| Summary: | Future driver assistance and autonomous driving systems require high-resolution 4D imaging radars that provide detailed and robust information about the vehicle's surroundings, even in poor weather or lighting conditions. In this work, a novel high-resolution radar system with 1728 virtual channels is presented, exceeding the state-of-the-art channel count for automotive radar sensors by a factor of 9. To realize the system, a new mixed feedthrough and distribution network topology is employed for the distribution of the ramp oscillator signal. A multilayer printed circuit board is designed and fabricated with all components assembled on the back side, while the radio frequency signal distribution is on a buried layer and only the antennas are on the front side. The array is optimized to enable both multipleinput multiple-output operation and transmit beamforming. A sparse array with both transmit and receive antennas close to the transceivers is realized to form a 2D array with a large unambiguous region of <inline-formula><tex-math notation="LaTeX">$130 \mathrm{^{\circ }}$</tex-math></inline-formula> × <inline-formula><tex-math notation="LaTeX">$75 \mathrm{^{\circ }}$</tex-math></inline-formula> with a maximal sidelobe level of <inline-formula><tex-math notation="LaTeX">$-15 \,\mathrm{{\rm dB}}$</tex-math></inline-formula>. The array features a <inline-formula><tex-math notation="LaTeX">$3 \,\mathrm{{\rm dB}}$</tex-math></inline-formula> beamwidth of <inline-formula><tex-math notation="LaTeX">$0.78 \mathrm{^{\circ }}$</tex-math></inline-formula> × <inline-formula><tex-math notation="LaTeX">$3.6 \mathrm{^{\circ }}$</tex-math></inline-formula> in azimuth and elevation, respectively. Radar measurements in an anechoic chamber show that even the individual peaks of the absorber in the chamber can be detected and separated in the range-angle cut of the 4D radar image. The performance is validated by measurements of a parking lot, where cars, a pedestrian, a fence, and a street lamp can be detected, separated, and estimated correctly in size and position.
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