Planar Asymmetric Fed Interdigital Coupling Antenna-in-Package Using FOWLP Process Operating at 60–90 GHz in Endfire Mode

This article first reports a wideband asymmetric fed interdigital coupling antenna (AFICA) with the fan-out wafer-level package (FOWLP) process. The asymmetric fed structure is designed to realize a more compact array size. The interdigital-shaped coupling method between the elements achieves wideband impedance matching with 70-
$\Omega $
feeding line. In addition, the exemplified
$1\times4$
AFICA array package demonstrates a wide bandwidth from 60 to 90 GHz and an extremely low profile of
$0.044\lambda _{0}$
at 60 GHz. Furthermore, the prototype module is fabricated and integrated with frequency quadrupler CMOS chip. The measured results exhibit a wide bandwidth from 60 to 90 GHz and a peak gain of 9.3 dBi. The measured antenna efficiency is higher than 80%. Both fabricated package and module feature a wide scanning angle of ±50° and low cross-polarization levels (
${\le }\!-\!18$
dB) at operating bands, respectively. The power-based de-embedding method is proposed to evaluate the performance of real-life modules and systems. The simulated and experimental results of the fan-out (FO) interconnection loss are less than 1 dB, respectively. As a result, the proposed co-planar wideband AFICA array with endfire mode design is fully compatible with various chips, such as 5G/6G communication, radar, and sensing applications.