This chapter begins with a formulation of the RUWO algorithm in Section 18.2 and its application to producing spatial, frequency, and space-frequency transmit nulls for radio frequency interference avoidance, followed by a description of the Naval Research Laboratory's Space Time Adaptive Nulling (STAN) radar test bed, an eight-channel X-band coherent MIMO radar test bed used to experimentally verify the performance of the RUWO algorithm in Section 18.3. Section 18.4 then provides a description of narrowband loop-back and open-air experimental applications of RUWO that were originally presented in [14,15], respectively. Following the narrowband results is an explanation in Section 18.5 of how the RUWO algorithm is incorporated into a method for producing wideband FM waveforms with large space-frequency nulls as discussed in [11]. The chapter concludes with a summary of presented work and a discussion of future work and open problems on the topic of space-time transmit nulling with the goal of RF spectrum interoperability.

Chapter Contents:

• 18.1 Introduction
• 18.2 Overview of reiterative uniform weight optimization (RUWO) algorithm
• 18.2.1 General formulation
• 18.2.2 Spatial nulling
• 18.2.3 Frequency nulling
• 18.2.4 Space–frequency nulling
• 18.2.5 Deterministic and adaptive spatial interference covariance
• 18.3 Experimental MIMO radar test bed
• 18.4 Experimental demonstration of transmit nulling
• 18.4.1 Base-band loop-back demonstration
• 18.4.2 Open-air demonstration of space–frequency transmit nulling
• 18.5 Incorporation of RUWO within a wideband emission design problem
• 18.5.1 Wideband array analysis
• 18.5.1.1 Wideband beamforming
• 18.5.1.2 Wideband definition and the narrowband assumption
• 18.5.1.3 Physical considerations and the invisible space
• 18.5.2 RUWO within spectral shaping optimization
• 18.5.3 Wideband MIMO radar emission optimization with space–frequency nulling
• 18.5.3.1 Parameter initialization
• 18.5.3.2 Emission design via alternating projections
• 18.5.4 Emission optimization analysis
• 18.6 Summary
• 18.7 Looking ahead
• Acknowledgments
• References

Inspec keywords: radar transmitters; radiofrequency interference; optimisation; interference suppression; MIMO radar

Other keywords: narrowband loop-back; eight-channel X-band coherent MIMO radar test bed; open-air experimental applications; wideband FM waveforms; space-frequency transmit nulls; STAN; space-time transmit nulling; RF spectrum interoperability; radio frequency interference avoidance; Naval Research Laboratory's Space Time Adaptive Nulling radar test bed; RUWO algorithm

Subjects: Electromagnetic compatibility and interference; Optimisation techniques; Radar equipment, systems and applications