General Administration of Quality Supervision, Inspection and Quarantine of the People‘s Republic of China
Status
Latest
GB/T 14557-1993
Scope
This standard specifies the common measurement methods (electric bridge or directional coupler without error identification or slotted measurement line method, double connector method), measurement methods with error identification (electric bridge method, directional coupler method), Typical method and time domain reflectometer method to measure the reflection coefficient of RF coaxial connector and RF coaxial connector adapter. The reflection coefficient of the RF connector shall be measured by mating the standard test connector with the test sample. The adapter shall mate with the standard test connector at both ends. The relevant specifications for specific types of connectors should also specify the corresponding standard test connectors (level 0 connectors). The entire mated pair of standard test connector pairs, including precision transmission lines or cables, shall exhibit the most uniform characteristic impedance. A suitable length of cable shall be attached to the cable connector according to the instructions provided by the connector manufacturer. Preference should be given to cables with close tolerances. It is permissible to use a cable simulator instead of a cable. Time Domain Reflectometry (TDR) should be used to check the uniformity of the measurement device and to check the imperfection of the coaxial transmission line section used and the accuracy of detecting its characteristic impedance. The reflection coefficient shall be expressed as a function of frequency. Measurements should usually be made using a frequency domain approach, preferably using a swept frequency signal generator. When the frequency is about 1GHz, it can be measured by time domain method first, and then converted into frequency domain characteristics. Such measurement has the special advantage of distinguishing the reflection caused by the tested connector from other reflections in the system. Moreover, when the frequency domain method is used for measurement, especially when the frequency is low, it is difficult to distinguish which part of the reflection is caused by. If the point frequency method different from the frequency sweep method is adopted, an appropriately small frequency increment should be used between the test frequency points. Unless the frequency signal generator (usually automatically controlled) can produce very small frequency increments, otherwise, the point frequency method is not a satisfactory method for error resolution. Common devices for measuring reflection coefficient as a function of frequency are RF bridges, directional couplers, and slotted measuring wires. In the absence of special devices that can distinguish errors caused by different defects, generally speaking, only when the reflection coefficient is greater than 0.05 (meaning that the measurement uncertainty should not be greater than 10% of the measured value), the measurement device using these devices is satisfactory. When testing connectors with a specified reflection coefficient limit value below 0.05, it is usually necessary to use a measuring device that can distinguish the effect of errors and can judge the relevant reflection. Some computer-controlled automatic measurement systems, with the addition of an error correction mode, can reduce the measurement inaccuracy of the reflection coefficient at the measurement frequency point without the need for additional error resolution methods. This standard applies to RF coaxial connectors and RF coaxial connector adapters for mating with RF coaxial cables or stripline or microstrip transmission.
GB/T 14557-1993 history
1993GB/T 14557-1993 Electrical tests and measuring procedures for ridio-frequency connectors:Reflection factor