【仪测高下】PCB插损和阻抗测试方案

Core Viewpoint - The rapid rise of AI technology has led to an exponential increase in the demand for data bus throughput in servers and computing devices, necessitating upgrades in PCIe standards to meet these requirements [1][2]. Group 1: PCIe Standards and Challenges - PCIe standards have evolved to PCIe 6.0 and 7.0, achieving signal frequencies of up to 128 GT/s and expanding channel configurations from x1 to x16 to facilitate high bandwidth transmission [1][2]. - Higher signal frequencies result in exponential increases in insertion loss, leading to reduced signal amplitude and distortion, while impedance discontinuities in PCB traces can cause signal reflection and timing jitter, impacting signal integrity [1][2]. Group 2: Insertion Loss and Impedance - Insertion loss refers to the power loss due to conductor and dielectric losses as signals pass through PCB transmission lines, typically measured in decibels (dB), with PCIe 5.0 requiring insertion loss not to exceed 0.6 dB at 16 GHz [3]. - Characteristic impedance, determined by the geometric structure and material properties of transmission lines, is typically recommended at 50Ω or 100Ω (differential), with impedance mismatches leading to signal reflection and return loss degradation [5]. Group 3: Testing Methods - Vector Network Analyzers (VNAs) are the preferred instruments for measuring insertion loss, allowing direct comparison of output and input signals to reflect losses [9][11]. - The Delta-L method, developed by Intel, enhances measurement accuracy by compensating for fixture effects and impedance mismatches, making it a mainstream method for PCB production testing [12][18]. Group 4: Rohde & Schwarz Testing Solutions - Rohde & Schwarz offers a comprehensive range of vector network analyzers, including models like R&S®ZNA, R&S®ZNB, and R&S®ZNBT, covering frequency ranges from 9 kHz to 110 GHz, catering to diverse testing needs [20]. - The integrated Delta-L functionality in Rohde & Schwarz VNAs allows for efficient insertion loss testing without external computers, streamlining the testing process [21][22]. - The TDR functionality in Rohde & Schwarz VNAs supports various window functions and time-domain enhancement algorithms, displaying both impedance and frequency domain S-parameter information for effective diagnostics [27][29]. Group 5: Future Outlook - Rohde & Schwarz's ZNA/ZNB/ZNL series, equipped with electronic calibration components and built-in impedance testing capabilities, redefine PCB insertion loss and impedance testing standards, addressing the higher demands of future 6G communications and AI server applications [35].