A comparative study of complex multiple-band noise-shaping sigma-delta modulators for multi-tone input signals

This paper presents a comparative study of complex single-bit and multi-bit sigma-delta modulators that are capable of providing concurrent multiple-band noise-shaping for multi-tone narrow-band input signals. The concepts applied for the three design methodologies are based on the noise transfer functions of complex comb, complex slink and complex multi-notch filters.

Methods for the transfer function design of multiple narrow-band bandpass sigma-delta modulators

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, which can achieve concurrent multiple noise-shaping for multi-tone input signals. Four different design methodologies based on the noise transfer functions of comb filters, slink filters, multi-notch filters and fractional delay comb filters are applied for the design of these multiple-band sigma-delta modulators. The latter approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter-based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies. The merits and drawbacks of each technique for the various sigma-delta topologies are assessed in terms of in-band signal-to-noise ratios, accuracy of tunability and coefficient complexity for ease of implementation.

Introduction: the impact of the 'War on Terror' on executive–legislative relations: a global perspective

In democratic polities, constitutional equilibria or balances of power between the executive and the legislature shift over time. Normative and empirical political theorists have long recognised that war, civil unrest, economic and political crises, terrorist attacks, and other events strengthen the power of the executive, disrupt and threaten constitutional politics, and damage democratic institutions: crises require swift action and executives are thought to be more capable than parliaments and legislatures of taking such actions. The terrorist attacks on New York and Washington on 11 September 2001 and the ensuing so-called 'war on terror' declared by President Bush clearly constituted a crisis, not only in the United States but also in other political systems, in part because of the US's hegemonic position in defining and shaping many other states' foreign and domestic policies. Dicey, Schmitt, and Rossiter suggest that critical events and political crises inevitably trigger the concentration of (emergency) powers in the hands of the executive. Aristotle and Machiavelli questioned the inevitability of this process. This article and the articles that follow in this Special Issue utilise empirical evidence, through the use of case studies of the United States, the United Kingdom, Russia, Australia, Israel, Italy and Indonesia, to address this debate. Specifically, the issue explores to what extent the external shock or crisis of 9/11 (and other terrorist attacks) and the ensuing 'war on terror' significantly changed the balance of executive-legislative relations from t (before the crisis) to t+1 (after the crisis) in these political systems, all of which were the targets of actual or foiled terrorist attacks. The most significant findings are that the shock of 9/11 and the 'war on terror' elicited varied responses by national executives and legislatures/parliaments and thus the balance of executive-legislative relations in different political systems; that, therefore, executive-legislative relations are positive rather than zero-sum; and that domestic political contexts conditioned these institutional responses.

Narrow-band variable center frequency single-loop and multistage sigma-delta modulators for bandpass signals

Oversampled narrow-band single-loop and multistage resonator-based bandpass sigma-delta (Σ-Δ) modulators that can accommodate different passband center to sampling frequency ratios are reported. These tunable bandpass configurations are designed by analytically determining and subsequently verifying through detailed empirical simulations the required compensation hardware to deliver enhanced noise-shaping. It is demonstrated that comparatively superior in-band signal-to-noise ratios and dynamic ranges are attributed to the inclusion of appropriate digital feedforward and feedback compensators within these structures.

Application of fractional delay filters to tune the centre frequency location of single-band sigma-delta modulators

This paper presents a novel technique for the design of narrow-band sigma-delta modulators with an embedded tunable centre frequency mechanism. This method demonstrates that the use of sum filters combined with a fractional delayer provide the flexibility of tuning the noise shaping band for any desired variable centre frequency input signal.

Increasing the variability of centre frequency locations in multiple-band sigma-delta modulators via the use of fractional delay filters

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, that can achieve concurrent multiple noise-shaping for multi-tone input signals. This approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies.

Effective-fourth-order resonator based MASH bandpass sigma-delta modulators

Two novel effective-fourth-order (eighth-order) resonator based MASH (MultistAge noise SHaping) bandpass Σ-Δ modulators are introduced at the behavioural level and subsequently examined by simulations utilising the ALTA SPW environment. The considered bandpass configurations have in their loop filter a cascade of standard second-order resonator structures in order to achieve appropriate noise shaping. The quantisation noise in each stage is suppressed by feeding the error of each section into the input of the following stage. It is demonstrated in this paper that the quadruple effective-first-order cascade configuration has significantly better performance as well as conforming more closely with theory in comparison with the effective-second-order effective-second-order cascade. The superior performance of the former can be attributed to the cumulative effect of the multi-bit outputs as well as the presence of more notch filters.

MASH structures for bandpass sigma-delta modulators

The paper presents simulation results from investigating the behaviour of multistage (MASH) oversampled bandpass sigma-delta (Σ-Δ) modulators for use in analogue to digital converters for high frequency narrowband applications such as the signals out of the intermediate frequency (IF) section of a superheterodyne radio receiver. The bandpass configurations under consideration have in their loop filter a cascade of second-order resonator structures in order to achieve acceptable noise shaping. The quantisation noise in each stage is suppressed by feeding the error of each section into the input of the following stages. It is demonstrated that the triple effective-first-order bandpass MASH structure has significantly better performance compared with the effective-second-order effective-first-order bandpass MASH structure.

Parties in democratic national assemblies: comparative assessment of parliaments note

This paper argues that the analysis of democratic national assemblies is not only impossible without discussing political parties, but also incomprehensible without recognizing parties as the most significant organizations within them. Parties have structured political groupings and demands on government even before assemblies were democratically elected. And although parties may be in decline as institutions mediating between society and government in the current era, they remain significant as organizing forces within government. The paper first explains the origins of party organizations within parliaments by exploring why individual members and the assemblies taken as a whole need parties: what are their costs and benefits? It then describes the manner in which party organizations operate in different national assembly chambers. The third section analyses types and sources of party influence, including the role played by party leaders in manipulating legislative agendas, structuring Members’ policy choices and shaping policy outcomes. The final section reviews how politi- cal scientists have sought to explain intra-party cohesion and discipline across different national assemblies.

How does a house remember? heritage-ising return migration in an Indonesian-Chinese house museum in Guangdong, PRC

This paper is an attempt to integrate heritage and museum studies through exploring the complex relationship between the materiality of architecture and social memories with a house museum of return migration in Guangdong, PRC as a case study. It unveils that the ongoing process of memory is intrinsically intertwined with spatial and temporal dimensions of the physical dwelling and built environment and the wider social-historical context and power relations shaping them. I argue that it is the house as ‘object of exhibit’ just as much as the exhibits inside the house that materialises the turbulent and traumatic migratory experience of Returned Overseas Chinese, embodies their memories and exposes the contested nature of museumification. By looking at the socially and geographically marginalised dwelling of return migrants, the house draws people’s attention to the often neglected importance of conceptual periphery in re-theorising what is often assumed to be the core of heritage value. It points to the necessity to integrate displaced, diasporic, transnational subjects to heritage and museum studies that have been traditionally framed within national and territorial boundaries.

Territories of scarcity and creativity: a critical view of informal settlements and emerging tactics under conditions of scarcity in Nairobi, Kenya and Quito, Ecuador

This thesis explores the processes through which scarcity is constructed in informal settlements and how conditions emerging within its limits gives way to particular socio-spatial phenomena and influence the emergence of self-organisation and creative strategies from a non-expert perspective. At the same time, this thesis deconstructs these emerging tactics (reactive and transformative) in a diagrammatic way to generate a critical study of their potential for socio-spatial change that goes beyond the everyday survival. Most people associate scarcity with “not having enough” of something, most usually of a material nature. In contrast, this paper is based on the premise that scarcity is a constructed condition, therefore exploring it beyond its immediate manifestation and illustrating its discursive, distributive and socio-material components. In this line, the research uses Assemblage Theory as both an approach and a tool for analysis. This approach allows the research to depart from everyday narratives of the residents, and gradually evolve into a multi-scalar, non-linear reading of scarcity, by following leads into different realms and unpacking a series of routine events to uncover their connections to wider processes and particular elements affecting the settlement and the city as a whole. For this purpose, the research is based on a qualitative, flexible and multi-sited methodology, using different case studies as testing grounds. Collected data stems from a 11-months ethnographic fieldwork in informal settlements in Ecuador and Kenya, analysing the socio-spatial practices and strategies deployed by the different actors producing the built environment and arising from everyday and latent experiences of scarcity. The thesis examines the multi-scalar nature of these strategies, including self-building and management tactics, the mobilisation of grassroots organisations, the innovative ways of collaborating deployed by different coalitions and the reformulation of urban development policies. As outcomes of the research, the thesis will show illustrative diagrams that allow a better understanding of, firstly, the construction of scarcity in the built environment beyond its immediate manifestation and secondly, the way that emerging tactics a) improve existing conditions of scarcity, b) reinforce the status quo or c) contribute to the worsening of the original condition. Therefore, this thesis aims to offer lessons with both practical and theoretical considerations, by firstly, giving an insight into the complexity and transcalar nature of the construction of scarcity in informal settlements; secondly, by illustrating how acute conditions related to scarcity gives birth to a plethora of particular phenomena shaping the territory, social relationships and processes; and thirdly, by identifying specific characteristics within the informal that might allow for new readings of the city and possibilities for socio-spatial change under conditions of scarcity.

Citizenship, belonging and attachment in the ‘war on terror’

The ‘war on terror’ has had an enormous impact on citizens’ legal rights and legal status. Using data from interviews with British Pakistani Kashmiri Muslims, this paper explores how the change to citizens’ legal rights and legal status in the ‘war on terror’, the legal dimension of citizenship, has impacted the psychological dimension of citizenship. Through denoting legal rights, equality and status the study revealed the powerful role of the state and the police in shaping citizens’ perceptions of the legal dimension of citizenship. The paper explores how changes to participants’ perceptions of their legal status and legal rights are instrumental in shaping the psychological dimension of citizenship—participants’ sense of loyalty, belonging and attachment to their British identity and their Islamic identity.

Developing a Technoself System to Improve Lifelong Learning Engagement

Lifelong learning exists today in the context of a cultural and societal shift to a knowledge-based, technology-enhanced, and rapidly-changing economy. It has a significant impact on people’s lives and has become of vital importance with the emergence of new technologies that change how people communicate, collect information, and collaborate with others. The emerging technologies, such as social networking, interactive media and game technology, have expanded a new dimension of self – ‘technoself’ driven by socio-technical innovations and taken an important step forward in lifelong learning through the Technology Enhanced Learning (TEL). The TEL encourages learners as producers to embed personalized knowledge and collective experience on individualized learning within professional practice. It becomes more personal and social than traditional lifelong learning, especially about the ‘learning as socially grounded’ aspects. This paper studies the development of technoself system during lifelong learning and introduces technoself enhanced learning as a novel sociological framework of lifelong learning to couple the educational dimension with social dimension in order to enhance learner engagement by shaping personal learning focus and setting. We examine how people construct their own inquiry and learn from others, how people shift and adapt in these technoself-enhanced learning environments, and how learner engagement is improving as the involvement of learners as producers in lifelong learning. We further discuss the barriers and the positive and negative unintended consequences of using technology for lifelong learning.

National Policies for Local Urban Sustainability: A New Governance Approach?

Cities have become a focal point for efforts to transition towards a more sustainable, low-carbon society, with many municipal agencies championing ‘eco city’ initiatives of one kind or another. And yet, national policy initiatives frequently play an important – if sometimes overlooked – role, too. This chapters provides comparative perspectives on four recent national sustainable city programmes from France, India, Japan, and the United Kingdom. The analysis reveals two key insights: first, national policy is found to exercise a strong shaping role in what sustainable development for future cities is understood to be, which helps explain the considerable differences in priorities and approaches across countries. Second, beyond articulating strategic priorities, national policy may exercise a ‘soft’ governance function by incentivising and facilitating wider, voluntary governance networks in the effort to implement sustainable city projects locally. This innovative role, however, depends on the ability of national policy to produce resonance among societal actors and on its effective interaction with formal planning processes.