Contents I. Introduction and Motivation
The demand for higher system bandwidth is almost omnipresent especially in short range applications as communication for broadband data-transfer [1], [2] and in radar-sensing applications for higher target resolution [3]. At a frequency around 300 GHz (sub-THz) the wavelength becomes short enough to efficiently integrate the antenna itself on-chip. A challenging task in this area is the design of broadband on-chip antennas due to the small separation between the antenna and ground layer, which leads typically to a narrow-band matching behavior. To overcome these limitations different design approaches are presented in literature. On the one hand, dielectric resonators can be placed on top of the on-chip antenna [4], on the other hand substrate-integrated-waveguide antennas [5] can be designed to increase the bandwidth of the antenna. Also designs based on localized backside etching techniques can be utilized [6]. Furthermore, defected ground structures in combination with parasitic patches can be applied on-chip, although the silicon thickness has to chosen appropriately for constructive interference [7]. However, this approach leads to unwanted waveguide propagation and radiation phenomena inside the high permittivity silicon wafer, which must be considered.
