Portable Atmospheric Transfer of Microwave Signal Using Diode Laser with Timing Fluctuation Suppression

We demonstrate an atmospheric transfer of microwave signal over a 120 m outdoor free⁃space link using a compact diode laser with a timing fluctuation suppression technique. Timing fluctuation and Allan Deviation are both measured to charac⁃ terize the instability of transferred frequency incurred during the transfer process. By transferring a 100 MHz microwave signal within 4500 s, the total root⁃mean⁃square (RMS) timing fluctuation was measured to be about 6 ps, with a fractional frequency instability on the order of 1 × 10−12 at 1 s, and order of 7 × 10−15 at 1000 s. This portable atmospheric fre⁃ quency transfer scheme with timing fluctuation suppression can be used to distribute an atomic clock ⁃ based frequency over a free⁃space link.