Let [P.sub.t] represent the power of transmitter (GPS satellite), [G.sub.t] gain of transmitter, and a target cross section, [R.sub.1] shows range (distance) from GPS satellites to target, and [R.sub.2] is range from target to receiver; then the received power can be calculated as 
The simulation result of SNR versus range for reflected L1 and L5 GPS signals shown in Figure 5 was carried out for 0 to 1000 m range with target cross section of 10 [m.sup.2].
As shown in Figure 10, as we observe a target through turbulence, we may expect the decrease of the target cross section
. It was, however, shown and experimentally verified that the apparent target cross section
can increase as much as 2 or 3 times the free space cross section.
The total measured cross section ([Sigma]) is given by, (6) [Mathematical Expression Omitted] where [Sigma.sub.B] = the background cross section [Sigma.sub.T] = the target cross section
[Psi] = the angle between the background and target
Part I begins by presenting the basic radar equation, radar antennas and electronics, signal propagation, radar target cross sections
, noise effects, target detection, the radar ambiguity function, pulse compression, radar accuracy and monopulse operation.