Reconfigurable RF Filters and Wideband Constant-HPBW Antenna Arrays for Next-Generation Radios

Ubiquitous use of wireless communications has increased the need for radio-frequency (RF) transceivers that simultaneously support multiple standards and waveforms and operate under dynamic interfering-signal conditions. For their realization, the development of reconfigurable and ultra-compact RF front-end/antenna interface components is necessary. Particularly, reconfigurable bandpass filters (BPFs) that adapt to different communication bands and suppress various interfering signals are of utmost importance. Furthermore, wideband antenna arrays must exhibit consistent radiation patterns over wide frequency ranges to robustly acquire incoming signals for processing. This thesis presents comprehensive design methodologies, practical realization aspects, and novel integration schemes for reconfigurable RF filters and filter-based feed networks for antenna arrays for next-generation broadband transceivers where efficient spectrum usage will be critical. Specifically, versatile and widely reconfigurable multiband and multi-functional operational schemes are developed to produce single-ended and balanced BPFs. A design methodology for feed networks that enable minimum variation in the half-power beamwidth (HPBW) in antenna arrays over ultra-wide bandwidths is presented. The novel concepts within are described through synthesis and analysis, electromagnetic design techniques, and prototypes fabricated in technologies such as microstrip, lumped element, integrated-circuit, or a hybrid combination of them. First, a class of novel quasi-elliptic-type BPF architectures with multiple levels of tuning is introduced. They exhibit state-of-the-art performance including high levels of tunability, selectivity, and quality factors. Next, multi-functional filters that have unique transfer function characteristics such as bandpass-to-bandstop or reflectionless responses are explored. They can reduce the size of a front-end by performing functions of multiple devices within one component. The last group of filtering architectures are focused towards the realization of non-reciprocal BPFs that allow signal transmission in only one direction. These filtering isolators work within a single device without the use of bulky magnets. Next, feed networks that enable minimum HPBW-variation in antenna arrays are addressed. Their elements are selectively fed over frequency based on weighting functions determined by an optimization algorithm. These weighting functions can be approximated with filter transfer functions. Thus, filter-based feed networks are developed for both omnidirectional and directive linear antenna arrays. The networks enable a consistent HPBW over the widest frequency ranges to date

Covid and care: how a ‘stacked’ care system could help places like Hackney

The weakness of local support networks, already cut to the bone, has been cruelly exposed by the pandemic. The LSE’s COVID and Care Research Group looks at the situation in Hackney and explains how an alternative ‘stacked’ care system could help

Reconceptualising well-being: social work, economics and choice

In this paper we examine the intersection of well-being, agency and the current political and economic structures which impact on social work with adults and in doing so contribute to ‘interpreting and mapping out the force fields of meaning production’ (Fornäs, Fredriksson & Johannisson 2011: 7). In it we draw upon Sointu’s (2005) work which identified the shift from conceptualising well-being in terms of ‘the body politic’ to conceptualising it in terms of ‘the body personal’ and identified parallels with understanding well-being in English social work. There has been a shift in the nature of social work in the United Kingdom in how the question of agency has been addressed. For many years this was through the traditional notion of autonomy and self-determination (Biestek 1961) and later collective approaches to welfare and services (Bailey & Brake 1975). The development of paradigms of mainly personal empowerment in the 1980s and 1990s (Braye & Preston-Shoot 1995) saw social work become less associated with collective engagement in welfare and more concerned with the enhancement of individual well-being (Jordan 2007). Whilst the rhetoric of well-being, in contemporary English social work, continues to include autonomy and self-determination, this is focused primarily upon the narrower concepts of independence and choice (Simpson 2012). The UK Department of Health’s A Vision for Adult Social Care: Capable Communities and Active Citizens (DoH 2010) is the template for national social care policy to which all Local Authorities in England had to respond with an implementation plan. This paper draws on a documentary analysis of two such plans drafted in 2012 in the wake of an ‘austerity budget’ and consequent public expenditure reductions. The analysis considers the effect of economic imperatives on the conceptualisation of individual choices and needs in the context of Local Authorities’ responsibilities to people collectively. A concept of ‘reasonableness’ emerges, which is used to legitimize a re-balancing of the ‘body personal’ and the ‘body politic’ in the concept of well-being with the re-emergence of an economic, public construction. Our discussion considers why this is happening and whether or not a new synthesised position between the personal and political is being developed, as economists and policy makers appropriate well-being for their ends

The Mouse Cer1 (Cerberus related or homologue) Gene Is Not Required for Anterior Pattern Formation

AbstractCer1 is the mouse homologue of the Xenopus Cerberus gene whose product is able to induce development of head structures during embryonic development. The Cer1 protein is a member of the cysteine knot superfamily and is expressed in anterior regions of the mouse gastrula. A segmental pattern of expression with nascent and newly formed somites is also seen. This suggests an additional role in development of the axial skeleton, musculature, or peripheral nervous system. Xenopus animal cap assays and mouse germ-layer explant recombination experiments indicate that the mouse protein can act as a patterning molecule for anterior development in Xenopus, including induction of Otx2 expression, and suggest it may have a similar role in mouse development. However, we present here genetic data that demonstrate that Cer1 is not necessary for anterior patterning, Otx2 expression, somite formation, or even normal mouse morphogenesis

Stretched during COVID, Britain’s social infrastructure needs an urgent boost

Besides ‘the economy’ and ‘health’ lies a neglected area of human life during the pandemic: social infrastructures. These vital links, sustained by families and communities, now need to be a priority. The LSE COVID and Care Recovery Group call for both urgent and long term help for voluntary and community groups

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 µm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures

Holographic optical trapping

Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps useful for capturing, moving and transforming mesoscopic objects. Through a combination of beam-splitting, mode forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. With nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps offer extraordinary access to the microscopic world and already have found applications in fundamental research and industrial applications.Comment: 8 pages, 7 figures, invited contribution to Applied Optics focus issue on Digital Holograph

A Comparison of the Effect of Intermittent and Continuous Infusion of Meropenem on the Prevalence of Nausea in Pediatric Cystic Fibrosis Patients

Cystic Fibrosis (CF) is a genetic disease, leading to changes of membrane secretions causing obstruction of smaller airways. CF patients often develop pulmonary infections and require antibiotic treatment. Meropenem is a broad spectrum beta lactam that acts by lysing microbes through interfering with bacterial cell wall synthesis. Although a safe and effective treatment, data on pediatric patients is limited