A Delay Calibration Method for the Multi-channel Broadband Microwave Photonic System

In order to solve the problem of multi-channel phase inconsistency in a microwave photonic phased array radar system, a delay calibration method is proposed based on the true delay characteristic of the microwave photonic system. Since the instantaneous bandwidth is usually greater thanGHz for a microwave photonic system, it is difficult to complete phase calibration by phase shifters. Therefore, based on the true delay characteristic, the proposed method ensures the phase consistency of a multi-channel broadband system by optical delay calibration. First, a reference channel is selected and the phase difference between other channels is obtained. Second, according to the relationship between the phase and the optical delay, a phase calibration function is established. Third, to ensure the calibration phase is minimal in the frequency band, an optimal delay calibration function is established. Finally, based on the performance of the actual optical delay device, the calibration delay for all channels is fine-tuned. To verify the effectiveness of this method, a muti-channel microwave system on 6∼18GHz is tested. Before the delay calibration, the phase difference between all channels is greater than 360°. After the delay calibration by the proposed method, the phase difference between all channels is limited to ±20°.