Terminology » Difference between IBW vs OBW: Instantaneous Bandwidth & Occupied Bandwidth

Difference between IBW vs OBW: Instantaneous Bandwidth & Occupied Bandwidth

Introduction : In radio and wireless systems, IBW (Instantaneous Bandwidth) and OBW (Occupied Bandwidth) are two critical metrics that define how spectrum is used. While IBW describes the total bandwidth span a radio front end can actively handle at a moment, OBW focuses on how much of that bandwidth is actually used by signal power. This article explains both concepts, the methods for their measurement and significance in system design and their regulatory importance.

What are IBW and OBW?

IBW represents snap-shot of bandwidth of the radio frequency (RF) signal at particular instant. OBW represents bandwidth of RF signal over particular period.

IBW vs OBW Figure-1 : Spectrum Analyzer snap-shot of IBW and OBW

The figure depicts RF device operating in 1.91 to 1.93 GHz frequency range with center frequency at 1.92 GHz. It shows one snap-shot at some instant. IBW shown is about 10 MHz, OBW shown is about 4.1744 MHz.

In summary, Frequency range > IBW > OBW

Key differences

Aspect	IBW	OBW
Definition	The full span of frequencies the radio system can use at a given moment - from lowest to highest frequency component irrespective of transmission is there or not in the spectrum.	The span of frequencies over which signal’s main energy is concentrated (e.g. containing 99% of power). This bandwidth is the spectrum occupied by the actual transmission.
Purpose	Describe capability	Describe actual usage
Relation to power	Does not directly incorporate power distribution	Takes into account power distribution of signal

Conclusion: IBW and OBW may sound similar, but they serve distinct roles. IBW defines capability and hardware limits, whereas OBW captures real signal usage.