Definition

Center frequency leakage is the portion of the transmitter energy that leaks through the transmitter components. This unwanted energy appears in the modulated signal at the signal center frequency.

Standards

  • IEEE Std 802.11b-1999 16 September 1999 Paragraph 18.4.7.7 RF carrier suppression
  • IEEE Std 802.11a-1999 16 September 1999 Paragraph 17.3.6.1 Transmitter center frequency leakage

Measurement Subtleties

In an 802.11a frame, the channel estimation sequence makes the center frequency leakage measurement. In this part of the frame, every 4th carrier is ON which allows you to see the leakage component properly. To isolate this portion of the frame, you will need the time gate function of the 89600. Since the leakage is measured relative to the total signal power, you need other functions such as the band power measurement and the C/N math function.

Test Tools

For 802.11a, time gating is needed in order to isolate that portion of the burst which contains the center carrier. The 802.11a is multicarrier, so using time-gating on the burst allows you to see the center carrier leakage in the frequency domain. The center carrier should be nulled, so any power that shows up at this point is due to leakage. In this case, you can use either the 89600, or the PSA, both of which have the capability for time-gating. For 802.11b no time gating is needed so the measurement can be performed with either the 89600 VSA, the PSA spectrum analyzer, or the ESA spectrum analyzer.

You can use the 89600 Series vector signal analyzer standalone, in conjunction with the ESA-E and PSA series Spectrum analyzers, and with several of Keysight's Infiniium family of oscilloscopes.

You can use the ESA or PSA Series spectrum analyzers as down-converting front ends for the 89600 (with specific options). This provides vector signal analysis capabilities up to 50 GHz. You can also use 89600 hardware as standalone. This provides vector signal analysis up to 6 GHz, with one or two channel inputs, for IQ, IF, and RF measurements.