  Hand blockage leads to significant performance impairments at millimeter wave
carrier frequencies. A number of prior works have characterized the loss in
signal strength with the hand using studies with horn antennas and form-factor
user equipments (UEs). However, the impact of the hand on the effective phase
response seen by the antenna elements has not been studied so far. Towards this
goal, we consider a measurement framework that uses a hand phantom holding the
UE in relaxed positions reflective of talk mode, watching videos, and playing
games. We first study the impact of blockage on a directional beam steering
codebook. The tight phase relationship across antenna elements needed to steer
beams leads to a significant performance degradation as the hand surface can
distort the observed amplitudes and phases across the antenna elements, which
cannot be matched by this codebook. To overcome this loss, we propose a
non-directional beamforming codebook made of amplitudes and/or quantized phases
with both these quantities estimated as necessary. Theoretical as well as
numerical studies show that the proposed codebook can de-randomize the phase
distortions induced by the hand and coherently combine the energy across
antenna elements and thus help in mitigating hand blockage losses.
