The radiance of most objects seen at a distance through the atmosphere is dominated by scattered light of a blue hue that should make the landscape appear predominately blue. However, common experience shows that people can see colors at a distance. A possible explanation of this paradox is that the visual system splits the light into a haze layer and the background landscape. A straightforward mathematical description of this splitting explains the results of a color matching study in the Great Smoky Mountains National Park. In this study, hues of objects seen through haze were found to be constant with changes in optical depth while colorfulness decreased exponentially.

Interference can significantly degrade the performance of global navigation satellite system (GNSS) receivers. Therefore, mitigation methods are required to ensure reliable operations. However, as there are different types of interference, robust, multi-purpose mitigation algorithms are needed. This paper describes the most popular state-of-the-art interference mitigation techniques. The high-rate DFT-based data manipulator (HDDM) is proposed as a possible solution to overcome their limitations. This paper presents a hardware implementation of the HDDM algorithm. The hardware HDDM module is integrated in three different receivers equipped with analog radio-frequency (RF) front-ends supporting signals with different dynamic range. The resource utilization and power consumption is evaluated for the three cases. The algorithm is compared to a low-end mass-market receiver and a high-end professional receiver with basic and sophisticated interference mitigation capabilities, respectively. Different type of interference are used to compare the mitigation capabilities of the receivers under test. Results of the HDDM hardware implementation achieve the similar or improved performance to the state of the art. With more complex interferences, like frequency hopping or pulsed, the HDDM shows even better performance.

This paper presents the overall architecture, first test structure implementations, and measurement results of an integrated GNSS front-end based on intentional path overlay. The front-end ASIC supports simultaneous multiband, multi-system GNSS reception of GPS L5 / Galileo E5 / GLONASS G3 and GPS L1 / Galileo E1 / GLONASS G1 signals with up to 52 MHz bandwidth while using only one common baseband path thanks to an intentional analog signal overlay. Test structures of the RF and baseband parts were realized in a 1.8V, 150nm RF-CMOS technology packaged in a QFN48 housings with full ESD protection. Both chips are described in detail regarding their design and their actual measurement results

This paper presents a general overlay based front-end architecture that enables the joint reception of two signals broadcast in separate frequency bands, sharing just one common baseband stage. The consequences of this overlay in terms of signal quality are analyzed and it is shown that the noise floor superposition results in non-negligible signal degradations. However, it is also demonstrated that these degradations can be minimized by judiciously setting the relative gain between the two signal paths. As an illustration, the analytical optimal path- control expression to combine overlayed signals in an ionospheric- free pseudorange is derived for both Cramer-Rao Lower Bound and practical code tracking parameters