Variable Time-Step 2.5-15 GHz Phase Modulator with Pre-Distortion for Outphasing Transmitters

Radio transmitters for 5G and beyond communication employ high signal bandwidths and carrier frequencies, setting stringent requirements on the design of transceiver circuits in terms of timing and complexity. Phase modulators act as information encoders as well as delay lines for accurate timing compensation circuits. In this paper we present a configurable variable time-step 2.5-15 GHz 7-bit phase modulator with non-linearity pre-distortion and calibration capabilities. The proposed design exhibits highly linear operation and uses mixed-mode design approach with analog phase modulator and digital binary-to-unary unit for calibration and predistortion. The proposed design is implemented in 22-nm CMOS and occupies 0.68 mm² die area. Simulations across process-voltage-temperature variations indicate consistent dynamic non-linearity (DNL) performance. The design reaches a worst-case DNL performance of 0.43 LSB (least-significant-bit) at 15 GHz operating frequency.