Build A Phased Array On A Wafer To Boost Antenna Performance

SCALABILITY AND INTEGRATION
As noted, packing more antenna elements on a single wafer enhances the antenna gain and provides a finer beam width, which is essential for high-resolution sensor or radar scanning applications, as well as very-high-data-rate wireless links.

Figure 6 shows a prototype of such an array. The 1024 antenna elements are integrated in a multiple-input, multiple-output (MIMO) configuration beneath each sub-array of the antennas. Due to the spatial power-combining property of waves, the beam-forming function provides enhanced range and coverage, which is needed to improve the SNR of the transmit or receive channel over long distances and for fine resolution.

One of the key limitations in designing a WSAM is dissipating the heat from the wafer. A practical limitation for heat dissipation without a need for an external cooling system is about 1 W/cm² for a silicon substrate. That translates to about 375 W/wafer (for an 8-in. substrate). Obviously, the power dissipation is directly related to the number of antenna elements per wafer. With various packing densities that are the function of the frequency of operation, 64 elements and antennas can be placed at X-band and 4096 elements at V-band.

The key contributors to the integrated solution are the power consumed by the PA (DLNA) and by the controller to address global control of the WSAM. It should be emphasized that a WSAM integrated solution includes building the antenna array and the active electronics on the same substrate.

The key point is that for a 4096-element array (at 60 GHz), the weight of the WSAM module is at least 2000 times less than that of a discrete-component version—a result of extensive reduction of package and substrate material. Notably, the volume of the WSAM module is 4000 times less than the discrete-component-based implementation.

ACKNOWLEDGMENT
The author acknowledges significant support of the WSAM project by various DoD agencies. The development of RF and control-signal distribution across the WSAM has been sponsored by the Defense Advance Research Projects Agency (DARPA). The development of the electronic-scanning capability of the WSAM has been supported by the Air Force Research Laboratory.

References

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