ON-CHIP ANTENNAS can be used in applications from radio-frequency-identification (RFID) tags to RF sensors/radars. Gallium arsenide (GaAs) has been the most commonly used substrate in many of these applications. Yet active RF devices are expected to increasingly turn to silicon for its low cost, high integration and other advantages. Many researchers have sought to fabricate antennas on a silicon substrate. At China's Shanghai Jiao Tong University, two onchip slot antennas in 0.18-m CMOS have been presented by Liang Jiang and Junfa Mao from the Center for Microwave and RF Technologies and Wen-Yan Yin from the School of Electronic Information and Electrical Engineering.

The two antennas resonate near 30 GHz with widths of 10 and 100 m in standard 0.18-m CMOS. The researchers measured the forward transmission (S21) between the two 10-m-width and two 100-m-width slot antennas with ~3 mm distance through free space. See "On- Chip Slot Antenna in 0.18 m CMOS for Wireless Application," Microwave and Optical Technology Letters, May 2008, p. 1187.