A new sigma-delta modulator architecture for wide bandwidth application called cascaded feedforward sigma-delta modulator is proposed in this paper. This sigma-delta modulator is similar to the conventional feedforward summation sigma-delta modulator. The conventional feedforward summation sigma-delta modulator uses multi-bit feedback and therefore a multi-bit digital-to-analog converter (DAC) ...

In recent years, the research toward the development of high speed and high resolution analog-to-digital converters (ADCs) has been equally driven by the demand of high-speed wire line and wireless communication services. Delta-Sigma ADCs are widely used in wireless applications due to their oversampling and noise shaping characteristics. This thesis aims to design a continuous-time sigma-delta...

Chirp compensation is demonstrated using voltage division to a long-section electroabsorption phase modulator together with an amplitude modulator arranged in a tandem configuration, both integrated with an SOA and a sampled-grating DBR laser.

Radio over Fiber (RoF) is a next generation wireless broadband Internet access technology. In Radio over Fiber system the radio signal is generated at the central station is modulated on to light and transmitted over optical fiber cable to various base stations. The base station has to convert the optical signal to an electrical signal, amplify and transmit it. Modulation of RF signal onto ligh...

A continuous-time (CT) ΣΔ modulator for sensing and direct analog-to-digital conversion of nA-range (subthreshold) currents is presented in this work. The presented modulator uses a subthreshold technique based on subthreshold source-coupled logic cells to efficiently convert subthreshold current to digital code without performing current-to-voltage conversion. As a benefit of this technique, t...

-The input feedforward path in a ΔΣ modulator is an attractive technique for low-distortion swing-reduction design. It helps lower the power dissipation, especially in ΔΣ modulators designed with low oversampling ratios (OSRs) in low-voltage nanometer CMOS technologies. However, a ΔΣ modulator with analog feedforward (AFF) requires an analog adder before the quantizer, which can limit the achie...

This article discusses the applicability of quadrature ΣΔ modulator (QΣΔM) based analog-to-digital (A/D) conversion in cognitive radio (CR) receivers. First, unavoidable in-phase/quadrature (I/Q) mismatch effects, limiting the dynamic range, are analyzed in closed-form in the case of a first-order modulator. In addition, using the derived analytical converter model, it is shown that notching th...