DESIGN AND ANALYSIS OF LOW PROFILE CIRCULARLY POLARIZED ANTENNAS

In the last decade, mobile communication has spread widely and become an essential tool in every day’s life. A tremendous increase in the demand of small Personal Mobile Devices (PMD) has been observed with wide model ranges and applications. This necessitates the design of low profile and compact antennas that can be accommodated in the smaller PMD sizes. This thesis focuses on designing low profile Circularly Polarised (CP) antennas that can be incorporated with these devices. Two types of circularly polarised antennas have been considered; Dielectric Resonator Antennas (DRA) and planar open loop antennas backed by an Artificial Magnetic Conductor (AMC) ground plane. The Elliptical DRA has been considered owing to the simplicity of achieving CP radiation compared to a cylindrical DRA. Several EDRAs have been designed employing a simple conformal strip excitation mechanism. The designed antennas include single and dual band, as well as a wideband CP DRAs. In addition, a low profile elliptical dielectric resonator antenna has been designed using a dielectric constant of ε_r=25. Extremely lower profile CP loop antennas have been designed by incorporating the Artificial Magnetic Conductor (AMC) as a ground plane. Two excitation mechanisms have been employed; the Co-Planar waveguide and the vertical probe feed. A total antenna’s thickness of λ_o⁄48 has been achieved for the probe-fed loop antenna compared to λ_o⁄21.2 that has been reported in the literature and incorporated the square patch AMC. Two artificial magnetic conductor surfaces have been designed; the traditional square patch and a novel AMC. The novel AMC has reduced the antenna’s size by ~28% compared to other antennas, incorporated the square patch AMC given the same thickness using a 4×4 unit cells’ grid. Additionally, a reduction of ~45% has been achieved using a 3×3 grid of the novel unit cell with sufficient matching and axial ratio bandwidths. Furthermore, a CP loop antenna backed by the novel AMC out-performs an identical counterpart placed above the traditional square patches AMC with simulated axial ratio bandwidth of ~10%. Moreover, two dual band AMCs are presented, that are suitable for the L1 and L2 GPS bands. Once more, a pronounced size reduction of ~42% has been attained using the novel dual band AMC unit cells compared to the double square dual band AMC. Several prototypes have been fabricated with close agreement between simulated and measured results. Some results have been verified using another commercial software, HFSS

Metabolic and other morbid complications in congenital generalized lipodystrophy type 4

\ua9 2024 Wiley Periodicals LLC.Morbidity and mortality rates in patients with autosomal recessive, congenital generalized lipodystrophy type 4 (CGL4), an ultra-rare disorder, remain unclear. We report on 30 females and 16 males from 10 countries with biallelic null variants in CAVIN1 gene (mean age, 12 years; range, 2 months to 41 years). Hypertriglyceridemia was seen in 79% (34/43), hepatic steatosis in 82% (27/33) but diabetes mellitus in only 21% (8/44). Myopathy with elevated serum creatine kinase levels (346–3325 IU/L) affected all of them (38/38). 39% had scoliosis (10/26) and 57% had atlantoaxial instability (8/14). Cardiac arrhythmias were detected in 57% (20/35) and 46% had ventricular tachycardia (16/35). Congenital pyloric stenosis was diagnosed in 39% (18/46), 9 had esophageal dysmotility and 19 had intestinal dysmotility. Four patients suffered from intestinal perforations. Seven patients died at mean age of 17 years (range: 2 months to 39 years). The cause of death in four patients was cardiac arrhythmia and sudden death, while others died of prematurity, gastrointestinal perforation, and infected foot ulcers leading to sepsis. Our study highlights high prevalence of myopathy, metabolic abnormalities, cardiac, and gastrointestinal problems in patients with CGL4. CGL4 patients are at high risk of early death mainly caused by cardiac arrhythmias

Metabolic and other morbid complications in congenital generalized lipodystrophy type 4

Morbidity and mortality rates in patients with autosomal recessive, congenital generalized lipodystrophy type 4 (CGL4), an ultra-rare disorder, remain unclear. We report on 30 females and 16 males from 10 countries with biallelic null variants in CAVIN1 gene (mean age, 12 years; range, 2 months to 41 years). Hypertriglyceridemia was seen in 79% (34/43), hepatic steatosis in 82% (27/33) but diabetes mellitus in only 21% (8/44). Myopathy with elevated serum creatine kinase levels (346–3325 IU/L) affected all of them (38/38). 39% had scoliosis (10/26) and 57% had atlantoaxial instability (8/14). Cardiac arrhythmias were detected in 57% (20/35) and 46% had ventricular tachycardia (16/35). Congenital pyloric stenosis was diagnosed in 39% (18/46), 9 had esophageal dysmotility and 19 had intestinal dysmotility. Four patients suffered from intestinal perforations. Seven patients died at mean age of 17 years (range: 2 months to 39 years). The cause of death in four patients was cardiac arrhythmia and sudden death, while others died of prematurity, gastrointestinal perforation, and infected foot ulcers leading to sepsis. Our study highlights high prevalence of myopathy, metabolic abnormalities, cardiac, and gastrointestinal problems in patients with CGL4. CGL4 patients are at high risk of early death mainly caused by cardiac arrhythmias