17.4 A 18.6-to-40.1GHz 201.7dBc/Hz FoMT Multi-Core Oscillator Using E-M Mixed-Coupling Resonance Boosting

The development of millimeter-wave (mmW) multiple-band systems for the 5G wireless and point-to-point backhaul communication requires ultra-wideband signal sources with low phase noise. However, with increasing parasitics and the limited quality factor of passive components at mmW bands, it is significantly challenging for an oscillator in a signal source to meet such performance. Recently, oscillator designs have evolved from the conventional single-core to multi-core types [1], [2]. With the parallel cross-coupled pairs and LCtanks, a multicore oscillator can efficiently reduce the phase noise level, while increasing the chip size and limiting frequency tuning range. To extend the operation bandwidth, mode-switching multi-core oscillators [3], [7] are developed and enable phase-noise reduction and tuning-range extension simultaneously. Nevertheless, most of the reported mode-switching oscillators are dual-mode and are still not easily able to cover the multiple bands for mmW 5G radio. A series resonator mode switching oscillator [4] achieves triple modes using four resonators, which greatly increase the chip area. Moreover, the cross-coupled pairs in [4] are switched OFF in different modes, thus the multi-core phase noise reduction cannot be achieved in each mode. This paper proposes a mmW multi-core oscillator using electric-magnetic (E-M) mixed-coupling resonance boosting to achieve a quad-mode operation bandwidth from 18.6 to 40.1GHz, which can fully cover the 5G bands around 24, 28, 37, and 39GHz. The mmW tuning range is as wide as 73%. With the wideband flicker noise suppression, the 1/f3 phase-noise corner is far below 1MHz over the operation frequency. An FoM
_T
@1MHz of 201.7dBc/Hz is achieved at mmW bands by the proposed oscillator.