Fig. 1. Ring oscillator using negative skewed scheme: (a) conceptual diagram, (b) schematic diagram [3].
Fig. 2. Frequency multiplication by combining 0˚, 120˚, 240˚ signals.
Fig. 3. Coupled ring oscillators [7,8].
Fig. 4. Overall architecture of the proposed oscillator.
Fig. 5. Delay cell.
Fig. 6. Coupled 3-stage ring oscillators.
Fig. 7. Simulated waveform of multiphase signals.
Fig. 8. Frequency multiplier.
Fig. 9. Simulated waveform of frequency multipliers.
Fig. 10. The 3-stage ring oscillator with dual delay path(C3 structure).
Fig. 11. Simulated frequency range of the proposed VCO.
Fig. 12. Simulated phase noise.
Table 1. List of designed ring oscillators.
Table 3. Performance summary and comparison of VCOs
Table 2. Performance comparison of various ring oscillator structures.
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