A 433-MHz Wireless Burst-Chirp Modulation Transmitter with Adaptive Duty-Cycle Control and Precharge Mechanism

This paper presents an energy-efficient 433 MHz wireless transmitter with burst-chirp modulation. To compromise the design trade-offs between output power and power consumption, the transmitter (TX) adopts a duty-cycle controlled class-E power amplifier (PA), whose switching duty-cycle ratio is less than 50% Through this method, the impedance transformation ratio at the output of the PA is reduced, thus improving efficiency. Furthermore, a digital controller directly modulates the oscillator, generating chirp pulses. Moreover, the precharge mechanism is proposed to improve settling time, allowing short-pulse data transmission time. The TX IC is fabricated using 180-nm CMOS technology and occupies an active area of 1.73 mm(2). The design achieves 8.71/Mbit normalized system efficiency, while the output power is -1.18 dBm at a 0.8-V supply, and the maximum system efficiency is 45%.