In this work we investigate the weight structure of cyclic codes of composite length n = n1n2, where n1 and n2 are relatively prime. The actual minimum distances of some classes of binary cyclic codes of composite length are derived. For other classes new lower bounds on the minimum distance are obtained. These new lower bounds improve on the BCH bound for a considerable number of binary cyclic codes.
Hartmann, Carlos R.P. and Hwang, T. Y., "Some Results on the Weight Structure of Cyclic Codes of Composite Length" (1975). Electrical Engineering and Computer Science Technical Reports. Paper 16.