What is the successive detection logarithmic receiver and how does it achieve wide dynamic range?

The successive detection logarithmic (SDL) receiver achieves wide dynamic range by using a cascade of limiting amplifiers, each followed by a detector, whose outputs are summed to produce a video output proportional to the logarithm of the input signal power. The SDL receiver achieves 60-90 dB of instantaneous dynamic range without AGC because each detector in the chain responds to a different portion of the input power range: the first detector (at the end of the amplifier chain) responds to the weakest signals (which have been amplified by all stages), and the last detector (at the input) responds to the strongest signals (which saturate all the amplifier stages). The total output is the sum of all detector outputs, and because each stage adds a fixed increment of detection for each fixed increment of input power (in dB), the summation produces a logarithmic transfer function. The SDL receiver operation: for a weak input signal (-80 dBm): the signal is amplified through all 8 stages (total gain approximately 80-100 dB) to a level where only the last 1-2 detectors respond. Output voltage: low. For a moderate input signal (-40 dBm): the signal saturates the last 4-5 stages but is detected by all 8 detectors. Output voltage: medium. For a strong input signal (0 dBm): the signal saturates all 8 stages, and all 8 detectors produce maximum output. Output voltage: high. The result is a monotonic, approximately logarithmic relationship between input power and output voltage across the 80-90 dB range.