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The transfer of the forward scatter (FS) concept to passive coherent location (FS PCL) systems provides a new emerging area of research. This article is dedicated to the investigation of various aspects of a bistatic passive coherent location (PCL) system operating in the FS mode. For efficient signal processing, appropriate FS PCL system analysis is presented. It is shown that using a relatively small modernisation of traditional signal processing algorithms, a PCL system may effectively operate against stealth and low profile targets crossing or being located in the vicinity of the radar baseline. The FS signals have been analysed in view of finding key effects and parameters influencing the waveforms and spectra which define the overall signal processing. Experimental results are given to validate the presented analysis.

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A novel dielectric lens antenna with a broadband integrated waveguide-based feed and an optimized tapered extension is presented for low TeraHertz frequencies. The antenna consists of an extended hemispherical lens fed by a standard WR-3 rectangular waveguide fitted directly at the bottom of the lens. The antenna has been designed for high resolution imaging radar systems requiring very wide bandwidth performance and highly directive beams. A novel matching technique based on an air pocket etched off the lens dielectric is employed to obtain broadband antenna operation covering the entire dominant-mode bandwidth of the waveguide. In addition, a new taper shaped lens extension is proposed for the first time and optimized to achieve improved sidelobe level and gain performance. The antenna is compatible with newly developed waveguide-based automotive radar and communications systems. The operating 3dB gain bandwidth is 30% (230GHz -310GHz) achieving a maximum of 30dB measured gain. The measured S11 is well below -14dB across the WR-3 band.

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In this study, the authors investigate the application of the Doppler beam sharpening (DBS) technique for angular refinement to the emerging area of low-terahertz (THz) radar sensing. Ultimately this is to improve radar image quality in the azimuth plane to complement the excellent range resolution and thus improve object classification in low-THz radar imaging systems for autonomous platforms. The study explains the fundamental theory behind the process of DBS and describes the applicability of DBS to automotive sensing, indicating the potential for synthetic beamwidths of a fraction of a degree. Low-THz DBS was experimentally tested under controlled laboratory conditions, not only to accurately localised target objects in Cartesian space but also to provide unique object imaging at low-THz frequencies with wide azimuthal beamwidth antennas. It was shown that a stationary (i.e. non-scanned) wide beam antenna mounted on a moving platform can deliver imagery at least comparable to that produced by physical beamforming, be that steering arrays or narrow beam scanning antennas as in the experimental case presented.

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