A Narrow-Strip Broadband Microstrip Antenna With L-Probe Fed

Theoretical study of a narrow-strip broadband microstrip antenna with L-probe fed is presented in this paper. In order to realize narrow-strip antenna structure (the width is less than 0.22λ), the L-probe is designed at the width side of the rectangle radiating patch. Equivalent transmission line model is then used to analysis the two resonant frequencies which result in a broadband property (-10dB impedance bandwidth of 32%). It is found that for the L-probe fed miscrostrip antenna with relatively high air layer (0.1λ), the termination capacitance of the patch is negligible and the effective dielectric constant is approximate to that of the air. In addition, a simple approximate scheme is proposed to further estimate the lower resonant frequency accurately. Simulated and measured results are carried out to verify the theoretical analysis.