Dual Phase-Locked Loop Design for Wireless Stable Radio Frequency Transmission

A dual phase-locked loop structure for wireless stable radio frequency is proposed in this letter. The noise introduced by free space is suppressed by the phase-locked loop filtering function and phase conjugation module. Backscattering is avoided by regenerating different radio frequency signals at the local end and remote end via dual phase-locked loop. Furthermore, the influence of atmospheric conditions such as temperature, humidity and pressure on the performance of the system is analyzed. Experimental validation is performed in a 15 m outdoor wireless link with frequency instability of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${3.8} \mathbf {\times } {10}^{\mathbf {-}{14}}$ </tex-math></inline-formula> at \text {1}s and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${4.4} \mathbf {\times } {10}^{\mathbf {-}{17}}$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${10}^{{4}}$ </tex-math></inline-formula>s. This design can provide a reference for the construction of wireless frequency synchronization networks.