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參數資料
| 型號： | AD8345ARE |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 衰減器 |
| 英文描述： | 250 MHz.1000 MHz Quadrature Modulator |
| 中文描述： | 140 MHz - 1000 MHz RF/MICROWAVE QUADRAPHASE MODULATOR |
| 封裝： | MO-153ABT, TSSOP-16 |
| 文件頁數： | 8/16頁 |
| 文件大小： | 372K |
| 代理商： | AD8345ARE |
REV. 0
AD8345
–8–
CIRCUIT DESCRIPTION
Overview
The AD8345 can be divided into the following sections: Local
Oscillator (LO) Interface, Mixer, Differential Voltage-to-Cur-
rent (V-to-I) Converter, Differential-to-Single-Ended (D-to-S)
Converter, and Bias. A block diagram of the part is shown in
Figure 2.
OUT
LOIP
LOIN
IBBP
IBBN
QBBP
QBBN
PHASE
SPLITTER
Figure 2. AD8345 Block Diagram
The LO Interface generates two LO signals at 90 degrees of
phase difference with each other, to drive two mixers in quadra-
ture. Baseband signals are converted into current form in the
Differential V-to-I Converters, feeding into the two mixers. The
outputs of the mixers are combined to feed the Differential-to-
Single-Ended Converter, which provides a 50
output interface.
Bias currents to each section are controlled by the Enable
(ENBL) signal. Detailed description of each section follows.
LO Interface
The LO Interface consists of interleaved stages of polyphase
phase-splitters and buffer amplifiers. The polyphase phase-splitter
contains resistors and capacitors connected in a circular manner
to split the LO signal into I and Q paths in precise quadra-
ture with each other. The signal on each path goes through a
buffer amplifier to make up for the loss and high frequency
roll-off. The two signals then go through another polyphase
network to enhance the quadrature accuracy. The broad oper-
ating frequency range (250 MHz to 1000 MHz) is achieved
by staggering the RC time constants of each stage of the phase-
splitters. The outputs of the second phase-splitter are fed into
the driver amplifiers for the mixers’ LO inputs.
Differential V-to-I Converter
In this circuit, each baseband input pin is connected to an op amp
driving a transistor connected as an emitter follower. A resistor
between the two emitters maintains a varying current propor-
tional to the differential input voltage through the transistor. These
currents are fed to the two mixers in differential form.
Mixers
There are two double-balanced mixers, one for the In-phase
Channel (I-Channel) and one for the Quadrature Channel (Q-
Channel). Each mixer uses the Gilbert-cell design with four
cross-connected transistors. The bases of the transistors are
driven by the LO signal of the corresponding channel. The
output currents from the two mixers are summed together in
two load resistors. The signal developed across the load resistors
is sent to the D-to-S stage.
Differential to Single-Ended Converter
The differential-to-single-ended converter consists of two emit-
ter followers driving a totem-pole output stage whose output
impedance is established by the emitter resistors in the output
transistors. The output of this stage is connected to the output
(VOUT) pin.
Bias
A bandgap reference circuit based on the
-VBE principle gen-
erates the Proportional-To-Absolute-Temperature (PTAT) as
well as temperature-stable currents used by the different sec-
tions as references. When the bandgap reference is disabled by
pulling down the voltage at the ENBL pin, all other sections are
shut off accordingly.
LO LEVEL
–
dBm
N
–
–
150
–
10
–
152
–
160
–
151
–
153
–
154
–
155
V
S
= 5V
–
156
–
157
–
158
–
159
–
9
–
8
–
7
–
6
–
5
–
4
–
3
–
2
–
1
0
1
2
TPC 19. Noise Floor vs. LO Input Power. (T
A
= 25
°
C, F
LO
=
800 MHz, V
S
= 5 V, All I and Q Inputs are DC-Biased to
0.7 V) Noise Measured at 20 MHz Offset from Carrier
LO LEVEL
–
dBm
C
–
–
36
–
10
V
S
= 5.5V
–
40
–
50
–
38
–
42
–
44
–
46
–
48
–
9
–
8
–
7
–
6
–
5
–
4
–
3
–
2
–
1
0
1
2
TPC 20. LO Feedthrough vs. LO Input Power. (T
A
= 25
°
C,
LO = 800 MHz, V
S
= 5.5 V)
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|---|---|
| AD8345ARE-REEL | 制造商:Analog Devices 功能描述:Quadrature Mod 80MHz 16-Pin TSSOP EP T/R |
| AD8345ARE-REEL7 | 功能描述:IC QUADRATURE MOD 250MHZ 16TSSOP RoHS:否 類別:RF/IF 和 RFID >> RF 調制器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 功能:調制器 LO 頻率:700MHz ~ 2.3GHz RF 頻率:700MHz ~ 2.3GHz P1dB:1dBm 底噪:-148dBm/Hz 輸出功率:-1dBm 電流 - 電源:46mA 電源電壓:2.7 V ~ 3.6 V 測試頻率:1.75GHz 封裝/外殼:28-WFQFN 裸露焊盤 包裝:帶卷 (TR) |
| AD8345AREZ | 功能描述:IC QUADRATURE MOD 250MHZ 16TSSOP RoHS:是 類別:RF/IF 和 RFID >> RF 調制器 系列:- 產品培訓模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:2,500 系列:- 功能:調制器 LO 頻率:700MHz ~ 2.3GHz RF 頻率:700MHz ~ 2.3GHz P1dB:1dBm 底噪:-148dBm/Hz 輸出功率:-1dBm 電流 - 電源:46mA 電源電壓:2.7 V ~ 3.6 V 測試頻率:1.75GHz 封裝/外殼:28-WFQFN 裸露焊盤 包裝:帶卷 (TR) |
| AD8345AREZ | 制造商:Analog Devices 功能描述:IC QUAD MODULATOR 140MHZ-1GHZ 16-TSSO 制造商:Analog Devices 功能描述:IC, QUAD MODULATOR, 140MHZ-1GHZ, 16-TSSO |
| AD8345AREZ-REEL | 制造商:Analog Devices 功能描述:Quadrature Mod 80MHz 16-Pin TSSOP EP T/R |
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