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DECIGO is a future Japanese project for the detection of gravitational waves in space. To conduct various scientific missions, including the verification of cosmic inflation through the detection of primordial gravitational waves as the main objective, DECIGO is designed to have high sensitivity in the frequency band from 0.1 to 10 Hz, with arms of length 1000 km. Furthermore, the use of the Fabry-Perotcavity in these arms has been established for the DECIGO project. In this paper, we scrutinize the significance of the Fabry-Perot cavity for promoting this project, with a focus on the possibility of observing gravitational waves from cosmic inflation and binary compact star systems as indicators. The results show that using the Fabry-Perot cavity is extremely beneficial for detecting them, and it is anticipated to enable the opening of a new window in gravitational wave astronomy. [ABSTRACT FROM AUTHOR]

A novel Fabry-Perot cavity (FPC) antenna with metasurface is presented, which can achieve broad bandwidth and low profile. Traditional FPC antennas, with rectangular microstrip antennas as feeds, have limited impedance bandwidth and struggle to make a compromise in the gain bandwidth and maximum gain value. To obtain wide bandwidth, the FPC antenna proposed in this paper utilizes a feed antenna loaded with parasitic patches. To widen impedance bandwidth and gain bandwidth and reduce the profile, a positive phase gradient partially reflective surface (PRS) and an artificial magnetic conductor (AMC) are located above and below the feed antenna, respectively. The phase property of the PRS and AMC also brings in a more smooth gain value curve. To further increase gain values, four metal reflector plates are located around the proposed antenna. The overall dimension of the antenna is 2.5λ0×2.5λ0×0.25λ0 (λ0 is the free space wavelength at 7.5 GHz). Simulated results show that the resonant cavity antenna proposed in this letter exhibits an impedance bandwidth of 13.3% (7-8 GHz) and a 3 dB gain bandwidth of 14.3% (7.02-8.10 GHz). The maximum gain in the whole operating band is 14.5 dBi. The measured results are in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

A dual-polarized filtering Fabry-Perot antenna (FPA) with high selectivity and high isolation is proposed for in-band full-duplex (IBFD) applications. The proposed antenna utilizes a square patch as the feeding element, which is fed by a double differential-fed scheme for dual-polarized radiation with high isolation. The patch is loaded with a symmetrical cross-slot and four shorting pins for a broad passband filtering feature. To enhance broadside gain across a wide frequency range, the patch is incorporated with a partially reflecting surface (PRS), which is composed of two complementary cross-slot and patch arrays. Moreover, the frequency selectivity of PRS is exploited to improve the filtering characteristic. The double differential feeds are realized based on out-of-phase power dividers, which are combined with simple low-pass filters to further improve the out-of-band suppression. The final design was fabricated and measured. The measurement results show excellent results with a 10-dB return loss bandwidth of 21.5% (4.91-6.09 GHz), isolation of greater than 40 dB, peak gain of 13.7 dBi, out-of-band suppression level of better than 27 dB, and a cross-polarization level of less than -27 dB. [ABSTRACT FROM AUTHOR]

Studying the geometry of electromagnetic band gap (EBG) structures in 1 and 3 dimensions is useful for achieving effective directional radiation, high gain, and side-lobe attenuation of antennae. This paper presents an EBG antenna, whose radiating source is a rectangular notched patch, which can be used for applications around 20 GHz. Two conventional woodpile dielectric structures with a triangular lattice are presented in a comparative study to extract the best physical and electromagnetic performance in terms of directivity, bandwidth, and gain; these are the square and the cylindrical rods. These two structures' electromagnetic and geometrical limits allow the design of a 3D EBG structure called an icosahedral structure. The proposed antenna is composed of different ceramic substrates (the Arlon AR 450, (h = 0.48 mm, ɛr = 4.5, El Tand = 0.0035) on which the radiating element is placed, the Rogers TMM 13i, (ɛr = 12.85, El Tand = 0.0019) for the 3D icosahedral structure; and the Taconic TLY-5A, (ɛr = 2.17, El Tand = 0.0009) for the 1D lateral walls). With a substrate-plated radiation source coupled with a 3D icosahedral structure and surrounded by a vertically mounted 1D structure, a directivity of 19 dBi was obtained with a realized gain of 17.7 dB and an optimal coupling (antenna–EBG material) at 19.8 GHz. These results are encouraging given the antenna size of 33.41 × 27.87 × 37.36 mm3. [ABSTRACT FROM AUTHOR]

We propose a novel design method for an ultrasmall high-efficiency Fabry-Perot cavity (FPC) antenna using an artificial magnetic conductor (AMC). Unlike conventional FPC antennas, which are approximately 2 λ, 3 λ in size, the proposed antenna has an ultrasmall size of 0.37 λ⨉0.37 λ, and it is enclosed by metallic walls blocking leaky waves. By installing an AMC on the metal walls, we significantly improve the radiation efficiency by up to 91 %. When the proposed antenna is utilized as an element of array antennas, it is expected to demonstrate a wide beam-steering range without grating lobes, owing to the narrow interval of the elements and the high steering accuracy resulting from the inhibition of undesirable couplings between the elements by the side walls. [ABSTRACT FROM AUTHOR]

In recent years, metasurfaces have become a rapidly growing domain of research in several fields of engineering and applied physics due to their ability to manipulate both phase and amplitude of electromagnetic fields. These artificial 2D-materials, usually composed of metallic elements printed on dielectric substrates, have the advantages of being low profile, lightweight as well as easy to fabricate and integrate with standard circuit technologies. In this context, this paper reviews the latest progress in metasurface antenna design, where metasurfaces are used to miniaturize the profile, increase the bandwidth, and control the radiation pattern in the near- and far-field regions. [ABSTRACT FROM AUTHOR]

In this article, a narrow and a wide band high gain antenna with improved front to back ratio using highly reflecting surface are proposed. A highly reflecting compact ultrathin metasurface (MS) of thickness 0.0134 λ with >90% reflection band of 1.42 GHz from 4.55 to 5.97 GHz is designed. The open air field Fabry–Perot cavity resonator antenna is designed by placing this MS over a microstrip patch antenna radiator first and next on standard wide band C‐band wave guide port radiator at an optimum height to get narrow and wide enhanced gain band width, respectively. The proposed antennas are fabricated and measured experimentally. A low profile narrow band FPC antenna with measured broad side gain enhancement of 8.54 dB having maximum measured gain of 16.5 dBi at 5.3 GHz is designed first. Next, a wide band FPC antenna having broad side measured enhanced gain band width of >1 GHz from 4.75 GHz to about 6.00 GHz with maximum gain enhancement of 8.32 dB with maximum measured gain of 17.85 dBi at 5.30 GHz is observed. A wide improved front to back ratio (FBR) band of 1 GHz with maximum FBR of 39.5 dB at 5.30 GHz is presented. This antenna can be used for 5G long range services. [ABSTRACT FROM AUTHOR]

Abstract: A novel reflective metasurface which presents different reflection phases to different polarization waves is designed in this article. The metasurface is used as the ground plane of a Fabry‐Pérot cavity (FPC) antenna. The radiator of the FPC antenna is a dual‐band patch antenna which has different polarizations in different bands, so by tuning the reflection phase of the metasurface correctly, the FPC antenna can work in two frequency bands. A prototype antenna is fabricated and measured. The measured results show that the antenna can operate at 8.35‐8.56 GHz (2.5%) in x‐polarization and 9.5‐10.1 GHz (6.1%) in y‐polarization. The maximum realized gains of the antenna in two bands are 17.6 dB at 8.75 GHz and 19 dB at 9.8 GHz. The measured results agree well with the simulated results which confirm the correctness of the design. [ABSTRACT FROM AUTHOR]

This paper presents a method to achieve high gain (>20 dBi) and wide bandwidth (>55%) from a compact antenna that is less than one wavelength tall and only 2.6\lambda 0 in diameter at the lowest operating frequency. The antenna comprises of an optimized single-layer superstrate, made out of four dielectric sections, and a ground plane, which are separated by an air cavity. The permittivity and thickness of the dielectric sections decrease in the transverse direction. Two-step optimization method was implemented employing a customized full-wave optimizer to optimize the width and thickness of each dielectric section in the superstrate, while maintaining a fixed overall diameter of the antenna. This optimization results in an antenna with a high gain and a large 3-dB gain bandwidth, without compromising on antenna footprint. A prototype of the new antenna having a superstrate with stepped thickness was fabricated and tested. It exhibits a measured peak broadside directivity and a peak realized gain of 20.7 and 20.2 dBi, respectively. Its measured gain-bandwidth product of 5969 and directivity-bandwidth product (DBP) of 6580 are almost three times the best figures for resonant cavity antennas (RCAs). The total area of the new antenna prototype is 5.3\lambda 0^{2} and its overall height is 0.89\lambda 0 at the lowest operating frequency. It is significantly more compact and its DBP per unit area and aperture efficiency are significantly greater than those of lens-based antennas. Its measured 3-dB gain bandwidth of 57% is unprecedented for high-gain short antennas, including RCAs. Moreover, over the entire bandwidth, sidelobe levels of the antenna are around −12 and −21 dB in the E- and H-planes, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a design of a planar, lowprofile, and high gain Fabry-Perot cavity antenna for Kband applications is presented. The antenna is consisted of a frequency selective surface (FSS) made of a circular hole array and a feeding structure made of a coupled strip-slitline. The FSS and the slitline both are lithographically patterned on a high permittivity substrate while the stripline is printed on top of a thin and low permittivity substrate. These two substrates are then closely appressed each other to form a planar structure. The measured results show that the proposed antenna has an impedance bandwidth of about 4% (|S11|≤-10 dB), a maximum gain of about 10.4 dBi, and a 3-dB gain bandwidth of approximately 2.9% at the resonance frequency of around 20.8 GHz. The antenna's compact, planar, and lightweight profile, i.e., approximately 4λo × 4λo × 0.24λo of a free-space wavelength at 21.0 GHz makes it promising for a small and efficient source in K-band applications. [ABSTRACT FROM AUTHOR]

A low profile dual band resonant cavity antenna that incorporates double sided partially reflective surface (PRS) with complementary layers is presented here. The PRS is formed by printing periodic array of complementary metallic square loops on the opposite sides of the dielectric material. The PRS has been used as a superstrate, placed above the radiating microstrip patch. This PRS acts as a dual band matching section between the microstrip patch and free space, hence resulting in dual resonance. The proposed structure has been analyzed using equivalent circuit model. Parametric analysis of the sensitive structural parameters has also been discussed. To validate the design, the simulation analysis and experimental results obtained from a prototype operating at 8.9 and 9.4 GHz are presented. The measured gain at the two frequencies is 10.2 and 8.5 dBi, respectively. The overall size of the antenna is 1.78λ × 1.78λ × 0.09 λ with λ corresponding to 8.9 GHz. [ABSTRACT FROM AUTHOR]

ABSTRACT A high gain dual-polarized wideband Fabry-Perot (FP) antenna fed by 1 × 2 antenna array is proposed. A metasurface consisting of patch and mesh array is employed as a partially reflective surface, which produces a reflection phase with a positive slope over a wideband frequency range for increasing antenna's gain bandwidth. To obtain dual polarizations and further improve the gain of antenna, a 1 × 2 patch array coupled by two orthogonal slots is designed as the feed of the FP antenna. A prototype is fabricated and measured. The measured results demonstrate that this proposed antenna has a 3-dB gain bandwidth of 22.2% in both polarizations. The peak gain of 15.7 dBi and 15.2 dBi is obtained at two polarization ports, respectively. Within the 3-dB gain bandwidth, good impedance matching with high isolation over 35 dB between the two ports is achieved as well. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2316-2321, 2016 [ABSTRACT FROM AUTHOR]

In this communication we present a concept of a partially reflective surface (PRS) antenna capable of independent beam-scanning and beamwidth dynamic control. The beamwidth is controlled by reconfiguring the PRS reflectivity via embedded varactor diodes, while the beam is steered by using a small phased array in the H-plane as a source antenna exciting the Fabry-Pérot cavity. A fully operational prototype is fabricated and measured upon reconfiguration, demonstrating the viability of the concept and good agreement between simulated and measured results. The achieved beamwidth variation is from 18.7^\circ to 22.4^\circ, with the scanning range of 15^\circ and 20^\circ for the narrowest and the widest beamwidth, respectively. [ABSTRACT FROM AUTHOR]

This review paper summarizes various aspects of directive beaming and explains these aspects in terms of leaky waves. Directive beaming occurs in antenna design where a narrow beam is obtainable by using fairly simple planar structures excited by a single source. These structures include Fabry–Pérot cavity structures as well as metamaterial structures made from artificial low-permittivity media. Directive beaming also occurs in the optical area where it has been observed that highly directive beams can be produced from small apertures in a metal film when an appropriate periodic patterning is placed on the film. One aspect that these phenomena all have in common is that they are due to the excitation of one or more weakly attenuated leaky waves, the radiation from which forms the directive beam. This is established in each case by examining the role of the leaky waves in determining the near-field on the aperture of the structure and the far-field radiation pattern of the structure. [ABSTRACT FROM PUBLISHER]

Ultracompact metamaterial-based cavity (thickness λ/15) is proposed to realize a low secondary lobes level and highly directive phased array antenna. The cavity is fed by an array of four patch antennas designed to operate at around 9.5 GHz. The radiation patterns of the phased arrays are compared with those of their respective metamaterial-based cavity antennas. The latter structures have lower secondary lobes and provide higher gain and directivity. Moreover, the cavities enhance the beam steering of the phased arrays. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2653–2656, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24709 [ABSTRACT FROM AUTHOR]

The analysis and design of subwavelength metamaterial-based resonant cavity antennas are presented. The antennas under investigation are formed by embedding a feeding source in a Fabry-Perot (FP) cavity composed of a Perfect Electrical Conductor (PEC) surface and a metasurface reflector. The embedded feeding source used in this study is a 2 × 2 microstrip patch array. The influence of the interelement spacing of the patch array feed on the radiation patterns is investigated and reported. The effect of the cavity thickness is also considered. Finally, the design of highly directive subwavelength cavity antennas is presented. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1883–1888, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24485 [ABSTRACT FROM AUTHOR]

A new dual-band Fabry-Pérot cavity (FPC) antenna consisting of a partially reflective surface (PRS) superstrate and an artificial magnetic conductor (AMC) substrate is proposed for low-frequency separation ratio. The main purpose of this antenna is to introduce more than -20 dB rejection band in between two very closely located service bands (up- and downlink bands) of Korean personal communication service (PCS). Additionally, with the help of metallic side walls enclosing all the openings between the superstrate and the substrate, we can obtain more than 10 dB realized gain throughout the two operation bands. Moreover, the selective behavior of the gain near the pass bands is highly increased and the back radiation is reduced remarkably. The effect of attaching the superstrate to the side walls on antenna performance is also analyzed. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1869–1872, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24509 [ABSTRACT FROM AUTHOR]

A new method is presented for increasing the separation between the radiating elements of a 1-D array antenna by incorporating it into a Fabry-Pérot type resonant cavity with artificial magnetic conductor (AMC) walls. The AMC walls create a more uniform distribution of field within the cavity and, moreover, eliminate diffracted fields. The concept is demonstrated via 3-D full-wave simulations as well as experimental measurements for a prototype antenna. Comparison between an antenna with AMC walls and an identical reference antenna, without walls, shows a reduction in the sidelobe level. An array element separation of 2λ is achieved whilst maintaining good radiation performance. The performance of the proposed structure is also compared to that of an antenna incorporating PEC walls. Finally, the effect of the side- wall and central AMC walls are considered separately in order to isolate their corresponding effect on the antenna performance. [ABSTRACT FROM AUTHOR]

Metallic electromagnetic bandgap resonator antennas are highly attractive to design very efficient primary feeds of focal array fed reflector antennas for space Tx applications. The antennas analayzed in this work consists of purely metallic Fabry–Perot (FP) cavities with a single partially reflecting surface (PRS) and four perfect electrical conductor (PEC) walls on the sides. They are excited by a standard metallic waveguide. In contrast to prior work, we focus our attention on compact FP resonators whose size is in the order of a few wavelengths in free space. Their radiation characteristics (namely, their resonant frequency, maximum directivity, aperture efficiency, and radiation bandwidth) are investigated numerically in X-band with the finite-difference time-domain method. The extensive study of their radiation performance as a function of their size and grid reflectivity of the PRS, as well as the comparison with the well-known characteristics of large FP antennas, highlight three main features that must be taken into account for an optimum design: (1) for a given grid reflectivity, the resonant frequency increases while reducing the size of the shielded resonator, (2) for a given size of the antenna there exists an optimum reflectivity maximizing the aperture efficiency, (3) at resonance, the beam radiated by a square cavity is not circularly symmetric. In particular, we have shown that, for a 2 × λo cavity, it is possible to reach a high-aperture efficiency (ηs = 80%) over a 2.8% (-1 dB radiation) bandwidth. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2216–2221, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22703 [ABSTRACT FROM AUTHOR]

The enhancement of directivity of a monopole located in a Fabry–Perot type cavity is studied. The analysis is based on the response of the cavity excited from its inside by electromagnetic waves. To validate the proposed antenna, an experimental prototype is designed, fabricated, and measured. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 12–17, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21249 [ABSTRACT FROM AUTHOR]

The input impedance of directive electromagnetic bandgap (EBG) resonator antennas is studied theoretically and experimentally at millimeter-wave frequencies. These antennas consist of a printed primary source illuminating a metallo-dielectric EBG radome through a free-space coupling region. A Fabry–Perot (FP)-type resonator with highly reflecting metallic strip gratings is used. The variations of input impedance, resonant frequency, and return loss at resonance are investigated as functions of the thickness of the coupling region, for various topologies of (i) printed sources (single- and double-layer patch antennas and arrays) and (ii) EBG cavities with a variable Q factor (that is, directivity). We also demonstrate that the coupling conditions are optimized when the resonator is fed by a relatively directive primary source (here, a 2 × 2 aperture-coupled patch-antenna array), rather than by a patch or a wire antenna, as is usually done. In that case, the required accuracy of the coupling region's thickness is much less stringent, which is essential from a practical point of view. These theoretical results are experimentally validated at 60 GHz through the characterization of several configurations of EBG antennas. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 369–375, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20144 [ABSTRACT FROM AUTHOR]

Compact focusing antennas, consisting of a Fabry–Perot (FP) cavity coupled to a printed source, are studied in the 60-GHz band. Several configurations of antennas, including plane-parallel or plano-convex cavities excited by a patch antenna or an array, are considered and compared. In particular, their radiation characteristics are investigated experimentally as a function of the operating frequency and the thickness of the free-space coupling region separating the primary radiator from the resonator. The optimum coupling conditions are also defined to maximize the efficiency and minimize the sidelobe level. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 438–443, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11084 [ABSTRACT FROM AUTHOR]

In this contribution, two semi-analytical methods are compared for computing the radiation characteristics of a Fabry–Perot cavity excited by an internal current line source. One method uses the leaky wave theory and the other method uses a ray analysis. Compared to the conventional ray method, the first method offers more accurate results without increasing computing time. A full-wave method is used as a reference. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1654–1656, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21692 [ABSTRACT FROM AUTHOR]