The need for higher bandwidths in applications such as automotive radar and upcoming 6G mobile networks is fueling the demand for higher radio frequencies. This is why the D-Band, spanning from 110 to 170 GHz, garners significant attention.
But tapping into these frequencies poses challenges, such as increased system complexity and signal attenuation. Hollow air-filled substrate-integrated waveguide (AFSIW) technology with fully metalized sidewalls offers significantly reduced signal loss compared to substrate-integrated waveguides (SIWs) that use rows of vias and the planar interconnect technology used in current communication and radar systems. Despite this intrinsic benefit, a mass-production approach for PCBs with integrated AFSIW waveguides is currently unavailable.
“To facilitate the next generation of cost-effective, high-performance radar and communication systems, millimeter-wave front-end systems that can operate at frequencies exceeding 100 GHz are necessary. However, a key concern is how these antennas and millimeter-wave ICs can be optimally connected. We believe a key part of the solution is to utilize AFSIW technology. Unfortunately, such waveguides are expensive and hard to integrate into multi-layer PCBs or interposers. Imec and AT&S have partnered to address this challenge. Together we demonstrate an integrated front-end combining imec’s 140 GHz radar ICs in combination with a novel packaging/module concept developed by AT&S. The demonstration of PCB-integrated AFSIWs is an important breakthrough towards achieving this end goal,” said Ilja Ocket, program manager at imec.
As part of an advanced system module concept, AT&S and imec have collaborated to develop D-Band AFSIWs with solid copper sidewalls integrated into a multi-layer PCB to prevent signal leakage and to form arbitrarily shaped air cavities. It is the first successful demonstration of an AFSIW operating above 100 GHz, and integrated into a low-cost, mass-manufacturable PCB. By eliminating dielectric losses, so that only conductor losses remain, the new approach achieves a loss of 0.07 to 0.08dB/mm across the 115 to 155 GHz frequency range, translating into a five-fold reduction compared to reported planar PCB lines or SIWs in PCBs and interposers. These impressive results only represent a first step, as further improvements will continue to drive down losses even further in the coming years.
“Imec’s 140 GHz radar chips and packaging design expertise have given us a significant head start. We believe that our new packaging approach can be utilized to create efficient, compact, and high-resolution 140 GHz radar modules for automotive applications, creating vehicles that are increasingly ‘aware’ of what is happening, both in-cabin and around them,” said Erich Schlaffer, program manager R&D Electronics Solution at AT&S. “Additionally, this technology will find its way in 6G mobile networks.”
