Mitigating interference via spatial and spectral nulling

• Published in: IET radar, sonar & navigation Vol. 8; no. 2; pp. 84 - 93
• Main Authors: Higgins, Thomas, Webster, Tegan, Shackelford, Aaron K
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering and Technology 01.02.2014; The Institution of Engineering & Technology
• Subjects: Algorithms; Arrays; constant modulus radar waveforms; eight‐channel X‐band coherent MIMO radar test bed; interference mitigation; interference suppression; iterative methods; loop‐back configuration; loop‐back experiment; MIMO radar; MIMO transmit arrays; multiple‐input multiple‐output transmit arrays; next generation radar system; Nulling; open air configuration; open air experiment; over‐crowded radiofrequency spectrum; phase‐only transmit nulling; phase‐only weights; Radar; radar receivers; radar transmitters; receiver; reiterative uniform weight optimisation algorithm; RUWO algorithm; signal‐to‐interference‐plus noise ratio framework; Sonar; space‐frequency nulls; spatial nulling; Special Issue: Bistatic and MIMO radars and their applications in surveillance and remote sensing; Spectra; spectral nulling; transmitter; Waveforms; X-band; over-crowded radiofrequency spectrum; iterative methods; spatial nulling; open air configuration; MIMO transmit arrays; MIMO radar; phase-only weights; open air experiment; transmitter; space-frequency nulls; interference mitigation; radar transmitters; multiple-input multiple-output transmit arrays; interference suppression; receiver; spectral nulling; reiterative uniform weight optimisation algorithm; signal-to-interference-plus noise ratio framework; eight-channel X-band coherent MIMO radar test bed; RUWO algorithm; radar receivers; loop-back configuration; loop-back experiment; next generation radar system; constant modulus radar waveforms; phase-only transmit nulling
• ISSN: 1751-8784; 1751-8792
• DOI: 10.1049/iet-rsn.2013.0194

Phase-only transmit nulling may help the next generation of radar systems operate in an over-crowded radio frequency spectrum. The reiterative uniform weight optimisation (RUWO) algorithm generates constant modulus radar waveforms with spatial, frequency or space–frequency nulls for multiple-input multiple-output (MIMO) transmit arrays by utilising the maximum signal-to-interference plus noise ratio framework in a reiterative fashion. This study presents loop-back and open air experimental results, obtained using an eight-channel X-band coherent MIMO radar test bed, that demonstrate the use of RUWO to generate constant modulus waveforms that possess spatial and/or frequency nulls. The RUWO algorithm is first used to deterministically generate phase-only weights that produce spatial, frequency or space–frequency nulls at baseband in a loop-back configuration. The algorithm is then utilised to generate weights to produce spatial nulls, both deterministically and adaptively, for the full eight-channel test bed in an open air configuration. The deterministic and adaptive strategies are compared; results demonstrate that RUWO can be used to create spatial nulls and highlight the need for careful calibration of both the transmitter and the receiver.