The theoretical limit for small antenna performance that was derived decades ago by Wheeler and Chu governs design tradeoffs size, bandwidth, efficiency. Theoretical guidelines have also been other details of such as permittivity, aspect ratio, even the nature internal structure antenna. In this paper, we extract analyze experimental data from a large body published designs to establish several facts not previously demonstrated: (1) efficiency are validated all available evidence. (2)...

Frequency independent fast-wave (FW) propagation with phase velocity greater than the speed of light can be ideally realized in a dielectric medium whose relative permittivity is positive, but less 1. Conventionally, FW implemented by non-TEM waveguides or antiresonance-based metamaterials, which suffers from narrow bandwidth due to dispersion. In contrast, non-Foster circuits provide brand new method for reducing dispersion so as broaden bandwidth. This paper demonstrates broadband...

Non-Foster matching networks can overcome the gain-bandwidth limitations of passive small antennas, but at cost increased noise generated by active circuit. Gain and measurements a non-Foster matched loop antenna were compared with those to quantify improvement in received signal-to-noise ratio (SNR) matching. The average gain 7 dB from 30-135 MHz was accompanied an added 8.9 dB, indicating that did not provide any SNR antenna. These results led study various sources receiving system. Noise...

Parasitic arrays can generate steerable patterns using tunable reactive loads at the parasitic elements to provide required phase for scattered radiation. However, radiation that is coupled and reflected by attached has a frequency dependent delay, leading beam/null squint effect limited instantaneous squint-free bandwidth. In this paper, we introduce technique eliminating dependence non-Foster loads, whose reflection positive dispersion slope cancel negative associated with propagation...

A non-Foster matching network has been designed for a small cylindrical slot antenna, and its broadband capability examined at varying signal power levels. It observed that the circuit (NFC) impedance changes considerably as increases, thus reducing well introducing stability problems. To analyze true advantage in transmit applications, third-order intermodulation output intercept point (OIP3) gain-bandwidth product of matched antenna have compared with unmatched when both are attached to...

The absorbing performance of a nonlinear waveform‐dependent metasurface with pulsed signals is demonstrated. periodic structure containing diodes, capacitors and resistors. These enable us to first rectify high‐power incoming signal static field, then store the energy during illumination dissipate it before next pulse comes in. incident pulses contain finite width spectrum around 4.2 GHz. By using metasurface, absorption that depends on both power duty cycle measured. measurements...

Electrically small antennas have a theoretical limit to the maximum bandwidth-efficiency product that can be achieved, as derived by Wheeler and Chu. This overcome using non-Foster matching (active matching), is shown in this paper for an electrically loop antenna. A floating negative inductor was simulated full network simulation demonstrates bandwidth of antenna increases 2.9 times Wheeler-Chu limit.

A new non-dispersive tunable reflection phase shifter is introduced based on the artificial magnetic conductor (AMC) loaded with non-Foster circuits (NFCs). An AMC structure circuit model extracted and possibility of mitigating its intrinsic strong dispersion discussed by loading it both negative capacitance inductance. The NFC designed to produce inductance highly accurate, scalable measurement-based models, co-simulated a realistic AMC. numerical results are in good agreement analysis show...

In this paper, a tunable negative capacitor with effective capacitance ranging from -7pF to -12pF was designed and tested. This simulated as periodically attached microstrip line superluminal propagation observed. Based on phase matching condition, such acts leaky wave antenna without the problem of beam squint. Further, we use capacitors control radiation angle antenna.

A non-Foster matching network has been designed and implemented for a given antenna impedance. The measured results show broadband bandwidth which is around seventeen times the obtained from passive matching. Further, efficiency of general matched over an unmatched studied by analyzing signal to noise ratio (SNR) improvement in received signals. In order obtain improved SNR with matching, upper limit on circuit derived. our then analyzed.

Non-Foster circuits (NFCs) can overcome bandwidth and performance limitations of passive antennas metamaterial structures. However, these active have nonlinear transistors which introduce undesirable effects at high signal power levels. A non-Foster matching network has been designed for a small loop antenna, its broadband capability examined varying It observed that the NFC impedance changes considerably as increases, thus reducing well introducing stability problems.

If we are limited to rearranging passive materials such as dielectrics and metals, then the performance of antennas, artificial materials, other electromagnetic structures that build will always be determined by same fundamental limitations affect today's designs. By including active circuits, it is possible exceed devices not otherwise possible. One example a thin, broadband leaky wave antenna free beam squint. This structure can also used broadband, electrically thin cloaking structure....

Non-Foster networks are those whose reactance has a negative slope with frequency, and can thus overcome bandwidth limitations of many passive systems using their unique impedance phase properties. The design parameters convertor circuit (circuit configuration, transistor bias) used to generate non-Foster impedances will depend on the load at output circuit, frequencies operation requirements pertaining specific application (such as low noise or high linearity). Insights into design,...