An Impact of Introducing Multi-Level Signals to a Bandpass Cascaded Delta-Sigma Modulator

An impact of introducing multi-level signals to a bandpass delta-sigma modulator (DSM), which is of particular interest for wireless communications applications, has been investigated. In particular, a cascaded architecture is studied, since this is favorable to obtain high resolution as well as stability. By increasing the number of the signal levels from two to 16, we have improved the DSM signal-to-noise ratio by 24 dB, or by 4 bits. This amount of improvement is almost the same as that for conventional lowpass DSMs. Our simulation also indicates that the distortion in the output waveform results from a mismatch between level intervals, which is inevitable in circuit implementations. Random selection of unit elements to generate one of 16 levels at each sampling time is proved effective to suppress the distortion.

• Type: Conference
• Year: 2002
• Where: ISMVL
• Authors: Takao Waho, Shin-ya Kobayashi, Koji Matsuura
• Keywords: Artificial Intelligence, Bandpass Delta-sigma Modulator, Conventional Lowpass Dsms, DSM Signal-to-noise Ratio, ISMVL 2002