hsp50214 Intersil Corporation, hsp50214 Datasheet - Page 15

• Manufacturer Part Number: hsp50214
• Description: Programmable Downconverter
• Manufacturer: Intersil Corporation

Halfband Decimating Filters
The Programmable Down Converter has five halfband filter
stages, as shown in Figure 17. Each stage decimates by 2
and filters out half of the available bandwidth. The first half-
band, or HB1, has 7 taps. The remaining halfbands; HB2,
HB3, HB4, and HB5; have 11, 15, 19, and 23 taps respec-
tively. The coefficients for these halfbands are given in Table
4. Figure 18 shows the frequency response of each of the
halfband filters with respect to normalized frequency, F
Frequency normalization is with respect to the input sam-
pling frequency of each filter section. Each stage is activated
by their respective bit location (15-20) in Control Word 7. Any
combination of halfband filters may be used, or all may be
bypassed. Figure 19 details the halfband alias profiles with
respect to normalized frequency F
Since each halfband filter section decimates by 2, the total
decimation through the halfband filter is given by:
where N = Number of Halfband Filters Selected (1 - 5).
DEC
FIGURE 18. HALFBAND FILTER FREQUENCY RESPONSE
-100
-120
-20
-40
-60
-80
HB
0
=
2
N
-6dB BANDWIDTH
NORMALIZED FREQUENCY (F
0.125
HALFBAND FILTER 5
HALFBAND FILTER 4
HALFBAND FILTER 3
HALFBAND FILTER 2
HALFBAND FILTER 1
0.25
N
.
N
0.375
)
(EQ. 9)
HSP50214
0.5
N
.
15
CONTROL WORD 7, BIT 19
†
FIGURE 17. BLOCK DIAGRAM OF HALFBAND FILTER
Each halfband section decimates by 2
CONTROL WORD 7, BIT 18
F
FIGURE 19. HALFBAND FILTER ALIAS CONSIDERATIONS
-100
-120
N
-20
-40
-60
-80
CONTROL WORD 7, BIT 17
F
= F
0
N
FILTER INPUT
= F
HB4
CONTROL WORD 7, BIT 16
F
HALFBAND
ALIAS
PROFILES
N
CONTROL WORD 7, BIT 15
F
HB3
= F
N
SECTION
= F
HB2
HB1
0.125
F
NORMALIZED FREQUENCY (F
N
= f
HALFBAND FILTER 4
HALFBAND FILTER 3
HALFBAND FILTER 2
HALFBAND FILTER 1
IN
HALFBAND FILTER 5
0
HALFBAND FILTER 5
0
F
0.25
1
5
HALFBAND FILTER 4
= F
0
1
F
HB4
HALFBAND FILTER 3
HB4
0
F
1
HALFBAND FILTER 2
HB3
= F
0
F
OR F
1
HALFBAND FILTER 1
HB2
HALFBAND
FILTER OUTPUT
HB3
= F
-6dB BANDWIDTH
1
F
0.375
HB4
HB1
HB2
= F
OR F
N
)
HB1
/2
= f
OR F
HB3
f
†
IN
S
OR F
OR f
= f
HB2
/2
†
S
†
HB1
S
/2
/2
†
0.5
/2
†