我们正在使用一款 中频子系统芯片 AD9864，
现在已经可以从 SSI 数据输出接口读取到 IQ 数据.
不知道如何根据芯片 SSI 接口输出的 ATT 和 RSSI 数值，计算输入到 AD9864 入口处的实际信号功率大小.
请问 ATT 数值和 RSSI 数值是需要换算成 dB 的？如何换算？
The RSSI is a coarse "linear detector" that measure the ABS(I)+ABS(Q) value of the input signal has shown in figure 58. It is typically used in conjunction with the AGC since its output is compared to the programmable level set in the AGCR field. The RSSI is a 6-bit field (when enabled) in the SSI output data with a value of 60 corresponding to a 0 dBFS sinewave input at IF center ( and -6 dBFS corresponding to a a value of 30).
If the VGA setting is known than it is possible to calculate the real power from the IQ output (within digital passband with higher accuracy) or the RSSI field (wider band with lower accuracy due to 6-bit linear resolution). For example, if its setting was set to 0 dB (i.e. ONLY VGA Enabled in figure 59) than a -32 dBm input signal will result in a -2 dBFS level (defined as IF "clip point") on the I/Q output. Hence 0 dBFS = -30 dBm is my reference point.
If the signal generator was reduced by 4 dB to -36 dBm. I would expect the RSSI field to read closer to 30 since this corresponds to -6 dBFS).
Note that the freqency offset from the IF center also introduces an additional error as shown in figure 60.
Again, the RSSI function is typically used in conjunction with the AGC and only provides a coarse estimate of the signal power over the extended freq range of the 1st stage Dec-12 filter.