At 05:47 PM 8/22/2008, you wrote:
Chris R. Anderson wrote:
Fundamental requirements for a radio board:
- FPGA
- Power supplies (switchers or linear regulators for multiple voltages)
My preference would be linear regulators, just from a simplicity
standpoint. I'm a fan of Linear Tech--they're not the least
expensive, but they are the best--and have been looking at the
LT1763. It provides 500 mA output, low noise, low dropout voltage,
and various input/output protection circuits. $2.29 each in
quantities of 100, and we'll probably need at least 3 on the board
(3.3V Digital, 3.3V Analog, and 1.8V Digital).
Agree - LTC makes good stuff.
Voltage-wise be aware that the Cyclone III part needs a 1.2V VCCint
and VCCDpll, in addition to the VCCIO which will need to be 1.8V on
the Beagle side and 3.3V on the ADC/DAC side which you've already
noted. There's also the 2.5V VCCA for the FPGA's internal PLL. Be
prepared for VCCint to draw up to several amps too - depends on the
internal speed and utilization.
Drat and blast, you had to remind me of that :-). This is what
happens when you spend all day teaching Engineering to English
majors. I guess that probably means we'll need to use at least one
switching regulator. I've had good luck and experience using the
LT1765. It's good up to 3A and should be useable down to 1.2V.
- ADC/DAC (any decisions on these yet?)
It looks like we're going to go with the AD9860/9862, and design
the board so that either one can be installed.
Those seem nice - lots of goodies inside and they'll help maintain
compatibility with existing USRP applications. Kinda old and
expensive though - using a simpler/cheaper device with just a
converter and doing the signal processing in the FPGA might be more
cost effective.
I know - everyone's a critic. :)
I agree, they're expensive and a few years old, but we can make use
of a lot of existing code. Tell you what, let's get this board to
work, and then see if we can find a better/faster/cheaper way to do
it for REV 2.
Also, I've had some Navy guys express interest in seeing if we could
implement either an AIS (Automatic Identification System) or DSC
(Digital Selective Calling) receiver. Those are both standard
waveforms for large ships, and the Beagleboard would be a very nice
low-cost receiver.
More info on AIS: http://www.navcen.uscg.gov/enav/ais/default.htm
more info on DSC: http://www.navcen.uscg.gov/MARCOMMS/gmdss/dsc.htm
Chris
-------------------------------------
Chris R. Anderson, Ph.D.
[EMAIL PROTECTED]
410-293-6185
Assistant Professor
US Naval Academy
Electrical Engineering Department
105 Maryland Avenue
Annapolis MD 21402
