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A millimeter-wave (mm-wave) system architecture with enhanced-gain antenna solution is proposed for fifth-generation (5G) wireless communications. To enhance the antenna gain, the surface wave currents are converted to constructive far-field radiations through a novel two-stage metallic and dielectric rings. By applying low-profile dielectric ring, the electric near-field distributions of the grounded quarter-wavelength metallic ring are modified to create radiation apertures with appropriate polarization and orientation. The mutual coupling between transmit/receive antennas and cross polarizations is reduced by 7 and 5 dB, respectively, and the gain is enhanced over 4 dB. Low-loss mm-wave transitions are implemented in a standard FR-4 printed circuit board and in an interposer substrate to integrate the active antenna with the rest of the wireless system on a compact universal serial bus (USB)-interface platform. To evaluate the interposer package and define the output power of the embedded 60-GHz RF IC, an evaluation module with a standard WR-15 waveguide interface is designed and implemented. A prototype of the architecture, which is entirely realized using low-cost organic substrates, is presented and evaluated by experiments. Excellent correlations are achieved between simulations and measurements, demonstrating more than 25 dBm of equivalent isotropically radiated power (EIRP) over the unlicensed 60-GHz frequency band. [ABSTRACT FROM AUTHOR]

Compact phased-array antennas embedded in flip-chip ball grid array (BGA) packages are proposed to operate over the unlicensed 60 GHz frequency band. Radiation properties are enhanced by designing novel corrugated soft-surface structures and implementing them using the low-temperature co-fired ceramic process with no extra cost and fabrication complexity. This is achieved by adjusting via land diameters of periodic grounded vias in top four layers of the package, which in fact create perfect magnetic boundaries between the phased-array antenna elements to modify the electric near-field distributions and consequently improve far-field characteristics including gain, cross polarization, sidelobe level, and beam steering. Low-loss transitions from flip-chip IC to antenna elements are designed with less than 0.1 dB amplitude and 2° phase imbalance over 50–70 GHz. Prototypes with/without soft-surface structures are fabricated to work with flip-chip ICs with/without switches. A USB-interface adapter and a waveguide-interface module with a compact vertical power combiner are proposed for the first time to experimentally evaluate the phased-array antenna while connected to the flip-chip RF IC. Significant miniaturizations and improvements are achieved over the wide frequency range of 56–67 GHz, demonstrating up to 7 dB reduction in sidelobe level, up to 4 dB reduction in cross polarization, and up to 3 dB enhancement in gain at different directions. [ABSTRACT FROM AUTHOR]

Miniaturized transparent metallodielectric resonator antennas are developed and integrated on amorphous silicon solar cells. The horizontal metallic strips attached on the sidewalls of transparent low-profile dielectric resonators are used to manipulate electric near-fields and achieve novel dominant modes that represent miniaturized narrowband, wideband, or multiband antennas with various far-field properties. The radiation properties of each mode can also be adjusted to suit a prospective application by a simple change in position and/or size of the strip. The horizontal strip on the sidewall can be as narrow as one twelfth of the resonator height, and the top wall of the resonator is always kept clear to maximize the solar cell efficiency. A comprehensive comparison including far-field, near-field, and impedance properties of different modes is presented. Several prototypes of the integrated antennas were fabricated and tested. The experimental results are along with the theoretical achievements showing miniaturized antennas with maximum dimension as small as $0.18\lambda $ and multimode operation with realized gain higher than 6 dBi. [ABSTRACT FROM PUBLISHER]

Thick film screen-printing technology is employed to introduce planar dielectric antennas. The micron-size-thick film is made from high-permittivity dielectric paste, which is printed on a low-loss low-permittivity microwave substrate to operate as a magnetic wall boundary. A simplified theoretical model is developed to analyze the antenna structure. The accuracy of this model is evaluated by the results of a commercial three-dimensional (3-D) electromagnetic field solver. The model works well with less than 5% deviation from time-consuming simulations, providing the permittivity contrast between the film and substrate is kept high (e.g., > 30). The impact of dielectric loss of the film in antenna performance is significantly less than that of the substrate, allowing medium-loss films (e.g., \boldsymbol\varepsilon^\prime\prime = 3) results in highly efficient antennas with over 95% radiation efficiency. A prototype was made using screen printing and experimentally characterized at Ku-band. The experimental results confirm the theoretical achievements. The measured -10\;\textdB impedance bandwidth of the printable planar dielectric antenna having dimensions of 0.2 \boldsymbol\lambda0 \times 0.2 \boldsymbol\lambda0 is over 10% with a measured gain ranging from 4.5 to 5.5 dBi. Broadside radiation patterns with cross polarization levels of lower than - 20\;\textdB are achieved. This process is compatible with low-temperature cofired ceramic (LTCC) technology where similar idea can be applied to other passive microwave components. [ABSTRACT FROM PUBLISHER]

A new approach is introduced to show that bulk polymers with metallic plates/strips can be employed to design compact lightweight resonator antennas. A new fundamental mode is excited inside the polymer, based on the special boundary conditions enforced by the metallic plates and strip. By properly adjusting the physical parameters (e.g., the gap between metallic plate and strip), the mode is excited in an appropriate shape and significant miniaturization along with good radiation performance is achieved. An antenna structure is fabricated using acrylic $({{\varepsilon}_{r}} = 3)$ and the measured results are compared with the results of other compact antennas, which can be realized using very high-permittivity materials. Besides over 70% reduction in weight, outstanding antenna features such as 10% impedance bandwidth, 5.7 dBi gain, over 90% efficiency, and dimensions smaller than $\lambda/6$, make the proposed approach more suitable for designing compact lightweight antennas. [ABSTRACT FROM AUTHOR]

Planar microwave components are very desirable for many applications and are mainly realized by metallic structures. In this work, a planar dielectric waveguide is proposed. A high-permittivity micrometer-size thick film is patterned on a low-loss microwave substrate and is considered as a nearly perfect magnetic wall to realize the waveguide structure. The permittivity contrast between the film and substrate is kept high (e.g., >\30) in order to minimize the leakage power, and consequently, the insertion loss. The waveguide structure is theoretically analyzed using an approximation method and the results are confirmed by a simulation-based numerical method. The impact of dielectric loss of the film in waveguide performance is much less than that of the substrate, allowing waveguides with films having a medium or high loss (e.g., \varepsilon^\prime\prime = 3) result in a low insertion loss (e.g., up to 0.04 dB/mm at 40 GHz). Several prototypes are fabricated by screen-printing of barium–strontium–titanate (BST) pastes and characterized at 40 GHz. Using the extremely lossy BST film (\tan \delta = 0.2, \varepsilon^\prime\prime = 70), the insertion loss of the waveguide is measured to be 0.18 dB/mm. Based on the current technologies, the printable planar dielectric waveguide can achieve 0.08 dB/mm in insertion loss. Further improvements are expected in the future as the materials and fabrication technologies progress. [ABSTRACT FROM PUBLISHER]

Dielectric resonator antennas (DRAs) excited by tall microstrip transmission lines (TMLs) are investigated. Two different TML-DRA structures are proposed and the impact of TML parameters on the antenna performance is studied when low-loss and lossy substrates are used. To validate the effectiveness of this approach, a set of prototype antennas was fabricated, measured and compared with simulation results. A good agreement is obtained. It is found that by adjusting TML parameters, excellent impedance matching and coupling to low-permittivity DRAs are achieved even on high-permittivity substrates. The impedance bandwidth of a single-mode simple-shape rectangular DRA with εrd = 9 can be as high as 25%. The radiation efficiency of the antenna on extremely lossy substrates is significantly improved and based on the measured results over 80% efficiency with a gain ranging from 4.2 to 5.5 dBi along the impedance bandwidth can be expected. Since TML is a low-loss transmission line, the DRA is a low-loss radiator and low-permittivity DRAs can be well matched by TML, the TML-DRA forms an excellent wideband antenna system with high radiation efficiency. [ABSTRACT FROM AUTHOR]

As the permittivity of dielectric resonators decreases, it becomes difficult to feed the dielectric resonator antennas (DRAs) using direct microstrip lines. The variation of the resonant input resistance with the feed location becomes smaller, while the maximum achievable peak resistance dramatically drops to lower than 50 \Omega in most cases. To satisfy the impedance matching, field matching, improve coupling to low-permittivity dielectric resonators, and further increase the antenna bandwidth associated with the dominant mode, without disturbing far-field properties, tapered microstrip line-fed DRAs are proposed, designed, fabricated and evaluated in this communication. Both measurements and simulation investigations are presented and the results are compared with other forms of microstrip feed lines. The impedance bandwidth can be 75% larger than the bandwidth achieved by the step-shape microstrip-fed DRA. Symmetrical radiation patterns with low cross-polarization levels (lower than -22 dB) and a gain ranging from 4.9 to 6.8 dBi, within the impedance bandwidth of the antenna, are observed in the measurements. It is also shown that the proximity coupled tapered microstrip line is an ideal feeding for high-permittivity DRAs in situations where the microstrip line cannot be positioned underneath the dielectric resonator. To verify, one such antenna is designed, simulated and experimentally investigated, obtaining satisfactory results. [ABSTRACT FROM AUTHOR]

The goal of this paper is to investigate the electrical properties of photoresist-alumina microcomposites with different portions of ceramic content. Substrates of photoresist-alumina microcomposites are fabricated and a comprehensive analysis is performed to characterize their dielectric constant and dielectric loss tangent at microwave frequencies up to 40 GHz. To evaluate the performance of these materials for microwave applications, the properties of various lithographically fabricated antenna elements are examined and analysed based on the measured electrical properties. The experimental results show that the electrical properties of the photoresist composite are nonlinearly affected by ceramic content and also a minimum percentage of ceramic portion is required to improve the electrical properties of the photoresist composite. For instance, comparison of 0 wt% with 23 wt% SU8-alumina shows that no reduction is achieved for the dielectric loss tangent. Comparison of 38 wt% with 48 wt% SU8-alumina microcomposite shows that the dielectric loss tangent is improved from 0.03 to 0.01 and the dielectric constant is increased from 3.8 to 5.0 at 25 GHz. These improvements can result in superior performance for the photoresist-based microwave components. [ABSTRACT FROM AUTHOR]

The goal of this study is to present a simple model based on the ring-resonator technique to measure nondestructively the permittivity and loss tangent of dielectric materials. The proposed measurement model utilizes a modified ring-resonator technique in one-layer and two-layer microstrip configurations. This method eliminates the requirement to metalize the samples and enables characterization of permittivity and dielectric loss from 2 to 40 GHz. The effects of conductor and radiation losses that may introduce significant errors in the calculation of the loss tangent, especially at very high frequencies, are minimized. The measurement precision is evaluated by comparing the results with those obtained by using two well-known standard techniques. Uncertainties associated with the proposed model are addressed. [ABSTRACT FROM PUBLISHER]

The goal of this communication is to maintain wide impedance bandwidth white miniaturizing a microstrip-fed dielectric resonator antenna (DRA). The approach of using high aspect ratio structures is proposed, discussed, and compared with the two segmented structures approach. Finite element method parametric study of high permittivity high aspect ratio structures is used to demonstrate how two appropriate resonant modes can be merged to obtain miniaturized antennas with broadband operation, stable radiation patterns, and low cross polarization levels. To show the effectiveness of the approach, a set of microstrip-fed two segmented and high aspect ratio DRAs is fabricated, characterized, and the results are compared with Ansoft HFSS simulations. A high aspect ratio DRA with cross section as small as 0.08λ by 0.12λ has better than 11 percent bandwidth and is especially attractive for compact array applications. [ABSTRACT FROM AUTHOR]

Two segmented dielectric-resonator antennas have been investigated. A weighted average model is used to predict the resonant frequency. A simple method is then introduced to optimize the lower segment of the antenna. Finally, a fast and efficient design algorithm is presented. Three examples are used to implement the methods and the algorithm in three different frequency bands. Impedance bandwidths of up to 30% are achieved with the optimum design. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 533–537, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20871 [ABSTRACT FROM AUTHOR]

Novel photoresist-based artificial bulk dielectrics with tall-embedded metal grids are investigated and their radiation characteristics are studied in detail. The embedded metal grid substantially increases (around six times) the effective permittivity of the low permittivity base photoresist material, and enables excitation with a simple direct microstrip feed to radiate effectively at frequencies similar to a high-permittivity dielectric resonator antenna (DRA). Moreover, the grid changes the near fields inside the resonator and introduces novel modes that are completely different than those of usual DRAs. A set of artificial resonator antennas is designed, lithographically fabricated, and measured to demonstrate the new modes resonating at 17 and 19 GHz with 2% and 6% bandwidth and 7.6 and 6.6 dB broadside gain, respectively, with suitable cross-polarization levels of better than - 20\;\textdB. These new modes do not appear simultaneously, and can be excited separately by varying the length of the microstrip feed. [ABSTRACT FROM PUBLISHER]