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A re-configurable meta surface based linear to linear polarization converter is presented.

International audience; This paper describes the design and development of a highly directive planar end-fire array using arc dipoles as the array elements. The inter element spacing, shape, and size of the array elements are optimized for maximum directivity and gain. The array is printed on a substrate whose dimensions are also optimized for better performance. The overall length of the proposed six element array is 1.9λ, giving directivity and gain values as 12.0 dBi and 10.2 dB respectively at 5.8 GHz.

The performance of printed wideband antennas has to be optimized both in frequency and time domains, to qualify for UWB applications. This is especially true in multi-resonant antenna topologies where the excitation of different modes can change phase centers and radiation patterns with frequency. The study presented in this chapter intends to demonstrate the simulation and experimental design for the time domain characterization of UWB antennas. Modeling the antenna as a linear time-invariant system with transfer function and impulse response, distortion caused to a nanosecond pulse is analyzed. Two planar monopole antenna designs are considered for the comparative study: the SQMA and RMA. SQMA is a traditional CPW-fed monopole design with ground modifications for ultra wide-bandwidth. RMA is a rectangular CPW-fed monopole with an impedance transformer arrangement at the antenna feed. RMA maintains constant impedance over the entire UWB and contributes towards maintaining uniformity in the radiation patterns over the entire frequency band by its design. Transfer function measurements are performed for both the azimuthal and elevation planes and the impulse responses are deduced by performing IFFT. Parameters such as FWHM and ringing are computed from the impulse response for the performance comparison. To evaluate the influence of the antenna geometry on a transmitted/received pulse, the impulse responses are convoluted with a standard UWB pulse. The time-domain distortion for the designs is then compared by computing the Fidelity parameter.

Printed wideband antennas, if not optimised both in frequency and time domain, often fail to qualify for UWB applications. This is primarily observed in designs based on multiple resonances. The excitation of different modes causes variation in the position of the antenna phase centre and radiation patterns with frequency. In this paper, we propose a novel compact UWB antenna design with optimised resonances within the 3.1 – 10.6 GHz band. The design comprises of a rectangular CPW-fed monopole. The novelty in the design lies in the impedance transformer arrangement at the antenna feed which not only maintains constant impedance over the wide band but contributes towards maintaining uniformity in the radiation patterns over the frequency band. The proposed antenna is characterized, both in the frequency and time domain, confirming its suitability for UWB operation. The impedance bandwidth of the antenna is from 2.9-11.5GHz with an omni–directional radiation pattern over the full band, unlike most of the planar UWB antennas reported in literature whose pattern deteriorates particularly at the upper end of the band. It also exhibits appreciable polarization purity and radiation efficiency. The time domain parameters, Full Width Half Maxima (FWHM) and Ringing, are computed from the measured antenna transfer function. The computed Fidelity of the transmitted pulses indicates superior pulse handling capabilities. The antenna is suitable for commercial hand held devices as its PCB area is just 30 x 12mm2 when fabricated on the FR4 substrate with permittivity 4.4 and height 1.6mm.

A novel J shaped slot antenna for ultra-wide band (UWB) WiMedia is presented. The proposed antenna is designed using a microstrip to slot line cross transition on FR4 substrate with permittivity 4.4. Return loss of the antenna is from 2.8- 13GHz and occupies just 28x10 mm 2 on the PCB. Radiation patterns are stable and omni-directional. Antenna transfer function and impulse response are analyzed to study the pulse handling capability of the antenna.

A printed semi-elliptic monopole slot antenna for use in ultrawideband (UWB) communication systems is presented. The antenna features a coplanar waveguide signal strip terminated with a semi-elliptic stub and a modified ground plane to achieve wide bandwidth from 2.85-20 GHz. An exhaustive study of the radiation characteristics of this antenna in the frequency and time domains are presented. Design equations are derived and experimentally validated. Transient analysis indicates linear phase response and minimum dispersion to the transmitted pulse. The proposed radiator is omnidirectional with appreciable gain throughout the band.

Design of a compact dual frequency microstrip antenna is presented. The structure consists of a slotted circular patch with a dielectric superstrate. The superstrate,not only acts as a radome, but improves the bandwidth and lowers the resonant frequency also. The proposed design provides an overall size reduction of about 60% compared to an unslotted patch along with good efficiency,gain and bandwidth. The polarization planes at the two resonances are orthogonal and can be simultaneously excited using a coaxial feed. Parametric study of this configuration showed that the frequency ratio of the two resonances can be varied from 1.17 to 1.7 enabling its applications in the major wireless communication bands like AWS, DECT,PHS,Wi.Bro,ISM,and DMB. Design equations are also deduced for the proposed antenna and validated.

A novel compact planar ultra-wideband bevelled monopole for portable UWB systems is proposed. The antenna is CPW fed with an impedance transformer implemented along the length of the feed line. This in combination with the bevelled monopole–ground edges leads to a compact UWB antenna design confined to just 8×30 mm2. The proposed design fabricated on FR4 substrate (ɛr=4.4, thickness=1.6 mm) exhibits a wide impedance bandwidth of 8.4 GHz (3.0–11.4 GHz). The antenna measures a gain and radiation efficiency greater than 1.85 dBi and 81%, respectively, in the band of operation with omnidirectional radiation characteristics.

A compact wideband printed slot antenna, suitable for wireless local area network (WLAN) and satisfying the worldwide interoperability for microwave access (WiMAX) applications, is proposed here. The antenna is microstrip-fed and its structure is based on Koch fractal geometry where the resonance frequency of a conventional triangular slot antenna is lowered by applying Koch iterations. The antenna size inclusive of the ground plane is compact and has a wide operating bandwidth. The proposed second iteration Koch slot antenna operates from 2.33 to 6.19 GHz covering the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Design equations for the proposed antenna are developed and their validity is confirmed on different substrates and for different slot sizes.

A novel ultra-wideband (UWB) antenna consisting of a linear tapered slot in the ground plane and a microstrip to slotline transition is investigated. The antenna possesses a wide bandwidth from 2.95–14 GHz for |S11

Introduction: The universal serial-bus wireless (WUSB) combines the benefits of the USB with the convenience of wireless technology leading to data rates of 480 Mbit/s up to 3 m and of 110 Mbit/ su p to 10 m [1]. The WUSB is one of the most promising applications of ultra-wideband (UWB) technology and among the first to be commercially available for short-range and high-speed wireless interfaces. WUSB dongles replace the USB cables and deliver instant UWB connectivity for a wide range of devices such as printers, hubs and external hard drives. The dongles employ an on-board UWB antenna on printed circuit boards (PCBs) typically of 23 � 70 mm 2 sizes. Along with miniaturised size and omnidirectional radiation patterns, dongle antennas should be flexible in design with ground independence [2]. A microstrip-fed monopole antenna with reduced ground plane effects [3] and a bended plate monopole antenna [4] are some of the designs reported for WUSB dongle applications. The proposed antenna employs a near-rectangular slot which along with a tapered tuning stub exhibits a wide impedance bandwidth from 2.9 to 11 GHz. The width of the antenna is only 20 mm and is smaller than most of the slot antennas reported for UWB operations [5, 6]. Also, the antenna performance is observed to be unaffected by the PCB/ground length making the proposed design an ideal candidate for a WUSB dongle antenna. A coplanar waveguide (CPW) feed further ensures easy integration with the rest of the USB circuitry. The proposed antenna is successfully designed and experimentally verified. The antenna has excellent impedance matching, stable radiation patterns, and linear group delay over the entire UWB band along with good impulse response. Antenna design: Fig. 1a shows the geometry of the proposed antenna and its optimised dimensions. The antenna consists of a CPW-fed tapered tuning stub along with a near-rectangular aperture etched out from the ground plane of a PCB. The CPW feed is designed for 50 V on FR4 substrate with 1r ¼ 4.4 and thickness h ¼ 1.6 mm. Since the feed and the ground are on the same plane, a substrate with singlesided metallisation is used, making the antenna easy and cost-effective to manufacture.

A microstrip-fed planar ultra-wideband monopole antenna with band-notch characteristics is proposed. The antenna size is compact (18 30 mm) and operates over an extremely wide band of 3 16 GHz. The proposed design consists of an inverted cone as the radiating patch and a tapered ground plane. Wideband matching is obtained by properly shaping the ground. A pair of symmetrically placed quarter wave slot resonators is embedded in the ground plane for rejecting the 5 6 GHz WLAN band. Results indicate a stable and omnidirectional radiation pattern with an average gain of 3 dBi and a sharp reduction in gain at notched frequencies. Moreover, measured group delay and transmission characteristics show excellent transient response.

Design of a dual linearly-polarised microstrip patch antenna, excited by two orthogonal microstrip feed lines, is presented. A reduction in patch size of 35% is obtained when compared to a square patch operating at the same frequency. The polarisations are oriented at +45 and −45° with an isolation of more than 36 dB between the ports. Unlike earlier designs, the proposed structure provides better gain.