Frequency division orthogonal waveforms for narrowband MIMO arrays

Multiple-Input Multiple-Output arrays with closely spaced antennas typically utilize orthogonal waveforms to create a larger virtual aperture. Orthogonality between waveforms can be achieved using time, Doppler, coding, or frequency division. In this work we examine the method of generating frequency diverse waveforms. In general, the frequency division approach generates waveforms that have reduced bandwidth which results in reduced range resolution. To overcome this loss of range resolution more spectrum must be utilized which might not be compatible with narrowband arrays. Herein, we present an approach for generating a notched waveform set that preserves range resolution, is effectively orthogonal, and could be utilized by narrowband arrays.