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This paper presents the concept of offset unifocal phase symmetry to improve the performance (gain, gain roll-off, sidelobe level, etc.) of mechanically beam-steerable transmitarray (TA) antennas. The phase shifts are initially determined from an offset feed source to make the corresponding TA antenna radiate a tilted beam with high gain. The phase shifts are asymmetric and can be broadly divided into dominant and ordinary phase shifts with respect to the offset feed source. By mirroring the dominant phase shifts to make the phase shifts symmetric, it can enable symmetric radiation beams for symmetric offset feed sources and improve phase error. When the offset feed source is moving inward to steer the main beam, the phase error of the phase-shifting surface with respect to the feed source starts to occur, while the electric-field spillover/ illumination from the feed source is improved, which can maintain the gains of scanning beams. To verify the validity of the concept, the performance of a beam-steerable TA antenna enabled by the offset unifocal phase symmetry has been simulated and compared with the counterparts of unifocal and bifocal beam-steerable TA antennas. The measured results agree well with the simulated ones, revealing that the beam-steerable TA antenna enabled by the offset unifocal phase symmetry can maintain realized gains of scanning beams, suppress sidelobe levels, and reduce gain roll-off within the beam-scanning coverage. The offset unifocal phase symmetry, in principle, is a generalized approach and applicable to reflectarray antennas to improve the beam-steerable performance as well.

This brief presents a high-efficiency shared-aperture multiple antenna system. Unlike general shared-aperture antennas, the proposed antenna system with the size of 0.384×0.384×0.171λ3 makes high reuse the aperture in the two respective frequency bands, and the antenna structures of the two bands can each generate positive mutual enhancement for their radiating characteristics in the two bands. The flat Luneburg lens can realize beam steering capability for mm-wave antenna from 25.5 to 29.5 GHz with the gain of 19.3 dBi and improve the wide-angle scanning matching impedance for the Sub-6 GHz antenna from 3.2 to 3.45 GHz with the gain of 6.2 dBi. Meanwhile, as the radiating patch of the Sub-6 GHz antenna, the meta-surface can reduce the focal distance of the lens and maintain the high gain of the mm-wave antenna. Hence, a compact antenna system can achieve beam steering capabilities (up to 112°) in the Sub-6 GHz band and (up to 56°) mm-wave band with high gain, respectively. And the port isolation of the proposed antenna system between two frequency bands is generally better than 25 dB and even up to 40 dB at the Sub-6 GHz band. As reported in the simulated and measured results in a linear array, the antenna system shows good radiating performance with a dual-polarization state. Hence, the proposed multiple antenna system is a good candidate for 5G applications because of the high-efficiency, beam steering with high gain and full 5G band.

In this work, a wideband low sidelobe slot array antenna for wireless communication system at E-band is presented. The slots are excited by a parallel feeding network where the Taylor distribution is applied. Two types of widebandunequal power divider with compact structures are designed for various output ratios to fit the limited feeding network space. One is integrated vertically inside a 2 by 1 elements subarray using a set of pins with asymmetrical offset. The other type is designed inside an E-plane T-junction with unbalance impedance at two output ports. To avoid main lobe tilt and asymmetrical radiation patterns, the feeding network is designed to be biaxially symmetrical, and the feed port is placed in the center of the back. A prototype is fabricated with brass and measured in an anechoic chamber. It achieves a peak gain of 25.8 dBi and a fractional impedance bandwidth of 19.2% with S11 below −10 dB. The measured radiation patterns agree with the simulated patterns very well, and the sidelobe level is lower than −21 dB.

Funding: This work was supported in part by Engineering and Physical Sciences Research Council, U.K., under Grant EP/R013705/1, and in part by IAA Funding. A wide variety of desirable antenna beam patterns can be synthesized by optimal excitation and phasing of the HE11 and HE12 modes in scalar corrugated feedhorns. However, the bandwidth of such two-mode horns is often limited by modal dispersion. In this paper we introduce a class of low dispersion, two-mode feedhorns that can operate, in some cases, over operating bandwidths of 40-50%. We provide example designs that include horns with high coupling efficiency to: 1) a pure HE11 mode for single-mode excitation of corrugated pipe transmission lines; 2) a LG00 and LG02 combination for radiometry, with narrow beams; 3) a pure Laguerre Gaussian LG00 mode for quasi-optical instrumentation with constant phase centers; 4) a constant gain antenna for uniform illumination with frequency; 5) Airy patterns or “top hat” patterns for radar or communications applications, designed to maximize aperture efficiencies when used with larger reflect or lens antennas. More generally, we show methods to generate and phase multiple HE1n modes, to synthesize symmetric output beams at any desired frequency or gain. Publisher PDF

Publisher Copyright: Author Additive manufacturing (AM) is a rapidly developing field, which potentially decreases the manufacturing costs and enables increasingly complex antenna shapes. Metal-based AM might be particularly useful for manufacturing antennas at millimeter-wave (mm-wave) range, because these antennas are physically small enough making AM cost efficient, and manufacturing accuracy could still suffice for good electrical performance. In this letter, two additively manufactured and identical machined fully metallic Ka-band Vivaldi antenna arrays are compared. The manufactured antenna arrays are compared using RF measurements to conclude the feasibility of AM for manufacturing antenna arrays at mm-wave frequencies. Comparison of the measured radiation patterns and realized gains of each of the antenna arrays between 26 and 40 GHz shows close to identical radiation patterns for all the arrays. A loss in realized gain of 0.5-1.5 dB is observed in the AM arrays when compared to the machined array due to the used materials and the surface roughness.

A novel antenna design technique is proposed, which offers bandwidth enhancement up to the limits defined by element radiation efficiency. The employed technique is referred as frequency pulling (FP) as it mimics the ‘insertion loss design methodology of band‐pass filters’. This is essentially a wideband matching approach pushing the antenna efficiency to the limits set up by radiation efficiency. There are three options towards this trend: (i) first to enhance a single element bandwidth (compact element) exploiting its possibly multiple symmetrical feeding points as distinct resonator ports, (ii) frequency pulled array as to design a small antenna array (less than about 10 elements) where each element acts as a resonator and (iii) second order frequency‐pulled array as to build a small array using compact elements of category (i). Similar to the band‐pass filter design, all antennas or distinct‐port circuits resonate at the same resonant frequency when isolated, cascading two or more of them; FP yields to multiple‐overlapping successive resonances in their overall response. Although the proposed technique is general within this first effort, it is applied to simple patch antenna elements exhibiting multiple symmetrical feeding points, namely two—for rectangular, four—for square and five—for pentagonal. The third option is applied to an array of three compact 4‐feeding point square elements offering triple bandwidth with respect to the already wideband single element. However, this is achieved at the expense of a significant beam squint. Thus, in general, these wideband compact elements should be used within a classical array design. Further bandwidth enhancement using FP to antenna elements with inherent multiple resonances as patches with slots or truncated edges constitutes our next task. Their inherent wider bandwidth in radiation efficiency is expected to allow multiply higher bandwidths when exploited with our FP technique.

Accurate knowledge of initial complex excitation coefficients for phased-array elements is essential to ensure accurate array performance. In the literature, many array calibration algorithms have been proposed for this purpose, which generally requires customized phase setting for individual phase shifters connected to array elements. In this article, a new array calibration method is proposed for phased array operating in beam-steering mode only, that is, phase shifts of elements are only simultaneously set according to the beam-steering directions, and therefore, there is no need for dedicated individual element phase tuning. The proposed method requires a minimum number of complex-signal measurements in principle, which enables fast measurement. Furthermore, it is found that the performance of the proposed method is determined by the beam-steering matrix, whose condition number is mainly ruled by the beam-steering angle interval. The proposed method is numerically simulated and experimentally validated in a millimeter-wave (mmWave) phased-array antenna-in-package (AiP) platform at 28 GHz. The proposed method presents good agreement with the well-known rotating element electric field vector (REV) array calibration method, with an amplitude error and phase error within ±0.5 dB and ±5°, respectively. Furthermore, the reconstructed array pattern with the proposed method offers excellent match with the measured array pattern.

Lataa OA, kun julkaistu. This article studies the use of quality factor Q as a tool to design multiport antenna structures with matching networks. Approximative formulas for computing the Q -factor from the port impedances of multiport antennas are presented. We show that the achievable performance level can be reliably estimated based on the Q -factor without the need for computationally heavy and time-consuming matching network optimization. The efficiency of the proposed method is confirmed with a practical two-port antenna cluster design for smartphones operating in the 0.7-1.0 GHz frequency band. The results show that the proposed port impedance-based Q -factor formulas provide an efficient tool to accelerate the design process of multiport antennas.

International audience; In this paper, a flat hyperbolic lens antenna using Groove Gap Waveguide (GGW) technology is designed at 300 GHz. A GGW horn antenna is used to feed the metamaterial lens placed in a parallel plate waveguide (PPW), in order to increase the directivity in the direction of propagation. The combination of both devices, the metalens and the GGW antenna, achieves excellent radiation performance.

Penetration of cellphones into markets requires their robust operation in time-varying radio environments, especially for millimeter-wave communications. Hands and fingers of a human cause significant changes in the physical environments of cellphones, which influence the communication qualities to a large extent. In this paper, electromagnetic models of real hands and cellphone antennas are developed, and their efficacy is verified through measurements for the first time in the literature. Referential cellphone antenna arrays at $28$ and $39$~GHz are designed. Their radiation properties are evaluated through near-field scanning of the two prototypes, first in free space for calibration of the antenna measurement system and for building simplified models of the cellphone arrays. Next, radiation measurements are set up with real hands so that they are compared with electromagnetic simulations of the interaction between hands and simplified models of the arrays. The comparison showed a close agreement in terms of spherical coverage, indicating the efficacy of the hand and antenna array models along with the measurement approach. The repeatability of the measurements is $0.5$~dB difference in terms of cumulative distributions of the spherical coverage at the median level., Comment: 11 pages, 17 figures, Journal

Screen-printed and inkjet-printed conductive fabric antennas have been investigated in this manuscript. The former showed optimal radiation performance after fabrication and measurement, which was the basis for developing a new fabric antenna feeding technique. The aperture-fed technique is achieved with a single coaxial cable overlayed on a cut-out slot on the ground layer of the patch antenna. The cable is connected with conductive silver-based epoxy paste with high resilience to mechanical stress. Two antenna models for Bluetooth low energy (BLE) and long-range (LoRa) wireless applications were designed, fabricated, and measured at 2.44 GHz and 868 MHz, respectively, with good impedance and radiation performance. The measured antennas operated from 2.4 to 2.48 GHz (BLE) and 853 to 886 MHz (LoRa) at −10 dB S11. Measured results also showed a 56% radiation efficiency at BLE and 44.9% at LoRa. The screen-printing procedure and feeding technique have been presented in this manuscript.

The high-precision target echo generation in the field of radar systems is particularly important for large-scale, comprehensive testing of radars. Conventional echo generation techniques often use planar array air feed to simulate echoes. However, it is complicated and expensive to achieve the echo generation with traditional planar array. Therefore, this study proposes a high-precision target generation technique based on one-dimensional linear arrays. The simulation system achieves the target radial high-precision simulation through DRFM technology; the target azimuth high-precision simulation is achieved through differential GPS technology; and the target elevation high-precision simulation is realised through vertical one-dimensional linear array antenna switching. The semi-physical simulation system presented here has the advantages of simple control, low cost, low link loss, easy maintenance, and high simulation target accuracy. Finally, the system was tested in the field to verify the theoretical concept of the article.

A 1 × 4 low-loss frequency scanning planar array with hybrid feeding structure in Ku-band has been designed. In order to improve the array efficiency, the planar array was designed by four parallel sub-arrays and the waveguide slow-wave line structure with electromagnetic coupled slot on narrow side was used as feed line. The results of simulation show that, except at the centre frequency, the voltage standing wave ratio of the antenna array is below 1.2 at the operation band, the range of the scanning angles is (−30.5°, 29°), the beam width of the antenna is about 5.5°–6.6°, the sidelobe is below −20 dB, and the gain is more than 30 dBi.

This study designs a micro-machined BCB-cavity patch antenna and two types of four-element micro-machined antenna arrays at 100 GHz. The patches are fabricated on Benzocyclobutene (BCB) polymer material. The silicon substrate is selective lateral etched under the patch antenna to fabricate a cavity surrounded by metal and filled with BCB material. The BCB-cavity under patches can reduce the excitation of surface waves and enhance the radiation on performance. A single large BCB-cavity is designed to implement the four-element antenna arrays under the consideration of mutual coupling. The proposed single antenna has a 2.8 GHz impedance bandwidth. At 100 GHz, the simulated maximum gain is 6.7 dBi for the single antenna and 13 dBi for the four-element antenna arrays.

Highly integrated multilayered printed circuit board-based patch antenna arrays are proposed in this study for 60 GHz wireless communications. Electromagnetic coupling between two stacked patches is used to achieve the broadband performance. Different structures of single element antennas, two-element antenna arrays and four-element antenna arrays are presented. The two compact four-element antenna arrays show < −10 dB impedance bandwidth of 13 and 14.6% with 12 dBi peak gain. The arrays have the 3 dB gain bandwidth of 9 and 13%. A single column, four-element sub-array is used to design 4 × 16 antenna array. This array delivers 20.8 dBi peak gain with 13% impedance and gain bandwidth. Furthermore, a two-element series fed array is used to realise a 2 × 16 phased antenna array. This array is fed through a 16 × channel radio frequency IC to achieve the beam steering in [inline-formula] range.

A new method for solving the excitation amplitude and phase of wide-band phased array antenna is presented, in which spherical wave expansion and mode filtering (SWEMF) techniques are applied for the first time. Different from the previous methods that are required of matrix inversion or optimization iteration, the proposed SWEMF method is a forward calculation process. Thus, the solution is unique, and the result is closer to the true value. On the other hand, the SWEMF method only needs the total radiated field data of the array antenna in a small angular domain to ensure that the operation is simple and efficient. The effectiveness of the SWEMF method is successfully verified by examples of low sidelobe planar and linear arrays. The mean square error of the excitation amplitude can reach −38.88 dB. The range of excitation amplitude error is 0.05 v, and the excitation phase error is within 5.2°. This method takes about 60 s to calculate amplitude and phase at any one time. The feed amplitude and phase can be only calculated with the data in a small angular domain, and when the amount of data is small.

Conférence virtuelle; International audience; In this paper, a miniaturized omnidirectional circularly polarized (OCP) antenna for Internet-of-Things (IoT) applications is presented. The CP waveform is synthesized by combining two linearly polarized antenna elements which act as electric and magnetic dipole, respectively. The vertical and the horizontally polarized elements are integrated and fed by a single port. The OCP antenna achieves a CP bandwidth covering 80 MHz from 2.4 to 2.48 GHz. The results show that the antenna can provide at 2.44 GHz an axial ratio lower than 3 dB and gain variations of less than 1.1 dB over all azimuth angles. The OCP antenna is printed on two cost-effective FR-4 PCBs and it is very low profile. Thanks to its radiation and geometric properties, the proposed antenna solution fits well in specific IoT use cases where a monopole-type radiation pattern is required.

Three different feed horn antennas for radio astronomy applications are presented in this paper. Feed structures including Choked ring horn, conical corrugated horn, and exponentially shaped quad-ridged horn are designed and simulated. Circular waveguide with same diameter is used for exciting the dominant TE 11 mode in the input of all proposed antennas. The performance of each feed horn regarding the beamwidth, gain, cross polarization and side lobe levels are investigated in Q-band frequency range., 2020 IEEE USNC-CNC-URSI North American Radio Science Meeting (Joint with AP-S Symposium), July 5-10, 2020, Montreal, QC, Canada

Antenna arrays are commonly used to achieve high gains and beam steering, but they require complex feeding networks. For applications demanding moderate antenna gains (≃6 dB) and planar radiating structures, printed Yagi-Uda antennas can offer many advantages, but clearly, they cannot cover the whole azimuth plane. A symmetric structure made of two Yagi-Uda antennas with two active elements, a shared reflector and two directors of variable length is here presented and demonstrated to have switched beams that cover all the azimuth plane. By lengthening the physical lengths of the directors, they turn to act as reflectors: as a result, this antenna system has the ability to switch between broadside, bidirectional end-fire and two opposite end-fire patterns. The feeding is provided by a balanced parallel strip-slot line without the need for a balun section and thus reducing the overall size of the antenna. A modified design is also presented, obtained by adding a reflector board which allows for higher gains and focused radiation reconfigurability in the half-space. Simulated and measured results of both designs are reported showing good agreement. The antenna has a compact size, wideband characteristics and directive pattern reconfigurability.

Autonomous driving is becoming a reality-but low-cost 79 GHz radar antenna technology is still imperfect. Here, the authors propose a kind of proximity-coupled feed patch antenna array. By reducing the non-linear mutual interference between the transmission line and the radiating elements, the antenna's operating bandwidth is improved and the antenna gain is increased. Moreover, the consistency of the antenna radiation pattern at different frequencies is also improved. The simulation results show that the antenna has a −10 dB impedance bandwidth from 76 to 81.4 GHz, and the gain is >14.8 dB. Within the operating frequency band, the antenna main lobe width is smaller than ±1.2°

The upcoming standards of wireless communications result in additional and more stringent requirements for antennas in mobile phones. In this paper, we present a frequency-reconfigurable antenna that could potentially be suited for future mobile devices. Frequency reconfigurability is achieved through a cluster of mutually coupled antenna elements that is excited with frequency-dependent weights using a multichannel transceiver. We report a mobile handset antenna cluster measuring 15 $\times $ 15 $\times $ 1.6 mm3 that covers the frequency bands of 1.7–2.7, 3.3–4.5, and 5.475–6.425 GHz with an antenna efficiency better than 90%. The operation of the antenna cluster is experimentally verified by feeding all the antenna elements with proper weights using tailor-made power splitters that represent a multichannel transceiver with adjustable amplitude and phase in each branch. The results obtained with the feed networks suggest the feasibility of the reconfigurability concept and pave way for codesign of the antenna and the transceiver.

International audience; In this paper, two different feeding techniques for patch antenna placed on a multi-layer PCB build-up are studied. Antenna design target 5G n258 band. Despite the losses in the inner layers, the patch feeding based on aperture coupling has a radiation efficiency higher than 70%. A second design using via direct feeding show similar performance, given the same antenna's height. An 4 × 4 array has been simulated and fabricated. The experimental results agree well with simulated ones, providing a 13 dB realized gain and a scanning angle of 90° large.

In this study, simple and compact novel-shape planar monopole antenna for multi-band operation such as DCS, Bluetooth, and ultra-wide-band (UWB) is proposed. Proposed antenna comprises of circular ring with extended rectangular monopole antenna in one of the arm of the circular ring and inverted L-shape monopole antenna at the centre of the structure is placed to generate multiple resonances at different frequencies. In this structure, Bluetooth frequency band generates due to extended rectangular patch, DCS band by inverted L-patch, and UWB bands due to circular ring. Easily available FR4 substrate with permittivity 4.4 and loss tangent 0.02 is used for fabrication with antenna dimensions (35.5 × 24.5 × 1.6) mm^3. Antenna structure is fed through 50 Ω micro-strip line and terminated by SMA connector. Measured return loss of the antenna is ≤−10 dB with effective control over the three operating frequency bands. In addition, some selected key parameters which affect the impedance bandwidth are analysed and results are discussed.

Empirical results of an electrically small printed monopole antenna are described with a fractional bandwidth of 185% (115 MHz to 2.90 GHz) for return-loss better than 10 dB, peak gain and radiation efficiency at 1.45 GHz of 2.35 dBi and 78.8%, respectively. The antenna geometry can be approximated to a back-to-back triangular shaped patch structure that is excited through a common feed-line with a meander-line T-shape divider. The truncated ground-plane includes a central stub located underneath the feed-line. The impedance bandwidth of the antenna is enhanced with the inclusion of meander-line slots in the patch and four double split-ring resonators on the underside of the radiating patches. The antenna radiates approximately omni-directionally to provide coverage over a large part of very high frequency, the whole of ultrahigh frequency, the whole of L-band and some parts of S-band. The antenna has dimensions of 48.32 × 43.72 × 0.8 mm 3 , which is corresponding to the electrical size of 0.235 λ 0 × 0.211 λ 0 × 0.003 λ 0 , where λ 0 is the free-space wavelength at 1.45 GHz. The proposed low-profile low-cost antenna is suitable for application in wideband wireless communications systems. This work is partially supported by innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1.

International audience; In this paper, a technique to maximize the directivity of an antenna array is presented. It consists of a fed monopole and a loaded parasitic one. The nature and value of the load are obtained using the Uzkov equations that calculate the current weighting coefficients in the case of two separately fed antennas to maximize the gain and the directivity in one direction. Reconfigurability is achieved by using reflectors and directors activated by pin diodes to reduce the back radiation and pointing in the desired direction. Thus a system of two elements, one fed and the other loaded with an inductor, having a maximum gain of 5.2 dBi at 2.45GHz in azimuthal directions 90° and 270° is obtained. The system is compared with a system of two antennas fed separately.

A new textile wearable wireless node, for operation in the 2.45 GHz industrial, scientific and medical (ISM) band, is proposed. It consists of a dual-polarised textile patch antenna with integrated microcontroller, sensor, memory and transceiver with receive diversity. Integrated into a garment, the flexible unit may serve for fall detection, as well as for patient or rescue-worker monitoring. Fragile and lossy interconnections are eliminated. They are replaced by very short radiofrequency signal paths in the antenna feed plane, reducing electromagnetic compatibility and signal integrity problems. The compact and flexible module combines sensing and wireless channel monitoring functionality with reliable and energy-efficient off-body wireless communication capability, by fully exploiting dual polarisation diversity. By integrating a battery, a fully autonomous and flexible system is obtained. This novel textile wireless node was validated, both in flat and bent state, in the anechoic chamber, assessing the characteristics of the integrated system in free-space conditions. Moreover, its performance was verified in various real-world conditions, integrated into a firefighter garment, and used as an autonomous body-centric measurement device.

A novel coplanar waveguide-fed ultra-wideband antenna with triple band-notched function centred at 3.5, 5.5 and 7.5 GHz is proposed. It has small size of 26 × 26 mm^2. This antenna consists of an elliptical radiator and a square ground plane with an elliptical slot on one side of the substrate. Besides, two circles with a radius of 2 mm were dug from the edge of the outer ellipse to realise the bandwidth requirement. To avoid interference from Worldwide Interoperability for Microwave Access, a single open-ended elliptical arc-shaped slot was etched on the top side of the ground. Moreover, another elliptical arc-shaped slot notched at wireless local area network band was etched on the elliptical radiator and two systemically C-shaped slots working at 7.3–7.7 GHz was embedded on the structure. Measured voltage standing wave ratio shows the working frequency range was from 3.1 to 13.5 GHz except for notched bands of 3.35–3.8, 5.1–5.9 and 7.35–7.8 GHz.

This communication proposes a new patch antenna with dual circularly polarized capability at 2.575 GHz. The design exploits the even and odd modes in a coplanar waveguide transmission line and enables simultaneous right- and left-handed circular polarization, with two individual excitation ports. A patch antenna is fed by multimode transmission line and the advantages and disadvantages are discussed. A prototyped antenna realized up to 20 dB isolation between ports with S21

Multibeam satellite communication (SatCom) with full or aggressive frequency re-use is one of the most promising candidates for next-generation high throughput satellite systems. However, frequency re-use creates interbeam interference which needs to be managed using multiuser precoding techniques in the forward link and multiuser detection techniques in the reverse link. This work considers the forward link of multibeam Sat-Com systems and proposes a novel zero-forcing (ZF) precoding technique that makes use of users' physical location and antenna radiation pattern available at the gateway. Contrary to conventional precoding techniques in multibeam SatCom systems, the proposed precoding technique does not require feedback from user terminals. Numerical results show that the proposed ZF precoder achieves higher ergodic capacity than the conventional ZF precoder. We provide a closed-form approximation for the ergodic capacity of the proposed ZF precoder under rain fading. We also provide a closed-form approximation for computing the moments of the rain fading attenuation which enables us to derive high and low signal-to-noise ratio (SNR) expressions of the ergodic capacity in closed-form. Furthermore, an upper bound on the ergodic capacity is obtained. Monte Carlo simulations are used to validate the accuracy of our analysis. Refereed/Peer-reviewed

International audience; We describe the design, fabrication and measurements of an axisymmetric dielectric lens, featuring a sectorial radiation pattern at 77 GHz. It will be used as the primary feed of a lens-based compact antenna test range (CATR). Due to symmetry of revolution, the sectorial lens profile can be designed in one dimension by using phase only control. The phase variation is echoed on the lens depth. The resulting stepped lens is simulated using France Telecom Orange Labs SRSRD software (¿in-house¿ software developed for dielectric axisymmetric radiating structures) and measured in an anechoic chamber at 77 GHz. Two lenses were fabricated with different materials: PVC and polyurethane, respectively. Good agreements were obtained between simulations and measurements. Less than 0.2 dB ripple in the central beam are obtained for the polyurethane lens although relatively high secondary lobes occur at 11°. Comparisons between the near field of a CATR illuminated by a small horn providing a uniform amplitude taper and the sectorial lens are conducted using numerical simulations. Results show that on-axis oscillations are reduced from 6 to 1 dB with the sectorial lens.

The use of ultrawideband technology in many applications implies the use of a suitable radiating structure, especially for pulsed systems. The development of a triangular CPW-fed printed antenna with specific ground plane shape is presented. First the triangular element was optimized to minimize return losses and size of the antenna in the [3.1-10.6] frequency band. The evolution of radiation patterns with frequency was also studied, as changes in phase center position and radiation characteristics alter the integrity of transmitted pulses. Thus the antenna ground plane shape was modified in order to maintain almost constant radiation patterns over the entire bandwidth. Time domain measurement methods were used to characterize the antennas and validate these improvements. The procedure is presented and results are plotted in a 3D format and discussed.

International audience; Several solutions are presented to reduce the mutual coupling between two planar inverted-F antennas (PIFAs) working in close radiocommunication standards and positioned on a finite-sized ground plane modeling the printed circuit board (PCB) of a typical mobile phone. First, the two PIFAs are designed on separate PCBs to, respectively, operate in the DCS1800 and UMTS bands. In a second step, they are associated on the top edge of the same PCB. Realistic arrangements are then theoretically and experimentally studied. Finally, several solutions are investigated to maximize the isolation. They consist in inserting a suspended line between the PIFAs' feedings and/or shorting points. All along this paper, several prototypes are fabricated and their performances measured to validate the obtained IE3D moment method-based simulation results

A simple method of acquiring super wideband characteristics for monopolar patch antenna is proposed. Through adopting a modified cone as feeding and radiating structure, the monopolar patch antenna can reach the impedance bandwidth of more than 1:23.4 for voltage standing wave ratio (VSWR) ≤ 2. In the whole operating band, the antenna has the like-monopole omnidirectional radiation patterns and the peak gains of 3.8–8.7 dB. Meanwhile, the height of the antenna is just 0.074λ(c), and the diameter of the radiated body is 0.205λ(c), which is smaller than other ultra-wideband omnidirectional antenna.

Author(s): Capolino, F; Bussotti, P; Borselli, L; Albani, M; Maci, S | Abstract: The problem of edge diffraction close to a point caustic is analyzed in a typical dual-reflector Gregorian antenna in offset configuration. The diffraction phenomenon is produced by a perfectly conducting fin located between the feeder and the main reflector. This fin is sometimes used to reduce the coupling between the primary feed and the main reflector. For the sake of simplicity, the two-dimensional case is studied here, but the present technique can also be applied to practical three-dimensional configurations. © 1997 John Wiley a Sons, Inc.

This paper presents the design and implementation of a dual polarization antenna with a low loss, planar feeding structure applicable for both, communication and radar applications at mm-wave frequencies. The array and feed network efficiency is approximately 50 %. Radiation patterns are given and discussed in detail. A higher gain can be achieved by duplicating the feed structure and the antenna subarrays.

Experiments are described using a photonic beam former to control a 60-GHz smart antenna. The 60-GHz signals are generated by optical heterodyning the waves of two laser diodes. Beam forming is achieved by new photonic planar lightwave circuits in silica technology. The beam former enables individual weighting of the millimeter-wave signals feeding the antenna elements. The required weights for a desired field distribution are calculated using the maximum directivity beam-forming algorithm.

A 2-element elliptical patch antenna array with a bidirectional radiation pattern has been developed for ultra wideband indoor wireless communications. The array is constructed by means of feeding two omni-directional elliptical patch elements with a 3-section hybrid power divider. Experimental results show that the array has a stable radiation pattern and low return loss over a broad bandwidth of 64% (3.1–6 GHz). © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 886–890, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23232

The performances of focal plane arrays that implement multibeam coverage from a single reflector antenna are usually reduced by conflicting requirements on the feed elements. Dense packing is required to minimize the beam separation, while typically large apertures provide the high feed directivity which in turn translates in low spill over losses from the reflector. In this contribution, the use of a dielectric super-layer to shape the radiation pattern of each feed, so that the spill over from the reflector is reduced without increasing the dimensions of each aperture, is discussed.

International audience; In this paper we propose a novel low cost and original circularly polarized monolayer radiating structure with opposite senses of polarization, covering the 1.576 GHz global positioning system (GPS) and the 2.338 GHz satellite digital audio radio system (SDARS) bands. This antenna is made up of a central square patch and a square ring around, both with truncated corners, placed of the center of a square ground plane of small dimensions. The two parts are linked together by mean of four connecting small microstrip lines. It is printed on duroid substrate. A single coaxial probe feed is connected at few millimeters from the center of the antenna to create the circular polarization (CP) in the two frequency bands.

We present a cavity-backed patch antenna with enhanced bandwidth and good efficiency which is assembled in a multilayer fully planar structure. The single element represents a basic block that can be replicated in a modular configuration to design array antennas implementing beam scanning or more general "smart" functionalities. To do that, each element has to be provided by a phase shifter that can be directly integrated on the layer hosting the beamforming network. For this reason, particular care was taken to minimize the space occupied on this layer by the feeding and matching network, so that most of the space of the unit cell is left free. The antenna was designed using a commercial, method of moments (MoM) based software. Results are shown for a single element and for a 2x2 array; a prototype is under construction.

International audience; A differential feeding technique for a broadband planar antenna-array is presented. The antenna structure is composed of four parallel linear series-fed arrays of four microstrip patches. To cancel the beam tilt versus frequency, one side of the array is fed with in-phase signal, whereas the same out-of-phase signal feeds the opposite side of the array. A rat-race balun is especially designed to generate those two signals. In comparison with other feeding techniques, there is no need for a resistive load which is actually a problem at millimeter (mm)-wave frequencies. To validate the concept, a 60 GHz prototype etched on the TacLamPlus substrate is designed and measured.

In this contribution we present a theoretical model for the analysis of finite arrays of open-ended waveguides on finite supporting structures and/or radome coverages. This model is based on a multi-mode equivalent network (MEN) [G.Gerini, M. Guglielmi, G. Lastoria, Efficient Integral Equation Formulation for Admittance or Impedance Representation of Planar Waveguide Junctions] representation of the radiating waveguides with their tuning elements and a high frequency approach of the external region. The accessible ports given by the multi-mode network connecting the antenna with the feeding waveguides offers the possibility of optimizing the structure looking both at the radiation characteristics of the antenna as well as at the matching network in the waveguides.

International audience; A dual-band HF and UHF RFID tag antenna with two feeding points is presented, fabricated and measured. A convenient HF resonance is obtained with an HF ASIC chip as well as good impedance matching with UHF ASIC chip in the European RFID UHF band. Tuning techniques of the design parameters are proposed, and tag performance in both frequency bands is evaluated.

International audience; pin diode control is used to obtain a dual-band operation of a capacitively coupled patch antenna fed by a coplanar waveguide (CPW). The beam-lead pin diodes are inserted in the excitation slot and reduce the coupling length of the slot in their ON state. The frequency ratio of the two operating frequencies is 1.22 at 4.0 GHz. Details of the antenna design and experimental results are presented and discussed.

International audience; A circularly polarised patch antenna, fed by a coplanar waveguide, is investigated experimentally. The antenna is excited by a couple of 100 Ω slotlines which are combined to obtain a 50 Ω coplanar waveguide. The axial ratio and the bandwidth of the antenna are similar to those obtained with other types of feeding.

Apprenticeship is linked to training. This paper is intended to be a tutorial on how to design, fabricate, and measure antennas in an economical and easy way, using recycled materials and common electronic devices such as a laptop and an access point. Several antenna designs built with household materials are proposed, giving practical design and fabrication guidelines. The use of the Wi-Fi band allows linking the experiment with daily-life devices, and proposing a simple and economical antenna-measurement system. The capacity to experiment with antennas from their design to measurement will defi nitely stimulate undergraduate or graduate students to get acquainted with the basic topics of antennas and propagation. The paper presented herein was awarded with the fi rst price in the IEEE AP-S Student Challenge 2010 [1, 2].

This paper presents a robust and easy manufacturable dual linear-polarized dielectric waveguide antenna (DRA) for the 24 GHz industrial, scientific, and medical band. Dual-polarized operation is achieved by utilizing a square metal waveguide and a conical horn for exciting the surface wave on a tapered dielectric rod. In order to couple a signal into the square waveguide, an innovative dual-polarized, aperture-coupled microstrip-to-waveguide transition is shown. Additionally, two kinds of radomes, i.e., a foam radome and a half-wave wall monolithic radome are presented to protect the DRA. The antenna achieves a 10 dB bandwidth of 1.7 GHz and a gain of 11.5 dB including losses caused by the transitions and connectors. The sidelobe level and the cross-polarization level are lower than -25 and -26 dB, respectively. Designs and measurement results of all components are described in detail in this paper.