Design and fabrication of 2.4 GHz pre-biased rectifier

A 2.4 GHz rectifier operating in a region of low RF input power was developed. The rectifier has a cross-coupled bridge configuration and is driven by a differential RF input signal. Since a rectifier needs an RF signal higher than the threshold voltage of transistors, we introduced a pre-biasing circuit to compensate for the threshold voltage. A low-voltage digital circuit, subthreshold voltage regulator, and low-power level shifter were introduced for reducing the power consumption of the pre-biasing circuit and increasing the driving voltage for the switches at the same time. The circuit simulations revealed that the pre-biasing circuit was effective in a low RF input power region. However, the output voltage was degraded in a high power region. Then, we combined the pre-biased rectifier in parallel with a non-biased rectifier. Three types of rectifiers consisting of LC matching circuits, three-stage rectifier cells, and biasing circuits were designed and fabricated using a 0.18-mu m mixed signal/RF CMOS process with one poly and six metal layers. The fabricated pre-biased rectifier operated in a region of RF input power of less than -15 dBm, while the non-biased rectifier could not operate in this region. The parallel combination of pre-biased and non-biased rectifiers effectively solved the drawback of the pre-biased rectifier in a high RF input power region

Low-power, small-size transmitter module with metamaterial antenna

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 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 mu m CMOS technology, while the antenna was fabricated with a 3.0 x 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