I'm a newbie on SDR. I want to design the following device and after examining several solutions, including 600MHz microcontrollers, FPGAs, high speed ADCs and dual-ported RAMs, I came across GNU Radio and its delay() block. That is what made me explore SDR as a means to my solution...

I need to realize an signal delay line as described below:
1. I have a say 300 microsecond long pulse stream with a variable amplitude of between +/- 1V, with a pulse width of around 1 microsecond.
2. I want to delay this pulse stream by a discrete amount of time, varying between 200 and 400 microseconds.
3. After the selected delay, I need to reconstruct and output the stream as it was.
4. The pulse stream is not continuous. It lasts say 200, 300 or 400 microseconds and comes on again after a certain period.
5. A 20 MHz sampling rate, yielding 20 samples per microsecond pulse, should be enough to reconstruct the sampled pulse stream.

From what I have read and seen of GNU Radio, I would need a full-duplex transmit-capable SDR and I'm inclined to favour the Analog Devices PlutoSDR, primarily for its full-duplex Rx/Tx capability and very low price. Problem is, I don't even know where to begin!

Can someone hold my hand and guide me through a GNU Radio flowgraph?

Thank you in advance...

- Tango