Synchronization is a fundamental enabler for low-power backscatter communication systems, where passive or semi-passive tags modulate ambient RF signals for ultra-low-power data transfer. In this survey, we review recent advances in synchronization techniques across Bluetooth Low Energy (BLE), Long-Term Evolution (LTE), and WiFi-based backscatter platforms. We categorize existing methods by their synchronization granularity, accuracy, compatibility, and power cost. We then compare representative systems including PassiveBLE, Bitalign, LScatter, SyncLTE, LiTEfoot, SyncScatter, and BiScatter, highlighting design trade-offs and performance metrics. Furthermore, we delve into the trade-offs between high throughput and low power synchronization, examining key approaches and challenges such as the balance between throughput, synchronization accuracy, and power consumption in various backscatter systems. Finally, we discuss open challenges and outline future directions toward scalable, secure, and ultra-low-power backscatter synchronization.