At 07:03 AM 8/25/2006, Jim Lux wrote:
>Then, the I/Q audio signals run through separate channels, so there's a
>"audio frequency" dependent variation between I and Q. This is fairly
>fixed, independent of
DDS frequency (not audio frequency.. it varies a lot with audio frequency)
>, but is also not particularly well
>represented by a single phase/amplitude calibration value (as currently
>used in PowerSDR), especially when used with wideband audio interfaces
>(e.g. 96 kHz sampling, etc.). The audio interface manufacturers do a
>fairly good job keeping phase and amplitude matched beween channels in the
>middle ranges (say, 100 to 10 kHz), but not so wonderful farther out: their
>primary criteria is making sure it "sounds right" and phase/amplitude
>problems in the lower end of the range would result in "stereo imaging"
>artifacts {Phase difference between L and R being one of the big cues for
>how you tell what direction a sound is coming from}.
Jim
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