The Design of All-Digital Polar Transmitter Based on ADPLL and Phase Synchronized ΔΣ Modulator

An improved architecture of polar transmitter (TX) is presented. The proposed architecture is digitally-intensive and mainly composed of an all-digital PLL (ADPLL) for phase modulation, a 1-bit low-pass delta sigma ΔΣ modulator for envelop modulation, and a H-bridge class-D power amplifier (PA) for differential signaling. The ΔΣ modulator is clocked using the phase modulated RF carrier to ensure phase synchronization between the amplitude and phase path, and to guarantee the PA is switching at zero crossings of the output current.