Self-Calibrated Digital Two-Point Modulator for BLE RF Transmitter

Abstract

In this brief, a self-calibrated two-point delta-sigma modulation technique for a CMOS RF transmitter is proposed for use for a voltage-controlled oscillator (VCO) and a delta–sigma modulator in a frequency synthesizer. By using the counter to calibrate the frequency deviation of two-point modulation to the desired value, the gain mismatch between two paths can be completely calibrated by modifying the gain of the VCO path. The frequency modulation therefore guarantees a robust performance against PVT variations without using any additional circuit. This technique is applied to Bluetooth Low Energy (BLE) applications. The proposed Two-Point Modulation achieves error vector magnitude (EVM) of −29.3 dB at 1 Mbps and is implemented in 55 nm CMOS process technology. The area of the chip is 0.28 mm2 and its power consumption is 2.9 mW.