How does the modulation bandwidth of Wi-Fi 7 at 320 MHz affect the PA linearity requirement?

How does the modulation bandwidth of Wi-Fi 7 at 320 MHz affect the PA linearity requirement? Wi-Fi 7 doubles the maximum channel bandwidth from 160 MHz (Wi-Fi 6) to 320 MHz, which significantly increases the demands on PA linearity: (1) Why wider bandwidth demands more linearity: PAPR increases with wider bandwidth because more OFDM subcarriers contribute to the peak power. The PAPR at 320 MHz is approximately 0.5-1 dB higher than at 160 MHz. The PA must handle this higher PAPR without clipping, requiring more backoff from P1dB. Memory effects: at wider bandwidths, the PA memory effects (thermal memory, bias circuit memory, and trapping effects) become more pronounced. These effects cause the PA response to depend not only on the current input signal but also on recent past inputs. Memory effects degrade EVM and ACLR and are harder to correct with static DPD. (2) Bandwidth-dependent linearity metrics: EVM: the EVM requirement does not change with bandwidth (it is per-subcarrier). However: achieving the same EVM at 320 MHz is harder because the PA must be linear across a wider frequency range (amplitude and phase flatness). ACLR/spectral mask: the out-of-band emissions must meet the spectral mask at the band edges. At 320 MHz, the energy in the spectral sidelobes is spread over a wider bandwidth, requiring the PA to be linear across the entire 320 MHz. The spectral mask is typically -20 dBr at the channel edge and -28 dBr at ±160 MHz from the center. (3) PA design impact: to meet the linearity requirement at 320 MHz: the PA OBO (output back-off) from P1dB must increase by 1-2 dB compared to 160 MHz. For a PA with +20 dBm P1dB: at 160 MHz (1024QAM): max linear Pout ≈ +16-17 dBm. At 320 MHz (4096QAM): max linear Pout ≈ +14-15 dBm. The PAE (power-added efficiency) drops significantly: from approximately 20-25% (160 MHz) to approximately 12-18% (320 MHz). DPD (Digital Pre-Distortion): AP-class devices use DPD to compensate for PA nonlinearity. At 320 MHz: the DPD observation bandwidth must be 3-5× the signal bandwidth = 960-1600 MHz. This requires a very wideband feedback receiver (ADC sampling rate > 2 GHz). The DPD model must include memory terms (memory polynomial or Volterra series) to capture bandwidth-dependent effects.