  For millimeter wave (mmWave) or Terahertz (THz) communications, by leveraging
the high spatial resolution offered by large antenna arrays and the multi-path
sparsity of mmWave/THz channels, a novel inter-symbol interference (ISI)
mitigation technique called delay alignment modulation (DAM) has been recently
proposed. The key ideas of DAM are delay pre-compensation and path-based
beamforming. However, existing research on DAM is based on fully digital
beamforming, where the number of radio frequency (RF) chains required is equal
to the number of antennas. This leads to high hardware cost and power
consumption for mmWave/THz massive multiple-input multiple-output (MIMO)
communications. Thus, this paper proposes the hybrid analog/digital beamforming
based DAM. The analog and digital beamforming matrices are designed to achieve
performance close to DAM based on fully digital beamforming. The effectiveness
of the proposed technique is verified by simulation results.
