Terahertz Dielectric Resonator Antennas for High Speed Communication and Sensing: From theory to design and implementation
Terahertz dielectric resonator antennas (DRAs) provide ultrafast data transfer rates using large bandwidth and multimode operations, which make them ideal for high speed communication due to their low loss and high efficiency. They can work at microwave, terahertz or optical frequencies, and are compact in size, which makes them well suited for advanced applications in sensing, scanning and imaging. New geometries are being developed for conical optical DRAs, cylindrical optical DRAs and spherical optical DRAs. Spherical optical DRAs have features of super directivity which can be used in quantum radars. Cylindrical optical DRAs with photo diodes can be used for wireless energy harvesting. This book covers the theory, modelling, design and implementation of DRA technologies at the microwave, terahertz or optical regime for future applications in wireless high-speed communication, wireless personal communication and sensor networks. Case studies on new geometries with prototype models are included at the end of this book.
Inspec keywords: eye; dielectric resonator antennas; plasmonics; microwave antennas; antenna radiation patterns
Other keywords: plasmons; eye; permittivity; surface plasmons; plasmonics; high speed communication; broadband antennas; microwave antennas; dielectric materials; antenna radiation patterns; sensing; terahertz dielectric resonator antennas
Subjects: Other dielectric applications and devices; Antennas; General electrical engineering topics
- Book DOI: 10.1049/PBTE103E
- Chapter DOI: 10.1049/PBTE103E
- ISBN: 9781839533556
- e-ISBN: 9781839533563
- Page count: 415
- Format: PDF
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Front Matter
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1 Dielectric resonator antennas (DRAs) and its synthesis
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Dielectric resonator antenna (DRA) has high efficiency and low losses at high frequencies. Terahertz (THz) and optical DRA are new trend topics of research in millimeter wave (mm wave), optics and photonics. They are simple in design, highly efficient, built with high dielectric constant ceramics and polymers materials (εr = 10-1,600), have design flexibility, easy to fabricate and stable operations at high temperatures. DRAs have excellent features of working throughout the frequency spectrum, right from microwave to the optical regime. Light (photons) are bosons and metal (electron-positrons) at terahertz frequency, metal acts as gaseous (plasma) at terahertz frequencies; hence it is termed fermions. The plasmon frequency gets coupled to terahertz DRA (TDRA) in proximity feed thus creates radiations in TDRA at its resonant frequency. Bosons and fermions scattering, and transportation mechanism can be solved by giving quantum-mechanical treatment to these TDRAs. Dirac and Maxwell's equations have used to get desired solution using creation and annihilation operators' theory. Electromagnetic (e.m.) far fields are solved as desired outcome. The radiation pattern is based on input to feed, current density fluctuations and retardation potentials. The fluctuations in quantum antennas must be controlled to minimum threshold value. The radiated field is a state of jointly coherent for the bosons (i.e., photons) and for the fermions (positrons-electrons). These are basic concept of radiations into DRAs at terahertz and optical frequencies. Hence, interaction between these bosonic and fermionic fields causes the e.m. field to change and induce surface currents that radiate out in space. This change in e.m. fields must be optimized to a threshold value. Light-imaging detection and ranging operates at 200-THz frequency. Polymer, ceramics and polymer composites can be used at mm wave or terahertz and optical frequencies. TDRA can be built with low-quality factor materials, and absorbers are designed using materials having high-quality factor materials. In TDRAs, input is LASER, it interacts with noble metals such as gold or silver, light-matter interaction takes place resulting into surface plasmon resonance. The silver nano waveguides have been used to provide feed mechanism to TDRAs of different shapes and geometries, i.e., cylindrical, rectangular, spherical and conical shape DRAs. LASER input interacts with silver metal and dielectric SiO2 substrate. Hence, in TDRA, surface plasmon polytron waves are generated due to light-matter interaction, these will give rise to plasmon frequency generation. This plasmon frequency is always kept lesser than LASER input frequency, so as to enable it to propagate in forward direction. Here, we propose a TDRA fully integrated with a photonic crystal waveguide for broadside radiation pattern.
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2 Dielectric resonator antennas—a comprehensive review
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Design and implementation of a dielectric resonator antenna (DRA) using ceramic materials having permittivity greater than ten have been used for multiple applications such as mobile communication, radars and satellite communication. Various techniques have been suggested for circular polarization. Trends of getting higher gain by exciting higher order modes have been used in microwave DRAs. Wide bad DRAs have been developed by mode merging techniques. Aspect ratios of 0.5-2.5 have been used in rectangular designs of DRA for exciting multimodes. Rectangular DRA reported as a favorable choice of many designers for simplicity. Terahertz DRA can be developed as miniature DRAs, they can offer high speed and high data rate for communication applications at terahertz or optical frequencies. DRAs at photonic wavelength can be used as artificial retinal photoreceptors and energy harvesting. Also, terahertz frequency can result into wide bandwidth and shall be able to provide terabits per second data rate. In this chapter, a comprehensive review on microwave, terahertz and optical DRAs has been surveyed. Terahertz is new technology, and developing this hardware is complex and requires high-resolution fabrication. Its fabrication is costly due to sophisticated fabrication infrastructure, i.e. an LPKF laser machine can be used to design antennas up to 50 μm. The manufacturing cost can be minimized once technology is matured and large-scale industrial production is taken up.
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3 Light–matter interaction in terahertz dielectric resonator antennas (DRA)
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Photons interact with atoms, molecules and other particles of metals and air particles in space or environment, out of which the phenomenon of scattering, absorption, polarization, coupling, propagation, creation and annihilation takes place. Transportation photons and particles takes place in temporal-spatial domains. Boltzmann coupled with Maxwell's equation can thus provide exact solution of wave propagation and quantum fields operators. Also, Schrödinger equation can provide solution to photon fields. Skin effect is dominant in photonic devices, and nonlinear phenomenon also gets introduced at optical spectrum. The solution of electromagnetic wave propagation and fields quantum is different from classical microwave regime. In this chapter, mathematical modeling of quantum fields generation, interaction and propagation has been developed and analyzed. The Dirac equation has been used to determine quantum wave fields. Human eyes have retinas with 5 million of cones of photonic wavelength in central part and 126 million rods in peripheral part to receive photons. They form vision by capturing any image from the real world. They are also known as photo receptors. In brief, light-matter interaction in retinal part takes place, conversion of phonic signal into electrical impulses takes place, now these electrical pulses get accumulated and travel through optical nerves and carry composite signal to brain, which further gets converted into pixels and thus image is formed. Light scattering and propagation solution is provided by Drude's model. Quantum entanglement is another important phenomenon to be used for quantum communication. This is also used for secure quantum communications.
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4 Terahertz dielectric resonator antennas design and modeling
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Theory of operation of a terahertz (THz) dielectric resonator antenna (DRA) is explained and mathematical expressions for rectangular DRA, spherical DRA, cone DRA and cylindrical DRA are broadly given in this chapter. THz emission is produced solely by the photo-induced current in the silicon (Si) DRAs, also telecom wavelength of 1,550-nm DRA is presented. Our finding is that THz waveforms are lower than those for pumping at 1,100 nm, due to the nonuniform absorption of different parts of the excitation spectrum that is also called plasmon frequency. DRAs exhibit an infinite number of resonant modes. In this chapter, the development of high-efficiency DRAs at optical frequencies and THz frequencies has comprehensively explained using mathematically equations for optical currents densities and quantum fields.
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5 Surface plasmon polytrons (SPP) into terahertz DRA
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Surface plasmonic resonance occurs at interface of metal and substrate at terahertz frequencies. The terahertz's wavelength is located between the microwave and the infrared region of the electromagnetic spectrum. Optical wavelength falls after infrared region. Terahertz DRA (TDRA) makes use of surface plasmon polytron (SPP) phenomenon for the excitation of dielectric resonator antenna (DRA). The Drude model helps to characterize TDRA, when switching from microwave to terahertz frequencies. Drude's scattering is function of frequency, resistance and conductance at photonic wavelength. Here, photon's generation is classified by bosonic fields or fermionic fields. The nonlinearity of photons is described by Dirac second quantized field equations. Feynman path integral gives know-how about particle's moment fluctuations. Correlation coefficient manipulation provides proper beam formation. Photon's spin is the main cause of nonlinearity in terahertz antennas. Optical spectrum has frequencies from 1013 to 1015 Hz. Optical DRA can couple optical energy into plasmonic resonance and vice versa. Plasmon resonance thus becomes the main cause of excitation to TDRA. Terahertz antennas that involve SPP phenomenon for radiations can provide highly directive radiation pattern and high gain.
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6 Terahertz conical dielectric resonator antenna—design, simulation and implementations
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Terahertz conical dielectric resonator antennas (DRAs) have been designed, simulated and analyzed at a terahertz spectrum, i.e. 10 THz. A lower terahertz frequency band is useful for high data speed communication, whereas a terahertz frequency upper band is used for optical sensors or sensing applications. The free-space wireless communications also use terahertz DRAs (TDRAs). A unique and novel geometry for terahertz dual-band operations has been investigated with mathematical formulations. The comprehensive analyses in a terahertz regime have been worked out with a reflection coefficient (S 11), a voltage standing wave ratio, a radiation pattern and efficiency using a conical TDRA. The conical TDRA is designed at 10 THz frequency with 4.9 dBi, gain and bore sight radiation pattern. The equivalent circuit of conical TDRA has been developed at given frequencies.
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7 Cylindrical terahertz and optical DRA—design and analysis
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Terahertz cylindrical dielectric resonator antennas (DRAs) have been studied and implemented using computer simulation technology. The theoretically analyses have also been performed at terahertz frequency. Mathematical formulation for the Poynting vector and far fields radiated pattern for terahertz antennas have been developed. Their simulation results along with theoretical concepts have been presented. The work carried out in this chapter is much useful for high-speed communication applications and retinal artificial photoreceptors applications. This optical DRAs work can also be used for sensing, scanning, imaging and chip-to-chip communications. The cylindrical optical DRAs have been built at 521 THz with a gain of 4.04 dBi. Another optical DRA has also been developed at 10 THz with 6-dBi gain. Simulated results on both optical DRAs have been included in this chapter. Antenna parameters such as reflection coefficient (S 11), radiation pattern, voltage standing wave ratio, impedance (Z11) plots along with other antenna results are included in this chapter. These are compact antennas and suitable for 5G and beyond networks for providing better connectivity with lower RF exposer levels.
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8 Spherical terahertz and optical DRA—design and implementations
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In this chapter, terahertz spherical DRA (dielectric resonator antenna) has been simulated for radiation parameters and its mathematically modeling is carried out. The terahertz DRA has been simulated at 511 THz. This frequency corresponds to a visible spectrum, and suitable for LiDAR and retinal photoreceptor applications. One more model has been developed at 10 THz. The spherical DRA is built with silicon (εr = 11.9) materials, and analyses on exciting higher order modes have been carried out. It has a gain of 18 dBi, in which multipole generation has been observed. Two separate models (silicon and titanate) at optical frequencies have also been developed and validated with 2.4-dB gain using computer simulation technology. Multi-input-multi-output spherical DRA has also been realized at 10 THz to get excellent directivity. Mathematical formulation on super directivity is also formulated. The proximity coupled feed has been used with laser input, and Gaussian beam excitation. The silver nano waveguides have been used in the modelling to provide feed to terahertz DRAs of different geometries, i.e. spherical DRA, etc. LASER input interacts with silver metal and dielectric SiO2 substrate.
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9 Rectangular terahertz DRA—design, simulation and implementations
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In this, design and implantations of a terahertz rectangular dielectric resonator antenna (DRA) using an HFSS simulator has been presented. The aspect-ratio has played a deterministic role for exciting desired multiple resonant modes at terahertz frequencies. The design has large bandwidth hence can be used for high-speed communications and terahertz sensors. It is simple due to rectangular geometry, efficient due to use of DR, compact due to terahertz frequency and unique using silicon as a radiator. Mathematical modeling of 10-THz frequency using a terahertz DRA is presented along with simulations results of S 11 below -10 dB, gain of 4.89 dBi with good radiation pattern, which have been validated. DRAs at photonic wavelength have also been developed for 511-THz frequency with all desired parameters and simple geometry. These DRAs fall within visible frequency; hence they can be used as artificial retinal photoreceptors. A DR material has advantages over metallic antennas as they can operate with stability from microwave to optical regime. These optical antennas can be suitable for wireless transmission of TBPS data rate. Also, coherent states and control at optical frequencies have been formulated mathematically with unique characteristics at terahertz frequency.
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10 Equivalent circuit analysis on terahertz and optical dielectric resonator antennas (DRAs)
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In this chapter, an equivalent R-L-C circuit for terahertz and optical dielectric resonator antenna (DRA) has been developed. The behavior of characteristics modes in response to resonance frequency, input impedance and quality factor has been formulated. Higher order resonant modes in terahertz DRA has been depicted with circuit concepts. The terms, such as quality factor, bandwidth, resonance frequency and selectivity in quantum circuits, have been comprehensively investigated in quantum circuits input impedance that is complex and nonlinear, the real part of which is a function of frequency. The dynamic impedance at terahertz frequency involves skin effect. The authors have developed R, L, C (resistor (R), inductor (L) and capacitor (C)) equivalent circuit for terahertz and optical DRAs. These investigations are useful for the theoretical modeling of optical DRAs that shall help designers during the design stage. Their comprehensive analysis and study of quality factor, bandwidth, resonant frequency and selectivity in quantum circuits have been illustrated. The mathematical formulations for antenna and absorber conditions have been worked out. Maximum resistance condition in R, L, C circuit-favored absorber designs and minimum resistance conditions have been found suitable for antenna functions. These investigations also depict the phenomenon of higher order resonant modes in terahertz DRA. These resonant modes can be modulated to get merged modes or controlled separated modes to provide wide bandwidth or narrow bandwidth in antenna designs.
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11 Optical DRA for retinal applications—next generation DRAs
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Human eye retinas have millions of cones and rods cells, also known as photoreceptors, to receive photons from the nature. There are arrays of photoreceptors on retina periphery and central part of retina. These cells perform functions of photonic antennas, for example they receive light particles and convert it into electrical impulses. In this chapter, cones and cylindrical rods have been studied and analyzed as photonic wavelength antennas. These terahertz dielectric resonator antennas (DRAs) have been developed using HFSS and CST simulators. Their simulation modeling and theoretical modeling have been presented in this chapter. The work carried out in this chapter is much useful for the development of artificial retinal antennas for possible use in retinal prosthesis using terahertz DRAs and photodiodes as bio-photoreceptors. These DRAs at terahertz frequencies can also be used in applications of scanning, imaging and wideband ultrahigh-speed communication systems.
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12 Conclusion and futuristic vision
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The dielectric resonator antennas (DRAs) have capabilities to operate at low frequencies, microwave frequencies, terahertz frequencies as well as optical frequencies. These DRAs possess low loss, design flexibilities and efficient radiation mechanism even at high temperatures. DRAs have recently been integrated with an Apple i-phone 12 mobile phone antenna at millimetric-wave frequencies for 5G applications, i.e., 28 GHz. These DRAs can operate higher order modes in addition to fundamental modes. They can provide reconfigurable antenna characteristics and wide bandwidths. DRAs have mode control mechanism. They can provide physical insights during design stage itself. They are versatile due to availability of many dielectric constant materials. They can use DR values ranging from 10 to 1,600. These DRAs can have two different aspect ratios to extend design flexibilities. Resonant modes merging is another important feature available to designer. Absorbers are used as artificial photosynthesis and energy-harvesting solar curtains can be developed using DR absorbers. They are in use for developing photonic devices. Sapphire antennas can be used for esthetic design and used for wearable sensors such as rings. DRAs can also be used as LiDAR in autonomous cars and self-driving vehicles. DRAs have been used for artificial leaves for photosynthesis and rectennas for energy-harvesting application. They are being used as absorbers. Solar curtain is another application for energy harvesting. These solar curtains shall become boon to green buildings, smart homes and smart cities. They can provide clean energy for domestic use. Designing retinal DRAs is another era of Hi-Fi. These can become futuristic DRAs/antennas arrays as a substitute of rods and cones in human eye retina as implants. They can very well be used for sight restoration or eye prosthesis. The other field of applications of DRAs can be agriculture and environmental. Namely, moisture sensor, rain sensor, temperature sensor, carbon monoxide gas sensor can be developed using DRA. Scanning and imaging is another field where terahertz DRA can be used for service to the society.
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Appendix A: Case studies
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Appendix B: Terahertz absorbers
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Appendix C: Antenna measured values in anechoic chamber
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Appendix D: Dielectric materials and resources
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Appendix E: Dual-band graphene antenna design and implementation
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Appendix F: Miniaturization design techniques
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Appendix G: Gaussian beam feed process
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Appendix H: Silicon dielectric resonator antenna at 5-THz frequency
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Appendix I: DRA designing process
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Appendix J: DRA design case study
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Appendix K: Vector network analyzer process for calibration
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Back Matter
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