AbstractAlthough differential detection methods having superior fading resistance and, in general are effective in digital land mobile communications systems, phase shifts due to frequency offsets become a major factor that deteriorates the error rate in these differential detection methods. Although various frequency‐offset compensating methods have been studied and developed, the maximum amount of frequency offset that can be compensated is limited due to the ambiguity of the phase, which has become a problem in estimating the phase shift due to a frequency offset.In this paper, a method for compensating frequency offset by double differential encoding of transmission data sequences, which allows a resolution of the forementioned problem even when a large frequency offset occurs, is proposed and the error rate performance in the application of a /4‐shift QPSK scheme is evaluated by computer simulation. As a result, it is shown that the proposed method has superior compensating performance on land mobile communications channels.