425 Ghz Highly Compact On-Chip Sequential-Phased CP Antenna With 19% Overlapped Impedance-AR Bandwidth

This article presents a 425 Ghz highly compact on-chip sequential-phased circularly polarized (CP) antenna with 19% overlapped impedance-axial-ratio (-AR) bandwidth. Unlike traditional sequential-phase feed relying on the physical length of the delay line to achieve phase progression, this antenna incorporates a compact reactance-loaded sequential-phase feed, which strategically utilizes the equivalent capacitor and inductor to shift the phase. This method eliminates the reliance on the long delay line and realizes stable phase differences over a wide bandwidth. Furthermore, a miniaturized radiating element is presented. By adeptly utilizing the equivalent electric and magnetic walls, this element is tuned to resonate in the unique half TM01 and quarter TE201 modes. The employment of these two incomplete modes expands the antenna impedance bandwidth and reduces the antenna size compared to complete modes. For validation, the presented antenna is fabricated using 65 nm CMOS technology and tested by dedicated terahertz (THz) measurement setups. Measurements show an overlapped impedance-AR bandwidth of 19% and a peak gain of 1.2 dBic. To the best of the author’s knowledge, this is the widest fully integrated THz on-chip CP antenna reported in the literature. The presented antenna offers distinct advantages, including highly compact size, extremely low profile, and wide overlapped impedance and AR bandwidth, making it an appealing candidate in fully integrated THz sensing, imaging, and communication applications.