  A family of quaternary sequences over Z4 is defined based on the
Ding-Helleseth generalized cyclotomic classes modulo pq for two distinct odd
primes p and q. The linear complexity is determined by computing the defining
polynomial of the sequences, which is in fact connected with the discrete
Fourier transform of the sequences. The results show that the sequences possess
large linear complexity and are good sequences from the viewpoint of
cryptography.
