What Is Antenna-in-Package?

Antenna-in-package, abbreviated AiP, is a packaging technology that integrates one or more antennas into the same package that houses a radio chip, so that the radiating element and the transceiver ship as a single surface-mount component. It sits between two alternatives: antenna-on-board, where the antenna is etched on the system printed circuit board and connected to the chip through a transmission line, and antenna-on-chip, where the antenna is fabricated on the semiconductor die itself. AiP takes the middle path, keeping the antenna off the lossy silicon substrate while removing the long, lossy board-level interconnect between chip and radiator.

The approach became practical at millimeter-wave frequencies because wavelength shrinks with frequency. At 28 gigahertz a half-wavelength is about 5 millimeters in air and less in dielectric, small enough that a full phased array of patch elements fits inside a package a few centimeters on a side. IBM demonstrated early 60 gigahertz AiP modules in the 2000s, and the technology moved into volume production with 5G millimeter-wave handsets and base stations, a trajectory traced in an invited IEEE paper on recent development of antenna-in-package for 5G millimeter-wave applications.

Interconnect Loss and the Case for Integration

Above roughly 20 gigahertz, connecting a chip to an external antenna is expensive in signal terms. Board dielectrics such as FR-4 become lossy, connector and solder transitions introduce reflections, and every millimeter of trace adds attenuation that directly degrades transmit power and receiver noise figure. Placing the antenna in the package shortens that path to a bump, a short redistribution trace, and a via, which lowers insertion loss, raises effective radiated power for a given amplifier, and reduces the parasitics that would otherwise detune the match. Shorter interconnects also cut the variation between array elements, which matters for beam steering because amplitude and phase errors across the aperture distort the pattern.

Packaging Technologies and Materials

Several substrate technologies compete. Low-temperature co-fired ceramic offers stable dielectric properties and buried cavity structures. Organic laminate build-up substrates, similar to flip-chip package substrates, dominate on cost and are widely used in handset modules. Fan-out wafer-level packaging embeds the die in molding compound and forms the antenna in redistribution layers, giving fine feature control and a very thin profile. Glass substrates, including designs using through-glass vias, offer low loss tangent and dimensional stability, and are an active area of development. Design choices within these technologies include stacked patches to widen bandwidth, cavity-backed structures to suppress surface waves, and dedicated ground and shielding layers to isolate the array from digital switching noise. Thermal management and warpage control constrain the stack-up, since the amplifiers dissipating heat sit directly beneath the radiating layers. A review of antenna-in-package technology in the journal Engineering covers the material and process trade-offs across these families.

Integration, Beam Steering, and Testing

A typical millimeter-wave AiP module carries a patch or dipole array, beamforming integrated circuits with per-element phase shifters and variable gain amplifiers, matching networks, and often the intermediate frequency or baseband interface, all within one package footprint. Handset implementations place two or more modules at different edges of the phone to maintain coverage as the device is rotated or blocked by a hand, and variants that add the board antenna back into the arrangement are compared in an overview of 5G millimeter-wave antenna design solutions for cellular phones. Because there is no connector at which to measure, characterization is over-the-air: far-field or compact antenna test ranges, near-field scanning with transformation to the far field, and equivalent isotropically radiated power measurement replace conductive testing, which changes both laboratory practice and production test economics.

Applications

Antenna-in-package technology has applications in fields including:

• 5G millimeter-wave handsets, customer premises equipment, and small cells
• Automotive radar at 77 gigahertz for collision avoidance and driver assistance
• Short-range gigabit wireless links, including 60 gigahertz WiGig devices
• Satellite communication user terminals with electronically steered arrays
• Radar-based gesture sensing and presence detection modules
• Emerging sub-terahertz research systems for future wireless standards