1、EIA SPECIFICATIONRigid Coaxial Transmission Lines and Connectors - 50 OhmsEIA-225-A (Revision of EIA-RS-225) April 2018 Electronic Components Industry Association ANSI/EIA-225-A-2018 Approved: April 5, 2018 EIA-225-ANOTICEEIA Engineering Specifications and Publications are designed to serve the publ
2、ic interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Specifications
3、and Publications shall not in any respect preclude any member or nonmember of ECIA from manufacturing or selling products not conforming to such Specifications and Publications, nor shall the existence of such Specifications and Publications preclude their voluntary use by those other than ECIA memb
4、ers, whether the Specification is to be used either domestically or internationally. NOTE The users attention is called to the possibility that compliance with this standard may require use of an invention covered by patent rights. By publication of this standard, no position is taken with respect t
5、o the validity of any such claim(s) or of any patent rights in connection therewith. If a patent holder has filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and conditions to applicants desiring to obtain such a license, then details ma
6、y be obtained from the standards developer Neither the standards developer nor ANSI is responsible for identifying patents for which a license may be required by an American National Standard or for conducting inquiries into the legal validity or scope of those patents that are brought to their atte
7、ntion.This EIA Specification is considered to have International Standardization implications, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the EIA Specification and the IEC document can be made. This Specification does n
8、ot purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this Specification to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (F
9、rom Standards Proposal No. 5370, formulated under the cognizance of the CE-2.2 Committee on RF Connectors and Rigid Coax Connectors and previously published in EIA-RS-225) Published by Electronic Components Industry Association 2018 EIA Standards the drawings define the necessary mechanical limits n
10、ecessary for mechanical interchangeability. 1.2 Size: 1.2.1 Definition: The size of a coaxial line is defined as the nominal outside diameter of the line, expressed in inches. The size of the connector is defined by the nominal outside diameter of the line with which it is used. Metric dimensions ar
11、e for reference only and are based upon 1.0 inch equals 25.4 mm. 1.2.2 Standard: The standard line sizes are specified in Table 1. The standard connector sizes are given in Figures 1, 2, 3 and 4. 2. Dimensions 2.1 Definitions: 2.2 Average Wall Thickness: Is one-half the difference between the corres
12、ponding inside and outside diameters. 2.3 Maximum Deviation: The wall thickness from the average wall thickness is the difference between the average wall thickness and either the maximum or minimum wall thickness measurement, whichever difference is greater. EIA-225-A Page 2 2.4 Standard: Dimension
13、s and tolerances for the lines are specified in Table 1. Dimensions and tolerances for the connectors are shown on Figure 1 thru Figure 3. EIA-225-A Page 3 3. Characteristic Impedance 3.1 Definition: The characteristic impedance of a coaxial transmission line is the driving impedance of the transmit
14、ted transverse electromagnetic wave. 3.2 Standard: The characteristic impedance for each line size is shown in Table 2. 3.3 Method of Determination: For a structurally uniform transmission line, the characteristic impedance shall be calculated from the appropriate formula. For a structurally non-uni
15、form line with transparent individual supports, the characteristic impedance shall be determined experimentally with measuring equipment or conventional transmission line and network theory of the necessary accuracy. For a structurally non-uniform line achieving electrical transparency by means of a
16、 systematic supporting structure, the characteristic impedance shall be determined between groups of supports. NOTE: Connectors shall be included as part of the transmission line and shall comply with the requirements specified for the transmission line. 4. Attenuation per Unit Length 4.1 Definition
17、: Attenuation is a reduction in signal strength occurring while transmitting signals over distances 4.2 Standard: Attenuation shall be expressed as a power ratio in decibels per unit length of line at a specified frequency and with specified conductor temperature. 4.3 Method of Determination: Attenu
18、ation shall be determined by a suitable method of measurement. 5. Standing Wave Ratio (SWR) 5.1 Definition: The standing wave ratio is the ratio between transmitted and reflected waves in a transmission line. Note: The standing wave ratio S in a uniform transmission line is given by: = 1 + 1Where p
19、is the magnitude of the reflection coefficient of the load. EIA-225-A Page 4 5.2 Standard: Standing wave ratio shall be expressed as a voltage ratio and shall be as required for the application. 5.3 Method of Determination: The standing wave ratio of any line section with connectors shall be determi
20、ned by connecting it between a uniform line and a load which are equal respectively to the nominal characteristic impedances of the line under test. The SWR of the section under test shall be that SWR measured in the uniform line. 6. Power Ratings 6.1 Definition: The peak power rating of a line and
21、connectors is that level of transmitted power which permits satisfactory operation of the assembly and provides an adequate safety factor below the level where injury or appreciably shortened life will occur. Power rating has two applications: continuous wave power and peak power. Peak power rating
22、is limited by the voltage breakdown ratio between transmitted and reflected waves (See Voltage Rating, Para 7.) The RMS value of a pulse of RF power passing through the transverse section of the coax, which if exceeded, will cause voltage breakdown; see Voltage Rating, see Para 7. The peak power han
23、dling can be recalculated in kW peak. The peak power rating defines ability of the line to handle the pulse operations. The continuous wave power handling is limited by condition when the dielectric temperature around center conductor exceeds the maximum value (thermal breakdown or that point where
24、the materials of construction used are degraded by the temperature rise). 6.2 Standard: The continuous wave power rating, at unity standing wave ratio unless otherwise limited, shall not exceed power that results in an inner conductor temperature of 100 C for copper conductors at an ambient temperat
25、ure of 50 C and shall include a statement of all applicable limiting factors, or ratings, that may limit suitability for an application. 6.3 Method of Determination: The power of a line including connectors shall be determined experimentally by thermal breakdown, life and related tests. There are se
26、veral tables and charts designed for cross-referencing which types of connectors need to be tested for which space environments and for cross-referencing what types of tests are necessary for what type of connector when being used in any space environment. 7. Voltage Ratings 7.1 Definition: The volt
27、age rating of a line and connectors is that value of transmitted voltage which permits satisfactory operation of the line assembly and provides an adequate safety factor below the point EIA-225-A Page 5 where injury or appreciably shortened life will occur. 7.2 Standard: The voltage rating, at unity
28、 standing wave ratio unless otherwise limited, either shall not exceed that which will result in an inner conductor to outer conductor dielectric breakdown at an ambient temperature of 50 C and shall include a statement of all applicable limiting factors, or the rating shall be suitable for the appl
29、ication. 7.3 Method of Determination: The voltage ratings of a line including connectors shall be determined experimentally by breakdown, life and related tests. There are several tables and charts designed for cross-referencing which types of connectors need to be tested for which space environment
30、s and for cross-referencing what types of tests are necessary for what type of connector when being used in any space environment. 8. Upper Frequency Limit 8.1 Definition: The upper frequency limit is determined by the cut-off frequency of higher order modes of propagation, and the effect which they
31、 have on the impedance and transmission characteristics of the normal TEM coaxial transmission line mode. The lowest cut-off frequency occurs with the TE11 mode, and this cut-off frequency in air dielectric line is the upper frequency limit of a practical transmission line. How closely the TE11 mode
32、 cut-off frequency can be approached depends on the application. 8.2 Standard: In general, it does not seem advisable to use coaxial line frequencies greater than 0.95 of the TE11 mode cut-off frequency. Supporting structures will further decrease the upper frequency limit. Practical experience indi
33、cates that 0.95 of the TE11 mode cut-off frequency in the overcut, undercut, or overcut-undercut insulator portion of the line will serve as a useful limit for most applications. The TE11 mode cut-off frequency, for air dielectric, Teflon and polystyrene overcut and undercut insulators is specified
34、in Table 1. The cut-off frequency typically doesnt imply the second mode transmission. It suggests the possibility of transmission. The dual mode transmission will begin from the TE11 mode resonance. In some applications it is allowable to use the transmission line at frequencies higher than cut-off
35、 but lower than mode resonance. Practically this means that the upper frequency limit of the transmission line can be higher than cut-off of the airline and lower than the resonant frequency of the supporting dielectric beads. 8.3 Method of Determination: The TE11 mode cut-off frequency can be readi
36、ly estimated by assuming the mean circumference calculated from the outer conductor inside diameter and inner conductor outside diameter is equal to one wavelength at the cut-off frequency. This will be in error less than 3% for 50 ohm coaxial line with insulating materials ordinarily utilized in hi
37、gh frequency coaxial lines. Appropriate theoretical expressions may be used for calculating the TE11 mode cut-off frequency of the particular line selected for the application. EIA-225-A Page 6 NOTE: Connectors shall be included as part of the transmission line and shall comply with the requirements
38、 for the transmission line. 9. Curvature 9.1 Definition: Curvature is the radial departure from a straight line between any two points on the external surface of a conductor. 9.2 Standard: Curvature of rigid coax shall not to exceed ” (12.7) for any ten foot (3 meter) portion of the total length. 9.
39、3 Method of Determination Measurement of curvature shall not be altered by gravity or any other forces. 10. Out-of-Roundness 10.1 Definition: Out-of-Roundness is the difference between the major and minor diameters at any one cross-section of a conductor. 10.2 Standard: Out-of-Roundness shall confor
40、m to best commercial practice. 11. Material and Workmanship 11.1 Material: To be specified by user. 11.2 Workmanship: The interior surface of the outer conductor, the exterior and interior surfaces of the inner conductor, and all mating surfaces of connectors and conductors shall be as free as possi
41、ble from detrimental holes, burrs, die marks, chatter marks or foreign materials. 12. Packaging and Packing Each length of transmission line assembly shall have protective covering at both ends. Packing shall be such as to assure that after shipping and handling the transmission line assembly shall
42、meet the requirements of this standard. EIA-225-A Page 7 13. Pressure Tightness 13.1 Definition: Pressure tightness is the ability of the transmission line and connector to maintain an internal pressure of dry gas, as commonly used to prevent the entrance of moisture or other foreign material. 13.2
43、Standard: The outer conductor and connector shall be capable of withstanding a pressure up to 60 lbs/in2(1661 gm/cm2) gage pressure without rupture. Gas leakage from a pressurized transmission line assembly shall not cause the pressure to drop more than 2 pounds per square inch (55.4 gm/cm2) in 24 h
44、ours, from an initial pressure of pounds per square inch gauge pressure, correction being made for temperature and barometric changes from start to finish of test. 13.3 Method of Determination: The pressure shall be measured in pounds per square inch above the maximum atmospheric pressure; and shall
45、 be determined experimentally. A shorter testing time than that specified above may be employed, if it provides the same time rate of leakage. Environmental conditions at the time of test shall be specified. 14. Designation 14.1 Line Size: The designation for coaxial lines in accordance with this st
46、andard shall include the line size and the nominal characteristic impedance. For example, for a 1 5/8 line it shall be as follows: 1 5/8 (50) 14.2 Impedance: The impedance and size of the anchor insulators included with the connectors in this standard shall be marked as below. For example, for a 3 1
47、/8 connector it shall be as follows: 3 1/8 (50) 14.3 Marking: The designation numbers shall be marked on the outside surface of the outer conductor of each length of finished coaxial line in such a way as not to deform the inside surface of the conductor. EIA-225-A Page 8Table 1 Dimensions and Toler
48、ances for Rigid Air Dielectric Coax Dimension in Inches (millimeters) Line Size (Nom) Outer Conductor Inner Conductor A Dia B Dia Wall Thickness C Dia D Dia Wall Thickness Nominal Maximum Deviation from Average Nominal Maximum Deviation from Average 6 1/8 6.125 0.008 (155.58 0.20) 5.981 0.008 (5.98
49、0.20) 0.072 (1.83) 0.012 (0.30) 2.600 0.004 (66.04 0.10) 2.520 0.004 0.04 (1.02) 0.0075 (1.90) 3 1/8 3.125 0.005 (79.375 0.005) 3.027 0.005 (76.89 0.13) 0.049 (1.25) 0.0075 (0.19) 0.869 0.0025 (22.07 .06) 0.799 0.0025 (20.29 0.06) 0.035 (0.89) 0.005 (0.13) 1 5/8 1.625 0.003 (41.275 0.076) 1.527 0.003 (38.79 0.08) 0.049 (1.25) 0.005 (0.13) 0.438 0.002 (11.13 0.05) 0.378 0.002 (9.60 0.05) 0.030 (0.76) 0.003 (0.08) 7/8 0.875 0.0025 (22.225 0.064) 0.785 0.0025 (19.94 0.06) 0.045 (1.14) 0.005 (0.13) 0.226 0.002 (5.74 0.05) 0.176 0.002 (4.47 0.05)
