A spectrum analyzer’s EMI (Electromagnetic Interference) bandwidth setting refers to specific resolution bandwidth (RBW) filters that are used during measurements to comply with electromagnetic compatibility (EMC) testing standards.
These settings are used to assess the amount of electromagnetic interference produced by different devices and ensuring they meet regulatory standards.
Key Points About EMI Bandwidth Settings:
- Purpose of EMI Filters: In spectrum analysis for EMI testing, the bandwidth of the RBW filter significantly impacts the measurement’s accuracy and compliance with regulatory requirements. The filter settings determine how finely the spectrum analyzer can resolve different frequencies, affecting its ability to accurately measure signal power at various frequencies.
- Standardization: EMI bandwidth settings are often standardized according to international regulatory requirements, such as those set by the CISPR (International Special Committee on Radio Interference), the FCC (Federal Communications Commission) in the U.S., or the IEC (International Electrotechnical Commission). These standards specify the bandwidths for measurements to ensure consistency across tests and comparability of results.
- Common Bandwidths: Typical EMI bandwidth settings include 200 Hz, 9 kHz, 120 kHz, and 1 MHz. Each of these bandwidths is chosen based on the frequency range being tested and the specific details of the regulatory standard being followed. For example: 200 Hz and 9 kHz are commonly used for lower frequency ranges. 120 kHz and 1 MHz might be used for higher frequency ranges.
- Quasi-Peak and Average Detectors: Spectrum analyzers used in EMI testing often come with different types of detectors, such as quasi-peak detectors, which are used to simulate the averaging effects of human exposure to RF energy, and average detectors, which measure the average energy of the signal. The bandwidth settings play a critical role in how these detectors function and their compliance with EMI standards.
- Impact on Measurement: Using the correct EMI bandwidth setting is crucial because it influences the measurement’s sensitivity and selectivity. A narrower bandwidth can detect smaller signals but will have a longer sweep time, whereas a wider bandwidth can sweep faster but might miss smaller signals.
When setting up a spectrum analyzer for EMI testing, it’s important to configure these bandwidth settings according to the specific standards applicable to the device being tested.
This ensures that the measurements are both accurate and compliant with international regulatory standards, which is essential for product certification and market approval.
