Bandpass electromechanical sigma-delta modulator

Ph.DDOCTOR OF PHILOSOPH

Bandpass delta-sigma modulators for radio receivers

This thesis concerns discrete-time (DT) bandpass (BP) ΔΣ modulators targeted for intermediate frequency (IF) analog-to-digital (A/D) conversion in radio receivers. The receiver architecture adopted has to be capable of operating with different radio frequencies, channel bandwidths, and modulation techniques. This is necessary in order to achieve an extensive operating area and the possibility of utilizing a local mobile phone standard or a standard suitable for a specific service. The digital IF receiver is a good choice for a multi-mode and multi-band mobile phone receiver, because the signal demodulation and channel filtering are performed in the digital domain. This increases the flexibility of the receiver and relieves the design of the baseband part, but an A/D conversion with high dynamic range and low power dissipation is required. BP ΔΣ modulators are capable of converting a high-frequency narrow band signal and are therefore suitable for signal digitization in an IF receiver. First, the theory of BP ΔΣ modulators is introduced. It has been determined that resonators are the most critical circuit blocks in the implementation of a high performance BP ΔΣ modulator. Different DT resonator topologies are studied and a double-delay (DD) resonator is found to be the best candidate for a high quality resonator. A new DD switched-capacitor (SC) resonator structure has been designed. Furthermore, two evolution versions of the designed SC resonator are presented and their nonidealities are analyzed. The three designed DD SC resonator structures are a main point of the thesis, together with the experimental results. Five different DT BP ΔΣ modulator circuit structures have been implemented and measured. All three of the designed SC resonators are used in the implemented circuits. The experimental work consists of both single-bit and multi-bit structures, as well as both single-loop and cascade architectures. The circuits have been implemented with a 0.35 μm (Bi)CMOS technology and operate with a 3.0 V supply. The measured maximum signal-to-noise-and-distortion ratios (SNDRs) are 78 dB over 270 kHz (GSM), 75 dB over 1.25 MHz (IS-95), 69 dB over 1.762 MHz (DECT), and 48 dB over 3.84 MHz (WCDMA) bandwidths using a 60 MHz IF signal.reviewe

A Systematic Review and Meta-Analysis of the Incidence of Injury in Professional Female Soccer

The epidemiology of injury in male professional football is well documented and has been used as a basis to monitor injury trends and implement injury prevention strategies. There are no systematic reviews that have investigated injury incidence in women’s professional football. Therefore, the extent of injury burden in women’s professional football remains unknown. PURPOSE: The primary aim of this study was to calculate an overall incidence rate of injury in senior female professional soccer. The secondary aims were to provide an incidence rate for training and match play. METHODS: PubMed, Discover, EBSCO, Embase and ScienceDirect electronic databases were searched from inception to September 2018. Two reviewers independently assessed study quality using the Strengthening the Reporting of Observational Studies in Epidemiology statement using a 22-item STROBE checklist. Seven prospective studies (n=1137 professional players) were combined in a pooled analysis of injury incidence using a mixed effects model. Heterogeneity was evaluated using the Cochrane Q statistic and I2. RESULTS: The epidemiological incidence proportion over one season was 0.62 (95% CI 0.59 - 0.64). Mean total incidence of injury was 3.15 (95% CI 1.54 - 4.75) injuries per 1000 hours. The mean incidence of injury during match play was 10.72 (95% CI 9.11 - 12.33) and during training was 2.21 (95% CI 0.96 - 3.45). Data analysis found a significant level of heterogeneity (total Incidence, X2 = 16.57 P < 0.05; I2 = 63.8%) and during subsequent sub group analyses in those studies reviewed (match incidence, X2 = 76.4 (d.f. = 7), P <0.05; I2 = 90.8%, training incidence, X2 = 16.97 (d.f. = 7), P < 0.05; I2 = 58.8%). Appraisal of the study methodologies revealed inconsistency in the use of injury terminology, data collection procedures and calculation of exposure by researchers. Such inconsistencies likely contribute to the large variance in the incidence and prevalence of injury reported. CONCLUSIONS: The estimated risk of sustaining at least one injury over one football season is 62%. Continued reporting of heterogeneous results in population samples limits meaningful comparison of studies. Standardising the criteria used to attribute injury and activity coupled with more accurate methods of calculating exposure will overcome such limitations