  Accurate channel parameter estimation is challenging for wideband
millimeter-wave (mmWave) large-scale hybrid arrays, due to beam squint and much
fewer radio frequency (RF) chains than antennas. This paper presents a novel
joint delay and angle estimation approach for wideband mmWave fully-connected
hybrid uniform cylindrical arrays. We first design a new hybrid beamformer to
reduce the dimension of received signals on the horizontal plane by exploiting
the convergence of the Bessel function, and to reduce the active beams in the
vertical direction through preselection. The important recurrence relationship
of the received signals needed for subspace-based angle and delay estimation is
preserved, even with substantially fewer RF chains than antennas. Then, linear
interpolation is generalized to reconstruct the received signals of the hybrid
beamformer, so that the signals can be coherently combined across the whole
band to suppress the beam squint. As a result, efficient subspace-based
algorithm algorithms can be developed to estimate the angles and delays of
multipath components. The estimated delays and angles are further matched and
correctly associated with different paths in the presence of non-negligible
noises, by putting forth perturbation operations. Simulations show that the
proposed approach can approach the Cram\'{e}r-Rao lower bound (CRLB) of the
estimation with a significantly lower computational complexity than existing
techniques.
