-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 The maximum (at 16 bits complex samples) data rate across USB on the USRP is 16 MHz; hence the minimum decimation rate of 4. My understanding is that this decimation gives more bits -- since you're combining 4 samples together, you can now extrapolate between 12-bit ADC samples for a higher resolution. So the min/max data range for complex data from the USRP is -32768/+32767, the full range of the 16-bit short coefficients.
- -Dan Bahn William L Civ USAFA/DFCS wrote: > For complex IQ data values, what is the min/max range both for data coming > from the USRP and data sent to the USRP? > > There are three obvious guesses: > > 1) Normalized to +/-1.0. > 2) Direct match to the ADC/DAC ranges. > 3) Normalized to a nominal ADC/DAC range. > > The first is right out since the values coming back are typically much, much > larger than that. > > The second would result in the RX range (which uses a 12-bit ADC) being > either 0 to 4095 or -2048 to +2047 while the TX range (which uses a 14-bit > DAC) would be either 0 to 16383 or -8192 to +8191. However, while I see both > positive and negative values in the RX data stream, I also see values that > are well above even the unsigned range. > > This leads me to suspect that the data is being normalized to signed 16-bit > values in both directions yielding a range of -32,768 to +32,767 by the > simple expedient of left shifting the ADC output by four places and right > shifting the DAC output by two places (with sign extension, of course). This > seems reasonable as it would make migrating to higher (or lower) resolution > ADCs and DACs transparent, at least until devices with greater than 16-bits > of resolution are used. > > Is that correct, at least where the useful range of values for complex IQ > data is concerned? > > Thanks. > > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFG5PjEy9GYuuMoUJ4RArIrAKCP1fZFwOapnVVXssqgzi2afVWb4wCgrDfS KBP1t/HGT4QXieKTx63B9R8= =uztu -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio