Dual-tracking multi-constellation GNSS front-end for high-performance receiver applications

This paper presents the design and implementation of a dual–tracking Radio Frequency (RF) front–end for a multi–constellation Global Navigation Satellite Systems (GNSS) receiver. The RF frond–end is based on the direct RF conversion architecture, which employs sub–Nyquist sampling (also known as subsampling) at RF. The dual–tracking RF front–end is composed of a few RF components that are duplicated to form the two RF channels. Employing a dual–channel Analogue–to–Digital Converter (ADC) enables synchronisation of the RF channels and minimises the errors resulting from the differences in the satellite clocks and the propagation delay between the two RF channels. The digitised GNSS signals are processed by two separate acquisition and tracking engines that are driven by the front–end’s master clock. This setup provides two synchronised receivers that are integrated onto one piece of hardware. The hardware is intended to be used for research applications such as multipath mitigation, scintillation assessment, and advanced satellite clock and spatial frame transformation modelling.

Eco-cities: technological showcases or public spaces?

A growing body of critical literature seeks to identify conceptual and practical problems accompanying the realisation of mainstream ‘eco-city’ initiatives around the world. However, little attention has been paid to the status of the ‘city’ itself within the broader discourse. If eco-cities are to be more than experimental ‘technological showcases’, and aim to transform urban life more generally, the question of what types of ‘cityness’ will ensue is of considerable importance. To effect a more significant sustainability transition, eco-city plans and policies may need somehow to encompass a more nuanced conceptualisation of cities as complex, unpredictable, and emergent spaces. The incompatibility of such a conceptualisation with liberal-modernist modes of planning means that radically innovative new approaches to eco-city development may need to be found. This thesis considers whether the eco-city, theorised as a multiple process of real-world experimentation, may shed some light on how ‘cityness’ might better be planned for in future. To do so, it conceptualises cityness through the lens of ‘publicness’. It makes an original contribution to knowledge by developing a new theoretical model of publicness as an ‘assemblage’ of space and behaviour, with an ‘emergent’ and ‘civic’ modality. It thereby extends recent debates over the idea of ‘urban assemblage’, and makes innovative links between theories of planning and of the public. This model informs the analysis of original empirical research, investigating the conceptualisation of the public in an international sample of official eco-city documents, and exploring the publicness of two implemented initiatives, in Portland, Oregon (US) and newly built Sejong City (South Korea). The research finds that publicness tends to be poorly articulated in mainstream eco-city plans and policies, with potentially negative implications for sustainability in the ‘urban age’. However, it also argues that state institution-led planning – even when experimental ‘governance’ approaches are adopted – may inevitably be limited in its ability to encompass the emergent public life of the city. The thesis concludes by considering the prospects for overcoming or more productively acknowledging these limits in future.