A Low-Power Edge-Combining Transmitter Using Quadrature Signals for FSK Modulation

A low-power transmitter is proposed that applies edge-combining not only for frequency multiplication but also for quadrature signal generation. A phase-selection modulator uses the quadrature signals for frequency modulation, where frequency-shift keying is emulated by switching the quadrature signals according to the desired frequency deviation. Additionally, the selection modulator can interpolate eight auxiliary phases that enhance the spectral performance of the frequency modulation. The transmitter was fabricated in a 180nm CMOS process. The target radio frequency in the 868MHz ISM band is generated using an efficient switched-mode edge-combining power amplifier with a drain efficiency of 24%, while the transmitter operates at a frequency of 217MHz to reduce power consumption. This transmitter works without external components and achieves a high overall power efficiency of 5% with an RF output power of -7dBm and a transmitter power consumption of 3.9mW in an area of 0.94mm(2).