SAFIRE

SAFIRE (St Andrews Fast Imaging Radar Equipment) is a custom built radar that was designed and constructed within the research labs of the
group in St Andews. Under a UK EPSRC partnership for public engagement grant, SAFIRE was one of four main workshops in our touring exhibition designed to showcase the alternative view of the world
provided by MMW remote sensing. The Vision for the future exhibit illustrates the science principles behind the ever increasing technology of millimetre-waves, and allows public enthusiasts of all ages
to participate in an interactive demo of some of the most exciting aspects of the field.

The exhibition was run by the group and was taken around the UK for a period of approximately 18 months beginning in early 2007, and was run by the group members. The project was partnered with a local exhibition
company FifeX Ltd, and more information about the project can be found on the project website: www.vision4thefuture.org.

Instrument

SAFIRE is a 94 GHz frequency modulated continuous wave (FMCW) radar. It uses a multiplied 7 GHz microwave source amplified to give approximately 2mW of output power, and can have a bandwidth of up to 2GHz corresponding to
a range resolution of less than 8cm! It uses a fast scanning flat antenna that rotates 360° and can scan and update imagegery (via pc processing) at approximately 4Hz. Under the design and intended use, SAFIRE can only image
ranges up to 30m given its output power and system noise.

 

SAFIRE_diagram

 

Diagram showing the inner workings of SAFIRE (click image for larger version)

The image above shows the skeleton of SAFIRE. The 94GHz signal is generated at the bottom of the box (gold blocks) with a frequency modulation added via a pc. The amplified signal is split in two: one is kept for reference, and the other is directed up through a large plastic lens, where the beam is focused
onto a flat metallic ellipse-like shape antenna. A DC motor then rotates the antenna continuously, and the radar beam is thrown around the rooom, similar to the projection of a lighthouse. Any objects located around the radar, will cause some return, which is directed in a reverse path
through the radar to a mixer. The mixer compares the return with the reference signal and the signal that was transmitted. The difference signal is then feed to a computer, where it is sampled and converted into a PPI image.

 

 

 

Scan of assembly hall taken at a Montrose Secondary School on one of our exhibits

The image above illustrates the typical PPI (plan position indicator – birds eye view) taken by SAFIRE. The image is of the assembly hall in which one of our visits took place, in Montrose, Scotland. The concentric circles indicate the location of the radar, with the aligned rows
of bright dots almost forming a solid line indicating the location and arrangement of chairs set up for an assembly. The spread of dots to the upper right of the scan depict the arrangement of another exhibit that took place neighbouring our site. The arrangement involved some
school desks and some partion screens.