SC-DSB-based Characterization oF RF Circuit Nonlinearity Using IP2 and IP3 Metrics

Abstract

Characterization of nonlinearity in RF circuits is a critical requirement for ensuring the performance, reliability, and spectral efficiency of modern communication and radar systems. Nonlinear effects lead to the generation of intermodulation distortion (IMD), pro-ducing unwanted spectral components that degrade the signal quality and the limit system dynamic range. Intercept point metrics, particularly the second-order intercept point (IP2) and the third-order intercept point (IP3), are widely used to quantify these nonlinear charac-teristics. Conventional measurement techniques typically rely on two-tone excitation; how-ever, such approaches may exhibit limitations related to spectral flexibility, implementation complexity, and measurement efficiency.

This paper presents a novel method for RF circuit nonlinearity characterization based on the use of Suppressed Carrier Double Sideband (SC-DSB) signals as probe sig-nals. The proposed approach enables controlled generation of intermodulation products, allowing precise evaluation of second- and third-order nonlinear behavior through IP2 and IP3 metrics. A theoretical framework based on polynomial modeling of nonlinear systems is developed to describe the formation of spectral components under SC-DSB excitation.

A simulation model of the RF signal chain is implemented, incorporating the SC-DSB signal generation, nonlinear system modeling, and FFT-based spectral analysis. The output spectrum is analyzed to extract fundamental and intermodulation components, ena-bling reliable estimation of intercept points. The obtained results demonstrate that the SC-DSB-based method provides improved control over spectral components and offers a flexi-ble and efficient alternative to conventional two-tone testing for RF nonlinearity characteri-zation. In addition, the proposed approach simplifies the measurement procedure while maintaining high accuracy in intercept point estimation. The method is well-suited for prac-tical implementation in simulation environments and real measurement systems. These ad-vantages make the proposed technique a promising solution for advanced RF system analy-sis and testing applications․