Hybrid-DPLL-based constant-envelope modulator for Internet-of-Things chipsets

A constant-envelope modulator is presented for Internet-of-Things (IoT) wireless connectivity technologies such as Bluetooth Low-Energy (BLE) and IEEE 802.15.4 ZigBee. It is based on the recently introduced hybrid digital phase-locked loop (HDPLL). It features direct frequency modulation of a digitally controlled oscillator (DCO) and a 2nd-order Delta-Sigma (ΔΣ) mixed-signal closed-loop phase/frequency detector (PFD). The ΔΣ PFD employs charge-pump (CP) PLL front end components for analog quality phase-error detection and a 1st-order ΔΣ ADC with dynamically adjusted digitization resolution. Digital requantization and noise cancellation facilitate low-power analog implementation. The inherent capability of the ΔΣ PFD to provide digital frequency error detection feedback allows for robust HDPLL-based TX self-calibration against the process-voltage-temperature (PVT) variations of its analog components.