# A practical limitation of an adaptive antenna array using the

# A practical limitation of an adaptive antenna array using the

A practical limitation of an adaptive antenna array using the LMS algorithm is the dynamic range over which the array can operate. This limitation is due to the fact that the speed of response of the weights in the [MS algorithm is proportional to the average signal power at the array input.

(a) Justify the assertion that the dynamic range of average signal power at the array input is proportional to Rb/f max where Rb is the data rate in b/s and f max is the maximum fade rate in Hz.

(b) Assuming a proportionality factor of 0.2, by which the ratio Rb/f max is scaled, calculate the dynamic range of an adaptive antenna array using the LMS algorithm for Rb = 32 kb/s and f max = 70 Hz. Comment on your result. (The proportionality factor of 0.2 is a reasonable choice for systems using PSK.)