Managing power dissipation in 5G antenna design: Page 2 of 5

June 13, 2016 //By Rik Jos, Fellow RF Technology, Ampleon
The emerging 5G wireless communications standard holds the promise of delivering more data to more customers at higher data rates than is currently possible – up to 1000 times more bandwidth by 2025, according to some forecasts. One way this will be achieved is by massive MIMO, using antennas made up of arrays of elements, driven by individual signals.

This works, but is inflexible – it can only handle one data stream and therefore it can only generate one signal beam. If the system needs to handle multiple data streams and generate multiple beams from one array, we need to move to digital beam forming, as shown in Figure 2, in which each element of the antenna array has its own transceiver and set of data converters.


Figure 2: Basic architecture of a digital beam forming array (Source: AMPLEON).

Greater complexity leads to greater power consumption, which needs to be controlled to reduce the environmental impact and operating-cost implications – and the cooling challenge.

 

Estimating the cooling needs of an antenna array

Take a 4x4 antenna array panel operating at 30 GHz, in which the antenna elements are placed half a wavelength apart – that is, 5 mm. To use digital beam forming means each element needs 2 DACs (for I and Q), 2 ADCs, 1 PLL, 1 LNA, 1 PA, 1 transmit/receive switch and some amplifiers and other electronics, including filters. The circuits for each element should ideally be on one chip, for cost and size reasons. The antenna is then assembled by laying out 16 chips evenly across a panel, so that they have short connections to the antenna elements they are driving and the heat they produce can be evenly distributed, as in Figure 3.


Figure 3: A 4x4 antenna array panel, with distributed elements per element and a central processing unit (Source: AMPLEON).

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