Ceramic boost for 28GHz mmWave 5G modules

Ceramic boost for 28GHz mmWave 5G modules

Technology News |
By Nick Flaherty

Researchers at materials company Du Pont have developed a Low-Temperature Co-fired Ceramic (LTCC) tape and silver (Ag) metallization for 5G modules operating at 28GHz.

The team at DuPont Microcircuit and Component Materials (MCM) worked with Dr. Chun-An at the Material and Chemical Research Laboratories (MCL) of the Industrial Technology Research Institute (ITRI) in Taiwan on the reference design of an Antenna-in-Package (AiP) that integrates a beam steerable antenna array in a Radio Frequency Front-End module (RFFE).

This used the GreenTape ceramic dielectric which has dielectric properties through 100 GHz while maintaining a dielectric constant (Dk) of 7.1 and dielectric loss (Df) of <0.0010. This was stable throughout the extreme temperature range (-50°C to 150°C) that a deployed radio head may be exposed. Using a full suite of high conductivity Ag metallization pastes for ground planes, via fills, signal lines, and solderable pads, a multilayer module can be made using standard LTCC processing that is co-fired and then can be further processed to surface mount passives, connectors, and active semiconductors.

In small and macro cells deployed outdoors, LTCC has advantages over organic laminate material platforms due to a significantly greater thermal conductivity of the dielectric which helps with thermal management in milliwatt to >1W operation power.

Unlike other materials, it is hermetic, and o is impervious to moisture that can degrade performance. The thermal expansion of LTCC is also a close match to critical ICs that are active components in the modules.

The reference design is intended to encourage hardware designers to consider how LTCC properties and high-frequency performance can enable devices that provide greater access to 5G mmWave bands in real world applications such as small cells installed indoors, connected factories, municipal- or provider-owned small cells for coverage in densely populated areas like smart cities or arenas and performance centre and mmWave base station radio heads.

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An RFFE AiP module was designed to incorporate Anokiwave phasor integrated circuit (IC) chipsets with a 2 x 4 patch antenna array. The module design and prototyping started with the radiating antenna patches, followed by the feedline network and power divider, and, finally, the integration and operation with the phasor IC with all the required passives and connectors.

The fabricated LTCC device shows excellent agreement between the simulations of the design using the material properties measured previously and the measured performance as shown by the return loss of the antenna elements. The module was evaluated by over-the-air measurements at 28 GHz where the Effective Isotropic Radiated Power (EIRP) of greater than 18 dBm was observed while steering the radiated beam by the array and the phasor ICs over ±35°. Less than 1 part per million error vector magnitude (~0.7 ppm EVM) was observed in a 64-quadrature amplitude modulation (64 QAM) scheme.

After building a software system and components to simulate the signal processing functions, 4K resolution video was transmitted reliably over 10 meters.

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