Also, in the paper they say they used pulse-width modulation for the backscatter signal instead of just attaching the sensors directly to the antenna like the Great Seal Bug because the dynamic range of the photodiodes is much less than that of a microphone and they wanted to avoid using an amplifier (section 3.1 in the paper). But the PWM requires power as well. Would an amplifier that only has to map the range of a photodiode to the range of a microphone really require that much more power? And if so, are we talking like twice the power, 10x, 100x?