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For a planar inductor, the maximal quality factor, Qmax, is located at the specified frequency, fQmax. In this paper, a method called selective metal parallel shunting (SMPS) is proposed to move fQmax onto the desired frequency without additional processing steps. For a given planar inductor, a customized program is developed to find all the possible SMPS inductors and predict their Qmax and fmax. Three sets of planar, all metal parallel shunting (AMPS), and SMPS inductors have been implemented in a 1P4M 0.35 μm CMOS process to verify the proposed method. The prediction errors of Qmax and fQmax are less than 13% and 10%, respectively, between the simulated and measured ones. Moreover, three 2.3-2.4 GHz VCOs using planar, AMPS, and SMPS inductors, respectively, have also been realized. The phase noise of the VCO using SMPS inductors can be improved by 9.3 dB and 6 dB, respectively, compared to the VCOs using planar and AMPS inductors at 100 KHz offset frequency. The figure-of-merit (FOM) performance of the VCO using SMPS inductors can be comparable to the state-of-the-art publications.
Date of Conference: 12-14 June 2003