Generating Test Signals for Noise-Based NPR/ACPR Type Tests in Production

In this article, a low-cost, high-frequency signal generation procedure suitable for Noise Power Ratio (NPR) and Adjacent Channel Power Ratio (ACPR) test is presented. The proposed technique can be implemented with any ATE equipped with a memory block and digital source in conjunction with a high frequency and high attenuation analog filter; hence, a costly external source is not required. The technique consists of digitally encoding the noise signal having the specified power spectrum using pulse-density modulation and recovering the analog stimulus with an analog filter operating in the desired spectrum. The technique is validated by simulation and experimental results. In simulation, both NPR and ACPR stimulus were realized with a 100 dB specification. For NPR test stimulus generation, a notch depth of 60 dB with respect to the noise pedestal was experimentally achieved. The sensitivity of the proposed methodology to jitter is also investigated.