations and their parameters, a trade-off between these can be obtained. Often, this is done by trial and error that may lead to excessive computational overhead and poor quality of the optimisation outcome. In this study, an adaptively constrained parameter extraction is introduced. Based on convergence results for space mapping algorithms, it allows us to automatically find the approximation-generalisation trade-off through the adjustment of the surrogate model parameter space. Improved performance of the space mapping algorithm is obtained both in terms of convergence properties and the quality of the optimised design. Algorithm convergence is additionally improved by constraining the surrogate optimisation process. The authors' technique is validated using several microwave design problems.

Adaptive nulling in time-modulated linear arrays with minimum power losses

Abstract: The synthesis of adaptive time-modulated linear arrays is dealt with by means of an innovative strategy, in which a particle swarm optimiser is used to reconfigure the pulse sequence controlling the static element excitations, as well as the least significant bits of digital phase shifters to maximise the signal-to-interference-plus-noise ratio at the receiver. The reduction of the power content of sideband radiation generated by the periodic on-off commutation of switches is addressed by customising to non-isotropic sources a very effective analytic relationship. A set of selected results is reported and discussed to show the advantages and limitations of the proposed approach. Comparisons with previously published results are also presented. "This paper is a postprint of a paper submitted to and accepted for publication in IET Microwaves, Antennas & Propagation and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library: http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5697293"

Reduced log-periodic dipole antenna using a cylindrical-hat cover

Abstract: A technique to decrease the size of log-periodic dipole array (LPDA) antennas employing inductive loads on its elements is introduced. This technique consists of adding a short-circuited cylindrical hat cover at the end of each arm of the antenna. Simulation and measurement results show that the total area, if considered as a trapezoid, of a fabricated LPDA antenna, based on the proposed technique, is approximately 50% smaller than the size area of a reference antenna using a conventional technique. The parameters of the reduced antenna are slightly modified, preserving the bandwidth, impedance, polarisation and radiation pattern shape. The drawback of this technique is the small reduction of gain, from 7.5 dB for the conventional antenna to 6.4 dB for the reduced prototype in the middle operation band.

Synthesis of microstrip lowpass filter using defected ground structures

Abstract: This study reports a systematic synthesis process to design higher-order defected ground structures (DGS)-based lowpass filters (LPF) with Chebyshev and Butterworth responses on any useful substrate in the range ɛr=2.2−12.9, h=0.6−2 mm. The existing circuit models are re-examined and closed-form expressions are presented to compute the area of the DGS slot-heads for the given inductance. The present design method improves the design of the existing DGS-based LPF reported by several investigators – both in terms of the electrical performances and reduction in length up to 57.8%. The improvement in sharpness of the transition is up to 16 dB/GHz. The improvement in the 20 dB rejection bandwidth is up to 4.5 GHz. The group delay response of Butterworth LPF is better than that of Chebyshev LPF. However, length of Chebyshev LPF is small when compared with that of Butterworth LPF. The study also presents the design results of the ultra-wideband DGS-type LPF – at the cut-off frequencies of 5, 7.5 and 12 GHz.

Stretchable dipole antenna for body area networks at 2.45 GHz

Abstract: A stretchable antenna is proposed for body area networks operating at 2.45 GHz. The topology of the antenna is based on a meandered dipole with a parasitic arm, which has an impedance with a dual-resonance behaviour. The antenna impedance is optimised for the specific radio-frequency integrated circuit where it will be connected to. This topology has been implemented on two stretchable technologies using thermoplastic poly-urethane and silicone as substrates. A simple stretching model has also been proposed for design purposes and it has been validated through measurements. Simulations based on this model and real stretching measurements have shown the potential of the structure for obtaining a wideband match in stretched conditions, with optimised designs achieving a reflection coefficient lower than −10 dB up to 20% stretching. On-body simulations and measurements have also been done, which indicate that practical values of reflection coefficient and radiation efficiency can be achieved with a separation of few millimetres between the antenna and the human body.