What is IFBW?
IFBW (Intermediate Frequency Bandwidth) is the bandwidth of the filter applied at the intermediate frequency (IF) stage in a superheterodyne receiver or test instrument. It determines the selectivity and sensitivity of the measurement system — narrower IFBW provides better sensitivity and frequency resolution but requires longer measurement time, while wider IFBW enables faster measurements with less frequency selectivity. IFBW is a critical parameter in spectrum analyser and network analyser configurations for 5G NR testing.
How Does IFBW Work?
In a superheterodyne receiver (used in most spectrum and signal analysers), the incoming RF signal is mixed down to a lower intermediate frequency where it passes through a bandpass filter — the IF filter. The bandwidth of this filter is the IFBW. A narrower IFBW rejects more noise, lowering the instrument’s noise floor and improving the ability to detect weak signals. However, the measurement sweep time is inversely proportional to IFBW² (for swept analysis), so narrowing IFBW significantly increases measurement time. For 5G NR measurements, IFBW is set based on the specific measurement: narrow for spurious emission searches, moderate for ACLR, and wide for EVM measurements.
Use Cases
Spectrum analyser configuration for 5G NR emissions testing, network analyser measurement setup, receiver sensitivity measurements, spurious emission search with maximum sensitivity, and EMC compliance testing.
3GPP / Standards Reference
ITU-R SM.1541 (Unwanted emissions measurement), 3GPP TS 38.104 (NR BS radio measurement methodologies)
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
