Σχεδίαση ενεργού CMOS μίκτη σε τεχνολογία 65nm

Αντικείμενο της παρούσας διπλωματικής εργασίας είναι η σχεδίαση ενός down conversion ενεργού (τύπου Gilbert Cell) CMOS μίκτη. Στο θεωρητικό μέρος της εργασίας εξηγούμε τη βασική λειτουργία ενός μίκτη, παρουσιάζουμε τις διάφορες κατηγορίες μικτών, με τα πλεονεκτήματα και τα μειονεκτήματά τους, και τέλος, περιγράφουμε τις παραμέτρους με βάση τις οποίες αξιολογούνται οι επιδόσεις κάθε μίκτη. Στο πρακτικό μέρος της εργασίας, ξεκινούμε από ένα βασικό κύκλωμα, εφαρμόζουμε τροποποιήσεις στο βασικό κύκλωμα με στόχο την βελτιστοποίησή του και τέλος, προσομοιώνουμε τη λειτουργία του με τη βοήθεια του σχεδιαστικού πακέτου ADS της Agilent Technologies. Η συχνότητα του RF σήματος εισόδου ήταν 2.5 GHz, η συχνότητα του LO σήματος του τοπικού ταλαντωτή ήταν 2.4 GHz και η συχνότητα του IF σήματος εξόδου 0.1 GHz. Ο μίκτης που σχεδιάστηκε είχε κέρδος μετατροπής (Conversion Gain) 5.85 dB, εικόνα θορύβου μονής πλευρικής ζώνης (Single Sideband Noise Figure) 7.02 dB, ισχύς εισόδου στο σημείο συμπίεσης 1dB -12dbm και ισχύς εισόδου στο σημείο τομής τρίτης τάξης (Input Intercept Point 3) -1dbm.Thesis' objective is the design of a down-conversion active (type: Gilbert Cell) CMOS mixer. The theoritical part of this thesis includes the explanation of the fundamental function of a mixer, the description of various mixer categories with their advantages and their disadvantages and finally, the parameters used for the assessment of any mixer. As regards the implementation part of the thesis, it consists of an initial circuit used as basis, some modifications applied on the initial circuit for optimization purposes and finally, the simulation of the circuit using Advanced Design System 2009 of Agilent Technologies. The frequency of the RF input signal is 2.5 GHz, the frequency of the local oscillator input signal is 2.4 GHz and the frequency of the IF output signal is 0.1 GHz. The conversion gain of the mixer is 5.85 dB, the single sideband noise figure is 7.02 dB, the input power level at 1 dB compression point is -12 dbm and the input power level at intersection point third order is -1 dbm

Determining utility values in patients with anterior cruciate ligament tears using clinical scoring systems

BACKGROUND: Several instruments and clinical scoring systems have been established to evaluate patients with ligamentous knee injuries. A comparison of individual articles in the literature is challenging, not only because of heterogeneity in methodology, but also due to the variety of the scoring systems used to document clinical outcomes. There is limited information about the correlation between used scores and quality of life with no information being available on the impact of each score on the utility values. The aim of this study was to compare the most commonly used scores for evaluating patients with anterior cruciate ligament (ACL) injuries, and to establish corresponding utility values. These values will be used for the interpretation and comparison of outcome results in the currently available literature for different treatment options. METHODS: Four hypothetical vignettes were defined, based on different levels of activities after rupture of the ACL to simulate typical situations seen in daily practice. A questionnaire, including the Health Utility Index (HUI) for utility values, the IKDC subjective score, the Lysholm and the Tegner score, was created and 25 orthopedic surgeons were asked to fill the questionnaire for each hypothetical patient as proxies for all patients they had treated and who would fit in that hypothetical vignette. RESULTS: The utility value as an indicator for quality of life increased with the level of activity. Having discomforts already during normal activities of daily living was rated with a mean utility value of 0.37 ± 0.19, half of that of a situation where mild sport activity was possible without discomfort (0.78 ± 0.11). All investigated scores were able to distinguish clearly (p < 0.05) between the hypothetical vignettes. However, the utility values correlated best with the IKDC subjective score (r = 0.86, p < 0.001) followed by the Lysholm score (r = 0.77, p < 0.001) and the Tegner score (r = 0.77, p < 0.001). CONCLUSIONS: Here we report the correlation between the most commonly used scores for the assessment of patients with a ruptured ACL and utility values as an indicator of quality of life. Assumptions were based on expert opinions to provide a possible transformation algorithm. The IKDC subjective knee score showed the highest correlation to the quality of life (i.e. HUI) in patients with a ruptured ACL. Confirmation of our results is needed by systematic inclusion of a measurement instrument for utility values in future clinical studies beside the already used clinical knee scoring systems

Reconstruction versus conservative treatment after rupture of the anterior cruciate ligament: cost effectiveness analysis

BACKGROUND: The decision whether to treat conservatively or reconstruct surgically a torn anterior cruciate ligament (ACL) is an ongoing subject of debate. The high prevalence and associated public health burden of torn ACL has led to continuous efforts to determine the best therapeutic approach. A critical evaluation of benefits and expenditures of both treatment options as in a cost effectiveness analysis seems well-suited to provide valuable information for treating physicians and healthcare policymakers. METHODS: A literature review identified four of 7410 searched articles providing sufficient outcome probabilities for the two treatment options for modeling. A transformation key based on the expert opinions of 25 orthopedic surgeons was used to derive utilities from available evidence. The cost data for both treatment strategies were based on average figures compiled by Orthopaedic University Hospital Balgrist and reinforced by Swiss national statistics. A decision tree was constructed to derive the cost-effectiveness of each strategy, which was then tested for robustness using Monte Carlo simulation. RESULTS: Decision tree analysis revealed a cost effectiveness of 16,038 USD/0.78 QALY for ACL reconstruction and 15,466 USD/0.66 QALY for conservative treatment, implying an incremental cost effectiveness of 4,890 USD/QALY for ACL reconstruction. Sensitivity analysis of utilities did not change the trend. CONCLUSION: ACL reconstruction for reestablishment of knee stability seems cost effective in the Swiss setting based on currently available evidence. This, however, should be reinforced with randomized controlled trials comparing the two treatment strategies

Efficient algorithms in speech coding

The need for low complexity speech coding algorithms has emerged due to application driven requirements. This may be attributed to the power consumption constraints placed on hand held mobile communication systems and the Electromagnetic Interference emission requirements placed on aU telecommunication products for both home and office use. Electromagnetic Interference emissions are hardware design specific and become prevalent when faster rated hardware is used. Low complexity speech coding algorithms can be implemented on slower DSP processors, thereby making it easier to meet the emission requirements. Slower DSP processors consume less power than faster processors

Is it possible to predict the outcome of an anterior cruciate ligament injury?

This thesis centers on a well-studied cohort of 100 patients, which received a treatment regimen of initial rehabilitation and activity modification to cope with Anterior Cruciate Ligament (ACL) injury. The data, collected prospectively and longitudinally, cover a span of 15 years after initial injury. The overall aim of this thesis is to describe the course of an ACL injury treated with rehabilitation and activity modification and to identify early prognostic factors of both short- and long-term outcome. The methods for evaluating outcome include patient-reported outcome scores — such as Lysholm, Tegner, and KOOS — and plain radiographs to assess radiographic findings of osteoarthritis. Further assessments include clinical laxity tests — such as Lachman and pivot-shift tests — to evaluate clinical instability as a predictor for later ACL reconstruction, as well as lateral radiographs to explore the influence of posterior-inferior tibial slope in ACL injury. The main findings show that approximately 60% of ACL-injured patients can manage without ACL reconstruction by following the treatment algorithm. Most patients in this study were able to resume pre-injury activity level, and their long-term outcome proved comparable to studies of ACL reconstruction. The study also shows that Lachman and pivot-shift tests performed at 3 months post-injury are important prognostic factors regarding the need for reconstruction; however, it is not recommended to use these tests for making decisions about ACL reconstruction in the acute phase. Another prognostic factor is the slope of the medial tibial plateau, which proved steeper in patients injured when participating in contact sports and led to a fourfold increased risk for later reconstruction in flat-sloped knees. Finally, the acute injury mechanism — with a compression-type injury as opposed to a distraction-type injury — appears to influence both the risk for meniscal injuries, not only at index injury but even later, and the need for ACL reconstruction. A compression-type injury further appears to increase the risk for future osteoarthritis, although the presence of multiple confounding factors may blur its true effect. Our results suggest the initial injury mechanism, along with anthropometric variables and clinical laxity tests, can help in predicting the outcome of ACL injury. The high percentage of copers in our study makes the decision of early reconstruction in the clinical setting questionable. Based on the data presented, we recommend at least a 3-month rehabilitation period prior to making a decision about ACL reconstruction

Combining results from hip impingement and range of motion tests can increase diagnostic accuracy in patients with FAI syndrome

Purpose: Clinical examination is an important part in the diagnosis of femoroacetabular impingement (FAI) syndrome. However, knowledge on reliability and validity of clinical diagnostic tests is scarce. The aims were to evaluate the inter-rater agreement and diagnostic accuracy of clinical tests to detect patients with FAI syndrome. Methods: Eighty-one patients (49% women) were recruited. Two experienced raters performed impingement and range of motion (ROM) tests. Three criteria had to be fulfilled for the diagnosis of FAI syndrome: (1) symptoms; (2) CAM and/or Pincer morphology; and (3) being responder to intra-articular block injection. For inter-rater agreement, the Cohen’s kappa statistics were used (0.41–0.60 = moderate, 0.61–0.80 = substantial agreement). For diagnostic accuracy, sensitivity, specificity, positive and negative predictive values were calculated. Results: Anterior impingement test (AIMT), FADIR test and FABER test showed kappa values above 0.6. All passive hip ROM, except extension, had kappa values above 0.4. AIMT and FADIR showed the highest sensitivity, i.e., 80%, with a specificity of 26% and 25%, respectively. Passive hip ROM in internal rotation with neutral hip position had a sensitivity of 29% and a specificity of 94%. Conclusion: The AIMT, FADIR and FABER tests were reliable between two experienced raters, while results from different raters for hip ROM should be interpreted with caution. The AIMT and FADIR test can only be used to rule out patients with FAI syndrome, while evaluation of ROM in internal rotation with neutral position may be more suitable to rule in patients with FAI syndrome. Level of evidence: II