Miniaturization of Omnidirectional Cavity Antennas Using Substrate-Integrated Impedance Surfaces

An omnidirectional antenna with a compact size is presented. The diameter of the proposed antenna is 100 mm and the height is ∼0.1λ L (12 mm). It consists of two dipoles and four shorting pins. With this configuration, the impedance bandwidth of the proposed antenna covers 2.4–2.6 GHz. Within the bandwidth, the proposed antenna has a stable bidirectional radiation pattern in the E‐plane and the omnidirectional radiation pattern in the H‐plane. The geometry of the antenna is investigated and optimised by the ANSYS high‐frequency structure simulator. The fabricated antenna is compact enough to be integrated into a communication system. Measured and simulated results are also obtained and compared at the end of this work.

This paper presents a reconfigurable slot antenna that uses a close-coupled biasing technique to facilitate the reconfiguring between two frequency bands. The technique uses a very thin double layered flexible copper clad Mylar substrate with the slot antenna on the front side and the biasing circuits at the backside of the design. The biasing circuit uses a conventional PIN diode to switch between ON and OFF states. Each state corresponds to a separate operating band. The reconfiguring from one sub-band to another is done electronically by means of a BAR64 diode. In this first example, the two bands are located close to each other to increase the bandwidth of the antenna. The resulting -10dB bandwidth increases by 20% as compared with the OFF-state. The antenna has mostly omnidirectional radiation patterns at the two frequency bands. Simulation and measurement results are compared and discussed which are to be in good agreement with one another.

ABSTRACTIn this article, we present a compact ultrawideband antenna with dual broadband‐notched characteristics centered at 3.4 and 5.5 GHz. The proposed antenna consists of a rectangular patch with a modified ground plane structure and 50 Ω microstrip‐fed line. By etching two opposite U‐shaped slots in the radiating patch, the notched bands of 3.375–3.945 GHz for WiMAX and 5.425–6.150 GHz for WLAN and HYPERLAN/2 were achieved. The antenna also offers a flat frequency response so minimizing the formation of spurs and precursors that ensures optimal time domain performance for ultrawideband radio applications. The return loss was measured to better than −10 dB over the entire band from 3.1 to 10.6 GHz. The antenna gain was larger than 2 dBi all over the frequencies with a flatness of 2.5 dB and an omnidirectional radiation pattern in the H‐plane. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2854–2856, 2015

This research proposes a circularly polarized (CP) single-fed omnidirectional dipole antenna operable in 2.45 GHz frequency for the industrial, scientific, and medical (ISM) radio band applications. The proposed antenna consisted of bisectional dipole core, a pair of quarter-wave baluns, and four diagonally adjoined parasitic braces. The bisectional dipole core was utilized to improve the antenna gain and realize omnidirectional radiation pattern, and the quarter-wave baluns were to symmetrize the current on the bisectional core. The four parasitic braces collectively generated circular polarization. In the study, simulations were conducted using CST Microwave Studio and a prototype antenna fabricated. To validate, experiments were carried out, and simulation and experimental results compared. The finding revealed good agreement between the simulation and experimental results. Essentially, in addition to achieving an antenna gain of 2.07 dBic, the proposed CP single-fed omnidirectional antenna is suited to ISM frequency band applications.

A novel miniature monopole tag antenna for passive Ultra-High Frequency (UHF) radio frequency identification (RFID) operation is presented.The antenna possesses a two-sided structure that is printed on an FR4 substrate and fed by a 50-Ω microstrip line. By properly using helical strips and vias, the antenna size can be reduced to a small volume of 10 (L) × 9.5 (W) × 0.8 (H) mm3 to be easily integrated within various portable devices. A miniaturized quasi-lumped circuit is also designed to attain a good impedance matching between the antenna and the chip. Experimental results demonstrate that the antenna has a suitable operating band about 914–939 MHz and also quite omnidirectional radiation pattern with appreciable gain. Moreover, the proposed compact tag antenna, capable of achieving a maximum readable range of about 5.6 m with an EIRP equal to 4 W, is well suited for RFID applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2770–2772, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25596

A tri-band antenna, which consists of a compact conventional phone antenna and a wideband multiple-input multiple-output (MIMO) antenna, is presented for mobile phone application. Three slits etched into the ground plane are used to reduce the mutual coupling between the conventional phone antenna and the MIMO antenna, moreover, this slits are help to relieve the impedance matching degradation of the conventional phone antenna caused by the mutual coupling. A wideband T-shaped neutralization line without effect on the performance of the conventional phone antenna is applied to improve the isolation for the MIMO antenna, and high isolation is achieved within the wide operation band. For the convention phone antenna, the two operation bands with VSWR ≤ 3 are 0.89–0.96 GHz and 1.71–2.18 GHz, respectively, and nearly omnidirectional radiation patterns in H-plane are achieved. The operation band of the MIMO antenna with VSWR ≤ 1.7 and isolation ≥ 20 dB is 2.4–3.7 GHz, and the two MIMO antenna elements have back-radiation patterns for achieving diversity gain. The simulated and the measured results are in a good agreement.

One of the key element in performance measurement for a neighbor discovery algorithm with switched beam antennas is how long it takes to discover the neighbors given that nodes do not have any prior knowledge about their neighbors. An impression we may have in neighbor discovery is that algorithms based on directional antennas takes longer time for a node to discover all its neighbors than those entirely based on omnidirectional antennas. We propose two neighbor discovery schemes, one is based on time slotting and the other on the well known CSMA/CA unslotted version. We evaluate the time that the sink needs to discover its neighbors when it is equipped with a switched beam antenna, and when it uses an omnidirectional antenna. Through our simulation results, we show that when neighbor discovery algorithms based on directional antennas are correctly designed, they achieve the same order of performance in terms of time needed by the sink to discover all its neighbors as those based on omnidirectional antennas. Our simulation results also show that when using a switched beam antenna and CSMA/CA algorithm for medium access at the sink, the discovery delay is higher.

A horizontally polarized omnidirectional microstrip antenna is proposed in this paper. The structure of designed antenna is with two back-to-back horizontally polarized microstrip antenna elements. Gain variation on main radiation plane of this new antenna is analyzed and radiation theory is deduced; formula of directivity on main radiation plane is given. Better omnidirectional characteristic of this antenna can be obtained by decreasing patch physical length. Both simulated and measured results verify the omnidirectional radiation patterns and input impedance characteristics. Good omnidirectional radiation patterns (gain variation inE-plane less than ±0.4 dBi) and input impedance characteristics are obtained; moreover, cross polarization less than −20 dBi is achieved.

In this work, a compact omnidirectional UHF antenna on the strength of spoof surface plasmon polaritons (SSPPs) is suggested. The measured −10dB impedance bandwidths is about 10.3% which is from 832 to 922 MHz. The simulated total efficiency is greater than 80% over the operating band. Good omnidirectional pattern is observed in the measured results on the H-plane, which is in accordance with the simulated results, and a dipole like pattern is observed on the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$H$</tex> -plane. It also shows that, at the resonance frequency of the antenna of 860 MHz, a compact size of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$112.6\ \text{mm} \times 62\ \text{mm} \times 1 \text{mm}\, (0.323\lambda_{0}\times 0.178\lambda_{0}\times 0.002\lambda_{0})$</tex> was achieved.

During the manufacturing of printed circuit boards (PCBs) for a Flight Project, it was found that a European manufacturer was building its boards to a European standard that had no requirement for copper wrap on the vias. The amount of copper wrap that was measured on coupons from the panel containing the boards of interest was less than the amount specified in IPC-6012 Rev B, Class 3. To help determine the reliability and usability of the boards, three sets of tests and a simulation were run. The test results, along with results of simulation and destructive physical analysis, are presented in this paper. The first experiment involved subjecting coupons from the panels supplied by the European manufacturer to thermal cycling. After 17 000 cycles, the test was stopped with no failures. A second set of accelerated tests involved comparing the thermal fatigue life of test samples made from FR4 and polyimide with varying amounts of copper wrap. Again, the testing did not reveal any failures. The third test involved using interconnect stress test coupons with through-hole vias and blind vias that were subjected to elevated temperatures to accelerate fatigue failures. While there were failures, as expected, the failures were at barrel cracks. In addition to the experiments, this paper also discusses the results of finite-element analysis using simulation software that was used to model plated-through holes under thermal stress using a steady-state analysis, also showing the main failure mode was barrel cracking. The tests show that although copper wrap was sought as a better alternative to butt joints between barrel plating and copper foil layers, manufacturability remains challenging and attempts to meet the requirements often result in features that reduce the reliability of the boards. Experimental and simulation work discussed in this paper indicate that the standard requirements for copper wrap are not contributing to the overall board reliability, although it should be added that a design with a butt joint is going to be a higher risk than a reduced copper wrap design. The study further shows that procurement requirements for wrap plating thickness from Class 3 to Class 2 would pose little risk to reliability (minimum 5 μm/0.197 mil for all via types).Experimental results corroborated by modeling indicate that the stress maxima are internal to the barrels rather than at the wrap location. In fact, the existence of Cu wrap was determined to have no appreciable effect on reliability.

There are some existing narrowband wireless systems over the designated ultra-wideband (UWB) operating band. To mitigate the potential interferences between UWB system and narrowband systems, a UWB antenna with dual band-notched characteristic is proposed. The antenna consists of a circular patch fed by a 50Ω microstrip line. An altered H-shaped slot is etched on the proposed radiator to introduce the dual band-notched function. At the same time, an embedding resonance circuit(ERC) is introduced to increase the depth and width of stop band. Therefore the antenna attains a better band-notched characteristic than other dual band-notched antennas at the same frequency bands. The fabricated antenna has a compact size, 34mm×26mm×1.6mm. The simulated and measured results show that the antenna exhibits a good impedance matching over the bandwidth of 2.8 to 10.7GHz with nearly omnidirectional radiation pattern and a stable gain, except two stop bands at 3.1∼4.2GHz and 5.0∼6.6GHz for filtering the WiMAX and WLAN. The simulated results are in good accordance with the measured ones.

Two compact variants fractal antennas are designed and investigated for portable broadband/ wide-band applications. The designed constrained to two different geometrical structures Modified Koch fractal antenna & Minkowiski fractal antenna (MKFA/MFA). The former design includes a square patch with protruding extensions for wideband applications and the later is a fusion of octagonal patch with reduced square curves on the corresponding vertices's for portable broadband devices. Both antennas are designed on the same pedestal and dimensions with different utility and are well established with the principles of fractal integrity. MFA provides efficient omni-directional radiation patterns with less X-Polarizations and MKFA also results in effective for both Bi & Quasi Omni-directional radiation patterns. Gain and efficiency for both the antennas are on good agreements.

ABSTRACTIn this article, the performance of compact planar wearable antenna 4.1 × 4.1 cm2 mounted on different phantoms and human body fed by microstrip line is designed to operate in ultra‐wide band applications. The proposed antenna consists of a circular patch with notch‐cut and U‐shaped slot on the upper side of the substrate and finite ground plane with rectangular shape defected ground structure (DGS) on the lower side. The U‐shaped slot and finite ground plane are used to achieve an enhanced impedance bandwidth. The proposed antenna is designed and simulated using Ansoft High Frequency Structure Simulator (HFSS) to verify its operation over larger frequency range from 3.6 GHz to 15 GHz. The return loss, VSWR, radiation pattern, and gain are investigated in this article and verified with the experimental measurements. The proposed wearable antenna radiates over a wide frequency band and can achieve nearly omnidirectional radiation patterns with an average gain of 3.11 dBi. A good agreement between simulations and practical measurements can be achieved in order to verify the suitability of proposed wearable antenna to be used in various UWB applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2531–2536, 2016

This paper presents a compact slotted rectangular microstrip antenna with modified ground plane. Performance advancements with simple modifications of a reference antenna has been carried out in the entire work. The radiating patch and the ground surface has been loaded by two asymmetrical slots and two symmetrical slots respectively. This slight change in antenna shape makes the microstrip antenna more compact. In addition, the directivity, gain, and radiation efficiency have been enhanced significantly. The overall antenna size is 41.3 mm × 48.5 mm × 1.6 mm. The proposed antenna provides 19.8% of the compactness along with 2.9dB of gain enhancement, directivity boost of 2.5dB and radiation efficiency improvement of 25%, approximately. An acceptable relationship is observed between co and cross polarization from achieved patterns which imply the antenna structure as a qualified radiator in terms of polarization purity. A prototype is fabricated with proper characterization. The measured results have a good agreement with simulated results.

A compact printed monopole antenna using two U-type slot working at Bluetooth/WiMAX/WLAN service is present. The antenna can be implemented with a small dimension similarly to the conventional strip-type slot. Based on the simulation and measurement results, triple-band antenna using two U-type slots are very effective in rejecting unwanted frequency in terms of its selectivity and small real estate. The overall dimension of the antenna comes around 30 mm×30 mm×1mm. The measurement results show that the antenna offers excellent performance with Bluetooth ranging from 2.28 GHz to 2.9 GHz, WiMAX ranging from 3.3 GHz to 3.85 GHz and wireless local area network (WLAN) ranging from 4.72 GHz to 6.4 GHz. The proposed antenna gives bidirectional pattern in the E-plane and omni-directional radiation pattern in the H-plane over the frequency range and relatively stable. This antenna configuration would be quiet useful for wireless communication systems.