调制信号PAR的疑问

如果两个等幅度不同频率的信号相加，那么其能量峰均值比PER=2，这个容易理解
看书有这句话有点疑问
"If there are n carriers in a given operating bandwidth, it is easy to
see that the theoretical maximum peak-to-average power ratio will be
sqrt(n). As n increases, however, the chances of a random in-phase
alignment becomes much lower so that in the limit such signals, or signal
combinations, tend toward behaving like noise. Gaussian noise has a
peak-to-average power ratio of about 9dB, so very dense multicarrier systems
might require about 6dB more power backoff to achieve a similar level of IM
distortion compared to a two-charrier signal having the same power."
1、为什么PER是sqrt(n)而不是n?
2、为什么Gaussian noise的PER就是约为9dB?

应该是写错了，都只是幅度为sqrt(N)，这个应该没错
可是后面那个Gaussian 的PAR=9dB实在是不明白了
比如CDMA的调制输出是不是就算是类似于高斯白噪声? PAR就是9dB左右吗?