ANSI EIA 364-90-2000 pdf free download.Crosstalk Ratio Test Procedure for Electrical Connectors, Sockets, Cable Assemblies or Interconnect Systems
1.1 Scope
This procedure applies to interconnect assemblies, such as electrical connectors, sockets and cable assemblies.
1.2 Object
This standard describes test methods for measuring the magnitude of the electromagnetic coupling between driven and quiet lines of an interconnect assembly. Both time domain (method A) and frequency domain methods (method B), single-ended and differential transmission, and insertion and reference fixture techniques are described.
1.3 Definitions
1.3.1 Drive signal
For the time domain method, the drive signal is a step waveform. For the frequency domain method, the drive signal is sinusoidal.
1.3.2 Crosstalk ratio
The ratio of the signal coupled (induced) into the quiet signal conductor or conductor pair to the magnitude of the signal in the driven conductor or conductor pair. Both signals shall have the same units of either voltage or current, and the ratio may be expressed as percent or dB.
1.3.3 Near end crosstalk ratio (NEXT)
The crosstalk ratio calculated on the quiet line at or in proximity to the sending (signal source) end of the driven line. This is the ratio of the near end quiet line signal amplitude to the near end driven line signal amplitude.
1.3.4 Far end crosstalk ratio (FEXT)
The crosstalk ratio calculated on the quiet line at or in proximity to the receiving (destination)
end of the driven line. This is the ratio of the far end quiet line signal amplitude to the near end
driven line signal amplitude.
1.3.5 Measurement system rise time
Rise time measured with fixture in place, without the specimen, and with filtering (or
normalization). Rise time is typically measured from 10% to 90% levels.
1.3.6 Specimen environment impedance
The impedance presented to the specimen signal conductors by the fixture. This impedance is a
result of transmission lines, termination resistors, attached receivers or signal sources, and fixture
parasitics.
1.3.7 Step amplitude
The voltage difference between the 0% and 100% levels, ignoring overshoot and undershoot, as
indicated in figure 1.
1.3.8 Isolation standard
A reference fixture without a test specimen and with identical crosstalk characteristics as the test
fixture. This fixture may or may not be part of the test board.
1.3.9 Termination (electronics usage)
An impedance connected to the end of a transmission line, typically to minimize reflected energy
on the line.
2 Test resources
2.1 Equipment
2.1.1 Method A, time domain
2.1.1.1 A step generator is used on the driven line and an oscilloscope monitors the quiet line. In
a differential application both shall be able to process differential signals. Typically, this means
complementary outputs with provision for amplitude and skew adjustment, and dual inputs with
a display of the difference and sum. Filtering or normalization shall be available for varying the
rise time. A time domain reflectometer (TDR) is usually used.
NOTE — The test professional should be aware of limitations of any math operation(s)
performed by an instrument, (e.g. normalization or software filtering).
2.1.1.2 Probes
Probes, when used, shall have suitable rise time performance and circuit loading characteristics
(e.g. resistance and capacitance).
2.1.2 Method B, frequency domain
A network analyzer is preferred. When greater dynamic range is desired, a signal generator and
spectrum analyzer may alternatively be used. An 8 port network analyzer or baluns may be used
for differential measurements.
2.2 Fixture
Unless otherwise specified in the referencing document the specimen environment impedance
shall match the impedance of the test equipment. Typically this will be 50 ohms for single-ended
measurements and 100 ohms for differential.
2.2.1 Specimen conductor assignments
For each measurement, the driven and quiet lines shall be fixtured as indicated in the referencing
document. Adjacent signal lines to these should likewise be terminated if possible (electrically
long adjacent signal lines may resonate adding error to the results). Unless otherwise specified a
1:1 signal to ground ratio (one differential pair to one ground if differential measurements are
performed) shall be used with each end having all grounds commoned, for an example, see
figure A.4. The fixture should be designed with equal delays for all lines.
