On 2/1/12 12:22 PM, Attila Kinali wrote:
On Wed, 1 Feb 2012 11:49:51 -0800
Peter Monta<pmo...@gmail.com> wrote:
One possible inexpensive design:
- RF input passively split three ways, with LC filters for the three
channels: L5/E5, L2, and L1/E1/Glonass
- For each channel, a downconverter (Maxim MAX2121) feeding a ~65 Ms/s
ADC (e.g. MAX19505)
- A low-cost FPGA (e.g. Spartan-6) that quantizes the channels to 2
bits, does AGC, assembles Ethernet packets
- Ethernet PHY, power (PoE?), etc.
You don't need the ADC: you just need a limiter/comparator. But you do
need a bunch of RF gain. I think you can get suitable ceramic filters
off the shelf for the GPS frequencies that are inexpensive.
You don't need insane sampling rates. Think in terms of subharmonic
sampling.
Heh..That's pretty much the design i thought of, though using a higher
sampling frequency (100 to 200Msps) which would allow to coherently
decode the E5a and E5b signals together. There is an ADC from National
that can do 200Msps for 20 bucks, with FPGA friendly parallel output
(ADC08200).
Is there a publically-available antenna design that's easy to
fabricate, has a stable phase center, covers 1100--1600 MHz, and has a
good pattern over this band with low cross-polarization? Even a large
choke-ring design would be okay if it's fully specified.
I think there are some crossed dipole designs around. What about quad
helix?
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