Pulse to digital detection circuit

摘要

A circuit relies on the natural time constant presented to a pulse input signal which drops the signal level to a very low value “zero state,” less than 0.1 percent of the peak value, before the next pulse arrives. The signal is amplified with a low-noise, wideband, AC-coupled amplifier and split into two equal signals. One of the signals is delayed relative to the other by a fraction of the repetition period and then both signals are input to separate very wideband track-and-hold circuits. Output signals from the track-and-hold circuits are amplified, subtracted and applied to the input of an analog-to-digital converter. The track-and-hold circuits are clocked in such a way that one track-and-hold holds the value at the peak of the signal and the other track-and-hold holds the value at the baseline of the signal, the point when the signal has decayed to the zero state.

主权项

1. A data communication apparatus comprising:
a photodiode configured to convert a light pulse to an electrical signal; a balun configured to split the electrical signal into a first electrical signal and a second electrical signal; an electronic delay to delay the first electrical signal by a duration greater than or equal to an amount of time necessary for the electrical signal to decay to a voltage value corresponding to a least significant bit; a first track-and-hold element connected to the delay, configured to sample the first electrical signal; a first analog-to-digital converter connected to the first track-and-hold element, configured to measure and digitize a first sampled electrical signal with reference to a first reference voltage; a second track-and-hold element configured to sample the second electrical signal of the two electrical signals; a second analog-to-digital converter connected to the second track-and-hold element, configured to measure and digitize a second sampled electrical signal with reference to a second reference voltage; and a processor configured to convert a signal corresponding to a voltage difference between the first electrical signal and the second electrical signal into a digital output, wherein the first analog to digital converter and the second analog to digital converter are connected to the processor.