任意の中心周波数を設定可能なバンドパスΔΣ変調器

抄録

Delta-sigma (ΔΣ) analog-to-digital converters (ADC's) have been used for the application area that requires high-resolution signal acquisition. Most of the ΔΣ ADC's use the low-pass type ΔΣ modulators, where it is necessary to prepare a sufficiently high sampling frequency than the input signal. On the other hand, it is useful to convert only a specific band signal with a high accuracy in sensing systems and voice-band telecommunications. In order to satisfy the demands, band-pass ΔΣ modulators have been proposed. Band-pass ΔΣ modulators, as opposed to the low-pass type modulators, are able to convert signals that have closer sampling frequencies. In addition, the band-pass ΔΣ modulators suppress the low-frequency noise. In general, however, the center frequency and sampling frequency of a band-pass modulator is determined at the design stage. Therefore, it is difficult to apply bandwidths that are different from the original intended design. This paper proposes a band-pass ΔΣ modulator with variable center frequency. The modulator is designed by using multistage structure, thereby the modulator's stability and accuracy has improved. Furthermore, a self-calibration method for noise leakage due to a mismatch between the analog loop filter and the back-end digital filter are also proposed. The modulator with proposed methods was investigated using MATLAB simulator, confirming the effectiveness of the band-pass ΔΣ modulator.