Enhancing Dynamic Range of Complex-Ratio Estimation Between Two RF Signals With Time Modulation

A novel method for extending the dynamic range of complex-ratio measurement between two radio frequency (RF) signals is proposed. It relies on adjusting the proportion of the signals in the combined one. By using a single-pole double-throw (SPDT) switch to periodically modulate the two RF signals and analyzing the spectrum of the combined signal, the amplitude ratio and phase difference can be determined. Measurement errors mainly stem from switch isolation limits and strong-to-weak signal interference, and the latter can be mitigated by proportion adjustment. Compared to previous works, the proposed method achieves an improved dynamic range and higher precision while preserving the low complexity of single-channel receiver. A 200 MHz–2 GHz measurement system is built, achieving 65 dB and 360° dynamic ranges with low root mean square errors (RMSEs). Experimental results match the measurements from the vector network analyzer (VNA), validating the effectiveness of the proposed method.