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| 型號(hào)： | AD8318ACPZ-REEL7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類(lèi)： | 運(yùn)動(dòng)控制電子 |
| 英文描述： | 1 MHz - 8 GHz, 60 dB Logarithmic Detector/Controller |
| 中文描述： | LOG OR ANTILOG AMPLIFIER, 600 MHz BAND WIDTH, QCC16 |
| 封裝： | 4 X 4 MM, MO-220-VGGC, LFCSP-16 |
| 文件頁(yè)數(shù)： | 19/24頁(yè) |
| 文件大小： | 2127K |
| 代理商： | AD8318ACPZ-REEL7 |
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AD8318
Rev. 0 | Page 19 of 24
0
RFIN
VGA/VVA
GAIN
CONTROL
VOLTAGE
DIRECTIONAL
COUPLER
ATTENUATOR
INHI
VSET
INLO
CLPF
VOUT
AD8318
52.3
1nF
C
FLT
1nF
DAC
Figure 39. AD8318 Controller Mode
Decreasing V
SET
, which corresponds to demanding a higher
signal from the VGA, will tend to increase V
OUT
. The gain
control voltage of the VGA must have a positive sense that is
increasing gain control voltage increases gain.
The basic connections for operating the AD8318 as an analog
controller with the AD8367 are shown in Figure 40. The AD8367
is a low frequency to 500 MHz VGA with 45 dB of dynamic
range. This configuration is very similar to the one shown in
Figure 39.
The gain of the AD8367 is controlled by the voltage applied to
the GAIN pin. This voltage, V
GAIN
, is scaled linear-in-dB with a
slope of 20 mV/dB and runs from 50 mV at –2.5 dB of gain, up
to 1.0 V at +42.5 dB.
The incoming RF signal to the AD8367 has a varying amplitude
level; receiving and demodulating it with the lowest possible
error requires that the signal levels be optimized for the highest
signal-to-noise ratio (SNR) feeding into the analog-to-digital
converters (ADC). This can be accomplished by using an
automatic gain control (AGC) loop. In Figure 40 the voltage
output of the AD8318 is used to modify the gain of the AD8367
until the incoming RF signal produces an output voltage that is
equal to the setpoint voltage V
SET
.
0
+3V
INPT
VOUT
VPOS
GND
GAIN
AD8367
VGA
HPLF
RF INPUT SIGNAL
RF OUTPUT SIGNAL
+5V
VSET
CLPF
INHI
VPOS
GND
AD8318
VOUT
INLO
R1
1k
1nF
1nF
0.1
μ
F
C
100pF
100MHz
174
R2
261
R
HP
100
C
100pF
DAC
+V
SET
SETPOINT
57.6
Figure 40. AD8318 Operating in Controller Mode to Provide Automatic Gain
Control Functionality in Combination with the AD8367
This AGC loop is capable of controlling signals over ~45 dB
dynamic range. The output of the AD8367 is designed to
drive loads ≥ 200 . As a result, it is not necessary to use the
53.6 resistor at the input of the AD8318; the nominal
input impedance of 2 k is sufficient. If the AD8367’s
output is to be driving a 50 load, such as an oscilloscope
or spectrum analyzer, a simple resistive divider network can
be used. Note that the divider used in Figure 40 has an
insertion loss of 11.5 dB.
Figure 41 shows the transfer function of output power
versus V
SET
voltage for a 100 MHz sine wave at 40 dBm
into the AD8367.
0
–60
–55
–50
–45
–40
–35
–30
–25
–20
–15
–10
–5
1.2
–1.2
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
1.0
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0
V
SET
(V)
E
P
O
Figure 41. AD8367 Output Power vs. AD8318 Setpoint Voltage
In order for the AGC loop to remain locked, the AD8318
must track the envelope of the VGA’s output signal and
provide the necessary voltage levels to the AD8367’s gain
control input. Figure 42 shows an oscilloscope screenshot of
the AGC loop depicted in Figure 40. A 50 MHz sine wave
with 50% AM modulation is applied to the AD8367. The
output signal from the VGA is a constant envelope sine
wave with an amplitude corresponding to a setpoint voltage
at the AD8318 of 1.0 V.
Figure 42. Oscilloscope Screenshot Showing an AM Modulated Input
Signal to the AD8367. The AD8318 tracks the envelope of this input
signal and applies the appropriate voltage to ensure a constant output
from the AD8367.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8318ACPZ-WP | 制造商:Analog Devices 功能描述:SP Amp LOG Amp Single 5.5V 16-Pin LFCSP EP Tray 制造商:Analog Devices 功能描述:SP AMP LOG AMP SGL 5.5V 16LFCSP - Waffle Pack 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Analog Devices 功能描述:IC AMP LOG SMD 8318 LFCSP-16 |
| AD8318-EP-EVALZ | 功能描述:EVAL BOARD FOR AD8318 制造商:analog devices inc. 系列:- 零件狀態(tài):過(guò)期 類(lèi)型:功率檢測(cè)器 頻率:1MHz ~ 8GHz 配套使用產(chǎn)品/相關(guān)產(chǎn)品:AD8318 所含物品:板 標(biāo)準(zhǔn)包裝:1 |
| AD8318-EVAL | 制造商:Analog Devices 功能描述:EVAL BD FOR AD8318 LOGARITHMIC DETECTOR/CNTRLR - Bulk |
| AD8318-EVALZ | 功能描述:BOARD EVAL FOR AD8318 RoHS:是 類(lèi)別:RF/IF 和 RFID >> RF 評(píng)估和開(kāi)發(fā)套件，板 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類(lèi)型:GPS 接收器 頻率:1575MHz 適用于相關(guān)產(chǎn)品:- 已供物品:模塊 其它名稱(chēng):SER3796 |
| AD8318SCPZ-EP-R2 | 制造商:Analog Devices 功能描述:1 MHZ TO 8 GHZ, 70 DB LOGARITHMIC DETECTOR / CONTROLLER - Tape and Reel |
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