  As radio-frequency (RF) antenna, component and processing capabilities
increase, the ability to perform multiple RF system functions from a common
aperture is being realized. Conducting both radar and communications from the
same system is potentially useful in vehicular, health monitoring, and
surveillance settings. This paper considers multiple-input-multiple-output
(MIMO) dual-function radar-communication (DFRC) systems in which the radar and
communication modes use distinct baseband waveforms. A transmit precoder
provides spatial multiplexing and power allocation among the radar and
communication modes. Multiple precoder design approaches are introduced for a
radar detection mode in which a total search volume is divided into dwells to
be searched sequentially. The approaches are designed to enforce a reliance on
radar waveforms for sensing purposes, yielding improved approximation of
desired ambiguity functions over prior methods found in the literature. The
methods are also shown via simulation to enable design flexibility, allowing
for prioritization of either subsystem and specification of a desired level of
radar or communication performance.
