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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: 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],


> 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.


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