SRRC Filing Timelines for a Product Entering China
SRRC radio type approval in China takes 8 to 16 weeks, requiring local agent representation, strict customs sample clearing, and accredited domestic lab scans.
Ground Loop Harmonic Emission
Meaning
Electromagnetic noise currents flowing through a common return path generate unintended signals that interfere with sensitive analog and digital circuits. The suppression of ground loop harmonic emission is essential in integrated systems where high-speed processors share a reference plane with wireless transceivers. This phenomenon is limited to conducted pathways and does not include radiated emissions.
Designers resolve these issues by using differential signaling and galvanic isolation.
Impedance Separation
Common ground planes often carry currents from both power supplies and high-frequency digital signals. When ground loop harmonic emission occurs, it introduces voltage fluctuations that degrade the signal-to-noise ratio of the receiver. This degradation can lead to data transmission errors.
Measurement Technique
Spectrum analyzers connected to the ground reference point capture these unwanted signals during laboratory evaluations. The engineers isolate ground loop harmonic emission by measuring the currents on the shield of the interface cables. These readings are compared to the limits set by electromagnetic compatibility standards.
Isolation Strategy
Optocouplers and digital isolators are employed to break the conductive path between different circuit blocks. By preventing ground loop harmonic emission, these components ensure that the reference ground remains clean and stable. This design choice is critical for passing system-level certification tests.