Waveform selection is a critical component of an interferometer architecture design. Achieving angle accuracy in complex target and interference environments can be accomplished only with the proper choice of waveforms. Mediumto highresolution waveforms can mitigate the effects of clutter and multipath that can degrade phase integrity and angle accuracy. When the clutter and/or multipath are spatially distributed, the range sidelobe performance resulting from the matched filter is critical in reducing the effects of distributed clutter and multipath. Because an interferometer may use small distributed arrays with relatively large beamwidths, the selection of waveforms to mitigate the scattering effect or to resolve target features becomes an important part of an interferometer architecture. In this chapter, several types of frequencyand phase-modulated waveforms are defined, and their impact on post-compression angle accuracy is discussed.

Chapter Contents:

• 5.1 Frequency Coding
• 5.1.1 Costas Codes
• 5.1.2 Linear Frequency Modulation
• 5.1.3 Frequency-Modulated Continuous Wave (FMCW)
• 5.1.4 Nonlinear Frequency Modulation
• 5.2 Phase Coding
• 5.2.1 Pseudorandom Noise Codes (Kasami Codes)
• 5.2.2 Group Modulation of PRN Codes
• 5.2.3 Essentially Orthogonal Waveforms
• 5.2.4 Optimized Multiphase Waveforms
• 5.3 Bounds on Autocorrelation and Cross-Correlation Performance
• 5.3.1 Correlation and Cross-Correlation of Random Binary Phase Sequences
• 5.3.2 Derivation of the Welch Bound for k=1
• 5.4 Chaotic Waveforms
• References

Inspec keywords: FM radar; radar resolution; interference suppression; matched filters; radar clutter; phase modulation; electromagnetic wave scattering; radar interferometry

Other keywords: high-resolution waveform; phase-modulation waveform; medium-resolution waveform; scattering effect mitigation; distributed clutter effect reduction; frequency-modulation waveform; range sidelobe performance; interferometer architecture design; radar waveform selection; post-compression angle accuracy; interference environment; matched filter; target feature resolution; complex target environment

Subjects: Radar equipment, systems and applications; Electromagnetic wave propagation; Electromagnetic compatibility and interference; Filtering methods in signal processing; Modulation and coding methods