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All Avalon disk recorders now offer the
option of built-in IF-baseband conversion, permitting the full performance benefits of
DSP-based signal processing to be applied directly to the original IF signal.
The IF receiver output is carefully filtered within the recorder
to remove any signals that might 'alias' into the pass-band of interest.
It is then sampled directly by a high performance A/D converter. The samples are processed
and down-converted by the DSP processor to create the digital data
that is recorded to disk. All the intermediate stages of analog or hybrid
D/A and A/D conversion traditionally associated with baseband tape recording are thereby eliminated, creating the most accurate
possible digital recording.
As Figures 1 and 2 demonstrate, this programmable, DSP-based
technique offers outstanding performance. It is possible to achieve a frequency response
of better than +/-0.5 dB across the
specified pass-band and SFDRs of 60 dB or better.
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| Figure 1: Frequency
response of a typical Avalon 160MHz (50 MHz BW) IF channel
(+/- 0.5 dB across the specified pass-band). |
Figure 2: SFDR measurement
from a typical 160 MHz Avalon IF channel (50 MHz BW) recording a pair of
tones at 160 MHz and 166 MHz
(~60 dB) |
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