In this paper a compact annular ring micro strip patch antenna with modified ground plane is proposed for UWB applications. The dimensions of proposed antenna are 30 × 26 × 1.6 mm3 which was designed ...on FR4 substrate with the thickness of 1.6 mm, εr = 4.4 and loss tangent parameter 0.02. To enhance the impedance bandwidth of the antenna ground plane is modifiedby extruding an inverted L shape stub and defected with multiple I shaped slots. The radiator consists of annular ringpatch, two circular stubs and one rectangular stub is included to the patch to improve the bandwidth. To design and simulate the proposed antenna CST Studio Suite 2018 is used. The proposed antenna is found with UWB frequency range of 3.1–10 GHz (S11 < −13 dB). Multiple frequency bands are observed in UWB frequency range 3.18 GHz, 6.75 GHz and8.67 GHz with the reflection coefficients of −49.6 dB, −50.2 dB and −45.7 dB respectively. VSWR is less than 2 for the total UWB frequency range. Proposed antenna is better option for UWB applications specially First and third frequency bands (3.18 GHz and 8.67 GHz) are suitable for Radio location (G59) services and second frequency band (6.75 GHz) is suitable for satellite and TV broadcasting applications. Performance of the proposed antenna is evaluated in terms of size, radiation efficiency and radiation patterns and it is better compared with existed systems.
The wireless power transfer (WPT) efficiency to implanted bioelectronic devices is constrained by several frequency-dependent physical mechanisms. Recent works have developed several mathematical ...formulations to understand these mechanisms and predict the optimal operating conditions. However, the existing approaches rely on simplified body models, which are unable to capture important aspects of WPT. Therefore, this article proposes the efficiency analysis approach in anatomical models that can provide insightful information on achieving the optimum operation conditions. First, this approach is validated with a theoretical spherical wave expansion (SWE) analysis, and the results for a simplified spherical model and a human pectoral model are compared. The results show that although a magnetic receiver outperforms an electric one for near-field operation and both the sources could be equally use in the far-field range, it is in the mid-field that the maximum efficiency is achieved with an optimum frequency between 1 and 5 GHz depending on the implantation depth. The receiver orientation is another factor that affects the efficiency, with a maximum difference between the best and worst case scenarios around five times for the electric source and over 13 times for the magnetic one. This approach is used to analyze the case of a deep-implanted pacemaker wirelessly powered by an on-body transmitter and subjected to stochastic misalignments. We evaluate the efficiency and exposure, and we demonstrate how a buffered transmitter can be tailored to achieve maximum powering efficiency. Finally, design guidelines that lead to optimal implantable WPT systems are established from the results obtained with the proposed approach.
From the characteristic mode point of view of electrically small antennas, radiation efficiency normally decreases significantly if multiple modes are well excited. Among all these well-excited ...modes, the one with the lowest modal radiation efficiency determines how much actual radiation efficiency is guaranteed. Based on this idea, this letter proposes a method for improving antenna efficiency using shape optimization approach. The optimized shape can give rise to a high efficiency and an implied high gain after being excited using a single port whose location is easily selected by observing characteristic-mode current distributions.
This work describes the designof an SRR-loaded pentagon monopole antenna for super wideband (SWB) applications on Rogers RT/Duroid 5880 dielectric material with dielectric constant of 2.2, and a ...dielectric loss tangent of 0.0009. The pentagon patch radiator is fed with a 50 Ω transmission line placed on the dielectric size of 16 mm × 14 mm × 0.787 mm. In this paper, SRR is etched from the radiating element, and partial ground is added to improve the performance characteristics. The proposed antenna has a bandwidth ratio (BR) of 185.38 and an impedance bandwidth (IBW) of 66.38 GHz at a reflection coefficient of −10 dB. It has a fractional bandwidth (FBW) of 197.85% and a bandwidth dimension ratio (BDR) of 19,786 dB, with a peak gain of 6.2 dB. The proposed antenna covers microwave applications, which cover the following spectrums: L: 1–2 GHz, S: 2–4 GHz, C: 4–8 GHz, X: 8–12 GHz, Ku: 12–18 GHz, K: 18–26.5 GHz, Ka: 26.5–40 GHz, and limited millimetre wave frequencies up to 70 GHz.
Male crickets attract females by producing calls with their forewings. Louder calls travel further and are more effective at attracting mates. However, crickets are much smaller than the wavelength ...of their call, and this limits their power output. A small group called tree crickets make acoustic tools called baffles which reduce acoustic short-circuiting, a source of dipole inefficiency. Here, we ask why baffling is uncommon among crickets. We hypothesize that baffling may be rare because like other tools they offer insufficient advantage for most species. To test this, we modelled the calling efficiencies of crickets within the full space of possible natural wing sizes and call frequencies, in multiple acoustic environments. We then generated efficiency landscapes, within which we plotted 112 cricket species across 7 phylogenetic clades. We found that all sampled crickets, in all conditions, could gain efficiency from tool use. Surprisingly, we also found that calling from the ground significantly increased efficiency, with or without a baffle, by as much as an order of magnitude. We found that the ground provides some reduction of acoustic short-circuiting but also halves the air volume within which sound is radiated. It simultaneously reflects sound upwards, allowing recapture of a significant amount of acoustic energy through constructive interference. Thus, using the ground as a reflective baffle is an effective strategy for increasing calling efficiency. Indeed, theory suggests that this increase in efficiency is accessible not just to crickets but to all acoustically communicating animals whether they are dipole or monopole sound sources.
The present commentary aims to explicate the veracity of the assertions posited by Capek and Jelinek in their article titled "Transducer and Radiation Efficiency Figures of a Multiport Antenna ...Array." According to the authors, it is not feasible to employ the Total Active Reflection Coefficient (TARC) to determine the transducer and radiation efficiency figures they propose, in most instances. Our findings indicate that TARC has already integrated the suggested figures, thereby obviating the need for further computation. The findings of our mathematical inquiry indicate that the assertion made by the authors is erroneous. We demonstrate the matching technique for a highly coupled asymmetric three-element dipole antenna array and show that the TARC for the worst case scenario is smaller than both conjugate and 50Ω matchings.
Fundamental bounds on antenna gain are found via convex optimization of the current density in a prescribed region. Various constraints are considered, including self-resonance and only partial ...control of the current distribution. Derived formulas are valid for arbitrarily shaped radiators of a given conductivity. All the optimization tasks are reduced to eigenvalue problems, which are solved efficiently. The second part of this paper deals with superdirectivity and its associated minimal costs in efficiency and Q-factor. This paper is accompanied by a series of examples practically demonstrating the relevance of the theoretical framework and entirely spanning a wide range of material parameters and electrical sizes used in antenna technology. The presented results are analyzed from a perspective of effectively radiating modes. In contrast to a common approach utilizing spherical modes, the radiating modes of a given body are directly evaluated and analyzed here. All crucial mathematical steps are reviewed in the appendices, including a series of important subroutines to be considered making it possible to reduce the computational burden associated with the evaluation of electrically large structures and structures of high conductivity.
A polarization-agility antenna using liquid metal (eutectic gallium indium) with high radiation efficiency is proposed in this letter. This design approach offers possibilities to use the minimum ...amount of liquid metal as well as elastomer, so that a higher-radiation-efficiency liquid metal antenna can be realized. The proposed design is based on an aperture-coupled patch antenna composed of both liquid metal alloy and copper tape. The polarization of this antenna is controlled by the position of the pressure-driven liquid metal encased in four triangle cavities constructed by both the elastic dielectric material (i.e., Ecoflex) and polyethylene terephthalate film. A prototype is demonstrated with a center frequency of 2.45 GHz. Three kinds of polarization including left-hand circular polarization, right-hand circular polarization, and linear polarization are successfully demonstrated. A radiation efficiency higher than 90% is observed in the measurement.
In this paper, we propose and develop a leaky-wave antenna (LWA) by periodically loading shunt radiation element pairs along a host transmission line (TL). Each pair of radiation unit consists of one ...capacitive element and one inductive element, which are susceptance-complementary with each other. The complementary radiation element loading leads to an effective open-stopband (OSB) suppression, thereby facilitating a continuous leaky-wave beam scanning from backward, through broadside, to forward. Compared with the previously studied OSB-suppressed LWAs containing only one type of susceptive radiation elements, the proposed LWA features two unique properties: constant radiation efficiency over the operation band, and unit cell period only related to the host TL regardless of parameter values of the radiation elements. The aperture synthesis of the proposed LWA is hence straightforward as the radiation elements can be designed to be equally spaced. Experimental prototypes are designed and fabricated based on microstrip line structure as a proof of concept. Desired measured results agree well with the theoretical predictions.
•A micro-scale burner with baffle for ammonia combustion is proposed.•The effects of the baffle on combustion and thermal performance are investigated.•The influence of baffle on the chemical ...reaction kinetics of NO formation is revealed.
Ammonia has attracted extensive attention, and its popularization and application in various power equipment has become one of the current hotspots. However, in the combustion-based micro power system, the combustion and emission characteristics of ammonia at micro scale are still unclear. In this paper, the combustion and emission characteristics of ammonia/oxygen in micro burner with baffle were studied by numerical simulation. By changing the length, width, position of the baffle and inlet velocity, the effects of various factors on temperature field, NO emission and radiation efficiency were obtained. The results show that compared with micro conventional burner, the addition of baffle reduces the channel temperature, radiation efficiency and NO emission. As the baffle length increases, the channel maximum temperature and NO emission decrease first and then increase. The mass fraction of NO in the exhaust gas increases as the baffle width increases under constant flow rate. As the baffle moves downstream, NO emission presents a parabolic distribution. When the baffle with length of 5 mm and width of 0.5 mm is placed 3 mm away from the inlet, the radiation and emission performance are the best. The mass fraction of NO decreases by 24.71% compared with micro planar combustor.
Fig. 1. Mass fraction of NO and radiation efficiency of burners Display omitted .
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