This paper presents a comprehensive review of symmetrically shaped antennas in terms of antenna size, dielectric materials, resonating band, peak gain, radiation pattern, simulating tools, and their applications. In this article, flower shape, leaf shape, tree shape, fan shape, Pi shape, butterfly shape, bat shape, wearable, multiband, monopole, and fractal antennas are discussed. Further, a survey of previously reported bandwidth enhancement techniques of microstrip patch antenna like introduction of thick and lower permittivity substrate, multilayer substrate, parasitic elements, slots and notches, shorting wall, shorting pin, defected ground structure, metamaterial-based split ring resonator structure, fractal geometry, and composite right-hand/left-handed transmission line approach is presented. The physics of these techniques has been discussed in detail which is supported by circuit theory model approach.

A common strategy to reduce the cost of a filter is to use a manufacturing technique with an intermediate accuracy and use tuning elements to compensate for the manufacturing errors. However, including tuning elements in the final EM simulations, and tuning the filters after manufacturing, can be quite challenging. In this context, therefore, we review in this paper two powerful filter design procedures based on Aggressive Space Mapping (ASM), and two semi-automatic tuning techniques. As a validation, we describe in detail the design and tuning of two types of filters that are commonly used for both space and ground applications, namely, a six-pole inductive filter in rectangular waveguide, and a more complex five-pole filter based on dual-mode resonators.

An optically transparent ultra-wideband (UWB) Vivaldi antenna with a rectifier circuit is proposed in this paper. The proposed antenna is designed and fabricated on a soda-lime glass substrate with fluorine doped conductive oxide (FTO) as the conductive layer. A radial stub is used for better impedance matching and enhancing the impedance bandwidth of the antenna. It operates over a frequency range of 2–6 GHz with a bandwidth of 4 GHz. It has a directional radiation pattern with a realized peak gain of 2.5 dBi at 4 GHz and simulated radiation efficiency greater than 28%. The transparent antenna is integrated with a rectifier and a matching circuit for radio frequency energy harvesting applications. The rectifier and matching circuit is designed on an FR4 substrate. The fabricated rectenna provided a dc voltage of 140 mV from the ambient environment. The proposed rectenna can be installed in handheld devices that increase the scope of applications in automobiles and mobile communications.

In this paper, a modular waveguide filter platform suitable for educational and prototyping purposes is presented. The waveguide filter platform is dimensioned to work in the F-band (4.9–7.05 GHz). The design of the platform is discussed and versatile application possibilities are shown in many examples. The platform can be used to realize generalized Chebyshev filters with or without cross-couplings by exploiting TE101 and TE102 mode cavities. Transmission zeros can be introduced by the utilization of wires or aperture couplings. Filter topologies based on the extracted pole technique can be examined as well. Small changes in the set-up also allow the realization of a gap waveguide filter, a diplexer set-up as well as filters with frequency-dependent coupling apertures. Most required components can either be purchased cheaply or be manufactured with a three-dimensional printer.