DSP compensation for distortion in RF filters

There is a growing demand for the high quality TV programs such as High Definition TV (HDTV). The CATV network is often a suitable solution to address this demand using a CATV modem delivering high data rate digital signals in a cost effective manner, thereby, utilizing a complex digital modulation scheme is inevitable. Exploiting complex modulation schemes, entails a more sophisticated modulator and distribution system with much tighter tolerances. However, there are always distortions introduced to the modulated signal in the modulator degrading signal quality. In this research, the effect of distortions introduced by the RF band pass filter in the modulator will be considered which cause degradations on the quality of the output Quadrature Amplitude Modulated (QAM) signal. Since the RF filter's amplitude/group delay distortions are not symmetrical in the frequency domain, once translated into the base band they have a complex effect on the QAM signal. Using Matlab, the degradation effects of these distortions on the QAM signal such as Bit Error Rate (BER) is investigated. In order to compensate for the effects of the RF filter distortions, two different methods are proposed. In the first method, a complex base band compensation filter is placed after the pulse shaping filter (SRRC). The coefficients of this complex filter are determined using an optimization algorithm developed during this research. The second approach, uses a pre-equalizer in the form of a Feed Forward FIR structure placed before the pulse shaping filter (SRRC). The coefficients of this pre-equalizer are determined using the equalization algorithm employed in a test receiver, with its tap weights generating the inverse response of the RF filter. The compensation of RF filter distortions in base band, in turn, improves the QAM signal parameters such as Modulation Error Ratio (MER). Finally, the MER of the modulated QAM signal before and after the base band compensation is compared between the two methods, showing a significant enhancement in the RF modulator performance

Examining the frequency of dysphagia and the predictive factors of dysphagia that require attention in patients with Parkinson's disease

Introduction. Due to the prevalence of dysphagia in patients with Parkinson's disease (PD) and its complications such as aspiration pneumonia, which is the main cause of death in these patients, PD-related disability can be prevented by early diagnosis and treatment of dysphagia. Objective. The present study was aimed at investigating the frequency of dysphagia in PD patients. Materials and methods. This cross-sectional study included 150 PD patients visiting a Neurology Clinic. The severity of PD was determined based on the Unified Parkinson Disease Rating Scale (UPDRS) and modified Hoen and Yahr (HYS) Scale. The Munich Dysphagia Test-Parkinson's disease (MDT-PD) questionnaire was used to assess dysphagia. Comparisons were made using generalized Fisher exact, Chi-square, ANOVA, and KruskalWallis tests. Predictive factors were analyzed using logistic regression. Statistical analyses were performed at significance level of 0.05. Results. Out of all 150 patients referred to the Clinic, the prevalence of dysphagia requiring attention was 25.3% (n = 38). The patients of the three groups according to the MDT-PD (no noticeable dysphagia, noticeable oropharyngeal, and dysphagia with aspiration risk) had a significant difference only in terms of the PD duration (p 0.001). In the predicting of dysphagia, the longer PD duration (p = 0.011) and homemaker occupation (p = 0.033) were protective factors, while female gender was a risk factor (p = 0.011). Conclusion. The prevalence of dysphagia requiring attention in the studied patients was 25.3%. It decreased with the longer duration of the disease, and its prevalence was lower in homemaker patients, while the odds of dysphagia was 5.8 times higher in women than in men