Adaptive self-calibrating image rejection receiver

An adaptive self-calibrating image rejection receiver is described, containing a modified Weaver image rejection mixer and a Digital Image Rejection Processor (DIRP). The blind source-separation-based DIRP eliminates the I/Q errors improving the Image Rejection Ratio (IRR) without the need for trimming or use of power-hungry discrete components. Hardware complexity is minimal, requiring only two complex coefficients; hence it can be easily integrated into the signal processing path of any receiver. Simulation results show that the proposed approach achieves 75-97 dB of IRR.

Design and low-power implementation of an adaptive image rejection receiver

This paper deals with and details the design and implementation of a low-power; hardware-efficient adaptive self-calibrating image rejection receiver based on blind-source-separation that alleviates the RF analog front-end impairments. Hybrid strength-reduced and re-scheduled data-flow, low-power implementation of the adaptive self-calibration algorithm is developed and its efficiency is demonstrated through simulation case studies. A behavioral and structural model is developed in Matlab as well as a low-level architectural design in VHDL providing valuable test benches for the performance measures undertaken on the detailed algorithms and structures.

Design of a power-aware digital image rejection receiver

This paper deals with and details the design of a power-aware adaptive digital image rejection receiver based on blind-source-separation that alleviates the RF analog front-end impairments. Power-aware system design at the RTL level without having to redesign arithmetic circuits is used to reduce the power consumption in nomadic devices. Power-aware multipliers with configurable precision are used to trade-off the image-rejection-ratio (IRR) performance with power consumption. Results of the simulation case studies demonstrate that the IRR performance of the power-aware system is comparable to that of the normal implementation albeit degraded slightly, but well within the acceptable limits.

Miniaturised sharp rejection bandpass filter with reconfigurable bandwidth for UWB applications

A novel, compact and highly selective microstrip bandpass filter with bandwidth reconfigurability for ultra-wideband (UWB) applications is presented. The proposed design uses stepped impedance resonator (SIR) for realization of bandpass filter (BPF) and employs a single varactor diode (BB135-NXP) for the purpose of reconfiguring bandwidth. Additionally, to improve the selectivity between passband edges, a cross-coupling between I/O feed lines is introduced which generated pairs of attenuation poles at each side of the passband. Measurements on a fabricated reconfigurable filter confirm the accuracy of the design procedure. Measured responses show good agreement with simulation. The proposed filter is able to achieve significant size reduction (8.5 mm × 7.1 mm excluding the feeding ports) as compared to the conventional bandpass filters with reconfigurable bandwidth.

On the structure, convergence and performance of an adaptive I/Q mismatch corrector

The I/Q mismatches in quadrature radio receivers results in finite and usually insufficient image rejection, degrading the performance greatly. In this paper we present a detailed analysis of the Blind-Source Separation (BSS) based mismatch corrector in terms of its structure, convergence and performance. The results indicate that the mismatch can be effectively compensated during the normal operation as well as in the rapidly changing environments. Since the compensation is carried out before any modulation specific processing, the proposed method works with all standard modulation formats and is amenable to low-power implementations.

Living and dealing with RF impairments in communication transceivers

This paper provides an overview of the sources and effects of the RF impairments limiting and rendering the performance of the future wireless communication transceivers costly as well as hindering their wide-spread use in commercial products. As transmission bandwidths and carrier frequencies increase effect of these impairments worsen. This paper studies and presents analytical evaluations of the performance degradation due to the RF impairments in terms of bit-error-rate and image rejection ratio. The paper also give highlights of the various aspects of the research carried out in mitigating the effects of these impairments primarily in the digital signal processing domain at the baseband as well as providing low-complexity hardware implementations of such algorithms incorporating a number of power and area saving techniques.

Churchill as Chancellor of the Exchequer (1924–9) and the return to the gold standard

The general election of 29 October 1924 saw Winston Churchill return to Parliament as Constitutionalist MP for Epping after two years in the political wilderness. It also saw Stanley Baldwin swept back to Number 10 on a Conservative landslide. Speculation about whether Baldwin would cement Churchill’s drift from the Liberal fold by offering him office surfaced during the election campaign. Churchill nevertheless thought ‘it very unlikely that I shall be invited to join the Government, as owing to the size of the majority it will probably be composed only of impeccable Conservatives’. [ 1 ] Because of his anti-socialist credentials, his ability to reassure wavering Liberals through his opposition to protectionism – dropped by Baldwin after its rejection in the 1923 general election – and concern he could prove a rallying point for backbench malcontents, there was however much to commend giving Churchill a post. To his surprise, Baldwin offered Churchill the long-coveted office of Chancellor of the Exchequer, briefly held by his father before his ill-conceived resignation in 1887. Having arranged a meeting with his Labour predecessor, Philip Snowden, about outstanding business the new Chancellor set to work. Marking his political transition, a few days later Churchill resigned from the National Liberal Club.

Defining the nation, defining public television: discourses of publics on public service television in post-communist Latvia

Institutional and political economy approaches have long dominated the study of post-Communist public broadcasting, as well as the entire body of post-Communist media transformations research, and the enquiry into publics of public broadcasting has traditionally been neglected. Though media scholars like to talk about a deep crisis in the relationship between public broadcasters and their publics in former Communist bloc countries across Central and Eastern Europe, little has been done to understand the relationship between public broadcasters and their publics in these societies drawing on qualitative audience research tradition. Building on Hirschman’s influential theory of ‘exit, voice and loyalty’, which made it possible to see viewing choices audiences make as an act of agency, in combination with theoretical tools developed within the framework of social constructionist approaches to national imagination and broadcasting, my study focuses on the investigation of responses publics of the Latvian public television LTV have developed vis-à-vis its role as contributing to the nation-building project in this ex-Soviet Baltic country. With the help of focus groups methodology and family ethnography, the thesis aims to explore the relationship between the way members of the ethno-linguistic majority of Latvian-speakers and the sizeable ethno-linguistic minority of Russian-speakers conceptualize the public broadcaster LTV, as well as understand the concept of public broadcasting more generally, and the way they define the national ‘we’. The study concludes that what I call publics of LTV employ Hirschman’s described exit mechanism as a voice-type response. Through their rejection of public television which, for a number of complex reasons they consider to be a state broadcaster serving the interests of those in power they voice their protest against the country’s political establishment and in the case of its Russian-speaking publics also against the government’s ethno-nationalistic conception of the national ‘we’. I also find that though having exited from the public broadcaster LTV, its publics have not abandoned the idea of public broadcasting as such. At least at a normative level the public broadcasting ideals are recognized, accepted and valued, though they are not necessarily associated with the country’s de jure institutional embodiment of public broadcasting LTV. Rejection of the public television has also not made its non-loyal publics ‘less citizens’. The commercial rivals of LTV, be they national or, in the case of Russian-speaking audiences, localized transnational Russian television, have allowed their viewers to exercise citizenship and be loyal nationals day in day out in a way that is more liberal and flexible than the hegemonic form of citizenship and national imagination of the public television LTV can offer.