Three‐dimensional micromachined silicon‐substrate integrated millimetre‐wave helical antennas

Abstract

This study presents a design study of a novel concept of a three‐dimensional (3D) micromachined square helical antenna designed for 75 GHz, which is completely integrated into a semiconductor silicon substrate. In contrast to conventional on‐chip integrated antennas which typically are built on top of the substrate surface, the proposed antenna concept utilises, for the first time to the knowledge of the authors, the whole volume of the wafer by building the helical structure inside the substrate, which results in a very area‐efficient high‐gain radiating element for a substrate‐integrated millimeter‐wave system. The effective permittivity of the antenna core and the surrounding substrate can be tailor‐made by 3D micromachining, for optimising the maximum antenna performance with this design study it was found, that such an antenna concept can achieve a maximum gain of 13.2 dBi, a radiation efficiency of 95.3% at the axial ratio of 0.94 and a half‐power beamwidth (HPBW) of smaller than 40°, and a return loss S11 of −22.3 dB at the nominal frequency of 74.5 GHz, with a 15‐GHz bandwidth with a reflection coefficient better than −10 dB. A 16‐element substrate‐integrated helical line array is demonstrated and achieves a maximum gain of 24.2 dBi with a HPBW of 6.3° in the y–z‐plane. This study also studies intensively the influences of the surrounding silicon substrate and dielectric‐core etching, the matching transition between the helical structure and a coplanar‐waveguide feeding, as well as size and geometry of the ground structure.

Current trends and future perspective of designing on-chip antennas

“…3D micro-machining is another complex but effective technique to characteristics enhancement of OCAs. In [56], to design a complete integrated antenna with high gain of 13.2 dB, 3D micromachining is performed. In this W-band antenna, an air-cored helical structure is designed using multiple level of metal layers connected through vias and integrated into the Si wafer.…”

Planar Helical Antenna of Circular Polarization

“…From a practical point of view, a planar helix is a suitable candidate to be well integrated on the surfaces of the installations, and its cross-section can be either square or rectangular. Square helical antennas have been reported to realize circular polarization with end-fire radiation [11]- [13]. In [13], a square helical antenna was integrated into a semiconductor silicon substrate, achieving good CP performance while maintaining the substrate thickness of 0.…”

“…Square helical antennas have been reported to realize circular polarization with end-fire radiation [11]- [13]. In [13], a square helical antenna was integrated into a semiconductor silicon substrate, achieving good CP performance while maintaining the substrate thickness of 0. 22 at the center frequency.…”

Low-profile and end-fire antennas for airborne applications

“…proposed [119]- [122]. In [120], a square helical antenna was integrated into a semiconductor silicon substrate, achieving good CP performance while maintaining the substrate thickness of 0.22 0 at the center frequency. In [122], a bifilar helix antenna was designed for unmanned aerial vehicle applications.…”