Reconfigurable Reflectarrays and Array Lenses for Dynamic Antenna Beam Control: A Review

Advances in reflectarrays and array lenses with electronic beam-forming capabilities are enabling a host of new possibilities for these high-performance, low-cost antenna architectures. This paper reviews enabling technologies and topologies of reconfigurable reflectarray and array lens designs, and surveys a range of experimental implementations and achievements that have been made in this area in recent years. The paper describes the fundamental design approaches employed in realizing reconfigurable designs, and explores advanced capabilities of these nascent architectures, such as multi-band operation, polarization manipulation, frequency agility, and amplification. Finally, the paper concludes by discussing future challenges and possibilities for these antennas.Comment: 16 pages, 12 figure

Technologies for Near-Field Focused Microwave Antennas

This paper provides a review spanning different technologies used to implement near-field focused antennas at the microwave frequency band up to a few tens of GHz: arrays of microstrip patches and printed dipoles, arrays of dielectric resonator antennas, reflectarrays, transmitarrays, Fresnel zone plate lenses, leaky-wave antennas, and waveguide arrays

Design And Practical Implementation Of Harmonic-Transponder Sensors

Harmonic radar is a nonlinear detection technology that transmits and receives radio-frequency (RF) signals at orthogonal frequencies, so as to suppress the undesired clutters, echoes and electromagnetic interreferences due to multipath scattering. Its implementation generally comprises a nonlinear tag (i.e, a harmonic transponder), which picks the interrogation signal at specific fundamental frequency (f0) and converts it into a high/sub-harmonic signal (nf0). Such a technology has been successfully applied to tracking small insects and detection of electrically-small objects in the rich-scattering environment. Similarly, a harmonic sensor is used to interrogate electrically-small and passive sensors, of which the magnitude and peak frequency of output harmonics (e.g., second harmonic) are functions of the parameter to be sensed. A harmonic tag or sensor comprises one or multiple antennas, a frequency modulator, a sensor, a microchip and matching networks. Here, we propose and experimentally validate compact, low-cost, low-profile, and conformal hybrid-fed microstrip antennas for the harmonics-based radar and sensor systems. The proposed 98 microstrip antennas are based on a simple single-layered and hybrid-feed structure. By optimizing the feed position and the geometry of microstrip patch, the fundamental mode and particular higher-order modes can be excited at the fundamental frequency and the second harmonic. We have derived the analytical expressions for calculating the antennas’ resonant frequencies, which have been verified with numerical simulations and measurements. Our results show that the proposed hybrid-feed, single-layered microstrip antennas, although having a compact size and a low profile, can achieve descent realized gain (1.2 – 3.5 dB), good impedance matching (return loss \u3c -15 dB), high isolation (\u3c-20 dB), and favorable co/cross-polarization properties. The proposed microstrip antennas may benefit various size-restricted harmonic transponders used for harmonic radars, harmonic sensors, medical implants, passive radio-frequency identification (RFID), and internet-of-things (IoT) applications

Towards an Advanced Automotive Radar Front-end Based on Gap Waveguide Technology

This thesis presents the early works on dual circularly polarized array antenna based on gap waveguide, also microstrip-to-waveguide transitions for integration of automotive radar front-end. Being the most widely used radar antenna, PCB antenna suffers from dielectric loss and design flexibility. Next generation automotive radars demand sophisticated antenna systems with high efficiency, which makes waveguide antenna become a better candidate. Over the last few years, gap waveguide has shown advantages for implementation of complicated antenna systems. Ridge gap waveguides have been widely used in passive gap waveguide components design including slot arrays. In this regard, two transitions between ridge gap waveguides and microstrip lines are presented for the integration with gap waveguide antennas. The transitions are verified in both passive and active configuration. Another work on packaging techniques is presented for integration with inverted microstrip gap waveguide antennas.Systems utilizing individual linear polarization (LP) that lack polarimetric capabilities are not capable of measuring the full scattering matrix, thus losing information about the scenery. To develop a more advanced radar system with better detectability, dual circularly polarized gap waveguide slot arrays for polarimetric radar sensing are investigated. An 8 78 planar array using double grooved circular waveguide polarizer is presented. The polarizers are compact in size and have excellent polarization properties. Multi-layer design of the array antenna benefits from the gap waveguide technology and features better performance. The works presented in this thesis laid the foundation of future works regarding integration of the radar front end. More works on prototyping radar systems using gap waveguide technology will be presented in future publications

2009 Index IEEE Antennas and Wireless Propagation Letters Vol. 8

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

2008 Index IEEE Transactions on Control Systems Technology Vol. 16

This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index

C-Ku-Band Dual-Polarized Array Element for Shared-Aperture Frequency-Scanning Array

Accurate now-casting and forecasting could prevent losses and reduce risks caused by severe weather. Key observation to improve our knowledge of the weather is the ocean vector wind. National Oceanic and Atmospheric Administration (NOAA) is embarking on an ambiguous but needed effort to launch a new satellite-based instrument called the Dual Frequency Scatterometer (DFS) that will provide accurate global mapping of the ocean vector wind in a timely manner. The Advanced Wind and Rain Airborne Profiler (AWRAP) can play a pivotal role for this mission by providing critical measurements to improve the geophysical model function that DFS will relay on to estimate the winds. AWRAP requires a novel antenna to collect dual-polarized, dual-wavelength measurements. This work develops a subarray for the AWRAP antenna that will enable it acquire the necessary measurements from the NOAA WP-3D aircraft. By sharing the aperture for both C (5.3 GHz) and Ku (13.8 GHz) bands, this antenna array utilizes the given circular area as efficiently as possible. In both bands, the array is capable of forming and scanning a narrow beam in the x-z plane in the range 40°-60° o normal within 10% of frequency bandwidth, for both vertical and horizontal polarizations. Each subarray consists of nine dual-polarized Ku-band microstrip patch antennas and two perpendicular C-band slot antennas, sharing the aperture. Microstrip patches and their stripline feed networks are integrated into an 8-layer printed circuit board (PCB) and the slots are formed on an aluminum plate under the PCB. The PCB covers the slots, but they can radiate through the openings in the ground planes of the PCB. The C-band slots are positioned between Ku-band patches every third patch spacing. In total, four separate feed networks are required to drive the antenna elements in two bands for two polarizations. In order to achieve lower loss and higher antenna efficiencies in a small space, several transmission line technologies (namely, rectangular waveguides, suspended striplines and striplines) are used to deliver the power to the antenna elements. In order to pass the signal between different media, a broad-band perpendicular E-plane waveguide-to-suspended stripline transition is designed and fabricated in Ku band. A frequency bandwidth of 12% and an insertion loss as low as 0.09 dB are achieved in measurement. Measured input return loss of the Ku-subarray is more than 9 dB in the entire frequency bandwidth and realized gains are better than 10 dBi. Cross-polarization levels are less than -20 dB in the lower frequencies. However, in the higher frequencies, cross-polarization levels increase to -15 dB. It is proposed to use mirrored feed technique to improve cross-polarization levels of the array. For the C-subarray, measured input return loss is better than 12 dB in the entire frequency bandwidth. Measured realized gain at the center frequency is -12 dBi, and cross-polarization level is better than -20 dB

Design and Analysis of Dual-Linearly Polarized Dielectric Resonator Antenna Array

Dielectric resonators have been widely used as narrowband shielded circuit components. The dielectric resonator antenna is an implementation of using an unshielded dielectric structure in order to extract the radiation of electric fields. Dielectric materials can have low dielectric loss and the absence of metallic surfaces also reduces conduction losses. A dielectric resonator antenna can have efficiencies above 95% for several hundred megahertz. The versatility in choice of shape, relative permittivity and size enables a whole spectrum of operating frequency ranges (1GHz-40GHz), sizes, radiation patterns and bandwidths. The far field radiation pattern is a characteristic of the resonating modes. In this project the investigation of dielectric resonator antennas was quantitatively realized by the design and evaluation of one omni-directional wideband dielectric resonator antenna with operating frequency range 3.9GHz to 6.2GHz and two dual linearly polarized broadside antenna arrays in L, S and C band applications. Transverse modes with rotational symmetry are preferred for an omni-directional radiation pattern, whereas a hybrid mode is suitable for a broadside radiation pattern. The modes can be excited by feeding from microstrip lines and coaxial probes. The location of the excitation determines what mode is excited. The resonant frequency is controlled by size, shape and permittivity of the DR element. Dual polarization is achieved by exciting two orthogonal modes simultaneously in the resonator. The cross coupling between the feeding networks and the matching of these becomes a crucial step in the design of a dielectric resonator antenna. The broadside antenna elements have been arranged in a linear as well as planar array to increase the directivity