Abstract
A technique is described to extend the working frequency-band and increase the radiation gain and efficiency of an electrically small antenna (ESA). The geometry of the proposed ESA is in the shape of an “H”structure. A small gap is included at the symmetry of the H-shape structure to embed an inductive load that is used to connect the two halves of the H-shaped antenna. With the lumped element inductor, the bandwidth of the H-shaped antenna is restricted by Chu-lower bound. However, it is demonstrated by analytical analysis and through 3D full-wave electromagnetic simulations that when the inductive load is replaced with negative reactance from a negative impedance converter (NIC) the antenna's bandwidth, radiation gain and efficiency performance can be significantly improved by ~40%, 3.6 dBi and 55%, respectively. This is because NIC acts as an effective interior matching circuit. The resonant frequency of the antenna structure with the inductive element was used to determine the required inductance variation in the NIC to realize the required bandwidth and radiation characteristics from the H-shaped antenna.
Highlights
Miniaturization of electronic circuits has led to numerous wireless applications that have conflicting requirements for their antenna systems [1]–[4]
Radiation performance electrically small antenna (ESA) is limited by its physical dimensions
The theoretical analysis reveals that this is possible by incorporating a frequency dependent negative reactance in the antenna structure, which can be only be accomplished by using an active circuit or negative impedance converter circuit
Summary
Miniaturization of electronic circuits has led to numerous wireless applications that have conflicting requirements for their antenna systems [1]–[4] This has resulted in the demand for electrically small antennas (ESA) that need to be effective and operate over substantial bandwidths. Matching networks based on Non-Foster (NF) have been proposed to overcome the Chu limit [13], [19] This is achieved by using negative inductance and capacitance in a NF matching network, which causes the antenna to resonate. H -shaped antenna based on [21]–[23] where an interior matching network comprising an inductor is incorporated between the two half portions that constitute the H -shaped antenna to realize a low Q-ratio value and broad bandwidth ESA with higher radiation gain and efficiency over its operating frequency band. Increased if the losses are increased, but at a cost of the total radiated power
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