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

Abstract

Abstract-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-μm CMOS process and occupies 1 mm 2 . It consumes only 60 μA with a 3-V supply. Measurements show that the phase mismatch is less than 0.8• and that the amplitude mismatch is less than 3%. The total harmonic distortion is below 0.6% over the seven-order frequency range.Index Terms-Analog filter, impedance measurement, quadrature signal generator, sinusoid signal generators, wide-frequencyrange frequency tuning.

High-throughput impedance spectroscopy biosensor array chip

“…The area of each IRC channel is 0.045 mm 2 , which is 25% less than the area of the circuit reported in [1]. The performance of the SFS matched the original version reported in [29], with a spurious-free dynamic range of the generated sinusoid at more than 50 dB and a total harmonic distortion of less than 0.6% in the 1 mHz-10 KHz frequency range.…”

“…The output of the sampling circuit contains a low-frequency replica that represents the frequency difference between the input signal and the sampling clock. A detailed analysis was presented in [29].…”

“…The limitations of the quadrate oscillators and triangle-to-sine generators are their poor linearity and difficulty in precisely controlling frequency. Our group reported an alternative method that is controlled purely by digital signals and produces excellent frequency accuracy and linearity [29]. It provides seven orders of frequency-tuning range (1 mHz-10 kHz) appropriate for impedance characterization of many biosensor interfaces.…”

Bioimpedance Sensors: A Tutorial

“…Alternatively, an unevenly tapped resistor chain can be used to approximate a sinusoidal waveform by switching between taps. With appropriate switching, quadrature signals can be generated for synchronous demodulation front-ends (described in Section V.C) [190]. This is illustrated in Fig.…”

“…(a) Tapped resistor chain for sine wave approximation and the generation of quadrature signals. Adapted from[190]. (b) Exploiting the non-linear transfer function of a differential pair in weak inversion and the conversion of a triangular wave into a sine wave, as illustrated also by the plots on the right.…”