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advantage of the slight time
difference inherent in the signals
traveling along different spatial
paths to differentiate the signals.
Beamforming, beamsteering, and
MIMO can all be accomplished
using analog methods. However,
a fully analog system may not be
desirable for high antenna element
systems due to the resulting
size, weight, power, cost, and
interconnect complexity compared
to a hybrid analog-digital or
fully digital system (Figure 4).
As shown, with a fully analog
phased array, the beamforming
is performed using analog phase
shifters and attenuators for each
element. If the received signals
are digitized, the beamforming
can be done in the digital domain,
eliminating the need for RF
phase shifters and attenuators
at each element. This concept
could be taken further, with the
transmitter phase shifters and
attenuators replaced by a digital
beamformer. With appropriate DSP
hardware, such a system could
be used for MIMO with additional
DSP techniques to perform
spatial multiplexing processing.
Figure 4: A corporate multi-beam analog phased array feed architecture (top) and a corporate multi-beam elemental digital
beamforming phased array feed architecture (bottom). (Source: NASA)
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