TIA Design for FMCW LiDAR Systems

This paper presents a design methodology for a transimpedance amplifier (TIA) that emphasizes enhanced power supply rejection ratio (PSRR), specifically tailored for long-distance frequency-modulated continuous-wave (FMCW) LiDAR systems. In these advanced systems, when critical components such as the transmitter, receiver, and optical phase shifters are integrated into a system-on-chip (SoC), the power supply is subject to significant fluctuations. These fluctuations primarily result from the high current switching activities inherent in these components. Given the extremely weak amplitude of the received optical signals, it is imperative that the TIA, serving as the initial stage of signal amplification, possesses a robust ability to reject variations in the power supply to maintain signal integrity. Another critical challenge in TIA design is the rejection of input DC current. Typically, the AC current signal, which carries the desired distance information, is accompanied by a substantial DC current. If left unaddressed, this DC component can saturate the TIA, thereby preventing the accurate amplification of the AC signal. To overcome this, the proposed TIA incorporates a mechanism specifically designed to reject the DC current, ensuring that the amplifier operates within its optimal range and effectively processes the weak AC signal. The proposed TIA architecture not only addresses the DC current rejection but also significantly improves the PSRR, making it highly suitable for the stringent demands of integrated LiDAR systems. Furthermore, the versatility of the proposed TIA design allows it to be applied in other systems that encounter similar challenges with power supply variations and input DC current interference. Detailed post layout simulations conducted using the 0.25-μm IHP standard CMOS process demonstrate that the proposed TIA achieves a substantial improvement in PSRR, with a 30-dB enhancement compared with conventional TIA designs. This performance is maintained even in the presence of input DC current, underscoring the efficacy of the proposed design in real-world applications. The results indicate that the proposed TIA design is a robust and efficient solution for SoC-based FMCW LiDAR systems and other applications requiring high sensitivity and resilience to power supply disturbances.