參數(shù)資料
型號(hào)： AD9864
廠商： Analog Devices, Inc.
英文描述： IF Digitizing Subsystem
中文描述： 中頻數(shù)字化子系統(tǒng)
文件頁(yè)數(shù)： 26/44頁(yè)
文件大?。?/td> 1984K
代理商： AD9864
AD9864
Table 13. SPI Registers Associated with CLK Synthesizer
Address
(Hex)
Breakdown
0x00
(7:0)
0x01
(3:2)
0x10
(5:0)
0x11
(7:0)
0x12
(4:0)
0x13
(7:0)
0x14
(6)
(5)
(4:2)
(1:0)
0x15
(3:0)
0x16
(7:0)
FREQUENCY (MHz)
500
100
400
600
200
R
)
0
550
450
150
50
350
300
350
300
250
0
Bit
Width
8
2
6
8
5
8
1
1
3
1
4
8
Default
Value
0xFF
0
00
0x38
0x00
0x3C
0
0
0
0
0x0
0x04
Name
STBY
CKOB
CKR (13:8)
CKR (7:0)
CKN (12:8)
CKN (7:0)
CKF
CKINV
CKI
CKTM
CKFA (13:8)
CKFA (7:0)
Figure 44. The Shunt Input Resistance vs.
the Frequency of the AD9864’s IF1 Input
FREQUENCY (MHz)
1.5
100
0.5
2.5
200
C
0
2.0
1.0
150
50
0
350
300
250
0
IF LNA/MIXER
The AD9864 contains a single-ended LNA followed by a Gil-
bert-type active mixer, shown in Figure 43 with the required
external components. The LNA uses negative shunt feedback to
set its input impedance at the IFIN pin, thus making it depend-
ent on the input frequency. It can be modeled as approximately
370 ||1.4 pF (±20%) below 100 MHz. Figure 44 and Figure 45
show the equivalent input impedance versus frequency charac-
teristics of the AD9864. The increase in shunt resistance versus
frequency can be attributed to the reduction in bandwidth, thus
the amount of negative feedback of the LNA. Note that the
input signal into IFIN should be ac-coupled via a 10 nF capaci-
tor since the LNA input is self-biasing.
Figure 45. The Shunt Capacitance vs. the Frequency of the AD9864’s IF1 Input
IFIN
R
BIAS
VDDI
MXOP
LO INPUT =
0.3V p-p TO
1.0V p-p
DC SERVO
LOOP
MULTI-TANH
V–I STAGE
CXIF
MXON
CXVM
C
L
L
CXVL
2.7V TO 3.6V
R
GAIN
R
F
0
50
The mixer’s differential LO port is driven by the LO buffer
stage shown in Figure 43, which can be driven single-ended or
differential. Since it is self-biasing, the LO signal level can be
ac-coupled and range from 0.3 V p-p to 1.0 V p-p with negligi-
ble effect on performance. The mixer’s open-collector outputs,
MXOP and MXON, drive an external resonant tank consisting
of a differential LC network tuned to the IF of the band-pass
Σ- ADC, i.e., f
IF2_ADC
= f
CLK
/8. The two inductors provide a dc
bias path for the mixer core via a series resistor of 50 , which
is included to dampen the common-mode response. The
mixer’s output must be ac-coupled to the input of the band-
pass Σ- ADC, IF2P, and IF2N via two 100 pF capacitors to
ensure proper tuning of the LC center frequency.
The external differential LC tank forms the resonant element for
the first resonator of the band-pass Σ- modulator, and so must
be tuned to the
f
CLK
/8
center frequency of the modulator. The
inductors should be chosen such that their impedance at
f
CLK
/8
is
about 140, i.e., L = 180/
f
CLK
. An accuracy of 20% is considered to
be adequate. For example, at
f
CLK
= 18 MHz, L = 10 μH is a good
choice. Once the inductors have been selected, the required tank
capacitance may be calculated using the relation
Figure 43. Simplified Schematic of AD9864’s LNA/Mixer
Rev. 0 | Page 26 of 44
相關(guān)PDF資料
PDF描述
AD9864-EB IF Digitizing Subsystem
AD9864BCPZ IF Digitizing Subsystem
AD9864BCPZRL IF Digitizing Subsystem
AD9866BCPRL Broadband Modem Mixed Signal Front End
AD9866CHIPS Broadband Modem Mixed Signal Front End
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD9864BCP 制造商:Analog Devices 功能描述:IF SUBSYS 48LFCSP EP - Bulk
AD9864BCPZ 功能描述:IC IF SUBSYSTEM GEN-PURP 48LFCSP RoHS:是 類別:RF/IF 和 RFID >> RF 前端 (LNA + PA) 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:250 系列:- RF 型:GPS 頻率:1575.42MHz 特點(diǎn):- 封裝/外殼:48-TQFP 裸露焊盤 供應(yīng)商設(shè)備封裝:48-TQFP 裸露焊盤（7x7） 包裝:托盤
AD9864BCPZ 制造商:Analog Devices 功能描述:IC, IF SUBSYSTEM, 16-24BIT, 6.8KHZ-270KH
AD9864BCPZRL 功能描述:IC IF SUBSYSTEM GEN-PURP 48LFCSP RoHS:是 類別:RF/IF 和 RFID >> RF 前端 (LNA + PA) 系列:- 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:250 系列:- RF 型:GPS 頻率:1575.42MHz 特點(diǎn):- 封裝/外殼:48-TQFP 裸露焊盤 供應(yīng)商設(shè)備封裝:48-TQFP 裸露焊盤（7x7） 包裝:托盤
AD9864-EB 制造商:Analog Devices 功能描述:
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