Page 16 - Issue 3 2023

INFRASTRUCTURE

For a non-MIMO operation, only
one transmit channel is used, and when
paired with the four receive channels
the angular resolution is approximately
30° with the antenna arrangement
discussed previously.
In MIMO mode for the context
of this radar, the transmitted signal
is sent through one transmit channel
(Tx1) and the following radar chirp (or
ramp) is sent to the other transmit
channel (Tx2). The separation between
the transmit channels causes an offset
in the angle of arrival at the receive
elements when the transmitted signal
has been sent from Tx2 vs. with Tx1. If
the separation between each element
is known, stored and calibrated then
this offset could be used to create
additional virtual antenna elements.
This means in MIMO mode, the radar
has effectively seven receive elements.
Four are real physical elements, four
are offset virtual elements as they
appear to Tx2, and the centre element
is an overlap of one each of the real
and virtual elements. The angular
resolution is improved to below 20°
when MIMO operation is used in this
example.

Conclusion Figure 4. An EV-TINYRAD24G credit-card sized board, a complete FMCW radar system. The top image
We have introduced and discussed shows the top side showing ADI’s 24 GHz chipset. The lower image shows transmit and receive
some system-level blocks that are used centre-fed patch antennas.
in the building of an FMCW radar. The
frequency of operation was targeted specification of the TinyRad performance and operation can be found in its user’s guide
at 24 GHz due to it being an ISM band. on the product page.
Slow speed FMCW ramps were used While the TinyRad offers good performance for many applications and is likely
to take advantage of the lower speed the best choice for a beginner radar designer, it may be insufficient for some high
sampling signal chain and lower data demanding scenarios such as those with fast-moving targets or at ranges above
rates for ease of real-time data analysis. 200 m (target size dependent). Potential variations to the TinyRad design that could be
The ADI 24 GHz chipset has been shown made to customize the design for a more specific use case have been proposed. The
to offer a good level of integration EV-RADAR-MMIC is a connectorized evaluation board that lacks most of the plug and
and high degree of performance and play functionality of the TinyRad but lends itself well to further customisation as it can
allows the radar design to be simplified interface with an external ADC, processor, and additional external gain stages on the
vs. a completely discrete solution. transmit and receive channels.
The TinyRad platform is a premade
evaluation platform that incorporates About the Author
this chipset and includes the necessary Alex Andrews joined Analog Devices in 2017, graduating from Queen’s University Belfast
software to begin evaluating the radar with a B.Eng. in electrical and electronic engineering.
system immediately, without the lead
time required to develop the required Analog Devices is represented in South Africa by Altron Arrow.
hardware from scratch. A detailed Email ccoetzee@arrow.altech.co.za for more details.

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