Full-Wave Analysis and Design of Circular Half-Width Microstrip Leaky-Wave Antennas

Abstract

A half-width microstrip leaky-wave antenna on a circular substrate is proposed and investigated. A microstrip on a circular substrate has a broader bandwidth for free-space leaky-wave radiation than a planar microstrip. A half-width microstrip has similar radiation characteristics to a full-width microstrip, but it does not require complex feeding structures. Full-wave analysis based on the extended spectral domain approach (ESDA) is applied to analyze the propagation characteristics of the circular half-width microstrip. The ESDA accounts for field singularities near a conductor edge of finite thickness and it does not require a virtual boundary to obtain the finite extent of the analytical space. Consequently, the ESDA is more suitable for analyzing leaky-wave structures than other conventional analysis methods. Numerical calculations are performed to determine the characteristics of the leaky-wave radiation from half-width microstrips on circular and semicircular substrates. The leaky radiation elements can be efficiently designed based on these numerical results. Two practical antennas with leaky radiation elements and feeders are designed and implemented. The measured bandwidths of the free-space leaky-wave radiation indicate that these cylindrical antennas have better performances than planar ones and they are in reasonable agreement with theoretical results. The measured radiation patterns with frequency-scanning characteristics also agree well with the simulation results.