Terminal Antennas in Difficult Environments
6.1 GNSS Antennas and Multipath Environment
The introduction of built-in GPS in portable personal navigation devices (PNDs), especially in mobile phones, has revolutionised the navigation industry. The ever-growing demand for the availability of navigation facilities in these devices has made the GNSS an essential part of modern wireless personal area network (WPAN) and wireless body area network (WBAN) applications. As the only navigation and positioning service provider to the mobile phone industry in recent times, the GPS is discussed in this chapter.
Portable mobile terminals are affected by multipath due to reflections, diffraction and scattering of the incident radio waves. It depends on the structure of the surrounding environment, as shown in Figure 6.1. This phenomenon has been well studied over time. Analysis of this complex and random nature problem is complicated. Statistical modelling is a powerful tool that offers simple and flexible solutions to such problems. A number of researchers have used this approach to study and characterise the multipath effects on mobile terminals and GPS antennas [1–10]. Axelrad et al. have used signal-to-noise ratios (SNRs) to predict and remove multipath errors . Wu and Hsieh have used sidereal filtering of time-series range residual variations based on a least squares model to mitigate the multipath . It requires a comprehensive data set containing multipath delay samples ...