Quadrature slow-time MIMO radar with experimental results

Multiple-input multiple-output (MIMO) radar requires orthogonal waveforms to be transmitted on each transmit element or subarray. One practical problem that arises is the complexity and expense of the hardware needed to implement MIMO radar. Slow-time MIMO waveforms, often referred to as SLO-MO waveforms, allow the implementation of MIMO radar without any hardware modifications to the receiver. However, generation of the SLO-MO MIMO waveforms on the transmitter typically requires a multichannel arbitrary waveform generator, variable RF phase shifters, or using multiple carrier frequencies. All of these options can be expensive, especially at microwave frequencies. This paper describes a technique to generate SLO-MO MIMO waveforms using low-cost passive frequency mixers with existing (non-MIMO) radar architectures. Passive frequency mixers are inexpensive and easy to add inline to existing radar transmitters. This paper presents the concept of double-sideband and quadrature MIMO slow-time radar, along with experimental results from the Duke S-band radar testbed.