Miniaturized Inverted-F Antenna with capacitive loading

A miniaturization technique based on capacitive loading is introduced for antenna size reduction. The capacitive Loaded Inverted-F Antenna (CLIFA) can achieve electrical length as low as λ/8. Capacitive loading is realized with a printed parallel plate capacitor, reducing associated manufacturing time and cost. The structure exhibits great simplicity in planar form which makes it easily realized on PCB for handheld devices and mobile systems. By employing switches to control the capacitance, the device has the potential to become frequency reconfigurable. The design of the CLIFA is analyzed and the performance is compared to measured data on prototypes operating at 868 MHz. Performance figures including radiation patterns, efficiency and stored energy are discussed with respect to the size reduction.