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參數(shù)資料
| 型號： | AD9874 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 通信及網(wǎng)絡(luò) |
| 英文描述： | IF Digitizing Subsystem |
| 中文描述： | SPECIALTY TELECOM CIRCUIT, PQFP48 |
| 封裝： | 1.40 MM HEIGHT, PLASTIC, TQFP-48 |
| 文件頁數(shù)： | 36/40頁 |
| 文件大?。?/td> | 744K |
| 代理商： | AD9874 |
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REV. 0
–36–
AD9874
VCO
LNA
X
MIXER
IF SAW 1
IF SAW 2
DUPLEXER PRESELECT
GAIN = –2dB
NF = 2dB
GAIN = 22dB
NF = 1dB
GAIN = –3dB
NF = 3dB
GAIN = 5dB
NF = 12dB
IF
AMP
GAIN = –9dB
NF = –9dB
GAIN = 15dB
NF = 2dB
13MHz
DSP
OR
ASIC
36dB
PAD
25
24
23
33
PE
PD
PC
SYNCB
31
FS
29
28
DOUTA
CLKOUT
35
19
20
CLKP
CLKN
LOP
LON
43
42
47
15
AD9874
“MASTER”
LOOP
FILTER
15
IOUTC
25
23
24
PE
PD
PC
35
LOP
LON
43
42
IFIN
47
AD9874
“SLAVE”
31
29
28
FS
DOUTA
CLKOUT
33
SYNCB
19
20
CLKP
CLKN
IOUTL
38
LOOP
FILTER
C
VAR
RD
R
F
C
P
C
Z
0.1 F
L
OSC
R
BIAS
C
OSC
VDDC
IFIN
IOUTC
ATTENUATED PATH WITH
“CLIP POINT” = 7.0dBm
DIRECT PATH WITH
“CLIP POINT” = –17dBm
f
REF
f
REF
Figure 29. Example of Split Path Rx Architecture to Increase Receiver Dynamic Range Capabilities
“
Split Path
”
Rx Architecture
A split path Rx architecture may be attractive for those applications
whose instantaneous dynamic range requirements exceed the
capability of a single AD9874 device. To cope with these higher
dynamic range requirements, two AD9874s can be operated in
parallel with their respective clip points offset by a fixed amount.
Adding a fixed amount of attenuation in front of the AD9874,
and/or programming the attenuation setting of its internal VGA,
can adjust the input-referred clip point. To save power and
simplify hardware, the LO and CLK circuits of the device can
also be shared. Connecting the SYNCB pins of the two devices
together and pulsing this line low synchronizes the two devices.
An example of this concept for possible use in a GSM base station
is shown in Figure 29. The signal chain consists of a high linearity
RF front end and IF stage followed by two AD9874s operating in
parallel. The RF front end consists of a duplexer and preselect
filter to pass the GSM RF band of interest. A high performance
LNA isolates the duplexer from the preselect filter while providing
sufficient gain to minimize system NF. An RF mixer is used to
downconvert the entire GSM band to a suitable IF where much
of the channel selectivity is accomplished. The 170.6 MHz IF is
chosen to avoid any self-induced spurs from the AD9874. The IF
stage consists of two SAW filters isolated by a 15 dB gain stage. The
cascaded SAW filter response must provide sufficient blocker rejec-
tion in order for the receiver to meets its sensitivity requirements
under worst-case blocker conditions. A composite response having
27, 60, and 100 dB rejection at frequency offsets of
±
0.8 MHz,
±
1.6
MHz, and
±
6.5 MHz, respectively, provides enough blocker sup-
pression to ensure that the AD9874 with the lower clip point will
not be overdriven by any blocker. This configuration results in the
best possible receiver sensitivity under all blocking conditions.
The output of the last SAW filters drives the two AD9874 via a
direct signal path and an attenuated signal path. The direct
path corresponds to the AD9874 having the lowest clip point
and provides the highest receiver sensitivity with a system noise
figure of 4.7 dB. The VGA of this device is set for maximum
attenuation, so its clip point is approximately –17 dBm. Since
conversion gain from the antenna to the AD9874 is 19 dB, the
digital output of this path will nominally be selected unless the
target signal’s power exceeds –36 dBm at the antenna. The
attenuated path corresponds to the AD9874 having the highest
input-referred clip point and its digital output point of this path
is set to 7 dBm by inserting a 30 dB attenuator and setting the
AD9874’s VGA to the middle of its 12 dB range. This setting
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD9874BST | IF Digitizing Subsystem |
| AD9874EB | IF Digitizing Subsystem |
| AD9875BSTRL | Broadband Modem Mixed-Signal Front End |
| AD9875 | Broadband Modem Mixed-Signal Front End |
| AD9875-EB | Broadband Modem Mixed-Signal Front End |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD9874ABST | 功能描述:IC IF DIGIT SUBSYSTEM 48-LQFP RoHS:否 類別:RF/IF 和 RFID >> RF 其它 IC 和模塊 系列:- 標(biāo)準(zhǔn)包裝:100 系列:* |
| AD9874ABST | 制造商:Analog Devices 功能描述:IF DIGITIZING SYBSYSTEM ((NW)) 制造商:Analog Devices 功能描述:IC, IF DIGITIZING SUBSYSTEM, LQFP-48 |
| AD9874ABST | 制造商:Analog Devices 功能描述:IC IF DIG SUBSYSTEM |
| AD9874ABSTRL | 功能描述:IC IF DIGIT SUBSYSTEM 48-LQFP RoHS:否 類別:RF/IF 和 RFID >> RF 其它 IC 和模塊 系列:- 標(biāo)準(zhǔn)包裝:100 系列:* |
| AD9874ABSTZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:IF Digitizing Subsystem |
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