Transmit and Receive In-Band and Out-of-Band Spurious Emissions

Definition

Spurious emissions are unwanted emissions, emanating from the equipment under test. The frequency bands (in-band and out-of-band) and their corresponding spurious emission limits are specified by regulatory agencies such as the Federal Communications Commission (FCC) in the United States and ETSI in Europe.

Standards

• IEEE Std 802.11b-1999 16 September 1999 Paragraph 18.4.6.8 Transmit and receive in-band and out-of-band spurious emissions
• IEEE Std 802.11a-1999 16 September 1999 Paragraph 17.3.8.4 Transmit and receive in-band and out-of-band spurious emissions
• ANSI/IEEE Std 802.11 First edition 1999-00-00 Paragraph 15.4.6.5 Transmit and receive in-band and out-of-band spurious emissions
• FCC CFR47 15.205 - Restricted bands of operation
• FCC CFR47 15.209 - Radiated emission limits; general requirements
• FCC CFR47 15.247 - Operation within the bands 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz
• FCC CFR47 15.407 - General technical requirements
• ETS 300-328

Measurement Subtleties

Some spurious emissions limits are based on using a quasi-peak detector. Not all spectrum analyzers have this type of detector. You could use a peak detector during product evaluation because it gives results that are equal to or higher than a quasi-peak detection.

Test Tools

During product development, you will find that the ESA and PSA Series spectrum analyzers are useful tools for measuring and finding sources of spurious emissions. Both spectrum analyzer series have built-in one-button spurious emissions measurement capability.

The frequency range of the spectrum analyzer is a very important factor for out-of-band spurious emissions coverage. The ESA Series has a limit of 26.5 GHz, and the PSA has a limit of 50 GHz.

For those wanting in-house precompliance testing capability Keysight offers several systems based on the E7400A Series EMC analyzers.