GB/T 34995-2017 in English
VALIDTechnical requirements and measurement methods of receiving equipments for time service in single frequency network
- Issued on:2017-11-01
- Implemented on:2018-02-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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《GB/T 34995-2017单频网授时接收设备技术要求和测量方法》由TC239（全国广播电影电视标准化技术委员会）归口，主管部门为国家广播电视总局。
Introduction
GB/T 34995—2017 Standard Overview
GB/T 34995—2017, the National Standard of the People's Republic of China, is an important standard in the field of time and frequency in my country. It is mainly used to standardize the technical requirements and measurement methods of timing receiving equipment in the single frequency network (SFN) of terrestrial digital television broadcasting. This standard aims to ensure that the performance indicators of timing receiving equipment meet the technical requirements of the national radio and television industry.
Background and Significance of Standard Formulation
With the advancement of the digital transformation of radio and television, the single frequency network (SFN) technology of terrestrial digital television broadcasting has been widely used. As a key component in the SFN system, the performance of timing receiving equipment directly affects the stability and reliability of broadcast signals. The formulation of GB/T 34995—2017 fills the technical gap in this field in China and provides unified technical specifications and test methods for timing equipment in the radio and television industry.
System Framework and Core Components
| Component Name | Functional Description | Technical Requirements |
|---|---|---|
| Timing Receiver Module | Receive GPS or BDS signals and generate time reference signals. | Support multi-system timing and have automatic switching function. |
| Frequency Taming Module | Lock the local oscillator to the standard signal. | Frequency accuracy ≤1E-12, stability ≤5E-11. |
| Local Oscillator | Provides high-precision time signal output. | Uses OCXO technology to output 10MHz and 1pps signals. |
Performance Index Comparison and Actual Application Cases
Table 1 lists in detail the main performance indicators of the timing receiving equipment, including frequency accuracy, phase noise and timing stability. Taking the 10MHz signal as an example, when the GPS or BDS signal is locked, its frequency accuracy requirement is ≤1E-12, which is much better than the performance of traditional timing equipment.
| Indicator Name | Technical Requirements | Actual Application Scenarios |
|---|---|---|
| Frequency Accuracy | ≤1E-12 | Broadcast and Television Network Time Synchronization |
| Phase Noise | ≤-150dBc/Hz (10kHz Offset) | High Precision Timing System |
Analysis of Measurement Equipment and Methods
The standard specifies the measurement requirements for timing receiving equipment, including time and frequency standard equipment and phase noise analyzer. The Time Interval Counter and Frequency Stability Tester can be used to accurately measure the amplitude, frequency accuracy and phase noise of a 10MHz signal.
Implementation recommendations and future prospects
To ensure that the performance of timing receiving equipment complies with the GB/T 34995-2017 standard, it is recommended that:
- Strictly select measurement equipment in accordance with the standard requirements.
- Establish a complete test environment to ensure the stability of GPS and BDS signals.
- Regularly maintain timing receiving equipment to maintain its high-precision performance.
With the development of 5G technology and the Internet of Things, the application scenarios of timing receiving equipment will be more extensive. In the future, the GB/T 34995-2017 standard will play a greater role in the fields of radio, television, communications and navigation.
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