JamCam: A camera-integrated GNSS receiver for spatial detection of radio frequency interference sources

This paper presents a Global Navigation Satellite System (GNSS) array-antenna receiver which is capable of generating source-maps of Radio Frequency Interference (RFI) to be superimposed to real-world pictures obtained from a camera. The principle is similar to the acoustic camera which is used for localization of acoustic noise sources in an image or a video sequence. Source-map generation is generally based on Direction-of-Arrival (DoA)-estimation techniques. In case of the GNSS-receiver, the Multiple Signal Identification and Classification (MUSIC) technique has been adopted for spectral DoA-estimation. Amplitudes in the spectrum indicate the DoA of RFI-sources depending on azimuth and elevation angles in the hemisphere above the array-antenna. These coordinates are transferred into cartesian image coordinates and an overlay image is generated with colors reflecting the shape of the spectrum. Afterwards, this image is superimposed to a grayscale picture obtained from the camera and RFI-sources can be visualized in the image. In this context, the paper addresses issues for online calibration of the array-antenna and static calibration of the camera. An Field Programmable Gate Array (FPGA)-based demonstrator is presented and first results from testing the receiver in real-time in an anechoic chamber are discussed.