Multi-Feed Holographic-Based Leaky Wave Antennas for MIMO-Radar Applications

This paper presents the integration and experimental validation of a multi-feed holographic-based leaky wave antenna (HLWA) array into an automotive MIMO radar system. First, a novel multi-layer integration concept with a quasi-coaxial transition is designed and fabricated, enabling rotationally symmetric surface wave excitation. Measured S-parameters from 76 GHz to 81 GHz show reflection coefficients below −10 dB and inter-port coupling <−22 dB. The frequency-dependent phase center shift of the HLWA relative to the physical feed position exhibits a maximum deviation below 0.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> across the automotive band. A wide beam synthesis process, fully decoupled from the antenna aperture size, is implemented by modifying the transverse modulation period of the surface impedance hologram. To combine multiple Tx and Rx sub-holograms into a shared holographic aperture, an angular-dependent hologram synthesis method is employed. The realized MIMO-HLWA array is fabricated on a fused silica wafer and comprises three Tx and four Rx feeds, resulting in a virtual aperture size of 6.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula>. Radar measurements of the MIMO-HLWA system in an anechoic chamber yield an ambiguity-free region of 21° × 21°. Subsequent validation scenarios demonstrate precise angular detection of multiple static targets and an average power improvement of 10 dB in range spectrum compared to the reference array is achieved. Moreover, dynamic scenarios involving one and two pedestrians verify the capability to resolve Doppler spectrograms clearly.