Gain enhancement of low-profile, electrically small capacitive-feed antennas using stacked meander lines

The present paper describes the gain enhancement of a small and low-profile linear antenna with capacitive feed (C-feed) using three metallic layers. The antenna has very small leakage current on the outer conductor of the coaxial cable and can easily control the imaginary part of the input impedance. The gain of the stacked three-layer meander line antenna, with the meander line in the middle layer is opposite to that of the other two layers, has increased by around 7 dB compared to the single layered C-feed antenna. The antenna gain is discussed based on simulated and measured results, which demonstrates that the antenna has successfully achieved the impedance and gain for mobile terminals and RFID tags.