PCB-Based Cross-Coupled Differential VCOs Using a Novel LC-Tank Comprised of the Chip Inductors

Hikaru IKEDA
Yasushi ITOH

IEICE TRANSACTIONS on Electronics   Vol.E101-C    No.10    pp.744-750
Publication Date: 2018/10/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.744
Type of Manuscript: Special Section PAPER (Special Section on Microwave and Millimeter-Wave Technologies)
microwave,  differential,  cross-coupled,  VCO,  LC-tank,  SiGe HBT,  

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The paper presents the analysis, design and performance of PCB (Printed Circuit Board)-based cross-coupled differential VCOs using a novel LC-tank. As compared with the conventional LC-tank, a novel LC-tank is comprised of only chip inductors and thus has an advantage in providing a higher cutoff frequency. This feature attributes to the use of the parasitic elements of the chip inductors and capacitors. The cutoff frequencies were compared for both LC-tanks by calculation, simulation and measurement. Then the traditional cross-coupled differential oscillators having both LC-tanks were designed, fabricated and performed by using 0.35µm SiGe HBTs and 1005-type chip devices. The implemented oscillator using a novel LC-tank has shown a 0.12GHz higher oscillation frequency, while phase noise characteristics were almost the same. In addition, the cross-coupled differential oscillator utilizes a series RL circuit in order to suppress the concurrent oscillations. The implemented cross-coupled differential VCO employing Si varactor diodes with a capacitance ratio of 2.5 to 1 has achieved a tuning frequency of 0.92 to 1.28GHz, an output power greater than -13.5dBm, a consumed power less than 8.7mW and a phase noise at 100kHz offset in a range from -104 to -100dBc/Hz.