It will be great if someone can explain me what exactly means "real impulse response". Further more , what is the effect of such a response on ROC (Laplace plane) and in particular if its restrict the possible area of the poles and zeros? Thanks
real impulse response
effect of such a response on ROC
nothing specific, since realness doesn't imply any kind of stability/convergence, far as I can tell. It does tell you something about poles and zeros always appearing in conjugate pairs, but that's it.
restrict the possible area of the poles and zeros