Super resolving
systems: Toraldo Pupils
(PUTO Project)
Electromagnetic numerical simulation at
20 GHz *
(FEKO fullwave software)
Three coronae Toraldo Pupil 
Near field
Left:. FEKO model for simulating a 3coronae
Toraldo Pupils (TP). The central green cylinder represents the dielectric
layer (with refractive index n = 1.5) employed to implement the
phase inversion. 
Right: FEKO model for a
3coronae TP using the planar multilayer substrate option, which simulate an
infinite opaque
screen. 


Left: Modeled distribution
of the nearfield for the 3coronae TP using an incident (from right) plane
wave. Multiple diffraction rings are
visible. The diameter of the open pupil and the circular screen are 9 cm and
40 cm, respectively. The nearfield
has been computed at
a distance from the screen of 20 cm. The screen thickness is one wavelength
(1.5 cm). 
Right:
Same as to left for an
incident field generated by a rectangular feedhorn
with edge taper. The edge diffraction
effects have disappeared. The logarithmic color scale are from −20
dBV/m (blue) to 0 dBV/m
(red). 

Left: Modeled distribution of the nearfield for the open pupil. 
Right: Modeled distribution of the nearfield for the 3coronae TP. 

Far field
Left:. Plot of the amplitude in the farfield of the 4 coronae TP
(redline), together with the comparison with the amplitude distributions of
the open pupil (blue line) and 3coronae TP (green line). 
Right: FEKO simulation showing the amplitude of the farfield for the 3coronae TP model, using a
rectangular feedhorn source whose field is incident on a circular
finite screen (red curve, with higher sidelobes), and a plane wave with the planar
multilayer substrate option (green curve). 


Left: FEKO simulation
showing the amplitude of the farfield for the 3coronae TP model (green
line), using as a source the equivalent “aperture excitation” fields obtained
at the Cassegrain focus of an antenna whose
aperture diameter was 3.2 m and the same f/D as the Medicina antenna (hence f = 9.72 m). For comparison is
also shown the farfield of the open pupil (blue line). 
Right: Optical system used in the simulation to left. The black bar at
the bottom represents the Cassegrain focus, which
coincides with the focus of the planoconvex lens.
The latter converts the expanding spherical wave into a plane wave that intercepts
a TP and generates the nearfield shown. The lens has a radius of curvature
of 28 cm, a diameter of 25 cm and a thickness along the optical axis of 3 cm.
The separation between the lens and the planar multilayer substrate screen
has been reduced in the figure for the sake of clarity. The real distance used for this simulation
was 150 cm. The gain in angular resolution,
as measured by the ratio of the widths of the central lobe, is of about a 2
factor. 
*For a detailed description of the results see: Luca Olmi et al., “Superresolution with Toraldo
pupils: analysis with electromagnetic numerical simulations”, Proc. SPIE 9906, Groundbased and
Airborne Telescopes VI, 99065Y (July 27, 2016); doi:10.1117/12.2230970