This letter presents, for the first time, a new filter-enhanced linearity measurement technique using a dual-band and dual-mode filter. While traditional two-tone linearity tests are simple and effective, their ultimate performance is determined by the quality (dynamic range and noise floor) and cost of the employed equipment. On the other hand, the proposed method consists of a simple conventional single-tone test facilitated by a low-cost appropriately designed bandstop filter (BSF). In particular, the employed dual-band/dual-mode absorptive BSF suppresses the fundamental frequency by over 35 dB (absorptive notch) and the second harmonic by over 25 dB (reflective notch), allowing for accurate measurement of the third harmonic, and hence, IP3. The proof-of-concept system is demonstrated at 2 GHz. The filter absorbs with better than 20 dB of reflection the excitation signal at f0=2f_{0}=2 GHz and reflects the signal at 2f0=42f_{0}=4 GHz. With just the insertion of the presented filter and without improving the measurement equipment, we demonstrate an improvement of over 12.7 dB in the IP3 characterization to a maximum of 81 dBm. We also demonstrate the ability to conduct this test with just a low-cost power detector in lieu of a spectrum analyzer leading to a simple scalable measurement technique.

中文翻译：

---

双频段双模滤波器增强线性测量


这封信首次提出了一种使用双频带和双模滤波器的新型滤波器增强线性测量技术。虽然传统的双音线性测试简单有效，但其最终性能取决于所用设备的质量（动态范围和本底噪声）和成本。另一方面，所提出的方法由简单的传统单音测试组成，该测试由适当设计的低成本带阻滤波器（BSF）促进。特别是，所采用的双频/双模吸收 BSF 可将基频抑制超过 35 dB（吸收陷波），将二次谐波抑制超过 25 dB（反射陷波），从而可以精确测量三次谐波，因此，IP3。该概念验证系统在 2 GHz 下进行了演示。滤波器以优于 20 dB 的反射吸收 f0=2f_{0}=2 GHz 的激励信号，并反射 2f0=42f_{0}=4 GHz 的信号。只需插入所提出的滤波器并且无需改进测量设备，我们就证明 IP3 特性改善超过 12.7 dB，最高可达 81 dBm。我们还展示了仅使用低成本功率检测器代替频谱分析仪进行此测试的能力，从而实现了简单的可扩展测量技术。