Extended Phase Noise Performance in Mutual Negative Resistance CMOS LC Oscillator for Low Supply Voltages


IEICE TRANSACTIONS on Electronics   Vol.E89-C   No.6   pp.732-738
Publication Date: 2006/06/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e89-c.6.732
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Analog Circuit and Device Technologies)
analog circuits,  LC oscillator circuits,  CMOS analog circuits,  high-frequency circuits,  

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A LC oscillator based upon the quadrature magnetic coupling to generate a mutual negative resistance (mu-R) is introduced. The topology offers enhanced optimum phase noise at low supply voltages by enabling extended circuit operation in the current-limited regime through the control of its mutual inductors' coupling factor, k. The principal operation of the mu-R oscillator is described and its comparison with the popular cross-coupled topology is discussed. The capability of the technique is demonstrated via design examples of 1.8 GHz oscillators. Simulations show that, by employing inductors with a self-inductance of 2 nH, a quality factor of about 7.5 and a coupling k=0.52, the mu-R oscillator exhibits the minimum phase noise of -142 dBc/Hz at 3 MHz-offset with 18 mA bias current and 2 V supply. This is 3-dB more than the minimum achievable phase noise in the cross-coupled oscillator with identical component parameters and supply voltage level.