Interstacked Transformer Quad-Core VCOs

This paper presents for the first time a quad-core oscillator based on a very compact interstacked transformer that tightly couples the four cores without oscillation mode ambiguity thanks to its strong magnetic coupling factor. As a proof of concept, a 19.125 GHz oscillator for a narrowband 77 GHz radar system was designed in 28 nm fully depleted silicon-on-insulator CMOS technology with a general purpose back-end-of-line. The soundness of the proposed quad-core oscillator topology is demonstrated by comparison with state-of-the-art quad-core solutions, highlighting a significant advantage in terms of area occupation and power consumption. The proposed topology can be profitably exploited in several RF/mm-wave applications, such as radar and wireless communication systems.