- 您現在的位置：買賣IC網 > PDF目錄373969 > AD9874 (ANALOG DEVICES INC) IF Digitizing Subsystem PDF資料下載
參數資料
| 型號： | AD9874 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 通信及網絡 |
| 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： | 34/40頁 |
| 文件大小： | 744K |
| 代理商： | AD9874 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁當前第34頁第35頁第36頁第37頁第38頁第39頁第40頁
REV. 0
–34–
AD9874
This second IF signal is then digitized by the - ADC, demodu-
lated into its quadrature I and Q components, filtered via matching
decimation filters, and reformatted to enable a synchronous serial
interface to a DSP. In this example, the AD9874’s LO and CLK
synthesizers are both enabled requiring some additional passive
components (for the synthesizer’s loop filters and CLK oscillator)
and a VCO for the LO synthesizer. Note, not all of the required
decoupling capacitors are shown. Refer to the previous section
and Figure 26 for more information on required external passive
components.
The selection of the first IF frequency is often based on the avail-
ability of low cost standard crystal or SAW filters as well as system
frequency planning considerations. In general, crystal filters are
often used for narrow-band radios having channel bandwidths below
50 kHz with IFs below 120 MHz, while SAW filters are more
suited for channel bandwidths greater than 50 kHz with IFs greater
than 70 MHz. The ultimate stop-band rejection required by the
IF filter will depend on how much suppression is required at the
AD9874’s image band resulting from downconversion to the
second IF. This image band is offset from the first IF by twice the
second IF frequency (i.e.,
±
f
CLK
/4 depending on high or low side
injection).
RF
INPUT
PRESELECT
FILTER
TUNER
ISAW FILTER
VDDA
- ADC
LNA
VCO
ADF42xx
PLL SYN
REFIN
TO
DSP
AD9874
DECIMATION
FILTER
SAMPLE CLOCK
SYNTHESIZER
I
LOOP
FILTER
L
L
VCO
LOOP
FILTER
VDDC
I
C
C
FROM DSP
LO
SYNTH.
VOLTAGE
REFERENCE
SPI
R
V
V
S
P
P
P
CRYSTAL
OSCILLATOR
IFIN
–16dB
LNA
V
V
I
I
DAC AGC
FORMATTING/SSI
DOUTA
DOUTB
FS
CLKOUT
CONTROL LOGIC
G
G
IF2 =
f
CLK
/8
Figure 27 Typical Dual Conversion Superheterodyne Application Using the AD9874
The selectivity and bandwidth of the IF filter will depend on both
the magnitude and frequency offset(s) of the adjacent channel
blocker(s) that could overdrive the AD9874’s input or generate
in-band intermodulation components. Further suppression is
performed within the AD9874 by its inherent band-pass response
and digital decimation filters. Note, some applications will require
additional application-specific filtering performed in the DSP
that follows the AD9874 to remove the adjacent channel and/or
implement a matched filter for optimum signal detection.
The output data rate of the AD9874,
f
OUT
, should be chosen to
be at least twice the bandwidth or symbol rate of the desired signal
to ensure that the decimation filters provide a flat pass-band
response as well as to allow for post-processing by a DSP. Once
f
OUT
is determined, the decimation factor of the digital filters
should be set such that the input clock rate,
f
CLK
, falls between
the AD9874’s rated operating range of 13 MHz–26 MHz and no
significant spurious products related to
f
CLK
fall within the
desired pass band resulting in a reduction in sensitivity perfor-
mance. If a spurious component is found to limit the sensitivity
performance, the decimation factor can often be modified
slightly to find a “spurious free” pass band. In general, selecting
相關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 |
相關代理商/技術參數 |
參數描述 |
|---|---|
| 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:- 標準包裝: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:- 標準包裝:100 系列:* |
| AD9874ABSTZ | 制造商:AD 制造商全稱:Analog Devices 功能描述:IF Digitizing Subsystem |
發布緊急采購，3分鐘左右您將得到回復。