1,721,027 research outputs found
Radiating properties of 1-D bidirectional leaky-wave antennas
No full textWe analyze radiation from bidirectional one-dimensional leaky-wave antennas (1-D LWAs), from an original perspective. As is known, when the aperture is infinite, the radiation pattern changes considerably for certain combinations of the phase and the attenuation constants. These specific values identify the boundaries between different radiating regimes. In this work, we thoroughly explain the evolution of the beam through all the radiating regimes, and then evaluate its beamwidth with original analytical formulas. The relevant case of a finite-size aperture is considered as well. In this case, we show that the boundaries between the radiating regimes change as the radiation efficiency changes. The evolution of these boundaries as a function of the radiation efficiency is found by numerical means. These results allows for a rigorous and comprehensive description of the radiating behavior of practical 1-D bidirectional LWAs
Optimization of the radiating features of 1-D unidirectional leaky-wave antennas
No full textThe optimization of antenna parameters such as gain is an important aspect of all antenna design. In the context of leaky-wave antennas (LWAs), it is important to have accurate design rules for optimizing the gain of the antenna for practical finite-length structures. In this work, taking advantage of the recent formulas derived for the accurate evaluation of the beamwidth in finite-size 1-D unidirectional LWAs, we obtain optimum conditions for this general class of antennas. In particular, design rules for minimizing the beamwidth or maximizing the gain are obtained. The latter is evaluated with a fully analytical procedure through the definition of a correction function that improves the accuracy of the common gain-beamwidth relation. The effects of material losses are also discussed to show how they can affect the optimization procedure. These results apply to any 1-D unidirectional LWA, because no assumptions are made on the wavenumber dispersion, which is instead structure-specific. However, the optimization of two practical examples, namely a holey and a slitted LWA, is discussed to show practical application of the proposed design rules
General formulas for the beam properties of 1-D bidirectional leaky-wave antennas
No full textIn this paper, we analyze the beam properties of bidirectional 1-D leaky-wave antennas (1-D LWAs). Specifically, it is found that, even in the infinite-aperture case, the beam properties considerably change for certain combinations of the phase and the attenuation constants, and different radiation regimes are identified here. New analytic formulas are provided to exactly evaluate the beamwidth of an infinite 1-D bidirectional LWA operating in any radiating regime. However, when the antenna truncation is accounted for, the boundaries between the radiating regimes change as the radiation efficiency changes. Analytic formulas are, therefore, provided to accurately calculate such boundaries for any practical radiation efficiency. The interesting case of a finite-length bidirectional 1-D LWA radiating at broadside is then extensively discussed. With respect to previous beamwidth formulas found in the literature, the new formulas take into account the finiteness of the aperture, thus providing more useful and reliable results, especially in cases when the aperture truncation considerably affects the radiation efficiency. The numerical results corroborate the accuracy of the proposed expressions. These new formulas not only significantly improve the accuracy of the existing ones but also lay the groundwork for the analysis of the beamwidth properties of the important case of 2-D LWAs
Broadside radiation properties of 1D microstrip leaky-wave antennas
No full textIn this paper the behavior in the neighborhood
of broadside for 1D periodic microstrip
leaky-wave antennas is investigated. As is well
known this type of antenna is characterized by a radiated
beam that is frequency scannable from the
backward to the forward quadrant; however the
presence of an open stopband results in undesirable
scan performance near broadside. Here the open
stopband is thoroughly characterized and related to
different types of discontinuities within the unit cell
through a comparison with the results obtained for
a strip grating; moreover, a technique is described
in order to obtain a minimization of the stopband
effects
A general formula for the half-power beamwidth of 1-D unidirectional leaky-wave antennas
No full textA general and accurate formula for evaluating the single-sided beamwidth in one-dimensional unidirectional leaky-wave antennas has been recently proposed. The half-power beamwidth is then estimated by simply doubling the value of the single-sided beamwidth. However, this approximation may lead to inaccurate results as the beam approaches endfire; at that point, the left- and the right-sided beamwidth may considerably differ one another. This conference paper proposes and numerically validates a more general formula to solve this issue
Accurate formulas for the beamwidth of 1-D bidirectional leaky-wave antennas
No full textIn this work, we accurately evaluate the beamwidth of one-dimensional (1-D) bidirectional leaky-wave antennas (LWAs) radiating at broadside. Indeed, existing formulas neglect the effect of the aperture truncation, which affects the exact value of the beamwidth for practical realizations of 1-D LWAs. By exploiting a well-established theoretical framework, we find an approximate, but still accurate analytical formula for evaluating the beamwidth of finite-length 1-D bidirectional LWAs radiating at broadside. The comparison with numerical results confirm the accuracy of the proposed formula, whereas the comparison with previous formulas confirm its relevance for accurate LWA design
A full-wave numerical approach for modal analysis of 1D periodic microstrip structures
No full textIn this paper, a full-wave numerical approach for
the analysis and design of one-dimensional (1-D) printed periodic structures is presented. Electromagnetic-bandgap structures and
leaky-wave antennas are important special cases of structures that
can be analyzed. The proposed technique is based on a mixed-potential integral equation in a unit-cell environment solved by the
method of moments in the spatial domain through a triangular
Delaunay mesh. The 1-D periodic vector and scalar Green’s
functions are derived in the spectral domain and an efficient sum
of spectral integrals is carried out to obtain the spatial-domain
quantities. An appropriate choice of the spectral integration path
is used in order to consider leakage effects. The method developed
here can thus analyze both bound and leaky modes on printed
structures that have an arbitrary metallization within the unit cell
Leaky modes at backward endfire on periodic printed structures
No full textIn this work, the transition at backward endfire between bound (nonleaky) and leaky
modes on one-dimensional periodic structures printed on a grounded dielectric substrate is
examined. This mode evolution has been characterized for a class of structures with a
finite-width cross section. Such structures support leakage into surface waves as well as
into space due to the presence of the substrate. The solutions in this transition region are
calculated using an accurate full-wave moment-method approach that allows for the
determination of both physical and nonphysical solutions, both of which play an important
role in the transition region
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