Excitation signals are a primary key for an accurate and fast bioimpedance measurement within a frequency range from 5 kHz to 1 MHz. In this paper, several signals for bio-impedance spectroscopy are compared, in term of frequency distribution and average Discrete Fourier Transform (DFT) peak value, with a reference to the execution time used to maintain the frequency resolution, the latter being manifested as a frequency vector length. The sine-sweep and binary-sweep both share an advantageous high energy distribution, the latter, albeit higher, suffers from power spectrum ratio waste due to the undesired harmonics. For less execution time, binary chirp has a good frequency distribution and a higher average DFT peak, hence energy distribution, with a main drawback of an average useful power spectrum ratio.