RF Frequency Identification Method Using Phase Differences of Clock and Undersampled Output Signals of Two Sample-and-Hold Circuits

This study proposes a radio frequency (RF) frequency identification method using phase differences between the clock and undersampled output signals of two sample-and-hold (S/H) circuits. Two S/H circuits are arranged in parallel, with their clock signals set to have similar frequencies but different phases. The input frequency of the S/H circuits is represented using an integer ${n} _{i}$ , the given clock frequency, and the measured output frequency of the S/H circuits. This integer ${n} _{i}$ is uniquely determined by the phase difference between the measured output signals and the set phase difference between the clock signals of the two S/H circuits. The proposed method can identify the input frequency through a straightforward calculation, which is applied to each frequency component of the output signals of the S/H circuits in cases of multiple input signals. Consequently, the proposed method allows for the calculation of the frequencies of multiple input signals independently, without increasing the measurement time associated with fast Fourier transform (FFT) processes or the scale of the RF circuit. Experimental results from a prototype with multiple continuous wave (CW) and burst (pulse) input signals demonstrate that the proposed method can accurately identify an unknown input frequency.