750 AIRBORNE NAVIGATION AND GROUND SURVEILLANCE 



where |f |d = ratio of total doppler signal power to the noise power in the 

 bandwidth of the doppler spectrum, at the highest speed of 

 operation. (The bandwidth of the doppler spectrum is 

 measured at the 3-db points) 



Pave = average transmitted power per beam 



Go = one-way maximum antenna gain relative to an isotropic 

 radiator 



Wrf = RF attenuation in the plumbing of the transmitter and 

 receiver paths, including duplexing and waveguide losses 



E = efficiency factor, defined as the ratio of available doppler- 

 signal-to-noise ratio to the doppler-signal-to-noise ratio 

 which would be available if all the received signal were 

 converted to doppler information. It includes sideband 

 power loss in pulse and FM-CW systems, noise increase 

 caused by "foldover," and any noise gating improvement. 

 The foldover loss occurs because of the noise-bandwidth 

 contraction and resulting noise density increase at the 

 second detector output of CW or pulse systems not using 

 single sideband detection techniques. It amounts to —3 db, 

 as explained in Sec. 6-6. The noise gating improvement 

 occurs if the receiver crystals are gated off completely from 

 the receiver input during a portion of the transmitter time 

 (as is done in most modern pulse systems) and is therefore 

 proportional to the ratio of receiver-on-time to the pulse 

 repetition period, sometimes called Do. The definition of E 

 above applies to coherent non-Janus and coherent post- 

 tracker-mixed Janus systems only. See additional j factor 

 for incoherent and coherent pre-tracker-mixed Janus 

 systems 



f{^) = scattering coefficient at the given y^ angle, where ^ is the 

 angle between the beam and the normal to the surface of the 

 sea or terrain [/(^A) = \^'^ sec i^] 



X = wavelength of transmission 



NF = RF noise figure 



k = Boltzmann's constant (1.38 X 10~") 



T = absolute temperature (300° K = 27° C) 



A/d = bandwidth in which the noise is measured — the bandwidth 

 of the doppler spectrum at the 3-db points, at the maximum 



