How can I detect the peak amplitudes of 100 kHz nanosecond (30 ns) pulses?

Dear all,

My goal is to digitize an analog signal and measure (capture) the maximum peak heights of each pulse. Then, I will analyze each data in a computer-based process. The analog signal has the frequency (pulse-repetition-rate) of f = 100 kHz. Furthermore, it consists of short pulses that exhibit pulse durations around ~30 ns. In addition, peak voltages of the pulses are not constant and change in time. (There are some time jitters also.) The illustration of the signal is in the attachment.


(Note: Actually, the pulses are not rectangle-shaped. They have the form of a Gaussian pulse.) 
The problem is that comparing to the time period of the signal, pulse durations are very short. So, I think that it is a real challenge to accurately capture the each pulse and detect their peak voltages via an ADC component. I don't know which ADC meet my requirements to detect pulse amplitudes, since I couldn't decide the required sampling rate and bandwidth of ADC.

I don't want to use GSPS-ADCs, since their prices are really high. Can I use kSPS range ADCs to capture pulse peaks? (e.g. only one sample for one pulse) I think this method requires the accurate synchronization of ADC clock to analog signal, am I right?

Can you give me some design advice to chose a proper method to digitize such a signal?
Thanks in advance.

What sort of amplitude variation are you expecting, and what sort of accuracy are you needing. It may be that a high speed peak detector would do it, which is an analogue solution. There is quite a bit of information on the web if you do a search. Once the signal is held, you can then sample it with an ADC, after the signal is converted you then reset the peak detector. With your repetition rate you will need an ADC that can convert at somewhat less than the repetition rate of the pulse, but you are only talking about a few mega samples/sec.Cheers,Richard

Utku,I saw this post a couple of days ago while at work and have been mulling over how I'd do it. Your requirements are pretty stiff, but not unachievable.  At the pulse level, you want to amplify your pulses so that the maximum peak level you'll get is a bit less than the sensitivity of your ADC.  At 30ns pulse length this implies an amplifier with a response of greater than 30 MHZ.  Not unachievable if you don't need much amplification, but I'd want a bandwidth of 100MHz or more for this.  Make the amplifier a peak detector too (output feeding a (fast) diode into a capacitor, with feedback after the capacitor).   Detect a peak (comparator) and trigger your ADC with that.  You'd need a fast (but not superfast) ADC.  Then, as Richard says, reset your peak detector (discharge the cap) - you could do that fairly easily if the ADC gives you some kind of end of conversion signal.   Then just read your ADC and wait for the next pulse.  Your max ADC conversion time would need to be a bit less than the pulse repetition rate (to allow for jitter).You'd probably get away with a 1MSPS ADC or even a bit less.Doesn't sound toooo difficult but you'd need good components around the front end to get accurate results.  A bit more information about the pulses would help (max / min amplitudes, widths and timing jitter).