CHARACTERIZATION OF IN-BUILDING UHF WIRELESS RADIO-COMMUNICATION CHANNELS USING SPECTRAL ENERGY MEASUREMENTS

A simple, cost-effective means is developed to estimate the time-invar iant wireless radio channel impulse response h(t) using only the magni tude of the channel transfer function, H(jw). The Hilbert transform is used to calculate the phase of H(jw) from its magnitude, Inverse disc rete Fourier transformation (IDFT) of H(jw) yields h(t). The Hilbert t ransform relation is applicable provided H(jw) is a minimum phase tran sfer function, An experimental in-building wireless channel testbed wa s established, for which h(t) was determined over the 1000-2500 MHz ra nge, Both line of sight (LOS) and non-LOS transmission was investigate d, Good agreement was observed between values of h(t) calculated from measured values of H(jw) and from those based only on \H(jw)\ and its Hilbert transform, Even when the minimum phase condition is violated, h(t) as calculated from \H(jw)\ and its Hilbert transform provides a u seful lower bound on the time-spread of h(t). The measurement of \H(jw )\ is easily implemented using a signal source, receiving antenna, and spectrum analyzer, A personal computer and software are required to c alculate the phase of H(jw) and its IDTF, Existing frequency-domain me asurement schemes utilize a vector network analyzer to measure H(jw) ( magnitude and phase angle), Such equipment is expensive, subject to tr ansmitter-receiver crosstalk, and restrictive as to the relative locat ions of the transmitting and receiving antenna.