Antenna Aperture Tuning with High-Voltage Bulk-CMOS Switch-Based RF Capacitor

A circuit for tuning the aperture of inverted-F antenna (IFA) utilizing a high-voltage RF-switch-based digitally-tunable capacitor in bulk-CMOS technology is demonstrated. The tuning network consists of the 5-bit switchable capacitor and a parallel inductor which are placed at the high-voltage plane of the radiating element with peak RF voltages of 60 V applied across the circuit. The antenna covers low and middle cellular frequency bands with fine tuning steps, providing return loss at the feed point of above 6 dB for more than 90% of the target frequency range. The measured peak reflected second and third harmonics generated by the tuned antenna when driven by the 34 dBm low-band RF signal are −38 dBm and −56 dBm respectively.