Ch 18. High Sensitivity GNSS

Chapter Overview: This chapter describes how we use the reduced Doppler/Code Delay search space (from A-GNSS) to get high sensitivity in GNSS receivers.

The existence of GNSS in smartphones depends on high sensitivity, because the GNSS antennas are so small, and the signal so weak inside the phone. However, high sensitivity has application far beyond smartphones, sometimes literally far beyond: high sensitivity GNSS receivers are employed in GEO satellites to acquire and track the weak signals transmitted from GNSS satellites on the other side of the Earth. We saw in Chapter 17 how A-GNSS sets the stage for high sensitivity by reducing the acquisition search space. In this chapter we explain how the receiver takes advantage of the reduced search space to integrate longer in each frequency-code search cell.

We describe the analysis of high sensitivity for GPS, and then extend it to show how different signal structures in different GNSS affect receiver complexity, size, cost and power consumption. When it comes to sensitivity, all GNSS signals are not created equal and what’s best is not immediately obvious. As you will see, simpler may be better; and more complicated signal design can be counter-productive. In the final section we discuss the question: if you could design a new GNSS signal set, what should the signals look like?

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C/No - Signal Strength Slide Rule: