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參數(shù)資料
| 型號： | AD8117 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Video Crosspoint Switch Video Crosspoint Switch |
| 中文描述： | 視頻交叉點開關視頻交叉點開關 |
| 文件頁數(shù)： | 26/32頁 |
| 文件大?。?/td> | 488K |
| 代理商： | AD8117 |
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AD8117/AD8118
Preliminary Technical Data
Currents flowing in conductors create magnetic fields that
circulate around the currents. These magnetic fields then
generate voltages in any other conductors whose paths they
link. The undesired induced voltages in these other channels are
crosstalk signals. The channels that crosstalk can be said to have
a mutual inductance that couples signals from one channel to
another
.
The power supplies, grounds, and other signal return paths of a
multichannel system are generally shared by the various
channels. When a current from one channel flows in one of
these paths, a voltage that is developed across the impedance
becomes an input crosstalk signal for other channels that share
the common impedance
.
All these sources of crosstalk are vector quantities, so the
magnitudes cannot simply be added together to obtain the total
crosstalk. In fact, there are conditions where driving additional
circuits in parallel in a given configuration can actually reduce
the crosstalk. The fact that the AD8117/AD8118 is a fully-
differential design means that many sources of crosstalk either
destructively cancel, or are common-mode to the signal and can
be rejected by a differential receiver.
Rev. PrA | Page 26 of 32
Areas of Crosstalk
A practical AD8117/AD8118 circuit must be mounted to some
sort of circuit board in order to connect it to power supplies
and measurement equipment. Great care has been taken to
create a characterization board (also available as an evaluation
board) that adds minimum crosstalk to the intrinsic device.
This, however, raises the issue that a system’s crosstalk is a
combination of the intrinsic crosstalk of the devices in addition
to the circuit board to which they are mounted. It is important
to try to separate these two areas when attempting to minimize
the effect of crosstalk.
In addition, crosstalk can occur among the inputs to a
crosspoint and among the outputs. It can also occur from input
to output. Techniques will be discussed for diagnosing which
part of a system is contributing to crosstalk.
Measuring Crosstalk
Crosstalk is measured by applying a signal to one or more
channels and measuring the relative strength of that signal on a
desired selected channel. The measurement is usually expressed
as dB down from the magnitude of the test signal. The crosstalk
is expressed by
|XT|
= 20 log
10
(
A
SEL
(
s
) /
A
TEST
(
s
))
where
s
=
jω
is the Laplace transform variable,
A
SEL
(
s
) is the
amplitude of the crosstalk induced signal in the selected
channel, and
A
TEST
(
s
) is the amplitude of the test signal. It can be
seen that crosstalk is a function of frequency, but not a function
of the magnitude of the test signal (to first order). In addition,
the crosstalk signal will have a phase relative to the test signal
associated with it.
A network analyzer is most commonly used to measure
crosstalk over a frequency range of interest. It can provide both
magnitude and phase information about the crosstalk signal.
As a crosspoint system or device grows larger, the number of
theoretical crosstalk combinations and permutations can
become extremely large. For example, in the case of the 32 ×
32
matrix of the AD8117, we can look at the number of crosstalk
terms that can be considered for a single channel, say the IN00
input. IN00 is programmed to connect to one of the AD8117
outputs where the measurement can be made.
First, the crosstalk terms associated with driving a test signal
into each of the other 31 inputs can be measured one at a time,
while applying no signal to IN00. Then the crosstalk terms
associated with driving a parallel test signal into all 31 other
inputs can be measured two at a time in all possible
combinations, then three at a time, and so on, until, finally,
there is only one way to drive a test signal into all 31 other
inputs in parallel.
Each of these cases is legitimately different from the others and
might yield a unique value, depending on the resolution of the
measurement system, but it is hardly practical to measure all
these terms and then specify them. In addition, this describes
the crosstalk matrix for just one input channel. A similar
crosstalk matrix can be proposed for every other input. In
addition, if the possible combinations and permutations for
connecting inputs to the other outputs (not used for
measurement) are taken into consideration, the numbers rather
quickly grow to astronomical proportions. If a larger crosspoint
array of multiple AD8117s is constructed, the numbers grow
larger still.
Obviously, some subset of all these cases must be selected to be
used as a guide for a practical measure of crosstalk. One
common method is to measure all hostile crosstalk; this means
that the crosstalk to the selected channel is measured while all
other system channels are driven in parallel. In general, this will
yield the worst crosstalk number, but this is not always the case,
due to the vector nature of the crosstalk signal.
Other useful crosstalk measurements are those created by one
nearest neighbor or by the two nearest neighbors on either side.
These crosstalk measurements will generally be higher than
those of more distant channels, so they can serve as a worst-
case measure for any other one-channel or two-channel
crosstalk measurements.
相關PDF資料 |
PDF描述 |
|---|---|
| AD811 | High Performance Video Op Amp(高性能視頻運放) |
| AD8123 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-R2 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-R7 | Triple Differential Receiver with Adjustable Line Equalization |
| AD8123ACPZ-RL | Triple Differential Receiver with Adjustable Line Equalization |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| AD8117_07 | 制造商:AD 制造商全稱:Analog Devices 功能描述:600 MHz, 32 】 32 Buffered Analog Crosspoint Switch |
| AD8117ABPZ | 功能描述:IC CROSSPOINT SWIT 32X32 304BGA RoHS:是 類別:集成電路 (IC) >> 接口 - 模擬開關，多路復用器，多路分解器 系列:- 其它有關文件:STG4159 View All Specifications 標準包裝:5,000 系列:- 功能:開關 電路:1 x SPDT 導通狀態(tài)電阻:300 毫歐 電壓電源:雙電源 電壓 - 電源，單路/雙路(±):±1.65 V ~ 4.8 V 電流 - 電源:50nA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:7-WFBGA，F(xiàn)CBGA 供應商設備封裝:7-覆晶 包裝:帶卷 (TR) |
| AD8117-EVAL | 制造商:AD 制造商全稱:Analog Devices 功能描述:600 MHz, 32 】 32 Buffered Analog Crosspoint Switch |
| AD8118 | 制造商:AD 制造商全稱:Analog Devices 功能描述:600 MHz, 32 】 32 Buffered Analog Crosspoint Switch |
| AD8118ABPZ | 功能描述:IC CROSSPOINT SWIT 32X32 304BGA RoHS:是 類別:集成電路 (IC) >> 接口 - 模擬開關，多路復用器，多路分解器 系列:- 其它有關文件:STG4159 View All Specifications 標準包裝:5,000 系列:- 功能:開關 電路:1 x SPDT 導通狀態(tài)電阻:300 毫歐 電壓電源:雙電源 電壓 - 電源，單路/雙路(±):±1.65 V ~ 4.8 V 電流 - 電源:50nA 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:7-WFBGA，F(xiàn)CBGA 供應商設備封裝:7-覆晶 包裝:帶卷 (TR) |
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