In this work, the authors report the operation of a cylindrical dielectric resonator antenna (CDRA) in the high gain HEM13δ mode, for the first time. This mode, excited with a standard microstrip slot, radiates in the broadside direction with gain in the range of 8−10 dBi. It is shown that through feed optimization, the HEM13δ mode can be excited dominantly by suppressing the fundamental HEM11δ mode of the CDRA. Detailed simulation studies show that the HEM13δ mode is supported by cylindrical dielectric resonators with an aspect ratio (radius to height ratio or a/d) >1, and it resonates at a frequency approximately 2.2 times that of the fundamental HEM11δ mode. The above features of the HEM13δ mode CDRA can be used as approximate design rules. For a CDRA with dielectric constant ɛr = 24, diameter 2a = 19.43 mm, and height d = 7.3 mm (a/d = 1.3), the HEM13δ mode is excited at 6.125 GHz with a peak gain of 10.14 dBi in simulation. Corresponding values from prototype measurement are 5.981 GHz and 9.62 dBi, respectively for the resonant frequency and the gain, verifying the simulation.

There has been wide-spread use of plane wave theory in muffler design in industry. However, This has led to an underestimation of acoustical performances at higher frequencies. To overcome the above drawback, the finite element and boundary element methods have been developed. Nevertheless, the time consumed in calculating the noise level is unacceptable. Moreover, considering the acoustical effect and necessity of space-constrained situation in industry, a compact design of reverse mufflers which may improve the acoustical efficiency is then proposed.

In this paper, a numerical assessment of rectangular mufflers hybridized with straight/reverse chambers using eigen function, four-pole matrix, and genetic algorithm under limited space is developed. Before the optimization is performed, an accuracy check of the mathematical models for the muffler will be carried out. Results reveal that the noise reduction will increase when the number of chambers increases. In addition, the acoustical performance of the mufflers is reversely proportional to the diameter of the inlet/outlet tubes. Also, the TL of the mufflers will be improved when using more number of target tones in the objective function. Consequently, a successful approach in searching optimal shaped rectangular straight/reverse mufflers using an eigen function and a genetic algorithm method within a constrained space has been demonstrated.