A high-precision digital phase discriminator based on adaptive sampling is proposed for an antenna automatic tuning system. FFT is used to detect the phase. The output signal of the tuning system is a periodic signal with a non-constant frequency. To reduce spectrum leakage, adaptive sampling is employed to realize phase detection of sinusoidal periodic signals in a certain frequency range. In addition, the antenna automatic tuning system outputs non-sinusoidal periodic low-power signals during tuning. By adding a frequency comparison in the adaptive sampling process, the phase detection of non-sinusoidal periodic signal in a certain frequency range is realized. The combination of odd-even frequency division and half-integer frequency division is adopted to reduce the phenomenon of spectrum leakage. A phase discrimination experiment platform is constructed to verify the effectiveness of the proposed phase discriminator. The accordance between the analysis and experimental results further testify to the advantages.

Digital phase discriminator; adaptive sampling; antenna automatic tuning system; non-sinusoidal periodic signal.