What is the adjacent channel leakage ratio requirement for a 5G NR base station transmitter?

What is the adjacent channel leakage ratio requirement for a 5G NR base station transmitter? The Adjacent Channel Leakage Ratio (ACLR) measures the out-of-band emissions from the transmitter into adjacent frequency channels, and it is one of the most critical PA linearity specifications for 5G NR: (1) ACLR definition: ACLR = P_carrier / P_adjacent (in dB). Where P_carrier is the power in the desired channel bandwidth and P_adjacent is the power leaked into the adjacent channel of the same bandwidth. The ACLR is measured at the antenna port (after filtering). (2) 3GPP requirements (TS 38.104): for NR base stations (BS): ACLR ≥ 45 dB for E-UTRA and NR adjacent channels. This applies at the first and second adjacent channel offsets. For the first adjacent channel: the center frequency offset = channel_BW (e.g., 100 MHz for a 100 MHz NR carrier). For the second adjacent channel: offset = 2 × channel_BW. (3) System ACLR budget: the 45 dB requirement is at the antenna port (after all filtering). The PA alone must provide approximately 35-40 dB ACLR before filtering. The output filter provides an additional 5-15 dB of adjacent channel rejection. With DPD: the PA ACLR is improved by 10-15 dB (from 30-35 dB raw to 45-50 dB with DPD). This allows the PA to operate closer to compression (higher output power and efficiency) while still meeting the 45 dB ACLR requirement. (4) ACLR vs power: as the PA output power increases toward P1dB, the ACLR degrades (more nonlinear distortion). The maximum operating power is typically set where ACLR = 50-55 dB (providing 5-10 dB margin above the 45 dB requirement). For a Doherty PA with DPD: the maximum operating power is approximately 3-5 dB below P1dB while maintaining ACLR ≥ 50 dB.