Investigation of Coupling Mechanisms for Efficient High Power and Low Phase Noise E-Band Quadrature VCOs in 130nm SiGe

• Published in: IEEE journal of microwaves 2024-04, Vol.4 (2), p.264-276
• Main Authors: Starke, David, Thomas, Sven, Bredendiek, Christian, Aufinger, Klaus, Pohl, Nils
• Format: Article
• Language: English
• Subjects: BiCMOS; BiCMOS integrated circuits; coupled oscillators; cross-coupled; Harmonic analysis; microwave and millimeter wave oscillators; millimeter-wave; MMIC; MMICs; Oscillators; quadrature; QVCO; SiGe BiCMOS; Silicon germanium; voltage-controlled oscillator (VCO); Voltage-controlled oscillators
• ISSN: 2692-8388; 2692-8388
• DOI: 10.1109/JMW.2024.3370395

This article compares two SiGe Colpitts quadrature voltage-controlled oscillators (QVCO) with different coupling techniques in the low E-Band, intended to be used as signal sources for push-push frequency doublers. The first QVCO is based on a cross-coupled tail-current topology, while the second is based on a fundamental active coupling network. The cross-coupled QVCO has a center frequency of 64.3 GHz and a bandwidth of 2.5 GHz. This circuit realization provides up to 12.2 dBm output power per channel and has a power consumption of 385 mW, resulting in a dc-to-RF efficiency of 8.6%. The phase noise of this oscillator at 1 MHz offset frequency is as low as −105 dBc/Hz. The fundamentally coupled QVCO has a center frequency of 67 GHz with a bandwidth of 3.9 GHz. It provides 13.1 dBm output power per channel while consuming 410 mW of power, resulting in a dc-to-RF efficiency of 9.9%. The oscillator's phase noise at 1 MHz offset frequency is as low as −105.2 dBc/Hz. In addition to the presented circuits, this article introduces a method to measure the relative phase error of quadrature signals utilizing a vector network analyzer. This method is verified with measurements of the developed QVCOs.