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In this paper, a review of the authors' work on inkjet-printed flexible antennas, fabricated on paper substrates, is given. This is presented as a system-level solution for ultra-low-cost mass production of UHF radio-frequency identification (RFID) tags and wireless sensor nodes (WSN), in an approach that could be easily extended to other microwave and wireless applications. First, we discuss the benefits of using paper as a substrate for high-frequency applications, reporting its very good electrical/dielectric performance up to at least 1 GHz. The RF characteristics of the paper-based substrate are studied by using a microstrip-ring resonator, in order to characterize the dielectric properties (dielectric constant and loss tangent). We then give details about the inkjet-printing technology, including the characterization of the conductive ink, which consists of nano-silver particles. We highlight the importance of this technology as a fast and simple fabrication technique, especially on flexible organic (e.g., LCP) or paper-based substrates. A compact inkjet-printed UHF "passive RFID" antenna, using the classic T-match approach and designed to match the IC's complex impedance, is presented as a demonstration prototype for this technology. In addition, we briefly touch upon the state-of-the-art area of fully-integrated wireless sensor modules on paper. We show the first-ever two-dimensional sensor integration with an RFID tag module on paper, as well as the possibility of a three-dimensional multilayer paper-based RF/microwave structure. [ABSTRACT FROM AUTHOR]

A planar WWAN (wireless wide area network) antenna comprising two monopole slots operated at their quarter-wavelength modes for GSM850/900/1800/1900/UMTS operation in the laptop computer is presented. With the use of monopole slot elements, the antenna can be easily printed on an inexpensive FR4 substrate and show a planar structure for promising applications in the thin-profile laptop computer. The antenna can provide two wide operating bands at about 900 and 1900 MHz to cover all the five operating bands for WWAN operation and yet occupies a small area of 10 × 75 mm2 in the narrow spacing between the display and the laptop computer casing. The user's hand effects on the antenna performances when the touch panel or touch screen is used for the laptop computer are also studied. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1274–1279, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24336 [ABSTRACT FROM AUTHOR]

A small-size uniplanar printed antenna suitable for 2.4/5.2/5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX operations is presented. The antenna is a coupled-fed PIFA and shows a height of 9 mm and a width of 13 mm only, when mounted at the top edge of the display panel in the laptop computer. The multiband operation is achieved by using the coupling feed and further embedding a band-notching slit in the radiating arm of the PIFA. With the coupling feed, two wide operating bands can be generated at about 2.5 and 5.5 GHz for the PIFA. By further embedding the slit of length about a quarter-wavelength at about 4 GHz, a band notching characteristic at about 4 GHz is obtained, which leads to an additional resonance at about 3.5 GHz and shows very small effects on the desired 2.5 and 5.5 GHz bands. This behavior results in successful excitation of an additional resonant mode for 3.5 GHz WiMAX operation. Hence, with no increase in the antenna size, three wide operating bands for covering all the desired operating bands of WLAN/WiMAX systems are achieved for the proposed PIFA. Details of the design considerations are presented, and results of the fabricated prototype are discussed. [ABSTRACT FROM AUTHOR]

A coupled-fed planar PIFA (planar inverted-F antenna) operated in its one-eighth wavelength (λ/8) mode, different from the traditional one-quarter wavelength (λ/4) mode, as the fundamental mode for mobile phone application is presented. The proposed PIFA comprises two radiating strips, both of slightly different lengths and close to about λ/8 at 900 MHz. By incorporating the use of the coupling feed, a wide operating band formed by the two λ/8 modes is excited at about 900 MHz for the antenna to cover GSM850/900 operation. Two λ/4 modes are also generated at close frequencies to from a wide operating band centered at about 1950 MHz to cover GSM1800/1900/UMTS operation. The proposed antenna hence can cover GSM850/900/1800/1900/UMTS penta-band operation for application in the mobile phone. In addition, the antenna has a simple structure and can be printed on a thin FR4 substrate of size 1.6 × 7 × 40 mm3 as a surface-mountable chip antenna. Details of the proposed antenna are presented and discussed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1091–1096, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24214 [ABSTRACT FROM AUTHOR]

Performance of a dual-band coplanar patch antenna integrated with an electromagnetic band gap substrate is described. The antenna structure is made from common clothing fabrics and operates at the 2.45 and 5 GHz wireless bands. The design of the coplanar antenna, band gap substrate, and their integration is presented. The band gap array consists of just 3 × 3 elements but reduces radiation into the body by over 10 dB and improves the antenna gain by 3 dB. The performance of the antenna under bending conditions and when placed on the human body are presented. [ABSTRACT FROM AUTHOR]

In this paper, the on-body performance of a range of wearable antennas was investigated by measuring ∣S21∣ path gain between two devices mounted on tissue-equivalent numerical and experimental phantoms, representative of human muscle tissue at 2.45 GHz. In particular, the study focused on the performance of a compact higher mode microstrip patch antenna (HMMPA) with a profile as low as λ/20. The 5- and 10-mm-high HMMPA prototypes had an impedance bandwidth of 6.7% and 8.6%, respectively, sufficient for the operating requirements of the 2.45-GHz industrial, scientific, and medical (ISM) band and both antennas offered 11-dB higher path gain compared to a fundamental-mode microstrip patch antenna. It was also demonstrated that a 7-dB improvement in path gain can be obtained for a fundamental-mode patch through the addition of a shortening wall. Notably, on-body HMMPA performance was comparable to a quarter wave monopole antenna on the same size of ground-plane, mounted normal to the tissue surface, indicating that the low-profile and physically more robust antenna is a promising solution for bodyworn antenna applications. [ABSTRACT FROM AUTHOR]

A very-small-size printed loop antenna for mobile phone application is proposed. The antenna has a loop strip of length 62 mm only, which is folded into an L-shape and occupies a small area of 96.5 mm2 on the top no-ground portion of the system circuit board of the mobile phone. By incorporating a simple matching circuit formed by a chip capacitor and a chip inductor, both in series, the loop antenna can generate three resonant modes (0.25-, 0.5-, and 1.0-wavelength modes) at about 925, 1800, and 2200 MHz. The 0.25-wavelength mode forms the antenna's lower band covering GSM operation, whereas the 0.5- and 1.0-wavelength modes form the antenna's upper band covering DCS/PCS/UMTS operation. Quad-band operation is hence obtained for the printed loop antenna, although it has a very small size. Details of the proposed antenna are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 184–192, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24008 [ABSTRACT FROM AUTHOR]

In this article, a double-printed dipole antenna with band-notched function for UWB applications is proposed and investigated. The band-notched characteristic is achieved by inserting two U-shaped slots on the dipole. Experimental and numerical results show that the proposed antenna meets the requirement of 3.1–10.6 GHz UWB systems with VSWR < 2, while avoiding the interference with the 5 GHz WLAN band. Transmitting antenna transfer function, receiving antenna transfer function, and antenna system function are used to describe the antenna performance. The impulse responses in time domain were calculated using inverse Fourier transform. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2986–2989, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23816 [ABSTRACT FROM AUTHOR]

The paper reports on investigations into phase characteristic of a unit cell of a single-layer microstrip reflectarray, which includes patch or ring elements of variable size. The aim is to have a smaller gradient (slower slope) of the reflected wave phase as a function of the elements' size to achieve a wider operational bandwidth and smaller susceptibility to manufacturing errors. The results obtained for single resonance elements demonstrate that a slower slope can be achieved using thicker substrates at the expense of an inadequate phase range of less than 3000. This inadequate phase range leads to the reflectarray elements phase errors, which reduce its directivity. To overcome this problem the use of multiresonance multiring elements is postulated. It is shown that square and circular shaped multiple rings printed on a thick substrate can offer a slower phase slope and the phase range exceeding 3600. The achieved slopes and ranges of double rings are comparable with those of double stacked patches printed on the equivalent low permittivity dielectric substrate. Choosing suitable dimensions of double-ring elements, the phase characteristic can be made approximately a linear function of their size. [ABSTRACT FROM AUTHOR]

A new design of the printed omnidirectional antenna for applications in 2.4/5-GHz dual-WLAN-band access points is proposed. The antenna consists of a conventional collinear antenna for 2.4 GHz operation and two U stubs for 5 GHz operation. The two U stubs are located near the points where the maximum currents at about 5.5 GHz occurring on the strips of the collinear antenna and arranged back-to-back in the same phase for achieving better antenna gain. Detailed analyses of the U stub on the impedance matching over the 5 GH band is presented. A prototype with good omnidirectional radiation across the 2.4/5-GHz WLAN bands is demonstrated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2403–2407, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23629 [ABSTRACT FROM AUTHOR]

This article proposed a design of a U-shaped strip-slot antenna for GSM900/DCS1800/WLAN/Bluetooth applications. The proposed antenna was fabricated on FR4 substrate and fed by 50-Ω coaxial cable. The proposed antenna was first cut into U-shaped strip to operate at higher frequency of 2.4 GHz for WLAN/BlueTooth applications. Furthermore, the other operation bands-900 MHz and 1800 MHz for GSM900/DCS1800 applications have been achieved by inserted symmetric U-shaped slot into the ground plane. Simulated and measured results are shown below. Details of the proposed antenna configuration and experimental results are also discussed. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2219–2223, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23601 [ABSTRACT FROM AUTHOR]

The multilevel matrix decomposition algorithm (MLMDA) was originally developed by Michielsen and Boag for 2-D TMz scattering problems and later implemented in 3-D by Rius et al. The 3-D MLMDA was particularly efficient and accurate for piece-wise planar objects such as printed antennas. However, for arbitrary 3-D problems it was not as efficient as the multilevel fast multipole algorithm (MLFMA) and the matrix compression error was too large for practical applications. This paper will introduce some improvements in 3-D MLMDA, like new placement of equivalent functions and SVD postcompression. The first is crucial to have a matrix compression error that converges to zero as the compressed matrix size increases. As a result, the new MDA-SVD algorithm is comparable with the MLFMA and the adaptive cross approximation (ACA) in terms of computation time and memory requirements. Remarkably, in high-accuracy computations the MDA-SVD approach obtains a matrix compression error one order of magnitude smaller than ACA or MLFMA in less computation time. Like the ACA, the MDA-SVD algorithm can be implemented on top of an existing MoM code with most commonly used Green's functions, but the MDA-SVD is much more efficient in the analysis of planar or piece-wise planar objects, like printed antennas. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

A printed coplanar two-antenna element suited for WLAN operation in the 2.4- and 5-GHz bands for dual-module applications in a MIMO system is proposed. The two-antenna element is comprised of one planar inverted-F antenna (PIFA) and one monopole antenna, both printed and integrated in a coplanar configuration on a narrow dielectric substrate with the dimensions 50 mm × 11 mm. The two antennas are excited using two separate feeds with a common ground plane. By utilizing two proposed elements spaced 10-mm apart in the lateral direction with an optimized arrangement, the four-antenna MIMO system obtained can achieve optimal isolation between any two of the four antennas. In comparison with the conventional dual-band antenna with a single feed, the proposed two-antenna element allows the 2.4- and 5-GHz signals to be simultaneously received or transmitted with no external switch circuit between the antenna and modules required. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1635–1638, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23540 [ABSTRACT FROM AUTHOR]

This paper reports on the investigations into new configurations of unit cells which offer an increased phasing range for a single-layer printed reflectarray. It is shown that the extended phasing range can be obtained by utilizing similar in shape but different in size resonant elements. Using this principle it is shown that two resonant elements forming a unit cell can double while three elements can almost triple the phasing range of a single resonant element unit cell. These investigations also show that the relative sizes and spacing between the elements in the cell can be adjusted to linearize the phasing curves as a function of the elements dimensions. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1028–1032, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23285 [ABSTRACT FROM AUTHOR]

Spatial communication systems need antennas circularly polarized. In this article, we propose a new compact dual-frequency circularly polarized antenna. The two circular polarizations obtained in each frequency band are on opposite sense. This antenna is a patch of dimensions 36 × 36 mm2, printed on duroid substrate. Left hand circular polarization and right hand circular polarization maximum gains are 6.46 dB at the low frequency and 7.14 dB at the high frequency. Theoretical total efficiency is about 91% in the two bands. Parametric study shows that each frequency band can be controlled separately and that circular polarization can be maintained in each band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 177–180, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23028 [ABSTRACT FROM AUTHOR]

A small printed antenna structure is presented featuring directive radiation patterns over ultrawide frequency band without relying on large antenna dimensions. The antenna comprises virtually two antennas—one electric-type antenna and one magnetic-type antenna—excited simultaneously in close proximity via one feed point. This combination of radiated fields from different types of sources result in directive radiation patterns without increasing antenna sizes as typically observed in antennas using only one type of sources. Two printed prototypes of the combined antenna are fabricated and their measured VSWR and radiation gain pattern characteristics are discussed. [ABSTRACT FROM AUTHOR]

A new internal multiband mobile phone antenna formed by two printed monopole slots of different lengths cut at the edge of the system ground plane of the mobile phone is presented. The antenna can generate two wide bands centered at about 900 and 2100 MHz to cover the GSM850/GSM900/DCS/PCS/UMTS bands and the 2.4-GHz WLAN band. Further, the antenna has a simple planar structure and occupies a small area of 15 x 40 mm2 only. It is also promising to bend the antenna into an L shape to reduce its volume occupied inside the mobile phone. Good radiation characteristics are obtained over the two wide operating bands. [ABSTRACT FROM AUTHOR]

A broadband printed dipole antenna capable of generating a wide operating band for digital television signal reception in the 470-806 MHz band is presented. The antenna is of rectangular shape of width 20 mm and length 227 mm (L), and comprises two asymmetric radiating portions of arm 1 and arm 2 separated by a step-shaped feed gap with its one open end at the center of antenna's one long side edge and the other open end at about L/4 away from the center of the opposite long side edge. The antenna can generate two adjacent resonant modes to form a wide operating band of larger than 50% in 2.5:1 VSWR bandwidth, which is much wider than that of the corresponding conventional center-fed dipole antenna. [ABSTRACT FROM AUTHOR]

An internal printed loop-type antenna comprising a driven monopole and a coupled strip for application in GSM850/GSM900/DCS/PCS/UMTS penta-band operation is presented. The antenna is suitable to be printed on the system circuit board of the mobile phone and short-circuited to the system ground plane to form as a loop-type structure. The antenna provides two wide bands at about 900 and 1900 MHz to cover the GSM850/900 and DCS/PCS/UMTS bands, respectively. The lower band is generated by the driven monopole and coupled strip operated together as a half-wavelength loop resonant structure. The upper band is formed by two resonant modes: the first one is the driven monopole operated alone as a quarter-wavelength monopole and the second one is contributed from the driven monopole and coupled strip operated together as a one-wavelength loop resonant structure. Details of the proposed antenna are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2595–2599, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22791 [ABSTRACT FROM AUTHOR]

A novel printed planar inverted-F antenna (PIFA) with two shielding strips to allow the antenna to be electromagnetic (EM) compatible with nearby conducting elements is presented. That is, the proposed printed PIFA can be placed in very proximity to nearby conducting elements with small or negligible effects on the antenna performances. This attractive feature is mainly because the antenna's possible EM fringing fields are sup- pressed by the two added shielding strips at the feed and end portions of the printed PIFA. Details of the proposed printed PIFA are described, and a design example for wireless local area network operation in the 2.4 GHz band is studied. [ABSTRACT FROM AUTHOR]

Circularly polarized single-layer U-slot microstrip patch antenna has been proposed. The suggested asymmetrical U-slot can generate the two orthogonal modes for circular polarization without chamfering any corner of the probe-fed square patch microstrip antenna. A parametric study has been carried out to investigate the effects caused by different arm lengths of the U-slot. The thickness of the foam substrate is about 8.5% of the wavelength at the operating frequency. The 3 dB axial ratio bandwidth of the antenna is 4%. Both experimental and theoretical results of the antenna have been presented and discussed. [ABSTRACT FROM AUTHOR]

A compact asymmetric coplanar strip, fed monopole antenna for multiband applications is presented. The antenna exhibits three resonances around 1.8, 2.4, and 5.6 GHz covering the DCS/PCS/UMTS/IEEE 802.11b/g/IEEE802.11a/HIPERLAN2 bands. The multiband characteristic of the antenna is due to the various meandered current paths excited in the radiating structure. The antenna has an overall dimension of only 28 × 30 mm2 when printed on a substrate of dielectric constant 4.4. The uniplanar design, simple feeding technique and compactness make it easy for the integration of the antenna into circuit boards. Details of the antenna design, experimental and simulated results are presented and discussed. [ABSTRACT FROM AUTHOR]

A rectangular monopole antenna fed by microstrip, stripline, or coplanar waveguide is studied and enhanced to offer the widest bandwidth with minimum size. A particular attention is focused on ground plans design and coupling between patch and transmission line in order to maintain UWB characteristics and low profile whatever transmission line is used. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1282–1287, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22462 [ABSTRACT FROM AUTHOR]

A novel dual-band printed loop antenna very promising for application in mobile phones as an internal antenna is presented. The antenna comprises an outer loop strip and an inner inverted-L strip connected to and enclosed by the outer loop strip. The antenna occupies a compact area of 15 × 50 mm² only, yet generating three resonant modes to form two wide bands at about 900 and 1800 MHz for the Global System for Mobile Communication/Digital Communication System operation. Detailed design considerations of the three excited modes are described in the paper. When a shielding metal case is placed close to the antenna, small effects on the antenna's impedance matching are seen, allowing compact integration of the antenna with nearby conducting elements or electronic components. The antenna is also found to result in small excited surface current distributions on the system ground plane of the mobile phone. This behavior is expected to lead to reduced user's hand effects on the radiation efficiency of the antenna. [ABSTRACT FROM AUTHOR]

A novel end-fed modified planar dipole antenna for digital television (DTV) signal reception in the 470–806 MHz band is presented. The antenna is of a narrow rectangular shape (10 mm wide and 235 mm long) and is printed on a dielectric substrate. The antenna comprises a step-shaped radiating strip (arm 1) and a narrow rectangular radiating strip (arm 2), both separated by an L-shaped feed gap whose one open end located at the shorter edge or end edge of the antenna. Across this open end of the L-shaped feed gap, the antenna can be excited to provide a wide bandwidth (2.5:1 VSWR) of larger than 50%, which is much wider than that of a corresponding conventional center-fed dipole antenna and allows the proposed antenna easily cover the 470–806 MHz band for DTV signal reception. In addition, over the operating band, the radiation performance of the proposed antenna is similar to that of the conventional center-fed dipole antenna. The proposed end-fed modified planar dipole antenna is studied in detail in this paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 676–680, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22229 [ABSTRACT FROM AUTHOR]

A small printed antenna is described with a reduced ground-plane effect for ultrawideband (UWB) applications. The radiator and ground plane of the antenna are etched onto a piece of printed circuit board (PCB) with an overall size of 25 mm × 25 mm × 1.5 mm. A notch is cut from the radiator while a strip is asymmetrically attached to the radiator. The simulation and measurement show that the miniaturized antenna achieves a broad operating bandwidth of 2.9-11.6 GHz for a 10-dB return loss. In particular, the ground-plane effect on impedance performance is greatly reduced by cutting the notch from the radiator because the electric currents on the ground plane are significantly suppressed at the lower edge operating frequencies. The antenna features three-dimensional omni-directional radiation with high radiation efficiency of 79%-95% across the UWB bandwidth. In addition, a parametric study of the geometric and electric parameters of the proposed antenna will be able to provide antenna engineers with more design information. [ABSTRACT FROM AUTHOR]

A novel compact microstrip fed dual-band coplanar antenna for wireless local area network is presented. The antenna comprises of a rectangular center strip and two lateral strips printed on a dielectric substrate and excited using a 50 Ω microstrip transmission line. The antenna generates two separate resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. Lower resonant mode of the antenna has an impedance bandwidth (2:1 VSWR) of 330 MHz (2190–2520 MHz), which easily covers the required bandwidth of the 2.4 GHz WLAN, and the upper resonant mode has a bandwidth of 1.23 GHz (4849–6070 MHz), covering 5.2/5.8 GHz WLAN bands. The proposed antenna occupy an area of 217 mm² when printed on FR4 substrate (ϵr = 4.7). A rigorous experimental study has been conducted to confirm the characteristics of the antenna. Design equations for the proposed antenna are also developed. [ABSTRACT FROM AUTHOR]

Open-sleeve dipoles are versatile antennas primarily because they have several design parameters that can be varied to achieve a wide range of VSWR performance and operating bandwidth. By properly adjusting their parameters, it is possible to create versions of these antennas that have either a broadband or a dual-band response. In this paper, a new variation of the conventional open-sleeve dipole antenna is introduced, which we call an end-loaded planar open-sleeve dipole (ELPOSD). This configuration provides a degree of miniaturization while retaining a comparable bandwidth in terms of the VSWR response to that of conventional open-sleeve dipoles. Several designs are presented for the conventional and end-loaded configurations that demonstrate the VSWR and miniaturization capabilities of this class of antennas. Measured results have been compared with simulations and found to be in good agreement for an end-loaded planar open-sleeve monopole. [ABSTRACT FROM AUTHOR]

A new printed antenna system mounted in an aperture in the roof of a car is evaluated for broadcast signal reception from 88-108 MHz. Results from simulations on the vehicle are compared with measurements. The overall performance of the antenna is also compared to common types of vehicle antennas, the roof monopole and a glass based antenna. Overall the average gain of the antennas was better than -3 dBi for vertical polarization and -10 dBi for horizontal while the input return loss was generally better than -2 dB before matching sections in the tuners and comparable with common automotive antennas. The antennas in the roof aperture offer an alternative place to mount antennas on automobiles. [ABSTRACT FROM AUTHOR]

A promising design of integrating a wideband printed monopole antenna in a system in package (AiSiP) for wireless local area network (WLAN) operation in the 2.4 GHz band is presented. The antenna is an inverted-F monopole antenna printed on the no-ground portion (6 × 18 mm2) of the module substrate of the AiSiP (total size 24 × 18 mm2). A parasitic shorted strip can also be added in the no-ground portion to double the operating bandwidth of the AiSiP. When mounted on the system ground plane of a wireless device, the AiSiP can provide a complete communication function, without the need of employing additional antennas in the wireless device. The proposed AiSiP is studied in the paper, and obtained results of the constructed prototype are presented. Effects of the system ground plane on the antenna performance of the AiSiP are also analyzed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2113–2117, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21868 [ABSTRACT FROM AUTHOR]

In this paper, the authors present a highly efficient, broadband patch based antenna that is compatible with integrating into Monolithic Microwave Integrated Circuits. The antenna configuration is a proximity coupled stacked patch structure where the layer between the Monolithic Microwave Integrated Circuit and the first patch is an inexpensive laminate. The impact of this layer on the performance of the antenna is investigated both theoretically and experimentally. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:1899–1902, 2006; Published online in Wiley InterScience (www.interscience.wiley.com(. DOI 10.1002/mop.21775 [ABSTRACT FROM AUTHOR]

Two novel Marconi-Franklin type printed antenna arrays, each consisting of three radiating elements arranged in a cascade configuration, are investigated. Both antennas are printed on a single high permittivity dielectric substrate and fed by SMA connectors, although coplanar waveguide (CPW) feed could easily be applied to further allow easier integration into an RF chip module. Two constructed prototypes, suitable for local-multi- point-distribution service operation in the 26-GHz band (25.5-26.5 GHz), are demonstrated. The constructed prototypes show an impedance bandwidth of about 1 GHz and a maximum gain of more than 5 dBi, with small variations (<1.8 dBi), is obtained across the achieved impedance bandwidth. Details of theoretical and experimental results showing impedance and radiation characteristics for both prototype antennas are given and discussed. [ABSTRACT FROM AUTHOR]

A new design using a dielectric reflector to reduce the back radiation of aperture coupled antennas is proposed and developed in this paper. To validate the proposed design, a concise theory analysis is first conducted and then the proposed design is analyzed in a modified aperture coupled microstrip antenna. In this design, a radiating patch and a microstrip feed line are both etched on the same side of a top substrate and a coupled slot is etched on the opposite side of this substrate. To examine the effect of the dielectric reflector on the antenna performance, theoretical simulations and experimental investigations were carried out, and a good agreement between the theoretical expectation and the measured results validates the proposed design. The measured radiation patterns show that the proposed structure can offer a high radiation efficiency, a high front to back radiation ratio, and a high co-cross polarization ratio. With these features, the proposed design is significant in the electromagnetic interference and electromagnetic compatibility (EMI/EMC) designs for reduced undesirable radiation. [ABSTRACT FROM AUTHOR]

A printed collinear two-antenna element suitable for application in a wireless local area network (WLAN) access point in a multi-input multi-output (MIMO) system is presented. The printed element comprises one dipole antenna and one monopole antenna, both printed in a collinear configuration on a narrow FR4 substrate of width 12 mm and length 120 mm and showing good omnidirectional radiation characteristics. It has been found that an antenna system formed by using two proposed elements spaced 75 mm or larger can have good isolation (better than -20 dB) between any two of the four antennas in the two proposed elements. With the comparison to the conventional antenna system formed by four discrete antennas, the antenna system with two proposed elements shows a much smaller lateral length. This characteristic makes the proposed collinear two-antenna element advantageous for application in a MIMO system. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 930–933, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21522 [ABSTRACT FROM AUTHOR]

A compact multiband planar inverted-F antenna (PIFA) suitable for distributed radio-over-fiber repeater networks is modified into a planar structure. It is shown that the planar antenna performance is not degraded with respect to the original PIFA and further, a two layer design is demonstrated to offer improved feed matching. The European bands for GSM, DCS-1800, DECT, UMTS, Bluetooth and HiperLAN2 are all covered. A model of the antenna is introduced as a first stage to developing an equivalent circuit. [ABSTRACT FROM AUTHOR]

We propose an adjoint-variable method for design sensitivity analysis of printed circuits and antennas where allowable perturbations in the design parameters are of a discrete type. We extend previous work on the sensitivity analysis of waveguide structures, where changes in the design parameters are stepwise, on-grid volumetric perturbations. Here, we explore the feasibility of such an approach in the case of printed-circuit board problems (with open boundaries) where perturbations relate to the shapes elements of infinitesimal thickness. We propose a complex-variable formulation of our approximate sensitivity analysis that improves its computational efficiency. The proposed technique offers significant increases in efficiency, accuracy, and convergence when compared to traditional sensitivity-analysis techniques. Its implementation is straightforward. The response and its gradient with respect to all possible design parameters are computed with at most two full-wave analyses—of the original and the adjoint problems. It operates on a fixed discretization grid where perturbations of grid nodes are not needed. We illustrate our technique through the sensitivity analysis of a microstrip line and a probe-fed printed patch antenna as well as the optimization of a printed Yagi antenna array. [ABSTRACT FROM AUTHOR]

This paper presents a study of a novel monopole antenna for ultrawide-band (UWB) applications. Printed on a dielectric substrate and fed by a 50 Ω microstrip line, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. A good agreement is achieved between the simulation and the experiment. In addition, the time domain performance of the proposed antenna is also evaluated in simulations. [ABSTRACT FROM AUTHOR]

This paper discusses the design and analysis of planar circularly symmetric (PCS) electromagnetic band gap (EBG) structures for reducing the surface waves excited by printed antennas on dense dielectric substrates. The key advantage of the circularly symmetric geometries is that a surface wave generated by a source located at its center experiences the same band gap effect in all radial directions. To obtain simple design rules of the PCS-EBGs for the optimization of the bandwidth, an equivalence is established between 2-D-EBGs and PCS-EBGS. Integrated planar printed antennas with bandwidths up to 20% are designed, manufactured and tested. [ABSTRACT FROM AUTHOR]

A printed dipole antenna showing high gain (about 6.8 dBi) radiation in the azimuthal plane is presented. The dipole antenna has a narrow width of 10 mm and a total length of about 202 mm (with 1.64 wavelengths of the frequency at 2442 MHz, the center frequency of the 2.4-GHz WLAN band). In each one of the two radiating arms of the dipole antenna, a meandered line is inserted as a phase-reversal device. With this arrangement, the proposed dipole antenna performs as a collinear array antenna with three in-phase half-wavelength radiating elements, leading to constructive radiation in the azimuthal plane and small side lobes in the elevation plane. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 214–218, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20948 [ABSTRACT FROM AUTHOR]

This paper presents the band-notched operation of a printed short-circuited wideband monopole antenna. The notched or rejected band within a wide operating bandwidth is obtained by embedding an inverted U-shaped slot close to the shorting point of the antenna, where strong excited surface currents in the antenna are usually present. The notched band is controllable by adjusting the lengths of the inner and outer perimeters of the embedded U-shaped slot. A constructed prototype of the antenna is demonstrated, and a parametric study of the embedded slot used for band-notched operation is also presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 58–61, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20900 [ABSTRACT FROM AUTHOR]

A printed collinear antenna with a narrow (10 mm) width showing high-gain omnidirectional radiation is presented. The antenna comprises three half-wavelength elements of one strip dipole, one meandered line, and one straight strip connected in series, and has a total height of only 113.5 mm (about 92% wavelength of the frequency at 2442 MHz) for operation in the 2.4-GHz WLAN band. Due to the meandered line, in which the excited surface current has a phase opposite to that of the strip dipole and straight strip, the destructive radiation in the azimuthal plane for the antenna is suppressed. Conversely, the strip dipole and straight strip are constructive with regard to radiation, which leads to high-gain omnidirectional radiation for the antenna. A prototype showing good omnidirectional radiation (with gain variations less than 1.5 dB in the azimuthal plane) with a high gain level of about 4.4 dBi across the 2.4-GHz WLAN band is presented. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 348–351, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20631 [ABSTRACT FROM AUTHOR]

A novel low-profile broadband printed monopole antenna suitable for VHF operations on vehicles is presented. The proposed monopole antenna is printed on a flexible printed circuit board and then folded onto a cylindrical foam base. A constructed prototype suitable for operation in the 200-MHz band is demonstrated. The prototype has a low profile of about 11 cm only (about 7% of the wavelength at 200 MHz) and shows a wide bandwidth (2.5:1 VSWR) of larger than 20%. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 349–350, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20301 [ABSTRACT FROM AUTHOR]

An omnidirectional planar antenna comprising two back-to-back folded dipoles printed on a dielectric substrate is presented. A constructed prototype suitable for WLAN operation in the 5-GHz band, such as the 5.2-Gift (5150-5350 MHz) and 5.8-GHz (5725-5875 GHz) bands, is demonstrated. The constructed prototype shows a wide impedance bandwidth of larger than 1.1 GHz (about 20% centered at 5.5 Gift), and a stable antenna gain level of about 4.5 dBi, with small variations (< 2 dBi) for omnidirectional radiation, is obtained across the bandwidth. Details of the antenna design and the experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper presents an efficient technique for evaluating Green's functions associated to layered media, when formulated as Sommerfeld integrals in the space domain. The key step in the formulation is that Sommerfeld integrals are computed choosing a suitable integration path which is closed through the imaginary axis of the complex spectral plane. It is shown that with this original choke of the integration contour, the numerical effort usually involved in the evaluation of Sommerfeld integrals can be greatly reduced, specially when large source-observer distances are involved. One asset of this technique is that it can be easily incorporated into integral equation based CAD packages for the efficient analysis of complex printed microwave circuit and antennas. In addition, the theoretical developments needed to set up the numerical algorithm throw a new light on the asymptotic behavior of the layered media Green's functions for large source-observer distances. [ABSTRACT FROM AUTHOR]

Modeled results are presented for an on-glass car antenna designed primarily for reception at VHF. A discussion is given as to the electromagnetic significance of various parts of the car structure with respect to the received pattern shape and computational efficiency. The simulated results are verified by comparison with measurement © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 404–407, 2000. [ABSTRACT FROM AUTHOR]