  Multiple-input multiple-output (MIMO) radar is a relatively new concept in
the field of radar signal processing. Many novel MIMO radar waveforms have been
developed by considering various performance metrics and constraints. In this
paper, we show that finite alphabet constant-envelope (FACE) quadrature-pulse
shift keying (QPSK) waveforms can be designed to realize a given covariance
matrix by transforming a constrained nonlinear optimization problem into an
unconstrained nonlinear optimization problem. In addition, we design QPSK
waveforms in a way that they don't cause interference to a cellular system, by
steering nulls towards a selected base station (BS). The BS is selected
according to our algorithm which guarantees minimum degradation in radar
performance due to null space projection (NSP) of radar waveforms. We design
QPSK waveforms with spectrum sharing constraints for a stationary and moving
radar platform. We show that the waveform designed for stationary MIMO radar
matches the desired beampattern closely, when the number of BS antennas
$N^{\text{BS}}$ is considerably less than the number of radar antennas $M$, due
to quasi-static interference channel. However, for moving radar the difference
between designed and desired waveforms is larger than stationary radar, due to
rapidly changing channel.
