Eight-channel 77-GHz front-end module with high-performance synthesized signal generator for FM-CW sensor applications

This paper presents a new frequency-modulated continuous-wave front-end module intended to serve next-generation automotive radar sensors. Providing one transmit and eight receive channels, the module is designed to operate between a multibeam antenna and an advanced signal-processing unit. All receive channels are equipped with low-noise amplifiers, mixers for downconversion, and IF amplifiers. Cascaded buffer amplifiers for the local-oscillator signal enable parallel operation of all receive channels. A high-performance synthesizer provides generation and transmission of arbitrarily programmable frequency ramped waveforms with high stability and linearity. Slope and frequency deviation of the waveforms can be adjusted for the respective radar application. Short settling times of the synthesizer allow very fast slopes and, thus, short distance measurements. An overview of the overall front-end module design and realization approach is given, including a more detailed description of the synthesizer concept. All active millimeter-wave functions are realized with GaAs monolithic microwave integrated circuits assembled in a hermetically sealed multichip module (MCM). The MCM itself is incorporated into a three-layer printed-circuit-board stack onto which IF amplification, frequency control, waveform generation as well as dc and bias control is realized. A summary of the measured performance data obtained from correspondingly built-up prototypes is given.