pulse generator with srd
Sorry, you are right. They DO have that useless circuit shown in AN918.
I am going to suggest that you completely ignore it, as it will not work.
Start off with this paper:
http://www.hp.woodshot.com/hprfhelp/5_downld/lit/diodelit/an984.pdf
On the top page you will see a current waveform that makes a sudden change vs time. This is due to the nature of the diode. A normal diode, like a shottky diode, conducts current only when the diode is forward biased. So if you apply a sine wave input voltage to a schottky diode (mounted in shunt, cathode to ground) you will get a half sinewave output voltage waveform for the positive voltage input, and a zero volt out signal when the input voltage sinewave tries to go negative. In other words, the schottky diode immediately clamps any negative going voltage.
A step recovery diode is specially designed so that it can sometimes conduct current for voltage applied in either direction. The do this by making a PN junction diode, but between the P and N materials, they leave a relatively thick Intrinsicly doped region where electrons can drift around. So if you apply a positive half of a sine wave voltage across that diode, it conducts current like a normal diode. BUT if you apply a negative going half sine wave, the electric field in the diode switches polarity immediately, but there are a boat load of electrons floating around in the I region. As the electric field in the diode gets stronger, it accelerates those electrons back to the annode, but then all of a sudden the last free electron is absorbed at the annode, there are not more electrons in the I region, and the big reverse current suddenly goes to zero and stays there.
Now that in intself is not that interesting. But if you were driving the input sinewave into the diode through a significant inductance, then when the reverse flowing current coming out of the I region suddenly goes to zero, the magnetic field in the inductor collapses and causes a hughe voltage spike to occur. That voltage spike is very short lived, and very high (tens of volts).
So what you need, as a bare minimum, is a step recovery diode driven by a big sine wave voltage source through an appropriately sized chip inductor. That is a good start.
The other elements in an actual comb/impulse generator are there to do an input match. Look for comb generator or impulse generator papers, like this one. Unfortunately, al lot of the early papers seem to now be locked up at the IEEE Iexplore site, were you need a membership to read them!
Also, be aware that the diode characteristics have a lot to do with the pulse shape, like diode capacitance, carrier lifetime, transiston time.
http://www.medphys.ucl.ac.uk/resear.../phd/chapter5.pdf#search="srd comb generator"
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And here is the ONLY decent copy of the type of circuit you should really be using for the input to SRD impulse generator. Unfortunately the output part of this circuit was designed as a freqeuncy multiplier (one output frequency only, so their circuit is a bandpass). You want to ignore the output matching network and output filter and just put a DC blocking capacitor in series to the right of the SRD:
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