Fully Integrated Seven-Order Frequency-Range Quadrature Sinusoid Signal Generator

A compact wide-frequency-range quadrature sinusoid signal generator tailored to on-chip impedance spectroscopy instrumentation applications is described. Using a new hybrid structure, it provides seven orders of frequency-tuning range (1 mHz to 10 kHz) appropriate for impedance characterization of many sensor materials. The signal generator exhibits very accurate frequency tuning through digital control, and the new structure inherently guarantees good phase and amplitude matching between sine and cosine outputs across the supported frequency range. The circuit has been fabricated in a 0.5-mum CMOS process and occupies 1 mm². It consumes only 60 muA with a 3-V supply. Measurements show that the phase mismatch is less than 0.8^deg and that the amplitude mismatch is less than 3%. The total harmonic distortion is below 0.6% over the seven-order frequency range.