  Millimeter wave MIMO combines the benefits of compact antenna arrays with a
large number of elements and massive bandwidths, so that fully digital
beamforming has the potential of supporting a large number of simultaneous
users with {\it per user} data rates of multiple gigabits/sec (Gbps). In this
paper, we develop an analytical model for the impact of nonlinearities in such
a system, and illustrate its utility in providing hardware design guidelines
regarding two key challenges: the low available precision of analog-to-digital
conversion at high sampling rates, and nonlinearities in ultra-high speed radio
frequency (RF) and baseband circuits. We consider linear minimum mean square
error (LMMSE) reception for a multiuser MIMO uplink, and provide performance
guarantees based on two key concepts: (a) summarization of the impact of
per-antenna nonlinearities via a quantity that we term the "intrinsic SNR", (b)
using linear MMSE performance in an ideal system without nonlinearities to
bound that in our non-ideal system. For our numerical results, we employ
nominal parameters corresponding to outdoor picocells operating at a carrier
frequency of 140 GHz, with a data rate of 10 Gbps per user.
