A low-power high-frequency all-pass-filter-based sinusoidal quadrature oscillator using CMOS current mirrors

Abstract

A low-power high-frequency sinusoidal quadrature oscillator is presented through the use of two allpass current mirror (CM)-based filters, a 1st-order CM lowpass filter and a CM bilinear transfer function. The bilinear transfer function is described in terms of a negative resistance (R N = -R L ) where R L is a resistor load of a current mirror. The technique is relatively simple based on (i) inherent time constants of current mirrors, i.e. the internal capacitances and the transconductance of a diode-connected NMOS, (ii) a simple negative resistance R N formed by a resistor load R L of a current mirror. Neither external capacitances nor inductances are required. As a particular example, a 1.01-GHz, 0.6-mW, 2-V CMOS all-pass-filter-based all-current-mirror sinusoidal quadrature oscillator is demonstrated in this paper. The oscillation frequency (f 0 ) is 1.01 GHz and is current-tunable over a range of 400 MHz or 40 %. The power consumption is at approximately 0.6 mW. The amplitude matching and the quadrature phase matching are better than 0.05 dB and 0.15°, respectively. Total harmonic distortions (THD) are less than 0.5 %. At 2 MHz offset from the 1.01 GHz, the carrier to noise ratio (CNR) is 83.01 dBc/Hz whilst the figure of merit called a normalized carrier-to-noise ratio (CNR norm ) is 139.29 dBc/Hz. The ratio of the oscillation frequency (f 0 ) to the unity-gain frequency (f T ) of a transistor is 0.134.