In this paper we present a method for stability analysis of high order Sigma-Delta modulators. The method is based on a parallel decomposition of the modulator. Using this presentation the general N-th order modulator could be considered as made up of N first order modulators, which interact only through the quantizer function. The decomposition helps us to extract the stability conditions of t...

A high resolution optical vector network analyzer (OVNA) implemented based on a wideband and wavelength-tunable optical single-sideband (OSSB) modulator is proposed and experimentally demonstrated. The OSSB modulation is achieved using a phase modulator and a tunable optical filter with a passband having two steep edges and a flat top. Wideband and wavelength-tunable OSSB modulation is achieved...

A silicon dual-ring modulator consisting of two serially cascaded rings with embedded PN junctions is driven by a differential signal pair. We show by simulation and experiment that the device has advantages over the single-ring modulator in terms of optical bandwidth, 3-dB modulation bandwidth and bit rate, at the expense of a 1.7-dB increase in the transmission penalty and a twofold increase ...

A Low power discrete time sigma delta ADC consisting of a second order sigma delta modulator and third order Cascaded Integrated Comb (CIC) filter is proposed. The second order modulator is designed to work at a signal band of 20K Hz at an oversampling ratio of 64 with a sampling frequency of 2.56 MHz. It achieves a signal to noise ratio of 85.2dB and a resolution of 14 bits. The CIC digital fi...

We show both numerically and experimentally that a phase modulator, acting as a time lens in the Fourier-lens configuration, can induce spectral broadening, narrowing, or shifts, depending on the phase of the modulator cycle. These spectral effects depend on the maximum phase shift that can be imposed by the modulator. In our numerical simulations, pulse spectrum could be compressed by a factor...

In this paper, a reduced complexity third-order digital delta-sigma modulator for fractional-N frequency synthesis is presented. The modulator consists of two sub-blocks and has a single bit output which makes it best for this application. A good shaping of quantization noise is achieved using a new architecture for a digital third-order delta-sigma modulator. The hardware required for this mod...

This paper presents a third order continuous time current mode ΣΔ modulator for WLAN 802.11b standard applications. The proposed circuit utilized feedback architecture with scaled and optimized DAC coefficients. At circuit level, we propose a modified cascade current mirror integrator with reduced input impedance which results in more bandwidth and linearity and hence improves the dynamic range...

This article focuses on the in-phase/quadrature (I/Q) imbalance problem in quadrature ΣΔ modulators (QΣΔM). In the literature, such quadrature modulators have been seen as a promising possibility for software defined radio (SDR) receivers, but matching the quadrature circuits is an inevitable problem for this kind of systems. In this article, an analytic closed-form model will be derived for a ...

In this paper we present a methodology for the simulation of continuous-time sigma-delta converters. This method, based on a fixed-step algorithm, permits not only a time-domain simulation of the modulator output but also the simulation of intermediary signals. The method is based on the discretization of the continuous-time models and the use of a discrete simulator such as Simulink, which is ...

A novel organic electro-optic (EO) modulator using transparent conducting oxides (ZnO and In2O3) as electrodes is demonstrated for the first time. The modulator employs the poled guest-host chromophore/polymer material AJL8/APC having r33=35pm/V and is able to achieve a low Vpi=2.8 V switching voltage for an 8mm-long device at a wavelength of 1.31ìm. This corresponds to a Vpi=1.1 V switching vo...