Electrically small oblate spheroidal and spherical antennas in confocal shells with negative permittivity represent perspective antenna design to combine moderately small size, wide bandwidth, high efficiency and power of radiation. However, optimization of the antennas performance parameters imposes contradictory restrictions on permittivity of the shells, electrical size of the antennas, shap...

We developed curved spiral antennas for use in underwater (freshwater) communications. Specifically, these antennas will be integrated in so-called mussel backpacks. Backpacks are compact electronics that incorporate sensors and a small radio that operate around 300 MHz. Researchers attach these backpacks in their freshwater mussel related research. The antennas must be small, lightweight, and ...

A low-cost and portable vector network analyzer (VNA) which covered operating frequency between 1MHz to 3GHz is used for vector reflection coefficient and standing wave ratio (swr) of the various microstrip antennas. This paper presents measurements of various ultra wideband (uwb) microstrip antennas for applications in biomedical field. Selection of antenna is an important key for detection of...

This paper focuses on the S-parameter method that is a basic method for measuring the input impedance of balanced-fed antennas. The basic concept of the method is summarized using the two-port network, and it is shown that the method can be enhanced to the unbalanced antennas using a formulation based on incident and reflected waves. The compensation method that eliminates the influence of a me...

This letter proposes a compact and energy-efficient directional modulation scheme for small power constrained devices (e.g., Internet of Things wireless sensors). The uses uniform circular array monopole antennas, with single radiofrequency chain antenna active at time. antennas can be located in close proximity, offering significant size reduction. Furthermore, the was demonstrated to operate ...

Abstracr We construct simal constellations for differential transmission with multiple basestation antennas. The signals are derived using the theory of fixed-point-free groups and are especially suitable for mobile cellular applications because they do not require the handset to have more than one antenna or to know the time-varying propagation environment. Yet we achieve full transmitter dive...