Super resolving systems: Toraldo Pupils

(PUTO Project)


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LABORATORY MEASUREMENTS*

 

Amplitude

 

Three-coronae pupil

 

Four-coronae pupil

 

 

 

 

 

 

Plot of the amplitude at 20 GHz in the near field (NF) of the open pupil (solid, black line), and of the three-coronae Toraldo Pupil (dashed, red line). More measurements were performed on just one side of the scan (the negative x direction), in order to test the strength of the far sidelobes. For comparison, the simulated amplitude distribution from FEKO is also shown (dot-dashed, green line). All curves are normalized with respect to the peak value. The distance between the launcher and the screen was 1.9 m, the separation between the screen and the probe was 18 cm, and the sampling interval along the scan direction was 0.5 cm.

 

Plot of the amplitude at 20 GHz in the near field (NF) of the open pupil (solid, black line), and of the four-coronae Toraldo Pupil (dashed, red line). The distance between the launcher and the screen was 1.7 m, the separation between the screen and the probe was 16 cm, and the sampling interval along the scan direction was 0.5 cm. In this case the amplitude generated by the Toraldo Pupil is normalized to the peak value of the open pupil.

 

 

Maps

 

Raster maps were performed with the open pupil and with both three- and four-coronae TPs (Toraldo Pupils).

Both copular and cross-polar radiation patterns were measured. The cross-polar pattern was recorded after rotating the feedhorn by 90.

The cross-polar component of the NF was required in order to later perform the NF-to-FF transformation,

but this measurement also had an interest in the perspective of using the TPs with the receiver system of a radio telescope.

All the cross-polar maps are normalized to the peak amplitude value of the copular pattern

 

 

Open pupil

 

Three-coronae pupil

 

Four-coronae pupil

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Near-field copolar amplitude distribution generated by an open circular pupil. The high-signal spot in the top-left of the map is likely to be an artifact, since it does not show up in other maps.

 

Near field cross-polar component.

 

 

 

Near-field copolar

amplitude distribution

 

 

Near field cross-polar component.

 

 

Near-field copolar

amplitude distribution

 

 

Near field cross-polar

component

 

 

 

 

 

 

 

 

 

 

Parameter values for all maps are:

       Frequency = 20 GHz

       Diameter of the open pupil = 9 cm

       Distance of the launcher from the plane of the pupil = 1.7 m

       Signal detected at a distance from the plane of the pupil = 10 cm

 

 


* For details see: Luca Olmi et al., Laboratory measurements of super-resolving Toraldo pupils for radio astronomical applications, Exp. Astron. (2017) 43: 285. https://doi.org/10.1007/s10686-017-9535-4