Luís Oliveira,

R – INESC-ID Lisboa


Nowadays, the demand for mobile and portable equipment has led to a large increase in wireless communication applications. Modern transceiver architectures, to achieve full integration and low cost, require quadrature oscillators with very accurate quadrature relationship, since quadrature errors affect strongly the overall performance of the RF (Radio Frequency) front-end. Relaxation oscillators are known for their poor phase-noise performance. Here we show that, by cross-coupling two oscillators, the phase-noise performance is improved. Moreover, strong coupling reduces the effect of mismatches and other disturbances: these are attenuated by the feedback, becoming second order effects, and this guaranties a very accurate quadrature. LC oscillators are known for their good phase-noise performance when compared with relaxation oscillators. In a cross-coupled LC oscillator, coupling is necessary for accurate quadrature in the presence of mismatches; however, this degrades the oscillator phase-noise, due to the degradation of the quality factor.


Date: 2007-Feb-15     Time: 14:00:00     Room: 425, 4th stage at INESC-ID

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