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參數資料
| 型號： | LTC1957 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | 40MHz to 900MHz Quadrature Demodulator |
| 中文描述： | 高達40MHz至900MHz正交解調器 |
| 文件頁數： | 8/12頁 |
| 文件大?。?/td> | 208K |
| 代理商： | LTC1957 |
LT5517
8
5517f
APPLICATIU
The LT5517 is a direct I/Q demodulator targeting high
linearity receiver applications. It consists of an RF ampli-
fier, I/Q mixers, a quadrature LO carrier generator and bias
circuitry.
The RF signal is applied to the inputs of the RF amplifier,
and is then demodulated into I-channel and Q-channel
baseband signals using precision quadrature LO signals,
which are internally generated using a divide-by-two cir-
cuit. The demodulated I/Q signals are lowpass filtered
internally with a –3dB bandwidth of 130MHz. The differen-
tial outputs of the I-channel and Q-channel are well matched
in amplitude and their phases are 90
°
apart across the full
frequency range from 40MHz to 900MHz.
W
U
U
RF Input Port
Differential drive is recommended for the RF inputs as
shown in Figure 2. A low loss 1:4 transformer is used on
the demonstration board for a wide bandwidth input
impedance match and to assure good noise figure and
maximum demodulator gain. Single-ended to differential
conversion can also be implemented using narrowband
L-C circuits to produce the required balanced waveforms
at the RF
+
and RF
–
inputs using three discrete elements as
shown in Figure 5. Nominal values are listed in Table 1. (In
practice, these values should be compensated according
to the parasitics of the PCB.) The conversion gain and NF
of the receiver are similar to those of the transformer-
coupled demo board, because the single-ended to differ-
ential conversion has a 1:4 impedance transformation,
similar to the transformer.
Table 1. The Component Values of Matching Network L
SH
, C
S1
and C
S2
FREQUENCY (MHz)
L
SH
(nH)
40
437
100
169
200
80.8
300
51.5
400
500
28.3
600
22.6
700
18.5
800
15.6
900
13.5
C
S1
, C
S2
(pF)
71.1
28.6
14.3
9.6
7.2
5.8
4.9
4.2
3.7
3.3
37
The differential impedance of the RF inputs is listed in
Table 2. The RF inputs may also be terminated in a single-
ended configuration. In this case either the RF
+
or the RF
–
input can be simply AC coupled to a 50
source, while the
other RF input is connected to ground with a 1nF capacitor.
Note, however, that this will result in degraded conversion
gain and noise figure in most cases.
Figure 5. RF Input Matching Network at 800MHz
L
15.6nH
TO RF
+
TO RF
–
MATCHING NETWORK
C
3.7pF
RF
INPUT
5517 F05
C
3.7pF
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| LT5500 | 40MHz to 900MHz Quadrature Demodulator |
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| LT5520 | 40MHz to 900MHz Quadrature Demodulator |
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| LTC1957-2EMS | 功能描述:IC RF PWR CONTROLLR DUAL 10-MSOP RoHS:否 類別:RF/IF 和 RFID >> RF 電源控制器 IC 系列:- 標準包裝:3,000 系列:- RF 型:GSM 頻率:450MHz ~ 2GHz 特點:四頻帶 封裝/外殼:8-VFBGA 供應商設備封裝:8-MicroSMD（1.51x1.51） 包裝:帶卷 (TR) 其它名稱:LMV243BLX |
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