A high-resolution frequency modulated continuous wave imaging radar for short-range applications is presented. A range resolution of about 1 cm is achieved with a bandwidth of up to 16 GHz around 160 GHz. In order to overcome losses and large tolerances on a printed circuit board (PCB), 8 coherently coupled monolithic microwave integrated circuits (MMIC) are used, each with one transmit and receive antenna on-chip and each representing a single channel radar system. The signals on the PCB are below 12 GHz, which facilitates fabrication and enables a design with low-cost substrates. The MMIC comprises a phase noise optimized architecture with a fully integrated on-chip frequency synthesizer. Due to partly uncorrelated phase noise between the frequency synthesizer components, the noise level is increased in bistatic radar measurements between two different MMICs, which is explained by a thorough phase noise analysis. Time-division multiplexing is used to realize a multiple-input multiple-output system with a virtual array of 64 elements and an angular resolution better than 1.5 • for the designed array. The positioning tolerances of the MMICs are included into the design resulting in a robust array design. The high-resolution radar performance is proven by imaging radar measurements of two exemplary scenarios.
In radar measurements the observed area is limited by the antenna beamwidth and due to the usually fixed transceiver position, only unhidden targets in a small observation area can be detected. Furthermore, bulky lens dimensions prevent the use of radar systems in constricted surroundings despite the small dimensions of microwave monolithic integrated circuit (MMIC) radars. To avoid this issue, a new system concept for a flexible and low cost 160 GHz radar sniffer probe is presented. The flexible sniffer probe is an extremely low loss dielectric waveguide with a dielectric elliptical lens (28 dBi) at the end. The dielectric waveguide has dielectric losses of 4.5 dB/m at 160 GHz and high flexibility, supporting bending radii of 1.5 cm with negligible losses. To feed the dielectric waveguide a metallic waveguide with a duplexer is used which is fed by a special MMIC-to-metallic waveguide transition. The proposed system expands the known radar measurement scenarios with new industrial, medical, and security applications.
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