Difference between real and complex impulse responses?
Your question might be the result of a misunderstanding. There is only one type of impulse response, and this is a system's response to a Dirac impulse $\delta(t)$ (in continuous time), or - in discrete time - to a discrete impulse $\delta(n)$. For a real-valued system, i.e. a system with real-valued parameters, the impulse response is always real-valued. For a complex-valued system, i.e. a system with complex-valued parameters (e.g. complex-valued filter coefficients), the impulse response is complex-valued. Note, however, that complex-valued systems are just a convenient way to describe certain real systems, just like complex numbers are often more convenient to establish certain mathematical results.