BICEP2: Digging further

You will recall that one of the fatal problems with BICEP2 I identified was that its imaging plane antenna elements were far closer together than the ultimate resolution of electromagnetic wave ( ~ one-third the wavelength – a basic physics limitation.) How did this situation come about?

There is now this paper which explains how the spacing was calculated.Here is the relevant portion:

This paper explains that the antenna spacing was determined inside a wafer of quartz above the antenna slots, with a dielectric constant of 11.8. The thickness of the wafer appears to be about one free space wavelength. The slots are much smaller than one wavelength.

By using the grating lobe criterion they find that the minimum spacing at 180 GHz should be 0.46 mm.

But this calculation is wrong. The dielectric constant that needed to be used in the above calculation is that of air (=1.0). Then the spacing would 1.6 mm – which would have avoided the spacing fatality issue I raised.


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One Response to “BICEP2: Digging further”

  1. Camilo Says:

    Hello There!!

    I’m glad you’ve pointed it out. I just wonder what’s the problem with the fundamentals. The only way time-invariant and phase-invariant mathematics work, is by forcing symmetry within the antenna design.

    As you’ve shown earlier, this design would only show complications and of course, time-variant or phase-variant mathematical models should be used (e.g. Chirp Transform etc.) to produce similar results, but that would imply ignoring the antenna design altogether and focus the reconstruction of data with signal processing subsystems.

    I see, like many other people, that the present problem with science, is the incapability of using theoretical models which readdress fundamentals, with the needed completeness and complexity that would help us, for the betterment of understanding physical reality.

    I’m just an Electronics Engineering undergrad trying to make sense of all this mess. I don’t want to be indoctrinated anymore with over-simplified versions of physical reality, and dark energy, and dark matter, and string theory.

    Kind Regards.

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