Measurement and Evaluation Method based on Under-sampling of High-Frequency Wide-Band Radio Signal

Abstract

Radio communication is using signals of higher and higher frequency than ever, and the frequency bandwidth of radio signals is also increasing. Measurement instruments need to measure in-phase and quadrature components of wide-band radio signals with a high sampling frequency. However, these measurement instruments tend to be costly and have low resolution. The system presented here uses under-sampling to measure in-phase and quadrature components with a low sampling frequency and converts them to a low-frequency image signal. This approach has not been used before because in-phase and quadrature components randomly change. In this paper, we show measurement and evaluation results obtained with this system for a continuous QPSK signal and a burst QPSK signal. These results showed good agreement with measurement and evaluation results using real-time sampling, suggesting the possibility of developing measurement instruments that can measure wide-band radio signal with low cost and high resolution.