What is ACPR?

Adjacent Channel Power Ratio ?!

ACPR include LACPR and UACPR

ACPR (Adjacent Channel Power Ratio) or sometimes named ACLR (Adjacent Channel Leakage power Ratio), is the ratio of the filtered mean power centered on the assigned frequency to the filtered mean power centered on the adjacent channel frequency.

It is widely used in OFDM communication such as 802.11a, 802.11g and WiMAX.
Because OFDM signal carriers are densely spaced one by one, to avoid adjacent carrier power interferencing others ACPR need to be regulated.

ACPR (or also aka ACLR: Adjacent Channel Leakage Ratio) is known simply as the ratio of the main channel power to the next adjacent channel power. It is a good figure of merit to measure the quality of the main channel out from the effects of adjacent channels. It is defined for W-CDMA signals (e.g. UMTS). One of the most important reasons for leakage from adjacent channels is the nonlineartiy of the power amplifier used in transmitters. There are some standards expressed by ITU. For example for a 5 MHz BW UMTS signal ACLR value should be bigger than 45 dB, whereas for 10 MHz BW signal is 50 dB.

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Is there a reason that for standards with higher baseband bandwidth, it is harder to achieve better ACPR? Or actually, for standards with higher baseband bandwidth, it is easier to achieve better ACPR ( in the sense that -70dB is better than -40dB)?