Front-to-back ratio

About: Front-to-back ratio is a research topic. Over the lifetime, 292 publications have been published within this topic receiving 3314 citations.

Performance Analysis of a Dual Cycle Engine with Considerations of Pressure Ratio and Cut-Off Ratio

Abstract: of the cycle are obtained. The results show that if compression ratio is smaller than certain value, the increase of pressure ratio and the decrease of cut-o ratio make the power output bigger. While if compression ratio exceeds certain value, the power output first increases and then starts to decline as pressure ratio and cut-o ratio are increased. With further increase in compression ratio, the power output decreases with increasing pressure ratio and decreasing cut-o ratio. The eects of pressure and cut-o ratios on the variation of the thermal eciency with compression ratio are similar to those for the power output. The results obtained in this work can provide significant guidance for the performance evaluation and improvement of modern high speed compression ignition engines.

Front-to-back ratio improvement of a microstrip patch antenna using an isolated soft surface structure

Abstract: A microstrip patch antenna fabricated on a substrate, shows significant performance degradation by surface waves. Particularly when the patch antenna is printed on high dielectric substrates or thick substrate, its front-to-back ratio is considerably affected. Various solutions for the surface wave suppression such as photonic bandgap (PBG), electromagnetic bandgap (EBG), micromachining technology and complex artificial soft surfaces, which requires considerable area to form a bandgap structure. In microstrip patch antenna design, the size of ground plane is limited. To solve this problem, we propose new isolated soft surfaces structure which does not share the ground plane of a patch. By removing the ground plane edges of the patch and forming soft surfaces within the bare substrate, the front-to-back ratio of a patch antenna significantly improved. A numerical investigation is presented for a patch antenna surrounded by the proposed new soft surface structure and the effectiveness of the soft surface in terms of front-to back ratio improvement is verified by its implementation. It is shown that the broadside gain of a patch antenna can be decreased by about 1 dBi while the backside level can be increased by about 11 dBi. As a result, the improvement for the front-to-back ratio of a patch antenna can be increased to about 10 dB through the use of the proposed new soft surface structure.

Design of a Yagi-Uda antenna by simulated annealing for gain, impedance and FBR

Abstract: A method of using simulated annealing algorithms to optimize the element spacing and lengths of Yagi-Uda antennas is presented Simulated Annealing (SA) is a powerful stochastic global search and optimization method It converges asymptotically probabilistically to a global optimum Yagi-Uda antennas gain is highly sensitive and depend upon numerous parameters and therefore it is difficult to optimize We present a simulated annealing algorithm-based automated antenna optimization system that uses the length and space between elements as optimization variables Our results include Yagi-Uda antennas that have excellent gain, impedance and front to back ratio properties