Hi Tom,
As you know, there are various ways to implement signal transmission,
depending on your needs for dynamic range requirments, total bandwidth,
whether you can put RFI producting digital circuitry near the feeds,
upgradability, costs, etc.
Can you transmit the RF or IF through analog fibers, and then locate the
digitizers in
an electronics lab, where they are easy to service, upgrade, keep cool,
shield from the receivers, ...? At the ATA we use analog transmission
over fiber.
Each ~15 GHz bandwidth fiber driver/receiver pair cost $2500. All the
digitizers
and digital backends are in the same room, making it easy to upgrade and
service.
The fastest current CASPER digitizers is 6 Gsps (8 bit); we plan to develop
a 20 Gsps digitizer over the next year or so. Their are a some 80 Gsps
digitizers,
but we don't have any plans to use them yet, as we can't handle the data
rate.
Best Wishes,
Dan
Tom Kuiper wrote:
During the upcoming Goldstone 70-m down-time, we have an opportunity
to put fibers dedicated to radio astronomy in the antenna. The
receiver we envision would, when fully built up, have 40 2-GHz ADCs.
To be able to use our signal processing equipment with other antennas
as well, we would want to put it in the Signal Processing Center,
which is about 0.5 km away from the receiver. I assume that we would
have a 10 GBe switch in the antenna. Could someone give me an
estimate of how many fibers of what kind would best serve our needs?
An alternative scheme would be what GAVRT DSS-28 does, which would be
to bring 40 IFs to the SPC and digitize there. That way the ADCs
could serve other antennas. However, this appears to me to be more
expensive and more problem prone, and ADCs are cheap.
Thanks and regards
Tom
