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 all-pass current mirror (CM)-based filters, a 1st-order CM low-pass filter and a CM bilinear transfer function. The bilinear transfer function is described in terms of a negative resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> = -R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ) where R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</sub> formed by a resistor load R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) 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 0.15deg, 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">norm</sub> ) is 139.29 dBc/Hz. The ratio of the oscillation frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) to the unity-gain frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of a transistor is 0.134.