employ a 2N
參數(shù)資料
型號: AD9271BSVZRL-50
廠商: Analog Devices Inc
文件頁數(shù): 17/60頁
文件大?。?/td> 0K
描述: IC ADC OCT 12BIT 50MSPS 100-TQFP
標(biāo)準(zhǔn)包裝: 1,000
位數(shù): 12
采樣率(每秒): 50M
數(shù)據(jù)接口: 串行,SPI?
轉(zhuǎn)換器數(shù)目: 8
功率耗散(最大): 1.49W
電壓電源: 單電源
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 100-TQFP 裸露焊盤
供應(yīng)商設(shè)備封裝: 100-TQFP-EP(14x14)
包裝: 帶卷 (TR)
輸入數(shù)目和類型: 8 個單端,單極;8 個差分,單極
AD9271
CW DOPPLER OPERATION
Modern ultrasound machines used for medical applications
employ a 2N binary array of receivers for beam forming, with
typical array sizes of 16 or 32 receiver channels phase-shifted
and summed together to extract coherent information. When
used in multiples, the desired signals from each channel can be
summed to yield a larger signal (increased by a factor N, where
N is the number of channels), and the noise is increased by the
square root of the number of channels. This technique enhances
the signal-to-noise performance of the machine. The critical
elements in a beam-former design are the means to align the
incoming signals in the time domain and the means to sum the
individual signals into a composite whole.
Beam forming, as applied to medical ultrasound, is defined as the
phase alignment and summation of signals that are generated
from a common source but received at different times by a
multielement ultrasound transducer. Beam forming has two
functions: it imparts directivity to the transducer, enhancing its
gain, and it defines a focal point within the body from which the
location of the returning echo is derived.
The AD9271 includes the front-end components needed to
implement analog beam forming for CW Doppler operation.
These components allow CW channels with similar phases to be
coherently combined before phase alignment and down mixing,
thus reducing the number of delay lines or adjustable phase shifters/
down mixers (AD8333 or AD8339) required. Next, if delay lines
are used, the phase alignment is performed and then the channels
are coherently summed and down converted by a dynamic range
I/Q demodulator. Alternatively, if phase shifters/down mixers,
such as the AD8333 and AD8339, are used, phase alignment
and downconversion are done before coherently summing all
channels into I/Q signals. In either case, the resultant I and Q
signals are filtered and sampled by two high resolution ADCs,
and the sampled signals are processed to extract the relevant
Doppler information.
AD9271
gm
LNA
Rev. B | Page 24 of
60
gm
SWITCH
ARRAY
LNA
8 × CHANNEL
16-BIT
ADC
Q
I
LNA
AD9271
LNA
SWITCH
ARRAY
8 × CHANNEL
LNA
2.5V
AD8333
2.5V
AD8333
16-BIT
ADC
06
30
4-
0
96
600nH
700
700
700
700
600nH
Figure 47. Typical CW Doppler System Using the AD9271 and AD8333 or AD8339
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