Analysis of Antenna Performance Degradation due to VCO Source Using Active S-Parameters

This paper proposes a method to analyze antenna performance degradation due to electromagnetic interference (EMI) between an antenna and a noise source using active scattering $(S)$ parameters. The victim is a printed planar inverted-F antenna (PIFA) and the noise source over the victim is high frequency signals coming from a voltage controlled oscillator (VCO) via a loop shaped transmission line. Operating the VCO distorts the return loss of nearby antenna, which results in the degradation of the antenna performance. The excitation power of noise source was measured by probing the power of veo circuit, and were used for the input in the active $S$ -parameters calculations. The validity of the proposed method was confirmed by the good agreement between the simulated and measured results.