Built-in self-test and characterization of polar transmitter parameters in the loop-back mode

This paper presents a Built-in self-test (BIST) solution for polar transmitters with low cost. Polar transmitters are desirable for portable devices due to higher power efficiency they provide compared to traditional Cartesian transmitters. However, they generally require iterative test/measurement/calibration cycles. The delay skew between the envelope and phase signals and the finite envelope bandwidth can create intermodulation distortion (IMD) that leads to the violation of the spectral mask and error vector magnitude (EVM) requirements. Typically, these parameters are not directly measured but calibrated through spectral performance analysis using expensive RF equipment, leading to lengthy and costly measurement/calibration cycles. Characterization and calibration of these parameters inside the device would reduce the test time and cost considerably. In this paper, we propose a technique to measure the delay skew and the finite envelope bandwidth, two parameters that can be digitally calibrated, based on the measurement of the output of the receiver in the loop-back mode. Simulation and hardware measurement results show that the proposed technique can characterize the targeted impairments in the polar transmitter accurately.