Image Processing Reference
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separation performance. The separation performance is deteriorated especially near the
Nyquist frequency.
Power
(dB)
tap =128
tap =32
tap =8
Frequency ( fs )
Fig. 9. Example of frequency response: the Hilbert transform system
Power (dB)
Power (dB)
reverse
reverse
forward
forward
Frequency ( fs )
(b) the complex FIR system
Frequency ( fs )
(a) the Hilbert transform system
Power (dB)
Power (dB)
reverse
reverse
forward
forward
Frequency ( fs )
(d) the FFT/IFFT system
Frequency ( fs )
(c) the complex IIR system
Power (dB)
Power (dB)
reverse
forward
reverse
forward
Frequency ( fs )
Frequency ( fs )
(e) the modulation/demodulation
(f) the phase-shift system
Fig. 10. Frequency characterization and direction separation performance
3.5 Conclusion
We made the target performances of the direction separating process of digital Doppler
audio, and evaluated six kinds of digital-signal-processing ideas that were pre-existing or
were newly devised. The performances of each processing were evaluated by comparing
many responses such as chirp or step and so on. The results are following.
1.
The complex IIR system and the phase-shift system are filling the target performance of
response time.
2.
The target performance of direction separation is filled except for the phase-shift
system.
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