AD6655BCPZ-125 Analog Devices Inc, AD6655BCPZ-125 Datasheet - Page 40

• Manufacturer Part Number: AD6655BCPZ-125
• Description: IC IF RCVR 14BIT 125MSPS 64LFCSP
• Manufacturer: Analog Devices Inc

Specifications of AD6655BCPZ-125

• Function: IF Diversity Receiver
• Frequency: 450MHz
• Rf Type: Cellular, CDMA2000, GSM EDGE, W-CDMA
• Secondary Attributes: 32-Bit Numerically Controlled Oscillator
• Package / Case: 64-VFQFN, CSP Exposed Pad
• Receiving Current: 705mA
• Frequency Range: 450MHz
• Rf Ic Case Style: LFCSP
• No. Of Pins: 64
• Supply Voltage Range: 1.7V To 1.9V
• Operating Temperature Range: -40°C To +85°C
• Frequency Max: 650MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD6655-125EBZ - BOARD EVAL W/AD6655 & SOFTWARE
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

AD6655
Table 20. FIR Filter Coefficients
Coefficient
Number
C0, C65
C1, C64
C2, C63
C3, C62
C4, C61
C5, C60
C6, C59
C7, C58
C8, C57
C9, C56
C10, C55
C11, C54
C12, C53
C13, C52
C14, C51
C15, C50
C16, C49
C17, C48
C18, C47
C19, C46
C20, C45
C21, C44
C22, C43
C23, C42
C24, C41
C25, C40
C26, C39
C27, C38
C28, C37
C29, C36
C30, C35
C31, C34
C32, C33
SYNCHRONIZATION
The AD6655 half-band filters within a single part or across
multiple parts can be synchronized using the external SYNC
input. Bit 5 and Bit 6 of Register 0x100 allow the half-bands to
be resynchronized on every SYNC signal or only on the first
SYNC signal after the register is written. A valid SYNC causes
the half-band filter to restart at the programmed decimation
phase value.
−0.0012689
−0.0008345
−0.0018439
−0.0024557
−0.0021510
−0.0056810
−0.0013437
−0.0110626
−0.0000229
−0.0195594
−0.0053153
−0.0341468
−0.0192165
−0.0728111
−0.0768890
Normalized
Coefficient
0.0001826
0.0006824
0.0009298
0.0000458
0.0011806
0.0011387
0.0018063
0.0035825
0.0017405
0.0078602
0.0146618
0.0018959
0.0255623
0.0104036
0.0471258
0.0354118
0.1607208
0.4396725
Decimal Coefficient
(21-Bit)
383
1431
1950
96
−2661
−1750
2476
2388
−3867
−5150
3788
7513
−4511
−11914
3650
16484
−2818
−23200
−48
30748
3976
−41019
−11147
53608
21818
−71611
−40300
98830
74264
−152696
−161248
337056
922060
Rev. A | Page 40 of 88
COMBINED FILTER PERFORMANCE
The combined response of the half-band filter and the FIR filter
is shown in Figure 74. The act of bandlimiting the ADC data with
the half-band filter ideally provides a 3 dB improvement in the
SNR at the expense of the sample rate and available bandwidth
of the output data. As a consequence of finite math, additional
quantization noise is added to the system due to truncation in
the NCO and half-band. As a consequence of the digital filter
rejection of out-of-band noise (assuming no quantization in the
filters and with a white noise floor from the ADC), there should
be a 3.16 dB improvement in the ADC SNR. However, the added
quantization lessens improvement to about 2.66 dB.
FINAL NCO
The output of the 32-bit fine tuning NCO is complex and
typically centered in frequency around dc. This complex output
is carried through the stages of the half-band and FIR filters to
provide proper antialiasing filtering. The final NCO provides a
means to move this complex output signal away from dc so that
a real output can be provided from the AD6655. The final NCO,
if enabled, translates the output from dc to a frequency equal to
the ADC sampling frequency divided by 8 (f
the user a decimated output signal centered at f
Optionally, this final NCO can be bypassed, and the dc-centered
I and Q values can be output in an interleaved fashion.
–100
–110
Figure 74. Half-Band Filter and FIR Filter Composite Response
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
0
0.1
FRACTION OF INPUT SAMPLE RATE
0.2
0.3
ADC
ADC
/8). This provides
0.4
/8 in frequency.