I don't know the details, but it looks like an array of S-band horns. Those won't get smaller without changing the frequency. http://www.q-par.com/products/ho

I don't know the details, but it looks like an array of S-band horns. Those won't get smaller without changing the frequency. http://www.q-par.com/products/horn-antennas/2-18-GHz-wide-band-horn-antennas http://www.q-par.com/products/horn-antennas/2-18-GHz-wide-ba... btw: I would also guess S-band was chosen for a reason. Three are all sorts of atomic vibrational resonances as you scale up in frequency, which might make it harder to get the desired view.