title: Wideband Doppler frequency shift measurement and direction ambiguity resolution using optical frequency shift and optical heterodyning.
abstract: A photonic approach for both wideband Doppler frequency shift (DFS) measurement and direction ambiguity resolution is proposed and experimentally demonstrated. In the proposed approach, a light wave from a laser diode is split into two paths. In one path, the DFS information is converted into an optical sideband close to the optical carrier by using two cascaded electro-optic modulators, while in the other path, the optical carrier is up-shifted by a specific value (e.g., from several MHz to hundreds of MHz) using an optical-frequency shift module. Then the optical signals from the two paths are combined and detected by a low-speed photodetector (PD), generating a low-frequency electronic signal. Through a subtraction between the specific optical frequency shift and the measured frequency of the low-frequency signal, the value of DFS is estimated from the derived absolute value, and the direction ambiguity is resolved from the derived sign (i.e., + or -). In the proof-of-concept experiments, DFSs from -90 to 90 kHz are successfully estimated for microwave signals at 10, 15, and 20 GHz, where the estimation errors are lower than ±60  Hz. The estimation errors can be further reduced via the use of a more stable optical frequency shift module.
authors.forename: Bing
authors.initials: B
authors.lastname: Lu
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
authors.forename: Xihua
authors.initials: X
authors.lastname: Zou
authors.forename: Xianglei
authors.initials: X
authors.lastname: Yan
authors.forename: Lianshan
authors.initials: L
authors.lastname: Yan
authors.forename: Bin
authors.initials: B
authors.lastname: Luo
mesh_terms: D004301:Doppler Effect; D055096:Optical Devices; D055620:Optical Phenomena