Codesigned Planar-Packaged THz Transmitter With Integrated CMOS Chip and Folded Reflectarray

This article introduces a planar-packaged terahertz (THz) transmitter, codesigned with a highly integrated CMOS active chip and a folded reflectarray (FRA). This design addresses the essential demands for high-power and cost-effective packaging solutions in THz applications. The CMOS active chip incorporates a four-stage ring oscillator and a differential on-chip patch antenna, both integrated into a single chip. A four-stage ring oscillator with a gate-loaded varactor configuration is proposed to broaden the frequency tuning range. The integration of the four-stage ring oscillator functionally multiplexing an on-chip antenna enables direct harmonic radiation without an impedance matching network, facilitating a compact, symmetrical chip layout. Furthermore, the chip-integrated FRA codesigned with the CMOS feeding source significantly narrows the beamwidth and enhances the equivalent isotropic radiated power (EIRP) without introducing additional power consumption. The fabricated prototype exhibits an EIRP of 12.3 dBm at 335 GHz, representing a significant EIRP enhancement of up to 22 dB over a standalone CMOS feeding source while maintaining a minimal dc power consumption of 49.6 mW. Additionally, the THz transmitter exhibits a frequency tuning range from 315 to 337.5 GHz, offering a relative bandwidth of 7.1%, and a dc-to-EIRP efficiency of 34.2%. The proposed chip-integrated FRA, with its low cost, low profile, and planar active integration capability, provides a substantial advancement for THz applications.