Existing radiofrequency (RF) seekers use mechanically steerable antennas. In order to
improve the robustness and performance of the missile seeker, current research is investigating the replacement of mechanical 2D antennas with active electronically controlled
3D antenna arrays capable of steering much faster and more accurately than existing solutions. 3D antenna arrays provide increased radar coverage, as a result of the conformal
shape and flexible beam steering in all directions. Therefore, additional degrees of freedom
can be exploited to develop a multifunctional seeker, a very sophisticated sensor that can
perform multiple simultaneous tasks and meet spectral allocation requirements.
This thesis presents a novel radar configuration, named multibeam radar (MBR), to
generate multiple beams in transmission by means of waveform diversity. MBR systems
based on waveform diversity require a set of orthogonal waveforms in order to generate
multiple channels in transmission and extract them efficiently at the receiver with digital
signal processing. The advantage is that MBR transmit differently designed waveforms in
arbitrary directions so that waveforms can be selected to provide multiple radar functions
and better manage the available resources.
An analytical model of an MBR is derived to analyse the relationship between individual channels and their performance in terms of isolation and phase steering effects.
Combinations of linear frequency modulated (LFM) waveforms are investigated and the
analytical expressions of the isolation between adjacent channels are presented for rectangular and Gaussian amplitude modulated LFM signals with different bandwidths, slopes and frequency offsets. The theoretical results have been tested experimentally to corroborate the isolation properties of the proposed waveforms. In addition, the practical
feasibility of the MBR concept has been proved with a radar test bed with two orthogonal
channels simultaneously detecting a moving target
