Return loss-bandwidth evaluation for electrically small microstrip antennas

Abstract

A method incorporating Bode–Fano integrals is proposed in this paper to evaluate the potential bandwidth of small antennas and provide a particular strategy for bandwidth improvement. The Bode–Fano theory is applied to the equivalent circuit of small microstrip antennas to calculate the maximum achievable return loss-bandwidth. Results of applying this theory to three types of microstrip antennas in $T{M}_{01}$ mode of propagation with defected ground structure (DGS) and defected microstrip structure (DMS) indicate that creating slots on the microstrip patch or ground structure despite their advantages can decrease the potential bandwidth of the antenna. Fano integrals reveal the invariant relation between maximum achievable return loss-bandwidth and overall volume of the antenna validated using the quality factor (Q factor) analysis.

Keywords:

• Microstrip antennas
• bandwidth
• Bode–Fano
• Q factor
• matching network
• antenna model
• slotted antennas

Acknowledgments

The work was supported in part by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to W. Huang (RGPIN-2017-04508 and RGPAS-2017-507962).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported in part by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to W. Huang (RGPAS- 2017-507962,RGPIN-2017-04508).