Radiation Efficiency of Longitudinally Symmetric and Asymmetric Periodic Leaky-Wave Antennas

Otto, S.; Al-Bassam, Amar; Rennings, Andreas; Solbach, Klaus; Caloz, Christophe

doi:10.1109/lawp.2012.2202365

Cited by 60 publications

(22 citation statements)

References 5 publications

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“…where is the maximum stored energy, with the electric energy, , and the magnetic energy, , being equal at the resonance frequency, , and is the radiated power. In the off-broadside regime and under the frequency-balanced condition, the series and shunt powers are then related to their respective quality factors by and (33) where , and , are the series and shunt energies and quality factors, respectively. Note that the energies model the series and shunt reactive near-fields of the LWA and are not related to radiation.…”

Section: Axial Ratio Optimizationmentioning

confidence: 99%

“…According to [31], off-broadside the LWA structure is modeled by purely reactive circuit elements and therefore, the series and shunt energies are always equal, i.e., (34) Substituting (34) into (33), and inserting the result into (29) leads to (35) This result shows that the axial ratio is generally not equal to one and that it varies according to the ratio of the series and shunt quality factors for near-optimum values. Moreover, (35) reveals that, although the off-broadside axial ratio is generally different from one, it is exactly one in the particular case of -balancing [31], which is thus also the condition for minimum axial ratio off-broadside.…”

Section: Axial Ratio Optimizationmentioning

confidence: 99%

“…It has been speculated in [29] that the shunt radiation was cross-polarized, whereas no consideration was given to polarization in [30]. This question was addressed in [33], where it was demonstrated that shunt radiation contribution, whose amount can be controlled by the degree of axial asymmetry, is transversally polarized. At about the same time, a first simplified CRLH LWA design with circular polarization was presented in [34], hence demonstrating an intrinsic quadrature phase relationship between series radiation and shunt radiation for this particular LWA implementation.…”

Section: Introductionmentioning

confidence: 99%

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Circular Polarization of Periodic Leaky-Wave Antennas With Axial Asymmetry: Theoretical Proof and Experimental Demonstration

Otto

Chen

Al-Bassam

et al. 2014

IEEE Trans. Antennas Propagat.

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Abstract-This paper includes two contributions. First, it proves that the series and shunt radiation components, corresponding to longitudinal and transversal electric fields, respectively, are always in phase quadrature in axially asymmetric periodic leaky-wave antennas (LWAs), so that these antennas are inherently elliptically polarized. This fact is theoretically proven and experimentally illustrated by two case-study examples, a composite right/left-handed (CRLH) LWA and a series-fed patch (SFP) LWA. Second, it shows (for the case of the SFP LWA) that the axial ratio is controlled and minimized by the degree of axial asymmetry.Index Terms-Bloch-Floquet theorem, circular polarization (CP), composite right/left-handed (CRLH) transmission line structures, leaky-wave antenna (LWA), periodic structure, phase quadrature, series-fed patch (SFP).

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Section: Axial Ratio Optimizationmentioning

confidence: 99%

Section: Axial Ratio Optimizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Circular Polarization of Periodic Leaky-Wave Antennas With Axial Asymmetry: Theoretical Proof and Experimental Demonstration

Otto

Chen

Al-Bassam

et al. 2014

IEEE Trans. Antennas Propagat.

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“…One possible explanation of this degradation is that an open stopband phenomenon 1 occurs at the broadside frequency, which results in a dramatic drop of gain and radiation efficiency. Many efforts have been made to resolve this issue 21 – 27 . It has been demonstrated that the asymmetry in the LWA structures, either transversal 24 , 25 or longitudinal 26 , 27 , is useful to avoid the performance degradation at the broadside.…”

Section: Introductionmentioning

confidence: 99%

Continuous Beam Steering Through Broadside Using Asymmetrically Modulated Goubau Line Leaky-Wave Antennas

Tang

Zhang

et al. 2017

Sci Rep

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Goubau line is a single-conductor transmission line, featuring easy integration and low-loss transmission properties. Here, we propose a periodic leaky-wave antenna (LWA) based on planar Goubau transmission line on a thin dielectric substrate. The leaky-wave radiations are generated by introducing periodic modulations along the Goubau line. In this way, the surface wave, which is slow-wave mode supported by the Goubau line, achieves an additional momentum and hence enters the fast-wave region for radiations. By employing the periodic modulations, the proposed Goubau line LWAs are able to continuously steer the main beam from backward to forward within the operational frequency range. However, the LWAs usually suffer from a low radiation efficiency at the broadside direction. To overcome this drawback, we explore both transversally and longitudinally asymmetrical modulations to the Goubau line. Theoretical analysis, numerical simulations and experimental results are given in comparison with the symmetrical LWAs. It is demonstrated that the asymmetrical modulations significantly improve the radiation efficiency of LWAs at the broadside. Furthermore, the measurement results agree well with the numerical ones, which experimentally validates the proposed LWA structures. These novel Goubau line LWAs, experimentally demonstrated and validated at microwave frequencies, show also great potential for millimeter-wave and terahertz systems.

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“…It has been shown in [11] that a P-LWA that is symmetric with respect to its two axes, i.e. double symmetric (DS), suffers from the broadside radiation degradation issue, with a radiation efficiency theoretically limited to 50% at broadside [13]. This issue is caused by equal power splitting between the series and shunt resonators, P se = |I se | 2 R = P sh = |V sh | 2 G, where the contribution to broadside radiation from the shunt resonator is null due antisymmetric field cancellation and radiation contribution is therefore only from the series resonator.…”

Section: B Double Symmetric (Ds) Casementioning

confidence: 99%

Broadside Dual-Channel Orthogonal-Polarization Radiation Using a Double-Asymmetric Periodic Leaky-Wave Antenna

Al-Bassam¹,

Otto²,

Heberling³

et al. 2017

IEEE Trans. Antennas Propagat.

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Abstract-The paper demonstrates that double unit-cell asymmetry in periodic leaky-wave antennas (P-LWAs), i.e. asymmetry with respect to both the longitudinal and transversal axes of the structure -or longitudinal asymmetry (LA) and transversal asymmetry (TA) -allows for the simultaneous broadside radiation of two orthogonal modes excited at the two ports of the antenna. This means that the antenna may simultaneously support two orthogonal channels, which represents an interesting polarization diversity characteristics for wireless communications. The double asymmetric (DA) unit cell combines a circularly polarized LA unit cell and a coupled mode TA unit cell, where the former provides equal radiation in the series and shunt modes while the latter separates these two modes in terms of their excitation ports. It is also shown that the degree of TA in the DA unit cell controls the cross-polarization discrimination level. The DA P-LWA concept is illustrated by two examples, a series-fed line-connected patch (SF-LCP) P-LWA and a seriesfed capacitively-coupled patch (SF-CCP) P-LWA, via full-wave simulation and also experiment for the SF-LCP P-LWA case.

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Radiation Efficiency of Longitudinally Symmetric and Asymmetric Periodic Leaky-Wave Antennas

Cited by 60 publications

References 5 publications

Circular Polarization of Periodic Leaky-Wave Antennas With Axial Asymmetry: Theoretical Proof and Experimental Demonstration

Circular Polarization of Periodic Leaky-Wave Antennas With Axial Asymmetry: Theoretical Proof and Experimental Demonstration

Continuous Beam Steering Through Broadside Using Asymmetrically Modulated Goubau Line Leaky-Wave Antennas

Broadside Dual-Channel Orthogonal-Polarization Radiation Using a Double-Asymmetric Periodic Leaky-Wave Antenna

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