Transmit Power

Definition

The transmitter peak or average power output measurement is made over an interval of time. This time is equal to the frame rate or transmission burst of the device under all conditions of modulation expressed in milliwatts.

Standards

• IEEE Std 802.11b-1999 Paragraph 18.4.7.1, 18.4.7.2 Transmit power levels and Power level control
• IEEE Std 802.11a-1999 Paragraph 17.3.9.1 Transmit power levels
• ANSI/IEEE Std 802.11 First edition 1999-00-00 Paragraph 15.4.7.1, 15.4.7.3 Transmit power levels and power level control
• FCC Title 47 Code of Federal Regulations Part 15 (47 CFR 15)

Measurement Subtleties

If not controlled, many transmitter parameters can reduce the performance of WLAN systems, or even prevent RF devices from working together. Transmit power levels directly affect the transmit range. Excess power may cause interference with other transmissions, or greatly shorten battery life unnecessarily in portable applications.

The 802.11 standard does not specify a tolerance limit for the impedance of the antenna ports or the frequency range to be tested.

The test limits vary depending on the frequency band and specification standard.

Test Tools

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 as standalone. This provides vector signal analysis up to 6 GHz, with one or two channel inputs, for IQ, IF, and RF measurements.

The 89607A WLAN test suite software comes pre-programmed with the IEEE802.11a/b/g transmitter performance specifications for automated control of the 89600 Series vector signal analyzer. The PSA and ESA spectrum analyzers offer traditional power measurements and also a choice of peak and average detection. 

Related Measurements

• Transmit Spectrum Mask
• Complementary cumulative distribution function (CCDF)