What is ACPR?
ACPR (Adjacent Channel Power Ratio) is the ratio of the power contained in a specified frequency channel bandwidth relative to the total carrier power. It is a key linearity metric for RF power amplifiers and transmitter chains, indicating how much signal energy spills into adjacent frequency channels due to non-linear distortion. Lower ACPR values indicate better spectral purity and less interference to neighbouring channels.
How Does ACPR Work?
ACPR is calculated by measuring the integrated power in the adjacent channel and dividing it by the integrated power in the main channel. The measurement is performed using a spectrum analyser or vector signal analyser with appropriate resolution bandwidth and channel filter settings. Non-linearities in power amplifiers — such as third-order intermodulation products — are the primary contributors to degraded ACPR. Techniques like digital pre-distortion (DPD) are used to improve ACPR performance.
Use Cases
Power amplifier characterization and linearization, transmitter compliance testing, DPD algorithm validation, 5G NR and LTE base station manufacturing test, and RF component qualification for multi-carrier systems.
3GPP / Standards Reference
3GPP TS 38.104 (NR BS radio transmission and reception), 3GPP TS 36.104 (E-UTRA BS radio transmission and reception)
Related Terms
ACP | ACLR | EVM | PAPR | AM distortion
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