Periodic Reporting for period 1 - ADVANTA (Toward a new generation of miniature multifrequency antennas using multiresonance platform based on subwavelength structures inspired by advanced metamaterials)
Reporting period: 2017-08-01 to 2019-07-31
Demand in miniature antennas has been growing over the last decades. A variety of modern applications like implantable antennas, miniature wireless sensors, internet-of-things (IoT) and multifunctional communication systems have stimulated this process. Development of miniature antennas for multiband operation is a trend in mobile communications. A modern smartphone has several functions that need several antennas in one device, to be used for WiFi, GPS, cellular network bands, etc., while its acceptable size is strongly restricted. One multiband antenna instead of many single-band antennas in one device is a good option, but size issues remain critical. Inexpensive small antennas which are well integrated with the other electronics are needed by the industry.
The overall objective of this project is to build a framework containing theoretical bases and efficient design procedures for miniature multiband antennas that may support multiple legacy communication standards. It is achieved by utilizing the specific properties of subwavelength resonators and planar metamaterials (metasurfaces) on their basis. The multiresonance concept and quantification of the scaling of resonance frequencies have been introduced to enable systematic design of multiband antennas. This allows us to fully exploit the advantages of the common miniaturizing effect of subwavelength resonators and a very-high-permittivity substrate to yield an alternative to commercial ceramic antennas. Design solutions for conventional substrates have been proposed for a large number of the subwavelength bands. Our theoretical framework has been experimentally proved for the designed compact antennas on a conventional substrate and ultra-miniature antennas on a very-high-permittivity substrate. It was applied to design antennas with two to six simultaneous operation bands in the frequency range from 0.8GHz to 10GHz, in order to enable cost-efficient solutions for the present and future needs of communication systems. A study of metasurfaces and related structures of the selected types has been performed to find the routes to further advancements and new scenarios of radiation manipulation.
The overall objective of this project is to build a framework containing theoretical bases and efficient design procedures for miniature multiband antennas that may support multiple legacy communication standards. It is achieved by utilizing the specific properties of subwavelength resonators and planar metamaterials (metasurfaces) on their basis. The multiresonance concept and quantification of the scaling of resonance frequencies have been introduced to enable systematic design of multiband antennas. This allows us to fully exploit the advantages of the common miniaturizing effect of subwavelength resonators and a very-high-permittivity substrate to yield an alternative to commercial ceramic antennas. Design solutions for conventional substrates have been proposed for a large number of the subwavelength bands. Our theoretical framework has been experimentally proved for the designed compact antennas on a conventional substrate and ultra-miniature antennas on a very-high-permittivity substrate. It was applied to design antennas with two to six simultaneous operation bands in the frequency range from 0.8GHz to 10GHz, in order to enable cost-efficient solutions for the present and future needs of communication systems. A study of metasurfaces and related structures of the selected types has been performed to find the routes to further advancements and new scenarios of radiation manipulation.
The conducted research includes, according to the specific objectives, (i) development of the multiresonance concept for subwavelength structures and quantification of the scaling of resonance frequencies, (ii) design and experimental study of ultra-miniature antennas with the combined effect of subwavelength resonators and a (very-)high-permittivity substrate; (iii) assessment of applicability of the ideas of Transformational Optics for design of ultra-miniature antennas, (iv) compact planar antennas based on the multiresonance concept, and (v) investigation of metasurfaces and related structures that (may) inspire multiband advanced antennas or sub-/superstrates for antennas, and metasurfaces inspired by the proposed antennas.
The multiresonance concept has been developed based on the guess that multiple subwavelength resonators may provide such a high field confinement that they work rather separately from each other in one antenna, or affect each other in a desirable and predictable way. Quantification of the scaling of resonant frequencies, which occurs at substrate’s permittivity variation and fixed size of the substrate-resonator block of antenna, has been introduced. The obtained results allow us to understand and exploit the specifics of the scaling in the open resonance structures and, consequently, justify a particular permittivity range needed to choose a proper substrate material when the maximal size of the antenna is strictly limited. Various natural materials have been assessed as substrates of ultra-miniature antennas for the range between 0.8 and 10 GHz. The choice has been made in favor of lithium niobate (LiNbO3), an affordable high-permittivity material (diagonal components of the relative permittivity tensor are 43, 43, and 28), which is widely used in electro-optics but not yet in ultra-miniature antennas. Fabrication steps are well developed for this material that makes it a perfect candidate for practical use. To validate the concept, an ultra-miniature dual-band monopole antenna on LiNbO3 substrate has been designed, fabricated, and studied experimentally. The antenna has an unusually small size: side size of its substrate-resonator block is just 1/24 of the wavelength at the lowest operating frequency (around 2.8 GHz). The obtained efficiency of 8-10% is acceptable for such small antennas. Good coincidence of the experimental and numerical results has been achieved. Some ideas of Transformational Optics approach were examined for possible use in design of ultra-miniature antennas.
The multiresonance concept has been adapted to the compact planar antennas on a conventional commercial substrate (Roger 5870, relative permittivity is 2.33). Several antennas having up to six bands were designed, whose unusual feature is that the subwavelength resonators are placed on the both sides of the substrate. This is crucial for compactness of the antenna since the maximal size is strictly limited. Almost arbitrary mutual location of the bands can be obtained for a given size of the substrate-resonator block. For the demonstration purposes, two antennas with three and four bands were fabricated and experimentally tested. The results are in good coincidence with simulations. The experiments demonstrate the usefulness of these antennas for sensing. All experimentally tested antennas were fed by a standard coaxial but are flexible regarding the feeding scheme.
Metasurfaces which (may) inspire advanced antennas and substrates and superstrates for radiated wavefront manipulation were studied. In turn, the designed ultra-minature/compact antennas were considered as unit cells of future metasurfaces. The transmission, reflection, absorption, and polarization conversion properties of the metasurfaces of the selected types have been studied in detail by means of numerical simulations. Connection between the properties of metasurfaces and their unit cells was demonstrated. Sample metasurfaces were designed for the purposes of future research.
The multiresonance concept has been developed based on the guess that multiple subwavelength resonators may provide such a high field confinement that they work rather separately from each other in one antenna, or affect each other in a desirable and predictable way. Quantification of the scaling of resonant frequencies, which occurs at substrate’s permittivity variation and fixed size of the substrate-resonator block of antenna, has been introduced. The obtained results allow us to understand and exploit the specifics of the scaling in the open resonance structures and, consequently, justify a particular permittivity range needed to choose a proper substrate material when the maximal size of the antenna is strictly limited. Various natural materials have been assessed as substrates of ultra-miniature antennas for the range between 0.8 and 10 GHz. The choice has been made in favor of lithium niobate (LiNbO3), an affordable high-permittivity material (diagonal components of the relative permittivity tensor are 43, 43, and 28), which is widely used in electro-optics but not yet in ultra-miniature antennas. Fabrication steps are well developed for this material that makes it a perfect candidate for practical use. To validate the concept, an ultra-miniature dual-band monopole antenna on LiNbO3 substrate has been designed, fabricated, and studied experimentally. The antenna has an unusually small size: side size of its substrate-resonator block is just 1/24 of the wavelength at the lowest operating frequency (around 2.8 GHz). The obtained efficiency of 8-10% is acceptable for such small antennas. Good coincidence of the experimental and numerical results has been achieved. Some ideas of Transformational Optics approach were examined for possible use in design of ultra-miniature antennas.
The multiresonance concept has been adapted to the compact planar antennas on a conventional commercial substrate (Roger 5870, relative permittivity is 2.33). Several antennas having up to six bands were designed, whose unusual feature is that the subwavelength resonators are placed on the both sides of the substrate. This is crucial for compactness of the antenna since the maximal size is strictly limited. Almost arbitrary mutual location of the bands can be obtained for a given size of the substrate-resonator block. For the demonstration purposes, two antennas with three and four bands were fabricated and experimentally tested. The results are in good coincidence with simulations. The experiments demonstrate the usefulness of these antennas for sensing. All experimentally tested antennas were fed by a standard coaxial but are flexible regarding the feeding scheme.
Metasurfaces which (may) inspire advanced antennas and substrates and superstrates for radiated wavefront manipulation were studied. In turn, the designed ultra-minature/compact antennas were considered as unit cells of future metasurfaces. The transmission, reflection, absorption, and polarization conversion properties of the metasurfaces of the selected types have been studied in detail by means of numerical simulations. Connection between the properties of metasurfaces and their unit cells was demonstrated. Sample metasurfaces were designed for the purposes of future research.
The progress achieved beyond SOTA is mainly determined by but not restricted to that (i) the multiresonator concept and quantification of the scaling of resonance frequencies in open resonance structures were introduced as the theoretical bases for multiband antenna design in the subwavelengh range; (ii) connection between the required extent of miniaturization and choice of substrate material is systematically studied; (iii) common effect of subwavelength resonators and (very-)high-permittivity substrates on the miniaturization extent was estimated and used in the experimentally studied dual-band ultra-miniature antenna; (iv) potential of lithium niobate as the substrate is experimentally justified; (v) the strategy of maximizing the number of subwavelength bands at fixed antenna size was developed; (vi) compact multiband planar antennas with subwavelength resonators placed on the both sides of the substrate were designed and experimentally studied; (vii) simple design rules enabling rather arbitrary spectral location of the operation bands were derived; (viii) new metasurfaces with capability in mechanically tunable polarization manipulation were designed; (ix) concept of electromagnetic disappearance has been introduced for the tunable meta-arrays.