Multistage Quadrature Sigma-Delta Modulators for Reconfigurable Multi-Band Analog-Digital Interface in Cognitive Radio Devices
TLDR
It is shown in the article through closed-form response analysis that the so-called mirror-frequency-rejecting STF design can offer additional operating robustness in challenging scenarios, such as the presence of strong mirror- frequencies blocking signals under I/Q imbalance, which is an unavoidable practical problem with quadrature circuits.Abstract:
This article addresses the design, analysis, and parameterization of reconfigurable multi-band noise and signal transfer functions (NTF and STF), realized with multistage quadrature ΣΔ modulator (QΣΔM) concept and complex-valued in-phase/quadrature (I/Q) signal processing. Such multi-band scheme was already proposed earlier by the authors at a preliminary level, and is here developed further toward flexible and reconfigurable A/D interface for cognitive radio (CR) receivers enabling efficient parallel reception of multiple noncontiguous frequency slices. Owing to straightforward parameterization, the NTF and the STF of the multistage QΣΔM can be adapted to input signal conditions based on spectrum-sensing information. It is also shown in the article through closed-form response analysis that the so-called mirror-frequency-rejecting STF design can offer additional operating robustness in challenging scenarios, such as the presence of strong mirror-frequency blocking signals under I/Q imbalance, which is an unavoidable practical problem with quadrature circuits. The mirror-frequency interference stemming from these blockers is analyzed with a novel analytic closed-form I/Q imbalance model for multistage QΣΔMs with arbitrary number of stages. Concrete examples are given with three-stage QΣΔM, which gives valuable degrees of freedom for the transfer function design. High-order frequency asymmetric multi-band noise shaping is, in general, a valuable asset in CR context offering flexible and frequency agile adaptation capability to differing waveforms to be received and detected. As demonstrated by this article, multistage QΣΔMs can indeed offer these properties together with robust operation without risking stability of the modulator.read more
Citations
More filters
Comparative Study between Continuous-Time Real and Quadrature Bandpass Delta Sigma Modulator for Multistandard Radio Receiver
TL;DR: In this article, a continuous-time quadrature bandpass delta sigma modulator is proposed for multistandard radio receiver based on the low-IF receiver architecture, which offers a viable solution for realizing digital, monolithic receivers.
Journal ArticleDOI
Frequency-Agile Multiband Quadrature Sigma-Delta Modulator for Cognitive Radio: Analysis, Design and Digital Post-Processing
TL;DR: A novel frequency-agile and reconfigurable transfer function design, allowing digital post-compensation of the MFI, is proposed, based on a novel closed-form transfer function model for higher-order quadrature Σ� Δ modulators (QΣΔMs) under implementation inaccuracies, proposed herein.
Journal ArticleDOI
Quantization Noise Reduction Techniques for Digital Pulsed RF Signal Generation Based on Quadrature Noise Shaped Encoding
TL;DR: Novel ways related to equalization techniques used for imbalanced digital complex valued systems are presented to mitigate conjugate image noise in digital RF transmitters.
Proceedings ArticleDOI
Digital mirror-frequency interference compensation for multiband quadrature sigma-delta ADC based cognitive radio receivers
TL;DR: A novel frequency-agile transfer function design for quadrature ΣΔ modulators (QΣΓMs) is proposed, allowing digital post-compensation of mirror-frequency interference generated by the mismatches between the receiver I and Q branches.
Patent
Dynamic range reduction for analog-to-digital converters
TL;DR: In this paper, an analog-to-digital (A2D) converter is used to determine whether an in-band blocker is present in the signal and adjust the transfer function of the analog to digital converter.
References
More filters
Journal ArticleDOI
NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey
TL;DR: The novel functionalities and current research challenges of the xG networks are explained in detail, and a brief overview of the cognitive radio technology is provided and the xg network architecture is introduced.
Book
Understanding Delta-Sigma Data Converters
TL;DR: This chapter discusses the design and simulation of delta-sigma modulator systems, and some of the considerations for implementation considerations for [Delta][Sigma] ADCs.
Journal ArticleDOI
An overview of sigma-delta converters
TL;DR: This article describes conventional A/D conversion, as well as its performance modeling, and examines the use of sigma-delta converters to convert narrowband bandpass signals with high resolution.
Journal ArticleDOI
Low-IF topologies for high-performance analog front ends of fully integrated receivers
Jan Crols,Michiel Steyaert +1 more
TL;DR: The fundamental principles of the low-IF receiver topology are introduced by applying the complex signal technique-a technique used in digital applications to the study of analog receiver front ends and its performance can be better.
Journal ArticleDOI
The Path to the Software-Defined Radio Receiver
TL;DR: The receiver's flexible analog baseband samples the channel of interest at zero IF, and is followed by clock-programmable downsampling with embedded filtering, giving a tunable selectivity that exceeds that of an RF prefilter, and a conversion rate that is low enough for A/D conversion at only milliwatts.