Interplay between coding theory and combinatorial t-designs has been a hot
topic for many years for combinatorialists and coding theorists. Some infinite
families of cyclic codes supporting infinite families of 3-designs have been
constructed in the past 50 years. However, no infinite family of negacyclic
codes supporting an infinite family of 3-designs has been reported in the
literature. This is the main motivation of this paper. Let q=pm, where p
is an odd prime and m≥2 is an integer. The objective of this paper is to
present an infinite family of cyclic codes over \gf(q) supporting an infinite
family of 3-designs and two infinite families of negacyclic codes over
\gf(q^2) supporting two infinite families of 3-designs. The parameters and
the weight distributions of these codes are determined. The subfield subcodes
of these negacyclic codes over \gf(q) are studied. Three infinite families of
almost MDS codes are also presented. A constacyclic code over GF(4)
supporting a 4-design and six open problems are also presented in this paper