A 5.4-7.4 GHz Ultra-Low Jitter Injection-Locked Frequency Tripler With 3rd Harmonic Current Boosting Input Buffer

We present a 5.4-to-7.4GHz injection-locked frequency tripler (ILFT) with enhanced 3rd harmonic injection using collector-to-base transformer-coupled input buffer. Regenerative feedback in the input buffer using a collector-to-base coupled transformer provides up to 2x improvement in the locking range of the ILFT compared to a conventional ILFT. Fabricated in 0.13 μm BiCMOS technology, the tripler exhibits a jitter tracking bandwidth, ωJTB of 20MHz. Due to its optimal jitter tracking bandwidth, the tripler filters the input noise beyond the ωJTB and effectively suppresses the free-running oscillator’s phase noise below ωJTB. We achieve an output rms jitter of 33.6 fs for an input rms jitter of 68 fs over a bandwidth of 1k-100MHz. The ILFT demonstrates a good sub-harmonic rejection ratio, SHRR of 51 dB and 48 dB for fundamental and second harmonic, respectively.