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.
- 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. :)
- Frequency source(s)
- Control interfaces for radio (SPI/I2C)
- FPGA Configuration stuff (Flash memory or Beagle interface)
We'll need to sort this out for sure. I'm thinking JTAG (as a backup)
plus Active Serial (EEPROM and/or from the Beagle) would be a good
option. If there's a better choice, though, we need to decide on it soon.
Sounds reasonable.
Eric
