请问下这段关于插损的话

其实内容应该是很简单的，因为我是入门级。
Isolation
Isolation is a measure of the insertion loss between a pair of mixer ports. The most important and often specified terms are the LO to IF and LO to RF isolation. The higher power level of the LO signal can create problems if this signal leaks through the mixer and out to the RF or IF port. For example, if the RF input signal has a level of -10 dBm, and with a mixer conversion loss of 6dB, the IF signal level is -16dBm. If the applied LO signal level is +10dBm and the L-to-I isolation is -20 dB, then the LO signal appearing at the IF port is -10 dBm which is 6dB higher than the desired LO signal. This higher LO signal will need to be properly filtered out of the IF signal path.
我在 6dB higer than the desired LO signal 这里不是很明白。为什么是desired？这个6是怎么来的呢？ 是-10和-16的差距么？ 那么 -16是LO desired的？ 谢谢了
这是我理解的图：    R (-10) ------(6 loss)  I    (-10-6=-16)
                                           /  (10-20=-10)
                                          / -20 leakage
                                         /
                                        /
                                     L (10)

写错了呗，应该是desired if signal