Pencil-Beam Single-Point-Fed Dirac Leaky-Wave Antenna on a Transmission-Line Grid

Abstract

Abstract-Leaky-wave antennas (LWAs) are widely used as single-point-fed linear antenna arrays. The extension of LWAs to 2D implies that they can be used as single-point-fed 2D antenna arrays without requiring a complex feeding network. However, generating a pencil beam from 2D LWAs is not straightforward and due care has to be taken for the design of the LWA. On the other hand, transmission-line (TL) grids have demonstrated interesting behaviors, such as an effective negative refractive index and growing of evanescent waves. In this paper, a singlepoint-fed TL-grid 2D Dirac leaky-wave antenna (DLWA) design is proposed that generates a pencil beam at both broadside and slightly tilted angles. The TL-grid unit cell is analytically treated in light of its scattering and impedance matrices. The optimized TL-grid unit cell is shown to exhibit a closed bandgap in the dispersion relation which is also linearly varying with frequency (hence it is a DLWA). The proposed 2D DLWA design is fabricated and the experimental results are presented.

Experimental demonstration of peripherally-excited antenna arrays

“…The perforations ideally should enable radiation along broadside and other tilted directions in a traveling-wave (leaky-wave) manner. However, for such periodic structures, an open bandgap commonly emerges between the relevant 3-4 eigenmodes in the dispersion relation 23,54,55,58 , and results in a frequency range in the dispersion relation that is not covered by any eigenmode solution. Whenever a wave is excited in the frequency range of the open bandgap, it is not allowed to propagate inside the structure, and is entirely reflected back towards the source of excitation.…”

“…Hence, successful radiation at and around broadside is a quite challenging endeavor. To overcome this challenge, the bandgap can be closed by achieving accidental degeneracy between the eigenmodes at the Γ-point in the dispersion relation 23,54,55,58 . This is achieved by manipulating the eigenmodes of the periodic structure, and forcing them to coexist at the Γ-point at exactly the same resonance frequency.…”

“…This is achieved by manipulating the eigenmodes of the periodic structure, and forcing them to coexist at the Γ-point at exactly the same resonance frequency. For a traveling-wave antenna, the eigenmodes are also required to have a balanced radiation strength (similar Q-factors) to guarantee the accidental degeneracy of the eigenmodes, and the complete closure of the bandgap at the Γ-point 23,54,55 . Note that the Q-factor in this case is directly related to the leakage constant (α) of the unit cell, where a lower Q-factor, corresponds to a higher leakage constant, and more radiation from the individual unit cells.…”

Dirac leaky wave antenna for millimetre‐wave applications

“…A 2D transmission-line-based DLWA was presented in [33] with unit cells composed of four transmission lines connected at a single junction forming a cross which can leak radiation out from the open edges of the microstrip line. This 2D DLWA antenna produced pencil beams and was suited for low-frequency applications.…”

Realization of Low Profile Leaky Wave Antennas Using the Bending Technique for Frequency Scanning and Sensor Applications

“…These designs have achieved good antenna performance, but at the expense of increased fabrication costs and design complexity. Furthermore, this is to point out that very limited research has been done on microstrip leaky wave antennas in the Ku-frequency band [15,16,17,18,19,20,21,22,23,24,25,26]. In this work, the sharpness of the bends along the body of a microstrip transmission line is advantageously used to realize a fundamentally different leaky wave antenna with a broadband impedance matching and high gain characteristics in the Ku-band.…”