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This paper reports a new improved Clapp VCO topology designed in 180 nm Si-Ge HBT technology for operations around 5 GHz. The designed topology uses a series-tuned resonator, a back-to-back series varactor configuration for tuning the output frequency and a filtering tail current designed for shunting to ground the second harmonic noise component. At the supply voltage of 3.3V, and across Process,...
Fractional-N frequency synthesizers are widely used in modern electronic systems. Their performance can be degraded by the presence of spurious tones (spurs). Many mechanisms for the production of spurs have been identified, making it possible to develop appropriate strategies to minimise or eliminate them. This paper describes another spur generation mechanism which has not been reported previously...
When implemented in Si-Ge HBT technology, the differential Colpitts LC Voltage-Controlled Oscillator (VCO) can deliver low close-in phase noise by virtue of its low flicker noise corner frequency. The Armstrong topology reuses bias current and therefore should be more power-efficient than Colpitts. By comparing differential Colpitts and Armstrong architectures side-by-side, this paper shows that the...
Amplitude-to-phase-noise conversion due to varactors for tuning the oscillation frequency can limit the close-in phase noise performance in LC voltage-controlled oscillators (VCOs). Highly nonlinear varactors make the output frequency dependent on oscillation amplitude and consequently amplitude noise translates into phase noise. The conversion coefficient KAM−FM quantifies this effect, and reveals...
It has been shown in the literature that a cross-coupled CMOS LC VCO will outperform an equivalent Colpitts VCO. In the case of bipolar devices, the jury is still out. This paper reports a comparative analysis of phase noise (PN), tuning range (TR), dissipated DC power and Figure of Merit (FoM) in cross-coupled and differential Colpitts LC VCOs topologies designed in 180 nm Si-Ge HBT technology for...
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