On Mon, Aug 15, 2011 at 12:48 AM, xi yang <[email protected]> wrote: > Hi, all > > I want to use fpga to do FFT before the data are transmitted to usb. > > In FFT module, I used float point numbers to be its input. According to the > IEEE Floating-Point Standard, a float point number is represented by 32 bits > (bits 0 through 22 form the mantissa, bits 23 through 30 form the exponent, > and bit 31 is the sign bit). However, in GNU Radio, the UHD drive sends > 16bits I, and 16bits Q. > > Are I and Q float point numbers? How do the 16bits represent a float number? > Any suggestion about the I/Q's format is appreciated! > > Thanks, > Yooxi
The interface to the USRP is defined to take floating point numbers. It will perform the conversion to the 16-bit shorts that are sent over the wire for you. Also remember that the output of the FFT is a vector, so you'll want to use the gr_vector_to_stream block to convert it back to a stream of floating point samples. Tom _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
