ADC1207S080_2 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 02 — 7 August 2008 16 of 21
NXP Semiconductors
ADC1207S080
Single 12 bits ADC, up to 80 MHz with direct/ultra high IF sampling
12. Application information
12.1 ADC1207S080 in 3G radio receivers
The ADC1207S080 has been proven in many 3G radio receivers with various operating
conditions regarding Input Frequency (IF), signal IF bandwidth and sampling frequency.
The ADC1207S080 is provided with a maximum analog input signal frequency of
400 MHz. It allows a significant cost-down of the RF front-end, from two mixers to only
one, even in multi-carriers architecture.
Table 9 describes some possible applications with the ADC1207S080 in high IF sampling
mode.
[1] IF bandwidth corresponds to the observed area on the ADC output spectrum.
For a dual carrier Wideband-Code-Division-Multiple-Access (W-CDMA) receiver, the most
important parameters are sensitivity and Adjacent Channel Selectivity (ACS). The
sensitivity is defined as the lowest detectable signal level. In W-CDMA, it can be far below
the noise floor. This difference, between the sensitivity and the noise floor, is defined by
the Sensitivity-to-Noise Ratio (SENR). Its value is negative due to the gain processing.
The Adjacent Channel Power Ratio (ACPR) is the difference between the full-scale −3dB
peak and the noise floor. It represents the ratio of the adjacent-channel power and the
average power level of the channel. The ACS is defined by the sum of SENR and ACPR.
Table 9. Examples of possible f
i
, f
clk
, IF BW combinations supported
f
i
(MHz) f
clk
(MHz) IF BW (MHz)
[1]
SNR (dB) SFDR (dBc)
350 80 5.00 65 71
243.95 9.60 0.25 71 80
96 76.80 1.60 72 76
96 76.80 4.80 71 77
96 76.80 20.00 68 76
80 61.44 10.00 70 85
78.4 44.80 3.50 71 76
70 40.00 1.25 72 79
Fig 9. Adjacent channel sensitivity and ADC sensibility
014aaa434
ACPR
NF
interfering channel wanted channel
ACS
noise floor
sensibility
thermal noise
SENR
