Negative-Index Capacitively Coupled Plasmas for Compact Antennas

The increasing demand for miniaturized, wideband, and reconfigurable wireless systems has driven significant interest in electrically small antennas (ESAs). However, conventional ESAs are inherently limited by the gain-bandwidth trade-off, particularly in the low RF range where physical space constraints exacerbate impedance matching challenges. Traditional passive matching networks cannot simultaneously achieve wide bandwidth and efficient matching due to Foster’s reactance theorem. One promising approach to overcoming this limitation is the use of non-Foster matching networks that exhibit an equivalent negative capacitance.

In this context, low-temperature plasmas offer a compelling path forward as they can naturally support negative permittivity regimes, emulating a tunable non-Foster element. In particular, we explore the use of capacitively coupled plasma (CCP) structures engineered to exhibit negative-index behavior in specific frequency bands. These structures enable active and broadband impedance transformation, facilitating wideband matching for ESAs.

This talk will present our progress in the design and experimental realization of negative-index CCPs tailored for antenna miniaturization. We demonstrate how such plasma-enabled networks can compensate for the large capacitive reactance of ESAs over an ultrawide frequency range, resulting in a significant enhancement in bandwidth times radiation efficiency. This approach introduces a novel use case of low-temperature plasmas in a highly demanded applied electromagnetic problem.