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Re: [Discuss-gnuradio] Range of floating point io types
From: |
Josh Blum |
Subject: |
Re: [Discuss-gnuradio] Range of floating point io types |
Date: |
Thu, 01 Sep 2011 08:33:31 -0700 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.20) Gecko/20110805 Lightning/1.0b2 Thunderbird/3.1.12 |
> The doxygen documentation [1] says that the range of COMPLEX_FLOAT32 is
> [-1.0,1.0],
Yes
> which means that both the real and imaginary part must be within this
> range, right?
Correct but, the complex magnitude must not exceed 1.0, or else you may
clip in the DSP.
> And what happens if you try to send values larger than 1.0?
truncation of the most significant bits
For example, the DQPSK block will transmit symbols at +/-1 +/-j. These
constellation points will clip in the DSP of the FPGA if you have the
cordic tuned to a non-zero frequency. I recommend that you characterize
your output before using the max dynamic range of the DAC.
-josh