Image Processing Reference
In-Depth Information
P
ower
Hf(z)
freq
-fs
-fs
/2
0
+
fs
/2
+fs
Power
2・
FB
Hr(z'')
Hf
(
z')
(a) spectrum of LPF
Hf(z)
freq
Hr(z)
Power
-fs
-fs
/2
0
+
fs
/2
+fs
RBC
F
BC
freq
(c) spectra of complex BPF
Hf(z')
and
Hr(z'')
-fs
-fs
/2
0
+
fs
/2
+fs
2・
RB
(b) spectrum of LPF
Hr(z)
Fig. 19. Frequency design of the complex IIR filter system
4.4 Performances
To satisfy the target performances of frequency resolution and frequency characteristics
shown in Table 6, we set up parameters for all the systems, such as the order of the filters
and the FFT number. We use the 8th Butterworth filter with cut-off 0.495*
FB
*
fs
and
0.495*
RB
*
fs
for the LPFs of the modulation/demodulation and complex IIR filter systems.
We perform 128-point FFT and 256-point inverse-FFT involved in the FFT/IFFT system, and
we apply rectangular weight to
WF
and
WR
.
system
estimation
delay (ms)
modulation/demodulation
order
/
fs
(*1)
2 (
order
=8)
FFT/IFFT
0.75*
N
/
fs
(*2)
24 (
N
=128)
complex IIR
order
/
fs
(*1)
2 (
order
=8)
Delay is estimated at
fs
=4 kHz. (*1) not including transient response
(*2) IFFT shift addition pitch is
N
/4.
Table 6. Time-delay of Doppler audio processing
load
(MFLOPS)
System
calculation component
estimation equation
C-add:
order
*8*
fs
C-mul: (
order
*8+6)*
fs
Ovh: 20%
1.96
(
order
=8)
modulation/demodulation
fs
*(48*
order
+24)*1.2
C-add:
N
*
r1
+4*
N
*
r2
C-mul:
N
*
r1
/2+2*
N
*
r2
R-mul: 2
N
*6
Ovh: 20%
5.76
(
N
=128)
(
r1
=7,
r2
=8)
(2
fs
*4/
N
)*
N
*(12+6*
r1
+12*
r2
)*1.2
FFT/IFFT
1.84
(
order
=8)
R-add: real-addition, Rmul: real-multiplication, Ovh: over head, C-add: complex-addition,
C-mul: complex-multiplication, IFFT shift addition pitch is
N
/4.
Calculation volume is estimated at
fs
=4 kHz.
Table 7. Calculation load of Doppler audio processing
C-add:
order
*8*
fs
C-mul:
order
*8*
fs
complex IIR
fs
*(48*
order
)*1.2