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| 型号： | AD8347ARUZ-REEL7 |
| 厂商： | ANALOG DEVICES INC |
| 元件分类： | 调制器/解调器 |
| 英文描述： | 800 MHz - 2700 MHz RF/MICROWAVE QUADRAPHASE DEMODULATOR |
| 封装： | MO-153AE, RU-28, TSSOP-28 |
| 文件页数： | 8/28页 |
| 文件大小： | 623K |
| 代理商： | AD8347ARUZ-REEL7 |
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AD8347
Rev. A | Page 16 of 28
THEORY OF OPERATION
RFIN
VREF
RFIP
VPS2
IMXO
COM3
IOPP
IOFS
IOPN
VCMO
VPS1
LOIN
IAIN
COM2
QOPN
COM3
VGIN
ENBL
LOIP
COM1
VPS3
AD8347
PHASE
SPLITTER
1
BIAS
CELL
DET 1
VREF
GAIN
CONTROL
INTERFACE
DET 2
VREF
VCMO
PHASE
SPLITTER
2
VCMO
VDT2
QMXO
QOPP
QOFS
VAGC
VDT1
QAIN
02675-045
4
6
13
8
14
21
12
2
15
10
11
17
20
19
18
22
16
24
25
26
27
23
9
7
1
28
5
3
Figure 45. Block Diagram
The AD8347 is a direct I/Q demodulator usable in digital
wireless communication systems including cellular, PCS, and
digital video receivers. An RF signal in the frequency range of
800 MHz to 2,700 MHz is directly downconverted to the I and
Q components at baseband using a local oscillator (LO) signal
at the same frequency as the RF signal.
differential currents are split and fed to the two Gilbert-cell
mixers through separate cascode stages.
MIXERS
Two double balanced Gilbert-cell mixers, one for each channel,
perform the in-phase (I) and quadrature (Q) down conversion.
Each mixer has four cross-connected transistor pairs that are
terminated in resistive loads and feed the differential baseband
variable gain amplifiers for each channel. The quadrature LO
signals drive the bases of the mixer transistors.
The RF input signal goes through two stages of variable gain
amplifiers before splitting up to reach two Gilbert-cell mixers.
The mixers are driven by a pair of LO signals which are in
quadrature (90 degrees of phase difference). The outputs of the
mixers are applied to baseband I-channel and Q-channel
variable gain amplifiers. The outputs from these baseband
variable gain amplifiers are brought out to pins for external
filtering. The filter outputs are then applied to a pair of on-chip,
fixed gain, baseband amplifiers. These amplifiers gain up the
outputs from the external filters to a level compatible with most
A-to-D converters. A sum of squares detector is available for
use in an automatic gain control (AGC) loop to set the output
level. The RF and baseband amplifiers provide approximately
69.5 dB of gain control range. Additional on-chip circuits allow
the setting of the dc level at the I-channel and Q-channel
baseband outputs, as well as nulling the dc offset at each
channel.
BASEBAND VARIABLE GAIN AMPLIFIERS
The baseband VGAs also use the X-AMP approach with NPN
differential pairs separated by sections of resistive attenuators.
The same interpolator controlling the RF amplifiers controls the
tail currents of the differential pairs. The outputs of these amplifiers
are provided off chip for external filtering. Automatic offset
nulling minimizes the dc offsets at both I- and Q-channels. The
common-mode output voltage is set to the same level as the
reference voltage (1.0 V) generated in the Bias cell, also made
available at the VREF pin (see Figure 45).
OUTPUT AMPLIFIERS
The output amplifiers gain up the signal coming back from each of
the external filters to a level compatible with most high speed A-to-
D converters. These amplifiers are based on an active feedback
design to achieve high gain bandwidth with low distortion.
RF VARIABLE GAIN AMPLIFIERS (VGA)
These amplifiers use the patented X-AMP approach with NPN
differential pairs separated by sections of resistive attenuators.
The gain control is achieved through a gaussian interpolator
where the control voltage sets the tail currents supplied to the
various differential pairs according to the gain desired. In the
first amplifier, the combined output currents from the
transconductance cells go through a cascode stage to resistive
loads with inductive peaking. In the second amplifier, the
LO AND PHASE SPLITTERS
The incoming LO signal is applied to a polyphase phase splitter
to generate the LO signals for the I-channel and Q-channel
mixers. The polyphase phase splitters are RC networks
connected in a cyclical manner to achieve gain balance and
phase quadrature. The wide operating frequency range of these
phase splitters is achieved by cascading multiple sections of
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8347-EVAL | 制造商:Analog Devices 功能描述:EVALUATION BOARD ((NS)) |
| ad8347-evalz | 制造商:Analog Devices 功能描述:EVAL BD 0.8 GHZ TO 2.7 GHZ DIRECT CONVERSION QUADRATURE DEMO - Bulk |
| AD8348 | 制造商:AD 制造商全称:Analog Devices 功能描述:400 MHz to 6 GHz Broadband Quadrature Modulator |
| AD8348ARE | 制造商:Analog Devices 功能描述:QUADRATURE MODULATOR - Rail/Tube |
| AD8348ARU | 功能描述:IC QUADRATUR DEMOD 50MHZ 28TSSOP RoHS:否 类别:RF/IF 和 RFID >> RF 解调器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 功能:解调器 LO 频率:- RF 频率:70MHz ~ 300MHz P1dB:-9dBm 增益:- 噪音数据:6.36dB 电流 - 电源:41.5mA 电源电压:2.7 V 封装/外壳:28-WFQFN 裸露焊盘 供应商设备封装:28-TQFN-EP（5x5） 包装:带卷 (TR) |
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