IEC 60512-25-2:2002 pdf download
IEC 60512-25-2:2002 pdf download.Connectors for electronic equipment-Tests and measurements – Part 25-2: Test 25b – Attenuation (insertion loss).
2.1.2 Time domain
A time domain reflectometer (TDR), triggered impulse generator and appropriate fast Fourier
transform (FFT) software are preferred.
2.2 Fixture
Unless otherwise specified in the reference document, the specimen environment impedance shall match the impedance of the test equipment. Typically, this will be 50 fl for single-ended measurements and 100 fl for differential measurements.
2.2.1 Specimen conductor assignments
For each measurement, the line to be measured shall be fixed as indicated in the referencing document. The far end (destination) and the near end (driven) of the line shall be terminated in the specimen environment impedance specified using one of the methods in figures A.2 or
A.3. In the special case where the drive signal is differential and not balanced, the common mode energy shall be terminated. Signal lines adjacent to these should likewise be terminated, if possible.
NOTE Electrically long adjacent signal lines may resonate adding error to the results.
Unless otherwise specified, a 1:1 signal-to-ground ratio (2:1 if differential measurements are performed) shall be used with each end having all grounds commoned. (For an example, see figure A.4).
2.2.2 Specimen fixture and signal line terminations for specimen environment impedance
Care should be taken to minimize the reactances of the resistive terminations over the range of test frequencies.
NOTE The fixture geometry and materials may impact the measurements due to the fixture parasitics. Usually, the product’s intended use dictates the most meaningful way to fix It.
2.2.3 InsertIon technique
The fixture shall be designed to allow the measurement of attenuation with and without the specimen, see figure Ala. If baluns are used for a measurement, or minimum loss pads used for impedance matching. these are included in the fixture. Figures A.2 and A.3 show typical configurations with minimum loss pads.
2.2.4 Reference fixture technique
In this technique, a separate fixture that combines both near end and far end is used for the fixture attenuation measurement; see figure A.lb. This fixture shall be a duplicate of the specimen fixture, only without the specimen. Traces, if used, shall include fixture connectors, vias, bends and corners. If baluns are used for a differential measurement, or minimum loss pads used for impedance matching, these are included in the fixture. Figures A.2 and A.3 show typical configurations with minimum loss pads.
Assembled connectors and cables, and mating connectors.
3.1.3 Sockets
A socket and test device or a socket and pluggable header adapter,
4 Test procedure
Unless otherwise specified, all measurement results shall contain a minimum of 200 frequency points. Each fixture measurement and its associated specimen attenuation measurement shall be taken at the same frequencies. Generate a magnitude versus frequency plot: 1 dB per division vertical scale and log frequency sweep are recommended. When applicable, single frequency results shall be tabulated, as specified in the reference document. Place the specimen at a minimum of 5 cm from any objects that would affect measured results.
NOTE Test professionals should be aware of the limitations of any math operation(s) performed by an instrument (e.g. normalization or software filtering).
4.1 FIxture attenuation
Fixture attenuation shall be measured separately so that it can be removed from and compared to the specimen measurement. If the reference document specifies precisely the fixture so that its attenuation contribution is known, then the fixture attenuation measurement is optional.
4.1.1 Calibration
4.1.1.1 When using a network analyzer, as a minimum, a Nthrough calibration at the reference plane (including analyzer cables, but not the specimen fixture) shall be performed. Where possible, a 12 term calibration is recommended.
4.1.1.2 When using a spectrum analyzer and generator, take a reference measurement following the same procedure. The generator output shall be kept the same for both fixture and specimen-with-fixture attenuation measurements made later.
NOTE Results may be inaccurate when:
a) The specimen attenuation Is not greater than the fixture attenuation.
b) The fixture electrical length is greater than 1)8 wavelength at the highest test frequency, unless special precautions are taken to ensure good impedance matching throughout the measurement path. This can be confirmed by sweeping across a wide frequency range and observing if there are nulls due to moding, fixture or balun resonances, etc.
