Description:HG9550. Frequency agility. Radar Altimeter. Navair. GRA-2000. -. Tri-service radar altimeter. NavCom. Defense. Electronics. AN/APN-232. FMCW .. (a). (b). (c). Figure 9 (a) Contour plot of the PAF for a BPSK signal modulated with 13-bit Barker code. (b) Cut along the 0 Doppler and (c) 0 delay axis.