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Application Notes
(Continued)
All gain cell outputs are AM-demodulated with a peak detec-
tor and summed together. This results in a logarithmic func-
tion. The logarithmic range is about:
20 · n · log (A)
where,
n = number of gain cells
A = gain per gaincell
Figure 9
shows a logarithmic function on a linear scale and
the piecewise approximation of the logarithmic function.
Figure 10
shows a logarithmic function on a logarithmic
scale and the piecewise approximation of the logarithmic
function.
The maximum error for this approximation occurs at the
geometric mean of a gain section, which is e.g. for the third
segment:
(9)
The size of the error increases with distance between the
thresholds.
LAYOUT CONSIDERATIONS
For a proper functioning part a good board layout is neces-
sary. Special care should be taken for the series resistance
R
(
Figure 1
) that determines the attenuation. For high re-
sistor values the parasitic capacitance of the resistor may
significantly impact the realized attenuation. The effective
attenuation will be lower than intended. To reduce the para-
sitic capacitance across resistor R
1
, this resistor can be
composed of several components in series instead of using
a single component.
20076020
FIGURE 8. Gain Cell
20076021
FIGURE 9. Log-Function on Lin Scale
20076022
FIGURE 10. Log-Function on Log Scale
L
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相關(guān)代理商/技術(shù)參數(shù) |
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|---|---|
| LMV228SD/NOPB | 功能描述:射頻檢測器 RoHS:否 制造商:Skyworks Solutions, Inc. 配置: 頻率范圍:650 MHz to 3 GHz 最大二極管電容: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SC-88 封裝:Reel |
| LMV228SDEVAL | 功能描述:BOARD EVALUATION FOR LMV228SD RoHS:否 類別:RF/IF 和 RFID >> RF 評估和開發(fā)套件，板 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型: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:SER3796 |
| LMV228SDX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:RF Power Detector for CDMA and WCDMA |
| LMV228SDX/NOPB | 功能描述:射頻檢測器 RoHS:否 制造商:Skyworks Solutions, Inc. 配置: 頻率范圍:650 MHz to 3 GHz 最大二極管電容: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:SC-88 封裝:Reel |
| LMV228TL | 制造商:Texas Instruments 功能描述:RF DETECTOR BUMP MICRO SMD-4 228 制造商:Texas Instruments 功能描述:IC,RF Amplifier,SINGLE,BGA,4PIN,PLASTIC |
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