Circuit Sage Tools
RFSim99 is a free linear S-parameter based circuit simulator offering schematic capture, simulation, 1 port and 2 port S-parameter display and file support, tolerance analysis, stability circles, and much more.
Nathan Iyer's Cascade:
Calculate Gain, NF, IIP3, Sensitivity from individual data of receiver's blocks
Global Positioning Systems, Inertial Navigation, and Integration by M. Grewal:
from description: "...provides engineers, computer scientists, and others with a working familiarity with the theory and contemporary applications of Global Navigation Satellite Systems (GNSS), Inertial Navigational Systems (INS), and Kalman filters. Throughout, the focus is on solving real-world problems, with an emphasis on the effective use of state-of-the-art integration techniques for those systems, especially the application of Kalman filtering. To that end, the authors explore the various subtleties, common failures, and inherent limitations of the theory as it applies to real-world situations, and provide numerous detailed application examples and practice problems, including GNSS-aided INS, modeling of gyros and accelerometers, and SBAS and GBAS..."
Global Positioning System: Theory and Practice:
from an Amazon reviewer: "...This text provides a great introduction to the *theory* of GPS. It is rigorous on the mathematics so I wouldn't recommend it for someone who just needs a general understanding of how GPS operates or an understanding of the applications of GPS (e.g. software project managers or other personnel who aren't actually implementing sat or receiver software). For those who need to dive into the theory and algorithms with of GPS, you should have a firm understanding of trigonometry, linear algebra (matrix operations) and basic calculus before reading this text. As one reviewer pointed out, it does cover the application of GPS to surveying in depth..."
Understanding GPS: Principles and Applications by E. Kaplan, et al:
Good reviews on Amazon