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参数资料
型号： AD8318-EVAL
厂商： Analog Devices, Inc.
英文描述： 1 MHz - 8 GHz, 60 dB Logarithmic Detector/Controller
中文描述： 1兆赫- 8千兆赫，60分贝对数检测器/控制器
文件页数： 11/24页
文件大小： 2127K
代理商： AD8318-EVAL
AD8318
GENERAL DESCRIPTION
The AD8318 is a 9-stage demodulating logarithmic amplifier,
which provides RF measurement and power amplifier control
functions. The design is similar to the AD8313 Logarithmic
Detector/Controller. However, the AD8318 input frequency
range is extended to 8 GHz with 60 dB dynamic range. Other
improvements include: reduced intercept variability versus
temperature, increased dynamic range at higher frequencies, low
noise measurement and controller output (VOUT), adjustable
low-pass corner frequency (CLPF), temperature sensor output
(TEMP), negative transfer function slope for higher accuracy,
and 10 ns response time for RF burst detection capability. A
Rev. 0 | Page 11 of 24
TEMP
SENSOR
GAIN
BIAS
SLOPE
DET
DET
DET
DET
INHI
INLO
I
V
VOUT
I
V
VSET
CLPF
TEMP
VPSI
ENBL
TADJ
VPSO
CMOP
CMIP
0
Figure 21. Block Diagram
A fully differential design, using a proprietary high speed
SiGe process, extends high frequency performance. Input INHI
receives the signal with a low frequency impedance of nominally
1200
in parallel with 0.7 pF. The maximum input with ±1 dB
log-conformance error is typically 0 dBm (re: 50
). The noise
spectral density referred to the input is 1.15 nV/
√
Hz, which
is equivalent to a voltage of 118 μV rms in a 10.5 GHz band-
width, or a noise power of –66 dBm (re: 50
). This noise
spectral density sets the lower limit of the dynamic range.
However, the low-end accuracy of the AD8318 is enhanced
by specially shaping the demodulating transfer characteristic
to partially compensate for errors due to internal noise. The
input system common pin, CMIP, provides a quality low
impedance connection to the printed circuit board (PCB)
ground through the use of four package pins. The package
paddle, which is internally connected to the CMIP pin, should
also be grounded to the PCB to reduce thermal impedance from
the die to the PCB.
The logarithmic function is approximated in a piecewise fashion
by 9 cascaded gain stages. (For a more comprehensive expla-
nation of the logarithm approximation, please refer to the
AD8307 data sheet, available at
www.analog.com
.) The cells have
a nominal voltage gain of 8.7 dB each, and a 3 dB bandwidth of
10.5 GHz. Using precision biasing, the gain is stabilized over
temperature and supply variations. Since the cascaded gain
stages are dc-coupled, the overall dc gain is high. An offset
compensation loop is included to correct for offsets within
the cascaded cells. At the output of each of the gain stages, a
square-law detector cell is used to rectify the signal. The RF
signal voltages are converted to a fluctuating differential
current having an average value that increases with signal
level. Along with the nine gain stages and detector cells, an
additional detector is included at the input of the AD8318,
altogether providing a 60 dB dynamic range. After the
detector currents are summed and filtered, the function
I
D
× log
10
(V
IN
/V
INTERCEPT
) is formed at the summing node,
where I
D
is the internally set detector current, V
IN
is the
input signal voltage, and V
INTERCEPT
is the intercept voltage
(i.e., when V
IN
= V
INTERCEPT
, the output voltage would be 0 V,
if it were capable of going to 0 V).
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相关代理商/技术参数
参数描述
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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
AD8318SCPZ-EP-RL7 制造商:Analog Devices 功能描述:
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AD8318XCPZ 制造商:Analog Devices 功能描述:100MHZ - 8GHZ, 70DB LOGARITHMIC DETECTOR/CONTROLLER - Bulk
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