Re: [Discuss-gnuradio] Front-end 802.11b

[Akshay Mishra]

Hello,
        The 802.11b should be possible with the USRP being built. (What are
                the FPGA gates/speed ?). The kind of ADC/DAC's being packed on
        it, it seems sufficient for the 802.11. Matt should be able to advise
        on this.

        there is a mention about many other interfaces besides ADC/DAC which
        can be used for AGC control/channel selection etc.

        -akshay.

        PS : we used some mini-circuits "plug & play" RF for our experiments
        here. Lot of fun and easy to use. Any body else having used them ?
        Passive RF front ends with wide dynamic range. suitable for SDR kind
        of work.
        http://www.mini-circuits.com/

On Tue, Feb 03, 2004 at 10:12:44AM -0800, Brian Whitaker wrote:
|Saber,
|
|  Regarding SDR 802.11b, keep in mind that functionally, you¹ll just be
|replacing the baseband/MAC IC in the system. The typcial 11b interface is
|really just a radio tx/rx (like the MAX2820 family), a BB controller (TI or
|some other up-and-coming vendors), and a TCXO, antenna, passives.
|
|  To talk about an SDR implementation, you¹re replacing the existing MAC and
|talking to the radio directly. Talking to the radio, you¹ve got:
|
|  inputs I+, I-, Q+, Q-  (pre-filtered I/Q data ‹ usually
|root-raised-cosine, alpha=0.7 (not exact))
|  outputs I+ I- Q+ Q-
|  SPI interface for channel settings, filter settings, etc
|  logic lines for tx/rx/idle mode control
|  analog AGC lines for tx and rx
|  a few other proprietary controls ‹ maybe an a/g switch for a dual-band
|radio
|
|Using a DAC to generate the BB signal, something like 8-bit @80MHz should do
|OK. I¹m not sure about the receiver, although people have been talking about
|8-10bit at Nyquist (>22MHz).
|
|Vendors that sell 11b radios (like Maxim) often have Eval kits built up that
|allow control via a PC. In the case of the 282x family, you could write code
|to bit-bang on a PC parallel port (emulate SPI and some of the logic
|controls), and then seperately control the ADCs and DACs for the data I/O,
|as well as the two DACs for the AGC (6-8bit, very slow).
|
|Brian.