Abstract-Development of a low-power, small-size transmitter is needed for wireless sensor networks.An effective way to reduce power consumption is to reduce the operating time in a voltage-controlled oscillator. In this study, a 2.4 GHz on-off keying (OOK) transmitter circuit is designed and implemented with an electrically small antenna using a left-handed transmission line. The transmitter circuit was fabricated with a standard 0.18 µm CMOS technology, while the antenna was fabricated with a 3.0×4.5 cm printed circuit board, chip capacitors, and chip inductors. Measured output power was -6.8 dBm with a power consumption of 3.59 mW when the baseband signal was always "high". The power consumption was reduced to 1.96 mW for the baseband signal with a mark ratio of 0.5.