Radiation Characteristics of A Spiral Antenna with Impedance Matching Circuit

This paper explores the radiation characteristics of a spiral-shaped patch antenna with an additional impedance matching circuit at the feeding network. The proposed spiral antenna which adopts a proximity coupled technique for the excitation is designed on two layers of 0.8 mm thick Roger RO4003C dielectric substrate with the dielectric constant of 3.38 and the loss tangent of 0.05. The impedance matching circuit comprised of interdigital capacitors and meander-lines is positioned between the first and the second layers. The proposed design is then realized for experimental characterization, where-by the results demonstrate that the spiral antenna operates at the center frequency of 3.5 GHz with an S
11
value of –21.5 dB, and has the bandwidth response of 40 MHz with the gain of 1.67 dBi at its center frequency.