FIGURE 1 FIGURE 2a OFDM transmit spectrum mask for 802.11a, 11g, 11j, HIPERLAN2 and HiSWANa systems Transmit spectral mask for 20 MHz 802.11n transmission in 2.4 GHz band Power spectral density (dBr) PSD Relative to maximum Transmit spectrum mask (not to scale) 0 dBr –20 dBr 0 dBr Typical signal spectrum (an example) –28 dBr –20 dBr –28 dBr –40 dBr –30 –20 –11 –9 fc 9 11 20 –45 dBr 30 Frequency (MHz) Note 1 – The outer heavy line is the spectrum mask for 802.11a, 11g, 11j, HIPERLAN2 and HiSWANa and the inner thin line is the envelope spectrum of OFDM signals with 52 subcarriers. Note 2 – The measurements shall be made using a 100 kHz resolution bandwidth and a 30 kHz video bandwidth. Note 3 – In the case of the 10 MHz channel spacing in 802.11j, the frequency scale shall be half. Frequency (MHz) –30 –20 –11 –9 9 11 20 30 Note 1 – Maximum of –45 dBr and –53 dBm/MHz at 30 MHz frequency offset and above. M.1450-02 M.1450-01 Regulations for the use of unlicensed spectrum 7