Design of fast settling frequency synthesizer for a 60GHz frequency-hopped RADAR application

Abstract

60GHz ISM band is an attractive band that can achieve a high data rate as it can use a huge bandwidth of up to 14GHz. However, this band has a problem with atmospheric attenuation, which causes the problem of degradation of the signal-to-noise ratio. In particular, in the case of RADAR technology, which is in the spotlight due to autonomous driving and unmanned systems, signal-to-noise ratio performance is much more deteriorated in the presence of signal interference, making it difficult to achieve the required performance. To solve this problem, in this paper, a Frequency-hopped RADAR, which is robust against signal interference, is proposed as a solution, and a frequency synthesizer with a short settling time is proposed for its implementation. A frequency synthesizer using a single-sideband mixer (SSB) was used to have a short settling time while covering a wide bandwidth in the 60GHz ISM band, and by adopting the injection-locked oscillator (ILO) as a filter, spur, a chronic problem of SSB mixers is improved. In addition, a calibration circuit that corrects the change of the ILO's frequency characteristics with external factors or time is presented. Using the technology proposed in this paper, simulation verification was performed with a 28nm CMOS process, and it was confirmed that the frequency settling time was within 100ns.