# A Multi-Channel Data Simulator Based on the Time Unification System
###### Abstract  
In satellite and airborne electro-optical tracking systems, there are numerous processing devices and complex data flows. To ensure the coordinated operation of the system, the multiple devices within the target system must operate under unified time control for data acquisition, computation, and output. This study introduces a multi-channel data simulator based on a time unification system. The complete simulation system includes the host computer, simulator, target system, and time reference generator. The simulator has programmable input and output interfaces for multi-channel protocols and has storage and real-time working modes. In the storage mode, the simulated data are pre-transmitted to the simulator's storage and sent to the target system according to the time reference generator. The simulator simultaneously stores the target system results. In the real-time mode, the host computer generates simulated data based on the target system's results and outputs the data through the simulator in real time. The main contribution of the simulator is that it achieves system-level closed-loop simulation and completes the functional and performance verification of the target system. Through experimental verification, it is found that the simulator can achieve 4.2 Gbps of simulated data transmission and 1.6 Gbps of data reception and storage, with a closed-loop delay of 39.9 us. test equipment; real-time simulation; data simulator; time unification system; FPGA 2024 14 5938 13 June 2024 4 July 2024 5 July 2024 8 July 2024 The time reference generator generates a time reference and provides it to the simulator. The simulated data generator generates simulated data in real time based on the results of the target system. The simulator generates a unified time output, simulated output, and result input. The target system has multiple processing devices, and the simulated inputs of these devices include control signals and data streams. The target system's inputs need to maintain a fixed delay relationship with the time reference input to satisfy the real processing timing of the processing devices, thus achieving time-unified simulation. There are two main implementation methods for the simulator. One method is to send pre-set simulated data to the target system and store the results of the target system for subsequent analysis [7; 8; 9]. This method cannot generate dynamically changing simulated data based on the output of the target system and cannot achieve closed-loop simulation. The other method is to generate the simulated data required by the target system in real time and change the simulated data output at the next moment based on the output result of the simulation system [10; 11; 12; 13; 14]. The dynamic generation of high-speed simulated data requires a large number of calculations and will lead to differences in the data output time across different interfaces. This study proposes a multi-channel data simulator based on a time unification system, which can achieve the real-time closed-loop simulation of the data required for the target system simulation. Simulated data from the source can be pre-generated and uniformly transmitted through the control of a host computer. [PERSON] et al. [7] achieved the simulation of data generated by space-borne sensors, with the simulated data stored using Flash and Compact Flash (CF) cards. However, the data output bandwidth was low due to the storage media, and it lacked synchronized input and result data input, making it impossible to achieve unified timing and closed-loop data simulation. [PERSON] et al. [8] improved the data output bandwidth and the storage capacity of the simulated data by enhancing the storage method. Nevertheless, because the storage and transmission modules communicated via the PCI eXtensions for Instrumentation (PXIe) bus, the output of various interfaces was still asynchronous with the time reference. [PERSON] et al.