1、 EIA STANDARD TP-80 Low Frequency Shielding Effectiveness Test Procedure for Electrical Connectors and Sockets EIA-364-80 NOVEMBER 2002 ELECTRONIC COMPONENTS, ASSEMBLIES RF amplifier; 200 ohm loads (non-inductive); 50 ohm loads; analyzer(s), network or spectrum; shielded cable and connectors; curren
2、t probe. 2.1.1.1 Signal source The signal source shall be an RF generator(s) with an output frequency of 10 kHz to 100 MHz, (method A), or 30 MHz to 500 MHz, (method B). The signal source may be part of the network analyzer(s). 2.1.1.2 RF amplifier The RF amplifier shall provide enough gain to raise
3、 the signal source output to 1 watt. 2.1.1.3 Analyzer The analyzer shall be either a network or spectrum analyzer and shall provide amplitude and may provide phase output from 10 kHz to 100 MHz, (method A), or 30 MHz to 500 MHz, (method B). More than one unit may be used to obtain the required plots
4、/values frequency band. 2.1.1.4 Data collection system This system shall be capable of interfacing with the analyzer and recording amplitude outputs. EIA-364-80 Page 4 2.2 Special test equipment, method A 2.2.1 Quadraxial test facility This shall be shielded metal enclosure with provisions for test
5、specimen installation, drive plate and guard coaxial chamber installation. See Appendix A for construction guidelines. 2.2.2 Connector test specimen adapters These shall be solid metal tubular backshells designed to interface with the connector accessory threads on one end and a type N plug on the o
6、ther. The adapters shall be designed to minimize transfer impedance contributions from other than the connector under test. The inner diameter shall be such that a 50 ohm characteristic impedance is maintained in conjunction with the center contact adapters; see annex A for fabrication details. 2.2.
7、3 Center contact adapters These shall be solid brass or bronze rods with the appropriate contacts on one end and type N socket on the other. 3 Test specimen 3.1 Preparation 3.1.1 Method A All wires shall be removed. Install the appropriate center contact adapters in both the plug and receptacle. Ins
8、tall the backshell adapters on the connectors. 3.1.1.1 Installation Install the test specimen in the inner chamber of the Quadraxial fixture, placing the current probe as shown in figure A-1. Tighten jam nuts to hold specimen in place. Connect one end of the adapter to the analyzer receiver channel
9、and terminate the other end to the 50 ohm load 3.1.1.2 Connection Connect instrumentation and measurement equipment as shown in figure 1. EIA-364-80 Page 5 Figure 1 - Test configuration 3.1.2 Method B 3.1.2.1 Panel mounted connector specimen Mount connector in the center of a bulkhead mounting plate
10、 (figure C.2, Annex C). Common all contacts as close to the bulkhead as possible. A 2 cm - 3 cm wide copper strap shall be soldered to the bulkhead mounting plate close to the CUT. The free end should be very close to the bussed panel mount connector conductors. The shield of a short probe cable sha
11、ll be soldered to the strap to form a low inductance path to the bulkhead, not the panel mount connector shield. This connection must be short as possible. Solder the center conductor to the bussed panel mount connector conductors. This connection should be as short as possible. Assemble the fixturi
12、ng of figure C.2. Be sure metal surfaces joined are cleaned for a good connection. ANALYZER EIA-364-80 Page 6 3.1.2.1.1 Measure specimen Zowith TDR A specimen connector shall be mounted on several inches of shielded cable. All conductors in this connector shall terminate a conductor in the cable. Ma
13、te to panel mounted connector specimen fixtured in 3.1.2.1. Use time domain reflectometry (TDR) to determine the voltage reflection coefficient of the mated pair. Estimate an average value if necessary. This will be used to calculate a correction factor (CF). 3.1.2.2 Cable mounted connector specimen
14、 Cut the cable on each specimen about 3 cm from the rear. Remove the outer jacket without nicking the braid, leaving 0.5 cm of outer jacket. Fold back braid over remaining outer jacket. Remove second foil shield, if present. Take care to avoid stressing the connector shield braid capture region. Str
15、ip all internal conductors, as close to the braid as practical. Twist together all internal conductors and solder. Cut soldered wires to 0.3 cm. Solder a non-inductive (metal film) termination resistor to this. Wrap this joint with high temperature insulating tape (Kapton). The termination resistor
16、shall be chosen to give a voltage reflection coefficient close to that measured in 3.1.2.1.1. Wrap the joint and termination resistor with copper tape. Dress the braid up over the copper tape. Wrap the braid and copper tape up to the free resistor lead with small gauge solid hook-up wire. Solder the
17、se together to prevent any RF leakage. 4 Test procedure 4.1 Method A With the connector and chamber configured per clause 3, the following procedure shall be performed. The test configuration shall be per figure A.1. 4.1.1 Calibration and initial set-up 4.1.1.1 Load calibration data (see Appendix B)
18、 into data processor system. 4.1.1.2 Connect instrumentation per Figure 1 (below). Adjust system gains and attenuations to ensure that all system elements are operating within their dynamic ranges. This is done by performing trial sweeps until satisfactory performance is obtained. 4.1.2 Specimen tra
19、nsfer impedance measurements 4.1.2.1 Set low frequency limit to 10 kHz maximum. 4.1.2.2 Set upper frequency limit to 100 MHz minimum. 4.1.2.3 Perform transfer impedance measurement. Measurements shall be taken from 10 kHz to 100 MHz. a minimum of 10 points per decade shall be sampled. When more than
20、 one instrument is required, the measurement bands shall overlap by 25% minimum. EIA-364-80 Page 7 4.1.2.4 Plot Z() for test specimen. Measured results shall be reported in dB from one ohm, )ohm 1( / log 20dBZ= 4.2 Method B 4.2.1 Do a full 2 port calibration if using a vector network analyzer for im
21、proved accuracy. 4.2.2 Collect a noise floor plot; see C.1.4). 4.2.3 Prepare panel mounted connector specimen(s); see 3.1.2.1. 4.2.4 Measure specimen Zo; see 3.1.2.1.1. NOTE Note the voltage reflection coefficient (p) for use in 4.2.8. 4.2.5 Prepare cable mounted specimens; see 3.1.2.2.2. 4.2.6 Coll
22、ect a reference measurement; see C.1.1. Place a cable mounted specimen in the fixturing of figure C.1. Solder the electrical connection at the right so that pressure is applied at the mechanical connection at the left (the fixture connection to the mating interface). Measure S21(reference) expressed
23、 in dB, or measure the power at the spectrum analyzer in dBm. The frequency range shall be 30 MHz to 500 MHz. 4.2.7 Collect the specimen measurements; see C.1.2. With the same cables, substitute the specimen measurement fixturing of figure C.2 for the reference measurement fixturing of 4.2.6 (figure
24、 C.1). Mate the connectors under test and connect to the type “N“ connector at the right. Measure S21(specimen) expressed in dB, or measure the power at the spectrum analyzer in dBm while driving the specimen with the same forward power (into fixture port 1, figure C.2 ) as used in 4.2.6. 4.2.8 Calc
25、ulate the correction factor. In dB it would be: )1/(2( log 20)dB( pCF = where p is the voltage reflection coefficient of the termination resistor, determined in 4.2.4 and 4.2.5 (C.1.3). EIA-364-80 Page 8 4.2.9 The vertical axis of the trace can now be labeled in units of dB-ohm: (dB) CF )(reference
26、dBm - (specimen) dBm ohm) - dB( +=Z (dB) CF )(reference - (specimen) 2121+= SS , where S21is expressed in dB. NOTE Note that the subtraction above can be done by many instruments real time. If so, the reference gradicule of the subtracted results can be assigned a value of (-1)CF(dB), that would mak
27、e it equal to 0 dB-ohm or, a controller may do these calculations. 4.2.10 Plot transfer impedance in log-log format, save plot file and record single frequency results. 4.2.11 Check that all points on the transfer impedance plot (trace) exceed the noise floor plot 4.2.2 by at least 10 dB. NOTE Note
28、potentially inaccurate regions in the plot. 5 Details to be specified The following details shall be specified in the referencing document: 5.1 Method A 5.1.1 Frequency range (if different than 1.1) 5.1.2 Marker frequencies (specific frequencies to evaluate connector performance), if desired 5.1.3 N
29、umber of specimens to be tested 5.1.4 Phase plots, if desired 5.2 Method B 5.2.1 Frequency range, if other than 4.2.6 5.2.2 Marker frequencies (specific frequencies to evaluate connector performance), if desired. 5.2.3 Number of specimens to be tested 5.2.4 Phase plots, if desired EIA-364-80 Page 9
30、6 Documentation Documentation shall contain the details specified in clause 5, with any exceptions, and the following: 6.1 Method A 6.1.1 Test number 6.1.2 Specimen identification 6.1.3 Test equipment used, and date of last and next calibration 6.1.4 Plots, (log log format, including 10 kHz -100 MHz
31、 data) 6.1.5 Name of operator and date of test 6.2 Method B 6.2.1 Test number 6.2.2 Specimen identification 6.2.3 Test equipment used, and date of last and next calibration 6.2.4 Correction factor in dB, or termination resistance, if applicable 6.2.5 Marker Frequency results, if requested 6.2.6 Nois
32、e floor plot 6.2.7 Note any data that fails the noise floor requirement 6.2.8 Plots, (log log format, including 30 MHz - 500 MHz data) 6.2.9 Name of operator and date of test EIA-364-80 Page A-1 Annex A Test method A A.1 Quadraxial fixture design requirements A.1.1 Material The fixture shall be fabr
33、icated from brass per QQ-B-613. The fixture end plates shall use 2 mm minimum thickness. Stock thickness of the balance of the fixture is optional. A.1.2 Design The inner RF drive box and the outer enclosure shall be designed to obtain 50 ohm characteristic impedances with respect to each other and
34、the test specimen, see A2.1 and A2.2. Any fixture design that differs from figure A.1 shall be quadraxial, maintain the specified 50 ohm characteristic impedances and preserve the input/output relationships noted in figure A.1. A1.2.1 Inner RF drive box The box shall be as shown in figure A.1. The b
35、ox is suspended by four UG-58A/U connectors at one end and four 200 ohm resistors at the other. The ends are open. The box may be supported using care to minimize impact to the air dielectric constant between the inner and outer portion of the fixture. A1.2.2 Outer enclosure The enclosure shall have
36、 provisions for installation of the appropriate test connectors, termination of the four resistors, and installation of the test specimen per figure A.2. The top of the fixture shall be removable. A1.2.3 Configuration The quadraxial fixture shall be as shown in figure A.1. All dimensions in centimet
37、ers unless otherwise noted. EIA-364-80 Page A-2 Figure A.1 - Quadraxial test fixture EIA-364-80 Page A-3 A.2 Connector test specimen adapter A2.1 Material Connector adapters shall be fabricated from brass per QQ-B-613 or copper per QQ-C-502. Dielectric material shall be polyethylene per L-P-390. A2.
38、2 Design The test specimen adapters shall be designed to provide a 50 ohm characteristic impedance with respect to center conductor and comply with figure A.2. All threaded joints shall be designed to minimize RF leakage. Figure A.2 - Connector under test EIA-364-80 Page B-1 Annex B B Test method B
39、B.1 Fixture calibration procedure B1.1 The quadraxial test fixture is calibrated by characterizing the current probe to a 50-ohm calibration reference, the instrumentation amplifier, the attenuator and the cables per figure B-1. The constants are divided out of the raw test data to obtain the calibr
40、ated results. For an automated system, the calibration constants are stored in the computer memory and the floppy disc file for processing the test data. Remember to include a 6 dB compensation B1.2 The coherent noise integrity of the fixture is checked by substituting a hollow copper rod for the co
41、nnector and measuring its transfer impedance. The levels are typically more than 90 dB below 1 ohm. Individual connector setups can be checked by installing braid over the connector under test and clamping to the copper transition sections at each end of the connector. Credible data will be at least
42、 10 dB higher. Figure B.1 - Calibration setup PRECISION 50 OHM RESISTOR EIA-364-80 Page C-1 Annex C C Test setup and calibration C.1 Test method B C.1.1 Reference measurement C.1.1.1 This technique relies on comparing two measurements that differ only in where the drive energy is placed. In the refe
43、rence measurement (see Figure C-1), the radio frequency (RF) current flows through the one ohm standard. The resulting voltage drives the specimen on the outside, and the resulting power is measured at port 2, (or, this can be measured as S21(reference). This voltage is equal to the voltage that wou
44、ld be generated if the specimen had a one ohm transfer impedance at all frequencies. C.1.1.2 This simple resistance is made to mimic a transfer impedance. Thus, the reference measurement only includes the fixturing response when the specimen is mounted in it. Figure C.1 - Reference measurement fixtu
45、ring EIA-364-80 Page C-2 C.1.2 Specimen measurement The second measurement (specimen measurement, figure C.2) applies the same amount of incident RF power to the inside of the specimen. The fixturing has exactly the same dimensions. The current from this incident power passes through the connector u
46、nder test transfer impedance, producing a voltage along the length of the specimen. The resulting power is measured at port 2 of figure C.2 (or, this can be measured as S21(specimen). The measurement includes the fixturing response previously measured times the transfer impedance of the specimen. Fi
47、gure C.2 - Specimen measurement fixturing C.1.3 Calculations The transfer impedance can be derived from these two measurements. The specimen measurement results are divided by the reference results at each frequency (subtract dB), leaving just the specimen transfer impedance. Finally, the results mu
48、st be multiplied by a frequency independent correction factor CF). Even with identical RF drive levels, the current through the one ohm standard of the reference measurement will differ from the inside current of the specimen measurement. EIA-364-80 Page C-3 C.1.4 Noise floor plot C.1.4.1 If the spe
49、cimens have very good shielding, the fixturing shielding may be inadequate, or the receiver may be picking up ambient signals. Before specimens are measured, some idea of this level must be available. This shall be obtained with the noise floor fixturing of figure C.3. C.1.4.2 The noise floor plot is obtained just like a transfer impedance measurement but with a solid panel and no connector under test. The reference measurement is the same as used in calculating connector transfer impedance; see 4.2.6. The specimen measurement is made as in figure C.3. The specimen
