Quadrature Frequency Generation for Wideband Wireless Applications by Mohammad Elbadry & Ramesh Harjani

Author:Mohammad Elbadry & Ramesh Harjani
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

4.3 Proposed QVCO

In the absence of parasitics, the ratio between the maximum and the minimum oscillation frequency of an LC oscillator would be given by:

(4.1)

where f max is the maximum oscillation frequency, f min is the minimum oscillation frequency, C max is the maximum capacitance, and C min is the minimum capacitance. Practically, the tank capacitance has a considerable percentage of parasitics (C par ). If switched-capacitor tuning is used, then a part of the parasitic capacitance (C fixed ) will be due to cross-coupled pair, the parasitic capacitance of the tank inductor, input capacitance of the QVCO buffers, as well as any deliberate fixed capacitance connected to the tank. Another major parasitic component will arise from the parasitic top and bottom plate capacitances associated with the switched-capacitor bank, as well as the switch parasitics. If the parasitic capacitance for each switched capacitor of value C is given by , where , then the total parasitic capacitance can be given by:

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