Reference Signal Synthesis for FMCW MIMO Radar Systems Using a Fractional-N Frequency Divider

In this paper we present a new approach for a signal synthesizer intended for wideband FMCW MIMO radar systems. An extremely fast frequency divider together with a control logic is used to realize a reference frequency ramp. This reference signal can then be multiplied to the demanded frequency band by a simple integer-N phase-locked loop in each of the transceivers of the MIMO system. To verify our approach we realize the reference frequency synthesizer that is based on a frequency divider realized in a SiGe bipolar technology. The spectrum of the frequency ramp shows no spurious as well as an excellent phase noise behaviour. Apart from the synthesizer itself, this paper will also deal with the determination of the division factor sequences, which is a challenging task due to the feedforwardstructure of the proposed architecture. The complete system is flexible in terms of bandwidth and ramp duration.