Configurable GPS/GNSS Antenna Module Resistant to RFI Saturation

Abstract

With GPS/Global Navigation Satellite System (GNSS) receivers exposed to greater levels of Radio Frequency Interference (RFI), a potential problem is the saturation of the receiver front end (FE). This problem is further complicated in typical multifrequency receivers by the interfrequency saturation effect. Specifically, any inband RFI targeted to induce FE saturation at only one specific GPS/GNSS frequency, if not properly handled, would potentially impact the reception of the other frequencies. This paper presents the design of an antenna module to detect, identify, and isolate potential RFI to prevent FE saturation including that due to the interfrequency effect. Analysis showed that any specific antenna module configuration with fixed internal components must sacrifice noise figure (NF) performance to increase robustness to RFI saturation, and vice versa. To provide a compact solution to this dilemma and the interfrequency saturation issue, two dynamically configurable antenna modules based on the concept of network topology were proposed for typical dual-frequency GPS/GNSS receivers. Such a solution can adapt to different RFI conditions by operating in corresponding modes resulting in a better NF versus robustness tradeoff. The proposed antenna-module design was validated by experiments with live GPS signals under controlled RFI conditions.