W-CDMA Adjacent Channel Leakage Power Ratio (ACLR) Measurements

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One of the most important measurements on RF signals for digital communication systems is the leakage power into the adjacent channels. A quantitative figure of merit is adjacent channel power ratio (ACPR) or adjacent channel leakage ratio (ACLR). The ACLR measurement determines how much of the transmitted power is allowed to leak into the first and second neighboring carriers (high side and low side). Leakage of RF power into adjacent channels or bands can cause major interference to occur on another carrier's network.
The measurement of ACLR is defined as the ratio of the average power in the adjacent frequency channel to the average power in the transmitted frequency channel. It is reported in dBc (dB relative to the main carrier).
Test models are used to have pre-defined test conditions for base station conformance test of ACLR. Under 3GPP TS 25.141, five types of test models are defined. Each test model consists of PCCPCH (Primary Common Control Physical Channel), PICH (Paging Indication Channel), CPICH (Common Pilot Channel), SCH (Synchronization Channel) and some DPCHs (Dedicated Physical Channels).

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NOTE:

The 3GPP TS 25.141 standard for W-CDMA requires the adjacent channel power leakage ratio to be better than -44.2 dBc at 5 MHz offset and -49.2 dBc at 10 MHz offset. The minimum requirements for the adjacent channel power leakage ratios are -45 dBc and -50 dBc respectively, but the conformance test requirements add 0.8 dB tolerance to these figures. The conformance limits are consequently -44.2 dBc at 5 MHz offset and -49.2 dBc at 10 MHz offset.

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